An efficient synthetic method for the heterogenization of bifunctional zwitterionic HEPES catalyst on LDH modified γ-Fe 2 O 3 magnetic nanoparticles (MNPs) was developed to create a novel polar catalytic environment for tandem catalysis. The efficiency of the resulted acid/base bifunctional catalyst (γ-Fe 2 O 3 @Cu 3 Al-LDH/HEPES) was investigated in Biginelli-like synthesis of biologically active pyrazolo [3,4-d]pyrimidines via the cyclocondensation of 3-methyl, 1-phenyl-H1-pyrazole-5-ol with various aromatic aldehydes and urea derivatives in a mixture of water and ethanol (1:1) under reflux conditions. Besides, the desired products were reached with high conversions and powerful reusability. Utilization of simple and mild reaction conditions, hybrid bifunctional catalytic groups, short reaction time, green and safe solvent, high catalytic performance and good recyclability, easy purification of the products, and simple magnetically work-up make this methodology an interesting and effective option in the Biginelli reaction.

A magnetically separable cobalt complex of macrocyclic pseudo-crown ether (PCE) immobilized on magnetic Cu/Al-layered double hydroxide (γ-Fe 2 O 3 @Cu 3 Al-layered double hydroxide (LDH)/PCE-Co) was readily fabricated using a simple four-step postsynthetic modification strategy. This newly prepared nanocomposite was characterized by different chemo-physical approaches, including Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), inductively coupled plasma optical emission spectroscopy (ICP-OES), vibrating sample magnetometer (VSM), X-ray diffraction (XRD), nitrogen adsorptiondesorption isotherms, energy-dispersive X-ray spectroscopy (EDX), and elemental mapping. The catalytic performance of these nanoparticles (NPs) was explored in the synthesis of diverse 1H-chromeno[2,3-b]pyridine-3-carbonitrile derivatives via one-pot three-component reactions under green reaction conditions. Environmentally benign reaction conditions, simple separation, high yields of the reactions, versatility, easy magnetic separation, and reusability for several runs without significant loss of catalytic performance are the key advantages that make this protocol an ideal alternative method for the synthesis of chromene derivatives.

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