Nitration of some 2-substituted pyrimidine-4, 6-diones in sulfuric acid was studied, which afforded previously unknown 5, 5-gem-dinitropyrimidine-4, 6-diones in high yields. The gem- dinitro products were easily attacked by nucleophiles with concomitant formation of gem- dinitroacetyl derivatives, which in turn could be further hydrolyzed to salts of dinitromethane and triureas.