Synthesis of azobenzenes with high reactivity towards reductive cleavage: Enhancing the repertoire of hypersensitive azobenzenes and examining their dissociation behavior

Trifluoromethyl (CF₃), cyano (CN), and nitro (NO₂) groups were demonstrated to be effective acceptors in the molecular design of triple-donor/acceptor-based hypersensitive azobenzenes. The synthesis of these reactive scaffolds requires only two steps with overall yields ranging from 70 to 73%. UV–Vis absorption spectroscopy indicated that in all cases, a few seconds of exposure to mild reducing conditions is sufficient for complete cleavage of the azo bond. Liquid chromatography coupled with mass spectrometry (LC-MS) established the formation of two aniline fragments in the case of the CF₃ and CN-substituted azobenzenes. In the case of the NO₂-substituted compound, however, partial reduction of the nitro group results in the formation of three different anilines.