Keggin-Type Mixed Polyoxomolybdates Catalyzed Cyclohexanone Oxidation by Hydrogen Peroxide: In Situ IR Pyridine Adsorption

The Baeyer–Villiger Oxidation of Cycloketones Using Hydrogen Peroxide as an Oxidant

Baeyer–Villiger oxidation can synthesize a series of esters or lactones that have essential application value but are difficult to be synthesized by other methods. Cycloketones can be oxidized to lactones using molecular oxygen, peroxy acids, or hydrogen peroxide as an oxidant. Hydrogen peroxide is one of the environmental oxidants. Because of the weak oxidation ability of hydrogen peroxide, Bronsted acids and Lewis acids are used as catalysts to activate hydrogen peroxide or the carbonyl of ketones to increase the nucleophilic performance of hydrogen peroxide. The catalytic mechanisms of Bronsted acids and Lewis acids differ in the Baeyer–Villiger oxidation of cyclohexanone with an aqueous solution of hydrogen peroxide as an oxidant.

Cesium salt of 2-molybdo-10-tungstophosphoric acid as an efficient and reusable catalyst for the synthesis of uracil derivatives via a green route

A solid catalyst, cesium salt of 2-molybdo-10-tungstophosphoric acid (Cs_2.3H_0.7PW₁₀Mo₂O₄₀) named as Cs-3, was synthesized by a simple, cheap, clean, and eco-friendly method. The physicochemical properties of the synthesized catalyst were studied via FTIR spectroscopy, XRD, EDX, ICP-AES, SEM-TEM, and BET techniques. The precursor 2-molybdo-10-tungstophosphoric acid (H₃PW₁₀Mo₂O₄₀) was easily soluble in water and other polar solvents. Moreover, their cesium salts Cs _x H_3-x PW₁₀Mo₂ with Cs content in the range x = 2.0-2.5 were insoluble in water and other polar solvents. The surface area of the precursor (5.483 m² g^-1) increased after partial proton exchange by Cs⁺ ions (111.732 m² g^-1), and all samples with x > 1 were resistant to leaching of active components and can be recycled without obvious loss of activity. This catalyst used for the synthesis of uracil derivatives via a green route under solvent free conditions at 70 °C gives higher yield within a shorter reaction time. The catalyst was found to be more active and reusable over nine runs with a negligible loss of activity.