trifluoroacetic acid; trifluoroacetic anhydride T=0°C; 45 h; Heating / reflux;

1: m-CPBA; TsOH / CH2Cl2 / 20 °C 2: K2CO3 / CH2Cl2; methanol 3: 60 percent / acetic acid / Heating View Scheme

1: 93 percent / TiCl4 2: m-CPBA; TsOH / CH2Cl2 / 20 °C 3: K2CO3 / CH2Cl2; methanol 4: 60 percent / acetic acid / Heating View Scheme

1.1: 97 percent / K2CO3; Br2 / CH2Cl2 / 1 h / 0 °C 2.1: 94 percent / diisopropylethylamine / dimethylformamide / 1.5 h / 20 °C 3.1: 77 percent / i-PrOTMS; TMSOTf / CH2Cl2 / -78 °C 4.1: 85 percent / tetrahydrofuran / 24 h / Heating 5.1: 85 percent / Me2AlCl / CH2Cl2 / 0.17 h / -78 °C 6.1: LHMDS / tetrahydrofuran; hexane / 1.5 h / -78 - -10 °C 6.2: 70 percent / tetrahydrofuran; hexane / 3 h / -20 - 0 °C 7.1: 81 percent / NaBH4 / ethanol / 2.5 h / -78 °C 8.1: 95 percent / 2,6-lutidine / CH2Cl2 / 1 h / -10 °C 9.1: n-BuLi / tetrahydrofuran; pentane / 0.08 h / -78 °C 9.2: BF3*Et2O / tetrahydrofuran; pentane / 3 h / -78 °C 10.1: 57 percent / second generation Grubbs' catalyst / CH2Cl2 / 48 h / 50 - 55 °C 11.1: 89 percent / 2,6-lutidine; DMAP / pyridine / 1 h / 0 - 20 °C 12.1: 78 percent / pyridine; OsO4 / tetrahydrofuran / 5 h / 0 °C 13.1: 95 percent / pyridine / CH2Cl2 / 2 h / 0 °C 14.1: 84 percent / BnNMe3OH / methanol; tetrahydrofuran / 1 h / 0 °C 15.1: n-BuLi; WCl6 / tetrahydrofuran; hexane / 0 - 20 °C 16.1: 12 mg / pyridinum p-toluenesulfonate / methanol / 6 h / 0 °C 17.1: 69 percent / Dess-Martin periodinane; pyridine / CH2Cl2 / 0 - 20 °C 18.1: 40 percent / aq. HF / acetonitrile / 0 - 20 °C View Scheme

1: 86 percent / hydrazine hydrate, KOH / 1.) reflux, 15 min; 2.) 120 deg C, 30 min; 3.) 140 deg C, 30 min 2: 77 percent / ceric ammonium nitrate / H2O; acetonitrile / 0.75 h / Ambient temperature View Scheme