Phosphoric acid functionalized graphene oxide: A highly dispersible carbon-based nanocatalyst for the green synthesis of bio-active pyrazoles (original) (raw)
Related papers
2020
In this study, graphene oxide was functionalized with 3-aminopyridine to prepare a novel nanocatalyst known as the graphene oxide functionalized pyridine-methanesulfonate (GO@PyH-CH3SO3). The GO@PyH-CH3SO3 was then employed as an effective nanocatalyst to prepare 4, 4'-(aryl methylene)-bis(1H-pyrazol-5-ols) via one-pot multicomponent condensation reaction of aldehydes with 3-methyl-1-phenyl-1H-pyrazol-5(4H)-one. The best reaction condition involved the use of 0.02 g of the catalyst for 20 min and at 70 °C without using any solvent. Also, the reusability of catalyst and product yield in five runs was examined and no significant change was observed. The leaching test was utilized to assess the nature of the catalytic activity, and the results showed the heterogeneous condition for the catalytic activity. Efficiently and capability of the GO@PyH-CH3SO3 catalyst and other catalysts were compared and showed the superior properties of this catalyst.
Regenerable Acidity of Graphene Oxide in Promoting Multicomponent Organic Synthesis
Scientific Reports, 2019
the Brønsted acidity of graphene oxide (Go) materials has shown promising activity in organic synthesis. However, roles and functionality of Lewis acid sites remain elusive. Herein, we reported a carbocatalytic approach utilizing both Brønsted and Lewis acid sites in GOs as heterogeneous promoters in a series of multicomponent synthesis of triazoloquinazolinone compounds. the Gos possessing the highest degree of oxidation, also having the highest amounts of Lewis acid sites, enable optimal yields (up to 95%) under mild and non-toxic reaction conditions (85 °C in EtOH). The results of FT-IR spectroscopy, temperature-programed decomposition mass spectrometry, and X-ray photoelectron spectroscopy identified that the apparent Lewis acidity via basal plane epoxide ring opening, on top of the saturated Brønsted acidic carboxylic groups, is responsible for the enhanced carbocatalytic activities involving Knoevenagel condensation pathway. Recycled GO can be effectively regenerated to reach 97% activity of fresh GO, supporting the recognition of GO as pseudocatalyst in organic synthesis. Carbonaceous materials have emerged as promising green carbocatalysts in various organic reactions 1-8. Graphene oxide (GO), a 2D, carbonaceous material bearing different oxygen functional groups such as alcohol, epoxide, ketones, and carboxylic acid 9-12 , is emerging as a green alternative for organic transformations and particularly superb in acidic carbocatalysis 5,13,14. The inherent Brønsted acidity of GO, due to the presence of acidic oxygen groups on the edge of GO sheets, has been well exploited in the synthesis of benzylpyrazolyl coumarins 15 , thioacetals 16 , ethers 17 , and other Brønsted acid-catalyzed reactions such as transamidation 18 , Fisher esterification 19-22 , Boc-protection of alcohols 23 , and Kabachnik-Fields reactions 24. Despite these extensive studies, only the Brønsted acidic nature of GO was recognized. Recently, Szostak 25 and Bandini groups 26 , demonstrated the success of GO-promoted alkylation of arenes and thiophenes. Among these Friedel-Crafts reactions, the possible activities of Lewis acidity of GO has been suggested. However, studies on the use and understanding of GO capitalizing on its Lewis acidity is very few. Multicomponent reactions (MCR) involve the combination of three or more compounds in one-pot, which affords rapid formation of small molecules with complex structures. Easy purification, high atom economy, and less waste generation due to a minimal number of synthetic steps make MCR an environmental friendly tool for organic synthesis 27. Triazoloquinazolinones are attractive target compounds due to their important biological activities as anti-HIV 28 , anticonvulsant 29 , analgesic 30 , and antihypertensive 31 agents. In the past decade, efforts have been made to synthesize triazoloquinazolinone using different acid catalysts in MCR approach 32-35 , where Lewis acids were proved to be important in facilitating reaction yields. For example, the Lewis acidities of nickel nanoparticles, molecular iodine, and hydrotalcites have been shown to promote the multicomponent synthesis of triazoloquinazolinones effectively 36-38. However, the drawbacks of non-reusable promoters, toxic solvents, corrosive homogenous acid promoters, and complicated catalysts were involved. Aqueous sustainable, heterogeneous GO materials with the strong acidity and high oxidative degrees are thus a promising candidate to realize high reaction yields, low toxicity solvent, and recyclability. The reported studies using GO as carbocatalyst in different MCR 39-42 have shown the loss of active oxygen groups during the reaction, which significantly hinders the reusability. Unclear roles of the involved acidic groups of GO complicate the materials design pathway in improving both the activity and stability in acidity-assisted organic synthesis. In this paper, we investigated the acid role of GO with an activity correlation of a series of
Emerging Trends in the Syntheses of Heterocycles Using Graphene-based Carbocatalysts: An Update
Topics in Current Chemistry, 2019
Graphene-based carbocatalysts owing to numerous amazing properties such as large specific surface area, high intrinsic mobility, excellent thermal and electrical conductivities, chemical stability, ease of functionalization, simple method of preparation, effortless recovery and recyclability have gained a superior position amongst the conventional homogeneous and heterogeneous catalysts. In this review, an endeavor has been made to highlight the syntheses of diverse heterocyclic compounds catalyzed by graphene-based catalysts. Further, the study also reveals that all the catalysts could be reused several times without significant loss in their catalytic activity. Additionally, most of the reactions catalyzed by graphene-based carbocatalysts were carried out at ambient temperature and under solvent-free conditions. Thus, the graphene-based catalysts do not merely act as efficient catalysts but also serve as sustainable, green catalysts. This review is divided into various subsections , each of which comprehensively describes the preparation of a particular heterocyclic scaffold catalyzed by graphene-derived carbocatalyst in addition to synthesis of graphene oxide and reduced graphene oxide, functionalization, and structural features governing their catalytic properties.
