1
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Spivey JA, Collum DB. Potassium Hexamethyldisilazide (KHMDS): Solvent-Dependent Solution Structures. J Am Chem Soc 2024; 146:17827-17837. [PMID: 38901126 PMCID: PMC11373885 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.
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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
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2
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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.
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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
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3
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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.
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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
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4
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Sachan SK, Anantharaman G. Mixed-Valent Stellated Cuboctahedral Cu(2,4-Imdb)-MOF for Trace Water Detection. Inorg Chem 2022; 61:18340-18345. [DOI: 10.1021/acs.inorgchem.2c02791] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Sharad Kumar Sachan
- Indian Institute of Technology Kanpur (IITK), Kanpur, Uttar Pradesh 208016, India
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5
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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] [MESH Headings] [Grants] [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.
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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
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6
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Cave EA, Olson JZ, Schlenker CW. Ion-Pairing Dynamics Revealed by Kinetically Resolved In Situ FTIR Spectroelectrochemistry during Lithium-Ion Storage. ACS APPLIED MATERIALS & INTERFACES 2021; 13:48546-48554. [PMID: 34623808 DOI: 10.1021/acsami.1c11964] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Understanding the kinetics of interfacial ion speciation could inform battery designs. However, this knowledge gap persists, largely due to the challenge of experimentally interrogating the evolution of ions near electrode interfaces in a sea of bulk signals. We report here the very first kinetically resolved correlation between interfacial ion speciation and lithium-ion storage in a model system, by applying global target analysis to in situ attenuated total reflectance (ATR) Fourier-Transform infrared (FTIR) spectroelectrochemical data. Our results suggest that it may be more kinetically viable for lithium to be extracted from contact ion pairs (CIPs) to contribute to faster electrode charging compared to fully solvated lithium. As the search for fast-charging lithium-ion batteries and supercapacitors wages on, this discovery suggests that manipulating the ion pairing within the electrolyte could be one effective strategy for promoting faster-charging kinetics.
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Affiliation(s)
- Emma A Cave
- Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, United States
| | - Jarred Z Olson
- National Physical Laboratory, Teddington, Middlesex TW11 0LW, U.K
| | - Cody W Schlenker
- Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, United States
- Molecular Engineering & Sciences Institute, University of Washington, Seattle, Washington 98195, United States
- Clean Energy Institute, University of Washington, Seattle, Washington 98195-1653, United States
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7
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Woltornist RA, Collum DB. Aggregation and Solvation of Sodium Hexamethyldisilazide: Across the Solvent Spectrum. J Org Chem 2021; 86:2406-2422. [PMID: 33471993 PMCID: PMC8011853 DOI: 10.1021/acs.joc.0c02546] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We report solution structures of sodium hexamethyldisilazide (NaHMDS) solvated by >30 standard solvents (ligands). These include: toluene, benzene, and styrene; triethylamine and related trialkylamines; pyrrolidine as a representative dialkylamine; dialkylethers including THF, tert-butylmethyl ether, and diethyl ether; dipolar ligands such as DMF, HMPA, DMSO, and DMPU; a bifunctional dipolar ligand nonamethylimidodiphosphoramide (NIPA); polyamines N,N,N',N'-tetramethylenediamine (TMEDA), N,N,N',N″,N″-pentamethyldiethylenetriamine (PMDTA), N,N,N',N'-tetramethylcyclohexanediamine (TMCDA), and 2,2'-bipyridine; polyethers 12-crown-4, 15-crown-5, 18-crown-6, and diglyme; 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane ([2.2.2] cryptand); and tris[2-(2-methoxyethoxy)ethyl]amine (TDA-1). Combinations of 1H, 13C, 15N, and 29Si NMR spectroscopies, the method of continuous variations, X-ray crystallography, and density functional theory (DFT) computations reveal ligand-modulated aggregation to give mixtures of dimers, monomers, triple ions, and ion pairs. 15N-29Si coupling constants distinguish dimers and monomers. Solvation numbers are determined by a combination of solvent titrations, observed free and bound solvent in the slow exchange limit, and DFT computations. The relative abilities of solvents to compete in binary mixtures often match that predicted by conventional wisdom but with some exceptions and evidence of both competitive and cooperative (mixed) solvation. Crystal structures of a NaHMDS cryptate ion pair and a 15-crown-5-solvated monomer are included. Results are compared with those for lithium hexamethyldisilazide, lithium diisopropylamide, and sodium diisopropylamide.
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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
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8
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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
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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.![]()
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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
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9
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Ye W, Ni C, Hu J. Stereoselective nucleophilic monofluoromethylation of tert-butanesulfinimines: Dynamic thermodynamic Resolution of racemic α-fluoro carbanions. J Fluor Chem 2020. [DOI: 10.1016/j.jfluchem.2020.109451] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
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10
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Devaine-Pressing K, Oldenburg FJ, Menzel JP, Springer M, Dawe LN, Kozak CM. Lithium, sodium, potassium and calcium amine-bis(phenolate) complexes in the ring-opening polymerization of rac-lactide. Dalton Trans 2020; 49:1531-1544. [PMID: 31930245 DOI: 10.1039/c9dt04561a] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Compounds of Li, Na, K and Ca of a tetradentate amino-bis(phenolato) ligand were prepared. Bimetallic compounds formulated as M2[L](THF)n (where M = Na, n = 1 (1·THF) or Li, n = 1 (2·THF)) were synthesized via the reaction of H2[L] (where [L] = 2-pyridylmethylamino-N,N-bis(2-methylene-4-methoxy-6-tert-butylphenolato) with sodium hydride or n-butyllithium, respectively, in THF. Monometallic complexes MH[L](THF)n (where M = Na, n = 1 (3·THF), Li, n = 0 (4) and K, n = 0 (5)) were obtained by reaction of H2[L] with MN(SiMe3)2 where M = Na, Li, or K. Calcium complex Ca[L](THF) (6·THF) was synthesized in two ways; reaction of Na2[L] with calcium iodide in THF, and reaction of Ca[N(SiMe3)2]2 with H2[L] in toluene. Compounds 1-6 exhibit activity for rac-lactide polymerization under melt and solution conditions. Moderate control of polymer molecular weights was achieved in toluene, whereas polydisperse polymer was obtained under solvent free conditions. MALDI-TOF MS analysis of the polymer end groups revealed a predominantly cyclic nature for the polylactides.
