Mild and Efficient Deoxygenation of Sulfoxides to Sulfides Using HfCl4/KBH4 System

HfCl4/KBH4 was found to be a facile, efficient, convenient, and chemoselective system for the deoxygenation of dialkyl, diaryl, and aryl alkyl sulfoxides, especially for the reduction of dibenzyl sulfoxide to the corresponding sulfides under mild conditions. In addition, the HfCl4/KBH4 system could be used in reduction of some other sulfur-bearing substrates to the corresponding sulfides, such as 2,2'-dibenzothiazolyl disulfide, but this reducing system could not reduce sulfolane, diphenyl sulfone, p-toluenesulfonic acid, and p-toluenesulfonyl chloride to their corresponding thiophenols.