Copper‐Catalyzed [4+2] Cycloaddition Using N‐(2‐Pyridyl)ketimines and Terminal Alkynes

Abstract Copper‐catalyzed [4+2] cycloaddition of N‐(2‐pyridyl)ketimines and terminal alkynes has been achieved. Ketimines bearing a trifluoromethyl group reacted with various terminal alkynes to produce pyrido[1,2‐a]pyrimidines in good to high yields. This reaction proceeded through a propargylamine intermediate and the corresponding product was obtained via 6‐endo‐dig cyclization. magnified image