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

The 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.