Synthesis of 5-Methylmercaptouracil

5-Methylmercaptouracil was prepared by the reaction of uracil with dimethyl sulfoxide and monochloromethyl ether. At the same time the formation of methylal, methyl sulfide, methyl disulfide, methyl methanethiolsulfonate, methyl chloride and paraformaldehyde were observed. Acetyl chloride was successfully used instead of monochloromethyl ether. Uracil reacted with dimethyl sulfoxide and phenacyl bromides, resulting in the formation of 5-bromouracil. The mechanism of these reactions were discussed.