Synthesis of octahydro-2H-chromen-4-ol from vanillin and isopulegol over acid modified montmorillonite clays: Effect of acidity on the Prins cyclizationстатья
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Дата последнего поиска статьи во внешних источниках: 9 июня 2015 г.
Аннотация:Two calcium-rich natural layered aluminosilicates containing 90–95 wt.% montmorillonite were chemically
activated using 0.125–3.0 M HCl solutions. Structural and textural properties were characterized by
X-ray diffraction, elemental analysis and N2-adsorption/desorption analyses. According to infrared spectroscopy using pyridine as probe molecule, the amount of Brønsted acid sites increased when increasing
HCl concentration. The catalytic performance of these materials was investigated in the Prins cyclization
of (−)-isopulegol with vanillin to form octahydro-2H-chromen-4-ol, carried out in toluene at 35 ◦C. It was
found that the amount of Brønsted acid sites and the microporosity of the catalysts are key factors for
the control of the reaction rate and the selectivity towards octahydro-2H-chromen-4-ol.