Electrosynthesis of Sulfur-containing Organic Compounds using a Reactive Sulfur-Graphite Electrode

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Sulfur-containing organic compounds could be transformed to an aimed compound by applying the fruitful sulfur chemistry. Therefore, it is interesting to study incorporation of sulfur functionality into the organic compounds using a reactive sulfur-graphite electrode (S-C electrode). In the present work, we carried out introducing of sulfur functionality into the following compounds : cumulenes havingtrifluoromethyl groups, phenylsulfonylpropennitriles, and phenylsulfonylpropennitriles having a trifluoromethyl group. The present work leads to the following conclusions.(1) Electroreduction of cumulenes with trifiuoromethyl groups using the S-C electrode afforded dimeric compounds with a 1,2,5,6-tetrathiocin skeleton as the major products. There was a large difference in the main product between the cumulenes with and without trifluoromethyl groups, cumulenes without trifluoromethyl groups yielding 7-membered ring compounds with five sulfur atoms such as pentathiepins.(2) 3-Aryl-2-phenylsulfonylpropenenitriles having geminal cyano and sulfonyl groups gave dimeric 5-arylisothiazoles bridged with two or three sulfur atoms at the 3-position in moderate yields. 2-Phenyl-3-phenylsulfonylpropenenitrile havingvicinal cyano and sulfonyl groups yielded dimeric 4-phenylisothiazole bridged with two sulfur atoms together with 3-[(Z)-2-cyano-2-phenylethenylthio]-5-phenylisothiazole. This electrosynthesis of sulfur-containing compounds is characterized as elimination of a phenylsulfonyl group accompanying the addition of polysulfide anion(s) produced by electroreduction of elemental sulfur.(3) 2-(4-Biphenylyl)-3-phenylsulfonyl-3-trifluoromethylpropenenitrile afforded a coupling compound bridged with a nitrogen atom of isothiazole and 1,2-dithiolane skeleton.