1: 89 percent / tetrahydrofuran / -78 °C 2: 85 percent / L-Selectride; ZnCl2 / CH2Cl2; tetrahydrofuran; diethyl ether / -78 - 20 °C 3: 70 percent / diisopropyl azodicarboxylate; triphenylphosphine / tetrahydrofuran / 48 h / 4 °C 4: 93 percent / aq. acetic acid / 5 h / 50 °C View Scheme