sodium hydroxide in methanol 1) RT, 3 h, 2) 20 h, reflux;

hydrogen bromide in acetic acid 0.5 h; Heating;

1: 78 percent / CrO3 / H2SO4; acetone / 1.5 h / 0 - 10 °C 2: 85 percent / HBr / acetic acid / 0.5 h / Heating View Scheme

1: 90 percent / K2CO3 / acetone / 16 h / Heating 2: 78 percent / CrO3 / H2SO4; acetone / 1.5 h / 0 - 10 °C 3: 85 percent / HBr / acetic acid / 0.5 h / Heating View Scheme

1.1: Na2S2O4; NaOH / methanol; H2O / 0.67 h / 0 °C 1.2: 63 percent / H2O2 / methanol; H2O 2.1: 90 percent / K2CO3 / acetone / 16 h / Heating 3.1: 78 percent / CrO3 / H2SO4; acetone / 1.5 h / 0 - 10 °C 4.1: 85 percent / HBr / acetic acid / 0.5 h / Heating View Scheme