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Affiliation(s)
- Katalin Devaine-Pressing
- Department of Chemistry, Memorial University of Newfoundland, St John's, Newfoundland, A1B 3X7, Canada.
| | - Fabio J Oldenburg
- Department of Chemistry, Memorial University of Newfoundland, St John's, Newfoundland, A1B 3X7, Canada.
| | - Jan P Menzel
- Department of Chemistry, Memorial University of Newfoundland, St John's, Newfoundland, A1B 3X7, Canada.
| | - Maximilian Springer
- Department of Chemistry, Memorial University of Newfoundland, St John's, Newfoundland, A1B 3X7, Canada.
| | - Louise N Dawe
- Department of Chemistry and Biochemistry, Wilfrid Laurier University, Waterloo, Ontario N2L 3C5, Canada
| | - Christopher M Kozak
- Department of Chemistry, Memorial University of Newfoundland, St John's, Newfoundland, A1B 3X7, Canada.
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11
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Paioti PHS, del Pozo J, Mikus MS, Lee J, Koh MJ, Romiti F, Torker S, Hoveyda AH. Catalytic Enantioselective Boryl and Silyl Substitution with Trifluoromethyl Alkenes: Scope, Utility, and Mechanistic Nuances of Cu–F β-Elimination. J Am Chem Soc 2019; 141:19917-19934. [DOI: 10.1021/jacs.9b11382] [Citation(s) in RCA: 67] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Paulo H. S. Paioti
- Supramolecular Science and Engineering Institute, University of Strasbourg, CNRS, 67000 Strasbourg, France
| | - Juan del Pozo
- Department of Chemistry, Merkert Chemistry Center, Boston College, Chestnut Hill, Massachusetts 02467, United States
| | - Malte S. Mikus
- Department of Chemistry, Merkert Chemistry Center, Boston College, Chestnut Hill, Massachusetts 02467, United States
| | - Jaehee Lee
- Department of Chemistry, Merkert Chemistry Center, Boston College, Chestnut Hill, Massachusetts 02467, United States
| | - Ming Joo Koh
- Department of Chemistry, Merkert Chemistry Center, Boston College, Chestnut Hill, Massachusetts 02467, United States
| | - Filippo Romiti
- Supramolecular Science and Engineering Institute, University of Strasbourg, CNRS, 67000 Strasbourg, France
| | - Sebastian Torker
- Supramolecular Science and Engineering Institute, University of Strasbourg, CNRS, 67000 Strasbourg, France
| | - Amir H. Hoveyda
- Supramolecular Science and Engineering Institute, University of Strasbourg, CNRS, 67000 Strasbourg, France
- Department of Chemistry, Merkert Chemistry Center, Boston College, Chestnut Hill, Massachusetts 02467, United States
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12
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Ciechańska M, Jóźwiak A, Nazarski RB, Skorupska EA. Unexpected Rearrangement of Dilithiated Isoindoline-1,3-diols into 3-Aminoindan-1-ones via N-Lithioaminoarylcarbenes: A Combined Synthetic and Computational Study. J Org Chem 2019; 84:11425-11440. [PMID: 31449415 DOI: 10.1021/acs.joc.9b01217] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The reaction of 2-aryl-3-hydroxyisoindolin-1-ones with the s-BuLi·TMEDA system in THF at -78 °C, affording a series of diastereomeric 3-aminoindan-1-ones via a novel rearrangement of the isoindolinone scaffold, is reported. It is proposed that α-elimination of LiOH from the transient N,O-dilithiated hemiaminal carbenoids leads to the formation of singlet carbenes followed by their trapping via an intramolecular C-H insertion. An alternative explanation based on an intramolecular Mannich reaction seem much less probable. A mechanistic-type study that combines spectroscopic data of the products and calculation results, with a special focus on the diverse lithiated intermediates that are most likely to engage in the title process (particularly those with internal Li bonds), is presented. The MP2 approach, including the NPA and QTAIM data, provided insight into structures and properties of all these species. Two reaction routes A and B appeared to be possible for the postulated carbene mechanism. An unusual metamorphosis of the CCN atom triad, from a near sp 1-azaallene-type in more stable noncarbene Li enolates to a roughly sp2 type in their carbene keto tautomers, is recognized in one of these pathways (route B). Dominant forms of resonance structures for the aforementioned tautomeric systems that have seven-membered quasi rings stabilized by Li+ ions bridging the N and carbonyl O atoms are indicated. Large computational difficulties arising from a huge impact of internal Li+ complexation on conformational preferences and electronic properties of carbonyl group-bearing lithium derivatives are also discussed. The new γ-keto carbene species under study belong to a subclass of acyclic aminoarylcarbenes.
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Affiliation(s)
- Magdalena Ciechańska
- Department of Organic Chemistry, Faculty of Chemistry , University of Lodz , Tamka 12 , 91-403 Łódź , Poland
| | - Andrzej Jóźwiak
- Department of Organic Chemistry, Faculty of Chemistry , University of Lodz , Tamka 12 , 91-403 Łódź , Poland
| | - Ryszard B Nazarski
- Theoretical and Structural Chemistry Group, Department of Physical Chemistry, Faculty of Chemistry , University of Lodz , Pomorska 163/165 , 90-236 Łódź , Poland
| | - Ewa A Skorupska
- Department of Organic Chemistry, Faculty of Chemistry , University of Lodz , Tamka 12 , 91-403 Łódź , Poland
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13
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Zhou Y, Jermaks J, Keresztes I, MacMillan SN, Collum DB. Pseudophedrine-Derived Myers Enolates: Structures and Influence of Lithium Chloride on Reactivity and Mechanism. J Am Chem Soc 2019; 141:5444-5460. [PMID: 30896939 PMCID: PMC7079698 DOI: 10.1021/jacs.9b00328] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The structures and reactivities of pseudoephedrine-derived dianionic Myers enolates are examined. A combination of NMR and IR spectroscopic, crystallographic, and computational data reveal that the homoaggregated dianions form octalithiated tetramers displaying S4-symmetric Li8O8 cores and overall C2 symmetry. Computational and isotopic labeling studies reveal strong N-Li contacts in the carboxamide enolate moiety. The method of continuous variations proves deceptive, as octalithiated tetrameric homoaggregates afford hexalithiated trimeric heteroaggregates. A lithium diisopropylamide-lithium enolate mixed aggregate is found to be a C2-symmetric hexalithiated species incorporating two enolate dianions and two lithium diisopropylamide (LDA) subunits. Structural and rate studies show that lithium chloride has little effect on the dynamics of the enolate homoaggregates but forms adducts of unknown structure. Rate studies of alkylations indicate that the aging of the aggregates can have effects spanning orders of magnitude. The LiCl-enolate adduct dramatically accelerates the reaction but requires superstoichiometric quantities owing to putative autoinhibition. Efforts and progress toward eliminating the requisite large excess of LiCl are discussed.
