An immobilized Schiff base–Mn complex as a hybrid magnetic nanocatalyst for green synthesis of biologically active [4,3-d]pyrido[1,2-a]pyrimidin-6-ones

The immobilization of metal ions on inorganic supports has garnered significant attention due to its wide range of applications. These immobilized metal ions serve as catalysts for chemical reactions and as probes for studying biological processes. In this study, we successfully prepared Fe3O4@SiO2@Mn-complex by immobilizing manganese onto the surface of magnetic Fe3O4@SiO2 nanoparticles through a layer-by-layer assembly technique. The structure of these hybrid nanoparticles was characterized by various analytical techniques, including Fourier transform infrared spectroscopy (FT-IR), powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), vibrating sample magnetometry (VSM), scanning electron microscopy (SEM), and inductively coupled plasma-optical emission spectrometry (ICP-OES). Fe3O4@SiO2@Mn-complex was successfully utilized in the synthesis of biologically active 7-aryl[4,3-d]pyrido[1,2-a]pyrimidin-6(7H)-one derivatives in an aqueous medium, providing environmentally friendly conditions. The desired products were manufactured in high yields (81–95%) without the formation of side products. The heterogeneity of the solid nanocatalyst was assessed using a hot filtration test that confirmed minimal manganese leaching during the reaction. This procedure offers numerous advantages, including short reaction times, the use of a green solvent, the ability to reuse the catalyst without a significant decrease in catalytic activity, and easy separation of the catalyst using an external magnet. Furthermore, this approach aligns with environmental compatibility and sustainability standards.


