1
|
Sujansky SJ, Hoteling GA, Bandar JS. A strategy for the controllable generation of organic superbases from benchtop-stable salts. Chem Sci 2024; 15:10018-10026. [PMID: 38966380 PMCID: PMC11220602 DOI: 10.1039/d4sc02524e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2024] [Accepted: 05/07/2024] [Indexed: 07/06/2024] Open
Abstract
Organic superbases are a distinct class of strong base that enable numerous modern reaction applications. Despite their great synthetic potential, widespread use and study of superbases are limited by their air sensitivity and difficult preparation. To address this, we report air-stable carboxylate salts of BTPP and P2-t-Bu phosphazene superbases that, when added to solution with an epoxide, spontaneously generate freebase. These systems function as effective precatalysts and stoichiometric prereagents for superbase-promoted addition, substitution and polymerization reactions. In addition to improving the synthesis, shelf stability, handling and recycling of phosphazenes, this approach enables precise regulation of the rate of base generation in situ. The activation strategy effectively mimics manual slow addition techniques, allowing for control over a reaction's rate or induction period and improvement of reactions that require strong base but are also sensitive to its presence, such as Pd-catalyzed coupling reactions.
Collapse
Affiliation(s)
- Stephen J Sujansky
- Department of Chemistry, Colorado State University Fort Collins Colorado 80523 USA
| | - Garrett A Hoteling
- Department of Chemistry, Colorado State University Fort Collins Colorado 80523 USA
| | - Jeffrey S Bandar
- Department of Chemistry, Colorado State University Fort Collins Colorado 80523 USA
| |
Collapse
|
2
|
Spivey JA, Collum DB. Potassium Hexamethyldisilazide (KHMDS): Solvent-Dependent Solution Structures. J Am Chem Soc 2024; 146:17827-17837. [PMID: 38901126 DOI: 10.1021/jacs.4c03418] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/22/2024]
Abstract
Solution structures of potassium hexamethyldisilazide [KHMDS] and labeled [15N]KHMDS were examined using a number of analytical methods including 29Si NMR spectroscopy and density functional theory computations. A combination of 15N-29Si couplings, 29Si chemical shifts, and the method of continuous variations reveals dimers, monomers, and ion pairs. Weakly coordinating monofunctional ligands such as toluene, N,N-dimethylethylamine, and Et3N afford exclusively dimers. 1,3-Dioxolane, THF, dimethoxyethane, hexamethylphosphoramide, and diglyme provide dimers at low ligand concentrations and monomers at high ligand concentrations. N,N,N',N'-Tetramethylethylenediamine and N,N,N',N'-tetramethylcyclohexanediamine provide exclusively dimers at all ligand concentrations at ambient temperatures and significant monomer at -80 °C. Studies of 12-crown-4 ran into technical problems. Equimolar 15-crown-5 forms a dimer, whereas excess 15-crown-5 affords a putative ion pair. Whereas equimolar 18-crown-6 also affords a dimer, an excess provides a monomer rather than a solvent-separated ion pair. [2.2.2]cryptand affords what is believed to be a contact-ion-paired cryptate. Solvation was probed using largely density functional theory (DFT) computations. Thermally corrected energies are consistent with lower aggregates and higher solvates at low temperatures, but the magnitudes of the computed temperature dependencies were substantially larger than the experimentally derived data.
Collapse
Affiliation(s)
- Jesse A Spivey
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, United States
| | - David B Collum
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, United States
| |
Collapse
|
3
|
Yang X, Zhang B, Ruan J, Duanmu K, Chen W. Palladium-Catalyzed Allylation of Endocyclic 1-Azaallyl Anions. J Org Chem 2024; 89:8896-8905. [PMID: 38856706 DOI: 10.1021/acs.joc.4c00743] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2024]
Abstract
Endocyclic 1-azaallyl anions engage allyl acetates in a palladium-catalyzed allylation followed by reduction to give unprotected 2-(hetero)aryl-3-allylpiperidines and 2-allyl-3-arylmorpholines, products not easily accessible by other means. The allyl group is then readily transformed into a variety of functional groups. Preliminary studies on the asymmetric variant of the reaction using an enantiomerically pure BI-DIME-type ligand provide the product with moderate enantioselectivity. Computational studies suggest that energy barriers of inner-sphere reductive elimination and outer-sphere nucleophilic substitution are almost the same, which makes both of them possible reaction pathways. In addition, the inner-sphere mechanism displays an enantiodiscriminating C-C bond forming step, while the outer-sphere mechanism is much less selective, which combined to give the asymmetric variant of the reaction moderate enantioselectivity.
Collapse
Affiliation(s)
- Xiaoyu Yang
- School of Chemical Science and Engineering, Institute for Advanced Studies, Tongji University, 1239 Siping Rd, Shanghai 200092, P. R. China
| | - Biao Zhang
- School of Chemical Science and Engineering, Institute for Advanced Studies, Tongji University, 1239 Siping Rd, Shanghai 200092, P. R. China
| | - Junhao Ruan
- School of Chemical Science and Engineering, Institute for Advanced Studies, Tongji University, 1239 Siping Rd, Shanghai 200092, P. R. China
| | - Kaining Duanmu
- School of Chemical Science and Engineering, Institute for Advanced Studies, Tongji University, 1239 Siping Rd, Shanghai 200092, P. R. China
| | - Weijie Chen
- School of Chemical Science and Engineering, Institute for Advanced Studies, Tongji University, 1239 Siping Rd, Shanghai 200092, P. R. China
| |
Collapse
|
4
|
Bodnar AK, Szewczyk SM, Sun Y, Chen Y, Huang AX, Newhouse TR. Comprehensive Mechanistic Analysis of Palladium- and Nickel-Catalyzed α,β-Dehydrogenation of Carbonyls via Organozinc Intermediates. J Org Chem 2024; 89:3123-3132. [PMID: 38377547 PMCID: PMC11000628 DOI: 10.1021/acs.joc.3c02572] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/22/2024]
Abstract
Introducing degrees of unsaturation into small molecules is a central transformation in organic synthesis. A strategically useful category of this reaction type is the conversion of alkanes into alkenes for substrates with an adjacent electron-withdrawing group. An efficient strategy for this conversion has been deprotonation to form a stabilized organozinc intermediate that can be subjected to α,β-dehydrogenation through palladium or nickel catalysis. This general reactivity blueprint presents a window to uncover and understand the reactivity of Pd- and Ni-enolates. Within this context, it was determined that β-hydride elimination is slow and proceeds via concerted syn-elimination. One interesting finding is that β-hydride elimination can be preferred to a greater extent than C-C bond formation for Ni, more so than with Pd, which defies the generally assumed trends that β-hydride elimination is more facile with Pd than Ni. The discussion of these findings is informed by KIE experiments, DFT calculations, stoichiometric reactions, and rate studies. Additionally, this report details an in-depth analysis of a methodological manifold for practical dehydrogenation and should enable its application to challenges in organic synthesis.
Collapse
Affiliation(s)
- Alexandra K Bodnar
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520-8107, United States
| | - Suzanne M Szewczyk
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520-8107, United States
| | - Yang Sun
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520-8107, United States
| | - Yifeng Chen
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520-8107, United States
| | - Anson X Huang
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520-8107, United States
| | - Timothy R Newhouse
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520-8107, United States
| |
Collapse
|
5
|
You Q, Collum DB. Carbon-Nitrogen Bond Formation Using Sodium Hexamethyldisilazide: Solvent-Dependent Reactivities and Mechanisms. J Am Chem Soc 2023; 145:23568-23584. [PMID: 37857357 DOI: 10.1021/jacs.3c07317] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2023]
Abstract
The solvent-dependent reactivity of sodium hexamethyldisilazide (NaHMDS) toward carbon-centered electrophiles reveals reactions that are poorly represented or unrepresented in the literature, including direct aminolysis of aromatic methyl esters to give carboxamides, nitriles, or amidines, depending on the choice of solvent. SNAr substitutions of aryl halides and opening of terminal epoxides are also examined. A combination of 1H and 29Si nuclear magnetic resonance (NMR) spectroscopic studies using [15N]NaHMDS, kinetic studies, and computational studies reveals the complex mechanistic basis of the preferences for simple aryl carboxamides in toluene and dimethylethylamine and arylnitriles or amidines in tetrahydrofuran (THF). A prevalence of dimer- and mixed dimer-based chemistry even starting from the observable NaHMDS monomer in THF solution is notable.
Collapse
Affiliation(s)
- Qiulin You
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, United States
| | - David B Collum
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, United States
| |
Collapse
|
6
|
Lui NM, Collum DB. Sodiated Oppolzer Enolates: Solution Structures, Mechanism of Alkylation, and Origin of Stereoselectivity. Org Chem Front 2023; 10:4750-4757. [PMID: 38144519 PMCID: PMC10746328 DOI: 10.1039/d3qo01021j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2023]
Abstract
NMR spectroscopic studies reveal camphorsultam-derived sodium enolates known as Oppolzer enolates reside as monomers in neat THF and THF/HMPA solutions and as dimers in toluene when solvated by N,N,N',N'-tetramethylethylenediamine (TMEDA) and N,N,N',N'',N''-pentamethyldiethylenediamine (PMDTA). Density functional theory (DFT) computations attest to the solvation numbers. Rate studies show analogy with previously studied lithiated Oppolzer enolates in which alkylation occurs through non-chelated solvent-separated ion pairs. The origins of the selectivity trace to transition structures in which the alkylating agent is guided to the exo face of the camphor owing to stereoelectronic preferences imparted by the sultam sulfonyl moiety. Marked secondary-shell solvation effects are gleaned from the rate studies.