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Affiliation(s)
- Yuhui Zhou
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell
University, Ithaca, New York 14853–1301
| | - Janis Jermaks
- 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
| | - Samantha N. MacMillan
- 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
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14
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Shukla D, Babu SA. Pd‐Catalyzed Diastereoselective Intramolecular Amide
α
‐C−H Arylation in Sterically Hindered Monospirooxindole Motifs. Adv Synth Catal 2019. [DOI: 10.1002/adsc.201801732] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Dipti Shukla
- Department Chemical SciencesIndian Institute of Science Education and Research (IISER) Mohali, Knowledge City, Sector 81, SAS Nagar, Mohali, Manauli P.O. Punjab 140306 India
| | - Srinivasarao Arulananda Babu
- Department Chemical SciencesIndian Institute of Science Education and Research (IISER) Mohali, Knowledge City, Sector 81, SAS Nagar, Mohali, Manauli P.O. Punjab 140306 India
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15
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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.
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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
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16
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Schüler P, Görls H, Westerhausen M, Krieck S. Bis(trimethylsilyl)amide complexes of s-block metals with bidentate ether and amine ligands. Dalton Trans 2019; 48:8966-8975. [PMID: 31144702 DOI: 10.1039/c9dt01426h] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The synthesis of the bis(trimethylsilyl)amide complexes of alkali and alkaline-earth metals with bidentate ether and amine bases 1,2-bis(dimethylamino)ethane (tmeda), dimethyl-methoxyethylamine (dmmea), and 1,2-dimethoxyethane (dme) succeedsviaaddition of these bases to coligand-free complexes orvialigand exchange of thf adducts.
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Affiliation(s)
- Philipp Schüler
- Institute of Inorganic and Analytical Chemistry
- Friedrich Schiller University Humboldtstraße 8
- 07743 Jena
- Germany
| | - Helmar Görls
- Institute of Inorganic and Analytical Chemistry
- Friedrich Schiller University Humboldtstraße 8
- 07743 Jena
- Germany
| | - Matthias Westerhausen
- Institute of Inorganic and Analytical Chemistry
- Friedrich Schiller University Humboldtstraße 8
- 07743 Jena
- Germany
| | - Sven Krieck
- Institute of Inorganic and Analytical Chemistry
- Friedrich Schiller University Humboldtstraße 8
- 07743 Jena
- Germany
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17
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Tanoury GJ, Roeper S. A computational study on the stereoselective reduction of cyclic ketones by LiAl(OR)3H in THF. Tetrahedron 2018. [DOI: 10.1016/j.tet.2018.10.060] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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18
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Yang G, Ivanov IN, Ruther RE, Sacci RL, Subjakova V, Hallinan DT, Nanda J. Electrolyte Solvation Structure at Solid-Liquid Interface Probed by Nanogap Surface-Enhanced Raman Spectroscopy. ACS NANO 2018; 12:10159-10170. [PMID: 30226745 DOI: 10.1021/acsnano.8b05038] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Understanding the fundamental factors that drive ion solvation structure and transport is key to design high-performance, stable battery electrolytes. Reversible ion solvation and desolvation are critical to the interfacial charge-transfer process across the solid-liquid interface as well as the resulting stability of the solid electrolyte interphase. Herein, we report the study of Li+ salt solvation structure in aprotic solution in the immediate vicinity (∼20 nm) of the solid electrode-liquid interface using surface-enhanced Raman spectroscopy (SERS) from a gold nanoparticle (Au NP) monolayer. The plasmonic coupling between Au NPs produces strong electromagnetic field enhancement in the gap region, leading to a 5 orders of magnitude increase in Raman intensity for electrolyte components and their mixtures namely, lithium hexafluorophosphate, fluoroethylene carbonate, ethylene carbonate, and diethyl carbonate. Further, we estimate and compare the lithium-ion solvation number derived from SERS, standard Raman spectroscopy, and Fourier transform infrared spectroscopy experiments to monitor and ascertain the changes in the solvation shell diameter in the confined nanogap region where there is maximum enhancement of the electric field. Our findings provide a multimodal spectroscopic approach to gain fundamental insights into the molecular structure of the electrolyte at the solid-liquid interface.
