Browsing by Author "Dhananjay Kumar"

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A highly expeditious synthesis of a bicyclic iminosugar using the novel key step of [NMM]+[HSO4]- promoted conjugate addition and Mitsunobu reaction
(2013) Virendra Prasad; Dhananjay Kumar; Vinod K. Tiwari
A simple and highly facile protocol has been developed for the stereoselective synthesis of 1-deoxy-norcastanospermine from readily available d-glucose. N-Methylmorpholinium hydrogen sulphate was seen for the first time as a suitable catalyst for the facile conjugate addition of an amine to a glycosyl olefinic ester. Furthermore, the key step of this strategy is the internal reductive amination of glycosyl azetidine, obtained from glycosyl β-amino alcohol under Mitsunobu reaction conditions. © 2013 The Royal Society of Chemistry.
An efficient one-pot synthesis of: N, N ′-disubstituted ureas and carbamates from N -acylbenzotriazoles
(Royal Society of Chemistry, 2016) Anoop S. Singh; Dhananjay Kumar; Nidhi Mishra; Vinod K. Tiwari
A facile and high-yielding one-pot synthesis of carbamates and N,N′-disubstituted symmetrical ureas from N-acylbenzotriazoles has been devised. It is believed that, the intermediate acyl-azide undergo Curtius rearrangement and in different solvents gives different products i.e. carbamates in alcohols and N,N′-disubstituted symmetrical urea in THF. © The Royal Society of Chemistry 2016.
An Improved Synthetic Protocol for Benzothiazoles via Ring Opening of Benzotriazole
(Wiley-Blackwell, 2018) Dhananjay Kumar; Anoop S. Singh; Vinod K. Tiwari
An improved procedure for the construction of benzothiazole scaffold via intramolecular cyclative cleavage of benzotriazole ring under free radical condition was successfully accomplished. The protocol utilises NaBH4 which regenerates the active reagent n-Bu3SnH in the reaction medium and makes this method cost effective and less toxic as a substitute of expensive and toxic silanes. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
An unexpected p-Toluenesulfonic acid catalyzed 1,3-migration of thiocarbonyl: Selective formation of 1,3-dioxolane-2-thione ring and optimization study
(Association of Carbohydrate Chemists and Technologists, 2014) Dhananjay Kumar; Anoop S. Singh; Vinod K. Tiwari
The selective opening of 5, 6-O-acetal of 3-O-(1,2: 5,6-di -O-i sopropylidine-α-D-gl ucofuranose)-1H-benzo [d][1,2,3]triazole-1-carbothioate (3) afforded bis(1,2-O-isopropylidene-5,6-thionocarbonato-α-D-glucofuranose (5) as a sole crystalline product. The reaction involved the treatment of 3 with p-toluenesulfonic acid in CH2 Cl2 at ambient temperature for 12 h giving compound 5 in 96% yield via 1,3-migration of thiocarbonyl moiety. The optimization study further revealed that the five membered dioxolane-2-thione ring was stabilized over six member ring by 8.78 kcal/mol.
An unprecedented deoxygenation protocol of benzylic alcohols using bis(1-benzotriazolyl)methanethione
(Royal Society of Chemistry, 2015) Dhananjay Kumar; Anoop S. Singh; Vinod K. Tiwari
A facile and regioselective two-step protocol for the deoxygenation of benzylic alcohols using bis(benzotriazole)methanethione has been devised. Benzotriazole derivatives, namely, benzyloxythioacylbenzotriazoles (ROCSBt), on reaction with silanes or Bu3SnH under microwave irradiation or conventional heating undergo a free radical β-scission of C-O bond instead of N-N bond (benzotriazole ring cleavage) to afford a deoxy product. The methodology has various applications because it selectively deoxygenates benzylic alcohols with the aid of a relatively nontoxic (TMS)3SiH reagent as an acceptable alternate to Bu3SnH. © The Royal Society of Chemistry 2015.
