An integration of electrooxidative cyclization and chemical oxidation was achieved. Electrochemical oxidation of alkenes having a nucleophilic moiety in the presence of DMSO gave cyclized alkoxysulfonium ions, which were converted to the corresponding ketones by treatment with triethylamine in a one-pot sequential manner. The method is also an effective tool for cyclization of 1,6-dienes affording five-membered ring diketones in high stereoselectivity.