Ytterbium (III) triflate/Sodium Dodecyl Sulfate: A Versatile Recyclable and Water‐Tolerant Catalyst for the Synthesis of Bis(indolyl)methanes (BIMs)

KIO3-catalyzed selective oxidation of thiols to disulfides in water under ambient conditions

Herein, we report a KIO3-catalyzed oxidative coupling of thiols to their corresponding disulfides in water, in a short time and at ambient temperature. The reaction has a broad scope and exhibits good functional group tolerance, resulting in the desired products in excellent yields. This approach allows the reuse of the reaction system in multiple cycles and scale-up. Furthermore, the current protocol demonstrates compatibility for in situ generation of disulfides and post application in C(sp2)-H bond sulfenylation.

Unlocking Diversity: From Simple to Cutting-Edge Synthetic Methodologies of Bis(indolyl)methanes

From a synthetic perspective, bis(indolyl)methanes have undergone extensive investigation over the past two to three decades owing to their remarkable pharmacological activities, encompassing anticancer, antimicrobial, antioxidant, and antiinflammatory properties. These highly desirable attributes have spurred significant interest within the scientific community, leading to the development of various synthetic strategies that are not only more efficient but also ecofriendly. This synthesis-based literature review delves into the advancements made in the past 5 years, focusing on the synthesis of symmetrical as well as unsymmetrical bis(indolyl)methanes. The review encompasses a wide array of methods, ranging from well-established techniques to more unconventional and innovative approaches. Furthermore, it highlights the exploration of various substrates, encompassing readily available chemicals such as indole, aldehydes/ketones, indolyl methanols, etc. as well as the use of some specific compounds as starting materials to achieve the synthesis of this invaluable molecule. By encapsulating the latest developments in this field, this review provides insights into the expanding horizons of bis(indolyl)methane synthesis.

Recent Advances on the Antimicrobial Activities of Schiff Bases and their Metal Complexes: An Updated Overview

Schiff bases represent a valuable class of organic compounds, synthesized via condensation of primary amines with ketones or aldehydes. They are renowned for possessing innumerable applications in agricultural chemistry, organic synthesis, chemical and biological sensing, coating, polymer and resin industries, catalysis, coordination chemistry, and drug designing. Schiff bases contain imine or azomethine (-C=N-) functional groups which are important pharmacophores for the design and synthesis of lead bioactive compounds. In medicinal chemistry, Schiff bases have attracted immense attention due to their diverse biological activities. This review aims to encompass the recent developments on the antimicrobial activities of Schiff bases. The article summarizes the antibacterial, antifungal, antiviral, antimalarial, and antileishmanial activities of Schiff bases reported since 2011.

Urea Hydrogen Peroxide and Ethyl Lactate, an Eco-Friendly Combo System in the Direct C(sp2)-H Bond Selenylation of Imidazo[2,1-b]thiazole and Related Structures

Herein, we describe a urea hydrogen peroxide-mediated sustainable protocol for the synthesis of selenylated imidazo[2,1-b]thiazole by using half molar equivalent diorganyl diselenides in ethyl lactate as a greener solvent. The reaction features high yields, easy performance on gram scale, metal-free conditions, as well as applicability to imidazopyridine and imidazopyrimidine.

Recent Advances on Direct Functionalization of Indoles in Aqueous Media

Indoles and their derivatives have dominated a significant proportion of nitrogen-containing heterocyclic compounds and play an essential role in synthetic and medicinal chemistry, pesticides, and advanced materials. Compared with conventional synthetic strategies, direct functionalization of indoles provides straightforward access to construct diverse indole scaffolds. As we enter an era emphasizing green and sustainable chemistry, utilizing environment-friendly solvents represented by water demonstrates great potential in synthesizing valuable indole derivatives. This review aims to depict the critical aspects of aqueous-mediated indoles functionalization over the past decade and discusses the future challenges and prospects in this fast-growing field. For the convenience of readers, this review is classified into three parts according to the bonding modes (C-C, C-N, and C-S bonds), which focus on the diversity of indole derivatives, the prominent role of water in the chemical process, and the types of catalyst systems and mechanisms. We hope this review can promote the sustainable development of the direct functionalization of indoles and their derivatives and the discovery of novel and practical organic methods in aqueous phase.

