Fe3+-montmorillonite as a cost-effective and recyclable solid acidic catalyst for the synthesis of xanthenediones

Montmorillonite-catalysed coupling reactions: a green overview

Coupling reactions are widely significant in organic synthesis, and within the green chemistry perspective the utilization of montmorillonite clay as a catalyst offers a viable alternative to traditional coupling protocols. Montmorillonite clay is an effective, eco-friendly, economic and recyclable catalyst, and its heterogeneous nature facilitates easy isolation and reusability. The majority of coupling reactions executed with montmorillonite catalysts offer notable advantages over their homogeneous counterparts, including enhanced efficiency, selectivity, operational simplicity, elimination of toxic solvents and ligands, maintenance of mild reaction conditions, and cost-effectiveness. This review gives a comprehensive summary of the literature to date on coupling reactions catalysed by montmorillonite clay, while also outlining future prospects in this area.

BioMOF-Mn: An Antimicrobial Agent and an Efficient Nanocatalyst for Domino One-Pot Preparation of Xanthene Derivatives

In this paper, a new Mn-based metal-organic framework [UoB-6] was obtained via a one-step ultrasonic irradiation method with the ligand (H₂bdda: 4,4'-(1,4-phenylenebis(azaneylylidene))bis(methaneylylidene))dibenzoic acid. The structural integrity of the synthesized BioMOF-Mn was corroborated by FT-IR, EDX, ICP, XRD, TEM, DLS, FESEM, and BET-BJH analyses. The aerobic oxidative domino reaction of benzyl alcohols or aldehydes with dimedone derivatives was performed in the presence of the UoB-6 catalyst to produce xanthene derivatives in good yields. Hot filtration and Hg poisoning tests proved the heterogeneous nature of the catalyst. Novel synthesized xanthene-based bis-aldehydes were introduced as potent HDAC1 inhibitors according to molecular docking calculations. Finally, the inhibitory activities of Mn-MOF nanoparticles were evaluated on Escherichia coli and Candida albicans. The MIC, MBC, and MFC values were determined from 2048 to 4096 μg·mL^-1 according to antimicrobial susceptibility testing methods. The inhibitory effects of antimicrobial agents can be exacerbated when loaded on BioMOFs.

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.

ChCl: Gly (DESs) Promote Environmentally Benign Synthesis of Xanthene Derivatives and Their Antitubercular Activity

A ChCl: Gly (DESs) promoted environmentally benign method was developed for the first time using the reaction of aryl aldehydes and dimedone to give excellent yields of xanthene analogues. The major application of this present protocol is the use of green solvent, a wide range of substrate, short reaction times, ease of recovery, the recyclability of the catalyst, high reaction yield, and ChCl: Gly as an alternative catalyst and solvent. In addition to this, all the synthesized compounds were evaluated for their in vitro antimycobacterial activity against M. tuberculosis H37Ra (MTB) and M. bovis BCG strains. The compounds 3d, 3e, 3f, and 3j showed significant antitubercular activity against MTB and M. bovis strains with minimum inhibitory concentration (MIC) values of 2.5−15.10 µg/mL and 0.26–14.92 µg/mL, respectively. The compounds 3e, 3f, and 3j were found to be nontoxic against MCF-7, A549, HCT 116, and THP-1 cell lines. All the prepared compounds were confirmed by ¹H NMR and ¹³C NMR analysis.

Incorporation of Keggin-based H3PW7Mo5O40 into bentonite: synthesis, characterization and catalytic applications

The Keggin-based molybdo-substituted tungstophosphoric acid, H3[PW7Mo5O40]·12H2O, were synthesized and incorporated with a bentonite clay by using a wetness impregnation method. The catalysts were characterized using several methods, such as inductively coupled plasma-atomic emission spectroscopy (ICP-AES), Fourier transform infrared spectroscopy (FT-IR), X-ray diffractometry (XRD), scanning electron microscopy energy-dispersive X-ray spectroscopy (SEM-EDS), transmission electron microscopy (TEM), and thermogravimetric and differential thermal analysis (TG-DTA). This extremely active catalytic system provides a green strategy for the synthesis of 1,8-dioxo-octahydroxanthene and 1,8-dioxo-decahydroacridine derivatives under solvent free conditions at 80 °C with a good reaction mass efficiency, effective mass yield, and excellent atom economy. Both the surface acidity and catalytic activity sharply increased after H3[PW7Mo5O40]·12H2O was impregnated with bentonite clay. In addition, the PW7Mo5/bentonite catalyst can be conveniently recovered and reused numerous times without demonstrating a significant loss in activity.

