acetic anhydride 3 h; Heating;

1: 89 percent / Ac2O / 3 h / Heating 2: 99.4 percent / formamide / xylene / 24 h / Heating 3: aq. NH3 / 24 h / 80 °C 4: 9.4 percent / pyridine, POCl3 / 1.5 h / Ambient temperature View Scheme