Enantioselective Rauhut−Currier Reactions Promoted by Protected Cysteine

We report highly enantioselective examples of the Rauhut−Currier cycloisomerization reaction (the “vinylogous Morita−Baylis−Hillman reaction”). The reaction is highly practical and is catalyzed by a commercially available derivative of the proteinogenic amino acid cysteine. Reactions are conducted in the presence of potassium tert-butoxide and a critical concentration of water in bulk acetonitrile. A mechanistic model is advanced that may account for reaction selectivity that is predicated on organizational chelation of K ion in the product-determining step in which the Cys derivative undergoes elimination.