Collapse
Affiliation(s)
- Nathan M Lui
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, United States
| | - David B Collum
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, United States
| |
Collapse
|
7
|
Jdanova S, Taylor MS. Mechanistic Study of the Copper(II)-Mediated Site-Selective O-Arylation of Glycosides with Arylboronic Acids. J Org Chem 2023; 88:3487-3498. [PMID: 36888595 DOI: 10.1021/acs.joc.2c02693] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/09/2023]
Abstract
Glycosides having multiple free OH groups have been shown to undergo site-selective O-arylations in the presence of arylboronic acids and copper(II) acetate. Herein, a mechanistic analysis of these Chan-Evans-Lam-type couplings is presented based on reaction kinetics, mass spectrometric analysis of reaction mixtures, and substituent effect studies. The results establish that the formation of a substrate-derived boronic ester accelerates the rate-determining transmetalation step. Intramolecular transfer of the aryl group from the boronic ester is ruled out in favor of a pathway in which the key pre-transmetalation assembly is generated from a boronic ester, a copper complex, and a second equivalent of arylboronic acid.
Collapse
Affiliation(s)
- Sofia Jdanova
- Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6 Canada
| | - Mark S Taylor
- Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6 Canada
| |
Collapse
|
8
|
Lui NM, MacMillan SN, Collum DB. Lithiated Oppolzer Enolates: Solution Structures, Mechanism of Alkylation, and Origin of Stereoselectivity. J Am Chem Soc 2022; 144:23379-23395. [PMID: 36534055 PMCID: PMC10071589 DOI: 10.1021/jacs.2c09341] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Camphorsultam-based lithium enolates referred to colloquially as Oppolzer enolates are examined spectroscopically, crystallographically, kinetically, and computationally to ascertain the mechanism of alkylation and the origin of the stereoselectivity. Solvent- and substrate-dependent structures include tetramers for alkyl-substituted enolates in toluene, unsymmetric dimers for aryl-substituted enolates in toluene, substrate-independent symmetric dimers in THF and THF/toluene mixtures, HMPA-bridged trisolvated dimers at low HMPA concentrations, and disolvated monomers for the aryl-substituted enolates at elevated HMPA concentrations. Extensive analyses of the stereochemistry of aggregation are included. Rate studies for reaction with allyl bromide implicate an HMPA-solvated ion pair with a +Li(HMPA)4 counterion. Dependencies on toluene and THF are attributed to exclusively secondary-shell (medium) effects. Aided by density functional theory (DFT) computations, a stereochemical model is presented in which neither chelates nor the lithium gegenion serves roles. The stereoselectivity stems from the chirality within the sultam ring and not the camphor skeletal core.
Collapse
Affiliation(s)
- Nathan M Lui
- Department of Chemistry and Chemical Biology Baker Laboratory, Cornell University Ithaca, New York 14853-1301, United States
| | - Samantha N MacMillan
- Department of Chemistry and Chemical Biology Baker Laboratory, Cornell University Ithaca, New York 14853-1301, United States
| | - David B Collum
- Department of Chemistry and Chemical Biology Baker Laboratory, Cornell University Ithaca, New York 14853-1301, United States
| |
Collapse
|
9
|
Ma Y, Lui NM, Keresztes I, Woltornist RA, Collum DB. Sodium Isopropyl(trimethylsilyl)amide: A Stable and Highly Soluble Lithium Diisopropylamide Mimic. J Org Chem 2022; 87:14223-14229. [PMID: 36282953 PMCID: PMC10042304 DOI: 10.1021/acs.joc.2c01745] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The preparation, structure, physical properties, and reactivities of sodium isopropyl(trimethylsilyl)amide (NaPTA) are described. The solubilities at room temperature range from n-heptane (0.55 M), n-hexane (0.60 M), toluene (0.65 M), MTBE (1.7 M), Et3N (3.2 M), and THF (>6.0 M). The half-life to destruction in neat THF is >1 year at 25 °C and 7 days at 70 °C, which compares favorably to 2.5 months and 1.5 days, respectively, for LDA in neat THF. This study focuses on NaPTA in THF. 29Si NMR spectroscopy shows exclusively a mixture of cis and trans stereoisomeric dimers in 0.10-12 M THF in hexane. Density functional theory (DFT) computations suggest that the pKb is intermediate between dimeric sodium diisopropylamide (NaDA) and dimeric sodium hexamethyldisilazide (NaHMDS). Metalations of arenes, epoxides, ketones, hydrazones, alkenes, and alkyl halides show higher reactivities than LDA (kNaPTA/LDA = 1-30). While the rates of arene metalation are high, the lower pKb of NaPTA limits the substrates. Metalation of pseudoephedrate-based carboxamides to form disodiated Myers enolates solves several challenging technical problems.
Collapse
Affiliation(s)
- Yun Ma
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, United States
| | - Nathan M Lui
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, United States
| | - Ivan Keresztes
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, United States
| | - Ryan A Woltornist
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, United States
| | - David B Collum
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, United States
| |
Collapse
|
10
|
Li J, Song X, Wu F, You H, Chen FE. Cu‐Catalyzed Asymmetric Allylic Alkylation of Racemic Cyclic Allyl Bromides with Organolithium Compounds. European J Org Chem 2022. [DOI: 10.1002/ejoc.202200860] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Jun Li
- Harbin Institute of Technology Shenzhen School of science CHINA
| | - Xiao Song
- Harbin Institute of Technology Shenzhen School of science CHINA
| | - Fusong Wu
- Harbin Institute of Technology Shenzhen School of science CHINA
| | - Hengzhi You
- Harbin Institute of Technology Shenzhen School of science Xili University Town, Building G, Room 608 518055 Shenzhen CHINA
| | - Fen-Er Chen
- Harbin Institute of Technology Shenzhen School of science CHINA
| |
Collapse
|
11
|
Woltornist RA, Collum DB. Ketone Enolization with Sodium Hexamethyldisilazide: Solvent- and Substrate-Dependent E- Z Selectivity and Affiliated Mechanisms. J Am Chem Soc 2021; 143:17452-17464. [PMID: 34643382 PMCID: PMC10042305 DOI: 10.1021/jacs.1c06529] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Ketone enolization by sodium hexamethyldisilazide (NaHMDS) shows a marked solvent and substrate dependence. Enolization of 2-methyl-3-pentanone reveals E-Z selectivities in Et3N/toluene (20:1), methyl-t-butyl ether (MTBE, 10:1), N,N,N',N″,N″-pentamethyldiethylenetriamine (PMDTA)/toluene (8:1), TMEDA/toluene (4:1), diglyme (1:1), DME (1:22), and tetrahydrofuran (THF) (1:90). Control experiments show slow or nonexistent stereochemical equilibration in all solvents except THF. Enolate trapping with Me3SiCl/Et3N requires warming to -40 °C whereas Me3SiOTf reacts within seconds. In situ enolate trapping at -78 °C using preformed NaHMDS/Me3SiCl mixtures is effective in Et3N/toluene yet fails in THF by forming (Me3Si)3N. Rate studies show enolization via mono- and disolvated dimers in Et3N/toluene, disolvated dimers in TMEDA, trisolvated monomers in THF/toluene, and free ions with PMDTA. Density functional theory computations explore the selectivities via the E- and Z-based transition structures. Failures of theory-experiment correlations of ionic fragments were considerable even when isodesmic comparisons could have canceled electron correlation errors. Swapping 2-methyl-3-pentanone with a close isostere, 2-methylcyclohexanone, causes a fundamental change in the mechanism to a trisolvated-monomer-based enolization in THF.
Collapse
Affiliation(s)
- Ryan A Woltornist
- Department of Chemistry and Chemical Biology Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, United States
| | - David B Collum
- Department of Chemistry and Chemical Biology Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, United States
| |
Collapse
|
12
|
Martínez RF, Cravotto G, Cintas P. Organic Sonochemistry: A Chemist's Timely Perspective on Mechanisms and Reactivity. J Org Chem 2021; 86:13833-13856. [PMID: 34156841 PMCID: PMC8562878 DOI: 10.1021/acs.joc.1c00805] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Indexed: 01/17/2023]
Abstract
Sonochemistry, the use of sound waves, usually within the ultrasonic range (>20 kHz), to boost or alter chemical properties and reactivity constitutes a long-standing and sustainable technique that has, however, received less attention than other activation protocols despite affordable setups. Even if unnecessary to underline the impact of ultrasound-based strategies in a broad range of chemical and biological applications, there is considerable misunderstanding and pitfalls regarding the interpretation of cavitational effects and the actual role played by the acoustic field. In this Perspective, with an eye on mechanisms in particular, we discuss the potentiality of sonochemistry in synthetic organic chemistry through selected examples of past and recent developments. Such examples illustrate specific controlling effects and working rules. Looking back at the past while looking forward to advancing the field, some essentials of sonochemical activation will be distilled.
Collapse
Affiliation(s)
- R. Fernando Martínez
- Department
of Organic and Inorganic Chemistry, Faculty of Sciences, and IACYS-Green
Chemistry and Sustainable Development Unit, University of Extremadura, 06006 Badajoz, Spain
| | - Giancarlo Cravotto
- Dipartimento
di Scienza e Tecnologia del Farmaco, Universita
degli Studi di Torino, via P. Giuria 9, Torino 10125, Italy
| | - Pedro Cintas
- Department
of Organic and Inorganic Chemistry, Faculty of Sciences, and IACYS-Green
Chemistry and Sustainable Development Unit, University of Extremadura, 06006 Badajoz, Spain
| |
Collapse
|
13
|
Ma Y, Woltornist RA, Algera RF, Collum DB. Reactions of Sodium Diisopropylamide: Liquid-Phase and Solid-Liquid Phase-Transfer Catalysis by N, N, N', N″, N″-Pentamethyldiethylenetriamine. J Am Chem Soc 2021; 143:13370-13381. [PMID: 34375095 PMCID: PMC10042303 DOI: 10.1021/jacs.1c06528] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Sodium diisopropylamide (NaDA) in N,N-dimethylethylamine (DMEA) and DMEA-hydrocarbon mixtures with added N,N,N',N″,N″-pentamethyldiethylenetriamine (PMDTA) reacts with alkyl halides, epoxides, hydrazones, arenes, alkenes, and allyl ethers. Comparisons of PMDTA with N,N,N',N'-tetramethylethylenediamine (TMEDA) accompanied by detailed rate and computational studies reveal the importance of the trifunctionality and κ2-κ3 hemilability. Rate studies show exclusively monomer-based reactions of 2-bromooctane, cyclooctene oxide, and dimethylresorcinol. Catalysis with 10 mol % PMDTA shows up to >30-fold accelerations (kcat > 300) with no evidence of inhibition over 10 turnovers. Solid-liquid phase-transfer catalysis (SLPTC) is explored as a means to optimize the catalysis as well as explore the merits of heterogeneous reaction conditions.
