Expanding the Horizon of Multicomponent Oxidative Coupling Reaction via the Design of a Unique, 3D Copper Isophthalate MOF-Based Catalyst Decorated with Mixed Spinel CoFe2O4 Nanoparticles

CoFe2O4@SiO2-NH2@MOF-5 magnetic nanocatalyst for the synthesis of biologically active quinazoline derivatives

Metal-organic frameworks (MOFs) offered excellent catalytic activity due to their superior porosity, and high densities of catalytic sites in remarkable specific surfaces. In this research, we prepared a magnetic nanocomposite based on MOF-5 which is one of the prominent and practical structures that have been reported in many applications, and investigated the advantages of it as a catalyst. The multi-functional catalyst was prepared in five steps including (1) preparation of cobalt ferrite nanoparticles (CoFe2O4), (2) surface modification of cobalt ferrite using tetraethyl orthosilicate, (3) surface functionalization using 3-aminopropyl triethoxysilane, (4) preparation of MOF-5, (5) preparation of CoFe2O4@SiO2-NH2@MOF-5 nanocomposite. The resulting catalyst was evaluated by FTIR, FESEM, EDX, XRD, and VSM analyses. The CoFe2O4@SiO2-NH2@MOF-5 nanocomposite was applied as a catalyst for the quinazoline derivatives' synthesis. Various products were prepared with significant yields (90-98%) in short reaction times (20-60 min) without difficult work-up. In addition, the magnetic behavior of the catalyst allows it to be collected and recycled by a magnet and applied for six consecutive cycles without significantly reducing its efficiency. Quinazoline derivatives showed significant biological activities so their antioxidant activity was between 23.7% and 88.9% and their antimicrobial activity was in contradiction of E. coli, S. enterica, L. monocytogenes, S. aureus, and E. faecalis.

Nitrogen-Enriched Biguanidine-Functionalized Cobalt Ferrite Nanoparticles as a Heterogeneous Base Catalyst for Knoevenagel Condensation under Solvent-Free Conditions

Designing efficient, economical heterogeneous catalysts for the Knoevenagel condensation reaction is highly significant owing to the importance of reaction products in industries as well as pharmaceutics. Herein, we have designed and synthesized biguanidine-functionalized basic magnetically retrievable cobalt ferrite nanoparticles (CFNPs) for the synthesis of Knoevenagel condensation products using benzaldehydes and active methylene compounds (malononitrile/ethyl cyanoacetate/cyanoacetamide). Several advanced techniques, such as Fourier transform infrared (FT-IR), thermogravimetric analysis (TGA), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and vibration sample magnetometry (VSM), were utilized to precisely characterize the catalyst. The robust features of the current approach involve outstanding catalytic performance, solvent-free reaction conditions, ease of catalyst retrievability, easy workup procedure, large substrate tolerance, high turnover frequency (TOF) values (up to 486.88 h-1), values of green chemistry metrics such as E-factor (0.15), reaction mass efficiency (RME) value (87.07%), carbon efficiency (93.4%), and atom economy (AE) value (88.10%) close to their ideal values, and recyclability up to eight runs without a considerable reduction in activity, boosting the appeal of this approach from a commercial and ecological point of view.

A simple and straightforward strategy for expedient access to benzoxazoles using chemically engineered 2D magnetic graphene oxide nanosheets as an eco-compatible catalyst

Two-dimensional (2D) graphene oxide nanosheets serve as an excellent support material for immobilizing metal complexes to deal with the drawbacks of homogeneous catalysis. In this work, we report a magnetically retrievable graphene oxide (MGO) based copper nanocatalytic system that has been efficiently exploited for obtaining a series of pharmaceutically and biologically active benzoxazole scaffolds. The nanocatalyst was designed by covalent immobilization of dehydroacetic acid (DHA) onto a magnetic amino-silanized graphene oxide nanosupport which was accompanied by its metallation with copper acetate. The structure of the synthesized MGO hybrid material (Cu@DHA@APTES@MGO) was characterized by numerous physico-chemical techniques such as transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), vibrating sample magnetometry (VSM), elemental mapping, atomic absorption spectroscopy (AAS), thermogravimetric analysis (TGA), Brunauer-Emmett-Teller (BET) surface area analysis and energy-dispersive X-ray fluorescence spectroscopy (ED-XRF). The fabricated architectures exhibited high efficiency for cyclization of 2-aminophenols and β-diketones with wide substrate scope, excellent functional group tolerance, a higher conversion percentage (>98%) and a high turnover number (TON). The exceptional catalytic activity could be attributed to the 2D architecture of graphene oxide which provides space for trapping of reactants between 2D graphitic overlayers and metal surfaces and the reaction proceeds to afford benzoxazole products with moderate to excellent conversion percentages. Notably, this nanocomposite could be recovered easily through an external magnetic force and reused for multiple runs without any appreciable loss in its catalytic efficacy.

