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Riggs JC, Ramirez A, Cremeens ME, Bashore CG, Candler J, Wirtz MC, Coe JW, Collum DB. Structural and Rate Studies of the Formation of Substituted Benzynes. J Am Chem Soc 2008; 130:3406-12. [DOI: 10.1021/ja0754655] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Jason C. Riggs
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, and Pfizer Global Research and Development, Groton Laboratories, Pfizer, Inc., Groton, Connecticut 06340
| | - Antonio Ramirez
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, and Pfizer Global Research and Development, Groton Laboratories, Pfizer, Inc., Groton, Connecticut 06340
| | - Matthew E. Cremeens
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, and Pfizer Global Research and Development, Groton Laboratories, Pfizer, Inc., Groton, Connecticut 06340
| | - Crystal G. Bashore
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, and Pfizer Global Research and Development, Groton Laboratories, Pfizer, Inc., Groton, Connecticut 06340
| | - John Candler
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, and Pfizer Global Research and Development, Groton Laboratories, Pfizer, Inc., Groton, Connecticut 06340
| | - Michael C. Wirtz
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, and Pfizer Global Research and Development, Groton Laboratories, Pfizer, Inc., Groton, Connecticut 06340
| | - Jotham W. Coe
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, and Pfizer Global Research and Development, Groton Laboratories, Pfizer, Inc., Groton, Connecticut 06340
| | - David B. Collum
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, and Pfizer Global Research and Development, Groton Laboratories, Pfizer, Inc., Groton, Connecticut 06340
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García F, McPartlin M, Morey JV, Nobuto D, Kondo Y, Naka H, Uchiyama M, Wheatley AEH. Suppressing the Anionic Fries Rearrangement of Aryl Dialkylcarbamates; the Isolation of a Crystallineortho-Deprotonated Carbamate. European J Org Chem 2008. [DOI: 10.1002/ejoc.200701096] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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53
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García-Álvarez J, Graham DV, Hevia E, Kennedy AR, Mulvey RE. Synthesis and characterisation of new bimetallic alkali metal–magnesium mixed diisopropylamide-acetylides: structural variations in bimetallic lithium- and sodium-heteroleptic magnesiates. Dalton Trans 2008:1481-6. [DOI: 10.1039/b716215d] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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54
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Wu CJ, Lee SH, Yun H, Lee BY. Ortho Lithiation of Tetrahydroquinoline Derivatives and Its Use for the Facile Construction of Polymerization Catalysts. Organometallics 2007. [DOI: 10.1021/om7010084] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Chun Ji Wu
- Department of Molecular Science and Technology and Energy System Division, Ajou University, Suwon 443-749, Korea
| | - Sang Hoon Lee
- Department of Molecular Science and Technology and Energy System Division, Ajou University, Suwon 443-749, Korea
| | - Hoseop Yun
- Department of Molecular Science and Technology and Energy System Division, Ajou University, Suwon 443-749, Korea
| | - Bun Yeoul Lee
- Department of Molecular Science and Technology and Energy System Division, Ajou University, Suwon 443-749, Korea
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55
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Ma Y, Collum DB. Lithium diisopropylamide-mediated reactions of imines, unsaturated esters, epoxides, and aryl carbamates: influence of hexamethylphosphoramide and ethereal cosolvents on reaction mechanisms. J Am Chem Soc 2007; 129:14818-25. [PMID: 17985891 DOI: 10.1021/ja074554e] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Several reactions mediated by lithium diisopropylamide (LDA) with added hexamethylphosphoramide (HMPA) are described. The N-isopropylimine of cyclohexanone lithiates via an ensemble of monomer-based pathways. Conjugate addition of LDA/HMPA to an unsaturated ester proceeds via di- and tetra-HMPA-solvated dimers. Deprotonation of norbornene epoxide by LDA/HMPA proceeds via an intermediate metalated epoxide as a mixed dimer with LDA. Ortholithiation of an aryl carbamate proceeds via a mono-HMPA-solvated monomer-based pathway. Dependencies on THF and other ethereal cosolvents suggest that secondary-shell solvation effects are important in some instances. The origins of the inordinate mechanistic complexity are discussed.
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Affiliation(s)
- Yun Ma
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, USA
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56
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Godenschwager PF, Collum DB. Lithium Hexamethyldisilazide-Mediated Enolizations: Influence of Chelating Ligands and Hydrocarbon Cosolvents on the Rates and Mechanisms. J Am Chem Soc 2007; 129:12023-31. [PMID: 17850084 DOI: 10.1021/ja074018m] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Enolizations of 2-methylcyclohexanone by lithium hexamethyldisilazide (LiHMDS) in the presence of three chelating ligands--trans-N,N,N',N'-tetramethylcyclohexanediamine, N,N,N',N'-tetramethylethylenediamine, and dimethoxyethane--reveal an approximate 40-fold range of rates. NMR spectroscopic analyses and rate studies reveal isostructural transition structures based on monomeric LiHMDS for the diamines. Rate studies of LiHMDS/dimethoxyethane-mediated enolizations implicate a substantial number of monomer- and dimer-based mechanisms. The rate laws vary for the three ligands because of ligand-dependent structural differences in both the reactants and the transition structures. The importance of LiHMDS-ketone complexes and the role of hydrocarbon cosolvents are discussed.
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Affiliation(s)
- Peter F Godenschwager
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University Ithaca, New York 14853-1301, USA
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Collum DB, McNeil AJ, Ramirez A. Lithium diisopropylamide: solution kinetics and implications for organic synthesis. Angew Chem Int Ed Engl 2007; 46:3002-17. [PMID: 17387670 DOI: 10.1002/anie.200603038] [Citation(s) in RCA: 169] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Lithium diisopropylamide (LDA) is a prominent reagent used in organic synthesis. In this Review, rate studies of LDA-mediated reactions are placed in the broader context of organic synthesis in three distinct segments. The first section provides a tutorial on solution kinetics, emphasizing the characteristic rate behavior caused by dominant solvation and aggregation effects. The second section summarizes substrate- and solvent-dependent mechanisms that reveal basic principles of solvation and aggregation. The final section suggests how an understanding of mechanism might be combined with empirical methods to optimize yields, rates, and selectivities of organolithium reactions and applied to organic synthesis.
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Affiliation(s)
- David B Collum
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, NY 14853-1301, USA.
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