Reduction of Some Sulfides and Ethers with Aromatic Rings by Electrochemically Generated Solvated Electrons

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Abstract
The reduction of some sulfides and ethers has been investigated in 0.5 M LiCl–HMPA solutions with and without alcohol (methanol, ethanol, and 2-propanol). Diphenyl sulfide underwent cleavage to produce benzene as the main product. The hydrogenated products of benzene have been obtained in 35 and 50 mol % alcohol solutions, and the increased dependence on ethanol (i.e., H+) concentrations in the solutions has been established. The cleavage reaction was affected by the ease of α-hydrogen abstraction from the alcohol. The cleavage reaction has been elucidated as proceeding via a one-electron transfer mechanism, while the hydrogenation proceeded via a two-electron transfer mechanism. The estimation of current efficiencies supports this mechanism. Hexyl phenyl sulfide cleaved in the manner similar to that for diphenyl sulfide with a current efficiency of about 80% whereas only the hydrogenated products were obtained from benzo[b]thiophene and dibenzothiophene. Fission of the C–S bond of tetrahydrothiophene has been achieved by this method. Some ethers examined exhibited approx. the same behavior as the corresponding sulfides.