Access to pyrrolo-pyridines by gold-catalyzed hydroarylation of pyrroles tethered to terminal alkynes

Abstract

In a simple procedure, the intramolecular hydroarylation of N-propargyl-pyrrole-2-carboxamides was accomplished with the aid of gold(III) catalysis. The reaction led to differently substituted pyrrolo[2,3-c]pyridine and pyrrolo[3,2-c]pyridine derivatives arising either from direct cyclization or from a formal rearrangement of the carboxamide group. Terminal alkynes are essential to achieve bicyclic pyrrolo-fused pyridinones by a 6-exo-dig process, while the presence of a phenyl group at the C-C triple bond promotes the 7-endo-dig cyclization giving pyrrolo-azepines.

Keywords: C–C coupling; gold catalysis; homogeneous catalysis; nitrogen heterocycles; rearrangement.

Scheme 1

Pd-catalyzed cyclization of N-allyl-pyrrole-2-carboxamides.

Figure 1

Significant relationships among hydrogen and carbon atoms arising from 2D-NMR studies to determine the pyrrolo-pyridinones.

Scheme 2

Proposed mechanism for the formation of the six-membered products.