1: 51 percent / diethyl ether / 0.25 h / 0 °C / 5 recycles 2: 28 percent / Potassium hydride / hexamethylphosphoric acid triamide; tetrahydrofuran / 2 h / Ambient temperature 3: 41 percent / KOH, hydrazine hydrate (85percent) / various solvent(s) / 6 h / Heating 4: 72 percent / HgO, BF3-OEt2 / tetrahydrofuran; H2O / 1.5 h / Ambient temperature View Scheme