Preparation and characterization of Lewis acid grafted sulfonated carbon@titania composites for the multicomponent synthesis of 4H-pyrimido[2,1-b]benzothiazoles and benzoxanthenones under solvent-free conditions

Fe/Co-MOF Nanocatalysts: Greener Chemistry Approach for the Removal of Toxic Metals and Catalytic Applications

This study describes the preparation of new bimetallic (Fe/Co)-organic framework (Bi-MOF) nanocatalysts with different percentages of iron/cobalt for their use and reuse in adsorption, antibacterial, antioxidant, and catalytic applications following the principles of green chemistry. The prepared catalysts were characterized using several techniques, including X-ray powder diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, and scanning electron microscopy. These techniques proved the formation of MOFs, and the average crystallite sizes were 25.3-53.1, 27.6-67.2, 3.0-18.9, 3.0-12.9, and 3.0-23.6 nm for the Fe-MOF, Co-MOF, 10%Fe:90%Co-MOF, 50%Fe:50%Co-MOF, and 90%Fe:10%Co-MOF samples, respectively. The nanoscale (Fe/Co) Bi-MOF catalysts as efficient heterogeneous solid catalysts showed high catalytic activity with excellent yields and short reaction times in the catalytic reactions of quinoxaline and dibenzoxanthene compounds, in addition to their antioxidant and antibacterial activities. Furthermore, the nanoscale (Fe/Co) Bi-MOF catalysts efficiently removed toxic metal pollutants (Pb²⁺, Hg²⁺, Cd²⁺, and Cu²⁺) from aqueous solutions with high adsorption capacity.

α-Aminoazoles/azines: key reaction partners for multicomponent reactions

Aromatic α-aminoazaheterocycles are the focus of significant investigations and exploration by researchers owing to their key role in diverse biological and physiological processes. The existence of their derivatives in numerous drugs and alkaloids is due to their heterocyclic nitrogenous nature. Therefore, the synthesis of a structurally diverse range of their derivatives through simple and convenient methods represents a vital field of synthetic organic chemistry. Multicomponent reactions (MCRs) provide a platform to introduce desirable structure diversity and complexity into a molecule in a single operation with a significant reduction in the use of harmful organic waste, and hence have attracted particular attention as an excellent tool to access these derivatives. This review covers the advances made from 2010 to the beginning of 2020 in terms of the utilization of α-aminoazaheterocycles as synthetic precursors in MCRs.

An Overview of Coumarin as a Versatile and Readily Accessible Scaffold with Broad-Ranging Biological Activities

Privileged structures have been widely used as an effective template for the research and discovery of high value chemicals. Coumarin is a simple scaffold widespread in Nature and it can be found in a considerable number of plants as well as in some fungi and bacteria. In the last years, these natural compounds have been gaining an increasing attention from the scientific community for their wide range of biological activities, mainly due to their ability to interact with diverse enzymes and receptors in living organisms. In addition, coumarin nucleus has proved to be easily synthetized and decorated, giving the possibility of designing new coumarin-based compounds and investigating their potential in the treatment of various diseases. The versatility of coumarin scaffold finds applications not only in medicinal chemistry but also in the agrochemical field as well as in the cosmetic and fragrances industry. This review is intended to be a critical overview on coumarins, comprehensive of natural sources, metabolites, biological evaluations and synthetic approaches.

Colorimetric Metal Sensing of Fe3+ and Cr3+ and Photophysical and Electrochemical Studies Based on Benzo[4,5]thiazolo[3,2-a]pyrimidine-3-carboxylate and Its Derivatives

Benzo[4,5]thiazolo[3, 2-a]pyrimidine-3-carboxylate derivatives (4a-i) containing electron-donor and electron-acceptor groups with remarkable photophysical and electrochemical properties were synthesized. The changes in absorption properties of compound 4a in the presence of various cations were evaluated. Compound 4a can act as a colorimetric sensor for highly sensitive and selective detection of Fe³⁺ and Cr³⁺in acetonitrile solvent. Using measurements of absorbance intensity, the binding constants for the 4a + Fe³⁺ complex and 4a + Cr³⁺ complex were found to be 1.958 × 10⁸ and 1.5442 × 10⁷ M^-1 with lower detection limits of 52 and 110 nM, respectively. ¹H NMR titrations, Fourier transform infrared (FTIR) studies, electrospray ionization (ESI)-mass spectra, and Job's plots were used to verify the mechanism of the specific reaction and colorimetric sensing of 4a + Fe³⁺ and 4a + Cr³⁺. The application of compound 4a for the determination of Fe³⁺ in spiked samples of iron tablets in different environmental water samples showed a satisfactory result with good recovery.

Ionic liquid coated sulfonated carbon@titania composites for the one-pot synthesis of indeno[1,2-b]indole-9,10-diones and 1H-pyrazolo[1,2-b]phthalazine-5,10-diones in aqueous media

A novel and efficient ionic liquid based solid Bronsted acid catalyst has been designed and explored as a recyclable catalytic system for multicomponent synthesis in an aqueous reaction media.