1: 71 percent / CrO3, 3,5-dimethylpyrazole / CH2Cl2 / 0.5 h / -20 °C 2: 43 percent / BBr3 / CH2Cl2 / 2.5 h / -78 - -10 °C 3: 62 percent / BF3*Et2O / CH2Cl2 / 1 h / Ambient temperature 4: 67 percent / Raney nickel W-7 / ethanol / 3 h / Heating 5: 87 percent / LiAlH4 / tetrahydrofuran / 1 h / 0 °C 6: 77 percent / aq. potassium nitrosodisulfonate, KH2PO4 / acetone / 0.5 h / Ambient temperature View Scheme