Synthesis of β-Methylsulfonylated N-Heterocycles from Saturated Cyclic Amines with the Insertion of Sulfur Dioxide.

An efficient synthesis of β-methylsulfonylated N-heterocycles via FeCl3-catalyzed C(sp3)-H dehydrogenation and C(sp2)-H methylsulfonylation of inactivated cyclic amines with the promotion and participation of inorganic sodium metabisulfite and dicumyl peroxide (DCP) has been developed. Notably, bifunctional DCP acted not only as an oxidant to promote the dehydrogenation but also as a methyl radical to participate in the sulfone formation. With this protocol, a number of β-methylsulfonylated tetrahydropyridines, tetrahydroazepines, and pyrroles were obtained in a facile one-pot manner.