Abstract Addition reactions of C-nucleophiles to the C= N bond of 5-phenyl-and 1-methyl-5- phenylpyrimidin-2 (1H)-ones 1a, b and 6-phenyl-1, 2, 4-triazin-3 (2H)-one 2 were investigated. 1a, b and 2 furnished addition products with indoles; 1a also added N- methylpyrrole. Only 2 added thiophene and methyl ketones, and reacted with alkyl halides and acetone forming products resulting both from alkylation and from addition of acetone ...