Synthesis of pyrano[3,4‐c]pyrazole and pyrazolo[3,4‐d][1,2]diazepine derivatives

Abstract

AbstractBy the action of thionyl chloride on 3(5)‐R‐4‐phenacylpyrazole‐5(3)‐carboxylic acid (3c,d), 3‐R‐5‐phenylpyrano[3,4‐c]pyrazole‐7‐(1H)ones (4c,d) were obtained. When 4c,d were treated with hydrazine hydrate followed by refluxing in ethanol containing acetic acid, 4,7‐dihydro‐3‐R‐5‐phenylpyrazolo[3,4‐d][1,2]‐diazepin‐8‐(1H)ones (6c,d) were formed. Compounds 6c,d, in turn, were refluxed in ethanol saturated with hydrochloric acid to yield 6‐amino‐1,6‐dihydro‐3‐R‐5‐phenyl‐7H‐pyrazolo[3,4‐c]pyridin‐7‐ones (7c,d). Compounds 7c,d could be obtained directly from 5c,d. The starting materials 3c,d were prepared by hydrolysis of the oxime of 3(5)‐R‐4‐phenacyl‐5(3)carboalcoxypyrazoles (1a,b). Structural assignments rested on correct elemental analysis, molecular weights determined by mass spectrometry, and spectroscopic evidence.