Synthesis of Pyrroloindoles and Dipyrrolo-pyridines by a Hydroamination Route

Significance

A previously reported synthesis of 2-(aminomethyl)indoles via a copper-catalyzed three-component reaction of 2-ethynylaniline, paraformaldehyde, and a secondary amine followed by heteroannulation (H. Ohno et al. Angew. Chem. Int. Ed. 2007, 46, 2295) serves as the basis of the synthetic work reported herein. Thus, treatment of a double ortho-ethynyl aryldiamine 1 with formaldehyde and a secondary amine under copper catalysis leads to mono- or dimethylene amino pyrroloindoles 2 and 3, respectively. Under similar conditions the pyridine analogue 4 leads to the pyrrolopyridines 5 and 6, respectively.