Chemistry - Research Publications
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Item Br�nsted acid catalyzed mechanochemical�domino multicomponent reactions by employing liquid assisted grindstone chemistry(Nature Research, 2023-01-25T00:00:00) Borah, Biplob; Swain, Sidhartha; Patat, Mihir; Kumar, Bhupender; Prajapat, Ketan Kumar; Biswas, Rathindranath; Vasantha, R.; Chowhan, L. RajuHere, we have demonstrated a metal-free energy-efficient mechanochemical approach for expedient access to a diverse set of 2-amino-3-cyano-aryl/heteroaryl-4H-chromenes, tetrahydrospiro[chromene-3,4?-indoline], 2,2?-aryl/heteroarylmethylene-bis(3-hydroxy-5,5-dimethylcyclohex-2-enone) as well as tetrahydro-1H-xanthen-1-one by employing the reactivity of 5,5-dimethylcyclohexane-1,3-dione/cyclohexane-1,3-dione with TsOH?H2O as Br�nsted acid catalyst under water-assisted grinding conditions at ambient temperature. The ability to accomplish multiple C�C, C=C, C�O, and C�N bonds from readily available starting materials via a domino multicomponent strategy in the absence of metal-catalyst as well as volatile organic solvents with an immediate reduction in the cost of the transformation without necessitates complex operational procedures, features the significant highlights of this approach. The excellent yield of the products, broad functional group tolerances, easy set-up, column-free, scalable synthesis with ultralow catalyst loading, short reaction time, waste-free, ligand-free, and toxic-free, are other notable advantages of this approach. The greenness and sustainability of the protocol were also established by demonstrating several green metrics parameters. � 2023, The Author(s).Item Coupling Nonstoichiometric Zn0.76Co0.24S with NiCo2S4Composite Nanoflowers for Efficient Synergistic Electrocatalytic Oxygen and Hydrogen Evolution Reactions(American Chemical Society, 2022-12-15T00:00:00) Biswas, Rathindranath; Thakur, Pooja; Ahmed, Imtiaz; Rom, Tanmay; Ali, Mir Sahidul; Patil, Ranjit A.; Kumar, Bhupender; Som, Shubham; Chopra, Deepak; Paul, Avijit Kumar; Ma, Yuan-Ron; Haldar, Krishna KantaTransition-metal sulfide-based composite nanomaterials have garnered extensive interest not only for their unique morphological architectures but also for exploring as a noble-metal-free cost-effective, durable, and highly stable catalyst for electrochemical water splitting. In this work, we synthesized in situ nonstoichiometric Zn0.76Co0.24S with NiCo2S4binary composite flowers (Zn0.76Co0.24S/NiCo2S4) in one step by thermal decomposition of Zn2[PDTC]4and Ni[PDTC]2complexes by a solvothermal process in a nonaqueous medium from their molecular precursor, and their potential application in electrochemical oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) was investigated. Field-emission scanning electron microscopy and transmission electron microscopy analyses revealed the flower-shaped morphology of as-synthesized Zn0.76Co0.24S/NiCo2S4. Again, the structural and chemical compositions were confirmed through powder X-ray diffraction and X-ray photoelectron spectroscopy studies, respectively. The as-obtained 3D flower-type Zn0.76Co0.24S/NiCo2S4nanostructure was further subject to electrochemical OER and HER in alkaline and acidic media, respectively. Zn0.76Co0.24S/NiCo2S4showed low overpotential values of 248 mV (Tafel slope, 85 mV dec-1) and 141 mV (Tafel slope, 79 mV dec-1) for OER and HER activities, respectively, due to the synergistic effects of Zn0.76Co0.24S and NiCo2S4. Several long-term stability tests also affirmed that the Zn0.76Co0.24S/NiCo2S4composite nanostructure is a highly stable and efficient electrocatalyst toward OER and HER activities as compared to the recently reported superior bifunctional electrocatalysts as well as state-of-the-art materials. � 2023 American Chemical Society. All rights reserved.Item Direct Michael addition/decarboxylation reaction catalyzed by a composite of copper ferrite nanoparticles immobilized on microcrystalline cellulose: an eco-friendly approach for constructing 3,4-dihydrocoumarin frameworks(Royal Society of Chemistry, 2022-10-27T00:00:00) Kumar, Bhupender; Borah, Biplob; Babu, J. Nagendra; Chowhan, L. RajuA composite of copper ferrite oxide nanoparticles immobilized on microcrystalline cellulose (CuFe2O4@MCC) was synthesized. The synthesized composite was characterized by FESEM with EDS-Mapping, TEM, P-XRD, TEM, and BET analysis and investigated for its catalytic activity toward Tandem Michael addition and decarboxylation of coumarin-3-carboxylic acid with cyclic 1,3-diketones to obtain novel 3,4-dihydrocoumarin derivatives. This protocol was established with wide substrate scope and significant yield. The significant characteristics of this methodology are mild reaction conditions, easy setup procedure, non-toxic, and cost-effectiveness. A gram-scale synthesis with low catalyst loading was also demonstrated. � 2022 The Royal Society of Chemistry.Item Sustainable synthesis of highly diastereoselective & fluorescent active spirooxindoles catalyzed by copper oxide nanoparticle immobilized on microcrystalline cellulose(John Wiley and Sons Ltd, 2022-05-18T00:00:00) Kumar, Bhupender; Babu, Nagendra J.; Chowhan, Raju L.Composites of copper oxide nanoparticles immobilized on microcrystalline cellulose (Cu2O@MCC) were synthesized and studied for their catalytic