Synthesis of 4H-Indazol-4-ones and Fused Pyrazoles via Copper-Catalyzed Annulation of Hydrazones with Cyclic Enones

Abstract

Herein, we report the synthesis of cyclic ketone-fused pyrazoles via [3+2] annulation reaction between hydrazones and cyclic enones (five-, six- and seven-membered) catalyzed by Cu(II) under aerobic conditions. These compounds were further functionalized by reactions such as Suzuki-Miyaura cross-coupling, Heck coupling, and Aldol reaction to afford diverse molecular scaffolds in good yield, selectivity and functional group tolerance.