86692-97-9Relevant academic research and scientific papers
Catalytic way of transforming 2,3-dimethylphenol to para-quinone with the use of vanadium-containing heteropoly acids
Rodikova, Yulia A.,Zhizhina, Elena G.,Pai, Zinaida P.
, p. 216 - 224 (2018)
2,3-Dimethyl-p-benzoquinone (2,3-Me2BQ) is a valuable chemical that is applied as a soft oxidizing and dehydrogenating agent and also as a synthon in preparing different complex products including pharmaceutical and biochemical substances. Keggin- and modified-type aqueous solutions of Mo-V-phosphoric heteropoly acids (Mo-V-P HPAs) with the gross compositions H3+xPMo12-xVxO40 (HPA-x) and HaPzMoyVx’Ob (HPA-x’), respectively, possessing high oxidation potential and simplicity of regeneration can serve as effective soft oxidants for obtaining such para-quinone from 2,3-dimethylphenol (2,3-Me2P). The synthesized HPA catalysts with different vanadium content were characterized by a number of analysis techniques, such as 31P and 51V NMR spectroscopy, potentiometry, titrimetry, and pH measurement. It was found that the predominant formation of 2,3-Me2BQ instead of corresponding diphenoquinone (DPQ) at one-electron oxidation is achieved by a consecutive optimization of reaction conditions, the most important among them being organic solvent and molar ratio of vanadium(V) to substrate. As was shown, the substitution of HPA-x by HPA-x’ allows one to increase the quinone selectivity and to decrease the optimal molar ratio of vanadium(V) to substrate. The highest yield of the desired quinone (97%) at total substrate conversion was obtained by using the biphasic water-benzene system at molar vanadium(V) to substrate ratio of 12. The temperature of 50 °C and an inert atmosphere were established to be the optimal reaction conditions. The aqueous HPA-10′ solution including the highest content of VO2+ ions proved to be the most efficient catalyst among investigated HPAs. Carrying out catalyst regeneration at a separate stage provides the preservation of its activity and selectivity at the initial level for at least ten cycles.
Oxidative Coupling of Phenols. Part 9. The Role of Steric Effects in the Oxidation of Methyl-substituted Phenols
Armstrong, David R.,Cameron, Colin,Nonhebel, Derek C.,Perkins, Peter G.
, p. 581 - 586 (2007/10/02)
MINDO/3 calculations indicate that for the coupling of 3,5-dimethylphenoxyl radicals the non-bonded methyl-methyl interactions cause the energy difference between the staggered (1b) and eclipsed (2b) geometries of approach to be greater than in the analogous coupling of phenoxyl radicals.The preferential and exclusive formation of the ortho-ortho-coupled products from the respective oxidations of 2,3-dimethylphenol and 2,3,5-trimethylphenol with di-t-butyl peroxide also support a mechanism, which proceeds via a staggered transition state.
