Preparation of New Chiral Building Blocks by a Mukaiyama–Michael Reaction of 2-(Phenylsulfonyl)cyclopent-2-en-1-one

Abstract

Highly enantio- and diastereoselective Mukaiyama-Michael reaction of 2-(phenylsulfonyl)cyclopent-2-en-1-one using enol silane of t-butyl thiopropionate is described. The product is formed in 87% yield with dr ratio of 27:1 and 91% ee under the stoichiometric conditions, and the yield, dr ratio, and ee were 89%, 49:1, and 88% ee, respectively, under the catalytic conditions. A highly stereoselective epimerization of the product of the Mukaiyama–Michael reaction which proceeds in 77% yield with dr ratio of 22:1 is described, too. Since both enantiomers of the ligand for this Mukaiyama-Michael reaction are available, a method for the synthesis of all four stereoisomers of the product as useful chiral building blocks has been established.