作者:Clayton H. Heathcock、Michael C. Pirrung、Stephen H. Montgomery、John Lampe
DOI:10.1016/s0040-4020(01)93284-3
日期:——
Li enolates of hindered aryl esters condense with aldehydes to give predominantly threo aldols. The method has been explored with esters 3 (DMP propionate), 4 (BHT propionate), and 5 (DBHA propionate). DMP propionate reacts with benzaldehyde and α-unbranched aliphatic aldehydes to give threo:erythro ratios of about 6.5:1. However, with α-branched aliphatic aldehydes, ester 3 gives only threo-aldols.
Attainment of syn-selectivity for boron-mediated asymmetric aldol reactions of carboxylic esters
作者:Ji-Feng Liu、Atsushi Abiko、Zhonghua Pei、Dana C Buske、Satoru Masamune
DOI:10.1016/s0040-4039(98)00123-3
日期:1998.4
reagent for syn-selective aldolreactions has been developed based on the recent finding that the stereochemistry of the boron-mediatedaldolreaction of a carboxylic ester is controlled by the bulkiness of the alcohol moiety of the ester, by the proper choice of reagents, and by the enolization conditions. This readily available, inexpensive reagent has been utilized in studies directed towards the synthesis
[reaction: see text]Comprehensive analysis of the enolization of alpha-silyloxyketones by Chx2BCl/R3N has allowed us to design stereoselective Chx2BCl-mediated aldol processes that afford syn or anti aldol products and to disclose a hypothesis that accounts for the subtle effects that determine their enolization.
Chiral propionate enolate equivalents for the stereoselective synthesis of threo- or erytho-α,-methyl-β-hydroxy acids
作者:Stephen G. Davies、Isabelle M. Dordor-Hedgecock、Peter Warner
DOI:10.1016/s0040-4039(00)94797-x
日期:——
derived from (η5-C5H5)Fe(CO)(PPh3)COCH2CH3 are chiral propionate enolate equivalents which on reaction with aldehydes (RCHO, RMe.Et,iPr,tBu) provide stereoselective syntheses of threo- and erytho-α-methyl-β-hydroxy acids respectively.