anthracene-9,10-diimine in ethanol Heating; Yield given;

hydrogenchloride in ethanol 1 h; Heating;

1: 80.5 percent / sodium carbonate / toluene / 0.92 h / 80 - 90 °C 2: 53 percent / acid (trace) / ethanol / 90 - 100 °C / sealed tube, overnight 3: 92 percent / polyphosphoric acid / 1.5 h / 140 °C 4: 88 percent Spectr. / hydrogen chloride / ethanol; CH2Cl2 / 4 h / Irradiation; other reagent (m-xylene, ethanol); intermediate species View Scheme

1: azobenzene-2,2'-diamine in toluene 0.25 h; Inert atmosphere; 2: 2-nitrosoacetanilide in toluene T=60°C; 72 h; Inert atmosphere;