Fixation of sulfur dioxide into small molecules.

Sulfonyl-derived functional groups can be found in a broad range of natural products, pharmaceuticals, and materials. Among the methods for the introduction of the sulfonyl group into small molecules, the approach using sulfur dioxide is the most promising and attractive one. In the past several years, the insertion of sulfur dioxide into small molecules under transition metal catalysis or metal-free conditions via a radical process has been developed. In this review, recent advances in the insertion of sulfur dioxide are presented.