1: 5.1 g / CrO3, pyridine / CH2Cl2 / 2 h 2: hydrazine hydrate / ethanol / 1 h / Heating 3: m-CPBA / CH2Cl2 / 1 h / 0 °C 4: 15 mg / 48 percent aq. HBr, glacial acetic acid / 0.25 h / Heating View Scheme