Mukaiyama Aldol Reactions Catalyzed by a Trimeric Organo Aluminum(III) Alkoxide

Abstract

Mukaiyama aldol reactions of enol ethers with a variety of aldehydes and ketones are efficiently catalyzed at 0–25 °C by the sterically bulky trimeric organo aluminum(III) alkoxide 1 synthesized via the reaction of 3 equiv of AlMe3 with tripodal tris(2-hydroxy-3-tert-butyl-5-methylphenyl) methane and the elimination of 3 equiv of methane. Comparisons of its catalytic properties with the less sterically hindered analogue 2, the more sterically hindered analogue 3, a monomeric aluminum near-analogue 4, and a dimeric alumatrane 5 revealed that 1 possesses superior activity.