Oxidation of Sulfides by Acyclic α-Azohydroperoxides

Article abstract of DOI:10.1021/jo00149a014

The oxidation of sulfides with a series of substituted benzylazobenzene α-hydroperoxides (2a-f) produced the corresponding sulfoxides in good yield (ca. 90 percent) in C6D6 at 34 deg C.The reaction was found to be of the first order with respect to α-azohydroperoxide and to sulfide in aprotic medium.The reaction of BzSPh with acyclic α-azohydroperoxide 2a in C6D6 was found to be slower than the corresponding oxidation with 3-bromo -4,5-dihydro-5-hydroperoxy-4,4-dimethyl-3,5-diphenyl-3H-pyrazole in CDCl3.The relative reactivity series of sulfides with α-azohydroperoxide 2a was found to be Me2S (25)> BzSMe (14)> PhSMe (2.5)> BzSPh (1.0).This is similar to that observed for the reaction of the sulfides with hydrogen peroxide in protic solvent and reflects the relative nucleophilicities of the sulfides.The second-order rate constants for the reaction of a series of substituted benzylazobenzene α-hydroperoxides with PhSMe and BzSMe exhibited an excellent correlation with ? values.Both LFERs had ρ values of approximately 1.0.The results were interpreted to be consistent with nucleophilic attack of the sulfide on oxygen.Concomitant transfer of the hydroperoxy proton to the azo nitrogen would account for the lack of the requirement of general acid catalysis in aprotic medium.