Chiral spiroborate esters catalyzed highly enantioselective direct aldol reaction

Asymmetric catalysis of chiral spiroborate esters with an O3BN framework toward the direct aldol reaction of acetone and aromatic aldehydes was examined, and a new, efficient chiral catalyst was discovered. In the presence of the novel catalyst, acetone was allowed to react with aromatic aldehydes at 0 degrees C for 50 h to afford chiral beta-hydroxyketone in up to > 99% ee and 92% yield. The catalyst, which is readily synthesized, is highly stable to hydrolysis, thermolysis, oxidation, and racemization, can be conveniently recovered. (c) 2006 Elsevier Ltd. All rights reserved.