SYNTHESIS OF PYRAZOLO-FUSED HETEROCYCLES BY A TANDEM APPEL DEHYDRATION/ELECTROCYCLIZATION METHODOLOGY

摘要

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 tetrachloride/triethylamine) 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-1H-imidazo[1,2-b]pyrazol-2-one 26 and 1H-imidazo[1,2-b]pyrazole 29. Compound 18c gave a monocyclic N-alpha-styryl-5-(phenylamino)pyrazole 32. [References: 24]