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Affiliation(s)
- Guang Yang
- Oak Ridge National Laboratory , Oak Ridge , Tennessee 37831 , United States
| | - Ilia N Ivanov
- Oak Ridge National Laboratory , Oak Ridge , Tennessee 37831 , United States
| | - Rose E Ruther
- Oak Ridge National Laboratory , Oak Ridge , Tennessee 37831 , United States
| | - Robert L Sacci
- Oak Ridge National Laboratory , Oak Ridge , Tennessee 37831 , United States
| | - Veronika Subjakova
- Department of Nuclear Physics and Biophysics , Comenius University , Mlynska dolina F1 , Bratislava 84248 , Slovakia
| | - Daniel T Hallinan
- Department of Chemical and Biomedical Engineering , Florida A&M University-Florida State University College of Engineering , 2525 Pottsdamer Street , Tallahassee , Florida 32310 , United States
| | - Jagjit Nanda
- Oak Ridge National Laboratory , Oak Ridge , Tennessee 37831 , United States
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19
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Krieck S, Schüler P, Görls H, Westerhausen M. Straightforward synthesis of rubidium bis(trimethylsilyl)amide and complexes of the alkali metal bis(trimethylsilyl)amides with weakly coordinating 2,2,5,5-tetramethyltetrahydrofuran. Dalton Trans 2018; 47:12562-12569. [PMID: 29862393 DOI: 10.1039/c8dt01539b] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Rubidium bis(trimethylsilyl)amide (rubidium hexamethyldisilazanide, Rb(hmds)) is accessible on a large scale with excellent yields via a magnetite-catalyzed metalation of hexamethyldisilazane (H(hmds)) in liquid ammonia. Recrystallization of solvent-free alkali metal hexamethyldisilazanides [A(hmds)]n of sodium to cesium from solutions containing 2,2,5,5-tetramethyltetrahydrofuran (Me4THF, thf*) yields the dinuclear complexes [(thf*)A(hmds)]2, which show a rather asymmetric coordination behavior of the bulky ether ligand with strongly bent A-A-O moieties for the heavier K, Rb, and Cs congeners, whereas in the Na complex, the ether ligand is clamped between the trimethylsilyl groups. In hydrocarbon solutions, dissociation of these compounds is observed leading to the liberation of this bulky and weakly binding cyclic ether.
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Affiliation(s)
- Sven Krieck
- Institute of Inorganic and Analytical Chemistry, Friedrich Schiller University Jena, Humboldtstraße 8, D-07743 Jena, Germany.
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20
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Engelhardt F, Maaß C, Andrada DM, Herbst-Irmer R, Stalke D. Benchmarking lithium amide versus amine bonding by charge density and energy decomposition analysis arguments. Chem Sci 2018; 9:3111-3121. [PMID: 29732094 PMCID: PMC5916014 DOI: 10.1039/c7sc05368a] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2017] [Accepted: 01/30/2018] [Indexed: 12/26/2022] Open
Abstract
We investigated [{(Me2NCH2)2(C4H2N)}Li]2 (1) by means of experimental charge density calculations based on the quantum theory of atoms in molecules (QTAIM) and DFT calculations using energy decomposition analysis (EDA).
Lithium amides are versatile C–H metallation reagents with vast industrial demand because of their high basicity combined with their weak nucleophilicity, and they are applied in kilotons worldwide annually. The nuclearity of lithium amides, however, modifies and steers reactivity, region- and stereo-selectivity and product diversification in organic syntheses. In this regard, it is vital to understand Li–N bonding as it causes the aggregation of lithium amides to form cubes or ladders from the polar Li–N covalent metal amide bond along the ring stacking and laddering principle. Deaggregation, however, is more governed by the Li←N donor bond to form amine adducts. The geometry of the solid state structures already suggests that there is σ- and π-contribution to the covalent bond. To quantify the mutual influence, we investigated [{(Me2NCH2)2(C4H2N)}Li]2 (1) by means of experimental charge density calculations based on the quantum theory of atoms in molecules (QTAIM) and DFT calculations using energy decomposition analysis (EDA). This new approach allows for the grading of electrostatic Li+N–, covalent Li–N and donating Li←N bonding, and provides a way to modify traditional widely-used heuristic concepts such as the –I and +I inductive effects. The electron density ρ(r) and its second derivative, the Laplacian ∇2ρ(r), mirror the various types of bonding. Most remarkably, from the topological descriptors, there is no clear separation of the lithium amide bonds from the lithium amine donor bonds. The computed natural partial charges for lithium are only +0.58, indicating an optimal density supply from the four nitrogen atoms, while the Wiberg bond orders of about 0.14 au suggest very weak bonding. The interaction energy between the two pincer molecules, (C4H2N)22–, with the Li22+ moiety is very strong (ca. –628 kcal mol–1), followed by the bond dissociation energy (–420.9 kcal mol–1). Partitioning the interaction energy into the Pauli (ΔEPauli), dispersion (ΔEdisp), electrostatic (ΔEelstat) and orbital (ΔEorb) terms gives a 71–72% ionic and 25–26% covalent character of the Li–N bond, different to the old dichotomy of 95 to 5%. In this regard, there is much more potential to steer the reactivity with various substituents and donor solvents than has been anticipated so far.
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Affiliation(s)
- Felix Engelhardt
- Institut für Anorganische Chemie , Georg-August-Universität Göttingen , Tammannstraße 4 , 37077 Göttingen , Germany
| | - Christian Maaß
- Institut für Anorganische Chemie , Georg-August-Universität Göttingen , Tammannstraße 4 , 37077 Göttingen , Germany
| | - Diego M Andrada
- Krupp-Chair of General and Inorganic Chemistry , Universität des Saarlandes , Campus Gebäude C4.1 , 66123 Saarbrücken , Germany . ;
| | - Regine Herbst-Irmer
- Institut für Anorganische Chemie , Georg-August-Universität Göttingen , Tammannstraße 4 , 37077 Göttingen , Germany
| | - Dietmar Stalke
- Institut für Anorganische Chemie , Georg-August-Universität Göttingen , Tammannstraße 4 , 37077 Göttingen , Germany
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21
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Malladi S, Nadh RV, Babu KS, Babu PS. Synthesis and antibacterial activity studies of 2,4-di substituted furan derivatives. BENI-SUEF UNIVERSITY JOURNAL OF BASIC AND APPLIED SCIENCES 2017. [DOI: 10.1016/j.bjbas.2017.08.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
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22
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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.
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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
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23
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Abstract
Several Gold's reagents were synthesized from cyanuric chloride and N,N-dialkylformamides. These synthetic equivalents of N,N-dimethylformamide dimethyl acetal were used in an optimized and scalable procedure for the regioselective synthesis of a variety of enaminones from ketone starting materials, whose utility was demonstrated by the stereoselective synthesis of Rawal-type dienes.
