Microwave-assisted copper- and palladium-catalyzed sonogashira-type coupling of aryl bromides and iodides with trimethylsilylacetylene

A novel core@double-shell three-layer structure with dendritic fibrous morphology based on Fe3O4@TEA@Ni-organic framework: a highly efficient magnetic catalyst in the microwave-assisted Sonogashira coupling reaction

In synthetic organic chemistry, the formation of carbon-carbon bonds is a significant and substantial reaction. As a result, developing a highly active magnetic heterogeneous catalyst with excellent performance is a very appealing technique for constructing C-C bonds in organic chemistry. The present study describes the fabrication of a novel and readily recoverable nickel-based metal-organic framework (MOF) for C-C bond formation through the Sonogashira coupling reaction. The efficient magnetic core-shell structure (Fe₃O₄@TEA@MOF) with a 3D dendritic fibrous morphology was successfully synthesized using a hydrothermal approach by immobilizing Ni-based MOF onto the Fe₃O₄@TEA core-shell structure. The fabrication of Fe₃O₄@TEA@MOF was confirmed by various analyses; Fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray analysis (EDS), and elemental mapping confirmed the stepwise fabrication of catalyst. X-ray diffraction analysis (XRD) showed the crystalline nature of the catalyst. Field-emission scanning electron microscopy (FE-SEM) displayed the 3D dendritic fibrous morphology. Thermogravimetric analysis (TGA) and vibrating sample magnetometer analysis (VSM) showed the excellent thermal stability and magnetic properties of Fe₃O₄@TEA@MOF. The Brunauer-Emmett-Teller analysis (BET) found that the fabricated catalyst with a surface area of 36.2 m² g^-1, pore volume of 0.18 cm³ g^-1, and mean pore diameter of 20.38 nm belongs to mesoporous structures. In addition, the information from the inductively coupled plasma-optical emission spectroscopy (ICP-OES) about fresh and reused catalysts showed that the metal leaching amount is slight and about 1.98%. Other advantages of the Fe₃O₄@TEA@MOF catalyst can be mentioned as easily reusable for four runs and high performance (above 98%) in synthesizing diphenylacetylene from phenylacetylene, aryl halide, and cesium carbonate (as the base) under solvent-free and microwave conditions.

Recent Advances in Microwave-Assisted Copper-Catalyzed Cross-Coupling Reactions

Cross-coupling reactions furnishing carbon–carbon (C–C) and carbon–heteroatom (C–X) bond is one of the most challenging tasks in organic syntheses. The early developed reaction protocols by Ullmann, Ullman–Goldberg, Cadiot–Chodkiewicz, Castro–Stephens, and Corey–House, utilizing elemental copper or its salts as catalyst have, for decades, attracted and inspired scientists. However, these reactions were suffering from the range of functional groups tolerated as well as severely restricted by the harsh reaction conditions often required high temperatures (150–200 °C) for extended reaction time. Enormous efforts have been paid to develop and achieve more sustainable reaction conditions by applying the microwave irradiation. The use of controlled microwave heating dramatically reduces the time required and therefore resulting in increase in the yield as well as the efficiency of the reaction. This review is mainly focuses on the recent advances and applications of copper catalyzed cross-coupling generation of carbon–carbon and carbon–heteroatom bond under microwave technology.

New Trends in C-C Cross-Coupling Reactions: The Use of Unconventional Conditions

The ever-growing interest in the cross-coupling reaction and its applications has increased exponentially in the last decade, owing to its efficiency and effectiveness. Transition metal-mediated cross-couplings reactions, such as Suzuki-Miyaura, Sonogashira, Heck, and others, are powerful tools for carbon-carbon bond formations and have become truly fundamental routes in catalysis, among other fields. Various greener strategies have emerged in recent years, given the widespread popularity of these important reactions. The present review comprises literature from 2015 onward covering the implementation of unconventional methodologies in carbon-carbon (C-C) cross-coupling reactions that embodies a variety of strategies, from the use of alternative energy sources to solvent- free and green media protocols.

