Synthesis of some novel pyridine and naphthyridine derivatives

2-[1-(Furan- or thiophen-2-yl)ethylidene)malononitriles (1a,b) undergo dimerization reactions in ethanol catalyzed by sodium ethoxide to afford 2-[4,6-di(furan- or thiophen-2-yl)-3-cyano-6-methyl-5,6-dihydropyridin-2(1H)-ylidene]malononitrile derivatives (2a,b), respectively. Compounds 2a and 2b couple with arene diazonium salts (3a-c) to afford the hydrazo derivatives (4a-f). They react also with hydrazines (5a,b) to afford the pyrazolo[3,4-H][1,6]naphthyridine derivatives (6a-d) and with urea derivatives (7a-c) to afford the pyrimido[4,5-H][1,6]naphthyridine derivatives (8a-f), respectively