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24
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Tai O, Hopson R, Williard PG. Ligand Binding Constants to Lithium Hexamethyldisilazide Determined by Diffusion-Ordered NMR Spectroscopy. J Org Chem 2017; 82:6223-6231. [PMID: 28562035 DOI: 10.1021/acs.joc.7b00800] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We report the direct measurement of ligand-binding constants of organolithium complexes using a 1H NMR/diffusion-ordered NMR spectroscopy (DOSY) titration technique. Lithium hexamethyldisilazide complexes with ethereal and ester donor ligands (THF, diethyl ether, MTBE, THP, tert-butyl acetate) are characterized using 1H NMR and X-ray crystallography. Their aggregation and solvation states are confirmed using diffusion coefficient-formula weight correlation analysis, and the 1H NMR/DOSY titration technique is applied to obtain their binding constants. Our work suggests that steric hindrance of ethereal ligands plays an important role in the aggregation, solvation, and reactivity of these complexes. It is noteworthy that diffusion methodology is utilized to obtain binding constants.
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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
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25
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Separation of tetrahydrofuran using RSM optimized accelerator-sulfur-filler of rubber membranes: Systematic optimization and comprehensive mechanistic study. KOREAN J CHEM ENG 2017. [DOI: 10.1007/s11814-017-0021-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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26
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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.
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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
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27
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Koch A, Görls H, Krieck S, Westerhausen M. Coordination behavior of bidentate bis(carbenes) at alkali metal bis(trimethylsilyl)amides. Dalton Trans 2017; 46:9058-9067. [DOI: 10.1039/c7dt01538k] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Crystallization of LiN(SiMe3)2 from 2,2,5,5-tetramethyltetrahydrofuran yields the base-free tetramer. Strong carbenes monomerize the lithium bis(trimethylsilyl)amides, whereas the heavier congeners from carbene-stabilized dimers [AN(SiMe3)2]2 with A = Na, K.
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Affiliation(s)
- Alexander Koch
- Friedrich Schiller University Jena
- Institute of Inorganic and Analytical Chemistry
- D-07743 Jena
- Germany
| | - Helmar Görls
- Friedrich Schiller University Jena
- Institute of Inorganic and Analytical Chemistry
- D-07743 Jena
- Germany
| | - Sven Krieck
- Friedrich Schiller University Jena
- Institute of Inorganic and Analytical Chemistry
- D-07743 Jena
- Germany
| | - Matthias Westerhausen
- Friedrich Schiller University Jena
- Institute of Inorganic and Analytical Chemistry
- D-07743 Jena
- Germany
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28
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Cross-Coupling of Organolithium with Ethers or Aryl Ammonium Salts by C−O or C−N Bond Cleavage. Chemistry 2016; 22:15693-15699. [DOI: 10.1002/chem.201603436] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Indexed: 12/14/2022]
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29
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Neufeld R, Michel R, Herbst-Irmer R, Schöne R, Stalke D. Introducing a Hydrogen-Bond Donor into a Weakly Nucleophilic Brønsted Base: Alkali Metal Hexamethyldisilazides (MHMDS, M=Li, Na, K, Rb and Cs) with Ammonia. Chemistry 2016; 22:12340-6. [PMID: 27457218 DOI: 10.1002/chem.201600833] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2016] [Revised: 05/25/2016] [Indexed: 11/08/2022]
Abstract
Alkali metal 1,1,1,3,3,3-hexamethyldisilazide (MHMDSs) are one of the most utilised weakly nucleophilic Brønsted bases in synthetic chemistry and especially in natural product synthesis. Like lithium organics, they aggregate depending on the employed donor solvents. Thus, they show different reactivity and selectivity as a function of their aggregation and solvation state. To date, monomeric LiHMDS with monodentate donor bases was only characterised in solution. Since the first preparation of LiHMDS in 1959 by Wannagat and Niederprüm, all efforts to crystallise monomeric LiHMDS in the absence of chelating ligands failed. Herein, we present ammonia adducts of LiHMDS, NaHMDS, KHMDS, RbHMDS and CsHMDS with unprecedented aggregation motifs: 1) The hitherto missing monomeric key compound in the LiHMDS aggregation architectures. Monomeric crystal structures of trisolvated LiHMDS (1) and NaHMDS (2), showing unique intermolecular hydrogen bonds, 2) the unprecedented tetrasolvated KHMDS (3) and RbHMDS (4) dimers and 3) the disolvated CsHMDS (5) dimer with very close intermolecular Si-CH3 ⋅⋅⋅Cs s-block "agostic" interactions have been prepared and characterised by single-crystal X-ray structure analysis.
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Affiliation(s)
- Roman Neufeld
- Institut für Anorganische Chemie, Georg-August-Universität, Tammannstrasse 4, 37077, Göttingen, Germany
| | - Reent Michel
- Institut für Anorganische Chemie, Georg-August-Universität, Tammannstrasse 4, 37077, Göttingen, Germany
| | - Regine Herbst-Irmer
- Institut für Anorganische Chemie, Georg-August-Universität, Tammannstrasse 4, 37077, Göttingen, Germany
| | - Ralf Schöne
- Institut für Anorganische Chemie, Georg-August-Universität, Tammannstrasse 4, 37077, Göttingen, Germany
| | - Dietmar Stalke
- Institut für Anorganische Chemie, Georg-August-Universität, Tammannstrasse 4, 37077, Göttingen, Germany.
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Houghton MJ, Biok NA, Huck CJ, Algera RF, Keresztes I, Wright SW, Collum DB. Lithium Enolates Derived from Pyroglutaminol: Aggregation, Solvation, and Atropisomerism. J Org Chem 2016; 81:4149-57. [PMID: 27035057 PMCID: PMC5245164 DOI: 10.1021/acs.joc.6b00459] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Lithium enolates derived from protected pyroglutaminols were characterized by using (6)Li, (13)C, and (19)F NMR spectroscopies in conjunction with the method of continuous variations. Mixtures of tetrasolvated dimers and tetrasolvated tetramers in different proportions depend on the steric demands of the hemiaminal protecting group, tetrahydrofuran concentration, and the presence or absence of an α-fluoro moiety. The high steric demands of the substituted bicyclo[3.3.0] ring system promote dimers to an unusual extent and allow solvents and atropisomers in cubic tetramers to be observed in the slow-exchange limit. Pyridine used as a (6)Li chemical shift reagent proved useful in assigning solvation numbers.
