Sodium alginate: An efficient biopolymeric catalyst for green synthesis of 2-amino-4H-pyran derivatives

Zn complexed on hybrid manganese doped cobalt ferrite nanoparticles covered by silica as a catalyst in the synthesis of 2-amino-4H-pyran and N- arylquinoline derivatives

In the present work, Zn complexed on hybrid manganese doped cobalt ferrite nanoparticles covered by silica were synthesized. These MNPs were characterized using different techniques including Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction analysis (XRD), Field emission-scanning electron micro-scope (FE-SEM), Energy-dispersive X-ray spectroscopy (EDS), Vibration sample magnetometer (VSM), Inductively coupled plasma atomic emission spectroscopy (ICP), Zeta potential and Thermogravimetric analysis (TGA). FE-SEM Images showed uniform spherical shape with rough surfaces and an aggregation in structure of MNPs. A decrease in Ms is visible in VSM analysis due to the increase in particle diameter as a result of loading the organic coating on the surface of the magnetic nanoparticles. According to TGA analysis, the synthesized MNPs have good stability up to 125 °C. The ICP analysis indicates the presence of 0.13 mmol/g zinc on the surface of loaded MNPs. The effect of these prepared MNPs as a catalyst was studied in the synthesis of 2-amino-4H-pyran and N- arylquinoline derivatives. This method provides excellent yield of products with short reaction time, simple purification and easy separation of the catalyst. Furthermore, the reusability of the catalyst during five periods was not associated with a significant decrease in its activity.

A supramolecular catalyst based on sodium alginate and viologen calix[4]resorcinol for the room temperature hydrolysis of paraoxon

Properties of paraoxon, such as poor water solubility, low rate of natural decomposition, ability to accumulate in soil and wastewater, lead to the fact that paraoxon is found in various agricultural products and textiles. In this regard, the search for effective ways of paraoxon degradation becomes an extremely urgent problem, which can be solved by creating catalysts by mimicking paraxonase. In this work, a complex of physicochemical methods was used to study the supramolecular interactions of sodium alginate, which has a calcium-binding ability similar to paraxonase, with viologen calix[4]resorcinol and to reveal the nature of the intermolecular interactions between them resulting in the spontaneous formation of nanoparticles. Before proceeding to the investigation of the binding ability of obtained nanoparticles to paraoxon, the encapsulating effect of nanoparticles on a number of model substrates of different solubility (doxorubicin hydrochloride, quercetin and oleic acid) was studied. The kinetics of paraoxon hydrolysis reaction using these nanoparticles was studied at room temperature in an aqueous medium by spectrophotometric method. The rate of this reaction increases with increasing concentration of stable nanoparticles having hydrophobic domains that ensure paraoxon immobilization. The results obtained allow considering the supramolecular polysaccharide/calixarene system as an effective biomimetic catalyst.

Recyclable mesalamine-functionalized magnetic nanoparticles (mesalamine/GPTMS@SiO2@Fe3O4) for tandem Knoevenagel-Michael cyclocondensation: grinding technique for the synthesis of biologically active 2-amino-4H-benzo[b]pyran derivatives

In the present study, mesalamine-functionalized on magnetic nanoparticles (mesalamine/GPTMS@SiO2@Fe3O4) is fabricated as an efficient and magnetically recoverable nanocatalyst. The as-prepared nanocatalyst was successfully synthesized in three steps using a convenient and low-cost method via modification of the surface of Fe3O4 nanoparticles with silica and GPTMS, respectively, to afford GPTMS@SiO2@Fe3O4. Finally, treatment with mesalamine as a powerful antioxidant generates the final nanocatalyst. Then, its structure was characterized by FT-IR, SEM, TEM, EDX, XRD, BET, VSM, and TGA techniques. The average size was found to be approximately 38 nm using TEM analysis and the average crystallite size was found to be approximately 27.02 nm using XRD analysis. In particular, the synthesized nanocatalyst exhibited strong thermal stability up to 400 °C and high magnetization properties. The activity of the synthesized nanocatalyst was evaluated in the tandem Knoevenagel-Michael cyclocondensation of various aromatic aldehydes, dimedone and malononitrile under a dry grinding method at room temperature to provide biologically active 2-amino-4H-benzo[b]pyran derivatives products in a short time with good yields. The presented procedure offers several advantages including gram-scale synthesis, good green chemistry metrics (GCM), easy fabrication of the catalyst, atom economy (AE), no use of column chromatography, and avoiding the generation of toxic materials. Furthermore, the nanocatalyst can be reused for 8 cycles with no loss of performance by using an external magnet.

