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 γ-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.

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► Magnetic inorganic–organic hybrid nano-organocatalyst was synthesized.
► (2-aminomethyl)phenol moiety supported on [γ-Fe2O3@HAp] is an ideal organocatalyst.
► Nano-catalyst can be magnetically separated and stored for long periods of time.
► 4H-benzo[b]pyrans and dihydropyrano[c]chromenes were synthesized in aqueous media.