1: 100 percent / potassium carbonate / methanol / 2 h / Ambient temperature 2: 100 percent / 4-dimethylaminopyridine, pyridine / CH2Cl2 / 1 h / 0 °C 3: 96 percent / acetic acid, water / tetrahydrofuran / 24 h / Ambient temperature 4: 91 percent / PCC, sodium acetate, Celite / CH2Cl2 / 1 h / Ambient temperature View Scheme