dimethylsulfide; ozone in methanol; dichloromethane 1) -70 deg C, 2 h; 2) -50 deg C, 30 min;

2: 4N KOH / ethanol / 2 h / Heating 3: 69.4 percent / O3, Me2S / methanol; CH2Cl2 / 1) -70 deg C, 2 h; 2) -50 deg C, 30 min View Scheme