Copper‐Catalyzed Aerobic Oxidative Cyclization of Hydrazones to Pyrazolidinones

Abstract

N‐Aryl hydrazones participate, under copper catalysis, in a [3+2] cycloaddition/aerobic oxidation cascade reaction to form pyrazolidinones. The starting hydrazones were prepared by three‐component coupling of allylic amines, acyl chlorides, and aryl diazonium salts.

Aerobic Copper-Catalyzed Organic Reactions

“…1125 Treatment of hydrazono amides to oxidative conditions resulted in a cycloaddition and subsequent oxidation, giving the pyrazolidinone products in moderate to good yield (Scheme 591). The amide nitrogen can support either allyl or methyl groups, while the hydrazone aryl is limited to ortho -xylenyl and para -chloro phenyl rings.…”

“…Grimaud and co-workers reported a tandem cyclization–oxidation of hydrazones to pyrazolidinones . Treatment of hydrazono amides to oxidative conditions resulted in a cycloaddition and subsequent oxidation, giving the pyrazolidinone products in moderate to good yield (Scheme ).…”

Ugi post-condensation copper-triggered oxidative cascade towards pyrazoles

“…We recently reported a new synthesis of fused pyrazolidinone under oxidative conditions from simple hydrazone derivatives ( Scheme 1 ) [ 13 ]. The cascade features a [3 + 2] cycloaddition coupled with an aerobic oxidation of the resulting pyrazolidine.…”