Copper(I) halide-promoted formation of 3-acyl-5-halopyridine moiety from NH-2-(2-acylethynyl)pyrroles and propargylamine

摘要

Available NH-2-acylethynylpyrroles undergo annulation/aromatization with propargylamine in the presence of 1 equiv. of CuHal (Hal = Cl, Br, I) at 60-65 degrees C to afford 3-acyl-2-(pyrrol-2-yl)pyridines and their 5-halo analogues in 28-61 and 5-14% yields, respectively. The latter are assumed to be resulted from halohydrogenation of the intermediate Cu-pyrrolylpropargyl amino enones.