TiO2 -SiO2 Catalyzed Eco-friendly Synthesis and Antioxidant Activity of Benzopyrano[2,3-d ]pyrimidine Derivatives

Transition-Metal Catalyzed Synthesis of Pyrimidines: Recent Advances, Mechanism, Scope and Future Perspectives

Pyrimidine is a pharmacologically important moiety that exhibits diverse biological activities. This review reflects the growing significance of transition metal-catalyzed reactions for the synthesis of pyrimidines (with no discussion being made on the transition metal-catalyzed functionalization of pyrimidines). The effect of different catalysts on the selectivity/yields of pyrimidines and catalyst recyclability (wherever applicable) are described, together with attempts to illustrate the role of the catalyst through mechanisms. Although several methods have been researched for synthesizing this privileged scaffold, there has been a considerable push to expand transition metal-catalyzed, sustainable, efficient and selective synthetic strategies leading to pyrimidines. The aim of the authors with this update (2017-2023) is to drive the designing of new transition metal-mediated protocols for pyrimidine synthesis.

Recent Advances in Multicomponent Reactions Catalysed under Operationally Heterogeneous Conditions

Multicomponent reactions (MCRs) have been gaining significance and attention over the past decade because of their ability to furnish complex products by using readily available and simple starting materials while simultaneously eliminating the need to separate and purify any intermediates. More so, most of these products have been found to exhibit diverse biological activities. Another paradigm shift which has occurred contemporarily is the switch to heterogeneous catalysis, which results in additional benefits such as the reduction of waste and an increase in the safety of the process. More importantly, it allows the user to recover and reuse the catalyst for multiple runs. In summary, both methodologies adhere to the principles of green chemistry, a philosophy which needs to become overarchingly enshrined. The plethora of reactions and catalysts which have been developed gives hope that chemists are slowly changing their ideology. As a result, this review attempts to discuss multicomponent reactions catalysed by operationally heterogeneous catalysts in the past 10 years. In this review, a further distinction is made between the MCRs which lead to the formation of heterocycles and those which do not.

One-Pot Synthesis of Benzopyrano-Pyrimidine Derivatives Catalyzed by P-Toluene Sulphonic Acid and Their Nematicidal and Molecular Docking Study

A cost-effective and environmentally benign benzopyrano-pyrimidine derivative synthesis has been established with the condensation of different salicylaldehyde derivatives, piperidine/morpholine with malononitrile, in the presence of a catalyst containing p-toluene sulphonic acid (PTSA) at 80 °C temperature. This procedure offers a new and enriched approach for synthesizing benzopyrano-pyrimidine derivatives with high yields, a straightforward experimental method, and short reaction times. The synthesized compounds were investigated for their nematocidal activity, and the result shows that among the four compounds, compounds 4 and 5 showed strong nematocidal activity against egg hatching and J2s mortality. The nematocidal efficacy of the compounds might be due to the toxicity of chemicals which are soluble in ethanol. The nematocidal effectiveness was directly related to the concentration of ethanolic dilutions of the compounds, i.e., the maximum treatment concentration, the higher the nematocidal action, or the higher the mortality and egg hatching inhibition. In the present study, with support from docking analysis, the relation between chemical reactivity and nematocidal activity of compound 4 was inferred.

Green biomimetic synthesis of Ag-TiO2 nanocomposite using Origanum majorana leaf extract under sonication and their biological activities

BACKGROUND

Studies of plant extract-mediated synthesis of nanoparticles is extensively explored and studied in recent time due to eco-friendly, cost-effectiveness and minimal use of toxic chemicals for synthesis. In this study, the synthesis of Ag-TiO2 nanocomposites (NCs) was carried out using Origanum majorana leaf extract under ultrasound irradiation. Origanum majorana leaf extract plays an important role as reducing and capping agent in synthesis of Ag-TiO2 nanocomposites (NCs). The antimicrobial activities of synthesised Ag-TiO2 NCs have been studied against Gram-positive and Gram-negative bacteria. In addition to this, the antioxidant activity of green Ag-TiO2 NCs was also evaluated on the basis of free radical scavenging activity against 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid (ABTS), and hydrogen peroxide free radicals.

RESULTS

Green-synthesised Ag-TiO2 NCs were successfully characterised on the basis of UV-Vis spectrophotometer, Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction analysis (XRD), scanning electron microscopy energy-dispersive X-ray spectroscopy (SEM-EDS) and transmission electron microscopy (TEM). The results revealed the spherical shape of nanocomposite with an average size 25-50 nm. The synthesised Ag-TiO2 NCs have showed significant antimicrobial activity against Escherichia coli, Bacillus subtilis and Aspergillus niger in comparison to TiO2 nanoparticles (NPs). The antioxidant evaluation of biomimetic synthesised Ag-TiO2 NCs also exhibited strong activity than TiO2 NPs and comparable to standard.

CONCLUSION

Green-synthesized Ag-TiO2 NCs provide a promising approach that can satisfy the requirement of large-scale industrial production bearing the advantage of low cost, eco-friendly and reproducible.

Synthesis of new 3H-chromeno[2,3-d]pyrimidine-4,6(5H,7H)-diones via the tandem intramolecular Pinner/Dimroth rearrangement

The reaction of 2-amino-4-aryl-7,7-dimethyl-5-oxo-5,6,7,8-tetrahydro-4H-chromene-3-carbonitriles with excess aliphatic carboxylic acids in the presence of phosphoryl chloride (POCl3) afforded new 2-alkyl-5-aryl-8,8-dimethyl-8,9-dihydro-3H-chromeno[2,3-d]pyrimidine-4,6(5H,7H)-diones in high yields. The suggested mechanism involves a tandem intramolecular Pinner/Dimroth rearrangement. The synthesized compounds were characterized by infrared (IR), proton nuclear magnetic resonance (1H NMR), carbon-13 nuclear magnetic resonance (13C NMR) and elemental analysis.