Formation of Elusive vic-Disulfoxides and OS-Sulfenyl Sulfinates during the m-Chloroperoxybenzoic Acid (MCPBA) Oxidation of Alkyl Aryl Disulfides and Their Regioisomeric Sulfinothioic Acid S-Esters

Article abstract of DOI:10.1021/jo00206a013

The initial step in the 1 equiv m-chloroperoxybenzonic acid (MCPBA) oxidation of 2,2-dimethylpropyl phenyl disulfide (10) and phenyl phenylmethyl disulfide (14) occurs predominantly at the sulfur atom bonded to the alkyl group to give S-phenyl 2,2-dimethylpropanesulfinothioate (5) and S-phenyl phenylmethanesulfinothioate (6), respectively.The 2 equiv MCPBA oxidation of disulfide 10 gives S-phenyl 2,2-dimethylpropanesulfonothioate (23) as the major product.The 1 equiv MCPBA oxidation of thiosulfinates 5 and 6 and S-2,2-dimethylpropyl benzenesulfinothioate (9) ultimately gives thiosulfonate 23, S-phenyl phenylmethanesulfonothioate (17), and thiosulfonate 23, respectively, as the major products.Thus, peroxidation of regioisomeric S-alkyl and S-aryl sulfinothioates 5 and 9 occurs predominantly at the sunfenyl sulfur atom to give diastereomeric vic-disulfoxides (α-disulfoxides) which may undergo cycloelimination to sulfines and sulfenic acids, dissociate to sulfinyl radicals, and rearrange intramoleculary to OS-sulfenyl silfinates and/or to sulfonothioic acid S-esters.OS-Sulfenyl sulfinates may isomerize to sulfonothioic acid S-esters or dissociate to sulfinyl radicals and/or to thiyl and sulfonyl radicals.The sulfinyl radicals may combine to form vic-disulfoxides and/or OS-sulfenyl sulfinates while the thiyl and sulfonyl radicals may lead to sulfonothioic acid S-esters.