Determination of the Influence of Water on the Synthesis of Oligoquinones in the Dehydrogenation Reaction of 1,4-Benzoquinone and Hydroquinone With 3,3′,5,5′-Tetra-Tert-Butyl-4,4′-Diphenoquinone

The development of the chemical industry drives the search for new substances with catalytic, biological, or antioxidant activity. A promising class of compounds is oligoaromatic quinones, which show high potential for use as various catalysts, sensors, or biologically active agents. The modern approach to the synthesis of oligoaromatic quinones involves oxidative polycondensation of quinone derivatives in the presence of strong dehydrogenating agents. One such compound with pronounced oxidative activity is 3,3′,5,5′-tetra-tert-butyl-4,4′-diphenoquinone (TTBDFQ), capable of abstracting hydrogen atoms from various donors, including aromatic diols and para-quinones. This article presents results on establishing the role of water in the synthesis of oligoquinones during the dehydrogenation of 1,4-benzoquinone and hydroquinone by TTBDFQ, and on assessing its effect on the stoichiometry and yields of target products. Reactions were carried out in an aqueous-toluene medium and under solvent-free conditions at 200 °C in an autoclave with vigorous stirring. Changes in the concentrations of the reagents were monitored by high-performance liquid chromatography (HPLC). A model experiment with sodium sulfite demonstrates for the first time that, in addition to dehydrogenation of 1,4-benzoquinone or hydroquinone, an intermediate dehydrogenation of water by TTBDFQ occurs. It is shown that water not only participates in the redox process but also plays a key role in oligoquinone formation, since no oligomerization occurs in its absence. The involvement of water in the reaction was corroborated by 1H NMR spectroscopy.