Prospects of application of Mo–V-phosphoric heteropolyacid solutions as bifunctional catalysts for syntheses of anthraquinones and their substituted derivatives

Abstract

The acid-catalyzed condensation of 1,3-butadienes with p-quinones and oxidation of the obtained adducts can be carried out as one-pot process in the presence of aqueous solutions of Mo–V–P-heteropolyacids (HPA) of the general composition HaPzMoyVxOb. These solutions act as bifunctional catalysts, since they simultaneously behave as strong Bronsted acids and fairly strong reversible oxidants. The condensation of 1,4-naphthoquinone (NQ) with 1,3-butadiene in solutions of high-vanadium HPA of the empirical compositions H15P4Mo18V7O89 and H17P3Mo16V10O89 in the presence of water-miscible organic solvents (acetone, 1,4-dioxane) affords 9,10-anthraquinone in a yield of ~70% and purity up to 97% at a complete conversion of NQ. Under similar conditions, the reactions of NQ and substituted 1,3-butadienes afford substituted anthraquinones in the yields up to 90% and purity up to 99%. The catalysts are regenerated with oxygen in an individual step and can be reused.