Abstract
1,4-Naphthoquinones (NQ) is a class of organic compounds with a number of important properties. However, the existing methods of their synthesis either give a low NQ yield or multistage and require a lot of time. In the present work new one-pot process of NQ synthesis from hydroquinone (HQ) and substituted 1,3-dienes at room temperature is proposed. The solution of heteropolyacid H7PMo8V4O40 (HPA-4) is used as a bifunctional (acid and redox) catalyst for this process. The influence of a number of factors on key process parameters has been studied. It is demonstrated that unsubstituted and a number of alkyl substituted NQ with the yields of 50% - 80% and purity of 92% - 99% can be obtained by this method. The results obtained allow to significantly simplify the synthesis of NQ directly from HQ in comparison with the described similar methods.
Highlights
1,4-Naphthoquinones ( NQ) is a class of organic compounds with a number of important properties
The unsubstituted NQ is used for the synthesis of 9,10-anthraquinone, a number of NQ are the regulators of polymerization, inhibitors of corrosion, and stabilizers of transformer oils [1]
We have studied the one-pot synthesis of 9,10-anthraquinone (AQ) and its derivatives from unsubstituted NQ and 1,3-dienes in the presence of high-vanadium solutions of heteropolyacids with empirical formulas H15P4Mo18V7O89 (HPA-7) and H17P3Mo16V10O89 (HPA-10) and hydrophilic organic solvent (1,4-dioxane) [8]
Summary
1,4-Naphthoquinones ( NQ) is a class of organic compounds with a number of important properties. In the first case, the yield of NQ is low and a significant amount of phthalic anhydride forms, and other oxidizers are either toxic, or produce huge wastes Still another way of NQ production is the diene synthesis between p-benzoquinone (BQ) and 1,3-dienes. We have studied the one-pot synthesis of 9,10-anthraquinone (AQ) and its derivatives from unsubstituted NQ and 1,3-dienes in the presence of high-vanadium solutions of heteropolyacids with empirical formulas H15P4Mo18V7O89 (HPA-7) and H17P3Mo16V10O89 (HPA-10) and hydrophilic organic solvent (1,4-dioxane) [8] In this process the solutions of HPA-x that are both strong Brønsted acids and quite strong oxidizers due to the presence of oxocations V(V) play the role of bifunctional catalysts: the acid catalysts of diene synthesis and catalysts of oxidation. In [11] it was shown that in the presence of solutions of HPA-x (where x is the number of atoms of V within the HPA composition) the reaction between HQ and excessive butadiene in the absence of organic solution depending on temperature leads to the mixtures containing NQ, AQ, as well
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