1: 89 percent / pyridine / 21 h / 20 °C 2: 70 percent / TBAF / tetrahydrofuran / 18 h / 40 °C 3: 75 percent / Pd(PPh3)2Cl2; CuI; Et3N / 3.5 h / 20 °C 4: 73 percent / TsNHNH2; NaOAc / 1,2-dimethoxy-ethane; H2O / 4 h / Heating 5: 57 percent / aq. HCl / methanol; tetrahydrofuran / 15 h / 20 °C View Scheme