Regioselective Synthesis of 1,2-and 1,4-Dihydroquinolines by Palladium-Catalyzed Intramolecular N-Arylation

A series of 1,2- and 1,4-dihydroquinolines has been successfully prepared. The Pd-catalyzed intramolecular N-arylation of Z-enamines, formally prepared by the Horner-Wadsworth-Emmons olefination, proceeded efficiently to furnish the cyclized products. Depending on the cyclization conditions, substituted 1,4-dihydroquinolines and further isomerized 1,2-dihydroquinolines were independently obtained in high yields with an excellent control of isomerization of the double bond.