Browsing by Author "Rama Kant"

Now showing 1 - 9 of 9

An efficient and economical synthesis of 5-substituted 1 H -tetrazoles via Pb(II) salt catalyzed [3+2] cycloaddition of nitriles and sodium azide
(Elsevier Masson SAS, 2016) Rama Kant; Vishal Singh; Alka Agarwal
A simple, mild and efficient method is developed for the synthesis of 5-substituted 1H-tetrazoles. Out of three used Pb(II) catalysts, lead chloride (PbCl2) has been found to be an efficient catalyst for [3+2] cycloaddition of NaN3 with aromatic and aliphatic nitriles to afford 5-substituted 1H-tetrazoles. The catalyst is reusable up to four cycles with consistent activity. The cost effectiveness and easy availability of the catalyst, simple methodology, excellent yield and easy work-up are the additional advantages. © 2015 Académie des sciences.
Crystallographic, Thermal and Hirshfeld Surface Studies of N-(1H-1,3-benzodiazol-2-yl)benzamide
(Springer India, 2017) Vishal Singh; Rama Kant; Alka Agarwal
In present study, the compound N-(1H-1,3-benzodiazol-2-yl)benzamide was synthesized and characterized by 1H NMR, IR, elemental and X-ray analysis. A good quality single crystal was grown by slow evaporation solution growth technique to investigate their X-ray structure. The compound crystallizes in a triclinic crystal system with space group P-1 and having the unit cell parameters of a = 10.2350(5) Ǻ, b = 14.7494(7) Ǻ, c = 24.2813(11) Ǻ, α = 79.084(4) °, β = 83.927(4) °, γ = 80.039(4) °, V = 3534.8(3) Å3and Z = 12. The molecules are arranged in a linear manner and crystal packing is stabilized by N–HO, N–HN, C–HO, C–H and intermolecular interactions. These interactions generate various hydrogen bond patterns e.g. R21(6), R22(10), R22(8), R21(7) and R44(30). Hirshfeld surface analysis suggests that the intermolecular HH, CH, NH and OH contacts are predominant. The thermal behavior of crystal was determined by DSC and TGA analysis. © 2017, The National Academy of Sciences, India.
Design, synthesis and biological evaluation of ciprofloxacin tethered bis-1,2,3-triazole conjugates as potent antibacterial agents
(Elsevier Masson SAS, 2016) Rama Kant; Vishal Singh; Gopal Nath; Satish Kumar Awasthi; Alka Agarwal
A series of new bis-1,2,3-triazole linked ciprofloxacin conjugates was designed, synthesized and evaluated in vitro antibacterial activity against a panel of clinically relevant bacteria. A significant part of the compounds displayed enhanced activity against both Gram-positive and Gram-negative species of bacteria as compared to the parent drug. Additionally, negligible toxicity profile of compounds indicates that they may act a good antibiotic in future. Despite relatively small number of synthesized conjugates, it was possible to observe important dependences between their structure and activity. © 2016 Elsevier Masson SAS
Hydrogen bonding patterns and DFT studies of (4-Acetylphenyl)amino 2,2-Dimethylpropanoate and (E)-1-(4-aminophenyl)-3-[4-(dimethylamino)phenyl] prop-2-en-1-one
(Springer New York LLC, 2014) Rama Kant; Biswajit Maiti; Satish Kumar Awasthi; Alka Agarwal
The (4-acetylphenyl)amino 2,2-dimethylpropanoate (1) and (E)-1-(4-aminophenyl)-3-[4-(dimethylamino)phenyl]prop-2-en-1-one (2), were synthesized and characterized by elemental analysis, FT-IR, 1H NMR, 13CNMR and single crystal X-ray diffraction techniques. Both compounds 1 and 2 crystallized in orthorhombic crystal system with Pbca and P212121 space group respectively, having the unit cell parameters: a = 11.7220(12) Å, b = 14.4580(13) Å, c = 15.7853(12) Å, β = 90°, Volume = 2675.2(4) Å3, Z = 8 for 1 and a = 6.1146(5) Å, b = 9.0567(8) Å, c = 26.079(3) Å, β = 90°, Volume = 1444.2(2) Å3, Z = 4 for compound 2. The crystal structures of both compounds (1 and 2) are stabilized by N-H···O strong intermolecular hydrogen bonding forming C 1 1 (8) motifs. In compound 1, the molecules are linked by three C-H···O intramolecular H-bond forming S(6) motifs. In compound 2, the molecules are linked by C-H···N intermolecular H-bond exhibiting C 1 1 (12) motif and C-H···O intramolecular H-bond leading to S(5) motif. Crystallographic and vibrational data are compared with the results of density functional theory (DFT) method at the B3LYP/6-31G(d,p) level. The electronic (UV-vis) spectra was calculated by using the TD-DFT method and correlated with experimental spectra. © 2014 Springer Science+Business Media New York.
