Reaction of arylboronreagents, arylboronic acids or arylborates, which are readily accessible by lithiation of aryl bromides followed by treatment with trimethoxyborane, with α,β-unsaturated esters in the presence of rhodium/(S)-binap catalyst proceeded with high enantioselectivity to give high yields of optically active β-aryl esters of up to 98% ee. The enantioselectivity depends on the steric bulkiness
A highlyenantioselective 1,4-addition of aryltrialkoxysilanes to α,β-unsaturated esters and amides was successfully catalyzed by a chiral rhodiumcomplex generated from [Rh(cod)(MeCN)2]BF4 and (S)-BINAP.
Applications of 4,4‘-(Me<sub>3</sub>Si)<sub>2</sub>-BINAP in Transition-Metal-Catalyzed Asymmetric Carbon−Carbon Bond-Forming Reactions
作者:Masamichi Ogasawara、Helen L. Ngo、Takeshi Sakamoto、Tamotsu Takahashi、Wenbin Lin
DOI:10.1021/ol050834s
日期:2005.7.1
A recently developed BINAP derivative with trimethylsilyl substituents on the 4- and 4 '-positions of the binaphthyl skeleton, 2,2 '-bis-(diphenylphosphino)-4,4 '-bis(trimethylsilyl)-1,1 '-binaphthyl (tms-BINAP), was used in a variety of transition-metal-catalyzed asymmetric carbon-carbon bond-forming reactions. In pi-allylpalladium-mediated reactions, tms-BINAP gave better enantioselectivity than the unsubstituted BINAP, and the origin of the improved enantioselectivity was gained from an X-ray structural study of [Pd(eta(3)-C3H5)((R)-tms-BINAP)]CIO4.