The synthesis of polyenes by electrolysis of beta -acetoxy phenyl sulfones having some double bonds was studied in acetonitrile using a Hg pool cathode and a sacrificial ME anode. Most unsaturated beta -acetoxy phenyl sulfones were subject to the electroreductive elimination of both the acetoxy and the sulfonyl groups, but did not give the desired polyenes because of partial hydrogenation of double bonds. The electrolytic reduction of a beta -acetoxy phenyl sulfone having a trifluoromethyl group at the beta -position was subjected to such 1.2-elimination followed by reductive removal of all fluorine atoms to afford the corresponding unsaturated hydrocarbons, whereas beta -acetoxy phenyl sulfones having a fluorine atom at the alpha -position gave the desired fluoro-olefins in high yields. All saturated beta -acetoxy phenyl sulfones afforded the desired alkenes in high yields. (C) 2001 Elsevier Science Ltd. All rights reserved.