1: 90 percent / aq. NaHCO3 / dioxane / 2 h / Heating 2: 52 percent / hydrazine hydrochloride; triethylamine / ethanol / 0.25 h / Heating 3: 72 percent / 180 °C 4: 80 percent / SnCl4 / acetonitrile / 5 h / 20 °C 5: 80 percent / NH3 / methanol / 36 h / 20 °C View Scheme

1.1: 90 percent / aq. NaHCO3 / dioxane / 2 h / Heating 2.1: 52 percent / hydrazine hydrochloride; triethylamine / ethanol / 0.25 h / Heating 3.1: 72 percent / 180 °C 4.1: 80 percent / SnCl4 / acetonitrile / 5 h / 20 °C 5.1: 80 percent / NH3 / methanol / 36 h / 20 °C 6.1: POCl3 / various solvent(s) / 0.67 h / 0 °C 6.2: 2 percent / pyrophosphoric acid; tributylamine / dimethylformamide / 0.02 h / 20 °C View Scheme