Synthesis of newer 1,2,3-triazole linked chalcone and flavone hybrid compounds and evaluation of their antimicrobial and cytotoxic activities
(Elsevier Masson SAS, 2016) Rama Kant; Dharmendra Kumar; Drishti Agarwal; Rinkoo Devi Gupta; Ragini Tilak; Satish Kumar Awasthi; Alka Agarwal
The present study was carried out in an attempt to synthesize a new class of antimicrobial and antiplasmodial agents by copper catalyzed click chemistry to afford 25 compounds 10-14(a-e) of 1,4-disubstituted-1,2,3-triazole derivatives of chalcones and flavones. The structures of the newly synthesized compounds were established by elemental analysis, IR, 1H NMR, 13C NMR and Mass spectral data. The newly synthesized compounds were evaluated for their antibacterial activity against Gram positive bacteria (Staphylococcus aureus, Enterococcus faecalis), Gram negative bacteria (Escherichia coli, Pseudomonas aeruginosa, Shigella boydii, Klebsiella pneumoniae) and antifungal activity against (Candida albicans, Candida tropicalis, Candida parapsilosis, Cryptococcus neoformans, Dermatophyte) as well as molds (Aspergillus niger, Aspergillus fumigatus). The antiplasmodial and cytotoxic activities of these compounds were also evaluated against human malaria parasite Plasmodium falciparum strain 3D7 and human hepato-cellular carcinoma cells (Huh-7), respectively. Compounds 10a, 10c, 10d, 12c and 14e showed promising antibacterial activity while compounds 10e, 11d, 11e, 12c, 13a, 13b, 13e, 14a and 14d showed good antifungal activity as compared to the corresponding standard drugs. Compound 10b was found to be the most active against Plasmodium falciparum while the remaining compounds showed moderate to weak antiplasmodial activity. However, cytotoxic activities of all compounds were found ineffective against Huh-7 cells. © 2016 Elsevier Masson SAS. All rights reserved.
Synthesis, characterization, Hirshfeld surfaces and DFT computation of novel benzyl N-(1,3-benzothiazol-2-yl)-N-benzylcarbamate
(Elsevier B.V., 2017) Rama Kant; Biswajit Maiti; Alka Agarwal
The compound benzyl N-(1,3-benzothiazol-2-yl)-N-benzylcarbamate was synthesized from 2-aminobenzothiazole and characterized by FT-IR, NMR, UV–Vis, X-ray diffraction and quantum chemical calculations. The compound crystallizes in the monoclinic, space group P21, with unit cell parameters of a = 11.5904(18) Å, b = 5.5213(7) Å, c = 15.251(2) Å, β = 112.217(16)°, V = 903.5(2) Å3 and Z = 2. The weak intermolecular C[sbnd]H⋯O and C[sbnd]H⋯π hydrogen bonds stabilized the crystal structure. Hydrogen bonding patterns were investigated in proposed compound on the behalf of X-ray analysis and its assignment with recognized terminological notations. The optimized geometrical parameters, harmonic vibrational frequencies, electrostatic potential surface and Milliken charges were calculated using hybrid Density Functional Theory (DFT/B3LYP) method with 6-31 + G(d,p) basis set. 1H and 13C NMR chemical shifts were also calculated at the same level of theory. The TD-DFT calculations have been performed to explore the electronic absorption spectra. Our computed data are in good agreement with the experimental values. © 2017 Elsevier B.V.
