Copper-Catalyzed [5+1] Annulation of 2-Ethynylanilines with an N,O-Acetal Leading to Construction of Quinoline Derivatives

A novel copper-catalyzed [5 + 1] annulation of 2-ethynylanilines with an N,O-acetal, which functioned as a Cl part, leading to the preparation of quinoline derivatives with an ester substituent on the 2-position is described. A combination of CuBr2 and trifluoroacetic acid (TFA) promoting [5 + 1] annulation of the 2-ethynylaniline with ethyl glyoxylate is also demonstrated.