Layered Copper Hydroxide Salts as Catalyst for the “Click” Reaction and Their Application in Methyl Orange Photocatalytic Discoloration

The 1,2,3-triazoles are an important class of organic compounds that are found in a variety of biologically active compounds. The most usual and efficient methodology to synthetize these compounds is the Copper-catalyzed Azide–Alkyne Cycloaddition (CuAAC), preferably by use of click chemistry principles. Therefore, the development of simple, robust, easily accessible and efficient materials as catalysts for this kind of reaction is highly desirable. In this sense, layered hydroxide salts (LHS) emerge as an interesting alternative for the click reaction. Thus, we describe herein the preparation and characterization of copper (II) layered hydroxide salts and their application as catalysts for the CuAAC reaction under solvent-free conditions. This synthetic methodology of CuAAC reaction is attractive as it follows several concepts of green chemistry, such as being easy to perform, allowing purification without chromatographic column, the process forming no sub-products, affording the desired 1,2,3-traizoles in the specific 1,4-disubstituted position in high yield, and having a short reaction time. Moreover, the photocatalysis for the degradation of methyl orange was also highly efficient using the same catalyst.

KIO4 -mediated Selective Hydroxymethylation/Methylenation of Imidazo-Heteroarenes: A Greener Approach

Herein, we report a KIO₄ -mediated, sustainable and chemoselective approach for the one-pot C(sp² )-H bond hydroxymethylation or methylenation of imidazo-heteroarenes with formaldehyde, generated in situ via the oxidative cleavage of ethylene glycol or glycerol (renewable reagents) through the Malaprade reaction. In the presence of ethylene glycol, a series of 3-hydroxymethyl-imidazo-heteroarenes was obtained in good to excellent yields. These compounds are important intermediates to access pharmaceutical drugs, e.g., Zolpidem. Furthermore, by using glycerol, bis(imidazo[1,2-a]pyridin-3-yl)methane derivatives were selectively obtained in good to excellent yields.

FeCl3·6H2O as a Mild Catalyst for Nucleophilic Substitution of Symmetrical Bis(indoyl)methanes

In this paper, unsymmetrical bis(indolyl)methane (BIM) and 3-alkylindole derivatives are smoothly synthesized from symmetrical BIMs with a variety of nucleophiles including heteroaromatic/aromatic compounds, allylsilane and alkynylsilane. FeCl₃·6H₂O is found to be a mild and highly effective catalyst for this nucleophilic substitution reaction in which N-methyl-2-phenylindole behaves as a good leaving group in the C_sp³-C_sp² bond cleavage reaction. The operational ease, nonexpensive and environmentally friendly catalyst, mild reaction conditions, broad functional group tolerance, and scalability of this reaction strategy are advantages of the present procedure.

Chickpea leaf exudates: a green Brønsted acid type biosurfactant for bis(indole)methane and bis(pyrazolyl)methane synthesis

A clean and highly efficient protocol for green synthesis of bis(indole)methanes and bis(pyrazolyl)methanes has been successfully achieved by using a naturally sourced bio-surfactant, chickpea leaf exudates (CLE), as a Brønsted acid-type catalyst.

Synthesis of 2,1,3-Benzoxadiazole Derivatives as New Fluorophores-Combined Experimental, Optical, Electro, and Theoretical Study

Herein, we report the synthesis and characterization of fluorophores containing a 2,1,3-benzoxadiazole unit associated with a π-conjugated system (D-π-A-π-D). These new fluorophores in solution exhibited an absorption maximum at around ~419 nm (visible region), as expected for electronic transitions of the π-π* type (ε ~2.7 × 107 L mol-1 cm-1), and strong solvent-dependent fluorescence emission (ΦFL ~0.5) located in the bluish-green region. The Stokes' shift of these compounds is ca. 3,779 cm-1, which was attributed to an intramolecular charge transfer (ICT) state. In CHCl3 solution, the compounds exhibited longer and shorter lifetimes, which was attributed to the emission of monomeric and aggregated molecules, respectively. Density functional theory was used to model the electronic structure of the compounds 9a-d in their excited and ground electronic states. The simulated emission spectra are consistent with the experimental results, with different solvents leading to a shift in the emission peak and the attribution of a π-π* state with the characteristics of a charge transfer excitation. The thermal properties were analyzed by thermogravimetric analysis, and a high maximum degradation rate occurred at around 300°C. Electrochemical studies were also performed in order to determine the band gaps of the molecules. The electrochemical band gaps (2.48-2.70 eV) showed strong correlations with the optical band gaps (2.64-2.67 eV).