Catalysis of Mukaiyama Aldol Reactions by a Tricyclic AluminumAlkoxide Lewis Acid

摘要

The Mukayiama aldol reaction of aldehydes is efficiently accomplished with a low concentration ofthe dimeric alumatrane catalyst 2 at mild or subambient temperatures. Our protocol tolerates a widevariety of electron-rich, neutral, and deficient aryl, alkyl, and heterocyclic aldehydes. A wide varietyof enol silyl ethers are also tolerated. An intermediate that was isolated provides mechanisticinformation regarding the role of dimeric 2 in the Mukaiyama aldol reaction. Experimental evidenceis presented for the stronger Lewis acidity of 5 compared with F_3B.