Reduction of alkyl disulphides with triphenylphosphine

Abstract

Alkyl disulphides are reduced to thiols by triphenylphosphine in aqueous methanol, with the phosphine being converted to the oxide. Water is believed to be the source of the hydrogen and oxygen required. The reductions are rather slow; heating for periods of several hours is necessary. Maximum yields of 70–80% are generally obtained, although some substituted alkyl disulphides, such as cystine and dithiodiglycolic acid, are quantitatively reduced. The principal analytical application of this reduction appears to be the determination of aromatic disulphides in the presence of alkyl disulphides, because the aromatic compounds are reduced at a much greater rate.