One-pot synthesis of 4H-benzo[b]pyrans and dihydropyrano[c]chromenes using inorganic-organic hybrid magnetic nanocatalyst in water

The synthesized nanocatalyst in this work provides a green and useful method to obtain 4H-benzo[b]pyrans and dihydropyrano[c]chromenes in aqueous media. The catalyst shows environmental benign character, which can be easily prepared, stored, recovered without obvious significant loss of activity. Due to water-resistant and superparamagnetic nano-nature of the catalyst, it could be easily separated by the application of an external magnetic device and reused conveniently. The synthesized inorganic-organic hybrid nanocatalyst has fully been characterized by magnetic, adsorptive and thermal techniques (transmission and scanning electron microscopy (TEM & SEM), Fourier transform spectroscopy infrared (FTIR), thermo gravimetric analysis (TGA), X-ray Diffraction (XRD), Brunauer Emmett Teller (BET) and vibrational sampling magnetometer (VSM)), which reveal of the superparamagnetic nano-nature of the particles. In summary, the magnetically inorganic-organic hybrid nanocatalyst supported on hydroxyapatite encapsulated gamma-Fe2O3 was found to be quite excellent and clean catalytic system for the synthesis of 4H-benzopyrans and 2-amino-5-oxo-4-aryl-4,5-dihydropyrano[3.2-c]chromene-3-carbonitriles. (C) 2012 Elsevier B.V. All rights reserved.