Highly efficient and environmentally benign method for the synthesis of tetrahydrobenzo[b]pyrans using Ca9.5Mg0.5(PO4)5.5(SiO4)0.5F1.5 as a new bio- and nanocatalyst with Brønsted base and Lewis acid properties

Abstract

Nanosized Ca9.5Mg0.5(PO4)5.5(SiO4)0.5F1.5 was used as a biocatalyst for the synthesis of tetrahydrobenzo[b]pyrans derivatives via one-pot three-component reaction of various aldehydes, dimedone and malononitrile. The reactions were easily carried out at 60 °C under mild and heterogeneous conditions. The catalyst was easily synthesized by high-energy ball milling, and the effect of some parameters such as specific surface area, pore volume, particle size, pH and crystallinity degree of the catalyst on the yield and reaction time was studied. The catalyst showed both Bronsted base and Lewis acid properties. The acidic sites were determined by FT-IR spectroscopy of the pyridine adsorption technique at different temperatures. Using a biocatalyst and an environmentally benign procedure, good to high yields of the products and short reaction time were the advantages of the method.