Electron-Deficient 3-Cyano-1-(p-toluenesulfonyl)-1,3-butadienes: Regio- and Stereoselective Synthesis of a Benzene Ring System by Michael-Type Addition-Cyclization with Enamines
benzonitriles is achieved via amino-catalyzed [3+3] benzannulation of α,β-unsaturated aldehydes and 4-arylsulfonyl-2-butenenitriles. Using pyrrolidine as an organocatalyst via iminium activation, a series of substituted benzonitriles were obtained in good to high yields in a regioselective manner. This reaction can proceed smoothly under mild reaction conditions and without the aid of any metals, additional