Microwave-Assisted Palladium-Catalyzed Cross-Coupling Reactions: Generation of Carbon–Carbon Bond

Cross-coupling reactions furnishing carbon–carbon (C–C) bond is one of the most challenging tasks in organic syntheses. The early developed reaction protocols by Negishi, Heck, Kumada, Sonogashira, Stille, Suzuki, and Hiyama, utilizing palladium or its salts as catalysis have, for decades, attracted and inspired researchers affiliated with academia and industry. Tremendous efforts have been paid to develop and achieve more sustainable reaction conditions, such as the reduction in energy consumption by applying the microwave irradiation technique. Chemical reactions under controlled microwave conditions dramatically reduce the reaction time and therefore resulting in increase in the yield of the desired product by minimizing the formation of side products. In this review, we mainly focus on the recent advances and applications of palladium catalyzed cross-coupling carbon–carbon bond formation under microwave technology.

Design, Synthesis and Antibacterial Activity of Coumarin-1,2,3-triazole Hybrids Obtained from Natural Furocoumarin Peucedanin

Synthesis of 1,2,3-triazole-substituted coumarins and also 1,2,3-triazolyl or 1,2,3-triazolylalk-1-inyl-linked coumarin-2,3-furocoumarin hybrids was performed by employing the cross-coupling and copper catalyzed azide-alkyne cycloaddition reaction approaches. The synthesized compounds were evaluated for their in vitro antibacterial activity against Staphylococcus aureus, Bacillius subtilis, Actinomyces viscosus and Escherichia coli bacterial strains. Coumarin-benzoic acid hybrids 4с, 42с and 3-((4-acetylamino-3-(methoxycarbonyl)phenyl)ethynyl)coumarin (29) showed promising activity against S. aureus strains, and the 1,2,3-triazolyloct-1-inyl linked coumarin-2,3-furocoumarin hybrid 37c was endowed with high selectivity against B. subtilis and E. coli species. The in vitro antibacterial activity of 4с, 29, 37c and 42с can potentially be compared with that of a number of modern antibiotic drugs used in the clinic, suggesting promising prospects for further research. A detailed study of the molecular interactions with the targeted protein MurB was performed using docking simulations and the obtained results are quite promising.

Synthetic Access to Functionalized Dipolarophiles of Lewis Basic Complexant Scaffolds through Sonogashira Cross-Coupling

Soft Lewis basic complexants that facilitate selective removal of discrete ions resident in spent nuclear fuel can decrease repository volume and radiotoxicity and are of significant interest. Optimization of chelation efficacy is predicated on modular access to synthons to rapidly evaluate structure-activity relationships. The following work highlights efficient access to functionalized synthons for use as potential dipolarophiles in subsequent cycloaddition processes via Sonogashira coupling of 3-(6-bromo-pyridin-2-yl)-[1,2,4]triazine scaffolds. The 41 examples explored during method development evaluated electrophile and nucleophile diversity affording the desired coupled products in 31-96% isolated yield. Method optimization, substrate scope, a scale-up reaction, and downstream product functionalization are reported herein.

Aromatic heterocycle galectin-1 interactions for selective single-digit nM affinity ligands

A series of 3-triazole-thiogalactosides and 3,3′-triazole-thiodigalactosides substituted with different five-membered heterocycles at the C-4 triazole position were found to have high selectivity for galectin-1. Initial studies on the 3-triazole-thiogalactosides indicated that five membered heterocycles in general gave increased affinity for galectin-1 and improved selectivity over galectin-3. The selectivity profile was similar for thiodigalactosides exemplified by 3,3′ substituted thien-3-yltriazole and thiazol-2-yltriazole, both having single-digit nM galectin-1 affinity and almost 10-fold galectin-1 selectivity. The binding interactions of a thiodigalactoside based galectin-1 inhibitor with two thien-3-yltriazole moieties were studied with X-ray crystallography. One of the thiophene moieties was positioned deeper into the pocket than previously reported phenyltriazoles and formed close contacts with Val31, Ser29, Gly124, and Asp123. The affinity and structural analysis thus revealed that steric and electronic optimization of five-membered aromatic heterocycle binding in a narrow galectin-1 subsite confers high affinity and selectivity.

A series of 3-triazole-thiogalactosides and 3,3′-triazole-thiodigalactosides substituted with different five-membered heterocycles at the C-4 triazole position were found to have high selectivity for galectin-1.