Zirconium oxide complex-functionalized MCM-41 nanostructure: an efficient and reusable mesoporous catalyst for oxidation of sulfides and oxidative coupling of thiols using hydrogen peroxide

A novel magnetic FSM-16 supported ionic liquid/Pd complex as a high performance and recyclable catalyst for the synthesis of pyrano[3,2-c]chromenes

In this work, Fe3O4@FSM-16/IL-Pd was successfully designed and synthesized via a new procedure of palladium(ii) complex immobilization onto magnetic FSM-16 using an ionic liquid, as a novel heterogeneous nanocatalyst. Multiple techniques were employed to characterize this magnetic nanocatalyst such as Fourier transform infrared spectroscopy (FT-IR), Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), Field Emission Scanning Electron Microscopy (FE-SEM), thermogravimetric analysis (TGA), Transmission electron microscopy (TEM), and Vibrating Sample Magnetometry (VSM). After complete characterization of the catalyst, its catalytic activity was used for the synthesis of pyrano[3,2-c]chromene-3-carbonitriles via the reaction of 4-hydroxycoumarin, aldehyde, and malononitrile under solvent-free conditions. Also, it can be recovered and reused several times without a significant decrease in its catalytic activity or palladium leaching.

Ionic liquid immobilized on modified magnetic FSM-16: an efficient and magnetically recoverable nanocatalyst

In the present article, a nanocomposite was prepared by immobilizing ionic liquid on the magnetic mesoporous FSM-16 with a core-shell structure (Fe3O4@FSM-16-SO3/IL). Subsequently, the structural properties of the synthesized nanocatalyst were characterized and analyzed by various techniques such as XRD, FT-IR, TEM, FE-SEM, BET, VSM, TGA, and EDS. Fe3O4@FSM-16-SO3/IL was used as a recoverable and efficient nanocatalyst for the synthesis of polyhydroquinoline derivatives. The magnetic nanocatalyst showed remarkable stability and reusability and was reused six consecutive times without considerable loss of its activity.

Efficient oxidation of sulfides to sulfoxides catalyzed by heterogeneous Zr-containing polyoxometalate grafted on graphene oxide

In this study, a tri-component composite named Zr/SiW12/GO was meticulously prepared through an ultrasonic-assisted method. This composite incorporates zirconium nanoparticles (Lewis acid), a negatively charged Keggin type polyoxometalate, and graphene oxide, and serves as a remarkable heterogeneous catalyst. The Keggin component plays multiple roles as reducing, encapsulating, and bridging agents, resulting in a cooperative effect among the three components that significantly enhances the catalytic activity. The catalytic performance of Zr/SiW12/GO was thoroughly investigated in the oxidation of sulfides to sulfoxides under mild conditions, employing H2O2 as the oxidant. Remarkably, this composite exhibited exceptional stability and could be effortlessly recovered and reused up to four times without any noticeable loss in its catalytic activity.

Synthesis and characterization of thiophene-derived palladium(ii) complex immobilized on FSM-16 and its application in the novel synthesis of 7-(aryl)-7,12-dihydro-6H-indeno[1,2,4]triazolo[1,5-a]pyrimidine-6-one derivatives

The present study aims at synthesizing a palladium complex with a thiophene-carboimine ligand, supported on FSM-16 as a mesoporous silica support. Firstly, the prepared FSM-16 was modified using 3-aminopropyl group. The imine bond was subsequently formed by condensation of FSM-16-propyl amine with thiophene-2-carbaldehyde. Finally, the imine/thiophene-FSM-16 reacted with PdCl₂ to form PdCl₂-imine/thiophene-FSM-16. The structural and physicochemical properties of the prepared nanocomposite were characterized using FT-IR, TEM, XRD, FE-SEM, EDS, BET, and TGA analyses. PdCl₂-imine/thiophene-FSM-16 exhibited efficient catalytic activity in the synthesis of indeno-1,2,4-triazolo[1,5-a]pyrimidine derivatives via a new three-component reaction between indan-1,3-dione, aromatic aldehydes and 3-amino-1H-1,2,4-triazole in water as the green solvent. Significantly, the heterogeneous catalyst can be easily separated from the reaction mixture and reused in another reaction.

