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. The direct organocatalytic desymmetrization was demonstrated for 4-substituted cyclohexanones by treatment with a vinyl sulfone in CHCl ₃. The desired Michael adducts were obtained in high chemical yields and stereoselectivities (up to 97 % yield, 93 % ee). Enantiomeric products were obtained by using either a camphor-derived pyrrolidine or a cinchonidine-derived primary amine as a catalyst.