A coupling of multiple C(sp³)–H bonds of the methyl group in methyl ketones with dimethyl sulfoxide is developed. This coupling allows the direct C(sp³)–H bond coupling among three methyl groups and affords one C–C bond and one CC bond under transition metal-free conditions. The value-added cyclized 3-methylthiomethyl chroman-4-ones can be synthesized through this method. A plausible mechanism is proposed.