Recyclable magnetically retrievable nanocatalysts for C–heteroatom bond formation reactions

During recent years, magnetic separation has proven to be a highly indispensable and sustainable tool for facile separation of catalysts from the reaction medium with the aid of only an external magnetic force that precludes the requirement of energy intensive, solvent based centrifugation or filtration techniques. Extensive research in the area of catalysis has clearly divulged that while designing any catalyst, the foremost features that need to be paid due attention to include high activity, ready recoverability and good reusability. Fortunately, the magnetic nanocatalysts involving a superparamagnetic core material that could comprise of iron oxides such as magnetite, maghemite or hematite or mixed ferrites (CoFe2O4, CuFe2O4) have offered bright prospects of designing the ideal catalysts by proving their efficacy as strong support material that could be further engineered with various tools of nanotechnology and efficiently catalyze various C–heterobond formation reactions. This chapter provides succinct overview of all the approaches utilized for fabricating different types of magnetic nanoparticles and strategies adopted for imparting them durability. The prime forte however remains to exclusively showcase the applications of the various types of magnetic nanocatalysts in C–O, C–N, C–S and miscellaneous (C–Se, C–Te) bond formation reactions which are anticipated to benefit the synthetic community on a broad spectrum by helping them rationalize and analyze the key features that need to be taken into account, while developing these magical nanostructured catalytic systems for boosting the green bond formation reactions/transformations.

Unravelling the catalytic potential of a magnetic CoFe2O4/Cu–ABDC MOF composite in the sustainable synthesis of 2H-indazole motifs

A magnetic CoFe2O4/Cu–ABDC hybrid composite was fabricated for the synthesis of biologically active and pharmacologically significant 2H-indazole scaffolds.

Insights into the catalytic potential of a rationally designed magnetic boron nitride nanosheet supported nickel catalyst for the efficient synthesis of 1,4-dihydropyridines

Magnetically integrated ultrathin h-BN nanosheets based nickel catalyst for the one-pot multicomponent reaction to access 1,4-dihydropyridines.

A sustainable gateway to access 1,8-dioxo-octahydroxanthene scaffolds via a surface-engineered halloysite-based magnetically responsive catalyst

A covalently modified, surface-engineered Cu(ii)@DCH@CPTMS@MHNT nanocatalyst is synthesized, which showed incredible catalytic activity in accessing a library of xanthene scaffolds.

Enhanced catalysis through structurally modified hybrid 2-D boron nitride nanosheets comprising of complexed 2-hydroxy-4-methoxybenzophenone motif

Tuning the structural architecture of the pristine two dimensional hexagonal boron nitride (h-BN) nanosheets through rational surface engineering have proven advantageous in the fabrication of competent catalytic materials. Inspired by the performance of h-BN based nanomaterials in expediting key organic transformations, we channelized our research efforts towards engineering the inherent surface properties of the exclusively stacked h-BN nanosheets through the incorporation of a novel competent copper complex of a bidentate chelating ligand 2-hydroxy-4-methoxybenzophenone (BP). Delightfully, this hybrid nanomaterial worked exceptionally well in boosting the [3 + 2] cycloaddition reaction of azide and nitriles, providing a facile access to a diverse variety of highly bioactive tetrazole motifs. A deep insight into the morphology of the covalently crafted h-BN signified the structural integrity of the exfoliated h-BN@OH nanosheets that exhibited lamellar like structures possessing smooth edges and flat surface. This interesting morphology could also be envisioned to augment the catalysis by allowing the desired surface area for the reactants and thus tailoring their activity. The work paves the way towards rational design of h-BN based nanomaterials and adjusting their catalytic potential by the use of suitable complexes for promoting sustainable catalysis, especially in view of the fact that till date only a very few h-BN nanosheets based catalysts have been devised.

Probing the catalytic activity of highly efficient sulfonic acid fabricated cobalt ferrite magnetic nanoparticles for the clean and scalable synthesis of dihydro, spiro and bis quinazolinones

An exceptionally productive, rapid, simple, and eco-friendly approach for the synthesis of 2,3-dihydroquinazolin-4(1H)-one has been developed utilizing acidic magnetically retrievable cobalt ferrite nanoparticles (CFNP@SO3H).

Recent developments and perspectives in the copper-catalyzed multicomponent synthesis of heterocycles

Heterocyclic compounds have become an inevitable part of organic chemistry due to their ubiquitous presence in bioactive compounds. Copper-catalyzed multicomponent synthesis of heterocycles has developed as the most convenient and facile synthetic route towards complex heterocyclic motifs. In this review, we discuss the advancements in the field of copper-catalyzed multicomponent reactions for the preparation of heterocycles since 2018.

Heterocycles are abundant in several pharmaceutical and naturally occurring compounds. Copper-catalyzed multicomponent reactions are a convenient method for easy access to heterocycles. In this review, we focus on the advancement in this field for the past two years.

Silica-Coated Magnetic-Nanoparticle-Supported DABCO-Derived Acidic Ionic Liquid for the Efficient Synthesis of Bioactive 3,3-Di(indolyl)indolin-2-ones

In this work, biologically significant 3,3-di(indolyl)indolin-2-ones have been synthesized using a silica-coated magnetic-nanoparticle-supported 1,4-diazabicyclo[2.2.2]octane (DABCO)-derived and acid-functionalized ionic liquid as the catalytic entity. The fabricated nanocomposite catalyzes the pseudo-three-component reaction of isatins and indoles explicitly via hydrogen-bonding interactions between substrates and the catalyst. The nanocatalytic system utilizes water as the green reaction medium to obtain a library of indolinones in good to excellent yields under mild reaction conditions. Besides, the catalyst could be easily recovered from the reaction mixture through simple external magnetic forces, which enables excellent recyclability of the catalyst for successive runs without appreciable loss in catalytic activity. Hence, the outcomes of the present methodology make the nanocatalyst a potential candidate for the development of green and sustainable chemical processes.