1: 69 percent / manganese dioxide / CH2Cl2 / 24 h / Ambient temperature 2: 64 percent / N-bromosuccinimide / benzene / 1 h / Irradiation 3: 55 percent / tris(trimethylsilyl)silane, azoisobutyronitrile (AIBN) / toluene / 2 h / 85 °C 4: 36 percent / boron tribromide / CH2Cl2 / 1 h / -40 °C View Scheme