Introduction of a trinuclear manganese(iii) catalyst on the surface of magnetic cellulose as an eco-benign, efficient and reusable novel heterogeneous catalyst for the multi-component synthesis of new derivatives of xanthene

In this work, the new trinuclear manganese catalyst defined as Fe3O4@NFC@NNSM-Mn(iii) was successfully manufactured and fully characterized by different techniques, including FT-IR, XRD, TEM, SEM, EDX, VSM, and ICP analysis. There have been reports of the use of magnetic catalysts for the synthesis of xanthine derivatives. The critical potential interest in the present method include short reaction time, high yields, recyclability of the catalyst, easy workup, and the ability to sustain a variety of functional groups, which give economical as well as ecological rewards. Also, the synthesized catalyst was used as a recyclable trinuclear catalyst in alcohol oxidation reactions at 40 °C. The magnetic catalyst activity of Fe3O4@NFC@NNSM-Mn(iii) could be attributed to the synergistic effects of the catalyst Fe3O4@NFC@NNS-Mn(iii) with melamine. Employing a sustainable and safe low temperature, using an eco-friendly solvent, no need to use any additive, and long-term stability and magnetic recyclability of the catalyst for at least six successive runs are the advantages of the current protocol towards green chemistry. This protocol is a benign, environmentally friendly method for heterocycle synthesis.

Application of cyclohexane-1,3-diones for six-membered oxygen-containing heterocycles synthesis

Cyclohexan-1,3-dione derivatives are versatile scaffolds for the synthesis of a variety of value-added organic molecules including heterocycles and natural products. Six-membered oxygen heterocycles prepared from cyclohexan-1,3-diones are of much importance as they are intermediate for the synthesis of a number of natural products and several other valuable bioactive molecules which shows anti-viral, anti-bacterial, analgesic, antimalarial, anti-inflammatory, anti-allergic, anti-tumor and anti-cancer activities. These advantages have inspired us to write a detailed survey on the newly developed methods which are very essential in the construction of six-membered oxygen heterocycles. Further, the versatility in the chemistry of cyclohexan-1,3-dione and its derivatives is due to the presence of highly active methylene moiety and its active di-carbonyl groups. Recently, reactions of cyclohexane-1,3-dione and its derivatives with other substrates for instance aldehydes, malononitriles, NMSM, chalcones, isatin etc. have been established for the construction of a variety of six-membered oxygen heterocycles. The studies reported in this review article involved the synthesis of six-membered oxygen-containing heterocycles which includes 4H-chromen-5(6H)-one, 2H-xanthen-1(9H)-one, 2H-xanthen-1,8(5H,9H)-dione, 6H-chromen-2,5-dione derivatives and natural products having six-membered oxygen heterocycles from cyclohexane-1,3-dione and its derivatives as one of the substrate.

Fabrication of a Gold-Supported NiAlTi-Layered Double Hydroxide Nanocatalyst for Organic Transformations

This work is mainly focused on the synthesis of an efficient and reusable heterogeneous Au/NiAlTi layered double hydroxide (LDH) nanocatalyst and its applications in the preparation of biologically important xanthene, 1,4-dihydropyridine, polyhydroquinoline, and 4H-pyran derivatives. NiAlTi LDH was designed hydrothermally and then gold was supported over the surface of LDH by using ion-exchange and NaBH4 reduction methods. The synthesized nanocatalyst was physicochemically characterized by X-ray diffractrometry, Fourier-transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, and transmission electron microscopy (TEM). The TEM images confirmed the support of gold nanoparticles over the surface of LDH with a size distribution of 7-9 nm. The well-characterized nanocatalyst was tested for the synthesis of biologically important xanthene, 1,4-dihydropyridine, polyhydroquinoline, and 4H-pyran derivatives. The advantages obtained were excellent yields in a lesser reaction time. Stability and reusability were also accessed; the catalyst was stable even after five cycles. High catalytic efficiency, easy fabrication, and recycling ability of Au/NiAlTi LDH make it a potential catalyst for the synthesis of xanthene, 1,4-dihydropyridine, polyhydroquinoline, and 4H-pyran derivatives.

