1 -Amino-3-aryl-2-cyano-177,6/7-pyrido

Cycloaddition of 2-styryl-4/7-3,l-benzoxazines and malononitrile gave 1 -amino-3-aryl-2-cyano-1 //,6//-pyrido[l, 2-n][3, l]benzoxazin-4-ones (99ZN(B)923). These tricyclic derivatives were also prepared in the reaction of 2-methyl-4//-3,l-benzoxazin-4-one and arylidenemalononitrile in AcOH in the presence of NaOAc. 

Cyclocondensation of ethyl 2-aminonicotinate in presence of HC(OEt)3 and various primary amines gave 22 3-substituted pyrido[2,3-,7]pyrimidin-4(377)-ones 371 <1995PHA719>. Fourteen 3,5,7-triarylpyrido[2,3-r7]pyrimi-dine-2,4(l/7,37/)-diones 372 have been prepared from the reaction of either 2-amino-3-cyano-4,6-diarylpyridines or the 3-carboxamido products of alcoholic KOH hydrolysis, with aryl isocyanates better yields were obtained from the amides <1995IJB740>. 4-Aminopyrido[2,3- pyrimidin-5(8//)-one 158 was synthesized by treatment of 2-amino-3-cyano-4-methoxypyridine with trimethylsilyl iodide to give the corresponding pyridin-4(177)-one, which was refluxed with formamidine acetate in ethoxyethanol to effect the cyclization <2000JME3704>. 

In a related reaction sequence, either arylhydrazones of diethyl 3-amino-2-cyano-4-oxopent-enedioate or their cyclization products, the corresponding ethyl 4-amino-l-aryl-5-cyano-6-oxo-l,6-dihydropyridazine-3-carboxylates react with malononitrile or ethyl cyanoacetate to give pyrido[2,3-d]pyridazine-2,5(1 f/,6//)-diones 2 or 3.71... 

Amino-4-aryl-3-cyano-7,7-dimethyl-5,6,7,8-tetrahydro-4H-benzo[f>]pyran 281 were reacted with benzylidene malononitrile in the presence of piperidine at 160 °C to afford pyrido[3,4-frJqu inclines 341 (89JPR971) (Scheme 65). 

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