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Affiliation(s)
- Michael J. Houghton
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853–1301
| | - Naomi A. Biok
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853–1301
| | - Christopher J. Huck
- 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
| | - Ivan Keresztes
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853–1301
| | - Stephen W. Wright
- Worldwide Medicinal Chemistry, Pfizer Global Research and Development, 445 Eastern Point Road, Groton, CT 06340
| | - David B. Collum
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853–1301
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31
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Dauer DR, Flügge M, Herbst-Irmer R, Stalke D. Bis-(benzothiazol-2-yl)-amines and their metal amides: a structural comparison in the solid state. Dalton Trans 2016; 45:6136-48. [DOI: 10.1039/c5dt03911h] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A series of functionalised bis-(benzothiazol-2-yl)-amine ligands and the related dimethylaluminium amides were synthesised and characterised. The solid state structural comparison reveals various coordination motifs, specific folding parameters and hydrogen bonding patterns in detail and guide the way to future Janus head ligand design.
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Affiliation(s)
- David-R. Dauer
- Institut für Anorganische Chemie
- Georg-August-Universität Göttingen
- 37077 Göttingen
- Germany
| | - Melchior Flügge
- Institut für Anorganische Chemie
- Georg-August-Universität Göttingen
- 37077 Göttingen
- Germany
| | - Regine Herbst-Irmer
- Institut für Anorganische Chemie
- Georg-August-Universität Göttingen
- 37077 Göttingen
- Germany
| | - Dietmar Stalke
- Institut für Anorganische Chemie
- Georg-August-Universität Göttingen
- 37077 Göttingen
- Germany
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32
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Jin KJ, Collum DB. Solid-State and Solution Structures of Glycinimine-Derived Lithium Enolates. J Am Chem Soc 2015; 137:14446-55. [PMID: 26554898 PMCID: PMC4762874 DOI: 10.1021/jacs.5b09524] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
A combination of crystallographic, spectroscopic, and computational studies was applied to study the structures of lithium enolates derived from glycinimines of benzophenone and (+)-camphor. The solvents examined included toluene and toluene containing various concentrations of tetrahydrofuran, N,N,N',N'-tetramethylethylenediamine (TMEDA), (R,R)-N,N,N',N'-tetramethylcyclohexanediamine [(R,R)-TMCDA], and (S,S)-N,N,N',N'-tetramethylcyclohexanediamine [(S,S)-TMCDA]. Crystal structures show chelated monomers, symmetric disolvated dimers, S4-symmetric tetramers, and both S6- and D3d-symmetric hexamers. (6)Li NMR spectroscopic studies in conjunction with the method of continuous variations show how these species distribute in solution. Density functional theory computations offer insights into experimentally elusive details.
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Affiliation(s)
- Kyoung Joo Jin
- 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
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Tallmadge EH, Collum DB. Evans Enolates: Solution Structures of Lithiated Oxazolidinone-Derived Enolates. J Am Chem Soc 2015; 137:13087-95. [PMID: 26437278 PMCID: PMC4765922 DOI: 10.1021/jacs.5b08207] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The results of a combination of (6)Li and (13)C NMR spectroscopic and computational studies of oxazolidinone-based lithium enolates-Evans enolates-in tetrahydrofuran (THF) solution revealed a mixture of dimers, tetramers, and oligomers (possibly ladders). The distribution depended on the structure of the oxazolidinone auxiliary, substituent on the enolate, and THF concentration (in THF/toluene mixtures). The unsolvated tetrameric form contained a D(2d)-symmetric core structure, whereas the dimers were determined experimentally and computationally to be trisolvates with several isomeric forms.
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Affiliation(s)
- Evan H Tallmadge
- Baker Laboratory, Department of Chemistry and Chemical Biology, Cornell University , Ithaca, New York 14853-1301, United States
| | - David B Collum
- Baker Laboratory, Department of Chemistry and Chemical Biology, Cornell University , Ithaca, New York 14853-1301, United States
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Lou S, McKenna GM, Tymonko SA, Ramirez A, Benkovics T, Conlon DA, González-Bobes F. Syn-Selective Synthesis of β-Branched α-Amino Acids by Alkylation of Glycine-Derived Imines with Secondary Sulfonates. Org Lett 2015; 17:5000-3. [DOI: 10.1021/acs.orglett.5b02448] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Sha Lou
- Chemical Development, Bristol-Myers Squibb, One Squibb Drive, New Brunswick, New Jersey 08903, United States
| | - Grace M. McKenna
- Chemical Development, Bristol-Myers Squibb, One Squibb Drive, New Brunswick, New Jersey 08903, United States
| | - Steven A. Tymonko
- Chemical Development, Bristol-Myers Squibb, One Squibb Drive, New Brunswick, New Jersey 08903, United States
| | - Antonio Ramirez
- Chemical Development, Bristol-Myers Squibb, One Squibb Drive, New Brunswick, New Jersey 08903, United States
| | - Tamas Benkovics
- Chemical Development, Bristol-Myers Squibb, One Squibb Drive, New Brunswick, New Jersey 08903, United States
| | - David A. Conlon
- Chemical Development, Bristol-Myers Squibb, One Squibb Drive, New Brunswick, New Jersey 08903, United States
| | - Francisco González-Bobes
- Chemical Development, Bristol-Myers Squibb, One Squibb Drive, New Brunswick, New Jersey 08903, United States
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35
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Sharif S, Rucker RP, Chandrasoma N, Mitchell D, Rodriguez MJ, Froese RDJ, Organ MG. Selective Monoarylation of Primary Amines Using the Pd-PEPPSI-IPentClPrecatalyst. Angew Chem Int Ed Engl 2015. [DOI: 10.1002/ange.201502822] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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36
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Sharif S, Rucker RP, Chandrasoma N, Mitchell D, Rodriguez MJ, Froese RDJ, Organ MG. Selective Monoarylation of Primary Amines Using the Pd-PEPPSI-IPentClPrecatalyst. Angew Chem Int Ed Engl 2015; 54:9507-11. [DOI: 10.1002/anie.201502822] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2015] [Indexed: 12/20/2022]
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37
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Essafi S, Tomasi S, Aggarwal VK, Harvey JN. Homologation of boronic esters with organolithium compounds: a computational assessment of mechanism. J Org Chem 2014; 79:12148-58. [PMID: 25318004 DOI: 10.1021/jo502020e] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Ab initio calculations are reported for the reaction of methyl boronic ester with organolithium reagents with α-leaving groups. The best calculations rely on density functional theory prediction of structures and coupled-cluster theory calculation of accurate potential energies. The results provide strong confirmation of the feasibility of a two-step mechanism with rapid initial formation of a boron-ate complex followed by slower migration of methyl from boron to carbon with loss of the leaving group. The calculated free energy of activation is consistent with observed kinetic behavior, and the calculations provide a framework for exploring substituent and other effects on reactivity. Obtaining reasonable agreement with experiment in this way is not trivial and requires careful treatment of level of theory (density functional theory calculations tend to yield inaccurate results), of conformational complexity, especially for the ate complexes, and of the nature of the microscopic model of reactants and solvent. The methodological challenges and possible pitfalls, many of which are relevant more broadly to computational modeling of organic reaction mechanisms, are discussed in detail.