Synthetic and Crystallographic Studies of (9-Ethyl-9H-carbazol-3-yl)-carbamic acid tert-butyl ester
(Springer India, 2015) Rama Kant; Vishal Singh; Alka Agarwal
The title compound (9-ethyl-9H-carbazol-3-yl)-carbamic acid tert-butyl ester was prepared from 3-amino-9-ethylcarbazole and di-tert-butyldicarbonate (Boc anhydride) in good yield. It was characterized by elemental analysis, FT-NMR, FT-IR spectroscopy and subjected to single crystal X-ray diffraction studies. The compound crystallizes in monoclinic space group P21/c with unit cell dimensions are a = 13.5218(8) Å, b = 12.7624(7) Å, c = 10.1352(6) Å, β = 100.784(6)°, V = 1718.15(17) Å3, Dx = 1.200 Mg m−3, and Z = 4. According to X-ray diffraction studies the molecule is in a non planar conformation except for the carbazole moiety and having a dihedral angle of 30.239(89)° between the plane of the carbazole and amide moieties. The molecules are packed in a zig-zag manner and strong N–H···O [C(4) motif] intermolecular hydrogen bonding, weak C–H···π [C(5) motif] and π–π stacking interaction stabilize the crystal packing. The thermal analysis of single crystal was determined by DSC and TGA. © 2015, The National Academy of Sciences, India.
The rigidity and chelation effect of ligands on the hydrogen evolution reaction catalyzed by Ni(ii) complexes
(Royal Society of Chemistry, 2023) Anjali Mishra; Gaurav Kumar Mishra; None Anamika; Nanhai Singh; Rama Kant; Kamlesh Kumar
With increasing interest in nickel-based electrocatalysts, three heteroleptic Ni(ii) dithiolate complexes with the general formula [Ni(ii)L(L′)2] (1-3), L = 2-(methylene-1,1′-dithiolato)-5,5′-dimethylcyclohexane-1,3-dione and L′ = triphenylphosphine (1), 1,1′-bis(diphenylphosphino)ferrocene (DPPF) (2), and 1,2-bis(diphenylphosphino)ethane (DPPE) (3), have been synthesized and characterized by various spectroscopic techniques (UV-vis, IR, 1H, and 31P{1H} NMR) as well as the electrochemical method. The molecular structure of complex 2 has also been determined by single-crystal X-ray crystallography. The crystal structure of complex 2 reveals a distorted square planar geometry around the nickel metal ion with a NiP2S2 core. The cyclic voltammograms reveal a small difference in the redox properties of complexes (ΔE° = 130 mV) while the difference in the catalytic half-wave potential becomes substantial (ΔEcat/2 = 670 mV) in the presence of 15 mM CF3COOH. The common S^S-dithiolate ligand provides stability, while the rigidity effect of other ligands (DPPE (3) > DPPF (2) > PPh3 (1)) regulates the formation of the transition state, resulting in the NiIII-H intermediate in the order of 1 > 2 > 3. The foot-of-the-wave analysis supports the widely accepted ECEC mechanism for Ni-based complexes with the first protonation step as a rate-determining step. The electrocatalytic proton reduction activity follows in the order of complex 1 > 2 > 3. The comparatively lower overpotential and higher turnover frequency of complex 1 are attributed to the flexibility of the PPh3 ligand, which favours the easy formation of a transition state. © 2024 The Royal Society of Chemistry.
Thermal and Crystallographic Studies of tert-Butyl 2-amino-1H-1,3-benzodiazole-1-carboxylate
(Springer India, 2016) Vishal Singh; Rama Kant; Alka Agarwal
tert-Butyl 2-amino-1H-1,3-benzodiazole-1-carboxylate was synthesized by the reaction of di-tert-butyl dicarbonate with 2-aminobenzimidazole in good yield. The compound was characterized by FT-NMR, FT-IR and single crystal X-ray diffraction. The compound crystallized in orthorhombic lattice with Pbca space group and having unit cell parameters of a = 15.5303(6) Å, b = 9.3643(4) Å, c = 17.2112(7) Å, V = 2503.03(18) Å3, Dx = 1.238 mg m−3 and Z = 8. The crystal structure of compound was stabilized by N–H···N and C–H···O intermolecular interactions. The molecules are arranged into zig-zag manner in a dimeric form by N2–H1A···N1 and C12–H12C···O intermolecular hydrogen bonding which exhibited center of symmetric (Formula presented.) and chain (Formula presented.) patterns respectively. The thermal analysis of crystal was determined by DSC and TGA. © 2016, The National Academy of Sciences, India.