Azo coupling

An azo coupling is an organic reaction between a diazonium compound and an aniline or a phenol. The reaction product is an azo compound. In this reaction the diazonium salt is an electrophile and the activated arene a nucleophile in an electrophilic aromatic substitution. Azo couplings are important in the production of dyes such as methyl red and pigment red 170.