1: 1.) CDI, 2.) NaBH4 / 1.) THF, 15 h, 20 deg C, 2.) THF, H2O, 20 deg C 2: 100 percent / MnO2 / acetone / 72 h / 20 °C 3: 98 percent / TFA / 15 h / 20 °C View Scheme

1: polyphosphoric ethyl ester / CHCl3 / 1 h / Heating 2: 87 percent / aq.NaOH / ethanol / 0.17 h / Heating View Scheme

1: 1.) CDI, 2.) NaBH4 / 1.) THF, 15 h, 20 deg C, 2.) THF, H2O, 20 deg C 2: 100 percent / MnO2 / acetone / 72 h / 20 °C 3: 98 percent / TFA / 15 h / 20 °C 4: 61 percent / propan-1-ol / 72 h / Heating View Scheme

With  polyphosphoric ethyl ester in  chloroform 1 h;  Heating;  Yield given;