An oxidative CÀ N bond cleavage reaction of substituted cyclic sulfonamides that proceeds via oxidation of bromide ion in hydrogen bromide solution was developed to furnish N-sulfonamideprotected acyclic amino ketones in high yields. The subsequent α-amination of the amino ketones via the oxidation of iodide in tetrabutylammonium iodide provided 2-acyl cyclic sulfonamides in good yields. The combination of these transformations involving the oxidation of halides resulted in a formal ring contraction of substituted cyclic amides.

An asymmetric synthesis of 2-bromomethyl-5-substituted tetrahydrofurans via a chiralruthenium-catalyzed transfer hydrogenation of 3butenyl ketones and bromoetherification of chiral pentenyl alcohols was developed. The inhibition of some side reactions furnished the desired products in high yields with high enantioselectivities. In addition, chiral pentenyl alcohols bearing electrondonating groups triggered substrate racemization in the aerobic bromoetherification.