Phosphine-Catalyzed (4 + 2) Annulation of δ-Sulfonamido-Substituted Enones with 1,1-Dicyanoalkenes: Synthesis of Piperidine Derivatives

The δ-sulfonamido-substituted enones were employed as phosphine acceptor in phosphine-catalyzed (4 + 2) annulation of 1,1-dicyanoalkenes. They served as a four-membered synthon to react with 1,1-dicyanoalkenes under mild reaction conditions, producing piperidine derivatives in moderate to excellent yields with good to excellent diastereoselectivities.