Green bio‐based synthesis of Fe 2 O 3 @SiO 2 ‐IL/Ag hollow spheres and their catalytic utility for ultrasonic‐assisted synthesis of propargylamines and benzo[ b ]furans

Synthesis of propargylamine: pioneering a green path with non-conventional KA2 coupling approach

The KA2 coupling reaction is a well-explored and versatile method for forming C-C bonds in synthetic chemistry. It is composed of ketone, amine, and alkyne, which play a major role in the synthesis of propargylamines, known for their diverse biological activities and are used in treating neurogenetical disorders. The KA2 coupling is highly challenging due to the low reactivity of ketimines toward nucleophilic attacks with metal acetylide intermediates formed by activating the C-H bond of the alkyne. Despite predominant studies conducted on thermal conditions for KA2 coupling reactions, green and sustainable approaches like non-conventional methods still have a lot to achieve. This review article provides a comprehensive introduction to the non-conventional approach in the KA2 coupling reaction, outlining its mechanisms and exploring future aspects.

A sustainable avenue for the synthesis of propargylamines and benzofurans using a Cu-functionalized MIL-101(Cr) as a reusable heterogeneous catalyst

A heterogeneous copper-catalyzed A3 coupling reaction of aldehydes, amines, and alkynes for the synthesis of propargylamines and benzofurans has been developed. Here, the modified metal-organic framework MIL-101(Cr)-SB-Cu complex was chosen as the heterogeneous copper catalyst and prepared via post-synthetic modification of amino-functionalized MIL-101(Cr). The structure, morphology, thermal stability, and copper content of the catalyst were determined by FT-IR, PXRD, SEM, TEM, EDX, TGA, XPS, and ICP-OES. The catalyst shows high catalytic activity for the aforementioned reactions under solvent-free reaction conditions. High yields, low catalyst loading, easy catalyst recovery and reusability with not much shrink in catalytic activity, and a good yield of 82% in gram-scale synthesis are some of the benefits of this protocol that drove it towards sustainability.

Ionic liquid-loaded triazine-based magnetic nanoparticles for promoting multicomponent reaction

A novel hybrid magnetic ionic-liquid as a heterogeneous catalyst was synthesized by hybridization of imidazolium based-ionic liquid onto the nitrogen rich magnetic nanocomposite. The resulting catalyst (n-Fe3O4@SiO2-TA-SO3H IL) has two advantages besides recyclability: (i) high capacity of functional-SO3H group with imidazolium-IL cation for promoting symmetric and asymmetric Hantzsch reaction and (ii) easy recovery. Caused by the polymeric and magnetic nature of the n-Fe3O4@SiO2-TA-SO3H IL, large quantities of acidic groups were bound to the n-Fe3O4@SiO2-TA surface, which reduced the catalyst mass applied to the catalytic reaction. Moreover, superior catalytic performance and outstanding recyclability of n-Fe3O4@SiO2-TA-SO3H IL in mild condition make this method a green pathway for manufacture of satisfactory chemicals.

Investigation of halloysite nanotubes and Schiff base combination with deposited copper iodide nanoparticles as a novel heterogeneous catalytic system

The design, preparation and characterization of a novel composite based on functionalization of halloysite nanoclay with Schiff base followed by immobilization of copper iodide as nanoparticles is revealed. This novel nano composite was fully characterized by utilization of FTIR, SEM/EDX, TGA, XRD and BET techniques. This Cu(I) NPs immobilized onto halloysite was successfully examined as a heterogeneous, thus easily recoverable and reusable catalyst in one of classist organic name reaction so-called “Click Reaction”. That comprised a three component reaction of phenylacetylene, α-haloketone or alkyl halide and sodium azide in aqueous media to furnish 1,2,3‐triazoles in short reaction time and high yields. Remarkably, the examination of the reusability of the catalyst confirmed that the catalyst could be reused at least six reaction runs without appreciable loss of its catalytic activity.

Greener organic synthetic methods: Sonochemistry and heterogeneous catalysis promoted multicomponent reactions

Ultrasound is an essential technique to improve organic synthesis from the point of view of green chemistry, as it can promote better yields and selectivities, in addition to shorter reaction times when compared to the conventional methods. Heterogeneous catalysis is another pillar of sustainable chemistry being the recycling and reuse of the catalysts one of its great advantage. In the other hand, multicomponent reactions provide the synthesis of structurally diverse compounds, in a one-pot fashion, without isolation and purification of intermediates. Thus, the combination of these protocols has proved to be a powerful tool to obtain biologically active organic compounds with lower costs, time and energy consumption. Herein, we provide a comprehensive overview of advances on methods of organic synthesis that have been reported over the past ten years with focus on ultrasound-assisted multicomponent reactions under heterogeneous catalysis. In particular, we present pharmacologically important N- and O-heterocyclic compounds, considering their synthetic methods using green solvents, and catalyst recycling.

