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Manipulation of materials is considered as one of the eminent strategies to create desirable catalysts. In this regard, increasing surface area and decreasing dimensions of catalysts have been widely employed on account of effectiveness of these methods. Herein, aerogel form of chitosan as a sustainable, and high aspect ratio compound is employed as a green support for the catalytic purposes. Chitosan aerogel was modified with Fe(II)-phthalocyanine to produce a heterogeneous catalyst for oxidation reactions. The synthesized catalyst promoted the oxidation reactions of alcohols and alkyl arenes to the corresponding aldehydes and ketones using H2O2 as an oxidant in 24 h. The reactions for aliphatic and aromatic alcohols gave turnover numbers of 106–109 at 80 °C and 106–117 at room temperature, respectively. The oxidations of alkyl arenes were carried out with turnover numbers laying in the range of 106–117 at 100 °C. The low toxicity, inexpensive nature, and recycling possibility of the catalyst accompanied by the reaction mild conditions, clean oxidant, and excellent yields offer chitosan aerogel modified with Fe(II)-phthalocyanine as a promising catalyst for oxidation reactions.

The synthesis of heterocyclic compounds containing a bioactive core including the pyridine molecular framework with diverse pharmaceutical and biological activities is noteworthy. Recently chemists have created novel active pharmacophores via MCRs in the presence of nanocatalysts. The application of various types of nanoparticles as catalysts has been studied in the formation of polyfunctionalized pyridines via multicomponent reactions, and is the subject of this review, which concentrates on their application for the synthesis of pyridine derivatives by multicomponent reactions in the last decade (2010–2020).

The present work introduces a one-step and facile hydrothermal procedure as a green process for the first time to synthesize nickel(II) oxide (NiO) nanoparticles. The as-prepared nanomaterials were used as high efficient, low toxic and cost catalyst for the synthesis of some organic compounds. Ni(NO3)2 and some natural extract were used as a surfactant for the first time to synthesis NiO nanomaterials. A high synthesis yield (91%) was obtained for S2. Rietveld analysis affirmed the cubic crystal system of the obtained NiO nanocatalyst. The morphology studies were carried out with the FESEM method and the images revealed a change from non-homogenous to homogenous spherical particles when the Barberryas was used instead of orange blossom surfactant. Besides, the images revealed that the particle size distribution was in the range of 20 to 60 nm. The synthesized catalysts were used for the first time in Biginelli multicomponent reactions (MCRs) for the preparation of 3,4-dihydropyrimidin-2(1H)-ones (DHPMs) under the present facile reaction conditions. High yield (97%) of the final product was achieved at the optimum condensation reaction conditions (Catalyst: 60 mg; temperature: 90 °C and time: 90 min) when ethyl acetoacetate/methyl acetoacetate (1 mmol), benzaldehyde (1 mmol) and urea (1.2 mmol) were used. A kinetic study affirmed pseudo-first-order model for Biginelli reactions followed the pseudo-first-order model.

New 3-(2-aryl-6-nitro-1H-indol-3-yl)quinoline-2,4(1H,3H)-diones were synthesized, and good-to-excellent yields were achieved through one-pot, three-component condensation of aryl glyoxal monohydrates, 4-hydroxyquinolin-2(1H)-one and 3-nitroaniline using sodium alginate and water/ethanol (1:1) as a green solvent at mild reaction conditions. The noticeable features of the present procedure are mild reaction conditions, economic procedure, availability of starting materials, very simple operation, easy isolation, no need for column chromatography separation and using sodium alginate as a natural polysaccharide that is a transition-metal-free, biodegradable, reusable and commercially affordable catalyst. In addition, sodium alginate was recycled up to five times with no remarkable loss of its catalytic properties.

One-pot, three-component reaction of various aryl glyoxal monohydrates, 5-methylisoxazol-3-amine and 4-hydroxyquinolin-2(1H)-one in the presence of a catalytic amount of DBU in H2O/EtOH (1:1) at 50 °C produced the 4-aroyl-5′-methyl-3,4-dihydro-2′H-spiro[[1,3]oxazino[5,6-c]quinoline-2,3′-isoxazol]-5(6H)-one derivatives containing spiro[1,3]oxazino[5,6-c]quinoline moiety in 82–89% yield. The high yields of products, easy work-up, and availability of starting materials are the main advantages of this synthetic strategy.

Pyrazolopyridine and pyrazoloquinoline derivatives were obtained by a one-pot, three-component reaction of arylglyoxals, 3-methyl-1-aryl-1H-pyrazol-5-amines and cyclic 1,3-dicarbonyl compounds in the presence of tetrapropylammonium bromide at 80°C in water through Knoevenagel and Micheal reactions, followed by intramolecular condensation, unexpected dearoylation and oxidation. Mild reaction conditions, high yields, simplicity of work up procedure, starting materials availability and clean product formation are some of the main advantages of this synthetic strategy.

In the present study, high surface area amorphous magnesia was synthesized using walnut shell as a template. This green, simple and useful synthetic protocol was based on the precipitation of magnesium nitrate on biomass in an aqueous phase, followed by calcination. Materials were characterized using X-ray diffraction, scanning electron microscopy (SEM) and N2 adsorption/desorption porosimetry, and the results exhibited high surface area for magnesium oxide. Furthermore, the pore size and surface area of these mesoporous materials can be adjusted by varying the biomass/magnesium nitrate ratio. In addition, magnesium oxide was studied as the support of palladium nanoparticles for the aerobic oxidation of alcohols. We have found out that the resulting Pd-loaded material acts as an effective catalytic system for the aerobic oxidation of benzylic and aliphatic alcohols. The catalyst can be recovered and reused three times without loss of activity. Also, to test the catalytic activity of magnesium oxides as a solid catalyst, we selected Meerwein-Ponndorf-Verley reduction of cyclohexanone with 2-propanol over different magnesium oxides.