Collapse
Affiliation(s)
- Yun Ma
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853–1301
| | - Ryan A. Woltornist
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853–1301
| | - Russell F. Algera
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853–1301
| | - David B. Collum
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853–1301
| |
Collapse
|
14
|
Chen W, Seidel D. α-C-H/N-H Annulation of Alicyclic Amines via Transient Imines: Preparation of Polycyclic Lactams. Org Lett 2021; 23:3729-3734. [PMID: 33881883 PMCID: PMC8175037 DOI: 10.1021/acs.orglett.1c01125] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Polycyclic lactams are prepared in a single operation from o-toluamides and cyclic amines in a process that involves transient cyclic imines, species that are conveniently obtained in situ from the corresponding lithium amides and simple ketone oxidants. Imines thus generated, such as 1-pyrroline and 1-piperideine, engage lithiated o-toluamides in a facile annulation process. Undesired side reactions such as imine deprotonation and o-toluamide dimerization are suppressed through the judicious choice of reaction conditions.
Collapse
Affiliation(s)
- Weijie Chen
- Center for Heterocyclic Compounds, Department of Chemistry, University of Florida, Gainesville, Florida, 32611, United States
| | - Daniel Seidel
- Center for Heterocyclic Compounds, Department of Chemistry, University of Florida, Gainesville, Florida, 32611, United States
| |
Collapse
|
15
|
Gavelle S, Abid I, Biletskyi B, Henrion S, Hémon-Ribaud A, Lhoste J, Martel A, Dujardin G, Gaulon-Nourry C. TIPS-Diazoacetone Aldol Addition: Mechanistic Aspects and Contribution to the Synthesis. J Org Chem 2021; 86:4917-4931. [PMID: 33725439 DOI: 10.1021/acs.joc.0c02725] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Aldol addition of α-triisopropylsilyl-α-diazoacetone (TIPS-diazoacetone), promoted by excess lithium diisopropylamide (LDA), was developed and applied to the synthesis of original C-TIPS diazoaldols, C-TIPS diazoketols, and a related Mannich-type product. An unprecedented mechanistic pathway has been proposed, involving a lithiated triazene intermediate resulting from the nucleophilic addition of LDA on the diazo moiety, supported by experimental results and DFT calculations.
Collapse
Affiliation(s)
- Sigrid Gavelle
- Institut des Molécules et Matériaux du Mans, IMMM UMR 6283 CNRS - Le Mans Université, Avenue Olivier Messiaen, 72085 CEDEX 9 Le Mans, France
| | - Imen Abid
- Institut des Molécules et Matériaux du Mans, IMMM UMR 6283 CNRS - Le Mans Université, Avenue Olivier Messiaen, 72085 CEDEX 9 Le Mans, France
| | - Bohdan Biletskyi
- Institut des Molécules et Matériaux du Mans, IMMM UMR 6283 CNRS - Le Mans Université, Avenue Olivier Messiaen, 72085 CEDEX 9 Le Mans, France
| | - Sylvain Henrion
- Institut des Molécules et Matériaux du Mans, IMMM UMR 6283 CNRS - Le Mans Université, Avenue Olivier Messiaen, 72085 CEDEX 9 Le Mans, France
| | - Annie Hémon-Ribaud
- Institut des Molécules et Matériaux du Mans, IMMM UMR 6283 CNRS - Le Mans Université, Avenue Olivier Messiaen, 72085 CEDEX 9 Le Mans, France
| | - Jérôme Lhoste
- Institut des Molécules et Matériaux du Mans, IMMM UMR 6283 CNRS - Le Mans Université, Avenue Olivier Messiaen, 72085 CEDEX 9 Le Mans, France
| | - Arnaud Martel
- Institut des Molécules et Matériaux du Mans, IMMM UMR 6283 CNRS - Le Mans Université, Avenue Olivier Messiaen, 72085 CEDEX 9 Le Mans, France
| | - Gilles Dujardin
- Institut des Molécules et Matériaux du Mans, IMMM UMR 6283 CNRS - Le Mans Université, Avenue Olivier Messiaen, 72085 CEDEX 9 Le Mans, France
| | - Catherine Gaulon-Nourry
- Institut des Molécules et Matériaux du Mans, IMMM UMR 6283 CNRS - Le Mans Université, Avenue Olivier Messiaen, 72085 CEDEX 9 Le Mans, France
| |
Collapse
|
16
|
Puleo TR, Sujansky SJ, Wright SE, Bandar JS. Organic Superbases in Recent Synthetic Methodology Research. Chemistry 2021; 27:4216-4229. [DOI: 10.1002/chem.202003580] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Indexed: 12/23/2022]
Affiliation(s)
- Thomas R. Puleo
- Department of Chemistry Colorado State University Fort Collins Colorado 80523 USA
| | - Stephen J. Sujansky
- Department of Chemistry Colorado State University Fort Collins Colorado 80523 USA
| | - Shawn E. Wright
- Department of Chemistry Colorado State University Fort Collins Colorado 80523 USA
| | - Jeffrey S. Bandar
- Department of Chemistry Colorado State University Fort Collins Colorado 80523 USA
| |
Collapse
|
17
|
Pareek M, Sunoj RB. Mechanistic insights into rhodium-catalyzed enantioselective allylic alkylation for quaternary stereogenic centers. Chem Sci 2020; 12:2527-2539. [PMID: 34164021 PMCID: PMC8179253 DOI: 10.1039/d0sc04959j] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Installing quaternary stereogenic carbon is an arduous task of contemporary importance in the domain of asymmetric catalysis. To this end, an asymmetric allylic alkylation of α,α-disubstituted aldehydes by using allyl benzoate in the presence of Wilkinson's catalyst [Rh(Cl)(PPh3)3], (R)-BINOL–P(OMe) as the external ligand, and LiHMDS as the base has been reported to offer high enantioselectivity. The mechanistic details of this important reaction remain vague, which prompted us to undertake a detailed density functional theory (SMD(THF)/B3LYP-D3) investigation on the nature of the potential active catalyst, energetic features of the catalytic cycle, and the origin of high enantioselectivity. We note that a chloride displacement from the native Rh-phosphine [Rh(Cl)(PPh3)3] by BINOL–P(OMe) phosphite and an ensuing MeCl elimination can result in the in situ formation of a Rh-phosphonate [Rh(BINOL–P
Created by potrace 1.16, written by Peter Selinger 2001-2019
]]>
O)(PPh3)3]. A superior energetic span (δE) noted with such a Rh-phosphonate suggests that it is likely to serve as an active catalyst. The uptake of allyl benzoate by the active catalyst followed by the turnover determining C–O bond oxidative addition furnishes a Rh-π-allyl intermediate, which upon interception by (Z)-Li-enolate (derived from α,α-disubstituted aldehyde) in the enantiocontrolling C–C bond generates a quaternary stereogenic center. The addition of the re prochiral face of the (Z)-Li-enolate to the Rh-bound allyl moiety leading to the R enantiomer of the product is found to be 2.4 kcal mol−1 more preferred over the addition through its si face. The origin of the stereochemical preference for the re face addition is traced to improved noncovalent interactions (NCIs) and less distortion in the enantiocontrolling C–C bond formation transition state than that in the si face addition. Computed enantioselectivity (96%) is in very good agreement with the experimental value (92%), so is the overall activation barrier (δE of 17.1 kcal mol−1), which is in conformity with room temperature reaction conditions. The origin of high enantioselectivity in the formation of quaternary stereogenic carbon.![]()
Collapse
Affiliation(s)
- Monika Pareek
- Department of Chemistry, Indian Institute of Technology Bombay Powai Mumbai 400076 India
| | - Raghavan B Sunoj
- Department of Chemistry, Indian Institute of Technology Bombay Powai Mumbai 400076 India
| |
Collapse
|
18
|
Maskeri MA, Brueckner AC, Feoktistova T, O'Connor MJ, Walden DM, Cheong PHY, Scheidt KA. Mechanism and origins of selectivity in the enantioselective oxa-Pictet-Spengler reaction: a cooperative catalytic complex from a hydrogen bond donor and chiral phosphoric acid. Chem Sci 2020; 11:8736-8743. [PMID: 34123127 PMCID: PMC8163393 DOI: 10.1039/d0sc03250f] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Accepted: 07/21/2020] [Indexed: 11/29/2022] Open
Abstract
Enantioselective additions to oxocarbenium ions are high-value synthetic transformations but have proven challenging to achieve. In particular, the oxa-Pictet-Spengler reaction has only recently been rendered enantioselective. We report experimental and computational studies on the mechanism of this unusual transformation. Herein we reveal that this reaction is hypothesized to proceed through a self-assembled ternary hydrogen bonding complex involving the substrate, chiral phosphate ion, and a urea hydrogen-bond donor. The computed transition state reveals C2-symmetric grooves in the chiral phosphate that are occupied by the urea and substrate. Occupation of one of these grooves by the urea co-catalyst tunes the available reactive volume and enhances the stereoselectivity of the chiral phosphate catalyst.
