Heteroatom-directed lithiations of chiral alkyl carbamates: A powerful tool for enantioselective synthesis

Hoppe, Dieter; Ahrens, Hartmut; Guarnieri, W.; Helmke, Hendrik; Kolczewski, Sabine

doi:10.1351/pac199668030613

Cited by 20 publications

(6 citation statements)

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“…Stable structures of organolithium compounds are well-established as highly aggregated and strongly ligandassociated. [8,9,[29][30][31][32][33] The origin of the stabilization can be attributed to a favorable binding energy between the relatively concentrated positive charge of the small lithium atom and the negative charge of the carbanion or the electron pair of a Lewis base in intermolecular and/or intramolecular interactions. Support for lithium-electron pair complexation in ground states was provided by X-ray crystallographic structures.…”

Section: Methodsmentioning

confidence: 99%

Beyond Thermodynamic Acidity: A Perspective on the Complex‐Induced Proximity Effect (CIPE) in Deprotonation Reactions

et al. 2004

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The concept of the complex-induced proximity effect (CIPE) in deprotonations is helpful in elucidating the mechanisms involved in carbanion chemistry and in planning organic syntheses. In this Review, the consequences of complexation of organolithium bases to functional groups of the substrates before the proton-transfer step are discussed. Experimental data from kinetic measurements and isotope-labeling experiments as well as the results of calculations in many cases point to a prelithiation complex as a reaction intermediate. Some examples from natural products synthesis illustrate how this concept can be used to obtain intermediates in a regio- or stereoselective manner. Of particular interest is the functionalization of positions that are remote from the coordination group.

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Section: Methodsmentioning

confidence: 99%

Beyond Thermodynamic Acidity: A Perspective on the Complex‐Induced Proximity Effect (CIPE) in Deprotonation Reactions

et al. 2004

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“…Previous studies of the deprotonation of alkyl carbamates with n BuLi/(−)‐sparteine have established a strong preference for the abstraction of the pro‐ S proton followed by electrophilic substitution with retention of configuration 65. Thus, deprotonation of 57 is presumed to initially generate an S ‐configured organolithium compound, which epimerizes over time to the R complex, unless TMSCl is present.…”

Section: Chiral Organolithium Reagentsmentioning

confidence: 99%

Configurational Stability and Transfer of Stereochemical Information in the Reactions of Enantioenriched Organolithium Reagents

Basu

Thayumanavan

2002

Angew. Chem. Int. Ed.

233

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The conversion of a prochiral methylene group into a stereogenic center by means of a lithiation/substitution sequence has emerged as a powerful synthetic transformation over the past 15 years. This reaction proceeds via a chiral organolithium intermediate, and the stereochemical fidelity of the overall reaction sequence is intimately dependent on the stereochemical behavior of the chiral organolithium as well as on the rate and stereochemical sense of the electrophilic substitution step. Chiral organolithium reagents were first reported by Letsinger, Curtin, and Applequist half a century ago. The lithiated intermediates in these early studies were not highly configurationally stable, and applications in stereoselective synthesis were not immediately forthcoming. The two decades that followed the 1980 report by Still and Sreekumar of a configurationally stable α‐oxyorganolithium were marked by an increased interest in these reagents. As the synthetic applications of chiral organolithium reagents have grown, so have accompanying mechanistic studies of these intermediates which serve as the basis for this review.

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“…The potassium ion is proposed to be coordinated by ligand 19 as well as the diketonate derived from 5a. 88 4 Michael Reactions The lupine alkaloid (-)-sparteine 22 was proved to be a powerful chiral additive for lithium-carbanionic chemistry [32]. Beak et al reported the conversion of benzylamines 21, deprotonated by nBuLi/(-)-sparteine, with dinitriles 23 (Scheme 4.10) [33].…”

Section: Miscellaneous Examplesmentioning

confidence: 99%

Michael Reactions and Conjugate Additions

Baro

Christoffers

2005

Quaternary Stereocenters

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Heteroatom-directed lithiations of chiral alkyl carbamates: A powerful tool for enantioselective synthesis

Abstract: Abstract

Cited by 20 publications

References 0 publications

Beyond Thermodynamic Acidity: A Perspective on the Complex‐Induced Proximity Effect (CIPE) in Deprotonation Reactions

Beyond Thermodynamic Acidity: A Perspective on the Complex‐Induced Proximity Effect (CIPE) in Deprotonation Reactions

Configurational Stability and Transfer of Stereochemical Information in the Reactions of Enantioenriched Organolithium Reagents

Michael Reactions and Conjugate Additions

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