1: conc. hydrochloric acid / Ambient temperature 2: 93 percent / potassium persulphate, conc. sulfuric acid / H2O; methanol / 3 h / 5 °C 3: 68 percent / pyridinium chlorochromate / CH2Cl2 / 1 h / Ambient temperature View Scheme

sulfuric acid in dichloromethane

in diethyl ether T=5°C;