1.1: 69 percent / conc. HCl / H2O; ethanol / 1.5 h / Heating 2.1: 80 percent / dimethylaminopyridine / CHCl3 / 20 °C 3.1: 95 percent / DBU / tetrahydrofuran / 20 °C 4.1: phosphorus oxychloride / pyridine / 20 °C 4.2: 32 percent / DBU / toluene / Heating View Scheme