1: With dicobalt octacarbonyl in dichloromethane T=20°C; 1 h; 2: With boron trifluoride diethyl etherate in dichloromethane T=20°C; Nicholas reaction; 3 h; 3: With ammonium cerium(IV) nitrate in acetone T=0°C; 0.0833333 h; Further stages.;