Studies on the synthesis of heterocyclic compounds. Part IV. Further investigation of the pschorr reaction with some pyrazole derivatives

Abstract Thermal decomposition of the diazonium sulfate derived from N‐methyl‐(1‐phenyl‐3‐methylpyrazol‐5‐yl)‐2‐aminobenzamide afforded products formulated as 1‐phenyl‐3‐methyl[2]benzopyrano[4,3‐c]pyrazol‐5‐one (yield 10%), 1,4‐dimethyl‐3‐phenylpyrazolo[3,4‐c]isoquinolin‐5‐one (yield 10%), N‐methyl‐(1‐phenyl‐3‐methylpyrazol‐5‐yl)‐2‐hydroxybenzamide (yield 8%) and 4′‐hydroxy‐2,3′‐dimethyl‐1′‐phenylspiro[isoindoline‐1,5′‐[2]‐pyrazolin]‐3‐one (yield 20%). Decomposition of the diazonium sulfate derived from N‐methyl‐(1,3‐diphenylpyrazol‐5‐yl)‐2‐aminobenzamide gave products formulated as 7,9‐dimethyldibenzo[e,g]pyrazolo[1,5‐a][1,3]‐diazocin‐10‐(9H)one (yield 8%), 4‐methyl‐1,3‐diphenylpyrazolo[3,4‐c]isoquinolin‐5‐one (yield 7%) and 4′‐hydroxy‐2‐methyl‐1′,3′‐diphenylspiro[isoindoline‐1,5′‐[2]pyrazolin]3‐one (yield 10%). The spiro compounds 6a,b underwent thermal and acid‐catalysed conversion into the hitherto unknown 2‐benzopyrano[4,3‐c]pyrazole ring system 7a,b in good yield. Analytical and spectral data are presented which supported the structures proposed.