Rhodium-catalyzed asymmetric 1,4-addition of arylboron reagents to alpha,beta-unsaturated esters

Reaction of arylboron reagents, arylboronic acids or arylborates, which are readily accessible by lithiation of aryl bromides followed by treatment wi th trimethoxyborane, with alpha,beta-unsaturated esters in the presence of rhodium/(S)-binap catalyst proceeded with high enantioselectivity to give h igh yields of optically active beta-aryl esters of up to 98% ee. The enanti oselectivity depends on the steric bulkiness of the ester moiety. (C) 1999 Elsevier Science Ltd. All rights reserved.