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 DOI: 10.1021/jacs.4c03418] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [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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Davison N, Hemingway JM, Waddell PG, Lu E. Lithium, sodium and potassium enolate aggregates and monomers: syntheses and structures. Dalton Trans 2024; 53:4719-4728. [PMID: 38362928 DOI: 10.1039/d4dt00211c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2024]
Abstract
In this Article, we report the syntheses and comparative structural studies of lithium, sodium, and potassium anthracen-9-yl enolates, as their aggregates (Li, Na: hexamer; K: tetramer) and ligand-stabilized monomers (for Li and Na). The monomers add new members to the rare collection of group-1 metal monomeric enolates. Moreover, the series covers different group-1 metal cations (Li+, Na+ and K+) and aggregate sizes, allowing comparative structural studies to elucidate how the metal identity and aggregate size influence the enolate structure.
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Affiliation(s)
- Nathan Davison
- Chemistry-School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK.
| | - Jack M Hemingway
- Chemistry-School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK.
| | - Paul G Waddell
- Chemistry-School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK.
| | - Erli Lu
- Chemistry-School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK.
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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: 1] [Impact Index Per Article: 0.5] [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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Berger T, Lebon J, Maichle‐Mössmer C, Anwander R. CeCl
3
/
n
‐BuLi: Enträtselung von Imamotos Organocer‐Reagenz. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202103889] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- Tassilo Berger
- Institut für Anorganische Chemie Eberhard Karls Universität Tübingen Auf der Morgenstelle 18 72076 Tübingen Deutschland
| | - Jakob Lebon
- Institut für Anorganische Chemie Eberhard Karls Universität Tübingen Auf der Morgenstelle 18 72076 Tübingen Deutschland
| | - Cäcilia Maichle‐Mössmer
- Institut für Anorganische Chemie Eberhard Karls Universität Tübingen Auf der Morgenstelle 18 72076 Tübingen Deutschland
| | - Reiner Anwander
- Institut für Anorganische Chemie Eberhard Karls Universität Tübingen Auf der Morgenstelle 18 72076 Tübingen Deutschland
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5
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Berger T, Lebon J, Maichle-Mössmer C, Anwander R. CeCl 3 /n-BuLi: Unraveling Imamoto's Organocerium Reagent. Angew Chem Int Ed Engl 2021; 60:15622-15631. [PMID: 33905590 PMCID: PMC8362106 DOI: 10.1002/anie.202103889] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2021] [Indexed: 12/31/2022]
Abstract
CeCl3(thf) reacts at low temperatures with MeLi, t‐BuLi, and n‐BuLi to isolable organocerium complexes. Solvent‐dependent extensive n‐BuLi dissociation is revealed by 7Li NMR spectroscopy, suggesting “Ce(n‐Bu)3(thf)x” or solvent‐separated ion pairs like “[Li(thf)4][Ce(n‐Bu)4(thf)y]” as the dominant species of the Imamoto reagent. The stability of complexes Li3Ln(n‐Bu)6(thf)4 increases markedly with decreasing LnIII size. Closer inspection of the solution behavior of crystalline Li3Lu(n‐Bu)6(thf)4 and mixtures of LuCl3(thf)2/n‐BuLi in THF indicates occurring n‐BuLi dissociation only at molar ratios of <1:3. n‐BuLi‐depleted complex LiLu(n‐Bu)3Cl(tmeda)2 was obtained by treatment of Li2Lu(n‐Bu)5(tmeda)2 with ClSiMe3, at the expense of LiCl incorporation. Imamoto's ketone/tertiary alcohol transformation was examined with 1,3‐diphenylpropan‐2‐one, affording 99 % of alcohol.
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Affiliation(s)
- Tassilo Berger
- Institut für Anorganische Chemie, Eberhard Karls Universität Tübingen, Auf der Morgenstelle 18, 72076, Tübingen, Germany
| | - Jakob Lebon
- Institut für Anorganische Chemie, Eberhard Karls Universität Tübingen, Auf der Morgenstelle 18, 72076, Tübingen, Germany
| | - Cäcilia Maichle-Mössmer
- Institut für Anorganische Chemie, Eberhard Karls Universität Tübingen, Auf der Morgenstelle 18, 72076, Tübingen, Germany
| | - Reiner Anwander
- Institut für Anorganische Chemie, Eberhard Karls Universität Tübingen, Auf der Morgenstelle 18, 72076, Tübingen, Germany
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6
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Pasturaud K, Rkein B, Sanselme M, Sebban M, Lakhdar S, Durandetti M, Legros J, Chataigner I. The facile dearomatization of nitroaromatic compounds using lithium enolates of unsaturated ketones in conjugate additions and (4+2) formal cycloadditions. Chem Commun (Camb) 2019; 55:7494-7497. [PMID: 31185071 DOI: 10.1039/c9cc02924a] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The dearomatization of conventional nitroarenes by lithiated enolates derived from methyl vinyl ketones easily takes place, following a formal (4+2) cycloaddition process. While nitroindoles react readily with in situ generated conjugated enolates, the deaggregation of these latter species using HMPA extends the reaction scope to the more aromatic nitronaphthalenes and pyridines.
