Some specific features of acid nitration of 2-substituted 4,6-dihydroxypyrimidines. Nucleophilic cleavage of the nitration products

The nitration of 2-substituted 4,6-dihydroxypyrimidines in concentrated sul furic acid yields the corresponding 5,5-dinitro derivatives. When the subst ituent in position 2 is an alkyl group, the nitration occurs both at positi on 5 and at the cx-carbon atom of the side chain. Hydrolysis of 2-substitut ed 4,6-dihydroxy-5,5-dinitropyrimidines leads to formation of 1,1-diamino-2 -R-2-nitroethylene derivatives. 1,1-Diamino-2,2-dinitroethylene was obtaine d by nitration of 4,6-dihydroxy-2-methylpyrimidine and subsequent hydrolysi s of 4,6-dihydroxy-5,5-dinitro-2-(dinitromethylene)-2,5-dihydropyrimidine.