Doped Keggin heteropolyacids as catalysts in sulfide oxidation and dihydropyrimidinone synthesis

P. VÁZQUEZ; G. SATHICQ; V. PALERMO; H. THOMAS; G. ROMANELLI

San Juan

Congreso; 43 rd IUPAC World Chemistry Congress; 2011

IUPAC

In this research, we report the preparation of V, Bi and Bi-V Keggin structures where Mo is partially replace by V, Bi, and Bi and V, respectively (H4PMo11VO40, (PMoV); H6PMo11BiO40, (PMoBi); and H5PMo11V0.5Bi0.5O40, (PMoVBi), in H3PMo12O40, (PMo)). These catalysts were well characterized by means of 31P-NMR, UV-visible spectra, FT-IR spectra, thermal analysis, textural properties and potentiometric titration. Mo, V and Bi amounts were estimated by ICP-AES analysis. In addition, the activities of the synthesized catalysts were evaluated in the selective oxidation of sulfides to sulfoxides/sulfones and in the solvent-free multicomponent synthesis of dihydropyrimidinones by the Biginelli method. The incorporation of V, Bi and Bi-V into the structure of PMo increases the catalytic activity (acid and redox catalysts). The correlation between catalytic oxidation performance (sulfide oxidation) and absorption edge energies of HPA catalysts demonstrated that the absorption edge energies could be utilized as a correlation parameter for the reduction potentials (oxidizing powers) of the HPA catalysts, and furthermore, as a probe of the catalytic oxidation performance of HPA catalysts. The two most active catalysts (PMoV and PMoVBi) were supported on aminopropyl-functionalized silica (SiO2NH2). The catalysts were prepared by the equilibrium adsorption technique. They were found to be efficient, ecofriendly and recyclable heterogeneous catalysts for the selective oxidation of diphenylsulfide to the corresponding sulfoxide/sulfone, under mild reaction conditions using aqueous hydrogen peroxide as the oxidant.