The reactions of 4‐dicyanomethylene‐2‐phenyl‐4H‐1‐benzopyran and some benzologs with nucleophiles

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Abstract
4‐Dicyanomethylene‐2‐phenyl‐4H‐1‐benzopyran (1) reacts with primary amines under mild conditions to give 4‐imino‐3‐alkyl‐5‐alkylimino‐2‐phenyl‐3,4‐dihydro‐5H‐[1]benzopyrano[3,4‐c]‐pyridine derivatives which, in turn, are hydrolyzed with acid to 4‐imino‐3‐alkyl‐2‐phenyl‐3,4‐dihydro‐5H‐[1]benzopyrano[3,4‐c]pyridin‐5‐ones. When more vigorous conditions are employed for the reactions of 1 with primary amines, Dimroth rearrangements take place and the products are derivatives of 4‐alkyl‐ (or aryl)amino‐5‐alkyl‐ (or aryl)imino‐2‐phenyl‐5H‐[1]benzopyrano‐[3,4‐c]pyridine. The latter compounds are hydrolyzed by acid to the corresponding 5‐pyridone derivatives. The reaction of 1 with piperidine gives 2‐phenyl‐4‐piperidyl‐5H‐[1]benzopyrano‐[3,4‐c]pyridin‐5‐one. Sodium methoxide reacts with 1 to give 3‐cyano‐2‐methoxy‐4‐(2‐hydroxyphenyl)‐6‐phenylpyridine. Two benzologs of 1 have been allowed to react with primary and secondary amines and the products are analogous to those obtained from 1.