Syntheses with nitriles. 62. 3,5-Dicyanopyridine derivatives by vilsmeier formylation of malononitrile and tetracyanopropenides

Reaction of malononitrile with dimethylformamide and phosphorus oxychloride gave (dimethylamino-methylene)malononitrile ( 1 ), 4-chloro-7-methyl-5,7-diaza-1,3,5-octatriene-1,1,3-tricarbonitrile ( 3a ) and the pyridine 2 . Compounds 3a and 3b as well as the triaza-derivative 3c may also be obtained by treatment of tetracyanopropenides 4a-c with dimethylformamide and phosphorus oxychloride. Ring closures were achieved by heating 3 under alkaline or acidic conditions. Substitution of chlorine in 3a with aromatic amines provided 1-aryl-1,2-dihydro-2-imino-3,5-pyridinedicarbonitriles 7 . Hydrolysis of 7 gave the 2-oxo-derivatives 8 .