Collapse
Affiliation(s)
- Mark A Maskeri
- Department of Chemistry, Center for Molecular Innovation and Drug Discovery, Northwestern University Evanston IL 60208 USA
| | | | | | - Matthew J O'Connor
- Department of Chemistry, Center for Molecular Innovation and Drug Discovery, Northwestern University Evanston IL 60208 USA
| | - Daniel M Walden
- Department of Chemistry, Oregon State University Corvallis OR 97331 USA
| | | | - Karl A Scheidt
- Department of Chemistry, Center for Molecular Innovation and Drug Discovery, Northwestern University Evanston IL 60208 USA
| |
Collapse
|
19
|
Woltornist RA, Ma Y, Algera RF, Zhou Y, Zhang Z, Collum DB. Structure, Reactivity, and Synthetic Applications of Sodium Diisopropylamide. SYNTHESIS-STUTTGART 2020; 52:1478-1497. [PMID: 34349297 PMCID: PMC8330442 DOI: 10.1055/s-0039-1690846] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The 60-year history of sodium diisopropylamide (NaDA) is described herein. We review various preparations, solvent-dependent stabilities, and solution structures. Synthetic applications of NaDA reported to date are framed by a mechanism-driven approach, emphasizing selectivities when appropriate. We conclude with examples beyond metalation in which NaDA plays a central role and a few thoughts on where future applications could be focused.
Collapse
Affiliation(s)
- Ryan A. Woltornist
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853–1301
| | - Yun Ma
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853–1301
| | - Russell F. Algera
- Pfizer Worldwide Research and Development, Eastern Point Road, Groton, Connecticut 06340, United States
| | - Yuhui Zhou
- Frontage Laboratories, Inc., 75 E Uwchlan Avenue, Suite 100, Exton, PA, 19341
| | - Zirong Zhang
- Department of Chemistry, University of Michigan, CHEM 3614 930 North University Ave, Ann Arbor, MI, 48109
| | - David B. Collum
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853–1301
| |
Collapse
|
20
|
Zhou Y, Keresztes I, MacMillan SN, Collum DB. Disodium Salts of Pseudoephedrine-Derived Myers Enolates: Stereoselectivity and Mechanism of Alkylation. J Am Chem Soc 2019; 141:16865-16876. [PMID: 31613094 DOI: 10.1021/jacs.9b08176] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Pseudoephedrine-derived dianionic Myers enolates were generated using sodium diisopropylamide (NaDA) in THF solution. The reactivities and selectivities of the disodium salts largely mirror those of the dilithium salts but without the requisite large excesses of inorganic salts (LiCl) or mandated dilute solutions. The disodium salts require careful control of temperature to preclude deleterious aggregate aging effects traced to changes in the aggregate structure and intervening O-alkylations. Structural studies and density functional theory (DFT) computations show a dominant highly symmetric polyhedron quite different from the lithium analogue. No enolate-NaDA mixed aggregates are observed with excess NaDA. Rate studies show an alkylation mechanism involving an intervening tetramer-monomer pre-equilibrium followed by rate-limiting alkylation of tetrasolvated monomers. DFT computations were conducted to explore the possible influences on stereochemistry. A crystal deriving from samples aged at ambient temperature contains six dianionic subunits and two monoanionic (alkoxide-only) subunits. A new preparation of concentrated solutions of NaDA in THF solution is described.
Collapse
Affiliation(s)
- Yuhui Zhou
- Department of Chemistry and Chemical Biology, Baker Laboratory , Cornell University , Ithaca , New York 14853-1301 , United States
| | - Ivan Keresztes
- Department of Chemistry and Chemical Biology, Baker Laboratory , Cornell University , Ithaca , New York 14853-1301 , United States
| | - Samantha N MacMillan
- Department of Chemistry and Chemical Biology, Baker Laboratory , Cornell University , Ithaca , New York 14853-1301 , United States
| | - David B Collum
- Department of Chemistry and Chemical Biology, Baker Laboratory , Cornell University , Ithaca , New York 14853-1301 , United States
| |
Collapse
|
21
|
Amemiya F, Noda H, Shibasaki M. Lewis Base Assisted Lithium Brønsted Base Catalysis: A New Entry for Catalytic Asymmetric Synthesis of β 2,2-Amino Acids. Chem Pharm Bull (Tokyo) 2019; 67:1046-1049. [PMID: 31341115 DOI: 10.1248/cpb.c19-00569] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A new catalytic system comprising chiral Ag complex and Li aryloxide/bisphosphine oxide is developed for the synthesis of β2,2-amino acids via direct asymmetric Mannich-type reaction of 4-subsituted isoxazolidin-5-ones. The Mannich adduct is a direct precursor of β-peptidic compounds otherwise difficult to obtain.
Collapse
|
22
|
Ma Y, Algera RF, Woltornist RA, Collum DB. Sodium Diisopropylamide-Mediated Dehydrohalogenations: Influence of Primary- and Secondary-Shell Solvation. J Org Chem 2019; 84:10860-10869. [PMID: 31436099 PMCID: PMC6737842 DOI: 10.1021/acs.joc.9b01428] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
![]()
Eliminations of alkyl
halides by sodium diisopropylamide (NaDA)
in tetrahydrofuran (THF)/hexane or THF/N,N-dimethylethylamine
(DMEA) solutions are facile
and complementary to analogous reactions of lithium diisopropylamide
in THF. Rate studies show a dominance of monomer-based metalations
and prevalent secondary-shell solvation effects overlaid on primary-shell
effects. 1-Halooctanes exclusively undergo elimination rather than
substitution. Rate and isotopic labeling studies on 1-bromooctane
reveal an E2-like elimination pathway via trisolvated NaDA monomer.
By contrast, 1-chlorooctane is eliminated via disolvated monomer through
a carbenoid mechanism. exo-2-Norbornyl chloride and
bromide are also eliminated via disolvated monomer; a syn E2 mechanism
is inferred for these substrates. The cis- and trans-4-tert-butylcyclohexyl bromides show
a preference for the elimination of the cis isomer (kcis/ax/ktrans/eq = 10). Rate
and isotopic labeling studies are consistent with a trans-diaxial
E2 elimination via trisolvated monomer for the cis isomer and a carbenoid
mechanism via disolvated monomer for the trans isomer. Vicinal haloethers
show substrate-dependent reactivities, affording alkynes and enol
ethers. trans-1-Bromo-2-methoxycyclohexane provides
enol ether 1-methoxycyclohexene, while trans-1-bromo-2-methoxycyclooctane
provides dimeric products consistent with fleeting cycloocta-1,2-diene
(cyclic allene), which was fully characterized as two conformers.
Collapse
Affiliation(s)
- Yun Ma
- Department of Chemistry and Chemical Biology, Baker Laboratory , Cornell University , Ithaca , New York 14853-1301 , United States
| | - Russell F Algera
- Department of Chemistry and Chemical Biology, Baker Laboratory , Cornell University , Ithaca , New York 14853-1301 , United States
| | - Ryan A Woltornist
- Department of Chemistry and Chemical Biology, Baker Laboratory , Cornell University , Ithaca , New York 14853-1301 , United States
| | - David B Collum
- Department of Chemistry and Chemical Biology, Baker Laboratory , Cornell University , Ithaca , New York 14853-1301 , United States
| |
Collapse
|
23
|
Vargová D, Némethová I, Plevová K, Šebesta R. Asymmetric Transition-Metal Catalysis in the Formation and Functionalization of Metal Enolates. ACS Catal 2019. [DOI: 10.1021/acscatal.8b04357] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Denisa Vargová
- Comenius University in Bratislava, Faculty of Natural Sciences, Department of Organic Chemistry, Mlynská dolina, Ilkovičova 6, 842 15 Bratislava, Slovak Republic
| | - Ivana Némethová
- Comenius University in Bratislava, Faculty of Natural Sciences, Department of Organic Chemistry, Mlynská dolina, Ilkovičova 6, 842 15 Bratislava, Slovak Republic
| | - Kristína Plevová
- Comenius University in Bratislava, Faculty of Natural Sciences, Department of Organic Chemistry, Mlynská dolina, Ilkovičova 6, 842 15 Bratislava, Slovak Republic
| | - Radovan Šebesta
- Comenius University in Bratislava, Faculty of Natural Sciences, Department of Organic Chemistry, Mlynská dolina, Ilkovičova 6, 842 15 Bratislava, Slovak Republic
| |
Collapse
|
24
|
Dunn AL, Leitch DC, Journet M, Martin M, Tabet EA, Curtis NR, Williams G, Goss C, Shaw T, O’Hare B, Wade C, Toczko MA, Liu P. Selective Continuous Flow Iodination Guided by Direct Spectroscopic Observation of Equilibrating Aryl Lithium Regioisomers. Organometallics 2019. [DOI: 10.1021/acs.organomet.8b00538] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Anna L. Dunn
- API Chemistry, GlaxoSmithKline, King of Prussia, Pennsylvania 19406, United States
| | - David C. Leitch
- API Chemistry, GlaxoSmithKline, King of Prussia, Pennsylvania 19406, United States
| | - Michel Journet
- API Chemistry, GlaxoSmithKline, King of Prussia, Pennsylvania 19406, United States
| | - Michael Martin
- Early Development Sciences, GlaxoSmithKline, Research Triangle Park, North Carolina 27709, United States
| | - Elie A. Tabet
- Early Development Sciences, GlaxoSmithKline, Research Triangle Park, North Carolina 27709, United States
| | | | | | - Charles Goss
- Process Analytical Technologies, GlaxoSmithKline, King of Prussia, Pennsylvania 19406, United States
| | - Tony Shaw
- API Chemistry, GlaxoSmithKline, King of Prussia, Pennsylvania 19406, United States
| | - Bernie O’Hare
- Global Spectroscopy, GlaxoSmithKline, King of Prussia, Pennsylvania 19406, United States
| | - Charles Wade
- API Chemistry, GlaxoSmithKline, Stevenage, U.K. SG1 2NY
| | - Matthew A. Toczko
- Early Development Sciences, GlaxoSmithKline, Research Triangle Park, North Carolina 27709, United States
| | - Peng Liu
- API Chemistry, GlaxoSmithKline, King of Prussia, Pennsylvania 19406, United States
| |
Collapse
|
25
|
Zhang Z, Collum DB. Structures and Reactivities of Sodiated Evans Enolates: Role of Solvation and Mixed Aggregation on the Stereochemistry and Mechanism of Alkylations. J Am Chem Soc 2019; 141:388-401. [PMID: 30462500 PMCID: PMC7185956 DOI: 10.1021/jacs.8b10364] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Oxazolidinone-based sodiated enolates (Evans enolates) were generated using sodium diisopropylamide (NaDA) or sodium hexamethyldisilazide (NaHMDS) in the presence of N,N,N',N'-tetramethylethylenediamine (TMEDA), ( R,R)- trans- N,N,N',N'-tetramethylcyclohexanediamine [( R,R)-TMCDA], or ( S,S)-TMCDA. 13C NMR spectroscopic analysis in conjunction with the method of continuous variations (MCV), x-ray crystallography, and density functional theory (DFT) computations revealed the enolates to be octahedral bis-diamine-chelated monomers. Rate and computational studies of an alkylation with allyl bromide implicate a bis-diamine-chelated-monomer-based transition structure. The sodiated Evans enolates form mixed dimers with NaHMDS, NaDA, or sodium 2,6-di- tert-butylphenolate, the reactivities of which are examined. Stereoselective quaternizations, aldol additions, and azaaldol additions are described.
