Transvinylation of 4- and 5-Nitropyrazoles with Vinyl Acetate in the Presence of Mercury Acetate Immobilized on Poly(vinylazole) Substrates

In this article, we aim to use polyvinylazoles as a support for mercury acetate, which can be used as a heterogeneous catalyst in transvinylation reactions for the synthesis of vinyl derivatives of azoles. The transition from a homogeneous to a heterogeneous system in transvinylation reactions allows for the easy separation of the catalyst from the reaction mixture and its reuse, which thereby reducing mercury salt pollution in wastewater. Cross-linked polyvinylazoles, obtained through radical copolymerization of vinyltriazole and vinylimidazole with divinylbenzene, were used as a support. Subsequently, these cross-linked polymers were heated in a mixture of benzene and acetic acid with mercury oxide. The amount of mercury acetate in the obtained complex is 60–65%. The structure of the obtained complexes was confirmed by IR spectroscopy, and they were tested as heterogeneous catalysts in transvinylation reactions in the azole-vinyl acetate system. It has been shown that the obtained heterogeneous catalysts can be successfully used (approximately six times) in selected transvinylation reactions. The structure of the obtained vinylazoles was confirmed by IR and NMR ¹H and ¹³C spectroscopic methods.