Electrophilic transformations induced by heteropoly acids: Applications and structural studies

The transformations of oxygen-containing compounds and hydrocarbons were studied in the presence of heteropoly acids (H₄[SiMo₁₂O₄₀], H₃[PMo₁₂O₄₀], H₄[SiW₁₂O₄₀] and H₃[PW₁₂O₄₀]), and a salt (Cs_2.5H_0.5[PW₁₂O₄₀]), First, the reactions of oxygen-containing compounds were studied including the transformations of monohydroxy compounds (dehydration, derivatization), aliphatic and diaryl diols (dehydration, rearrangements), and epoxides (ring opening, isomerization). Reactions of hydrocarbons were also investigated, with emphasis on alkylation reactions. As a main conclusion, it was found that selectivities strongly depend on the acid strength of the catalyst and the structure of the organic substrates. In some cases the products were isolated in excellent yield and selectivity to open new applications for organic syntheses and fine chemical production. The catalysts were also studied by spectroscopic (UV-VIS, FT-IR, ESR) and thermoanalytical (DSC) methods.