Introduction
Nanotechnology is poised to revolutionize various technological applications, with nanomaterials playing a pivotal role in numerous elds such as pharmacology, medicine, environmental protection, electronics, and particularly catalysis. 1anocatalysts demonstrate superior catalytic activity compared to conventional catalysts due to their high surface area.Additionally, they possess remarkable chemical stability. 2In recent years, magnetic nanoparticles (MNPs) have gained signicant popularity as a support for homogeneous catalysts.MNPsupported catalysts offer several noteworthy features.First, the use of MNPs as a support enhances the stability and recyclability of the catalyst.The magnetic nature of MNPs enables the catalyst to be easily separated and recovered from reaction mixtures by applying an external magnetic eld.This simplies the purication process and reduces waste generation, making MNP-supported catalysts more environmentally friendly.Additionally, MNP-supported catalysts exhibit high surface area due to their small particle size, which promotes increased catalytic activity.The large surface area facilitates better interaction between the reactants and the catalyst, leading to improved reaction rates and higher conversion efficiencies.][5] Spinel ferrites (MFe 2 O 4 , M: Fe, Zn, Co, Ni, Cd, etc.), with their unique properties and wide range of applications, hold significant importance in the eld of magnetic materials.These materials exhibit high saturation magnetization and coercivity values, making them highly suitable for a wide range of magnetic applications.The utilization of ferrite spheres with a hollow structure extends to various domains, including catalysis, adsorbents, and gas sensors.They nd extensive use in electronic devices, 6 information storage, 7 magnetic resonance imaging (MRI), 8 drug-delivery technology, 9 adsorption, 10 and sensing applications. 11Moreover, they can serve as catalysts in various chemical processes. 12,13The hollow interior provides Nanoscale Advances PAPER a large surface area, allowing for enhanced contact between the catalyst and reactants.Furthermore, the hollow structure allows for easy diffusion of reactants and products within the sphere, facilitating faster reaction rates.Consequently, these spheres have become a focal point of interest among researchers. 7agnetite, also known as iron(II, III) oxide (Fe 3 O 4 ), is a unique type of ferrite that can serve as an excellent magnetic support material for catalysts.It possesses high saturation magnetization, low cost, high chemical stability, and mechanical strength. 8,14,15The high saturation magnetization allows for easy separation of the catalyst from the reaction mixture using an external magnetic eld, simplifying the recovery and recycling process.The low cost of magnetite makes it economically viable for large-scale industrial applications.Metal complexes have been utilized as homogeneous catalysts in a wide array of reactions.However, many of these complexes are costly and precious, and they come with drawbacks such as difficult separation and a decline in catalytic activity over time.0][21][22][23][24][25][26][27] Supported metal complexes offer the advantage of easy separation from reaction mixtures using an external magnetic eld, making them highly efficient and practical for catalytic applications.Furthermore, immobilizing metal complexes on inorganic supports can improve their catalytic performance by creating a stable environment for active sites, leading to improved selectivity and reusability.Furthermore, the development of supported metal complexes on magnetic nanosized inorganic supports represents a promising strategy for overcoming the limitations of traditional homogeneous catalysts and advancing sustainable catalysis processes.
Multicomponent reactions (MCRs) have revolutionized the eld of organic synthesis by enabling the rapid and efficient construction of complex molecules in a single step, saving time and resources. 28,29By utilizing different combinations of starting materials, catalysts, and reaction conditions, researchers can access a wide range of structurally diverse compounds with potential biological activities or unique properties.Moreover, MCRs align well with the principles of green chemistry.Green chemistry aims to minimize environmental impact by designing chemical processes that are sustainable, efficient, and safe.MCRs contribute to this goal by reducing waste generation through atom economy, ensuring that most atoms from the starting materials end up in the nal product.This exibility makes MCRs highly valuable in drug discovery, materials science, and other elds where access to structurally diverse compounds is crucial. 30,31olyfunctionalized heterocyclic moieties are commonly found in the structures of bioactive natural and synthetic lead molecules, as well as in drug candidates that are either already on the market or currently undergoing clinical trials. 32,33These versatile compounds are also prevalent in agrochemicals, cosmetics, dyes, and various other application-oriented materials. 34The abundance of polyfunctionalized heterocyclic moieties in these compounds underscores their importance and potential for further exploration.Natural coumarins and their synthetic analogues are widely recognized for their diverse range of signicant pharmacological and biological properties within O-heterocycles.5][36][37] (Scheme 1) These compounds have immense potential for therapeutic applications in various elds of medicine and research. 37,38One particular class of coumarin derivatives, chromeno [4,3-d]pyrido[1,2-a]pyrimidin-6-ones, stands out due to its distinctive fused ring system.The fusion of chromene, pyridine, and pyrimidine rings results in a threedimensional structure that confers specic chemical and biological activities.][41][42] Water, as a green solvent, offers several advantages in organic synthesis.First, it is abundant, inexpensive, and readily available, making it a sustainable choice for large-scale reactions. 43Additionally, water is non-toxic and non-ammable, ensuring the safety of both researchers and the environment. 44,45The ability of water to form hydrogen bonds with substrates plays a crucial role in accelerating organic reactions.Hydrogen bonding facilitates the dissolution of reactants and enhances their reactivity by stabilizing transition states. 46,47The development of environmentally friendly and sustainable synthetic methodologies has gained signicant attention in recent years. 48,49In line with this, a new organic-inorganic hybrid nanostructure (Fe 3 O 4 @SiO 2 @Mn-complex) was prepared by immobilizing manganese onto the surface of magnetic Fe 3 O 4 @SiO 2 nanoparticles through a layer-by-layer assembly technique.This hybrid nanostructure efficiently catalysed the green synthesis of pharmaceutically interesting chromeno pyridopyrimidines under aqueous conditions (Scheme 2).

Experimental
All chemicals were purchased from Merck Chemical Company.Melting points were determined using ElectroThermal 9100 apparatus.The progress of the reaction was followed by thinlayer chromatography (TLC) on UV active aluminum backed Scheme 1 Biologically active fused coumarin derivatives.

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plates of silica gel (TLC Silica gel 60 F254). 1 H and 13 C NMR spectra were recorded on a Bruker Advance spectrometer at 300 and 75 MHz, respectively in DMSO-d 6 with TMS as an internal standard.IR spectra were reported using a Bruker Alpha using KBr pellets in the range of 400-4000 cm −1 .X-ray diffraction (XRD) was carried out on an X Pert Pro Cu-Ka radiation (l = 0.15406 nm) in the range of Bragg angle 10-80°.The eld emission-scanning electron microscopy (FE-SEM) and energydispersive X-ray spectroscopy (EDS) analyses were performed on a Sigma system, Zeiss Company, Germany.Thermal stability of Fe 3 O 4 @SiO 2 @Mn-complex (Fe 3 O 4 @SiO 2 @Mn-complex) MNPs was studied by thermogravimetric analysis (TGA) on a TGA2 system, Mettler Toledo Company under an N 2 atmosphere at a heating rate of 10 °C min −1 .The magnetic properties of MNPs were studied using a vibration sample magnetometer (VSM) with the model of an LBKFB instrument (Meghnatis Daghigh Kavir).

