The reaction of 2-amino-N′-arylbenzamidines with tetracyanoethene reinvestigated: routes to imidazoles, quinazolines and quinolino[2′,3′:4,5]imidazo[1,2-c]quinazoline-8-carbonitrile

2-Amino-N'-phenylbenzamidine (1a) reacts with tetracyanoethene (TCNE) to give 2-[2-(2-aminophenyl)-5-imino-1-phenyl-1H-imidazol-4(5H)-ylidene]malononitrile (Ha), 4-(phenylamino)uinazoline-2-carbonitrile (5a) and 4-imino-3-phenyl-3,4-dihydroquinazoline-2-carbonitrile (9a). By optimizing the reaction conditions each of the compounds can be isolated as the main product and seven examples of these reactions are described. The [1H-imidazol-4(5H)-ylidene]malononitrile ha was also independently synthesized in three steps from 2-amino-N'-(2-nitrophenyl)benzamidine (25) and TCNE in an overall yield of 56%. Dimroth rearrangement of either 2-aminophenyl- or 2-nitrophenyl-substituted [1H-imidazol-4(5H)-ylidene]malononitriles ha or 27 with DBU in hot DCM gave the 2-[2-(2-aminophenyl)- and 2-[2-(2-nitrophenyl)-5-(phenylimino)-3H-imidazol-4(5H)-ylidene]malononitriles 28 (71%) and 34(59%), respectively. Treatment of the [3H-imidazol-4(5H)-ylidene]malononitrile 28 with ethyl orthoformate in DMA at 165 degrees C gave (Z)-2[3-(phenylimino)imidazo[1,2-c]quinazolin-2(3H)-ylidene]malononitrile (36) (70%), thermolysis of which gave quinolino[3',2':4,5]imidazo[1,2-c]quinazoline-13-carbonitrile (30) (97%). (C) 2015 Elsevier Ltd. All rights reserved.