Supramolecular Pd@methioine-EDTA-chitosan nanocomposite: an effective and recyclable bio-based and eco-friendly catalyst for the green Heck cross-coupling reaction under mild conditions

Supramolecular palladium(ii) supported on modified chitosan by dl-methionine using an ethylenediaminetetraacetic acid linker (Pd@MET-EDTA-CS) was designed and prepared through a simple procedure. The structure of this novel supramolecular nanocomposite was characterized by different spectroscopic, microscopic and analytical techniques including FTIR, EDX, XRD, FESEM, TGA, DRS, TEM, AA, and BET. The obtained bio-based nanomaterial was successfully investigated, as a highly efficient and green heterogeneous catalyst, in the Heck cross-coupling reaction (HCR) for the synthesis of various valuable biologically active cinnamic acid ester derivatives from the corresponding aryl halides using several acrylates. Indeed, aryl halides containing I or Br survived very well under optimized conditions to afford the corresponding products compared to the substrates with Cl. The prepared Pd@MET-EDTA-CS nanocatalyst promoted the HCR in high to excellent yields and short reaction times with minimum Pd loading (0.0027 mol%) on its structure as well as without any leaching occurring during the process. The recovery of the catalyst was performed by simple filtration and the catalytic activity remained approximately constant after five runs for the model reaction.

Preparation and characterization of the h-BN/Fe3O4/APTES-AMF/CuII nanocomposite as a new and efficient catalyst for the one-pot three-component synthesis of 2-amino-4-aryl(or heteroaryl)-7,7-dimethyl-5-oxo-5,6,7,8-tetrahydro-4H-chromene-3-carbonitriles

The intriguing features of surface-engineered hexagonal two-dimensional boron nitride (h-BN) nanostructures have captivated the immense interest of researchers working in the arena of materials science. Inspired by striking attributes exhibited by h-BN nanosheets as the support material, we devoted our efforts towards synthesizing a novel magnetically retrievable h-BN/Fe₃O₄/APTES-AMF/Cu^II catalytic system, which was then comprehensively characterized using various techniques including SEM, TEM, EDX, SEM-based elemental mapping, ED-XRF, AAS, XRD, FT-IR, VSM, XPS, TGA, and BET. Further, the catalytic potential of h-BN/Fe₃O₄/APTES-AMF/Cu^II nanocomposites was investigated in the one-pot multicomponent coupling reaction to gain access to a library of biologically active 2-amino-4-aryl(or heteroaryl)-7,7-dimethyl-5-oxo-5,6,7,8-tetrahydro-4H-chromene-3-carbonitriles under ambient conditions. In addition, the use of green solvent, facile magnetic recoverability, and reusability of up to six successive runs made this protocol environmentally benign and economical. This work throws light on the development of covalently functionalized 2D-BN nanostructure-based copper catalysts and establishes its significance in furnishing industrially demanding products that would pave the way towards sustainable chemistry.

Optimization of green and environmentally-benign synthesis of isoamyl acetate in the presence of ball-milled seashells by response surface methodology

Ball-milled seashells, as a nano-biocomposite catalyst and natural source of CaCO₃ in its aragonite microcrystalline form with fixed CO₂, was optimized for the synthesis of isoamyl acetate (3-methylbutyl ethanoate) by response surface methodology with a five-level three-factor rotatable circumscribed central composite design. The seashells nano-biocomposite has proved to be an excellent heterogeneous multifunctional catalyst for the green and environmentally-benign synthesis of isoamyl acetate from acetic acid and isoamyl alcohol under solvent-free conditions. A high yield of 91% was obtained under the following optimal conditions: molar ratio of alcohol: acetic acid (1:3.7), catalyst loading (15.7 mg), the reaction temperature (98 °C), and the reaction time (219 min). The outstanding advantages of this protocol are the use of an inexpensive, naturally occurring and easily prepared nano-biocomposite material having appropriate thermal stability and without any modifications using hazardous reagents, lower catalyst loading and reaction temperature, no use of corrosive Bronsted acids as well as toxic azeotropic solvents or water adsorbents, and simplicity of the procedure.

