Silica-supported aluminum chloride as catalyst for the tetrahydropyranylation of thymol

The preparation, characterization, and performance of catalysts based on AlCl3 and different silica for the tetrahydropyranylation of thymol are reported. These catalysts were obtained by two procedures: incipient wetness impregnation and functionalization; in addition, the reaction was tested at 20 °C, using toluene as solvent. Thymol is a natural product of the terpene family and is currently used as disinfectant. All silica-supported aluminum chlorides showed catalytic activity and, under these conditions, secondary products were not obtained. From the point of view of conversion and reuse, the best catalysts were SiO2(AR106)-I and SiO2(SG)-F. For the former catalyst, the conversion in its third reuse was 83%, while SiO2(SG)-F presented a conversion of 95% in its second reuse. The catalytic system represents a clean way to obtain the tetrahydropyranylation of phenol using AlCl3 because the catalyst can be recycled.