1.1: n-BuLi / tetrahydrofuran; hexane / 0.33 h / 0 °C 1.2: 88 percent / tetrahydrofuran; hexane / 1.5 h / -78 °C 2.1: 67 percent / P2O5 / 20 h / 20 °C 3.1: 28 percent / KOMe / cyclohexane / 16 h / 80 °C View Scheme

1.1: n-BuLi / tetrahydrofuran; hexane / 0.33 h / -78 °C 1.2: 96 percent / tetrahydrofuran; hexane / 1 h / -78 °C 2.1: PBr3; pyridine / CH2Cl2 / 1 h / 20 °C 3.1: 60 percent / t-BuOK / cyclohexane / 16 h / 80 °C View Scheme