titanium(IV) isopropylate; titanium tetrachloride in dichloromethane T=-78°C; 4 h;

1: 94 percent / p-toluenesulphonic acid / benzene / Heating 2: 86 percent / CuI / diethyl ether / 1 h / Ambient temperature 3: 69 percent / Br2 / acetic acid / 30 h / Ambient temperature; 1) 1 h, 0 deg C, 2) r.t., 30 min 4: 78 percent / CaCO3 / dimethylformamide / Heating View Scheme

toluene-4-sulfonic acid in benzene Heating;

1: 94 percent / p-toluenesulphonic acid / benzene / Heating 2: 86 percent / CuI / diethyl ether / 1 h / Ambient temperature View Scheme

1: 94 percent / p-toluenesulphonic acid / benzene / Heating 2: 86 percent / CuI / diethyl ether / 1 h / Ambient temperature 3: 69 percent / Br2 / acetic acid / 30 h / Ambient temperature; 1) 1 h, 0 deg C, 2) r.t., 30 min View Scheme