Calcined Layered Double Hydroxides: Catalysts for Xanthene, 1,4-Dihydropyridine, and Polyhydroquinoline Derivative Synthesis

This work is generally focused on the synthesis of NiFeTi-layered double hydroxides (LDHs) using a hydrothermal route, which were calcined at various temperatures (varying from 200 to 600 °C). The synthesized materials were physicochemically characterized. X-ray diffraction results revealed the loss of the layered structure on calcination resulting in the formation of layered double oxides (LDOs) or mixed metal oxides, which was also supported by Fourier transform infrared studies. Scanning electron microscopy results also show loss of the layered structure and the creation of LDOs on increasing the temperature. These LDOs were tested as the catalysts for the synthesis of biologically significant xanthene, 1,4-dihydropyridine, and polyhydroquinoline derivatives. Among all, NiFeTi LDH calcined at 600 °C proved to be the best catalyst for the synthesis of these derivative compounds under optimized conditions. The advantages obtained were excellent yields in a lesser reaction time. Stability and reusability were also assessed; the catalyst was stable even after five cycles. Furthermore, the memory effect of the obtained NiFeTi CLDH calcined at 600 °C confirms that the material so formed is a calcined state of LDH itself. High catalytic efficiency, easy fabrication, and recycling ability of NiFeTi CLDH calcined at 600 °C make it a potential catalyst for the synthesis of xanthene, 1,4-dihydropyridine, and polyhydroquinoline derivatives.

The Immobilized Copper on Nickel Ferrite: A Magnetically Superior Nanocatalyst for Chemoselective and Knoevenagel Synthesis of Bisdimedones and 1,8-Dioxo-octahydroxanthenes under Solvent-Free Conditions

AIM AND OBJECTIVE

Nowadays, bisdimedones and 1,8-dioxo-octahydroxanthenes are considered as biologically active materials. Due to this, the synthesis of the mentioned materials is the subject of more interest. Although most of the reported methods have their own merits, however, they generally require the use of expensive reagents, hazardous organic solvents, a tedious workup procedure and reduced recyclability of the applied catalyst system. Overcoming of the above mentioned drawbacks, therefore, encouraged us to investigate the capability of nanostructured NiFe2O4@Cu towards the synthesis of bisdimedones and 1,8- dioxo-octahydroxanthenes under green reaction conditions.

MATERIALS AND METHODS

Nanoparticles of NiFe2O4@Cu were prepared via a two-step procedure including the preparation of NiFe2O4 by solid-state grinding of Ni(OAc)2·4H2O and Fe(NO3)3·9H2O in the presence of NaOH followed by the immobilization of Cu(0) on the surface of NiFe2O4 nucleus via hydrazine hydrate reduction of Cu(NO3)2·3H2O.

RESULTS

After the synthesis of NiFe2O4@Cu, the catalytic activity of the Cu-nanocatalyst towards Knoevenagel reaction of aromatic aldehydes with dimedone under different reaction conditions was investigated. The examinations showed that using the molar equivalents of aromatic aldehydes (1 mmol) and dimedone (2 mmol) in the presence of 0.15 g NiFe2O4@Cu under solvent-free conditions chemoselectively afforded structurally different bisdimedone products at 60°C and 1,8-dioxo-octahydroxanthenes at 120°C.

CONCLUSION

In this study, magnetically, nanoparticles of NiFe2O4@Cu were prepared and then characterized using different analyses. The catalytic activity of the prepared Cu-nanocatalyst was also studied towards solvent-free Knoevenagel condensation of aromatic aldehydes with dimedone. All the reactions were carried out within 15-240 min to afford bisdimedone and 1,8-dioxo-octahydroxanthene products in high yields.

Simple and efficient synthesis of 2,2′-arylmethylenebis(3-hydroxy-5,5-dimethyl-2-cyclohexene-1-one) derivatives

Abstract

A simple and efficient method for the synthesis of 2,2′-arylmethylenebis(3-hydroxy-5,5-dimethyl-2-cyclohexene-1-one) derivatives using 4 Å molecular sieves as catalyst is described. This approach offers several advantages such as high yields, mild reaction conditions, easily accessible, and reusable catalyst, and simple work-up procedure.

Graphic abstract

Solvent-Free Preparation of 1,8-Dioxo-Octahydroxanthenes Employing Iron Oxide Nanomaterials

In this study, 1,8-dioxo-octahydroxanthenes were prepared employing a simple, effective and environmentally sound approach utilizing an iron oxide nanocatalyst under solventless conditions. The proposed iron oxide nanomaterial exhibited high product yields, short reaction times and a facile work-up procedure. The synthesized catalyst was also found to be highly stable and reusable under the investigated conditions (up to twelve consecutive cycles) without any significant loss in its catalytic activity.