An Unprecedented Synthesis of N-Phenyl Amides via Cleavage of Benzotriazole Ring under Free Radical Condition
(Wiley-Blackwell, 2017) Anoop S. Singh; Dhananjay Kumar; Nidhi Mishra; Vinod K. Tiwari
An attempt of Bu3SnH mediated cyclization of acylbenzotriazoles (RCOBt) to corresponding benzoxazole failed; instead, corresponding N-phenylamides were achieved in good yield. The reactions proceed via reductive cleavage of benzotriazole ring with consequent evolution of molecular nitrogen (N2). A diverse range of amide has been achieved in high yields. Structures of all the compounds have been elucidated using IR, MS, 1H and 13C NMR, while four of them (3 o, 3 w, 4 and 5) have also been characterized by single crystal X-ray analysis. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chemical reaction- and particle diffusion-based kinetic modeling of metal biosorption by a Phormidium sp.-dominated cyanobacterial mat
(2011) Dhananjay Kumar; J.P. Gaur
The present study explores the suitability of chemical reaction-based and diffusion-based kinetic models for defining the biosorption of Cu(II), Cd(II) and Pb(II) by Phormidium sp.-dominated mat. The time-course data of metal sorption by the test mat significantly (r2=0.932-0.999) fitted to the chemical reaction-based models namely pseudo-first-order, -second-order, and the general rate law. However, these models fail to accurately describe the kinetics of metal biosorption due either to prefixed order or unjustifiable change in rate constant and reaction order with varying concentrations of metal and biomass in the solution. The diffusion-based models, namely, the intra-particle diffusion model and the external mass transfer model fitted well to the time-course metal sorption data, thus suggesting involvement of both external and intra-particle diffusion processes in sorption of test metals by mat biomass. However, the Boyd kinetic expression clearly showed that the external mass transfer is the dominant process. © 2010 Elsevier Ltd.
Click chemistry inspired highly facile synthesis of triazolyl ethisterone glycoconjugates
(2014) Dhananjay Kumar; Kunj B. Mishra; Bhuwan B. Mishra; Saheli Mondal; Vinod K. Tiwari
Numerous deoxy-azido sugars 3 were prepared by the reaction of tosyl/bromo sugars with NaN3 in dry DMF under heating condition. The 1,3-dipolar cycloaddition of deoxy-azido sugars 3 with ethisterone 4 to afford regioselective triazole-linked ethisterone glycoconjugates 5 was investigated in the presence of CuI and DIPEA in dichloromethane or CuSO4· 5H2O and sodium ascorbate in aqueous medium. All the developed compounds were characterized by spectroscopic analysis (IR, 1H & 13C NMR, and MS spectra). Structure of triazolyl ethisterone glycoconjugate 5a has been further confirmed by its Single Crystal X-ray analysis. © 2013 Elsevier Inc. All rights reserved.
Click Chemistry Inspired Synthesis of Hydroxyanthracene Triazolyl Glycoconjugates
(American Chemical Society, 2022) Nishant Pandey; Pratibha Dwivedi; Jyoti; Mangat Singh; Dhananjay Kumar; Vinod K. Tiwari; Bhuwan B. Mishra
Novel hydroxyanthracene-based terminal alkynes 3 and 5a/b were synthesized by the acetylide addition reaction at the 9,10-position of anthraquinone 1 under mild conditions. The developed alkynes 3, 5a, and 5b on Huisgen azide-alkyne cycloaddition reaction with azido-sugars 6 in the presence of Cu(I) catalyst provided a series of triazole fasten hydroxyanthracene glycoconjugates 7, 8, and 9, respectively, in good yields. The representative compounds 9 and 7h were successfully deprotected under room-temperature conditions to liberate the corresponding free glycoconjugates 10 and 11, respectively. Further, structures of a few compounds were unmaliciously evidenced by their single-crystal X-ray. © 2016 American Chemical Society.
