A Green and Facile Synthesis of 6-Methyl-2-(alkylthio)pyrimidin-4(3H)-one

Abstract

Reaction of 2-thiouracil (1) with alkylating agents, namely dimethyl sulphate, diethyl sulphate and benzyl chloride in the presence of potassium carbonate as a mild base, under green conditions, such as simple physical grinding of reactants or in solvents such as ethanol and PEG-600 and under microwave irradiation, gave, respectively 6-methyl-2-(methylthio)pyrimidin-4(3H)-one (2a, i.e., R=CH₃), 6-methyl-2-(ethylthio) pyrimidin-4(3H)-one (2b, i.e., R = C₂H₅) and 6-methyl-2-(benzylthio)pyrimidin-4(3H)-one (2c, i.e., R = PhCH₂Cl). Alternately, condensation of ethyl acetoacetate with S-methylisothiouronium hemisulfate, S-ethylisothiouronium hemisulfate and S-benzyl isothiouronium chloride in ethanolic potassium hydroxide under reflux for 3 h gave 2a-c respectively.