ANODIC FUNCTIONALIZATION OF VINYL SULFIDES. FORMAL ACCESS TO GEM OR VICINAL ARYL THIOETHER DICATIONS

Article abstract of DOI:10.1016/0040-4020(95)00009-W

The anodic oxidation of a number of vinyl thioethers has been performed in CH3CN-Et3N,3HF.Results clearly show that the reactivity of the vinyl sulfide radical cation depends on several factors as structure of substrates and nucleophilic conditions.For example a dimerization occurred from the unsubstituted vinyl sulfide 1a (CH2=CH-SPh) whereas α,β- and/or β,β-difluoro sulfides were obtained from substituted homologues.In order to understand this reactivity the anodic behaviour of 1a and 1b (Ph-CH=CH-SPh) has been especially analysed in two other nucleophilic media (CH3OH/Et3N,3HF and AcOH/AcOK) leading respectively to methoxylation and acetoxylation of starting compounds.Comparison with electrofluorination results has allowed us to propose a mechanism involving an intermediary episulfonium ion which could explain the formation and ratio of the products isolated.Key Words: vinyl sulfides; enol thioethers; anodic oxidation; electrochemistry; fluorination; methoxylation; acetoxylation; formal dication; fluorosulfides