CE3+-EXCHANGED MONTMORILLONITE (CE3+-MONT) AS A USEFUL SUBSTRATE-SELECTIVE ACETALIZATION CATALYST

The acetalization of carbonyl compounds with methanol was investigated in the presence of a cation-exchanged montmorillonite (M(n+)-mont; M(n+) = Ce3+, Zr4+, Fe3+, Al3+, Zn2+, Hf, and Na+). Ce3+-mont was found to be the most effective catalyst for substrate-selective acetalization. Cyclohexanones, benzaldehydes, and acid-sensitive 2-furancarboxaldehyde were converted nearly quantitatively to the corresponding acetals in methanol at 25 degrees C in the presence of Ce3+-mont. The substrates were activated by a Lewis acidic Ce3+ cation in the interlayer space on the order of 1 kJ mol(-1) as measured by FT-IR. The turnover number was estimated to be up to 2.6 x 10(3) based on the number of active acid sites in Ce3+-mont.