Collapse
Affiliation(s)
- Zirong Zhang
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853–1301
| | - David B. Collum
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853–1301
| |
Collapse
|
26
|
Liu Y, Liu S, Li D, Zhang N, Peng L, Ao J, Song CE, Lan Y, Yan H. Kinetic Resolution of Allylic Alcohol with Chiral BINOL-Based Alkoxides: A Combination of Experimental and Theoretical Studies. J Am Chem Soc 2018; 141:1150-1159. [DOI: 10.1021/jacs.8b12796] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
| | | | | | | | | | | | - Choong Eui Song
- Department of Chemistry, Sungkyunkwan University, 2066, Seobu-ro,
Jangan-gu, Suwon, Gyeonggi 440-746, Korea
| | | | | |
Collapse
|
27
|
Zhang XY, Zheng L, Guan BT. Lithium Diisopropylamide Catalyzed Allylic C-H Bond Alkylation with Styrenes. Org Lett 2018; 20:7177-7181. [PMID: 30387607 DOI: 10.1021/acs.orglett.8b03108] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Allylic substitution reactions, a well-established approach for new bond construction, often need transition-metal catalysts and stoichiometric amounts of organometallic reagents, strong bases, or oxidants. Lithium diisopropylamide (LDA), a widely used and commercially available Brønsted base, is herein reported to catalyze the allylic C-H bond addition of 1,3-diarylpropenes to styrenes. Preliminary mechanism studies have provided a solid structure of the π-allyllithium intermediate and revealed the unique catalytic roles of LDA and its conjugate acid diisopropylamine.
Collapse
Affiliation(s)
- Xiang-Yu Zhang
- State Key Laboratory and Institute of Elemento-Organic Chemistry, College of Chemistry , Nankai University , Tianjin 300071 , China
| | - Lei Zheng
- State Key Laboratory and Institute of Elemento-Organic Chemistry, College of Chemistry , Nankai University , Tianjin 300071 , China
| | - Bing-Tao Guan
- State Key Laboratory and Institute of Elemento-Organic Chemistry, College of Chemistry , Nankai University , Tianjin 300071 , China.,Collaborative Innovation Center of Chemical Science and Engineering , Nankai University , Tianjin 300071 , China
| |
Collapse
|
28
|
Akimoto G, Otsuka M, Takita R, Uchiyama M, Hedidi M, Bentabed-Ababsa G, Lassagne F, Erb W, Mongin F. Deprotonative Metalation of Methoxy-Substituted Arenes Using Lithium 2,2,6,6-Tetramethylpiperidide: Experimental and Computational Study. J Org Chem 2018; 83:13498-13506. [PMID: 30345758 DOI: 10.1021/acs.joc.8b02397] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The reaction pathways of lithium 2,2,6,6-tetramethylpiperidide (LiTMP)-mediated deprotonative metalation of methoxy-substituted arenes were investigated. Importantly, it was experimentally observed that, whereas TMEDA has no effect on the course of the reactions, the presence of more than the stoichiometric amount of LiCl is deleterious, in particular without an in situ trap. These effects were corroborated by the DFT calculations. The reaction mechanisms, such as the structure of the active species in the deprotonation event, the reaction pathways by each postulated LiTMP complex, the stabilization effects by in situ trapping using zinc species, and some kinetic interpretation, are discussed herein.
Collapse
Affiliation(s)
- Gaku Akimoto
- Graduate School of Pharmaceutical Sciences , The University of Tokyo , 7-3-1 Hongo , Bunkyo-ku, Tokyo 113-0033 , Japan.,Advanced Elements Chemistry Research Team, RIKEN Center for Sustainable Resource Science, and Elements Chemistry Laboratory , RIKEN , 2-1 Hirosawa , Wako-shi, Saitama 351-0198 , Japan
| | - Mai Otsuka
- Graduate School of Pharmaceutical Sciences , The University of Tokyo , 7-3-1 Hongo , Bunkyo-ku, Tokyo 113-0033 , Japan.,Advanced Elements Chemistry Research Team, RIKEN Center for Sustainable Resource Science, and Elements Chemistry Laboratory , RIKEN , 2-1 Hirosawa , Wako-shi, Saitama 351-0198 , Japan
| | - Ryo Takita
- Graduate School of Pharmaceutical Sciences , The University of Tokyo , 7-3-1 Hongo , Bunkyo-ku, Tokyo 113-0033 , Japan.,Advanced Elements Chemistry Research Team, RIKEN Center for Sustainable Resource Science, and Elements Chemistry Laboratory , RIKEN , 2-1 Hirosawa , Wako-shi, Saitama 351-0198 , Japan
| | - Masanobu Uchiyama
- Graduate School of Pharmaceutical Sciences , The University of Tokyo , 7-3-1 Hongo , Bunkyo-ku, Tokyo 113-0033 , Japan.,Advanced Elements Chemistry Research Team, RIKEN Center for Sustainable Resource Science, and Elements Chemistry Laboratory , RIKEN , 2-1 Hirosawa , Wako-shi, Saitama 351-0198 , Japan
| | - Madani Hedidi
- Univ Rennes, CNRS , ISCR (Institut des Sciences Chimiques de Rennes) - UMR 6226, F-35000 Rennes , France.,Laboratoire de Synthèse Organique Appliquée, Faculté des Sciences Exactes et Appliquées , Université Oran 1 Ahmed Ben Bella , BP 1524 El M'Naouer, 31000 Oran , Algeria
| | - Ghenia Bentabed-Ababsa
- Laboratoire de Synthèse Organique Appliquée, Faculté des Sciences Exactes et Appliquées , Université Oran 1 Ahmed Ben Bella , BP 1524 El M'Naouer, 31000 Oran , Algeria
| | - Frédéric Lassagne
- Univ Rennes, CNRS , ISCR (Institut des Sciences Chimiques de Rennes) - UMR 6226, F-35000 Rennes , France
| | - William Erb
- Univ Rennes, CNRS , ISCR (Institut des Sciences Chimiques de Rennes) - UMR 6226, F-35000 Rennes , France
| | - Florence Mongin
- Univ Rennes, CNRS , ISCR (Institut des Sciences Chimiques de Rennes) - UMR 6226, F-35000 Rennes , France
| |
Collapse
|
29
|
Sasaki M, Shimabara R, Takegawa T, Kotomori Y, Otani Y, Ohwada T, Takeda K. Steric Course of Deprotonation/Substitution of Chelating/Dipole-Stabilizing-Group-Substituted α-Amino- and α-Oxynitriles. European J Org Chem 2018. [DOI: 10.1002/ejoc.201800484] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Michiko Sasaki
- Department of Synthetic Organic Chemistry; Institute of Biomedical & Health Science; Hiroshima University; 1-2-3 Kasumi 734-8553 Minami-Ku, Hiroshima Japan
| | - Rumiko Shimabara
- Department of Synthetic Organic Chemistry; Institute of Biomedical & Health Science; Hiroshima University; 1-2-3 Kasumi 734-8553 Minami-Ku, Hiroshima Japan
| | - Tomo Takegawa
- Department of Synthetic Organic Chemistry; Institute of Biomedical & Health Science; Hiroshima University; 1-2-3 Kasumi 734-8553 Minami-Ku, Hiroshima Japan
| | - Yuri Kotomori
- Department of Synthetic Organic Chemistry; Institute of Biomedical & Health Science; Hiroshima University; 1-2-3 Kasumi 734-8553 Minami-Ku, Hiroshima Japan
| | - Yuko Otani
- Graduate School of Pharmaceutical Sciences; The University of Tokyo; 7-3-1 Hongo 113-0033 Bunkyo-Ku, Tokyo Japan
| | - Tomohiko Ohwada
- Graduate School of Pharmaceutical Sciences; The University of Tokyo; 7-3-1 Hongo 113-0033 Bunkyo-Ku, Tokyo Japan
| | - Kei Takeda
- Department of Synthetic Organic Chemistry; Institute of Biomedical & Health Science; Hiroshima University; 1-2-3 Kasumi 734-8553 Minami-Ku, Hiroshima Japan
| |
Collapse
|
30
|
Ho TC, Congmon J, Zhou Z, Tius MA, Pratt LM. Synthesis and structures of α-lithiated vinyl ethers. Tetrahedron 2018. [DOI: 10.1016/j.tet.2018.07.019] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
31
|
Mack KA, Collum DB. Case for Lithium Tetramethylpiperidide-Mediated Ortholithiations: Reactivity and Mechanisms. J Am Chem Soc 2018; 140:4877-4883. [PMID: 29589920 PMCID: PMC6141241 DOI: 10.1021/jacs.8b00590] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Rate and mechanistic studies of ortholithiations by lithium 2,2,6,6-tetramethylpiperidide focus on four arenes: 1,4-bis(trifluoromethyl)benzene, 1,3-bis(trifluoromethyl)benzene, 1,3-dimethoxybenzene, and 4,4-dimethyl-2-phenyl-2-oxazoline. Metalations occur via substrate-dependent combinations of monosolvated monomer, disolvated monomer, and tetrasolvated dimer (triple ions). Density functional theory computational studies augment the experimental data. We discuss the challenges presented by shifting dimer-monomer proportions in determining the observable reaction orders and our mathematical treatment of such shifting in reactant structure.