Preparation of the magnetic Fe 3 O 4 nanoparticles
Fe 3 O 4 MNPs were prepared by the co-preparation method. 14A mixture of FeCl 2 $4H 2 O (5 mmol, 0.99 g), and FeCl 3 $6H 2 O (10 mmol, 2.7 g) and deionized water (50 mL) in a round bottom ask (100 mL) was heated for 1 h at 95 °C under a N 2 atmosphere.Then pH of the reaction was adjusted on pH = 10 using ammonium hydroxide (25%) and heated for another 1 h.The reaction mixture was cooled to room temperature and the obtained black precipitate was separated using a magnet.The precipitate was washed several times with warm deionized water and ethanol (20 mL) and dried in a vacuum oven at 70 °C.
Synthesis of silica-coated MNPs (Fe 3 O 4 @SiO 2 MNPs) Fe 3 O 4 MNPs were coated with a silica layer using the Stöber method. 50A mixture of Fe 3 O 4 MNPs (1 g), EtOH (99%, 4 mL) and deionized water (6 mL) was poured in a round bottom ask (100 mL) and sonicated for 20 minutes.Ammonium hydroxide (25%, 1.5 mL) was added to the solution and sonicated for 20 minutes again.Tetraethyl orthosilicate (TEOS) (1.4 mL) was added to solution and stirred for 12 h under a N 2 atmosphere at room temperature.The black sediment was separated from the reaction using a magnet and washed with deionized water and ethanol several times and dried in a vacuum oven at 70 °C.
Then, 3-aminopropyltrimethoxysilane (APTMS) (0.6 mL) was added and reuxed for 24 h under a N 2 atmosphere.Finally, the precipitate was separated using a magnet, washed with toluene (10 mL), and dried in a vacuum oven at 50 °C. 51eparation of Fe 3 O 4 @SiO 2 @2OH-1NAP nanoparticles A mixture of Fe 3 O 4 @SiO 2 -PrNH 2 MNPs (1 g) and EtOH (10 mL) was sonicated for 20 minutes.Then, 2-hydroxy-1naphthaldehyde (0.3 g, 1.75 mmol) and triethylamine as base (0.8 mL) were added to the solution and reuxed for 24 h under a N 2 atmosphere.The reaction mixture was cooled to room temperature.The sediment was isolated using an external magnet and washed with ethanol three times (15 mL) and dried in a vacuum oven at 50 °C.
Preparation of the hybrid magnetic nanostructure (Fe 3 O 4 @SiO 2 @Mn-complex) Fe 3 O 4 @SiO 2 @2OH-1NAP MNPs (0.5 g) were dispersed in EtOH (10 mL) for 20 minutes.Then, MnCl 2 $4H 2 O solution (2 M, 5 mL) was added to the mixture slowly for 1 hour and stirred for 24 h under a N 2 atmosphere at room temperature.The precipitate was separated using a magnet, washed with EtOH and H 2 O, and dried in a vacuum oven at 50 °C.
General procedure for the synthesis of chromeno [4,3-d]pyrido [1,2-a]pyrimidin-6-one derivatives Fe 3 O 4 @SiO 2 @Mn-complex MNPs (15 mg) were added to a mixture of aromatic aldehydes (1 mmol), 2-aminopyridine (1 mmol) and 4-hydroxycoumarin (1 mmol) in EtOH : H 2 O (1 : 1) (6 mL).The mixture was stirred under ultrasonic waves at room temperature and the progress of the reaction was monitored by thin layer chromatography (TLC).Aer completion of the reaction, the catalyst was separated from the reaction using a magnet.5 mL of water was added to the solution to form the product.The obtained precipitate was ltered and dried at room temperature.

