Making full use of the oxidizing equivalents in bromate in the selective oxidation of thiols, sulfides, and benzylic/secondary alcohols into disulfides, sulfoxides, and aldehydes/ketones

Abstract

The oxidation of thiols to disulfides was achieved in high yields with 6:1 mol ratio of thiol to NaBrO₃, while the oxidation of sulfides and benzylic/secondary alcohols to the corresponding sulfoxides and aldehydes/ketones was successfully undertaken with 3:1 mol ratio of substrate to NaBrO₃. These ratios correspond to the minimum theoretical requirement of NaBrO₃. The reactions were conducted at 0-30°C, depending upon substrate, and were initiated with catalytic amounts of H⁺ and Br⁻ (initial Br⁻/BrO₃⁻ = 1:3.5 for thiol oxidation and 1:8 for sulfide and alcohol oxidation). Further, regeneration and reuse of the spent reagent in the aqueous effluent was demonstrated.