1: imidazole / dimethylformamide / 14 h / 25 °C 2: NaH / dimethylformamide / 1.) 0 deg C, 30 min, 2.) 25 deg C, 1 h 3: 86 percent / H2 / PdCl2 / methanol / 0.33 h 4: 99 percent / Et3N, DMAP / CH2Cl2 / 2.5 h / 25 °C 5: 95 percent / NaI / acetone / 15 h / Heating 6: 97 percent / acetonitrile / 45 h / Heating 7: n-BuLi / tetrahydrofuran; hexane / 1.) -78 deg C to -40 deg C, 2.) 20 deg C, 3 h 8: 1.) B2H6*THF, 2.) 3 N NaOH, 30percent H2O2 / 1.) THF, 15-20 deg C, 30 min, 2.) EtOH, 40 deg C, 30 min 9: 100 percent / i-Pr2NEt / CH2Cl2 / 1.) 25 deg C, 5 h, 2.) 40 deg C, 2.5 h 10: 99 percent / nBu4NF / tetrahydrofuran / 2.5 h / 25 °C 11: DMSO, (COCl)2 / CH2Cl2 / 0.5 h / -78 °C 12: t-BuOK / tetrahydrofuran / 1.) 25 deg C, 1.5 h, 2.) 55 deg C, 1 h 13: methanol / 2 h / 25 °C 14: NaBH4, AcOH / 2 h / 25 °C 15: 76 percent / Na, NH3 / tetrahydrofuran / 0.25 h / -78 °C 16: 96 percent / pyridine, DMAP / 0.5 h / 0 °C 17: 42 percent / KI, ZnCu / dimethylformamide / 4 h / Heating 18: aq. acetic acid / 0.5 h / 40 °C 19: Jones reagent / acetone / 1 h / 25 °C 20: 100 percent / 80percent aq. AcOH / 3 h / Heating View Scheme

4-(N,N-dimethlyamino)pyridine; triethylamine in dichloromethane 1 h; Ambient temperature; Yield given. Yields of byproduct given;