1: 95 percent / pyridine, N,N-dimethylaminopyridine (DMAP) / CH2Cl2 / 12 h / Ambient temperature 2: 80 percent / pyridinium chlorochromate, 3 Angstroem molecular sieves / CH2Cl2 / 12 h / Ambient temperature 3: 100 percent / 50percent aq. CF3COOH / 4 h / Ambient temperature View Scheme