Sulfamic acid pyromellitic diamide-functionalized MCM-41 as a multifunctional hybrid catalyst for melting-assisted solvent-free synthesis of bioactive 3,4-dihydropyrimidin-2-(1H)-ones

This study introduces a practical approach to fabricate a novel hybrid acidic catalyst, namely sulfamic acid pyromellitic diamide-functionalized MCM-41 (MCM-41-APS-PMDA-NHSO₃H). Various techniques such as FTIR, TGA, XRD, BET, FESEM, and EDX were used to confirm its structural characteristics. The efficiency of the new MCM-41-APS-PMDA-NHSO₃H organosilica nanomaterials, as a heterogenous nanocatalyst, was examined in the synthesis of biologically active 3,4-dihydropyrimidin-2-(1H)-one derivatives under solvent-free conditions. It was found that the nanoporous MCM-41-APS-PMDA-NHSO₃H, demonstrating acidic nature and high surface area, can activate all the Biginelli reaction components to afford desired 3,4-dihydropyrimidin-2-(1H)-ones under solvent-free conditions in short reaction time. Furthermore, easy and quick isolation of the new introduced hybrid organosilica from the reaction mixture as well as its reusability with negligible loss of activity in at least five consecutive runs are another advantages of this green protocol.

Enantioselective synthesis of sulfoxide using an SBA-15 supported vanadia catalyst: a computational elucidation using a QM/MM approach

Metal catalyzed asymmetric oxidation of prochiral sulfides is one of the prevailing strategies to produce enantiopure sulfoxides. Keeping in view the reported reactivity of peroxo vanadium complexes towards asymmetric oxidation reactions, this study explores the reactivity of vanadia represented as a VO₄ cluster with CH₃-S-Ph through DFT computations. The mechanism of the oxidation of sulfides to sulfoxides with unsupported VO₄ is thoroughly investigated. The chiral centre in the VO₄ cluster is introduced by grafting it on an SBA-15 support and two conformers of the supported cluster are thus obtained. The study was extended to locate transition states for the reaction of each conformer with CH₃-S-Ph. The large enantiomeric excess obtained from the energy difference of the transition states confirms the formation of enantiopure sulfoxide. Analysis of the computational results provides a rational explanation for the observed enantioselectivity, which is remarkable. The optical stability as well as asymmetry of chiral sulfoxides obtained by the current approach has been further confirmed by locating the planar transition state, through which conversion from one enantiomer to another takes place. The calculations suggest that transition between the two enantiomers of sulfoxide is hampered by sufficiently high inversion barriers.

S–S Bond Formation: Nanocatalysts in the Oxidative Coupling of Thiols

Compounds containing sulfur–sulfur bonds (often called disulfides or more specifically disulfanes) are arguably one of the most valuable functional groups in organic synthetic chemistry. They exist extensively in nature, in which they exhibit important biological activities. Furthermore, a diverse range of natural and synthetic disulfides have been discovered that have many applications as pharmaceutical and agriculture chemicals as well as synthetic intermediates. Since thiols are commercially accessible or easily synthesizable materials and their choice as starting materials is widely reported for the synthesis of organic sulfur compounds, unsurprisingly the oxidative coupling of thiols is the best and simplest route for the preparation of disulfides. In recent times, nanocatalysts have shown excellent catalytic activity and reusability in the oxidation of thiols to disulfides. Herein, we summarize the recently reported breakthroughs in the use of nanocatalysts for the oxidative coupling of thiols to their corresponding disulfides, with the goal of stimulating further progress in this field.

Efficient preparation of boehmite silica dopamine sulfamic acid as a novel nanostructured compound and its application as a catalyst in some organic reactions

Nano-boehmite was prepared in water at room temperature using commercially available materials and applied as supports for the preparation of a new catalyst.