1: p-toluenesulfonic acid / methanol / 5 h / Ambient temperature 2: pyridine / 20 h / 0 °C 3: 75 percent / HgBr2, Mg / diethyl ether / 6 h 4: Bu3SnH, azobis<isobutyronitrile> (AIBN) / benzene / 1.5 h / Heating; also without solvent, at 75 deg C View Scheme

1: p-toluenesulfonic acid / methanol / 5 h / Ambient temperature 2: pyridine / 20 h / 0 °C 3: 75 percent / HgBr2, Mg / diethyl ether / 6 h 4: Bu3SnH, azobis<isobutyronitrile> (AIBN) / benzene / 1.5 h / Heating; also without solvent, at 75 deg C View Scheme

1: p-toluenesulfonic acid / methanol / 5 h / Ambient temperature 2: pyridine / 20 h / 0 °C 3: 75 percent / HgBr2, Mg / diethyl ether / 6 h View Scheme

methanol; toluene-4-sulfonic acid T=20°C; Hydrolysis; 2 h;