Carbon-based solid acid catalyst was found to be highly efficient, eco-friendly and recyclable heterogeneous catalyst for the multicomponent reaction of dimedone, aromatic aldehydes, and a nitrogen source (ammonium acetate or aromatic amines) under solvent-free conditions, giving rise to 1,8-dioxodecahydroacridines in high yields. The present methodology offers several advantages, such as a simple procedure with an easy work-up, short reaction times, high yields, and the absence of any volatile and hazardous organic solvents.

A green and efficient method for the synthesis of 3,4-dihydropyrimidin-2(1H)-ones and -thiones through one-pot three-component reaction of ethyl acetoacetate, an aryl aldehyde, and urea or thiourea in acetonitrile using silica gel-supported polyphosphoric acid (PPA-SiO2) as catalyst is described. Compared to the classical Biginelli reaction conditions, the present methodology offers several advantages such as high yields, relatively short reaction times, mild reaction condition and a recyclable catalyst with a very easy work up.

Preparation of nanostructured diphosphate Na2CaP2O7. Avoiding of any acid catalysts. The prepared catalyst is reusable and eco-friendly. The method is easy and contains simple experimental procedure.

In this research, a magnetically-recoverable catalyst (NiFe 2 O 4 @SiO 2 -H 3 PMo 12 O 40 ) was prepared by supporting phosphomolybdic acid (H 3 PMo 12 O 40 ) onto silica-coated NiFe 2 O 4 nanoparticles. The prepared sample was characterized by FT-IR, TEM, SEM and VSM techniques and then the catalytic activity of this catalyst was investigated in the synthesis of tri-and tetra-substituted imidazole derivatives. More importantly, the catalyst was easily isolated from the reaction mixture by a magnetic bar and reused at least ten times without significant degradation in its activity.

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A covalently cross‐linked graphene oxide (GO) as a catalyst was prepared by a cross‐linking process using the nucleophilic reaction of zirconium (IV)‐coordinated 5,10,15,20‐tetrakis (aminophenyl)porphyrin (ZrPPh) with carboxyl groups of the edges of GO (GO‐ZrPPh). The chemical structure of catalyst was characterized by different analyses such as FT‐IR, SEM, TEM, EDS, ICP, TGA and UV. All analyses confirm the occurrence of successfully covalent immobilization of ZrPPh on the GO. Also, TEM and SEM images show that ZrPPh has been immobilized in the both of the edges and the basal plane of GO. The activity of the catalyst was studied for the synthesis of 3,4‐dihydropyrimidin‐2(1H)‐ones via Biginelli reaction. The cross‐linked catalyst is able to catalyze the reaction in short reaction times and good to excellent yields.

New Schiff base (SB) functionalized graphene oxide (GO) nanosheets containing phosphomolybdic counter‐anion H2PMo12O40¯ (H2PMo) were successfully prepared by grafting of 3‐aminopropyltriethoxysilane (APTS) on GO nanosheets followed by condensation with benzil and finally reaction with phosphomolybdic acid (H3PMo12O40, denoted as H3PMo) and characterized using Fourier transform infrared (FT‐IR) spectroscopy, field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), particle size distribution, energy‐dispersive X‐ray (EDX) analysis, EDX elemental mapping, and inductively coupled plasma optical emission spectrometry (ICP‐OES). The prepared new nanomaterial, denoted as GO‐SB‐H2PMo, was shown to be an efficient heterogeneous catalyst in one‐pot, three‐component reaction of β‐naphthol, aldehydes, and dimedone, giving high yields of tetrahydrobenzo[a]xanthene‐11‐ones within short reaction times. The catalyst is readily recovered by simple filtration and can be recycled and reused several times with no significant loss of catalytic activity.

A novel nanomagnetic basic catalyst of caesium carbonate supported on hydroxyapatite-coated Ni 0.5 Zn 0.5 Fe 2 O 4 magnetic nanoparticles (Ni 0.5 Zn 0.5 Fe 2 O 4 @HAP-Cs 2 CO 3 ) was prepared. This new catalyst was fully characterized using Fourier transform infrared spectroscopy, transmission and scanning electron microscopy, X-ray diffraction and vibrating sample magnetometry techniques, and then the catalytic activity of this catalyst was investigated in the synthesis of 1H-pyrazolo[1,2-b]phthalazine-5,10-dione derivatives. Also, Ni 0.5 Zn 0.5 Fe 2 O 4 @HAP-Cs 2 CO 3 could be reused at least five times without significant loss of activity and could be recovered easily by applying an external magnet. Thus, the developed nanomagnetic catalyst is potentially useful for the green and economic production of organic compounds.