Kinetic resolution of 2,2-difluoro-3-hydroxy-3-aryl-propionates catalyzed by organocatalyst (R)-benzotetramisole
作者:Hui Zhou、Qing Xu、Peiran Chen
DOI:10.1016/j.tet.2008.04.055
日期:2008.6
Kinetic resolution of a series of ethyl 2,2-difluoro-3-hydroxy-3-aryl-propionates catalyzed by (R)-benzotetramisole has been performed. It was found that when the aryl group was phenyl or phenyl substituted with electron-donating group (such as -Me, -OMe, and -SMe) or naphthyl groups, the enantio-selectivity factor (s) could reach 20 or higher; electron-withdrawing (such as fluorine) substitution on the benzene ring dramatically lowers the s value. Kinetic resolution in preparative scale for some of the substrates demonstrated the applicability of this method. (c) 2008 Elsevier Ltd. All rights reserved.
Rhodium-catalyzed Reformatsky-type reaction of ethyl bromodifluoroacetate
Treatment of a variety of carbonyl compounds with ethyl bromodifluoroacetate and Et2Zn in the presence of RhCl(PPh3)(3) in CH3CN afforded Reformatsky-type products in good to excellent yields in a mild reaction condition. This is a good method to obtain a beta-hydroxy-alpha,alpha-difluoro carboxylic acid ethyl ester and especially to improve the poor reactivity of ketones. (C) 2004 Elsevier Ltd. All rights reserved.
LINDERMAN, RUSSELL J.;GRAVES, DAVID M., J. ORG. CHEM., 54,(1989) N, C. 661-668