1: 1) n-BuLi / 1) hexane, THF, -70 deg C, 15 min, 2) 4 h 2: 62 percent / n-BuLi / tetrahydrofuran; hexane / 6 h / -70 °C 3: 99 percent / potassium azodicarboxylate, AcOH / methanol / 1 h / Ambient temperature 4: 0.1 N TFA / tetrahydrofuran / 4 h / Ambient temperature View Scheme