Comprehensive analysis of structural, morphological, surface chemistry, and optical traits of multifaceted SrTiO3 for enhanced photocatalytic and DSSC applications
(Elsevier Ltd, 2025) Satyam Upadhyay; Monika Srivastava; Pradyum Patel; Amit Kumar Srivastava; Dhananjay Kumar; Somnath C. Roy; Sanjay Kumar Srivastava
The present study underlines the facile synthesis of SrTiO3 nanoparticles through sol-gel approach and subsequently its dual applicability as photocatalyst for methylene blue degradation and photoanode in dye-sensitized solar cell fabrication. Structural and optical characterizations, including XRD with Rietveld refinement, SEM, TEM, XPS, Raman, UV–Vis, and PL spectroscopy, confirms a cubic perovskite phase with an optical bandgap of ∼3.24 eV. The ST NPs demonstrates enhanced photocatalytic activity under visible light, degrading ∼56.13 % of 10 ppm MB in 120 min. Kinetic studies under UV light further validated the degradation mechanism. As photoanodes in DSSCs, the ST NPs exhibit enhance photocurrent responses, especially when combined with natural pomegranate dye, suggesting their viability for renewable energy devices. These findings highlight the potential of strontium titanate nanoparticles for both photocatalytic applications and dye-sensitized solar cell fabrication, offering an eco-friendly and effective solution to address energy and environmental challenges. © 2025 Elsevier Ltd
Continuous metal removal from solution and industrial effluents using Spirogyra biomass-packed column reactor
(Elsevier Ltd, 2012) Alpana Singh; Dhananjay Kumar; J.P. Gaur
The granules of Spirogyra neglecta biomass, diameter 0.2-0.5. mm, were successfully prepared by boiling it in urea-formaldehyde mixture. Metal sorption performance of the column packed with Spirogyra granules was assessed under variable operating conditions, such as, different influent metal concentrations, bed heights and flow rates. These conditions greatly influenced the breakthrough time and volume, saturation time and volume, and the ability of the column to attain saturation after reaching the breakthrough. The experimental breakthrough curves obtained under varying experimental conditions were modeled using Bohart-Adams, Wolborska, Thomas, Yoon-Nelson and modified dose-response models. The first two models were valid only in representing the initial part of the breakthrough curves; however, the other three models were good in representing the entire breakthrough curve. The granule-packed column could be successfully used up to 6 and 9 cycles of sorption and desorption for the removal of Cu(II) and Pb(II), respectively. The column could efficiently remove different metals from real industrial effluents, and hence the test biomass (Spirogyra granules) is a good candidate for commercial application. © 2011 Elsevier Ltd.
Copper(II) and lead(II) sorption from aqueous solution by non-living Spirogyra neglecta
(2007) Alpana Singh; Dhananjay Kumar; J.P. Gaur
Dried biomass of Spirogyra neglecta rapidly sorbed the test metals and the process became saturated in 10-20 min. Maximum sorption of Pb(II) [116.1 mg g-1] and Cu(II) [115.3 mg g-1] occurred at 0.1 g l-1 biomass and 100 mg l-1 metal concentration in the solution. Sorption of Cu(II) and Pb(II) occurred optimally at pH 4.5 and 5.0, respectively. Lead(II) and Cu(II) sorption were lesser from binary metal solution than from single metal solution. Lead(II) more severely inhibited Cu(II) sorption than vice versa thus reflecting greater affinity of Pb(II) for the biomass. NaOH pretreatment slightly enhanced the metal removal ability of the biomass. During repeated sorption/desorption cycles, Pb(II) and Cu(II) sorption decreased by 11% and 27%, respectively, at the end of the fifth cycle due inter alia to 10-15% loss of biomass. Nevertheless, Spirogyra appears to be a good sorbent for removing metals Cu(II) and Pb(II) from wastewaters. © 2006 Elsevier Ltd. All rights reserved.
