1: 77 percent / toluene / 3 h / Heating 2: 90 percent / polyphosphoric acid / 0.33 h / 140 - 145 °C View Scheme

1: 74 percent / various solvent(s) / 1 h / 175 - 180 °C 2: 65 percent / chloranil / xylene / 4 h / Heating 3: 77 percent / toluene / 3 h / Heating 4: 90 percent / polyphosphoric acid / 0.33 h / 140 - 145 °C View Scheme

sodium hydroxide in ethanol 5 h; Heating;