Desymmetrization and Switching of Stereoselectivity in Direct Organocatalytic Michael Addition of Ketones to 1,1‐Bis(phenylsulfonyl)ethylene

Abstract

AbstractThe organocatalytic desymmetrization was demonstrated for 4‐substituted cyclohexanones by treatment with a vinyl sulfone in the presence of an organocatalyst. The desired Michael adducts were typically obtained in high chemical yields and high to excellent stereoselectivities (up to 97 % yield, 93 % ee). An efficient desymmetrization method was developed for the synthesis of enantiomeric products by using either camphor‐derived pyrrolidine V or cinchonidine‐derived primary amine VII as a catalyst. The absolute stereochemistry of the (2R,4R)‐2‐[2,2‐bis(phenylsulfonyl)ethyl]‐4‐methylcyclohexanone (3a) and (2R,4R)‐2‐[2,2‐bis(phenylsulfonyl)ethyl]‐4‐tert‐butylcyclohexanone (3b) was confirmed by single‐crystal X‐ray structure analyses.