1.1: 9.13 g / oxalyl bromide / dimethylformamide; CH2Cl2 / 0.5 h / 0 - 20 °C 2.1: 8.54 percent / CeCl3; NaBH4 / methanol / 1 h / 0 - 20 °C 3.1: 10.19 g / imidazole; 4-N,N-dimethylaminopyridine / CH2Cl2 / 20 °C 4.1: n-BuLi / tetrahydrofuran; hexane / 0.2 h / -78 °C 4.2: 86 percent / tetrahydrofuran; hexane / 4 h / -78 - -30 °C 5.1: tert-BuLi / tetrahydrofuran; pentane / 1 h / -78 - -50 °C 5.2: 73 percent / tetrahydrofuran; pentane / 5 h / -78 - -50 °C View Scheme