ozone; trifluoroacetic acid in dichloromethane T=-78°C;

1: 84 percent / methanol / 3 h / Heating 2: 1.) Hg(OAc)2; 2.) NaBH4 / 1.) THF, 4 deg C, 1.5 h 3: 45 percent / Jones reagent 4: 75 percent / potassium hydride, triethylborane / tetrahydrofuran / 3 h / 0 - 25 °C 5: 74 percent / potassium tert-butoxide / 1,2-dimethoxy-ethane / 6 h / 45 °C 6: 75 percent / DIBAL / benzene / 5 h / 25 °C 7: 75 percent / TFA, ozone / CH2Cl2 / -78 °C View Scheme

1: 84 percent / methanol / 3 h / Heating 2: 1.) Hg(OAc)2; 2.) NaBH4 / 1.) THF, 4 deg C, 1.5 h 3: 45 percent / Jones reagent 4: 75 percent / potassium hydride, triethylborane / tetrahydrofuran / 3 h / 0 - 25 °C 5: 74 percent / potassium tert-butoxide / 1,2-dimethoxy-ethane / 6 h / 45 °C 6: 75 percent / DIBAL / benzene / 5 h / 25 °C 7: 75 percent / TFA, ozone / CH2Cl2 / -78 °C View Scheme