Secondary Amine-Mediated Domino Reaction for the Synthesis of Substituted Quinolines from Dicyanoalkenes and Enynals.

Substituted quinolines, tricyclic and tetracyclic molecules with a quinoline moiety are synthesized by a domino reaction from dicyanoalkenes and 3-aryl-pent-2-en-4-ynals in one pot. We established two methods: one is catalyzed by chiral diphenylprolinol silyl ether, and the other is catalyzed by di(2-ethyl)hexylamine, in combination with p-nitrophenol. A wide variety of dicyanoalkenes can be employed. As the catalysts are secondary amines, and water is the only by-product, this is an environmentally benign synthetic method for the preparation of substituted quinolines.