Diazo coupling reactions of some methylpyrimidines

Abstract

The coupling of diazotised p-chloroaniline with 4-methyl- and 4,6-dimethyl-2-pyrimidone has been shown to occur not at the 5-position as previously reported, but at the 4-methyl group to give the p-chlorophenylhydrazones of the corresponding pyrimidine-4-carbaldehydes. 2,6-Dimethyl-4-pyrimidone and 1,4,6-trimethyl-2-pyrimidone undergo the same reaction at the 6-methyl group. p-Chlorobenzenediazonium chloride has been shown to react with 5-methylcytosine to give a p-chlorophenylazoaminopyrimidine which also has another p-chlorophenyl azo-group, probably at N-1.