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

Abstract

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.

Keywords:

• Deoxygenation
• HfCl₄/KBH₄
• reduction
• sulfides
• sulfoxides

Notes

^a Dry THF was added to the mixture of HfCl₄ and KBH₄ under nitrogen and stirred for 3 h at room temperature, and then a solution of 1 in dry THF was added dropwise and heated to the reaction temperature.

^b Isolated yield; all products were identified by ¹H NMR and mass spectrometry.

^c The preparation of reducing agent was not under nitrogen.

^a Dry THF was added to the mixture of HfCl₄ and KBH₄ under nitrogen and stirred for 3 h at room temperature, and then a solution of substrate in dry THF was added dropwise and heated to the reaction temperature.

^b Isolated yield; all products were characterized by ¹H NMR and mass spectrometry.

^c Conversion.

^d NR, no reaction.