Arrangement Models of Keggin-Al30 and Keggin-Al13 in the Interlayer of Montmorillonite and the Impacts of Pillaring on Surface Acidity: A Comparative Study on Catalytic Oxidation of Toluene

Acid-base reactivity is a key factor for understanding the interfacial geochemistry of clay minerals. Numerous studies showed the significant role of surface acidity of clay minerals in the geological processes and environmentally related applications. In this work, montmorillonite (Mt) was pillared by polycations of Keggin-Al₁₃ and Keggin-Al₃₀. Arrangement models of Keggin-Al₁₃ and Keggin-Al₃₀ in the interlayer region of Mt were put forward based on the chemical composition analysis, the structural formula calculation of Mt, and the results of powder X-ray diffraction. Ammonia temperature-programmed desorption and diffuse reflectance Fourier transform infrared methods were applied to explore the impacts of pillaring by polycations (Keggin-Al₁₃ and Keggin-Al₃₀) on the surface acidic characteristics of Mt. Results demonstrated that one Keggin-Al₃₀ polycation can affect an area of 9.5 unit cells (from two layers, with 4.7-4.8 unit cells in each layer) in Mt, whereas a Keggin-Al₁₃ polycation controls an area of 7.1 unit cells (from two layers, with 3.5-3.6 unit cells in each layer). Pillaring by polycations could lead to a lot of surface acid sites (1.33 mmol NH₃/g) on Mt with the main type of Bronsted acid sites. The increase of surface acid sites on both Keggin-Al₁₃-pillared Mt (Al₁₃-PILM) and Keggin-Al₃₀-pillared Mt (Al₃₀-PILM) is attributed to the high positive charge and high content of aluminum per unit of polycation, which affects the formation of Bronsted acid sites and structural changes of Mt layers. Catalytic oxidation of toluene provided evidence for the high catalytic activity of Al₃₀-PILM under much lower temperature at 78 °C compared with that of Al₁₃-PILM and Mt at 207 and 285 °C, respectively. The basic finding in this study not only reveals the possible sources of abundant micropores and mesopores in the micro/mesoporous materials of Al₁₃-PILM and Al₃₀-PILM but also provides a reasonable mechanism for the formation of abundant Bronsted surface acid sites on these two types of pillared materials. The novel Al₃₀-PILM with an excellent micro/mesoporous structure and extremely high thermal stability also exhibits a potential ability in the application of heterogeneous acid catalysis.

Immobilized copper-layered nickel ferrite on acid-activated montmorillonite, [(NiFe2O4@Cu)(H+-Mont)], as a superior magnetic nanocatalyst for the green synthesis of xanthene derivatives

In this study, the immobilization of copper-layered nickel ferrite on the surface and in the cavities of acid-activated montmorillonite (H⁺-Mont) was investigated. In this context, magnetic nanoparticles (MNPs) of NiFe₂O₄ as the prime magnetic cores were prepared. Next, through the reduction of Cu²⁺ ions with sodium borohydride, the nanoparticles of Cu⁰ were immobilized on the nanocore-surface of NiFe₂O₄, and the constituent NiFe₂O₄@Cu MNPs were obtained. Moreover, through the activation of montmorillonite K10 (Mont K10) with HCl (4 M) under controlled conditions, the H⁺-Mont constituent was prepared. The nanostructured NiFe₂O₄@Cu was then intercalated within the interlayers and on the external surface of the H⁺-Mont constituent to afford the novel magnetic nanocomposite (NiFe₂O₄@Cu)(H⁺-Mont). The prepared clay nanocomposite was characterized using FTIR spectroscopy, SEM, EDX, XRD, VSM and BET analyses. The obtained results showed that through acid-activation, the stacked-sheet structure of Mont K10 was exfoliated to tiny segments, leading to a significant increase in the surface area and total pore volume of the H⁺-Mont constituent as compared to those of montmorillonite alone. SEM analysis also exhibited that the dispersion of NiFe₂O₄@Cu MNPs in the interlayers and on the external surface of acid-activated montmorillonite was carried out successfully, and the nanoparticle sizes were distributed in the range of 15–25 nm. The BET surface analysis also indicated that through the immobilization of NiFe₂O₄@Cu MNPs, the surface area and total pore volume of the H⁺-Mont system were decreased. The catalytic activity of (NiFe₂O₄@Cu)(H⁺-Mont) was further studied towards the synthesis of substituted 13-aryl-5H-dibenzo[b,i]xanthene-5,7,12,14(13H) tetraones 3(a–k) and 3,3,6,6-tetramethyl-9-aryl-3,4,5,6,7,9-hexahydro-1H-xanthene-1,8(2H) diones 5(a–k)via the pseudo-one-pot three-component cyclocondensation of 2-hydroxy-1,4-naphthoquinone (Lawsone)/dimedone and aromatic aldehydes in a mixture of H₂O–EtOH (1 : 1 mL) as a green solvent at 80–90 °C. The (NiFe₂O₄@Cu)(H⁺-Mont) MNPs can be easily separated from the reaction mixture by an external magnetic field and reused for seven consecutive cycles without significant loss of catalytic activity.

