Selective access to dipyrazolo-fused pyridines via formal [3 + 2 + 1] heteroannulation of methyl ketones with pyrazol-5-amines

Abstract

A fascinating new form of the Hantzsch reaction with methyl ketones and pyrazol-5-amines for the selective synthesis of dipyrazolo-fused pyridines has been discovered. This special [3 + 2 + 1] heteroannulation was accomplished via the domino generation of two C–C bonds and one C–N bond. Preliminary mechanistic studies indicated that the I₂/DMSO system realized the oxidative carbonylation of Csp³–H of methyl ketones, while Cu(OTf)₂ acted as a relay reagent to accelerate this transformation.