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 C1 part, leading to the preparation of quinoline derivatives with an ester substituent on the 2-position is described. A combination of CuBr(2) and trifluoroacetic acid (TFA) promoting [5 + 1] annulation of the 2-ethynylaniline with ethyl glyoxylate is also demonstrated.