Collapse
Affiliation(s)
- Kyle A Mack
- Department of Chemistry and Chemical Biology Baker Laboratory , Cornell University , Ithaca , New York 14853-1301 , United States
| | - David B Collum
- Department of Chemistry and Chemical Biology Baker Laboratory , Cornell University , Ithaca , New York 14853-1301 , United States
| |
Collapse
|
32
|
Jermaks J, Tallmadge EH, Keresztes I, Collum DB. Lithium Amino Alkoxide-Evans Enolate Mixed Aggregates: Aldol Addition with Matched and Mismatched Stereocontrol. J Am Chem Soc 2018; 140:3077-3090. [PMID: 29457718 PMCID: PMC6059615 DOI: 10.1021/jacs.7b13776] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Building on structural and mechanistic studies of lithiated enolates derived from acylated oxazolidinones (Evans enolates) and chiral lithiated amino alkoxides, we found that amino alkoxides amplify the enantioselectivity of aldol additions. The pairing of enantiomeric series affords matched and mismatched stereoselectivities. The structures of mixed tetramers showing 2:2 and 3:1 (alkoxide-rich) stoichiometries are determined spectroscopically. Rate and computational studies provide a viable mechanistic and stereochemical model based on the direct reaction of the 3:1 mixed tetramers, but they raise unanswered questions for the 2:2 mixed aggregates.
Collapse
Affiliation(s)
- Janis Jermaks
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301
| | - Evan H. Tallmadge
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301
| | - Ivan Keresztes
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301
| | - David B. Collum
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301
| |
Collapse
|
33
|
Berton M, Mello R, Williard PG, González-Núñez ME. Reactivity of Lithium β-Ketocarboxylates: The Role of Lithium Salts. J Am Chem Soc 2017; 139:17414-17420. [PMID: 29116811 DOI: 10.1021/jacs.7b08450] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Lithium β-ketocarboxylates 1(COOLi), prepared by the reaction of lithium enolates 2(Li+) with carbon dioxide, readily undergo decarboxylative disproportionation in THF solution unless in the presence of lithium salts, in which case they are indefinitely stable at room temperature in inert atmosphere. The availability of stable THF solutions of lithium β-ketocarboxylates 1(COOLi) in the absence of carbon dioxide allowed reactions to take place with nitrogen bases and alkyl halides 3 to give α-alkyl ketones 1(R) after acidic hydrolysis. The sequence thus represents the use of carbon dioxide as a removable directing group for the selective monoalkylation of lithium enolates 2(Li+). The roles of lithium salts in preventing the disproportionation of lithium β-ketocarboxylates 1(COOLi) and in determining the course of the reaction with bases and alkyl halides 3 are discussed.
Collapse
Affiliation(s)
- Mateo Berton
- Departamento de Química Orgánica, Universidad de Valencia , Avda. Vicente Andrés Estellés s.n., 46100 Burjassot, Valencia, Spain.,Department of Chemistry, Brown University , Providence, Rhode Island 02912, United States
| | - Rossella Mello
- Departamento de Química Orgánica, Universidad de Valencia , Avda. Vicente Andrés Estellés s.n., 46100 Burjassot, Valencia, Spain
| | - Paul G Williard
- Department of Chemistry, Brown University , Providence, Rhode Island 02912, United States
| | - María Elena González-Núñez
- Departamento de Química Orgánica, Universidad de Valencia , Avda. Vicente Andrés Estellés s.n., 46100 Burjassot, Valencia, Spain
| |
Collapse
|
34
|
Algera RF, Ma Y, Collum DB. Sodium Diisopropylamide in Tetrahydrofuran: Selectivities, Rates, and Mechanisms of Arene Metalations. J Am Chem Soc 2017; 139:15197-15204. [PMID: 28946744 DOI: 10.1021/jacs.7b08734] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Sodium diisopropylamide (NaDA)-mediated metalations of arenes in tetrahydrofuran (THF)/hexane or THF/Me2NEt solutions are described. A survey of >40 benzenoid- and pyridine-based arenes with a range of substituents demonstrates the efficacy and regioselectivity of metalation. Metalations of activated disubstituted arenes and selected monosubstituted arenes are rapid at -78 °C. Rate studies of 1,3-dimethoxybenzene and related methoxylated arenes show exclusively monomer-based orthometalations with two or three coordinated THF ligands. Rate studies of the isotopic exchange of benzene and monosubstituted arenes with weakly activating groups reveal analogous di- and trisolvated monomer-based metalations. Cooperative inductive, mesomeric, steric, and chelate effects are discussed.
Collapse
Affiliation(s)
- Russell F Algera
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University , Ithaca, New York 14853-1301, United States
| | - Yun Ma
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University , Ithaca, New York 14853-1301, United States
| | - David B Collum
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University , Ithaca, New York 14853-1301, United States
| |
Collapse
|
35
|
Keles H, Susanne F, Livingstone H, Hunter S, Wade C, Bourdon R, Rutter A. Development of a Robust and Reusable Microreactor Employing Laser Based Mid-IR Chemical Imaging for the Automated Quantification of Reaction Kinetics. Org Process Res Dev 2017. [DOI: 10.1021/acs.oprd.7b00245] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- Hakan Keles
- Research
and Development, GlaxoSmithKline, Gunnels Wood Road, Stevenage SG1 2NY, U.K
| | - Flavien Susanne
- Product
and Process Engineering, GlaxoSmithKline, Gunnels Wood Road, Stevenage SG1 2NY, U.K
| | - Hamish Livingstone
- Technical
Development, Glaxo Wellcome Manufacturing Pte Ltd 1, Pioneer Sector
1, Singapore, 628413, Singapore
| | - Sarah Hunter
- Product
and Process Engineering, GlaxoSmithKline, Gunnels Wood Road, Stevenage SG1 2NY, U.K
| | - Charles Wade
- Global
API Chemistry, GlaxoSmithKline, Gunnels Wood Road, Stevenage SG1 2NY, U.K
| | - Rose Bourdon
- Research
and Development, GlaxoSmithKline, Gunnels Wood Road, Stevenage SG1 2NY, U.K
| | - Andrew Rutter
- Product
and Process Engineering, GlaxoSmithKline, Gunnels Wood Road, Stevenage SG1 2NY, U.K
| |
Collapse
|
36
|
Mack KA, McClory A, Zhang H, Gosselin F, Collum DB. Lithium Hexamethyldisilazide-Mediated Enolization of Highly Substituted Aryl Ketones: Structural and Mechanistic Basis of the E/Z Selectivities. J Am Chem Soc 2017; 139:12182-12189. [PMID: 28786667 PMCID: PMC6122874 DOI: 10.1021/jacs.7b05057] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Enolizations of highly substituted acyclic ketones used in the syntheses of tetrasubstituted olefin-based anticancer agents are described. Lithium hexamethyldisilazide (LiHMDS)-mediated enolizations are moderately Z-selective in neat tetrahydrofuran (THF) and E-selective in 2.0 M THF/hexane. The results of NMR spectroscopy show the resulting enolates to be statistically distributed ensembles of E,E-, E,Z-, and Z,Z-enolate dimers with subunits that reflect the selectivities. The results of rate studies trace the preference for E and Z isomers to tetrasolvated- and pentasolvated-monomer-based transition structures, respectively. Enolization using LiHMDS in N,N-dimethylethylamine or triethylamine in toluene affords a 65:1 mixture of LiHMDS-lithium enolate mixed dimers containing E and Z isomers, respectively. Spectroscopic studies show that condition-dependent complexation of ketone to LiHMDS occurs in trialkylamine/toluene. Rate data attribute the high selectivity exclusively to monosolvated-dimer-based transition structures.
Collapse
Affiliation(s)
- Kyle A. Mack
- Baker Laboratory, Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, United States
| | - Andrew McClory
- Small Molecule Process Chemistry, Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Haiming* Zhang
- Small Molecule Process Chemistry, Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Francis Gosselin
- Small Molecule Process Chemistry, Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - David B. Collum
- Baker Laboratory, Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, United States
| |
Collapse
|
37
|
Algera RF, Ma Y, Collum DB. Sodium Diisopropylamide in Tetrahydrofuran: Selectivities, Rates, and Mechanisms of Alkene Isomerizations and Diene Metalations. J Am Chem Soc 2017; 139:11544-11549. [PMID: 28735535 PMCID: PMC6059566 DOI: 10.1021/jacs.7b05218] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Sodium diisopropylamide in tetrahydrofuran is an effective base for the metalation of 1,4-dienes and isomerization of alkenes. Dienes metalate via tetrasolvated sodium amide monomers, whereas 1-pentene is isomerized by trisolvated monomers. Facile, highly Z-selective isomerizations are observed for allyl ethers under conditions that compare favorably to those of existing protocols. The selectivity is independent of the substituents on the allyl ethers; rate and computational data show that the rates, mechanisms, and roles of sodium-oxygen contacts are substituent-dependent. The competing influences of substrate coordination and solvent coordination to sodium are discussed.
