Synthesis of Pyrazolidinone-Fused Benzotriazines through C–H/N–H Bond Functionalization of 1-Phenylpyrazolidinones with Oxadiazolones

Abstract

Presented herein is an efficient synthesis of pyrazolidinone-fused benzotriazines through the cascade reaction of 1-phenylpyrazolidinones with oxadiazolones. The formation of the title products is initiated by Rh(III)-catalyzed C–H/N–H bond metallation of 1-phenylpyrazolidinone and subsequent coordination with oxadiazolone followed by migratory insertion along with CO2 liberation, proto-demetallation, and intramolecular condensation. To our knowledge, this is the first synthesis of pyrazolidinone-fused benzotriazines based on the C–H bond activation strategy by using oxadiazolone as an easy-to-handle amidine surrogate. In general, this new protocol has advantages such as valuable products, easily accessible substrates, redox neutral conditions, concise synthetic procedure, high efficiency, and compatibility with diverse functional groups. Moreover, the usefulness of this method is further showcased by scale-up synthetic scenario and suitability to substrates derived from natural products such as thymol and nerol.

Synthesis of structurally diverse pyrazolo[1,2-a]pyrazolones based on the selective C–H bond alkenylation–annulation of 1-arylpyrazolidinones with allenyl acetates

“…Inspired by the above-described pioneering studies and as a continuation of our research interest in CHA-initiated cascade reactions, 9,10 especially by using allene derivatives as effective CPs, 8 i we conceived a reaction between 1-arylpyrazolidinones and allenyl acetates with the aim of developing alternative approaches towards fused N -heterocyclic compounds. Herein, we would like to report the results obtained in this regard.…”