Catalyst- and additive-free chemoselective reduction of sulfoxides into sulfides using B2(OH)4 as a deoxygenative agent

An operationally simple and practical method for the reduction of sulfoxides into sulfides using tetrahydroxydiboron [B2(OH)4] as a deoxygenative agent in the absence of catalyst and additive is described. A wide range of diaryl-, dialkyl- and aryl/alkyl-sulfoxides was successfully converted into corresponding sulfides in 92–99% yields. The applicability and practicability were demonstrated by 36 examples and a gram-scale synthesis. This work expands the application field of B2(OH)4 from the reduction of aromatic rings, carbonyls, alkenes, alkynes, imines, nitro compounds, halides to sulfoxides.