1: 1.) 2,4,6-collidine / 1.) THF, -78 deg C, 10 min, 2.) THF, -78 deg C, 15 min; 20 deg C, 30 min 2: 70 percent / 2 percent benzenesulfonic acid / CHCl3; methanol / 2 h / Ambient temperature 3: 1.) t-butylamine, 2.) methanolic ammonia, 3.) TBAF View Scheme

1.1: 78 percent / CrO3; pyridine; Ac2O / CH2Cl2 / 1 h / 15 °C 2.1: 76 percent / p-TsOH / methanol; CHCl3 / 0.08 h / 20 °C 3.1: CeCl3; BuLi / tetrahydrofuran; hexane / 2.5 h / -50 °C 3.2: 85 percent / tetrahydrofuran; hexane / 3 h / -65 °C 4.1: ammonia / methanol / 24 h / 20 °C 5.1: 24.6 g / TBAF / tetrahydrofuran / 4 h / 20 °C View Scheme