Prins cyclisation of (–)-isopulegol with benzaldehyde over ZSM-5 based micro-mesoporous catalysts for production of pharmaceuticals

Several ZSM-5 derived micro-mesoporous catalysts were investigated in Prins cyclisation of (–)-isopulegol with benzaldehyde acting as a reactant and a solvent for production of heterocyclic oxygen containing 2H-chromene derivatives including the tetrahydropyran structure and exhibiting biological activity. The investigated catalysts were characterized by nitrogen adsorption, ammonia temperature programmed desorption, adsorption-desorption of pyridine and 2,6-di-tert-butylpyridine with Fourier transform infrared spectroscopic control. For the Prins reaction performed at 70 °C, the highest yield of the desired product, equal to 67% at complete conversion of (–)-isopulegol, was obtained over a micro-mesoporous catalyst containing an optimum amount of strong acid sites and mesopores, being 12 fold larger than the size of the desired product.