Hexamethylenetetramine Copper Diiodide Immobilized on Graphene Oxide Nanocomposite as Recyclable Catalyst for Sonochemical Green Synthesis of Diarylethynes

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.

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.

Sonochemistry in Transition Metal Catalyzed Cross-coupling Reactions: Recent Developments

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Transition metal catalyzed cross-coupling reactions have always been very important in synthetic organic chemistry due to their versatility in forming all sorts of carbon-carbon and carbon-hetero atom bonds. Incorporation of ultrasound assistance to these protocols resulted in milder reaction conditions, faster reaction rates, etc. This review focuses on the contributions made by ultrasound-assisted protocols towards transition metal catalyzed crosscoupling reactions.