An efficient potassium persulfate mediated four component reaction for the construction of 5-methyl pyrimidine derivatives has been established from readily available methyl ketones, amidine hydrochlorides and dimethyl sulfoxide. This transformation features dimethyl sulfoxide as a dual synthon, acting as the precursors of the methyl and methine units. Four new chemical bonds, involving two C−C and two C−N bonds were formed sequentially during the intermolecular oxidative annulation process. This synthetic method offers several advantages inc...