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Affiliation(s)
- Stéphanie Essafi
- School of Chemistry, University of Bristol , Cantock's Close, Bristol BS8 1TS, U.K
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38
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Rathman T‘L, Schwindeman JA. Preparation, Properties, and Safe Handling of Commercial Organolithiums: Alkyllithiums, Lithium sec-Organoamides, and Lithium Alkoxides. Org Process Res Dev 2014. [DOI: 10.1021/op500161b] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Affiliation(s)
- Terry ‘Li’ Rathman
- t-Links Consulting, 3843 Gardner Park Drive, Gastonia, North Carolina 28054, United States
| | - James A. Schwindeman
- Rohner Inc., 4066 Belle
Meade Circle, Belmont, North
Carolina 28012, United States
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39
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Pöppler A, Granitzka M, Herbst‐Irmer R, Chen Y, Iversen BB, John M, Mata RA, Stalke D. Charakterisierung eines Mehrkomponenten‐Lithiumlithats durch eine Kombination von Röntgenstrukturanalyse, NMR‐Spektroskopie und theoretischen Studien. Angew Chem Int Ed Engl 2014. [DOI: 10.1002/ange.201406320] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Ann‐Christin Pöppler
- Institut für Anorganische Chemie der Universität Göttingen, Tammannstraße 4, 37077 Göttingen (Deutschland)
| | - Markus Granitzka
- Institut für Anorganische Chemie der Universität Göttingen, Tammannstraße 4, 37077 Göttingen (Deutschland)
| | - Regine Herbst‐Irmer
- Institut für Anorganische Chemie der Universität Göttingen, Tammannstraße 4, 37077 Göttingen (Deutschland)
| | | | - Bo B. Iversen
- Center for Materials Crystallography, Department of Chemistry and iNano, Aarhus University (Dänemark)
| | - Michael John
- Institut für Anorganische Chemie der Universität Göttingen, Tammannstraße 4, 37077 Göttingen (Deutschland)
| | - Ricardo A. Mata
- Institut für Physikalische Chemie der Universität Göttingen (Deutschland)
| | - Dietmar Stalke
- Institut für Anorganische Chemie der Universität Göttingen, Tammannstraße 4, 37077 Göttingen (Deutschland)
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40
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Pöppler AC, Granitzka M, Herbst-Irmer R, Chen YS, Iversen BB, John M, Mata RA, Stalke D. Characterization of a Multicomponent Lithium Lithiate from a Combined X-Ray Diffraction, NMR Spectroscopy, and Computational Approach. Angew Chem Int Ed Engl 2014; 53:13282-7. [DOI: 10.1002/anie.201406320] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2014] [Indexed: 11/10/2022]
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41
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Su C, Guang J, Li W, Wu K, Hopson R, Williard PG. Chiral Lithium Diamides Derived from Linked N-Isopropyl Valinol or Alaninol. J Am Chem Soc 2014; 136:11735-47. [DOI: 10.1021/ja505179y] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Chicheung Su
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States
| | - Jie Guang
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States
| | - Weibin Li
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States
| | - Kuiwang Wu
- 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
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42
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Bruneau A, Liou L, Collum DB. Solution structures of lithium amino alkoxides used in highly enantioselective 1,2-additions. J Am Chem Soc 2014; 136:2885-91. [PMID: 24471766 PMCID: PMC3985715 DOI: 10.1021/ja412210d] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2013] [Indexed: 01/25/2023]
Abstract
Lithium ephedrates and norcarane-derived lithium amino alkoxides used to effect highly enantioselective 1,2-additions on large scales have been characterized in toluene and tetrahydrofuran. The method of continuous variations in conjunction with (6)Li NMR spectroscopy reveals that the lithium amino alkoxides are tetrameric. In each case, low-temperature (6)Li NMR spectra show stereoisomerically pure homoaggregates displaying resonances consistent with an S4-symmetric cubic core rather than the alternative D2d core. These assignments are supported by density functional theory computations and conform to X-ray crystal structures. Slow aggregate exchanges are discussed in the context of amino alkoxides as chiral auxiliaries.
