Regioselective N-methylation of methylthio-substituted pyrimidinones and 1,2,4-triazinone with methanol over H-Y zeolite.

Liquid - phase methylation of 2-methylthio-4-pyrimidone (4), 6-methyl-2-methylthio-4-pyrimidone (5) and 6-methyl-3-methylthio-1,2,4-triazine-5-one (6) with MeOH over HY-Zeolite selectively gave 1-methyl-2-methylthio-4-pyrimidone (7),1,6-dimethyl-2-methylthio-4-pyrimidone (9) and 2,6-dimethyl-3-methylthio-1,24-triazine-5-one (11), respectively. Methyl iodide or dimethyl sulfate have been used as methylating agents for pyrimidines(1-3) and 1,2,4-triazines(4,5). Alkylation of 2-thiouracil (1) and 6-methyl-2-thiouracil (2) with methyl iodide under basic conditions is known to lead.