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Affiliation(s)
- Karine Pasturaud
- Normandie Univ., UNIROUEN, INSA Rouen, CNRS, COBRA, 76000 Rouen, France.
| | - Batoul Rkein
- Normandie Univ., UNIROUEN, INSA Rouen, CNRS, COBRA, 76000 Rouen, France.
| | | | - Muriel Sebban
- Normandie Univ., UNIROUEN, INSA Rouen, CNRS, COBRA, 76000 Rouen, France.
| | - Sami Lakhdar
- Normandie Univ., LCMT, ENSICAEN, UNICAEN, CNRS, 6, Boulevard Maréchal Juin, Caen 14000, France
| | - Muriel Durandetti
- Normandie Univ., UNIROUEN, INSA Rouen, CNRS, COBRA, 76000 Rouen, France.
| | - Julien Legros
- Normandie Univ., UNIROUEN, INSA Rouen, CNRS, COBRA, 76000 Rouen, France.
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7
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Ji X, Li J, Wu M, Cao S. Facile Synthesis of 3-Arylindenes by HMPA-Promoted Direct Arylation of Indenes with Aryl Fluorides. ACS OMEGA 2018; 3:10099-10106. [PMID: 31459139 PMCID: PMC6645374 DOI: 10.1021/acsomega.8b01542] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/05/2018] [Accepted: 08/02/2018] [Indexed: 06/10/2023]
Abstract
A rapid and efficient approach to 3-arylated indenes by reactions of indenes with unactivated fluoroarenes with the assistance of lithium diisopropylamide and hexamethylphosphoramide at room temperature was developed.
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8
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Ji X, Zhao X, Shi H, Cao S. HMPA-Promoted Siladifluoromethylation of Di-, and Triarylmethanes with the Ruppert-Prakash Reagent. Chem Asian J 2017; 12:2794-2798. [PMID: 28940982 DOI: 10.1002/asia.201701224] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2017] [Revised: 09/17/2017] [Indexed: 11/11/2022]
Affiliation(s)
- Xinfei Ji
- Shanghai Key Laboratory of Chemical Biology, School of Pharmacy; East China University of Science and Technology (ECUST); Shanghai 200237 P.R. China
| | - Xianghu Zhao
- Shanghai Key Laboratory of Chemical Biology, School of Pharmacy; East China University of Science and Technology (ECUST); Shanghai 200237 P.R. China
| | - Hongyan Shi
- Shanghai Key Laboratory of Chemical Biology, School of Pharmacy; East China University of Science and Technology (ECUST); Shanghai 200237 P.R. China
| | - Song Cao
- Shanghai Key Laboratory of Chemical Biology, School of Pharmacy; East China University of Science and Technology (ECUST); Shanghai 200237 P.R. China
- Key Laboratory of Organofluorine Chemistry, Shanghai Institute of Organic Chemistry; Chinese Academy of Sciences; Shanghai 200032 P.R. China
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9
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Barozzino-Consiglio G, Hamdoun G, Fressigné C, Harrison-Marchand A, Maddaluno J, Oulyadi H. A Combined 1
H/6
Li NMR DOSY Strategy Finally Uncovers the Structure of Isopropyllithium in THF. Chemistry 2017; 23:12475-12479. [DOI: 10.1002/chem.201702990] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Indexed: 11/09/2022]
Affiliation(s)
| | - Ghanem Hamdoun
- Normandie Université, UNIROUEN, INSA de Rouen, CNRS; Laboratoire COBRA (UMR 6014 & FR 3038); 76000 Rouen France
| | - Catherine Fressigné
- Normandie Université, UNIROUEN, INSA de Rouen, CNRS; Laboratoire COBRA (UMR 6014 & FR 3038); 76000 Rouen France
| | - Anne Harrison-Marchand
- Normandie Université, UNIROUEN, INSA de Rouen, CNRS; Laboratoire COBRA (UMR 6014 & FR 3038); 76000 Rouen France
| | - Jacques Maddaluno
- Normandie Université, UNIROUEN, INSA de Rouen, CNRS; Laboratoire COBRA (UMR 6014 & FR 3038); 76000 Rouen France
| | - Hassan Oulyadi
- Normandie Université, UNIROUEN, INSA de Rouen, CNRS; Laboratoire COBRA (UMR 6014 & FR 3038); 76000 Rouen France
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10
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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.
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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,
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11
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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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12
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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: 5] [Impact Index Per Article: 0.6] [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).
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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
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13
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Honda K, Harris TV, Hatanaka M, Morokuma K, Mikami K. Computational S
N
2‐Type Mechanism for the Difluoromethylation of Lithium Enolate with Fluoroform through Bimetallic C−F Bond Dual Activation. Chemistry 2016; 22:8796-800. [DOI: 10.1002/chem.201601090] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2016] [Indexed: 11/05/2022]
Affiliation(s)
- Kazuya Honda
- Department of Applied Chemistry Tokyo Institute of Technology Tokyo 152-8552 Japan
| | - Travis V. Harris
- Fukui Institute for Fundamental Chemistry Kyoto University Kyoto 606-8103 Japan
- Department of Chemistry University of Puget Sound Tacoma Washington 98416 USA
| | - Miho Hatanaka
- Fukui Institute for Fundamental Chemistry Kyoto University Kyoto 606-8103 Japan
- Department of Chemistry Faculty of Science and Engineering Kinki University Osaka 577-8502 Japan
| | - Keiji Morokuma
- Fukui Institute for Fundamental Chemistry Kyoto University Kyoto 606-8103 Japan
| | - Koichi Mikami
- Department of Applied Chemistry Tokyo Institute of Technology Tokyo 152-8552 Japan
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