Transition Metal-Free C(sp3)-H Bonds Coupling among Three Methyl Groups
A multiple C(sp3)-H bonds coupling of the methyl group in methyl ketones with dimethyl sulfoxides is developed. This coupling allows the direct C(sp3)-H bond coupling among three methyl groups and affords one C-C bond and one C=C bond under the transition metal-free condition. The value-added cyclized 3-methylthiomethyl chroman-4-ones can be synthesized through this method. A plausible mechanism is proposed.