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Affiliation(s)
- Angela
M. Bruneau
- Department of Chemistry and
Chemical Biology Baker Laboratory, Cornell
University, Ithaca, New York 14853-1301, United States
| | - Lara Liou
- 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
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43
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Su C, Hopson R, Williard PG. Influence of Steric Factors on Chiral Lithium Amide Aggregates. J Am Chem Soc 2014; 136:3246-55. [DOI: 10.1021/ja4123957] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Chicheung Su
- Department of Chemistry, Brown University, 324 Brook Street, Providence, Rhode Island 02912 United States
| | - Russell Hopson
- Department of Chemistry, Brown University, 324 Brook Street, Providence, Rhode Island 02912 United States
| | - Paul G. Williard
- Department of Chemistry, Brown University, 324 Brook Street, Providence, Rhode Island 02912 United States
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44
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Su C, Guang J, Williard PG. Structures of Lithium N-Monosubstituted Anilides: Trisolvated Monomer to Tetrasolvated Dimer. J Org Chem 2014; 79:1032-9. [DOI: 10.1021/jo402498z] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- Chicheung Su
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States
| | - Jie Guang
- 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
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45
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Mikami K, Tomita Y, Iida T, Hashimoto R, Itoh Y. No Catalyst, Radical Initiator and Photochemical Irradiation Approach to Direct α-Trifluoromethylation of Lithium Enolates. HETEROCYCLES 2014. [DOI: 10.3987/com-13-s(s)95] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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46
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Dynamics of the Lithium Amide/Alkyllithium Interactions: Mixed Dimers and Beyond. TOP ORGANOMETAL CHEM 2014. [DOI: 10.1007/3418_2014_75] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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47
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Su C, Hopson R, Williard PG. Isotopically Enriched 13C Diffusion-Ordered NMR Spectroscopy: Analysis of Methyllithium. J Org Chem 2013; 78:11733-46. [DOI: 10.1021/jo401740g] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Affiliation(s)
- Chicheung Su
- 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
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48
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Ma Y, Stivala CE, Wright AM, Hayton T, Liang J, Keresztes I, Lobkovsky E, Collum DB, Zakarian A. Enediolate-dilithium amide mixed aggregates in the enantioselective alkylation of arylacetic acids: structural studies and a stereochemical model. J Am Chem Soc 2013; 135:16853-64. [PMID: 23654300 PMCID: PMC3818356 DOI: 10.1021/ja403076u] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A combination of X-ray crystallography, (6)Li, (15)N, and (13)C NMR spectroscopies, and density functional theory computations affords insight into the structures and reactivities of intervening aggregates underlying highly selective asymmetric alkylations of carboxylic acid dianions (enediolates) mediated by the dilithium salt of a C2-symmetric chiral tetraamine. Crystallography shows a trilithiated n-butyllithium-dilithiated amide that has dimerized to a hexalithiated form. Spectroscopic studies implicate the non-dimerized trilithiated mixed aggregate. Reaction of the dilithiated amide with the dilithium enediolate derived from phenylacetic acid affords a tetralithio aggregate comprised of the two dianions in solution and the dimerized octalithio form in the solid state. Computational studies shed light on the details of the solution structures and afford a highly predictive stereochemical model.
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Affiliation(s)
- Yun Ma
- Department of Chemistry and Chemical Biology Baker Laboratory, Cornell University, Ithaca, New York 14853–1301, Telephone: (607)-255-4879; Fax: (850)-644-8281
| | - Craig E. Stivala
- Contribution from the Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA 93106; Telephone: (805)-893-3717; Fax: (805)-893-4120
| | - Ashley M. Wright
- Contribution from the Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA 93106; Telephone: (805)-893-3717; Fax: (805)-893-4120
| | - Trevor Hayton
- Contribution from the Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA 93106; Telephone: (805)-893-3717; Fax: (805)-893-4120
| | - Jun Liang
- Department of Chemistry and Chemical Biology Baker Laboratory, Cornell University, Ithaca, New York 14853–1301, Telephone: (607)-255-4879; Fax: (850)-644-8281
| | - Ivan Keresztes
- Department of Chemistry and Chemical Biology Baker Laboratory, Cornell University, Ithaca, New York 14853–1301, Telephone: (607)-255-4879; Fax: (850)-644-8281
| | - Emil Lobkovsky
- Department of Chemistry and Chemical Biology Baker Laboratory, Cornell University, Ithaca, New York 14853–1301, Telephone: (607)-255-4879; Fax: (850)-644-8281
| | - David B. Collum
- Department of Chemistry and Chemical Biology Baker Laboratory, Cornell University, Ithaca, New York 14853–1301, Telephone: (607)-255-4879; Fax: (850)-644-8281
| | - Armen Zakarian
- Contribution from the Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA 93106; Telephone: (805)-893-3717; Fax: (805)-893-4120
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49
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Mulvey RE, Robertson SD. Synthetically important alkali-metal utility amides: lithium, sodium, and potassium hexamethyldisilazides, diisopropylamides, and tetramethylpiperidides. Angew Chem Int Ed Engl 2013; 52:11470-87. [PMID: 24133015 DOI: 10.1002/anie.201301837] [Citation(s) in RCA: 151] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2013] [Indexed: 11/08/2022]
Abstract
Most synthetic chemists will have at some point utilized a sterically demanding secondary amide (R2 N(-) ). The three most important examples, lithium 1,1,1,3,3,3-hexamethyldisilazide (LiHMDS), lithium diisopropylamide (LiDA), and lithium 2,2,6,6-tetramethylpiperidide (LiTMP)-the "utility amides"-have long been indispensible particularly for lithiation (Li-H exchange) reactions. Like organolithium compounds, they exhibit aggregation phenomena and strong Lewis acidity, and thus appear in distinct forms depending on the solvents employed. The structural chemistry of these compounds as well as their sodium and potassium congeners are described in the absence or in the presence of the most synthetically significant donor solvents tetrahydrofuran (THF) and N,N,N',N'-tetramethylethylenediamine (TMEDA) or closely related solvents. Examples of hetero-alkali-metal amides, an increasingly important composition because of the recent escalation of interest in mixed-metal synergic effects, are also included.
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Affiliation(s)
- Robert E Mulvey
- WestCHEM, Department of Pure and Applied Chemistry, University of Strathclyde, Glasgow, G1 1XL (UK).
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50
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Mulvey RE, Robertson SD. Nützliche Alkalimetallamide für die Synthese: Lithium-, Natrium- und Kaliumhexamethyldisilazide, -diisopropylamide und -tetramethylpiperidide. Angew Chem Int Ed Engl 2013. [DOI: 10.1002/ange.201301837] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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