1: 32.1 percent / aq. HCl / dioxane / 51 h / 41 - 43 °C 2: 85 percent / methanol; diethyl ether / 0 - 5 °C 3: 84 percent / LiEt3BH / tetrahydrofuran / 1 h / -78 °C 4: ZnCl2, 4 Angstroem molecular sieves / tetrahydrofuran / 2.5 h / Heating View Scheme