1.1: 87 percent / 10-camphorsulfonic acid / benzene / 24 h / 20 °C 2.1: tert-BuLi / tetrahydrofuran; pentane / 1.25 h / -78 - -20 °C 2.2: 82 percent / tetrahydrofuran; pentane / 0.5 h / -78 °C 3.1: 79 percent / sodium amalgam / methanol / 4 h / Heating View Scheme