1: P2O5, H3PO4 / 0.5 h / 60 - 70 °C 2: 86 percent / BBr3 / CH2Cl2 / 1 h / Ambient temperature 3: 40 percent / Potassium nitrosodisulfonate, potassium hydrogen phosphate / acetone; H2O View Scheme

1: P2O5, H3PO4 / 0.5 h / 60 - 70 °C 2: 80 percent / pyridinium chlorochromate / CH2Cl2 / 96 h / Ambient temperature 3: 82 percent / NaBH4 / ethanol / 1 h / Ambient temperature 4: 42 percent / CH3SO2Cl, Et3N / CH2Cl2 / 0 °C 5: 77 percent / NaH, EtSH / dimethylformamide / 3 h / 150 °C 6: 57 percent / potassium nitrosodisulfonate, potassium hydrogen phosphate / H2O; acetone / 4 h View Scheme