1: 1.) sodium bis(trimethylsilyl)amide, hexamethylphosphoric triamide (HMPA) / 1.) THF, -78 deg C, 30 min, 2.) THF, 30 min 2: 89.3 percent / pyridine*(HF)x / tetrahydrofuran / 1 h / 0 °C 3: 28 percent / PPh3, diethyl azodicarboxylate (DEAD) / benzene / 48 h / Ambient temperature 4: 84 percent / tetrabutylammonium fluoride / tetrahydrofuran / 0.05 h / Ambient temperature 5: 49 percent / 3 N aq. HCl / tetrahydrofuran / 18 h / Ambient temperature View Scheme