Microfluidic Organ-on-A-chip: A Guide to Biomaterial Choice and Fabrication

Organ-on-A-chip (OoAC) devices are miniaturized, functional, in vitro constructs that aim to recapitulate the in vivo physiology of an organ using different cell types and extracellular matrix, while maintaining the chemical and mechanical properties of the surrounding microenvironments. From an end-point perspective, the success of a microfluidic OoAC relies mainly on the type of biomaterial and the fabrication strategy employed. Certain biomaterials, such as PDMS (polydimethylsiloxane), are preferred over others due to their ease of fabrication and proven success in modelling complex organ systems. However, the inherent nature of human microtissues to respond differently to surrounding stimulations has led to the combination of biomaterials ranging from simple PDMS chips to 3D-printed polymers coated with natural and synthetic materials, including hydrogels. In addition, recent advances in 3D printing and bioprinting techniques have led to the powerful combination of utilizing these materials to develop microfluidic OoAC devices. In this narrative review, we evaluate the different materials used to fabricate microfluidic OoAC devices while outlining their pros and cons in different organ systems. A note on combining the advances made in additive manufacturing (AM) techniques for the microfabrication of these complex systems is also discussed.

Solvent-free mechanochemical multicomponent preparation of 4H-pyrans catalyzed by Cu2(NH2-BDC)2(DABCO) metal-organic framework

4H-pyrans have been prepared through a mechanochemical multicomponent reaction (MCR) of different aldehydes, malononitrile, and various 1,3-dicarbonyl compounds, catalyzed by an amine-functionalized metal-organic framework (MOF) Cu₂(NH₂-BDC)₂(DABCO) as a heterogeneous catalyst with good to excellent yields.

Fe3O4/SiO2 decorated trimesic acid-melamine nanocomposite: a reusable supramolecular organocatalyst for efficient multicomponent synthesis of imidazole derivatives

This article describes supramolecular Fe₃O₄/SiO₂ decorated trimesic acid-melamine (Fe₃O₄/SiO₂-TMA-Me) nanocomposite that can be prepared with features that combine properties of different materials to fabricate a structurally unique hybrid material. In particular, we have focused on design, synthesis and evaluation a heterogeneous magnetic organocatalyst containing acidic functional-groups for the synthesis of biologically important imidazole derivatives in good to excellent yields. The introduced Fe₃O₄/SiO₂-TMA-Me nanomaterial was characterized by different techniques such as FTIR, XRD, EDX, FESEM, TEM, TGA and DTA. As a noteworthy point, the magnetic catalytic system can be recycled and reused for more than seven consecutive runs while its high catalytic activity remains under the optimized conditions.

Sulfamic acid grafted to cross-linked chitosan by dendritic units: a bio-based, highly efficient and heterogeneous organocatalyst for green synthesis of 2,3-dihydroquinazoline derivatives

In this work, novel cross-linked chitosan by the G1 dendrimer from condensation of melamine and toluene-2,4-diisocyante terminated by sulfamic acid groups (CS-TDI-Me-TDI-NHSO₃H), as a bio-based and heterogeneous acidic organocatalyst, was designed and prepared. Also, the structure of the prepared organocatalyst was characterized by Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and thermogravimetric analysis/derivative thermogravimetry (TGA/DTA). Subsequently, the catalytic performance of the biobased and dendritic CS-TDI-Me-TDI-NHSO₃H, as a multifunctional solid acid, was evaluated for the preparation of 2,3-dihydroquinazoline derivatives through a three-component reaction by following green chemistry principles. Some of the advantages of this new protocol include high to excellent yields and short reaction times as well as easy preparation and remarkable catalyst stability of the introduced acidic organocatalyst. The CS-TDI-Me-TDI-SO₃H catalyst can be used for up to five cycles for the preparation of quinazoline derivatives with a slight decrease in its catalytic activity.

