1: 96 percent / pyridinium chlorochromate; silica gel / CH2Cl2 / 2 h / 20 °C 2: 98 percent / DBU / CH2Cl2 / 6 h / 20 °C 3: 95 percent / Zn; KOH / ethanol; H2O / 10 h / Heating 4: 88 percent / CeCl3 / tetrahydrofuran / 3 h / 0 - 20 °C 5: POCl3; pyridine / CH2Cl2 / 3 h / 0 - 20 °C View Scheme