Nanochemistry Research, 2017
The new magnetic amine-functionalized graphene oxide (Fe3O4-GO-NH2) nanocatalyst was prepared through the reaction of 3-aminopropyltriethoxysilane (APTES) with magnetic graphene oxide (Fe3O4-GO). It was characterized by XRD, TEM, SEM, FT-IR and EDX techniques. The intrinsic carboxylic acids on the edges of Fe3O4-GO along with the amine groups post grafted to the surface of Fe3O4-GO led to preparation of an acid-base bifunctional magnetically recyclable nanocatalyst. It proved to be efficient nanocatalyst for solvent-free synthesis of pyrano[3,2-c]pyridine derivatives under mild reaction conditions with good to excellent yields. This heterogeneous catalyst also exhibited higher activities than acid or base functionalized mesoporous silica, magnetic GO or basic Al2O3 an even higher than some basic homogeneous catalysts such as triethylamine and piperazine. More importantly, due to the loaded iron oxide nanoparticles, this catalyst could be easily recovered from the reaction mixture using an external magnet and reused without significant decrease in activity even after 7 runs.
Synthesis of functionalized dihydro-2-oxopyrroles using graphene oxide as heterogeneous catalyst
Molecular Diversity, 2018
A mild, efficient synthetic approach for the synthesis of highly functionalized dihydro-2-oxopyrroles is developed by using graphene oxide, a readily available and inexpensive material, as an eco-benign solid acid catalyst in ethanol at room temperature. The present methodology displays several advantages such as practical simplicity, high atom economy, easy workup procedure, and high yields of the products.
Proceedings of The 21st International Electronic Conference on Synthetic Organic Chemistry, 2017
In this paper, we have synthesized a series of 2,4,5-trisubstituted imidazoles from a new, highly efficient and green method. The reaction is performed in ethanol, by using 1,3,5-Tris (2hydroxyethyl) isocyanurate-Cu(II) functionalized magnetic graphene oxide (MGO-THEIC-CuII), which has done under microwave irradiation. All compounds have been well characterized by IR and NMR spectral data. introduction Catalysts are one of the main contributors to green synthesis. Homogeneous and heterogeneous catalysis made enormous contributions to the improvement of society. Both types possess several advantages, however, heterogeneous catalysis appears to be more suitable for the large scale industrial processes, which prefer continuous flow systems. Easy handling, robustness, lower sensitivity to common conditions (e.g. moisture, air etc.), longer shelf life, are the most important advantages of using heterogeneous catalysts. 1 The use of carbocatalysts is attractive owing to their low cost and high natural abundance. Carbocatalyts have been demonstrated in the oxidative aromatization and preparation of heteroaromatic compounds such as pyridine, imidazole, and pyrimidine. Recently, graphene oxide (GO) has attracted attention as a new carbocatalyst in organic synthesis. Graphene oxide (GO)) is a 2D carbon material with abundant oxygen-containing groups at the edge (e.g. carboxyl) and surface defects (e.g. hydroxyl and epoxy groups). Comparing with graphene, GO is much easier to be synthesized, functionalized and chemically assembled. GO has been widely applied in multidisciplinary fields, including energy storage, advance catalysis, sensitive detectors and environmental pollutant management. 2 The existence of various types of hydrophilic groups allows GO to be easily exfoliated, when it is in the liquid state. These active groups can be used to induce chemical reactions and provide GO with additional functional groups after the modification, thereby increasing the flexibility and diversity of GO applications. For example, GO layers can be intercalated or cross-linked with primary aliphatic amines, amino acids, diaminoalkanes, boronates, acyl chloride, and isocyanates, or they can be covalently linked to polymers through esterification. 3 In recent years, the importance of imidazoles in biological systems has attracted considerable interests because of their chemical and biochemical properties, and pharmaceutical compounds with an imidazole ring system. The heterocyclic compounds including 2,4,5-trisubstituted imidazoles possess