Results and discussion
Preparation and characterization of the magnetic hybrid nanostructure (Fe 3 O 4 @SiO 2 @Mn-complex) Fe 3 O 4 @SiO 2 @Mn-complex was constructed following the procedure outlined in Scheme 3. Initially, Fe 3 O 4 magnetic nanoparticles (MNPs) were prepared using the co-precipitation method.Subsequently, these particles were coated with a layer of silica using the Stöber method, resulting in the formation of Fe 3 O 4 @SiO 2 MNPs.The Fe 3 O 4 @SiO 2 -PrNH 2 nanoparticles were fabricated by functionalization of Fe 3 O 4 @SiO 2 nanoparticles with APTMS.In continuation, a Schiff base ligand was constructed on the surface of MNPs via the condensation of NH 2 groups with 2-hydroxynaphthaldehyde. Finally, Mn was stabilized and immobilized on modied MNPs through the coordination of nitrogen and oxygen atoms.The resulting precipitate was washed with ethanol and dried in a vacuum oven to obtain the nal hybrid nanomaterial (Fe 3 O 4 @SiO 2 @-Mn-complex).Various characterization techniques including FT-IR spectroscopy, X-ray diffraction (XRD), eld emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), thermogravimetric analysis (TGA), vibrating sample magnetometry (VSM), and inductively coupled plasma-optical emission spectrometry (ICP-OES) were used to identify and characterize the prepared nanostructure.
FT-IR spectra of Fe 3 O 4 (a), Fe 3 O 4 @SiO 2 (b), Fe 3 O 4 @SiO 2 @-PrNH 2 (c), Fe 3 O 4 @SiO 2 -PrNH@2OH-1NAP (d), and Fe 3 O 4 @-SiO 2 @Mn-complex (e) are presented in Fig. 1.A broad absorption band is observed in the range of 3000 and 3500 cm −1 , which can be related to the stretching vibrations of the OH and NH groups (Fig. 1a-d).In addition, the absorption band at 1623 cm −1 is related to the OH twisting vibration band (Fig. 1a), which is shied to 1634 cm −1 due to the modication of NPs (Fig. 1e).The Fe-O vibration bands appeared at 628 and 588 cm −1 (Fig. 1a-d).The appearance of absorption bands at 1078, 969, 803 and 448 cm −1 is attributed to the asymmetric stretching, symmetric stretching, in plane bending and rocking modes of the Si-O-Si group, respectively, that conrm the formation of a SiO 2 shell (Fig. 1b).Weak absorption bands are observed at around 2970 cm −1 , which conrm the presence of aliphatic hydrogens aer modication using APTMS (Fig. 1c).In addition, a new band at 1558 cm −1 proves the existence of bending NH (Fig. 1c).The appearance of new absorption bands in the range of 1356-1545 cm −1 can conrm the C]N and C]C bonds in the nanostructure (Fig. 1d and e).Finally, in Fig. 1e, no signicant change was observed, and therefore the presence of manganese in the nanoparticle structure was considered by other techniques.In general, the results prove that the surface of nanoparticles has been successfully modied.

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respectively.These data indicate that the obtained Fe 3 O 4 nanoparticles have a spinel structure and are according to the standard JCPDS (le no.0629-19). 52Also, the formation of peaks at 2q = 70.10°and53.55°can conrm the presence of MnO 2 in the nanostructure. 53he peak of SiO 2 is observed in the range of 2q = 17-20°. 54he XRD patterns prove that the structure of Fe 3 O 4 nanoparticles has been preserved during the functionalization steps.The crystal size was calculated using Scherer's equation (D = 0.9l/b cos q).In this equation, l is the wavelength of copper (0.154 nm), q is the Bragg's angle of the peak with the highest intensity (35.68°), and b is half the height of the peak with the highest intensity.The crystallite size of MNPs calculated from the width of the peak at 2q = 35.68°(311) is 15 nm, which is smaller than the range determined using FE-SEM analysis (Fig. 3).
Scanning electron microscopy (FE-SEM) was applied to check the morphology and size of nanoparticles (Fig. 3a).As can be seen, the prepared nanoparticles have average diameters of 25-35 nm and spherical shapes.The size of nanoparticles obtained from FE-SEM images is larger than that obtained from the XRD patterns, which can be attributed to some accumulation of nanoparticles.The EDX analysis shows the presence of iron (Fe), silicon (Si), oxygen (O), carbon (C), nitrogen (N) and manganese (Mn) elements in the Fe 3 O 4 @SiO 2 @Mn-complex nanostructure (Fig. 3b).Furthermore, the higher intensity of the Si peak compared to the Fe peaks shows that the Fe 3 O 4 nanoparticles have been trapped by the SiO 2 layer.The black spots and grey parts in the TEM image correspond to the Fe 3 O 4 core and silica layer (Fig. 4).Based on the TEM images, the sizes of the catalyst particles were found to be less than 40 nm.The typical thickness of the silica shell was evaluated to be in the range of 5-20 nm.The SEM and TEM images reveal that the size of the catalyst particles falls within the nanometer range.
The thermogravimetric analysis (TGA) was used to study the thermal stability of Fe 3 O 4 @SiO 2 @Mn-complex at 50-600 °C (Fig. 5).The magnetic catalyst shows 14% weight loss in two main steps over the temperature range.The rst stage shows 2% weight loss at T < 150 °C, which can be related to the removal of physically adsorbed water and organic solvents.The second stage shows 9% weight loss in the range of 150 < T < 600 °C, which is attributed to the decomposition of the organic moieties graed on the nanostructure.The exact amount of manganese in Fe 3 -O 4 @SiO 2 @Mn-complex was measured using the ICP-OES technique.Based on ICP-OES analysis, the amount of manganese in the hybrid nanocatalyst was 1.93 × 10 −3 mol g −1 .
Vibrating sample magnetometry was carried out to investigate the magnetic properties of the prepared NPs in a ±15 000 Oe range at room temperature (Fig. 6).The hysteresis loop is S like and shows superparamagnetic behavior for magnetic nanoparticles and no hysteresis phenomenon was observed.The histogram curve provides the main information about saturation magnetization (M s ).As can be seen, the nanoparticles have shown a saturation magnetization (M s ) of about 42 emu g −1 that conrms that Fe 3 O 4 @SiO 2 @Mn-complex MNPs have a suitable M s aer modication during four steps yet.So, this heterogeneous catalyst can be separated easily from the solution by using an external magnet.