Two inorganic–organic hybrid silver-polyoxometalates as reusable catalysts for one-pot synthesis of propargylamines via a three-component coupling reaction at room temperature

Two silver-polyoxometalates [Ag₃L₂(DMSO)₂][PW₁₂O₄₀]·4DMSO (1) and [(Ag₂L₂)₂][SiW₁₂O₄₀]·10DMSO·2H₂O (2) are made and 1 shows good catalytic activities for three-component coupling reaction.

Functionalized Silicas for Metal-Free and Metal-Based Catalytic Applications: A Review in Perspective of Green Chemistry

Heterogeneous catalysis plays a key role in promoting green chemistry through many routes. The functionalizable reactive silanols highlight silica as a beguiling support for the preparation of heterogeneous catalysts. Metal active sites anchored on functionalized silica (FS) usually demonstrate the better dispersion and stability due to their firm chemical interaction with FSs. Having certain functional groups in structure, FSs can act as the useful catalysts for few organic reactions even without the need of metal active sites which are termed as the covetous reusable organocatalysts. Magnetic FSs have laid the platform where the effortless recovery of catalysts is realized just using an external magnet, resulting in the simplified reaction procedure. Using FSs of multiple functional groups, we can envisage the shortened reaction pathway and, reduced chemical uses and chemical wastes. Unstable bio-molecules like enzymes have been stabilized when they get chemically anchored on FSs. The resultant solid bio-catalysts exhibited very good reusability in many catalytic reactions. Getting provoked from the green chemistry aspects and benefits of FS-based catalysts, we confer the recent literature and progress focusing on the significance of FSs in heterogeneous catalysis. This review covers the preparative methods, types and catalytic applications of FSs. A special emphasis is given to the metal-free FS catalysts, multiple FS-based catalysts and magnetic FSs. Through this review, we presume that the contribution of FSs to green chemistry can be well understood. The future perspective of FSs and the improvements still required for implementing FS-based catalysts in practical applications have been narrated at the end of this review.

One-pot synthesis of propargylamines using magnetic mesoporous polymelamine formaldehyde/zinc oxide nanocomposite as highly efficient, eco-friendly and durable nanocatalyst: optimization by DOE approach

Magnetic mesoporous polymelamine formaldehyde nanocomposite-incorporating ZnO nanoparticles were successfully synthesized using solvothermal and sol-gel methods. Fourier-transform infrared spectrometry (FT-IR), X-ray diffraction, Brunauer-Emmett-Teller, vibrating sample magnetometer, thermogravimetric analysis, elemental analysis, transmission electron microscopy and field emission scanning electron microscopy techniques were then utilized for evaluation of nanocomposites. The as-prepared nanocomposite can be used as heterogeneous nanocatalyst with remarkable performance for A³ coupling reaction toward one-pot synthesis of propargylamine and its derivatives under solvent-less condition. In order to maximize the product yield, the variables, i.e., reaction time, temperature and catalyst amount, were optimized by using a statistical approach. The synthesized nanocomposite can be easily separated from the reaction medium and reused over and over, without significant changes in its catalytic activity.

Zn-Catalyzed Multicomponent KA2 Coupling: One-Pot Assembly of Propargylamines Bearing Tetrasubstituted Carbon Centers

Tetrasubstituted propargylamines comprise a unique class of highly useful compounds, which can be accessed through the multicomponent coupling between ketones, amines, and alkynes (KA² coupling), an underexplored transformation. Herein, the development of a novel, highly efficient, and user-friendly catalytic system for the KA² coupling, based on the environmentally benign, inexpensive, and readily available zinc acetate, is described. This system is employed in the multicomponent assembly of unprecedented, tetrasubstituted propargylamines derived from structurally diverse, challenging, and even biorelevant substrates. Notable features of this protocol include the demonstration of the enhancing effect that neat conditions can have on catalytic activity, as well as the expedient functionalization of hindered, prochiral cyclohexanones, linear ketones, and interesting molecular scaffolds such as norcamphor and nornicotine.