RHODIUM-CATALYZED ASYMMETRIC 1,4-ADDITION OF 2-ALKENYL-1,3,2-BENZODIOXABOROLES TO ALPHA,BETA-UNSATURATED KETONES

Reaction of 2-alkenyl-1,3,2-benzodioxaboroles, which are readily acces sible by hydroboration of alkynes with catecholborane, with alpha,beta -unsaturated ketones in the presence of rhodium/(S)-binap catalyst and triethylamine in dioxane/H2O (10/1) proceeded with high enantioselect ivity at 100 degrees C to give high yields of optically active beta-al kenyl ketones of over 90% ee. One pot synthesis of the 1,4-addition pr oduct is also successful in the rhodium-catalyzed asymmetric reaction by use of alkenylboranes generated in situ from alkyne and catecholbor ane. (C) 1998 Elsevier Science Ltd. All rights reserved.