Mechanistic Insights into the Selective Synthesis of 4H-Pyran Derivatives On-Water Using Naturally Occurring Alginate from Sargassum muticum: Experimental and DFT Study

The naturally occurring sodium alginate (SA) biopolymer from the Sargassum muticum (Yendo) Fensholt was employed as a green organocatalyst for the synthesis of 4H-pyran derivatives. The naturally extracted macromolecule was fully characterized using different analyses, including nuclear magnetic resonance (NMR), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and Energy Dispersive X-ray Analysis (EDX). The catalytic activity of SA was investigated in the one-pot reaction between aldehydes, malononitrile, and 1,3-dicarbonyl compounds in water at room temperature, and the corresponding 2-amino-3-cyano-4H-pyran derivatives were obtained with good to excellent yields. This organocatalyst was easily separated from the reaction mixture and reused for at least two consecutive cycles without a significant loss of its catalytic activity or selectivity. From the mechanistic point of view, density functional theory (DFT) and NCI analyses were performed for the first time to explain the regioselectivity outcomes for the synthesis of 2-amino-3-cyano-4H-pyran derivatives using SA as a green organocatalyst.

Chitosan-EDTA-Cellulose network as a green, recyclable and multifunctional biopolymeric organocatalyst for the one-pot synthesis of 2-amino-4H-pyran derivatives

In this research, cellulose grafted to chitosan by EDTA (Cs-EDTA-Cell) bio-based material is reported and characterized by a series of various methods and techniques such as FTIR, DRS-UV–Vis, TGA, FESEM, XRD and EDX analysis. In fact, the Cs-EDTA-Cell network is more thermally stable than pristine cellulose or chitosan. There is a plenty of both acidic and basic sites on the surface of this bio-based and biodegradable network, as a multifunctional organocatalyst, to proceed three-component synthesis of 2-amino-4H-pyran derivatives at room temperature in EtOH. The Cs-EDTA-Cell nanocatalyst can be easily recovered from the reaction mixture by using filtration and reused for at least five times without significant decrease in its catalytic activity. In general, the Cs-EDTA-Cell network, as a heterogeneous catalyst, demonstrated excellent catalytic activity in an environmentally-benign solvent to afford desired products in short reaction times and required simple experimental and work-up procedure compared to many protocols using similar catalytic systems.

Collagen-coated superparamagnetic iron oxide nanoparticles as a sustainable catalyst for spirooxindole synthesis

In this work, a novel magnetic organic–inorganic hybrid catalyst was fabricated by encapsulating magnetite@silica (Fe₃O₄@SiO₂) nanoparticles with Isinglass protein collagen (IGPC) using epichlorohydrin (ECH) as a crosslinking agent. Characterization studies of the prepared particles were accomplished by various analytical techniques specifically, Fourier transform infrared (FTIR) analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM), energy-dispersive X-ray spectroscopy (EDS), X-ray powder diffraction (XRD), thermogravimetric analysis (TGA), and Brunauer−Emmett−Teller (BET) analysis. The XRD results showed a crystalline and amorphous phase which contribute to magnetite and isinglass respectively. Moreover, the formation of the core/shell structure had been confirmed by TEM images. The synthesized Fe₃O₄@SiO₂/ECH/IG was applied as a bifunctional heterogeneous catalyst in the synthesis of spirooxindole derivatives through the multicomponent reaction of isatin, malononitrile, and C-H acids which demonstrated its excellent catalytic properties. The advantages of this green approach were low catalyst loading, short reaction time, stability, and recyclability for at least four runs.

