cerium(IV) triflate; water in acetonitrile T=25°C; 0.5 h;

1: pyridine / 0 deg C, 30 min and 2 h, room t. 2: 84 percent / 1.) DBU, molecular sieves / CH2Cl2 / 20 h / 30 - 35 °C 3: LiN3, molecular sieves / dimethylformamide / 1 h / 150 °C 4: TsOH / CH2Cl2; methanol / 6 h / Ambient temperature View Scheme

1: 100 percent / imidazole / dimethylformamide / 54 h / 20 °C 2: 100 percent / Amberlyst 15-H / methanol / 30 h / 20 °C View Scheme

1: imidazole / dimethylformamide / 3 h / Ambient temperature 2: 80percent acetic acid / 3 h / Ambient temperature View Scheme