Cyclo-Release Strategy in Solid-Phase Combinatorial Synthesis of Heterocyclic Skeletons
(Academic Press Inc., 2012) Bhuwan B. Mishra; Dhananjay Kumar; Amrita Mishra; Prabhu P. Mohapatra; Vinod K. Tiwari
The recent advent of high-throughput, automated techniques combined with the identification of new therapeutic targets emerging from numerous efforts in the field of genome sequencing and molecular biology has generated a need of large collections of diverse heterocyclic scaffolds that have stipulated the development of novel reaction sequences and linking strategies to access the diverse range of complex heterocyclic systems. Combinatorial chemistry in this regard has emerged as a technology platform for the rapid assemblage of building blocks to generate quite complex structures in few synthetic steps. With the implementation of high-throughput screening for biological evaluation of hits and leads, combinatorial libraries have become very important for pharmaceutical and agricultural chemistry.The cyclo-release strategy that minimizes the chemical and tethering implication by releasing the intact desired target molecule in the final step of reaction is gaining widespread popularity over the last 20 years. Toward this end, there has been a particular interest in developing linking strategies whereby the loading and cleavage steps contribute to the complexity of the target structure rather than merely constituting extraneous manipulations. The present review highlights the practically high-yielding and high-purity approach for the solid-phase combinatorial synthesis of diverse pharmacologically active heterocyclic skeletons dealing with cyclo-release strategy. © 2012 Elsevier Inc.
Dairy value chain and critical stakeholders for added value products
(Elsevier, 2025) Dhananjay Kumar; Sadhana Ojha
The resilience of the dairy value chain is crucial for ensuring food security and sustaining socio-economic growth, particularly in emerging economies like India. The primary processes in this chain include milk production, collection, processing, and sales/distribution, all supported by various ancillary activities. This value chain provides self-employment, empowers women, and offers economic benefits to many poor milk producers. By effectively managing the dairy value chain, it is possible to overcome the limitations posed by agriculture, such as land and seasonal constraints. Economies of scale can gradually reduce these constraints, enhancing market access and driving growth in the dairy sector. Adopting a Three P's approach (People, Planet, and Profit) allows milk producer organizations to tackle sector challenges more comprehensively. This can be achieved through systematic production, services, risk assessment, and regular reviews involving core stakeholders. Such an approach ensures that the value chain remains robust and beneficial for all parties involved. © 2025 Elsevier Inc. All rights reserved.
Diacetoxyiodobenzene mediated one-pot synthesis of diverse carboxamides from aldehydes
(2012) Virendra Prasad; Raju R. Kale; Bhuwan B. Mishra; Dhananjay Kumar; Vinod K. Tiwari
A novel, one-pot, and highly facile protocol has been devised for an easy access of a series of novel glycosyl carboxamides from aldehydes using diacetoxyiodobenzene in the presence of ionic liquid at ambient temperature. © 2012 American Chemical Society.
Erratum: Synthesis of 2-N/S/C-substituted benzothiazoles via intramolecular cyclative cleavage of benzotriazole ring
(2014) Dhananjay Kumar; Bhuwan B. Mishra; Vinod K. Tiwari
[No abstract available]
Eu:Y2O3 highly dispersed fluorescent PVA film as turn off luminescent probe for enzyme free detection of H2O2
(Elsevier B.V., 2017) Dhananjay Kumar; Sima Umrao; Himanshu Mishra; Rohit Ranjan Srivastava; Monika Srivastava; Anchal Srivastava; S.K. Srivastava
In this work, a novel sensing scaffold consisting highly dispersed Eu:Y2O3 fluorescent flexible film of poly vinyl alcohol (EYCP) was synthesized by simple mixing method and applied to facilitate non-enzymatic detection of hydrogen peroxide (H2O2) by turn off probe of fluorescence. The fluorescence spectra of EYCP consisting number of emission sharp transitions from excited, 5D0→7Fj (j = 0, 1, 2, 3, 4) energy levels of doped Eu3+ ion in Y2O3 host. In the presence of H2O2, the fluorescence intensity of the EYCP film was quenched due to the reduction of electron–hole pair recombination in Eu centers by electron transfer from Eu–O excited state to H2O2 energy level rather than 5D0 state of Eu3+, which reduces the number of electron in 5D0 state. The EYCP film shows excellent fluorescence quenching in presence of H2O2 by significantly increasing concentration of H2O2 and completely quenched at ∼150 μM. A linear relationship is observed between 0.0 and 60 μM with a correlation coefficient of 0.989. H2O2 sensing is also compared with the EYC nanoparticles. This study is expected to have a significant impact on further study of the Eu:Y2O3 fluorescent flexible film for wide range applications. © 2017 Elsevier B.V.