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in the synthesis of chromeno [4,3-d]pyrido[1,2-a]pyrimidin-6one derivatives.The condensation reaction of 4-hydroxycoumarin isatin, 4-chlorobenzaldehyde, and 2-aminopyridine was selected as the model reaction.Three important parameters: solvents, catalyst amount, and temperature were optimized and the results are summarized in Table 1.First, the model reaction was carried out in several solvents such as EtOH, H 2 O, EtOH : H 2 O, CH 3 CN, and DMF and under solvent-free conditions.It was found that EtOH : H 2 O (1 : 1) is the best solvent for this reaction (Table 1, entry 4).As can be seen in Table 1, increasing the amount of catalyst from 5 to 15 mg improved the reaction time and efficiency, but, increasing the amount of catalyst to 20 mg did not have a signicant effect on the reaction time and efficiency (Table 1, entries 7-9).Finally, the reaction was examined at temperatures ranging from room temperature to 70 °C (Table 1, entries 3, 10, 11).The use of 15 mg of Fe 3 -O 4 @SiO 2 @Mn-complex as a catalyst in EtOH : H 2 O (1 : 1) as a solvent under ultrasound sonication serves as the best condition with respect to the green nature, clean workup procedure, and high yield for this synthesis.To consider the role of Fe 3 O 4 @SiO 2 @Mn-complex as a catalyst, the model reaction was performed under the same conditions with Fe 3 O 4 , Fe 3 O 4 @SiO 2 @PrNH@2OH-1NAP and without any catalyst (Table 1, entries 11-13).The ndings conrm that the catalytic activity of Fe 3 O 4 @SiO 2 @Mn-complex was improved in comparison to Fe 3 O 4 , and Fe 3 O 4 @SiO 2 @PrNH@2OH-1NAP.Immobilizing Mn metal on the nanostructure improves the reaction rate and product yield.The heterogeneity of the solid nanocatalyst was assessed by passing the model reaction mixture through a preheated lter pad during the hot ltration test.The catalytically active nanoparticles were separated from the reaction by ltration aer 20 minutes.The ltered reaction solution was then allowed to react for 60 minutes under optimal conditions.Reaction analysis and metal measurement in solution indicated minimal manganese leaching during the reaction and a significant decrease in the reaction rate following the hot ltration process.
Aer optimizing the reaction conditions, various aromatic aldehydes with electron-withdrawing or electron-donating substituents were applied under the optimized reaction conditions to determine the efficacy of the catalyst (Scheme 2 and Table 2).For all substrates, the reaction proceeded efficiently to produce the desired chromeno [4,3-d]pyrido [1,2-a]pyrimidin-6one derivatives in high to excellent yields with short reaction times without the formation of side products.The catalytic activity of Fe 3 O 4 @SiO 2 @Mn-complex MNPs for the model reaction was also compared with that reported in the literature (Table 3).These data conrm that the Fe 3 O 4 @SiO 2 @Mncomplex nanostructure is a suitable catalyst for synthesizing the desired corresponding product.
A plausible mechanism for the reaction is proposed in Scheme 4. The process is initiated by the Lewis acid sites of the nanostructure activating the carbonyl group of the aldehyde.This activation leads to the formation of intermediate (I) through a condensation reaction between 4-hydroxycoumarin (1) and the aldehyde (2), resulting in the elimination of a water molecule.Next, 2-aminopyridine (3) performs a nucleophilic attack on intermediate (I), which then undergoes a keto-enol tautomerization to form intermediate (II).To complete the reaction, intermediate (II) undergoes a simple intramolecular ring closure.The desired product resulted from the removal of a water molecule. 39The nanostructure (Fe 3 O 4 @SiO 2 @Mncomplex) possesses high porosity and surface area, which enhances the adsorption and activation of reactant molecules and provides a suitable support for this chemical reaction.Moreover, the presence of Lewis acid sites within the nanostructure can also activate certain bonds within the reactant molecules, making them more susceptible to breaking or rearranging during the reaction process.These activation steps effectively lower the energy barrier for the reactions to occur, accelerating the reaction rates.
The recyclability and reusability properties of the Fe 3 O 4 @-SiO 2 @Mn-complex nanostructure were investigated under optimal conditions in the model reaction.Aer completion of each reaction, the catalyst was easily separated using an external magnet, washed with ethanol, dried in a vacuum oven, and reused in subsequent reactions.As shown in Fig. 7, the recycled catalyst could be reused at least four times without any additional treatment or appreciable reduction in catalytic activity and without any change in its morphology.The product yield decreased by only 4% aer four runs, indicating the high performance of the catalyst.Nearly, quantitative recovery of the catalyst (up to 95%) could be obtained from each run.The consistent structure and activity of the recovered catalyst (Fe 3 -O 4 @SiO 2 @Mn-complex) conrm that the reused nanocatalyst exhibits excellent performance in the synthesis of chromeno Fig. 5 TGA analysis of Fe 3 O 4 @SiO 2 @Mn-complex MNPs.

