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

A novel copper-catalyzed [5 + 1] annulation of 2-ethynylanilines with an <i>N</i>,<i>O</i>-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 CuBr₂ and trifluoroacetic acid (TFA) promoting [5 + 1] annulation of the 2-ethynylaniline with ethyl glyoxylate is also demonstrated