In this study, the catalytic activity of the prepared (NiFe₂O₄@Cu)(H⁺-Mont) MNPs was studied towards the synthesis of dibenzo[b,i]xanthene tetraones 3(a–k) and hexahydroxanthene diones 5(a–k).

Natural phosphate-supported Cu(ii), an efficient and recyclable catalyst for the synthesis of xanthene and 1,4-disubstituted-1,2,3-triazole derivatives

Cu(NO3)2 supported on natural phosphate, Cu(ii)/NP, was prepared by co-precipitation and applied as a heterogeneous catalyst for synthesizing xanthenes (2-3 h, 85-97%) through Knoevenagel-Michael cascade reaction of aromatic aldehydes with 1,3-cyclic diketones in ethanol under refluxing conditions. It was further used for regioselective synthesis of 1,4-disubstituted-1,2,3-triazoles (1-25 min, 95-99%) via a three-component reaction between organic halides, aromatic alkynes and sodium azide in methanol at room temperature. The proposed catalyst, Cu(ii)/NP, was characterized using X-ray fluorescence, X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, Brunauer-Emmett-Teller, Barrett-Joyner-Halenda and inductively coupled plasma analyses. Compared to other reports in literature, the reactions took place through a simple co-precipitation, having short reaction time (<3 hours), high reaction yield (>85%), and high recyclability of catalyst (>5 times) without significant decrease in the inherent property and selectivity of catalyst. The proposed protocols provided significant economic and environmental advantages.

Fur-Imine-Functionalized Graphene Oxide-Immobilized Copper Oxide Nanoparticle Catalyst for the Synthesis of Xanthene Derivatives

Fur-imine-functionalized graphene oxide-immobilized copper oxide nanoparticles (Cu(II)-Fur-APTES/GO) are synthesized and found to be a cost-effective, efficient, and reusable heterogeneous nanocatalyst for the preparation of pharmaceutically important xanthene derivatives under greener solvent conditions. Cu(II)-Fur-APTES/GO exhibits excellent result in the synthesis of xanthenes with reduced reaction time (25-50 min) and higher yields (up to 95%) and has a simple procedure, ease of product separation, and no byproducts. Moreover, the nanocatalyst has a Cu loading of 13.5 at. % over functionalized GO which is far superior than the already known metal-based heterogeneous catalysts. The newly synthesized catalyst has been characterized by various physiochemical techniques such as X-ray photoelectron spectroscopy, X-ray diffraction, energy-dispersive X-ray, Raman spectroscopy for structural characterization, field emission scanning electron microscopy and high-resolution transmission electron microscopy for morphological characterization. The catalyst showed admirable recyclability up to five consecutive runs, and there was no appreciable loss in catalytic efficiency.

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.

Greener Route for Synthesis of aryl and alkyl-14H-dibenzo [a.j] xanthenes using Graphene Oxide-Copper Ferrite Nanocomposite as a Recyclable Heterogeneous Catalyst

A facile, efficient and environmentally-friendly protocol for the synthesis of xanthenes by graphene oxide based nanocomposite (GO-CuFe2O4) has been developed by one-pot condensation route. The nanocomposite was designed by decorating copper ferrite nanoparticles on graphene oxide (GO) surface via a solution combustion route without the use of template. The as-synthesized GO-CuFe2O4 composite was comprehensively characterized by XRD, FTIR, Raman, SEM, EDX, HRTEM with EDS mapping, XPS, N2 adsorption-desorption and ICP-OES techniques. This nanocomposite was then used in an operationally simple, cost effective, efficient and environmentally benign synthesis of 14H-dibenzo xanthene under solvent free condition. The present approach offers several advantages such as short reaction times, high yields, easy purification, a cleaner reaction, ease of recovery and reusability of the catalyst by a magnetic field. Based upon various controlled reaction results, a possible mechanism for xanthene synthesis over GO-CuFe2O4 catalyst was proposed. The superior catalytic activity of the GO-CuFe2O4 nanocomposite can be attributed to the synergistic interaction between GO and CuFe2O4 nanoparticles, high surface area and presence of small sized CuFe2O4 NPs. This versatile GO-CuFe2O4 nanocomposite synthesized via combustion method holds great promise for applications in wide range of industrially important catalytic reactions.

A unique opportunity for the utilization of glass wastes as a resource for catalytic applications: toward a cleaner environment

n-glass-waste-SO₃H at the service of catalytic application.