H5PW10V2O40@VOx/SBA-15-NH2 catalyst for the solventless synthesis of 3-substituted indoles

Photofixation of N2 to ammonia utilizing Ni@TPP-HPA nanocomposite under visible-light illumination

The production of ammonia as an important raw material in the chemical, agricultural, and food industries has been always a significant concern. However, conventional ammonia production methods require high energy consumption and costs. The photocatalytic rotes use green light sources and cost-effective photocatalysts to obtain ammonia from water under aerobic conditions and preventing production of greenhouse gases in the environment. To produce an effective heterogeneous catalyst, a new tetraphenylporphyrin-heteropolyacid (TPP-HPA) nanohybrid material is synthesized and loaded onto Ni nanoparticles in this work. Then, FE-SEM, EDS, XRD, and FT-IR analyses were applied to characterize the prepared nanohybrid material Ni@TPP-HPA. After that, the new inorganic-organic nanohybrid photocatalyst was introduced as an effective, environmental friendly, and recyclable mediator for N2 photofixation. The results showed that Ni@TPP-HPA is a good photocatalyst for the N2 fixation reaction and can be easily recycled without losing its activity for at least five runs. The Ni@TPP-HPA nanocomposite demonstrated the maximum ammonia generation by 2760 μmol L-1 g-1 under mild conditions when using methanol as a hole scavenger. Additionally, effects of solvent type, temperature, reaction time, irradiation source, solution pH, and other electron scavengers on the rate of NH4+ production were investigated and discussed.

Recent Applications of Heteropolyacids and Related Compounds in Heterocycle Synthesis. Contributions between 2010 and 2020

Over the past two decades, polyoxometalates (POM) have received considerable attention as solid catalysts, due to their unique physicochemical characteristics, since, first, they have very strong Bronsted acidity, approaching the region of a superacid, and second, they are efficient oxidizers that exhibit rapid redox transformations under fairly mild conditions. Their structural mobility is also highlighted, since they are complex molecules that can be modified by changing their structure or the elements that compose them to model their size, charge density, redox potentials, acidity, and solubility. Finally, they can be used in substoichiometric amounts and reused without an appreciable loss of catalytic activity, all of which postulate them as versatile, economic and ecological catalysts. Therefore, in 2009, we wrote a review article highlighting the great variety of organic reactions, mainly in the area of the synthesis of bioactive heterocycles in which they can be used, and this new review completes that article with the contributions made in the same area for the period 2010 to 2020. The synthesized heterocycles to be covered include pyrimidines, pyridines, pyrroles, indoles, chromenes, xanthenes, pyrans, azlactones, azoles, diazines, azepines, flavones, and formylchromones, among others.

Biodiesel Production from Low-Quality Oils Using Heterogeneous Cesium Salts of Vanadium-Substituted Polyoxometalate Acid Catalyst

This research aims at developing an efficient and reusable catalyst to improve biodiesel production processes. To achieve this, a vanadium-substituted polyoxometalate (POM) acid, namely H6PV3MoW8O40, was firstly prepared, and then the heterogenzation of the homogeneous Keggin-type heteropoly acids was performed by the partial proton substitution by monovalent large cesium cations with the formation of solid Cs2H4PV3MoW8O40 catalysts. Several techniques, such as X-ray diffractometer, Fourier transform infrared, coupled plasma–atomic emission spectrometry, Diffuse reflectance ultraviolet–visible spectrum, thermal gravimetric analysis and N2 adsorption–desorption techniques, were employed to characterize the as-prepared solid catalyst. The solid acid catalyst had the capacity to catalyze both the transesterification of soybean oil and esterification of free fatty acids (FFAs) simultaneously, providing an efficient production process for the production of biodiesel from low-quality oils. Under the operational conditions of a methanol/oil molar ratio of 30:1, a catalyst dosage of 5 wt.%, a reaction temperature of 140 °C, and a reaction duration of 8 h, an oil conversion of 92.2% was attained with the total FFA transformation to biodiesel. Furthermore, the catalyst could be reutilized for several cycles with no significant drop in its activity, thus having great potential for application with a bright perspective in the production of biodiesel, especially from low-quality oil feedstocks.

L, Durrani A. Environmentally benign PEG-OSO3H catalysed Ultrasound promoted cascade synthesis of furocoumarins in water

Background:

Green synthesis of furocoumarins in water, PEG-OSO3H used as a recyclable catalyst for the one-pot syntheis in water. avoid used of toxic, lachrymatric and unstablephenacyl bromides instead of that we prepared it in-situ and directly condence with 4-hydroxycoumarins.

Objective:

PEG-OSO3H found to be an efficient and reusable catalyst for the microwave irradiated one-pot synthesis of 3- Aryl-furo[3,2-c]coumarins in PEG-water as a greener reaction medium. This method found to be rapid, simple, ecofriendly and yield obtained relatively higher than other reported methods.

Methods:

Aromatic ketones (5 mmol), NBS (5mmol) was added in solution of PEG-OSO3H (10 mol%) in 10 ml water and irradiated under ultrasound at 80-85°C. then solution of 4-hydroxycoumarin (5 mmol) and solution of acetic acid and ammonium acetate (1 ml) were added into it. Reaction mass was further irradiated for 3 min. The reaction mixture was extracted with ethyl acetate (3 x 10ml) and the combined ethyl acetate phase was concentrated under reduced pressure to obtain corresponding 3-Aryl-furo[3,2-c]coumarins. Aqueous layer was reused for the next reactions.

Results:

It was observed that electrons withdrawing groups (-NO2,-F etc.) on benzene ring of aromatic ketones increases the rate of reactions as well as yield of the products. The IR spectrum of compound 4a showed prominent peaks at 1737cm-1C=O stretching for lactone, 1H NMR of compound 4c showed characteristic singlets for –CH3 of methoxy group of at 3.94 ppm, The above spectral data confirmed the structure of compound. The 13C NMR spectrum of 4b also shows the peaks of CH3, at 23.25 ppm.

Conclusion:

PEG-OSO3H found to be an efficient and reusable catalyst for the microwave irradiated one-pot synthesis of 3-Aryl-furo[3,2-c]coumarins in PEG-water as a greener reaction medium. This method found to be rapid, simple, ecofriendly and yield obtained relatively higher than other reported methods.

H3PW12O40/SBA-15 for the Solventless Synthesis of 3-Substituted Indoles

A family of silica-supported H3PW12O40 (HPW) solid acid catalysts was prepared by wet impregnation of mesoporous SBA-15 and investigated for the solventless synthesis of 3-substituted indoles under mild conditions. Mesoporous SBA-15 facilitated a high dispersion of immobilised H3PW12O40, significantly improving the catalytic efficiency of the heteropolyacid for the desired multi-component transformation. The yield of 3-substituted indoles strongly correlated with HPW loading (which spanned 3.2–51.6 wt %) and corresponding acid strength; the 51.6 wt % HPW/SBA-15 delivered 81% yield of 2-[(1H-indol-3-yl)(phenyl)methyl]malononitrile, approximately five times greater than that of the unsupported HPW, and exhibited a broad substrate scope for aromatic aldehydes.