activity toward 1,3-dipolar cycloaddition reaction. Azomethine ylide was in situ generated from isatin and 1,2,3,4-tetrahydroisoquinoline (THIQ) and styrylisoxazoles/chalcones used as dipolarphiles in one-pot synthesis of novel spiro polycyclic heterocyclic compounds. Cu2O@MCC showed excellent catalytic activity on 20 mg of composite with 30% loading of copper on MCC. The scale-up and recyclability experiment on the 10�mmol scale revealed the sustainability of composite even after four consecutive cycles. The products were fluorescent active, obtained in good to excellent yield with high regio and diastereoselectivity. The relevant features of the developed protocol are eco-friendly with a wide range of substrate scope and shorter reaction time. � 2022 John Wiley & Sons Ltd.Item Synthesis of in situ immobilized iron oxide nanoparticles (Fe3O4) on microcrystalline cellulose: Ecofriendly and recyclable catalyst for Michael addition(John Wiley and Sons Ltd, 2021-09-21T00:00:00) Kumar, Bhupender; Reddy, Marri Sameer; Dwivedi, Kartikey Dhar; Dahiya, Amarjeet; Babu, J. Nagendra; Chowhan, L. RajuMicrocrystalline cellulose-immobilized Fe3O4 magnetic nanoparticles (Fe3O4@MCC) with iron loading 5%�20% are synthesized and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The synthesized nanocomposites were studied for their catalytic activity towards Michael addition reaction by employing 1,3-cyclohexadione/dimedone and styrylisoxazole in an aqueous ethanolic medium. The catalyst with 15% iron loading showed the highest efficiency with an excellent yield. Michael addition reaction is one of the most important reaction for the creation of a carbon�carbon bond and widely used in organic synthesis under mild condition. The prepared catalyst performed well in Michael addition reaction and afforded the product in excellent yield. The products were isolated by simple filtration without use of any chromatographic techniques. The scale-up experiment on 10-mmol scale proved the sustainability of the methodology. The catalyst was recycled, and the recovered catalyst data showed no considerable depreciation in catalytic activity even after 5 consecutive cycles. The advantages of this green and safe procedure include a simple reaction set-up, very mild reaction conditions, high yields, moderate reaction time, recyclable catalyst, and easy separation of the products without use of any tedious separation techniques. � 2021 John Wiley & Sons, Ltd.Item Acetyl oxime/azirine 1, 3-dipole and strategy for the regioselective synthesis of polysubstituted pyrroles via [3 + 2] cycloaddition with alkyne utilizing Fe2O3@cellulose catalyst(Elsevier B.V., 2021-09-27T00:00:00) Dwivedi, Kartikey Dhar; Kumar, Bhupender; Reddy, Marri Sameer; Borah, Biplob; Nagendra Babu, J.; Chowhan, L. RajuFe2O3@cellulose catalyzed regioselective [3 + 2] cycloaddition of acetyl oxime with alkynes via 2H?azirines intermediate generated in situ in an aqueous ethanolic medium is described. The methodology is highly regioselective for the synthesis of polysubstituted pyrroles in good yield. The products were isolated without using any column chromatography. The catalyst could be separated by using an external magnet and the recovered catalyst could be reused for four consecutive cycles with negligible loss in its catalytic activity. Broad functional group tolerance, mild reaction condition, easily accessible starting materials, utilization of green reaction medium, recyclability of the catalyst up to further reaction without affecting the outcome of the reaction, gram-scale synthesis are some of the salient features of this strategy. � 2021 The Author(s)Item Graphitic Carbon Nitride Composites with MoO3-Decorated Co3O4Nanorods as Catalysts for Oxygen and Hydrogen Evolution(American Chemical Society, 2021-10-22T00:00:00) Ahmed, Imtiaz; Biswas, Rathindranath; Patil, Ranjit A.; Halder, Krishna Kamal; Singh, Harjinder; Banerjee, Biplab; Kumar, Bhupender; Ma, Yuan-Ron; Haldar, Krishna KantaWe have prepared a graphitic carbon nitride (g-C3N4) composite with MoO3-decorated Co3O4 nanorods (Co3O4/MoO3/g-C3N4) via the hydrothermal approach, and this hybrid material acts as a highly active and durable electrocatalyst for water splitting reactions. This material could fundamentally influence the catalytic processes and performance of oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). The OER and HER activities of Co3O4-/MoO3-based nanorods are enhanced by blending with conducting support, for example, graphitic carbon nitrides (g-C3N4). The X-ray diffraction pattern and the attenuated total reflectance-Fourier transform infrared data revealed that the as-synthesized nanorods are highly crystalline in nature and are attached to the g-C3N4 support. Transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy studies also affirm the successful heterointerface formation between Co3O4/MoO3 nanorods and g-C3N4. This Co3O4/MoO3/g-C3N4 rod-shaped catalyst is highly stable in comparison to its individual constituent and generates a current density of 10 mA cm-2 at a low overpotential of 206 mV for OER and 125 mV for HER in alkaline and acidic media, respectively. This work could pave the way for developing Co3O4/MoO3/g-C3N4 composite materials as electrocatalysts for overall water splitting reactions. � 2021 American Chemical Society. All rights reserved.