1: p-toluenesulfonic acid / 24 h / Ambient temperature 2: 90 percent / diisobutylaluminium hydride / diethyl ether; toluene / 1.5 h / -10 °C 3: 100 percent / pyridine / 20 h / 0 °C 4: 1.) CuI / 1.) Et2O, -5 deg C, 40 min, 2.) Et2O, from -5 to 0 deg C, 15 h 5: 95 percent / 10percent aq. HCl / acetone / 6 h 6: 1.) Mg / 1.) THF, 2.) THF, RT, 3 h 7: pyridine / 20 h / 0 °C 8: NaI, Zn / tetrahydrofuran / 3 h / Heating 9: 95 percent / 10percent aq. HCl / acetone / 6 h / 40 °C 10: 95 percent / diisobutylaluminium hydride / diethyl ether; toluene / 1.5 h / -10 °C 11: 75 percent / pyridine View Scheme

toluene-4-sulfonic acid 24 h; Ambient temperature; Yield given;