The first example of reversible C-azo coupling in a series of aromatic and heteroaromatic compounds

Heating of imidazolyl- and phenylazo-naphthols in acetic acid in the presence of p-toluenesulfonic acid and dimethylaniline yields imidazolyl- and phenyl-(p-dimethylamino)azobenzenes, which suggests the intermediacy of the corresponding diazo compounds.