SuperQuat 5,5-dimethyl-4-iso-propyloxazolidin-2-one as a mimic of Evans 4-tert-butyloxazolidin-2-one
作者:Steven D. Bull、Stephen G. Davies、A. Christopher Garner、Dennis Kruchinin、Min-Suk Key、Paul M. Roberts、Edward D. Savory、Andrew D. Smith、James E. Thomson
DOI:10.1039/b605244d
日期:——
The incorporation of a gem-dimethyl group at the 5-position of a chiral oxazolidinone biases the conformation of the adjacent C(4)-stereodirecting group such that the gem-dimethyl-4-iso-propyl combination mimics a C(4)-tert-butyl group, providing higher levels of stereocontrol than a simple 4-iso-propyloxazolidinone. The generality of this principle is demonstrated with applications in stereoselective enolate alkylations, kinetic resolutions, Diels–Alder cycloadditions and Pd-catalysed asymmetric acetalisation reactions.
Transesterification of N-acyloxazolidinones with alcohol by lanthanum(III) Iodide
作者:Shin-ichi Fukuzawa、Yuki Hongo
DOI:10.1016/s0040-4039(98)00521-8
日期:1998.5
Transesterification of N-acyloxazolidinones by treatment with an alcohol and lanthanum(III) iodide gives the corresponding esters in good to excellent yields under mild conditions with negligible racemization. (C) 1998 Elsevier Science Ltd. All rights reserved.
Electrogenerated Base-Induced N-Acylation of Chiral Oxazolidin-2-ones
Studies directed toward the design of chiral acylating agents. The utility of chiral N-benzoylimides in enantioselective alcohol acylation
作者:David A. Evans、James C. Anderson、Marta K. Taylor
DOI:10.1016/s0040-4039(00)73882-2
日期:1993.8
N-benzoyl-4(S)-tert-butyl-2-oxazolidinone (1b) is found to be an efficient enantioselective acylating agent for aryl n-alkyl carbinols. Selective benzoylation of racemic aryl n-alkyl carbinols with kinetic selectivities of 20-30:1 for the (R) enantiomer is observed. The acylation process is promoted by formation of the derived magnesium alkoxides which may be accessed either from alcohol deprotonation with MeMgBr or through deprotonation with the Lewis acid-base combination of MgBr2/R3N.
A simple method removing 2-oxazolidinone and 2-hydroxyethylamine auxiliaries in methoxide–carbonate systems for synthesis of planar-chiral nicotinate
A facile and practical removal of 2-oxazolidinone and 2-hydroxyethylamine auxiliaries was accomplished by treating the corresponding N-acyl-2-oxazolidin one and N-(2-hydroxyethyl)amide derivatives in simple methoxide-carbonate systems. The presence of excess DMC (dimethyl carbonate) accelerates the N-acyl bond cleavage for those substrates under mild reaction conditions, and the present method was found to be useful especially for the synthesis of planar-chiral nicotinate. (C) 2003 Elsevier Science Ltd. All rights reserved.