Showing papers by "Hiroaki Sasai published in 1999"

Direct Catalytic Asymmetric Aldol Reaction

Abstract: The direct catalytic asymmetric aldol reaction using aldehydes and unmodified ketones is described for the first time herein. This reaction was first found to be promoted by 20 mol % of anhydrous (R)-LLB (L = lanthanum, L = lithium, B = (R)-binaphthol moiety) at −20 °C, giving a variety of aldol products in ee's ranging from 44 to 94%. This asymmetric reaction has been greatly improved by developing a new heteropolymetallic asymmetric catalyst [(R)-LLB, KOH, and H2O]. Using 3−8 mol % of this catalyst, a variety of direct catalytic asymmetric aldol reactions were again found to proceed smoothly, affording aldol products in ee's ranging from 30 to 93% and in good to excellent yields. Interestingly, the use of this new heteropolymetallic asymmetric catalyst has realized a diastereoselective and enantioselective aldol reaction using cyclopentanone for the first time. It is also noteworthy that a variety of aldehydes, including hexanal, can be utilized for the current direct catalytic asymmetric aldol reaction...