Effect of structure and acidity of acid modified clay materials on synthesis of octahydro-2H-chromen-4-ol from vanillin and isopulegol

•Montmorillonite, kaolin and, metakaolin were modified by 0.5 mol/dm3 HCl.•The acid-activated clays were used as catalyst for the Prins cyclization reaction.•Activity of the materials depended on their structural and textural properties.•Activity of the materials depends on their acid–base properties.

The Prins cyclization of (−)-isopulegol with vanillin to form octahydro-2H-chromen-4-ol was studied in the presence of natural layered aluminosilicates modified by 0.5 mol/dm3 HCl, such as montmorillonite, kaolin, and metakaolin obtained by the calcination of kaolin at 650 °C. According to infrared spectroscopy using pyridine as probe molecule, the amount and strength of Brønsted acid sites depend on the type of clay and decrease in the following order HCl-montmorillonite > HCl-kaolin > HCl-metakaolin. The difference in Brønsted acidity and textural properties of clays affected the reaction rate and the selectivity towards octahydro-2H-chromen-4-ol.

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