Benzodioxolenes Functionalized with Hydrazone Moiety: Synthesis, Azo-Hydrazone Tautomerism, and Acid-Base Equilibrium

Novel benzodioxolene derivatives with hydrazone moiety were obtained by the reaction of 2,5-di-tert-butyl-3-hydroxy-1,4-benzoquinone with arylhydrazines. It was found that azo-hydrazone prototropic tautomerism depends on the nature of aryl substituent in hydrazone fragment. Moreover, synthesized compounds are sensitive to the acidity of the medium, and the degree of sensitivity is modulated by the acceptor properties of the aryl substituent in hydrazone moiety. The highest sensitivity combined with excellent reversibility was found for hydrazone with a 2,4-dinitrophenyl substituent, showing its potential use as an acid-base indicator in non-aqueous media.