Enantioselective Seleno-Michael Addition Reactions Catalyzed by a Chiral Bifunctional N-Heterocyclic Carbene with Noncovalent Activation.

The Michael reaction is a conjugate addition and is one of the most powerful methods with which to prepare functional molecules with a β-stereogenic center. Despite its success in the formation of various asymmetric carbon-carbon and carbon-heteroatom bonds, enantioselective seleno-Michael addition remains essentially unexplored. We report here a highly enantioselective Michael addition reaction of alkyl selenols to enones. This method conveniently introduces a Se atom to an electron-deficient double bond asymmetrically. A chiral bifunctional N-heterocyclic carbene (NHC)/thiourea catalyst was developed as a key ingredient that delivers chiral β-seleno ketones with remarkable selectivity. This new catalyst and its mode of action support broad applications in the catalytic activation of nucleophilic reactions.