Application of Metal–Organic Frameworks with Sulfonic Acid Tags in the Synthesis of Pyrazolo[3,4-b]pyridines via a Cooperative Vinylogous Anomeric-Based Oxidation

Abstract

Herein, we report the design and synthesis of Co-MOF-71/imidazole/SO3H as a novel porous catalyst with sulfonic acid tags. The structure and morphology of the catalyst were investigated using various techniques such as Fourier transform-infrared spectroscopy (FT-IR), X-ray diffraction, scanning electron microscopy (SEM), SEM elemental mapping, energy-dispersive X-ray spectroscopy, Barret–Joyner–Halenda, and N2 adsorption–desorption isotherms. Co-MOF-71/imidazole/SO3H was studied in the preparation of novel pyrazolo[3,4-b]pyridines under mild and green conditions via a cooperative vinylogous anomeric-based oxidation. A wide range of mono and bis pyrazolo[3,4-b]pyridines were synthesized with good to excellent yields (65–82%). A hot filtration test for the heterogeneous nature of the catalyst indicated the high stability of the prepared catalyst. The recyclability of Co-MOF-71/imidazole/SO3H is another advantage of the present methodology. The structures of the final products were confirmed using FT-IR, 1H-NMR, and 13C-NMR spectroscopic techniques.

Catalytic Application of Functionalized Bimetallic–Organic Frameworks with Phosphorous Acid Tags in the Synthesis of Pyrazolo[4,3-e]pyridines

“…Based on the concept of the modified strategy of MOFs in the design and synthesis of new catalysts in our group research, − we have presented a new porous catalyst based on bimetal–organic frameworks (bimetal–MOFs). In the following, phosphorous acid tags have been used to decorate the bimetallic–organic frameworks, which have created acidic sites for increasing their catalytic activity.…”

“…MOFs, in particular, are synthesized by combining metal clusters and organic compounds as nuclei and ligands, respectively. These materials offer unique properties and structures that make them highly attractive for various applications as catalysts, gas storage, and separation processes. − It is known that two-dimensional (2D) and three-dimensional (3D) porous structures have distinctive features such as tunable pore size, diverse structure, large surface area, and tunable chemistry. − Metal–organic frameworks are widely used in various fields such as gas separation, drug delivery, energy storage, and catalyst. − Also, the catalytic activities of metal–organic frameworks include photocatalysis, , asymmetric catalysis, , supramolecular catalysis, , oxidation of materials, biomass conversion, , electrocatalysis, , acidic and basic catalysis, − separation of toxic substances from different phases, medical, biological, sensors, and solar cells. , Metal–organic frameworks based on a combination of two metals have better stability and properties than single-metal MOFs. − The synergistic effect achieved by incorporating two metals in bimetallic MOFs can significantly enhance their catalytic activity. As a result, the synthesis of bimetallic MOFs has emerged as an attractive approach in this field, offering new avenues for exploration.…”

“…The postmodification method has been considered for designing various catalysts based on metal–organic frameworks (MOFs). In this method, MOFs are assembled and modified with various chemical reagents while their structure and network remain intact. − Our research groups have introduced a new category of acidic catalysts and/or reagents via a postmodification methodology for inserting phosphorous acid tags on the surface of metal–organic frameworks, − mesopores, , melamine, carbon quantum dots, , glycoluril, and uric acid . Phosphorous acid as a catalyst has been used for the oligomerization of light olefins, destructive alkylation of hydrocarbons, and organic synthesis .…”

The Importance of Nonstoichiometric Ratio of Reactants in Organic Synthesis

“…For example, we have used nonstoichiometric ratios of reactants for the preparation of various ionic liquids, molten salts, and gelatoric materials with high purity, 10−17 and also recently for the synthesis of a catalyst. 18 For example, this method is applicable to the synthesis of phosphonium-based ionic liquids (Scheme 5). 12−17 In these reactions, since the products and alkylating agents are highly polar and their separation from each other is very difficult, the best option for easy purification of the product is to use an excess amount of tributylphosphine (nonstoichiometric ratio of reactants), which is easily soluble in nonpolar solvents.…”

Application of Functionalized Zn-Based Metal–Organic Frameworks (Zn-MOFs) with CuO in Heterocycle Synthesis via Azide–Alkyne Cycloaddition

“…In recent years, our research group has been actively involved in studying the catalytic and photocatalytic applications of metal–organic frameworks (MOFs). ,,− Building upon our previous research in this field, the objective of this study is to design and synthesize a cost-effective and recyclable catalyst consisting of CuO nanoparticles supported on Zn-MOFs (Zn-MOF@CuO). This catalyst will be employed for the synthesis of alkynyl derivatives using a multicomponent reaction.…”