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

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.

Regioselective Synthesis of 2(1H)-Pyridinones from β-Aminoenones and Malononitrile. Reaction Mechanism

“…The average life of the intermediate 2 H -pyran-2-imine 6 must be very low. In the literature, we found described only those whose 2 H -pyran-2-imine rings are stable to nucleophilic attack because they are integrated in condensated polycyclic systems. ,− …”

Recyclisation of carbo- and heterocyclic compounds involving malononitrile and its derivatives

“…119 The benzopyran 149a reacts with primary amines under mild conditions giving rise to 4-amino-5-R-imino-2-phenyl-4H- [1]benzopyrano[3,4-c]pyridines 151. 120 In order to synthesise analogues of the antitumour antibiotic streptonigrin, recyclisation of 4-dicyanomethylene-2-(2-quinolyl)-4H- [1]benzopyran 152 in pyridine in the presence of NH 4 OH has been studied. This reaction gave 4-amino-5-imino-2-(2-quinolyl)-4H- [1]benzopyrano [3,4-c]pyridine 153 in 91% yield.…”

Synthesis and properties of 4-(3-amino-2-benzofuranyl)-coumarins

“…The synthesis of substituted 5H-chromeno[3,4-c]pyridin-5-ones has been studied by many workers and various methods have been reported for the preparation of these compounds, including the condensation of 3-cyano-4-(2-hydroxyphenyl)pyridine derivatives in PPA or HBr/HCl [11][12][13][14], of 4-(2-fluorophenyl)nicotinic acid upon heating [15], of salicylaldehyde, malononitrile, or ethyl cyanoacetate and ketones in the presence of ammonium acetate [16][17][18][19][20][21], of 4-dicyanomethylene-4H-1-benzopyrans with amines [22], and of 3-acetylcoumarin with cyanoacetamide and ketones [23].…”