1: CaCO3 / acetonitrile / 48 h / 90 °C 2: 73 percent / NaHMDS / tetrahydrofuran / 1.) 0 deg C, 10 min, 2.) -78 deg C to r.t., 3 h 3: 90 percent / 4 N aq. HCl, methylene blue / tetrahydrofuran / 0.5 h 4: 0.8 M aq. NaIO4, 60-200 mesh SiO2 / CH2Cl2 / 0.08 h / Ambient temperature 5: NaHMDS / 1.) THF, -75 deg C, 2.) CH2Cl2, -75 deg C to r.t., 4 h View Scheme