Collapse
Affiliation(s)
- Russell F Algera
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University , Ithaca, New York 14853-1301, United States
| | - Yun Ma
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University , Ithaca, New York 14853-1301, United States
| | - David B Collum
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University , Ithaca, New York 14853-1301, United States
| |
Collapse
|
38
|
Austin ND, Sahinidis NV, Konstantinov IA, Trahan DW. COSMO-based computer-aided molecular/mixture design: A focus on reaction solvents. AIChE J 2017. [DOI: 10.1002/aic.15871] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
|
39
|
Abstract
Solution characterizations and ligand binding constants were determined for n-butyllithium in hydrocarbon and ethereal solvents using diffusion-ordered NMR. In hydrocarbon solvents, n-butyllithium exists primarily as an octamer at -40 °C and deaggregates to a hexamer when the temperature is increased. In the presence of THF or diethyl ether, n-butyllithium exists predominantly as a tetra-solvated tetramer and deaggregates to a tetra-solvated dimer in the presence of a large excess or neat THF. The ligand binding constants for the tetra-solvated tetramers were measured using 1H NMR/DOSY titration.
Collapse
Affiliation(s)
- Onkei Tai
- Department of Chemistry, Brown University , Providence, Rhode Island 02912, United States
| | - Russell Hopson
- Department of Chemistry, Brown University , Providence, Rhode Island 02912, United States
| | - Paul G Williard
- Department of Chemistry, Brown University , Providence, Rhode Island 02912, United States
| |
Collapse
|
40
|
Ganiek MA, Becker MR, Berionni G, Zipse H, Knochel P. Barbier Continuous Flow Preparation and Reactions of Carbamoyllithiums for Nucleophilic Amidation. Chemistry 2017; 23:10280-10284. [PMID: 28590518 DOI: 10.1002/chem.201702593] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Indexed: 11/05/2022]
Abstract
An ambient temperature continuous flow method for nucleophilic amidation and thioamidation is described. Deprotonation of formamides by lithium diisopropylamine (LDA) affords carbamoyllithium intermediates that are quenched in situ with various electrophiles such as ketones, allyl bromides, Weinreb and morpholino amides. The nature of the reactive lithium intermediates and the thermodynamics of the metalation were further investigated by ab initio calculations and kinetic experiments.
Collapse
Affiliation(s)
- Maximilian A Ganiek
- Department Chemie, Ludwig-Maximilians-Universität München, Butenandtstrasse 5-13, Haus F, 81377, München, Germany
| | - Matthias R Becker
- Department Chemie, Ludwig-Maximilians-Universität München, Butenandtstrasse 5-13, Haus F, 81377, München, Germany
| | - Guillaume Berionni
- Department Chemie, Ludwig-Maximilians-Universität München, Butenandtstrasse 5-13, Haus F, 81377, München, Germany
| | - Hendrik Zipse
- Department Chemie, Ludwig-Maximilians-Universität München, Butenandtstrasse 5-13, Haus F, 81377, München, Germany
| | - Paul Knochel
- Department Chemie, Ludwig-Maximilians-Universität München, Butenandtstrasse 5-13, Haus F, 81377, München, Germany
| |
Collapse
|
41
|
Zhang Z, Collum DB. Evans Enolates: Structures and Mechanisms Underlying the Aldol Addition of Oxazolidinone-Derived Boron Enolates. J Org Chem 2017; 82:7595-7601. [PMID: 28686020 DOI: 10.1021/acs.joc.7b01365] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The soft enolization of an acylated oxazolidinone using di-n-butylboron triflate (n-Bu2BOTf) and trialkylamines and subsequent aldol addition was probed structurally and mechanistically using a combination of IR and NMR spectroscopies. None of the species along the reaction coordinate show a penchant for aggregating. Complexation of the acylated oxazolidinone by n-Bu2BOTf was too rapid to monitor, as was the subsequent enolization with Et3N (triethylamine). The preformed n-Bu2BOTf·Et3N complex, displaying muted Lewis acidity and affiliated tractable rates, reveals a rate-limiting complexation via a transition structure with a complicated counterion. n-Bu2BOTf·i-Bu3N bearing a hindered amine shifts the rate-limiting step to proton transfer. Rate studies show that the aldol addition with isobutyraldehyde occurs as proffered by others.
Collapse
Affiliation(s)
- Zirong Zhang
- Department of Chemistry and Chemical Biology Baker Laboratory, Cornell University , Ithaca, New York 14853-1301, United States
| | - David B Collum
- Department of Chemistry and Chemical Biology Baker Laboratory, Cornell University , Ithaca, New York 14853-1301, United States
| |
Collapse
|
42
|
Abstract
The solution structures, stabilities, physical properties, and reactivities of sodium diisopropylamide (NaDA) in a variety of coordinating solvents are described. NaDA is stable for months as a solid or as a 1.0 M solution in N,N-dimethylethylamine (DMEA) at -20 °C. A combination of NMR spectroscopic and computational studies show that NaDA is a disolvated symmetric dimer in DMEA, N,N-dimethyl-n-butylamine, and N-methylpyrrolidine. Tetrahydrofuran (THF) readily displaces DMEA, affording a tetrasolvated cyclic dimer at all THF concentrations. Dimethoxyethane (DME) and N,N,N',N'-tetramethylethylenediamine quantitatively displace DMEA, affording doubly chelated symmetric dimers. The trifunctional ligands N,N,N',N″,N″-pentamethyldiethylenetriamine and diglyme bind the dimer as bidentate rather than tridentate ligands. Relative rates of solvent decompositions are reported, and rate studies for the decomposition of THF and DME are consistent with monomer-based mechanisms.
Collapse
Affiliation(s)
- Russell F. Algera
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853–1301, United States,
| | - Yun Ma
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853–1301, United States,
| | - David B. Collum
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853–1301, United States,
| |
Collapse
|
43
|
Algera RF, Gupta L, Hoepker AC, Liang J, Ma Y, Singh KJ, Collum DB. Lithium Diisopropylamide: Nonequilibrium Kinetics and Lessons Learned about Rate Limitation. J Org Chem 2017; 82:4513-4532. [PMID: 28368117 PMCID: PMC6059656 DOI: 10.1021/acs.joc.6b03083] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The kinetics of lithium diisopropylamide (LDA) in tetrahydrofuran under nonequilibrium conditions are reviewed. These conditions correspond to a class of substrates in which the rates of LDA aggregation and solvation events are comparable to the rates at which various fleeting intermediates react with substrate. Substrates displaying these reactivities, by coincidence, happen to be those that react at tractable rates on laboratory time scales at -78 °C. In this strange region of nonlimiting behavior, rate-limiting steps are often poorly defined, sometimes involve deaggregation, and at other times include reaction with substrate. Changes in conditions routinely cause shifts in the rate-limiting steps, and autocatalysis is prevalent and can be acute. The studies are described in three distinct portions: (1) methods and strategies used to deconvolute complex reaction pathways, (2) the resulting conclusions about organolithium reaction mechanisms, and (3) perspectives on the concept of rate limitation reinforced by studies of LDA in tetrahydrofuran at -78 °C under nonequilibrium conditions.
Collapse
Affiliation(s)
- Russell F. Algera
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853–1301
| | - Lekha Gupta
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853–1301
| | - Alexander C. Hoepker
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853–1301
| | - Jun Liang
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853–1301
| | - Yun Ma
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853–1301
| | - Kanwal J. Singh
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853–1301
| | - David B. Collum
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853–1301
| |
Collapse
|
44
|
Border EC, Maguire M, MacLellan JG, Andrews PC. Metal-Induced C–N Bond Cleavage in the Decomposition of Alkali (R,R)-Bis(α-methylbenzyl)amide Complexes. Organometallics 2017. [DOI: 10.1021/acs.organomet.7b00074] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Emily C. Border
- School of Chemistry, Monash University, Clayton, Melbourne, Victoria 3800, Australia
| | - Melissa Maguire
- School of Chemistry, Monash University, Clayton, Melbourne, Victoria 3800, Australia
| | - Jonathan G. MacLellan
- School of Chemistry, Monash University, Clayton, Melbourne, Victoria 3800, Australia
| | - Philip C. Andrews
- School of Chemistry, Monash University, Clayton, Melbourne, Victoria 3800, Australia
| |
Collapse
|
45
|
Reyes-Rodríguez GJ, Algera RF, Collum DB. Lithium Hexamethyldisilazide-Mediated Enolization of Acylated Oxazolidinones: Solvent, Cosolvent, and Isotope Effects on Competing Monomer- and Dimer-Based Pathways. J Am Chem Soc 2017; 139:1233-1244. [PMID: 28080036 PMCID: PMC6059651 DOI: 10.1021/jacs.6b11354] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Lithium hexamethyldisilazide (LiHMDS)-mediated enolization of (+)-4-benzyl-3-propionyl-2-oxazolidinone in THF-hydrocarbon mixtures shows unusual sensitivity to the choice of hydrocarbon cosolvent (hexane versus toluene) and to isotopic labeling. Four mechanisms corresponding to monosolvated monomers, trisolvated dimers, octasolvated monomers, and octasolvated dimers were identified. Even under conditions in which the LiHMDS monomer was the dominant observable form, dimer-based metalation was significant. The mechanism-dependent isotope and cosolvent effects are discussed in the context of ground-state stabilization and transition-state tunneling.
