1.1: 76 percent / p-TsOH / methanol; CHCl3 / 0.08 h / 20 °C 2.1: CeCl3; BuLi / tetrahydrofuran; hexane / 2.5 h / -50 °C 2.2: 85 percent / tetrahydrofuran; hexane / 3 h / -65 °C 3.1: ammonia / methanol / 24 h / 20 °C 4.1: 24.6 g / TBAF / tetrahydrofuran / 4 h / 20 °C View Scheme