已开发出一种简单有效的方法,使用支持的试剂系统CuBr 2 / Al 2 O 3 -Na 2 CO 3 / Al 2 O 3在一个锅中由β-酮酸酯和二酮合成α-溴酸酯和酮,其中β-酮酸酯首先与CuBr 2 / Al 2 O 3反应,产物α-溴-β-酮酸酯与Na 2 CO 3 / Al 2 O 3反应以高产率得到最终产物α-溴酸酯。
The first cobalt-catalyzed asymmetric Kumada cross-coupling with high enantioselectivity has been developed. The reaction affords a unique strategy for the enantioselective arylation of α-bromo esters catalyzed by a cobalt-bisoxazoline complex. A variety of chiral α-arylalkanoic esters were prepared in excellent enantioselectivity and yield (up to 97% ee and 96% yield). The arylated products were transformed
Four new cyclopropane-based bisoxazolines were synthesized and applied to cobalt-catalyzed cross-coupling reactions between racemic alpha-bromo esters and aryl Grignard reagents. The reaction afforded a series of chiral alpha-arylalkanoic esters with high yields and good enantioselectivities (up to 93% yield, 92:8 er). This research focuses on the cross-coupling between racemic alpha-bromopropanoate and p-isobutylphenyl Grignard reagent's which provides ibuprofen ester efficiently. Furthermore, ibuprofen ester 7e was transformed into (S) -ibuprofen (99:1 er) via hydrolysis and recrystallization. (C) 2016 Elsevier Ltd. All rights reserved.
Efficient .alpha.-halogenation of acyl chlorides by N-bromosuccinimide, N-chlorosuccinimide, and molecular iodine
作者:David N. Harpp、L. Q. Bao、Catherine J. Black、John G. Gleason、Roger A. Smith