1.1: 96 percent / benzene / 8 h / Heating 2.1: KH; 18-crown-6 / -78 °C 2.2: 83 percent / tetrahydrofuran / 16 h / -78 - -60 °C 3.1: aq. AcOH / tetrahydrofuran / 0.08 h / 20 °C 4.1: 55 mg / NaBH4 / ethanol / 0.5 h / 0 °C 5.1: 93 percent / p-TsOH*H2O / methanol / 0.25 h / 20 °C View Scheme