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

The anodic oxidation of a number of vinyl thioethers has been performed in CH3CN-Et(3)N,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 alpha,beta- and/or beta,beta-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/Et(3)N,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.