Evaluation of various isotherm models, and metal sorption potential of cyanobacterial mats in single and multi-metal systems
(2010) Dhananjay Kumar; Lalit K. Pandey; J.P. Gaur
Isotherm curves for the biosorption of Cu(II), Cd(II) and Pb(II) by the biomass of five different cyanobacterial mats (Mat # 1-5) showed concave shape and plateau. Suitability of ten different isotherm models was evaluated for the equilibrium modeling of these isotherm curves, however, only the Toth model was found appropriate. Mat # 2, dominated by Phormidium sp., was identified as an excellent metal biosorbent because: (i) the Toth estimated maximum biosorption capacity (mmolg-1) of Mat # 2 for Pb(II) (1.028), Cu(II) (0.696) and Cd(II) (0.549) was the highest among the tested mats and compares favourably with Langmuir estimated metal sorption capacity of many seaweeds, regarded as the best metal biosorbents, (ii) Na+, K+ and Ca2+ did not substantially inhibit the biosorption of the test metals, (iii) and total metal sorption ability of Mat # 2 increased or remained unaffected in binary and ternary metal systems. © 2010 Elsevier B.V.
Gender Matters: Reappraising the Issues of Equity, Participation and Ownership in Watershed Management
(SAGE Publications Inc., 2022) Dhananjay Kumar; Dhiraj Kumar
Equal share in governance of managing natural resources is one of the strategic aspects of neoliberal developmentalism. Additionally, this process of natural resource governance (NRG) considers communities as a homogeneous entity by ignoring the cultural politics of gender division to maintain the latency and equilibrium of the existing gendered order and regime. Watershed developmental project is no exceptional in this regard. The existing empirical literature shows that the gender governance (GG) issues in development projects such as watershed is disproportionate between men and women. This article talks about GG by discussing the issues of equity, participation and ownership in NRG, and it argued that GG cannot be synonymous with gender mainstreaming. Watershed development in India has been taken to address the issues of conservation and production, but it doesn’t address the cultural politics of gendered division. Women are more inclined to be marginalized in the governance of watershed management due to the cultural politics of control and access over the ownership of the natural resource (land) which comes under the hegemonic control of their male counterparts. Women participation in watershed activities is merely for fulfilling the custom of the official quota. Considering the potential function of women participation in watershed activities, the present article seeks to explore the issues and approaches through which the participatory institutions must meet the emerging challenges. This study concludes that the role of women participation in NRG will help in the integration of various form of capital more effectively. © 2022 Indian Institute of Management, Ahmedabad.
Gold nanorods modified Eu: Y2O3 dispersed PVA film as a highly sensitive plasmon-enhanced luminescence probe for excellent and fast non-enzymatic detection of H2O2 and glucose
(Elsevier GmbH, 2021) Dhananjay Kumar; Arpita Dwivedi; Monika Srivastava; Anchal Srivastava; Amit Srivastava; S.K. Srivastava
This article addresses a high sensitivity, non-invasive, and use-throw in nature type biocompatible Eu: Y2O3 dispersed PVA film with gold nanorod (AEYCP film) fluorescent sensing probe for non-enzymatic detection of hydrogen peroxide (H2O2) and glucose (C6H12O6). The fluorescence spectra of the as-synthesized AEYCP fluorescent film consist of some sharp emission (most intense peak at ∼611 nm, owing to the 5D0-7F2 transition) which corresponds to electrical and magnetic dipole transitions. In the presence of H2O2 and glucose, the fluorescence intensity of the AEYCP film gets quenched due to the reduction of electron-hole pair, at the Eu center. The AEYCP film shows excellent fluorescence quenching in the presence of H2O2 at ∼500 nM (with a low detection limit of 1.80 × 10−9 M) and glucose (with a low detection limit 1.60 × 10-6 M). Herein, we envision that our result provides an insight for the synthesis of rare earth metal-doped oxide flexible,non-enzyme mimicking fluorescent probe for different biomedical applications. © 2020 Elsevier GmbH