Electrosynthesis of sulfur-containing organic compounds from cumulene derivatives using a sacrificial sulfur-graphite electrode

Abstract

Electrosynthesis of sulfur-containing organic compounds from cumulene derivatives was studied using a sacrificial sulfur-graphite electrode. 1,1-Di- p-chlorophenyl-4,4-diphenylbuta-1,2,3-triene ( 1a), 1,1-di- p-chlorophenyl-4,4-di- p-methylphenylbuta-1,2,3-triene ( 1b), 1,1,4,4-tetraphenylbuta-1,2,3-triene ( 1c) and 1,1-di- p-methoxyphenyl-4,4-diphenylbuta-1,2,3-triene ( 1d) were used as cumulenes. With 1a, 1b and 1c, 7-membered ring compounds with five sulfur atoms such as pentathiepins 2a, 2b and 2c were produced as the major products accompanied with dimeric compounds 3a, 3b and 3c which had a 1,2,5,6-tetrathiocin skeleton in minor amounts, respectively. However, 1d, which is the most difficult to be reduced among the cumulenes studied, did not give sulfur-containing organic compounds. Yields of 2a, 2b and 2c decreased a little by the addition of a proton donor such as benzoic acid. Main products 2 will be initiated by a Michael addition of the polysulfide anion(s) (S 8 2− and/or S 6 2−) produced by electroreduction of elemental sulfur. By-products 3 will be probably produced by further reaction of 2 with the polysulfide anion(s).