1: 72 percent / NaHCO3, CF3CO3H, urea / acetonitrile / 1.42 h / 0 °C 2: 85 percent / pyridinium chlorochromate / CH2Cl2 / 3.2 h / 23 °C 3: toluene / 19 h / 80 °C 4: 1.) hydrochloric acid 2.)DBN / 1.) THF, 0 deg C, 30 min, 2.) 0 deg C, 1 h 5: K2CO3 / acetone / 2.5 h / Heating View Scheme

1: 72 percent / NaHCO3, CF3CO3H, urea / acetonitrile / 1.42 h / 0 °C 2: 85 percent / pyridinium chlorochromate / CH2Cl2 / 3.2 h / 23 °C 3: toluene / 19 h / 80 °C 4: 1.) hydrochloric acid 2.)DBN / 1.) THF, 0 deg C, 30 min, 2.) 0 deg C, 1 h View Scheme