barium carbonate in tetrahydrofuran 3 h; Ambient temperature;

1: HBr (gas) / CH2Cl2 / 1 h / 0 - 5 °C 2: 42 percent / barium carbonate / tetrahydrofuran / 3 h / Ambient temperature View Scheme

1: boron trichloride / CH2Cl2 / 1 h / -70 - -65 °C 2: HBr (gas) / CH2Cl2 / 1 h / 0 - 5 °C 3: 42 percent / barium carbonate / tetrahydrofuran / 3 h / Ambient temperature View Scheme