1: With ozone in methanol; dichloromethane T=-78°C; 0.266667 h; 2: With dimethylsulfide in methanol; dichloromethane T=-78 - 23°C; 20 h; 3: With triethylsilane; boron trifluoride diethyl etherate in dichloromethane T=-78°C; 2.5 h; Further stages.;