Homolytic reactions of ligated boranes. Part 18. The scope of enantioselective hydrogen-atom abstraction by chiral amine–boryl radicals for kinetic resolution under conditions of polarity reversal catalysis
作者:Hai-Shan Dang、Valérie Diart、Brian P. Roberts
DOI:10.1039/p19940001033
日期:——
carbonyl-containing compounds. The key step involves enantioselective abstraction of hydrogen from a C–H bond α to the carbonyl function by optically active amine–boryl radicals derived from the catalyst by hydrogen-atom transfer to tert-butoxyl radicals generated by photolysis of di-tert-butyl peroxide. Chiral discrimination is generally not large, although enantioselectivity factors up to 8.8 were obtained at
B-iso-2-(2-diethylaminoethyl)apopinocampheyl-9-borabicyclo-[3.3.1]nonyl hydride — An improved chiral reducing agent for straight chain aliphatic ketones
作者:Steven A. Weissman、P. Veeraraghavan Ramachandran
DOI:10.1016/0040-4039(96)00691-0
日期:1996.5
A series of chirally modified borohydrides of the type lithium B-iso-2-(alkyl)apopinocampheyl-9-borabicyclo[3.3.1]nonylhydride (2–4 and 8–9) were prepared to enable a strategic development of chiral reagents for the reduction of straight chain aliphatic ketones. Reagent 8 (alkyl = 2-diethylaminoethyl) reduces 2-octanone in 82% ee, significantly higher than that obtained with NB-Enantride (7) under