Progresses in chitin, chitosan, starch, cellulose, pectin, alginate, gelatin and gum based (nano)catalysts for the Heck coupling reactions: A review

Heck cross-coupling reaction (HCR) is one of the few transition metal catalyzed CC bond-forming reactions, which has been considered as the most effective, direct, and atom economical synthetic method using various catalytic systems. Heck reaction is widely employed in numerous syntheses including preparation of pharmaceutical and biologically active compounds, agrochemicals, natural products, fine chemicals, etc. Commonly, Pd-based catalysts have been used in HCR. In recent decades, the application of biopolymers as natural and effective supports has received attention due to their being cost effective, abundance, and non-toxicity. In fact, recent studies demonstrated that biopolymer-based catalysts had high sorption capacities, chelating activities, versatility, and stability, which make them potentially applicable as green materials (supports) in HCR. These catalytic systems present high stability and recyclability after several cycles of reaction. This review aims at providing an overview of the current progresses made towards the application of various polysaccharide and gelatin-supported metal catalysts in HCR in recent years. Natural polymers such as starch, gum, pectin, chitin, chitosan, cellulose, alginate and gelatin have been used as natural supports for metal-based catalysts in HCR. Diverse aspects of the reactions, different methods of preparation and application of polysaccharide and gelatin-based catalysts and their reusability have been reviewed.

Environmentally adapted bio-oil compounds-derived polyolesters synthesis: Optimization and properties of base fluids

Non-edible bio-oil derived from lignocellulosic biomass could be used as environmentally friendly lubricant-ester base stock for maritime and road-type transportations. However, the use of crude bio-oil with highly oxygenated compounds required further upgrading to yield ester that mimicked the characteristics of Group V base oil (polyolesters). In this study, bio-oil based polyolesters was produced via esterification using green biopolymer alginate acid catalyst (Al-Alg). The bio-oil compounds used were acetic acid (AcA), propionic acid (PrA) and levulinic acid (LA), while polyols such as neopentyl glycol (NPG), trimethylolpropane (TMP) and pentaerythritol (PE) were used. Optimization studies revealed that NPG-PrA ester gave the best ester purity of 100%, with 95% of diester selectivity under optimum conditions of 15 wt% Al-Alg, 8 h, 6:1 PrA:NPG and 140 °C. The produced polyolesters showed potential lube characteristics with viscosity index of 76, kinematic viscosity of 2.3 mm² s^-1 at 40 °C and oxidative induction time of 15 min at 100 °C. Furthermore, a reusability study of the Al-Alg catalyst indicated high NPG-PrA diester selectivity (above 90%) for 8 consecutive cycles. The physico-chemical properties of spent Al-Alg catalyst were also discussed.

Organocatalyzed Heterocyclic Transformations In Green Media: A Review

Background:

Since the discovery of metal-free catalysts or organocatalysts about twenty years ago, a number of small molecules with different structures have been used to accelerate organic transformations. With the development of environmental awareness, to obtain highly efficient scaffolds, scientists have directed their studies towards synthetic methodologies that minimize or preferably eliminate the formation of waste, avoid toxic solvents and reagents and use renewable starting materials as far as possible.

Methods:

In this connection, the organocatalytic reactions providing efficiency and selectivity for most of the transformations have become an endless topic in organic chemistry since several advantages from both practical and environmental standpoints. Organocatalysts contributing to the transformation of reactants into products with the least possible waste production, have been serving the concept of green chemistry.

Results and Conclusion:

Organocatalysts have been classified based on their binding capacity to the substrate with covalent or noncovalent interactions involving hydrogen bonding and electrostatic interaction. Diverse types of small organic compounds including proline and its derivatives, phase-transfer catalysts, (thio)urease, phosphoric acids, sulfones, N-oxides, guanidines, cinchona derivatives, aminoindanol, and amino acids have been utilized as hydrogen bonding organocatalysts in different chemical transformations.

Synthesis, Characterization, and Catalytic Properties of Magnetic Fe3O4@FU: A Heterogeneous Nanostructured Mesoporous Bio-Based Catalyst for the Synthesis of Imidazole Derivatives

In this protocol, Fucoidan (FU), a fucose-rich sulfated polysaccharide extracted from brown algae Fucus vesiculosus was used for in situ preparation of magnetic Fe₃O₄@FU. Nanoco magnetic properties of Fe₃O₄@FU were investigated by energy dispersive X-ray (EDX) spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET) adsorption method, and vibrating sample magnetometer (VSM). The catalytic activity of Fe₃O₄@FU was employed for the synthesis of tri- and tetra-substituted imidazoles through three- and four-component reactions respectively, between benzyl, aldehydes, NH₄OAc and benzyl, aldehydes, NH₄OAc, and amine under reflux in ethanol. It is worth nothing that excellent yields, short reaction times, chromatography-free purification, and environmental friendliness are highlighted features of this protocol.

