1: 90 percent / 4 N aq. HCl, methylene blue / tetrahydrofuran / 0.5 h 2: 0.8 M aq. NaIO4, 60-200 mesh SiO2 / CH2Cl2 / 0.08 h / Ambient temperature 3: NaHMDS / 1.) THF, -75 deg C, 2.) CH2Cl2, -75 deg C to r.t., 4 h View Scheme