Synthesis of pyrazolo‐fused heterocycles by a tandem appel's dehydration/electrocyclization methodology

The hydrazones of benzophenone, benzil, and acetophenone were allowed to react with acetoacetanilide to give azinoamides 18 , and the reaction of 18 with Appel's dehydrathon contiditons (triphenylphosphine/carbon tetra‐chloride/triethylatnine) led to the corresponding azinoketimines 19 , which underwent elctrocyclic ring closure under the reaction conditions to give pyrazolo‐fused heterocycles. Azinoamide 18a gave a 4,9‐dihydropyazolo‐[5,1‐ b ]quinazoine 21 , while 18b yielded 2,3‐dihydro‐1 H ‐imidazo[1,2‐ b ]pyrazol‐2‐one 26 and 1 H ‐imidazo[1,2‐ b ]‐pyrazole 29 . Compound 18c gave a monocyclic N ‐α‐styryl‐5‐(phenylamino)pyrazole 32 .