An aluminum chloride-catalyzed reaction of 1-(phenylthiotrimethylsilylmethyl) cyclohexene, readily obtainable from cyclohexanone, with acid chlorides in dichloromethane underwent a regioselective acylation at the γ-Position of the allylic system to give γ-acyl enol thioethers in good yields. Heating of these enol thioethers with an equimolar amount of p-toluenesulfonic acid produced 2-cyclopentenone derivatives. This novel method for cyclopentannelation ...