Cinnolines. Part XVII. Reactions of 4-chlorocinnoline-3-carbonitrile and preparation of 2,3-dihydro-3-imino-1H-pyrazolo[4,3-c]cinnolines

Reaction of 3-bromo-4(1H)-cinnoline with copper(I) cyanide in pyridine yields 1,4-dihydro-4-oxocinnoline-3-carbonitrile, which is converted into 4-chlorocinnoline-3-carbonitrile by treatment with phosphoryl chloride. Catalytic hydrogenation of the chloro-compound in the presence of base gives 4,4′-bicinnolyl-3,3′-dicarbonitrile. Condensation reactions of the chloro-compound yield 1,4-dihydro-4-thioxocinnoline-3-carbonitrile (with thiourea), 3-cyanocinnolin-4-ylmalononitrile and similar products (with carbanions), methyl 2,3-dihydro-3-iminothieno[3,2-c]cinnoline-2-carboxylate (with methyl thioglycolate), and 2,3-dihydro-3-imino-1H-pyrazolo[4,3-c]cinnoline and related compounds (with hydrazine and substituted hydrazines).