A new nanocomposite catalyst based on clay‐supported heteropolyacid for the green synthesis of 2,4,5‐trisubstituted imidazoles

Abstract

Intercalation of cetyltrimethylammonium (CTA +) cations within the nanolayers of montmorillonite (MMT) clay followed by reaction with Keggin-type phosphomolybdic acid (PMo) resulted in the synthesis of (CTA) 3 PMo-MMT nanocomposite catalyst. The prepared nanocomposite catalyst was characterized using different physicochemical methods such as Fourier-transform infrared and inductively coupled plasma-optical emission spectroscopies, X-ray diffraction, and nitrogen adsorption-desorption (Brunauer-Emmett-Teller method) analyses. Characterization techniques demonstrated the intercalation of (CTA) 3 PMo species into the nanolayers of MMT. The resulting (CTA) 3 PMo-MMT nanocomposite catalyst efficiently catalyzed the synthesis of 2,4,5-trisubstituted imidazoles under solvent-free conditions. The efficiency is due to the fact that the presence of CTA + species makes the nanocomposite catalyst hydrophobic and facilitates the accessibility of hydrophobic reactants to active sites in the course of the reaction. High activity and selectivity were achieved in the presence of the prepared nanocomposite catalyst. The nanocomposite catalyst was readily isolated from the reaction mixture using simple filtration, washed with ethanol, and recycled five times without a major loss of activity.

Surface Functionalization of Magnetite Nanoparticles with Sulfonic Acid and Heteropoly Acid: Efficient Magnetically Recoverable Solid Acid Catalysts

“…In the presented spectra, the bands at about 3400 and 1630 cm −1 are attributed to the stretching and bending vibrations of surface OH groups, respectively. The existence of magnetite core can be evidenced by observation of two vibrational bands at about 635 and 587 cm −1 . On the other hand, the observed bands at 1102, 802 and 468 cm −1 are assigned to the asymmetric and symmetric stretching vibrations and bending vibration of Si‐O‐Si bonds in silica shell, respectively (Figures b–g).…”

Recent Advances in Facile Liquid Phase Epoxidation of Light Olefins over Heterogeneous Molybdenum Catalysts

“…Masteri Farahani et al . developed a new magnetically recoverable heterogeneous silica coated magnetic nanoparticles (SCMNP) catalyst (SCMNPs‐S‐COO‐MoO 2 ).…”

“…The C=C double bond in cyclic olefins has higher electron donation ability. It is expected to promote the rate of the epoxidation reaction in comparison with terminal olefins, since the reaction is electrophilic addition of electron‐deficient peroxidic oxygen to the olefin C=C double bond as nucleophile …”

“… SEM images of (a) SCMNPs−S‐COO MoO 2 catalyst, (b) γ‐Fe 2 O 3 @C@MoO 3 NPs, (c) MoO 2 NPs, (d) MoO 3 (sal‐phz)/SBA‐15, (e) Mo−CH 3 ‐SA‐NH 2 ‐SBA‐15, (f) MoO 2 Q 2 @PMO‐6 %, (g) MoO 2 Q 2 @PMO‐6 %, (h) Mo‐VPO (coprecipitation method), (i) 1.0 wt %MoO 3 @np‐Au …”

New magnetic supported hydrazone Schiff base dioxomolybdenum (VI) complex: An efficient nanocatalyst for epoxidation of cyclooctene and norbornene

“…Among different inert material, silica is an appropriate choice that not only prevents aggregation and improves chemical and thermal stability but also provides silanol groups for further functionalization . Regarding the application of magnetically separable catalysts, there are several reports that investigate the catalytic role of immobilized Mo complex on magnetic nanoparticles in the oxidation of alkenes …”