Pyridine and Quinoline Derivatives via Ru-Catalyzed Cyclization of Azadienynes

Significance

A mild and efficient two-step procedure for the synthesis of pyridine and quinoline derivatives from readily available N-vinyl or N-aryl amides is presented. The use of 2-chloropyridine as the base was found to be crucial for the conversion of starting amides (including sensitive N-vinyl amides) to the corresponding C-silyl alkynyl imines. The combination of SPhos and CpRu(PPh₃)₂Cl was found to be the optimal catalytic system for the desilylative cycloisomerization to give the pyridine and quinoline derivatives in good to excellent yields.