Cysteic acid grafted to magnetic graphene oxide as a promising recoverable solid acid catalyst for the synthesis of diverse 4H-chromene

4H-chromenes play a significant role in natural and pharmacological products. Despite continuous advances in the synthesis methodology of these compounds, there is still a lack of a green and efficient method. In this study, we have designed cysteic acid chemically attached to magnetic graphene oxide (MNPs·GO-CysA) as an efficient and reusable solid acid catalyst to synthesize 4H-chromene skeletons via a one-pot three components reaction of an enolizable compound, malononitrile, an aldehyde or isatin, and a mixture of water-ethanol as a green solvent. This new heterogeneous catalyst provides desired products with a good to excellent yield, short time, and mild condition. This procedure presents an environmentally friendly approach for the synthesis of a great number of 4H-chromene derivatives.

Development of natural polymeric microcapsules for antimicrobial drug delivery: triclosan loaded chitosan and alginate-based microcapsules

The goal of this work was the development of natural polymeric microcapsules for antimicrobial drug delivery - triclosan loaded alginate and chitosan-based microcapsules for potential coating applications in substrates such as textiles or plastics. Microcapsules containing 2.5% (w/w) or 3% (w/w) triclosan in both core and matrix were synthesized and evaluated by Fourier-transform infrared spectroscopy, scanning electron microscopy, confocal microscopy, differential scanning calorimetry, thermogravimetry, and antimicrobial activity. The microcapsules produced featured spherical and mostly irregularly-shaped surfaces composed by an alginate core in a chitosan outer matrix, as revealed by confocal microscopy, and antimicrobial activity against S. aureus and E. coli with inhibition halos up to 60 mm and 25 mm respectively, granted by a triclosan loading of 61.66%. The thermal analysis suggested that the polymers protected the active substance from temperature-induced degradation. In conclusion, these microcapsules may be applied toward antimicrobial functionalization of plastics, textiles and other materials.

New Hydrogen-Bond-Enriched 1,3,5-Tris(2-hydroxyethyl) Isocyanurate Covalently Functionalized MCM-41: An Efficient and Recoverable Hybrid Catalyst for Convenient Synthesis of Acridinedione Derivatives

A new nano-ordered 1,3,5-tris(2-hydroxyethyl) isocyanurate-1,3-propylene covalently functionalized MCM-41 (MCM-41-Pr-THEIC) was designed and prepared at room temperature through a simple procedure. According to various microscopic, spectroscopic, or thermal methods and techniques, the correlation of the catalytic performance of the hybrid mesoporous MCM-41-Pr-THEIC to its structural characteristics was fully confirmed. The new MCM-41-Pr-THEIC organosilica nanomaterials were successfully investigated as a solid mild nanocatalyst through hydrogen-bonding activation provided by its organic moiety, for the pseudo-four-component condensation of dimedone, aldehydes, and ammonium acetate or p-toluidine to afford the corresponding acridinedione derivatives under green conditions. Furthermore, the introduced nanocatalyst could be reused at least four times with negligible loss of its activity, indicating the good stability and high activity of the new hybrid organosilica.

One-pot synthesis of 2-amino-4H-chromene derivatives by MNPs@Cu as an effective and reusable magnetic nanocatalyst

MNPs@Cu as an effective, recyclable nanocatalyst was prepared and characterized using Fourier transform infrared spectroscopy, thermogravimetric analysis vibrating sample magnetometry, scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction.

Selective and highly efficient synthesis of xanthenedione or tetraketone derivatives catalyzed by ZnO nanorod-decorated graphene oxide

A new and efficient method for the pseudo three-component synthesis of diverse tetraketone or xanthenedione derivatives has been described in the presence of ZnO nanorods decorated graphene oxide.