1: 80 percent / SnCl4 / acetonitrile / 5 h / 20 °C 2: 80 percent / NH3 / methanol / 36 h / 20 °C View Scheme

1.1: 80 percent / SnCl4 / acetonitrile / 5 h / 20 °C 2.1: 80 percent / NH3 / methanol / 36 h / 20 °C 3.1: POCl3 / various solvent(s) / 0.67 h / 0 °C 3.2: 2 percent / pyrophosphoric acid; tributylamine / dimethylformamide / 0.02 h / 20 °C View Scheme