(2015) Fe 3 O 4 @SiO 2 -NH 2 core-shell nanocomposite as an efficient and green catalyst for the multi-component synthesis of highly substituted chromeno [2,3-b]

A novel and simple approach for the efficient and rapid synthesis of pyrano[2,3-c]-pyrazoleshas been accomplished via the four-component condensation reaction of malononitrile, hydrazine hydrate, ethyl acetoacetate, and substituted aldehydes using MIL-53(Fe) metal-organic framework (MOF) as a catalyst in ethanol at room temperature. Recycling studies have shown that the MIL-53(Fe) can be readily recovered and reused six times without significant loss of its activity. The present protocol offers the advantages including short reaction times, simple workup, high yields, elimination of toxic solvents, no chromatographic purification and recoverability of the catalyst. Also, the catalyst was fully characterized by SEM, EDX, FT-IR, XRD, TGA and TEM analysis.

′ -indoline]-trione derivatives from a three-component condensation reaction of 1,3-indandione, aromatic amines and isatins in the presence of a zinc terephthalate metalorganic framework Zn (BDC) MOF as the catalyst under solvent-free conditions. High yields, short reaction times, simple workup and environmentally benign procedure are advantages of this protocol. The Zn (BDC) MOF catalyst can be recovered and reused several times without loss of activity. The catalyst was characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infra red, X-ray powder diffraction and thermal gravimetric analysis. ARTICLE HISTORY

A practical, simple and efficient method for the synthesis of polysubstituted dihydropyridines was described via multicomponent reactions of aldehydes, arylamines, dimethyl acetylenedicarboxylate and malononitrile/ethyl acetoacetate in the presence of Fe 3 O 4 @SiO 2 -NH 2 nanocomposites. The present methodology provides a novel and efficient method for the synthesis of dihydropyridine derivatives with some advantages, such as excellent yields, short reaction times, recoverability and low catalyst loading. The nanomagnetic catalyst could be readily recovered using an external magnet and reused several times without any significant loss in activity. The catalyst was fully characterized by FT-IR, SEM, XRD, EDX and VSM analysis.

In this research, a general synthetic method for the synthesis of 3,4- dihydroquinoxalin-2-amine derivatives was developed using Co3O4@SiO2 nanoparticles under ultrasonic irradiation. Firstly by a simple and green process, Co3O4;@SiO2 nanoparticles were prepared via sonication, and then these nanoparticles were used as an efficient catalyst for the synthesis of 3,4- dihydroquinoxalin-2-amines via three-component reactions of ophenylenediamines (OPDA), diverse ketones and various isocyanides in ethanol under ultrasound irradiation. The combinatorial synthesis was attained for this procedure with applying ultrasound irradiation while making use of ethanol as green ambient. The present approach offers several advantages such as high yields, environmentally benign, simple work-up, excellent yield of products and short reaction times. The nanomagnetic catalyst could be readily recovered using a simple external magnet and reused several times without any significant loss in activity. The catalyst was fully characterized by FT-IR, FE-SEM, XRD, EDX, VSM and TEM analysis.