Collapse
Affiliation(s)
- Gabriel J. Reyes-Rodríguez
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853–1301
| | - Russell F. Algera
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853–1301
| | - David B. Collum
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853–1301
| |
Collapse
|
46
|
Wang Y, Liu J, Huang L, Zhu R, Huang X, Moir R, Huang J. KOtBu-Catalyzed lithiation of PMDTA and the direct functionalization of bridged alkenes under mild conditions. Chem Commun (Camb) 2017; 53:4589-4592. [DOI: 10.1039/c7cc02006f] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A practical preparation of the reagent PMDTALi using a super base system under mild conditions has been developed.
Collapse
Affiliation(s)
- Yuntao Wang
- School of Pharmaceutical Science and Technology
- Tianjin University
- Tianjin 300072
- China
- Collaborative Innovation Center of Chemical Science and Engineering
| | - Jialin Liu
- School of Pharmaceutical Science and Technology
- Tianjin University
- Tianjin 300072
- China
- Collaborative Innovation Center of Chemical Science and Engineering
| | - Lin Huang
- School of Pharmaceutical Science and Technology
- Tianjin University
- Tianjin 300072
- China
- Collaborative Innovation Center of Chemical Science and Engineering
| | - Ranran Zhu
- School of Pharmaceutical Science and Technology
- Tianjin University
- Tianjin 300072
- China
- Collaborative Innovation Center of Chemical Science and Engineering
| | - Xueyan Huang
- School of Pharmaceutical Science and Technology
- Tianjin University
- Tianjin 300072
- China
- Collaborative Innovation Center of Chemical Science and Engineering
| | - Ross Moir
- School of Chemistry
- University of Edinburgh
- UK
| | - Jianhui Huang
- School of Pharmaceutical Science and Technology
- Tianjin University
- Tianjin 300072
- China
- Collaborative Innovation Center of Chemical Science and Engineering
| |
Collapse
|
47
|
Guang J, Liu Q, Hopson R, Kagan G, Li W, Monroe TB, Williard PG. Conformational Polymorphism of Lithium Pinacolone Enolate. J Am Chem Soc 2016; 138:15177-15188. [PMID: 27762552 DOI: 10.1021/jacs.6b08177] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A metastable, polymorphic hexameric crystal structure of lithium pinacolone enolate (LiOPin) is reported along with three preparation methods. NMR-based structural characterization implies that the lithium pinacolate hexamer deaggregates to a tetramer in toluene but retains mainly the hexameric structure in nonaromatic hydrocarbon solvents such as cyclohexane. Moreover, the presence of a small amount of lithium aldolate (LiOA) dramatically influences the aggregation state of LiOPin by forming a mixed aggregate with a 3:1 ratio (LiOPin3·LiOA).
Collapse
Affiliation(s)
- Jie Guang
- Department of Chemistry, Brown University , Providence, Rhode Island 02912, United States
| | - Qiyong Liu
- Department of Chemistry, Brown University , Providence, Rhode Island 02912, United States
| | - Russell Hopson
- Department of Chemistry, Brown University , Providence, Rhode Island 02912, United States
| | - Gerald Kagan
- Department of Chemistry, Brown University , Providence, Rhode Island 02912, United States
| | - Weibin Li
- Department of Chemistry, Brown University , Providence, Rhode Island 02912, United States
| | - Thomas B Monroe
- Department of Chemistry, Brown University , Providence, Rhode Island 02912, United States
| | - Paul G Williard
- Department of Chemistry, Brown University , Providence, Rhode Island 02912, United States
| |
Collapse
|
48
|
Fernández-Nieto F, Paleo MR, Colunga R, Raposo ML, Garcia-Rio L, Sardina FJ. The Two Alternative Rate-Determining Steps in Benzylic Lithiation Reactions of Esters and Carbamates. Org Lett 2016; 18:5520-5523. [PMID: 27768316 DOI: 10.1021/acs.orglett.6b02753] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Lithiation reactions of tertiary benzylic esters and carbamates have been studied. Kinetic methodology revealed that a two-step reaction pathway should be considered for these reactions, where either the lithium precomplexation and/or the proton transfer steps can be rate determining. Kinetic isotopic effects were evaluated by comparison of the lithiations of the corresponding protio/deutero substrates, and the results obtained support the notion that lithium precomplexation is taking place on the reaction pathway and that it is the rate-determining step in this transformation.
Collapse
Affiliation(s)
- Fernando Fernández-Nieto
- Departamento de Química Orgánica and Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CIQUS), Universidade de Santiago de Compostela , 15782 Santiago de Compostela, Spain
| | - M Rita Paleo
- Departamento de Química Orgánica and Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CIQUS), Universidade de Santiago de Compostela , 15782 Santiago de Compostela, Spain
| | - Roberto Colunga
- Departamento de Química Orgánica and Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CIQUS), Universidade de Santiago de Compostela , 15782 Santiago de Compostela, Spain
| | - M Luz Raposo
- Departamento de Química Física and Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CIQUS), Universidade de Santiago de Compostela , 15782 Santiago de Compostela, Spain
| | - Luis Garcia-Rio
- Departamento de Química Física and Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CIQUS), Universidade de Santiago de Compostela , 15782 Santiago de Compostela, Spain
| | - F Javier Sardina
- Departamento de Química Orgánica and Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CIQUS), Universidade de Santiago de Compostela , 15782 Santiago de Compostela, Spain
| |
Collapse
|
49
|
MacLeod KC, Menges FS, McWilliams SF, Craig SM, Mercado BQ, Johnson MA, Holland PL. Alkali-Controlled C-H Cleavage or N-C Bond Formation by N2-Derived Iron Nitrides and Imides. J Am Chem Soc 2016; 138:11185-91. [PMID: 27571271 PMCID: PMC5266523 DOI: 10.1021/jacs.6b04984] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Formation of N-H and N-C bonds from functionalization of N2 is a potential route to utilization of this abundant resource. One of the key challenges is to make the products of N2 activation reactive enough to undergo further reactions under mild conditions. This paper explores the strategy of "alkali control," where the presence of an alkali metal cation enables the reduction of N2 under mild conditions, and then chelation of the alkali metal cation uncovers a highly reactive species that can break benzylic C-H bonds to give new N-H and Fe-C bonds. The ability to "turn on" this C-H activation pathway with 18-crown-6 is demonstrated with three different N2 reduction products of N2 cleavage in an iron-potassium system. The alkali control strategy can also turn on an intermolecular reaction of an N2-derived nitride with methyl tosylate that gives a new N-C bond. Since the transient K(+)-free intermediate reacts with this electrophile but not with the weak C-H bonds in 1,4-cyclohexadiene, it is proposed that the C-H cleavage occurs by a deprotonation mechanism. The combined results demonstrate that a K(+) ion can mask the latent nucleophilicity of N2-derived nitride and imide ligands within a trimetallic iron system and points a way toward control over N2 functionalization.
Collapse
Affiliation(s)
- K. Cory MacLeod
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States
| | - Fabian S. Menges
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States
| | - Sean F. McWilliams
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States
| | - Stephanie M. Craig
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States
| | - Brandon Q. Mercado
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States
| | - Mark A. Johnson
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States
| | - Patrick L. Holland
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States
| |
Collapse
|
50
|
Poad BLJ, Reed ND, Hansen CS, Trevitt AJ, Blanksby SJ, Mackay EG, Sherburn MS, Chan B, Radom L. Preparation of an ion with the highest calculated proton affinity: ortho-diethynylbenzene dianion. Chem Sci 2016; 7:6245-6250. [PMID: 30034765 PMCID: PMC6024202 DOI: 10.1039/c6sc01726f] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Accepted: 06/17/2016] [Indexed: 11/23/2022] Open
Abstract
Owing to the increased proton affinity that results from additional negative charges, multiply-charged anions are shown as a route to preparing powerful ‘superbases’.
Owing to the increased proton affinity that results from additional negative charges, multiply-charged anions have been proposed as one route to prepare and access a range of new and powerful “superbases”. Paradoxically, while the additional electrons in polyanions increase basicity they serve to diminish the electron binding energy and thus, it had been thought, hinder experimental synthesis. We report the synthesis and isolation of the ortho-diethynylbenzene dianion (ortho-DEB2–) and present observations of this novel species undergoing gas-phase proton-abstraction reactions. Using a theoretical model based on Marcus–Hush theory, we attribute the stability of ortho-DEB2– to the presence of a barrier that prevents spontaneous electron detachment. The proton affinity of 1843 kJ mol–1 calculated for this dianion superbase using high-level quantum chemistry calculations significantly exceeds that of the lithium monoxide anion, the most basic system previously prepared. The ortho-diethynylbenzene dianion is therefore the strongest base that has been experimentally observed to date.
Collapse
Affiliation(s)
- Berwyck L J Poad
- Central Analytical Research Facility , Institute for Future Environments , Queensland University of Technology , Brisbane , QLD 4001 , Australia . .,School of Chemistry , University of Wollongong , Gwynneville , NSW 2522 , Australia
| | - Nicholas D Reed
- School of Chemistry , University of Wollongong , Gwynneville , NSW 2522 , Australia
| | - Christopher S Hansen
- School of Chemistry , University of Wollongong , Gwynneville , NSW 2522 , Australia
| | - Adam J Trevitt
- School of Chemistry , University of Wollongong , Gwynneville , NSW 2522 , Australia
| | - Stephen J Blanksby
- Central Analytical Research Facility , Institute for Future Environments , Queensland University of Technology , Brisbane , QLD 4001 , Australia .
| | - Emily G Mackay
- Research School of Chemistry , Australian National University , Canberra , ACT 2601 , Australia
| | - Michael S Sherburn
- Research School of Chemistry , Australian National University , Canberra , ACT 2601 , Australia
| | - Bun Chan
- School of Chemistry , University of Sydney , Sydney , NSW 2006 , Australia
| | - Leo Radom
- School of Chemistry , University of Sydney , Sydney , NSW 2006 , Australia
| |
Collapse
|