1: 53 percent / 48percent aq. HBr / 18 h / 105 °C 2: 43 percent / SeO2 / dioxane; H2O / 4 h / 160 °C 3: 45 percent / pyridinium dichromate, 4-Angstroem molecular sieves / CH2Cl2 / 3.5 h / 0 °C View Scheme

1: 90 percent / sodium hexamethyldisilazide / tetrahydrofuran / 16 h / -70 deg C to room temperature 2: 1) O3, 2) Me2S / 1) MeOH, CH2Cl2, O3, -70 deg C, 2) -70 deg C to room temperature, 12 h 3: 94 percent / benzene; methanol; hexane / 3 h 4: 75 percent / p-TsOH / toluene / 4 h / Heating 5: 71 percent / 48percent aq. HBr / 15 h / 140 °C 6: 91 percent / O2, CuCl2, dimethylamine / dimethylformamide / 7 h View Scheme

hydrogen bromide T=105°C; 18 h;