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[4,3-d]pyrido[1,2-a]pyrimidin-6-one derivatives.We attribute this success to the complexation of Mn with organic ligands and immobilization on an inorganic support that effectively limits the leaching and particle growth of Mn.This unique hybrid nanocatalyst can be reused many times with only a slight decrease in performance.ICP-OES analysis was used to measure the potential Mn leaching into the reaction mixture aer four runs.Aer four  Paper Nanoscale Advances cycles, the manganese content was determined to be 1.87 × 10 −3 mol g −1 .The manganese content in Fe 3 O 4 @SiO 2 @Mncomplex aer four runs was comparable to that in the fresh catalyst (1.93 × 10 −3 mol g −1 ), conrming the negligible leaching of manganese into the reaction mixture.Therefore, the prepared hybrid nanocatalyst has good reusability and stability.

Conclusions
In this study, we have successfully synthesized an organicinorganic hybrid nanostructure by immobilizing a Schiff base ligand onto an inorganic support material, followed by the immobilization of manganese (Fe 3 O 4 @SiO 2 @Mn-complex).The prepared hybrid nanostructure was thoroughly characterized.The utilization of this nanostructure allows for the efficient and selective synthesis of pharmaceutically interesting functionalized ones through a one-pot three-component reaction involving 4hydroxycoumarin, substituted aromatic aldehydes, and 2-aminopyridine in aqueous ethanol under ambient conditions.The desired products were obtained in high yields and within short reaction times.This hybrid nanostructure exhibits high catalytic activity due to the synergistic effects among the organic ligand, Lewis acid, and porosity of the inorganic support.The notable advantages of this protocol include the use of aqueous ethanol as a green solvent, operational simplicity, energy efficiency, short reaction times, high to excellent yields, high atomeconomy, easy separation of the catalyst, reusability, and elimination of the need for tedious column chromatography during product isolation and purication.These aspects align with the principles of green and sustainable chemistry.The interaction between the organic ligand and the inorganic support material creates a distinct microenvironment that enhances catalytic efficiency and selectivity.Nanoscale Advances Paper

Fig. 7
Fig. 7 (a) Recyclability of Fe 3 O 4 @SiO 2 @Mn-complex in the model reaction during four runs.(b) FE-SEM image of the reused nanocatalyst.

Table 3
Comparison of catalytic activity of Fe 3 O 4 @SiO 2 @Mn-complex with those in reported studies for 4a © 2024 The Author(s).Published by the Royal Society of Chemistry Nanoscale Adv., 2024, 6, 2713-2721 | 2719