On the chemistry of cinnoline I. Synthesis and reactions of (4-amino-cinnolin-3-yl)-p-tolylmethanones

The synthesis of a series of (4-Amino-cinnolin-3-yl)-p-tolyl-methanones from aryl-hydrazonomalononitrile in a one step procedure is reported. The (4-amino-cinnolin-3-yl)-p-tolyl- methanones could be annelated to the corresponding 1,2-dihydro-4-(p-tolyl)-2-oxopyrido{[}3,2-c]cinnoline derivatives via (4-acetamido-cinnolin-3-yl)-p-tolyl-methanones. Treatment of 1,2-dihydro-9-methyl-4-(p-tolyl)-pyrido{[}3,2-c]cinnoline-2-one with POCl3 and P2S5 gave 2-chloro-9-methyl-4-(p-tolyl)-pyrido{[}3,2-c]cinnoline. and 1,2-dihydro-9-methyl-4-(p-tolyl)-pyrido{[}3,2-c]cinnoline-2-thione. Treatment of the ketone with malononitrile afforded 2-amino-3-cyano-9-methyl-4-(p-tolyl)-pyrido{[}3,2-c]cinnoline. Using these ketones, a facile and convenient route towards substituted pyrimidino{[}5,4-c]-cinnolines was developed. Chemical and spectroscopic evidences for the structures of the new compounds are presented.