1.1: tri-n-butylphosphine / tetrahydrofuran / 2 h / 20 °C 2.1: 0.31 g / pyridine; hydrogen peroxide / tetrahydrofuran; H2O / -40 - 20 °C 3.1: DIBALH / toluene; tetrahydrofuran / 1 h / -78 °C 3.2: 44 percent / triethylsilane; boron trifluoride etherate / CH2Cl2 / 2.5 h / -78 °C 4.1: lithium hydroxide / tetrahydrofuran; H2O / 12 h / 20 °C 5.1: 15 mg / trifluoroacetic acid / CH2Cl2 / 2 h / Heating View Scheme