Abstract
The development of new reagents based on benzopyrylium derivatives with enhanced chemical and analytical properties is of considerable interest, as their preparative synthesis is relatively straightforward and typically involves the condensation of triatomic phenols with β-dicarbonyl compounds. Benzopyrylium derivatives are highly reactive species capable of undergoing redox processes, forming complexes with multivalent metal ions, and participating in acid–base transformations in solution. It is particularly noteworthy that hydroxy-substituted benzopyrylium derivatives can convert into anhydro bases with a quinoid structure upon complex formation. This transformation results in a pronounced bathochromic shift of the absorption band and significantly enhances the contrast and detectability of analytical reactions. This work is devoted to the development of a method for obtaining new 6-substituted derivatives of 7,8-dihydroxy-4-methyl-2-phenylbenzo[b]pyrylium perchlorate, which can be used as complexing reagents for the extraction-spectrophotometric determination of polyvalent metal ions, as well as to reduce the duration and complexity of the synthesis. An approach is proposed, which consists in the condensation of equimolar amounts of 4-alkyl derivatives of pyrogallol and benzoylacetone at boiling for 30–60 min in the presence of perchloric acid, and the formed crystalline products are suitable for use in spectrophotometric analysis and do not require additional complex purification, which leads to a reduction in the complexity and duration of the synthesis by 2–3 times. Seven new 6-substituted derivatives of 7,8-dihydroxy-4-methyl-2-phenylbenzo[b]pyrylium perchlorate were obtained, which were identified by IR, NMR, and mass spectrometry, and their purity and identity were proven by high-performance liquid chromatography.
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