1: 96 percent / BCl3 / CH2Cl2 / 3 h / Ambient temperature 2: 82 percent / SO2Cl2 3: 91 percent / pyridine / 18 h / Ambient temperature 4: NaClO2, NH3SO3H / tetrahydrofuran; H2O / 5.5 h / Ambient temperature 5: NaOH/H2O / ethanol / 0.75 h / Ambient temperature View Scheme