Metal oxide nanoporous materials and nanoparticles have main potential uses in several different fields such as nanoelectronics, biomedical science, renewable solar energy, drug-gene delivery, thermal insulation, and so on. On the other hand, it is vital for scientists to understand that agricultural waste biomass-assisted synthesis is less costly, environmentally friendly and renewable strategy, and therefore, agricultural wastes are ideal renewable resources for production of nanostructures as a substitute for toxic chemicals. This present review includes significant recent improvements concerning the synthesis of agricultural waste biomass-assisted metal oxide nanostructures and their application. The goal is to provide a vision for the use of non-extracted agricultural waste, especially lignocellulosic biomass an inexpensive, green, differentiated resource and policy for the synthesis of valuable nanoporous materials and nanoparticles.

In the present study, we have designed and synthesized a new magnetically recoverable, nanocatalyst of Ag/Fe3O4@starch. The successful synthesis and the structure of the nanocatalyst were confirmed and evaluated with several analytical techniques including XRD, EDX, VSM, FT-IR, TEM and TGA. The impact and efficiency of Ag/Fe3O4@starch were successfully investigated in the one-pot synthesis of desired 4H-pyrans and tetrahydro-4H-chromenes using three-component condensation of various aldehydes, malononitrile, and 1,3-diketoesters or cyclic 1,3-diketones. The magnetic nanocatalyst was easily recovered and reused with high catalytic activity even after up to five runs.

Herein we report the syntheses of pyrazolo[3,4- b ]quinolin-5-one and pyrazolo[4′,3′:5,6]pyrido[2,3- d ]pyrimidin-5,7-dione derivatives by cyclocondensation of 1,3-diketones, 3-methyl-1-phenyl-1 H -pyrazole-5-amine and arylglyoxals, under catalyst-free conditions in H 2 O/EtOH at reflux in 65–98% and 73–96% yields respectively. This protocol provides mild reaction conditions, good to high yields, non-catalytic, simple procedures and easy isolation of products to structurally diverse tricyclic pyrazolo[3,4- b ]quinolin-5-one and pyrazolo[4′,3′:5,6]pyrido[2,3- d ]pyrimidin-5,7-dione derivatives, which may have biological and pharmacological activities.

Herein we report the synthesis of some novel indeno[1,2-b]benzofuran derivatives by reaction of ninhydrin with cyclic 1,3-dicarbonyl compounds including cyclopentane-1,3-dione, cyclohexane-1,3-dione, dimedone, 4,4-dimethylcyclohexane-1,3-dione, meldrum's acid, barbituric acid, thiobarbituric acid, 1,3-dimethylbarbituric acid and indane-1,3-dione. We also used tetra-propylammonium bromide (TPAB) as an organocatalyst.

N-formylation of different amines was carried out with formic acid in the presence of the Co3O4 nanoparticles as an efficient, stable heterogeneous catalyst to give the corresponding formamides under solvent-free conditions. This method has advantages over the reported methods such as high yields, mild conditions, easy work-up and short reaction times. The catalyst was characterized by different techniques such as XRD, SEM and FT-IR spectroscopy.

A series of new pyrazolo[5,4-b]quinoline derivatives were synthesized in good yields by tin(II) chloride dihydrate catalyzed cyclocondensation of 5-amino-3-(arylamino)-1H-pyrazole-4-carbonitriles with cyclohexane-1,3-dione or dimedone. The synthetic procedure can be carried out by means of simple operations under convenient solvent­-free conditions.

Ceria (CeO2) nanoparticles (NPs) have been produced from cerium nitrate and walnut shell as a worthless agricultural waste by a thermal decomposition method followed by open air calcination. These NPs further were characterized using powder X-ray diffraction, transmission electron microscopy (TEM), scanning electron microscopy, energy dispersive X-ray spectroscope and Fourier transform infrared spectroscopy. Moreover, particle sizes can be tuned by changing cerium source/biomass ratio. To test the catalytic activity of cerium NPs as a heterogeneous catalyst, we selected three-component synthesis of 3,4-dihydroquinoxalin-2-amine. Also, the efficiency of CeO2 NPs as a support for palladium NPs and subsequent use in aerobic oxidation of alcohols has been investigated. TEM image of a recovered catalyst indicates the formation of 12 nm sized palladium NPs within the cerium oxide NPs. The catalyst is quite effective for the oxidation of primary and secondary benzylic alcohols into their corresponding aldehydes and ketones under atmospheric pressure of air. Oxidation of secondary aliphatic alcohols is performed in oxygen atmosphere.

A novel and one-pot pseudo-four-component reaction between a series of arylglyoxals, malononitrile, 3-methyl-1-phenyl-1H-pyrazol-5-amine, and acetone in the presence of tetrapropylammonium bromide (TPAB) has been developed to synthesize a series of new substituted pyrazolo[3,4-b]pyridines, using water as an environmentally friendly solvent, in high to excellent yields.

The cyclocondensations are performed in molten tin dichloride which acts as both reaction medium and Lewis acid catalyst.