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Item Crystal structure of N-(2-hydroxynapthylidene)-l-isoleucinyl-4,6-o-ethylidene-β-d-glucopyranosylamine and an insight from experimental and theoretical calculations(Wiley, 2022-12) Sah, Ajay KumarDimethyl sulfoxide solution of N-(2-hydroxynapthylidene)-L-isoleucinyl-4,6-O-ethylidene-β-D-glucopyranosylamine (L1) affords single crystals of its ketoenamine configuration. The noncovalent intermolecular interactions present in the molecules have been explored by Hirshfeld surface analysis and 2D fingerprint plots generated using crystallographic data. The structural parameters of L1 in both the tautomeric forms (ketoenamine and phenolimine) at ground states have been optimized using Hartree–Fock and density functional theory calculations in gaseous and solution phases. The Fourier transform infrared, nuclear magnetic resonance, and UV–visible spectra of this molecule have been compared with the theoretically calculated data of both the tautomeric forms. Additionally, Mulliken population analysis, molecular electrostatic potential, and natural bond order analysis provide a better understanding of charge distribution, presence of electrophilic/nucleophilic sites, and intramolecular charge transfer, respectively, in the molecule.Item Synthesis of catalyst using bio-benign precursors and its application in one-pot catalytic synthesis of imidazo[1,2-a ]Pyridines(Wiley, 2023-03) Sah, Ajay KumarDevelopment of catalysts using natural feedstock is the need of the current era, and accordingly, we have developed a new ligand N-(2-hydroxynapthylidene)-L-leucienyl-4,6-O-ethylidene-β-D-glucopyranosylamine using natural occurring D-glucose and L-amino acid. It interacts with several bio-relevant metal ions like iron, copper, zinc, etc., but its association with cupric ions is immune to pH (4.2–9.1) change. In-situ copper-catalyzed reactions have been proven to be pivotal in many important organic syntheses, including imidazo[1,2-a]pyridines, which is one of the important precursors of many drug molecules. Catalytic synthesis of imidazo[1,2-a]pyridines requires high catalyst loading, hazardous solvent, high temperature, and long reaction time, which are major drawbacks towards green synthetic methodology. Interestingly, our glycoconjugate-derived cupric complex catalyzes the reactions among aldehydes, 2-aminopyridines, and terminal alkynes under the solvent-free condition to afford one-pot synthesis of imidazo[1,2-a]pyridines and 23 derivatives have been reported in good to excellent yields (53–93 %) using lower reaction time, temperature, and catalyst loading compared to other reports on similar reactions. Hence, our approach enhances the green methodology towards the catalytic synthesis of imidazo[1,2-a]pyridine derivatives.Item Synthesis, structural elucidation, and catalytic evaluation of glucopyranosylamine-derived Mo(VI) complex(Elsevier, 2024-01) Sah, Ajay KumarA new glucopyranosylamine-derived ditopic ligand (bis(4,6-O-ethylidene-β-d-glucopyranosylamine)-1,4-dihydroxy-2,5-dibenzylidene (H6L)) and it's coordinatively flexible dinuclear octahedral molybdenum complex ((MoO2)2H2L(D)2, (D = solvent)) has been synthesised. Recrystallization of the complex from dimethylformamide (DMF) yielded single crystals of coordination polymer (CP) [(MoO2)2H2L(DMF)]n, where the sixth coordination sites are occupied by Glu-OH3 and DMF. The solution-state studies revealed the presence of a discrete system, while the solid-state studies supported the polymeric nature, which is backed by density functional theory (DFT) calculations. To the best of our knowledge, this is the first report on the polymeric molybdenum complex of glucopyranosylamine-derived ligand. The experimental spectral data of Mo-complex matches with the theoretically generated spectra/values within the accepted range. The quantum chemical calculation for cooperative effect (νce) revealed the affinity of both the metal centers for the ligand's electron density, causing the largest weakening of the axial bond formed by the solvent molecule. This fact has been further evaluated experimentally by exploring the catalytic aspects of dinuclear Mo(VI) complex.Item Glucoconjugated dinuclear copper(ii) complex: an efficient catalyst for stereoselective synthesis of trisubstituted propargylamines via solvent-free A3 coupling reaction(Wiley, 2024-08) Sah, Ajay KumarDevelopment of catalytic systems using nontoxic natural precursors is the need of the era, and along this line, we have synthesized a new D-glucose derived ligand (4,6-O-ethylidene-N-(2-hydroxy-4-(octyloxy)benzylidene)-β-D-glucopyranosylamine) and its dinuclear copper(II) complex. The molecular structure of the complex has been established by single-crystal X-ray diffraction studies and detailed noncovalent intermolecular interactions present in it have been explored by Hirshfeld surface analysis. Further, the complex has been used as a catalyst in the enantioselective (87–99 % ee) synthesis of propargylamines in good to excellent yield (82–95 %) via aldehyde-amines-alkynes (A3) coupling reaction under solvent-free condition. The formation of aminal intermediate during the reaction has been confirmed by 1H-NMR and single-crystal X-ray diffraction studies. The catalytic system is reusable without any appreciable loss in the enantioselectivity or product yield.Item Metal-free synthesis of aminomethylated imidazoheterocycles: dual role of tert-butyl hydroperoxide as both an oxidant and a methylene source(RSC, 2018) Kumar, Anil; Sah, Ajay KumarA novel and efficient aminomethylation approach has been developed for the regioselective functionalization of imidazoheterocycles under metal-free conditions. A wide range of imidazoheterocycles and 2/4-aminoazaheterocycles successfully provided corresponding aminomethylated imidazoheterocycles in moderate to excellent (33–80%) yields. The isotopic labelling study suggested that TBHP played a dual role as both an oxidant and a methylene source in this transformation. The developed protocol follows a radical pathway which is supported by radical trapping experiments.Item N-Glycosylamines of 4,6-O-ethylidene-α-D-glucopyranose: synthesis, characterisation and structure of CO2H, Cl and F ortho-substituted phenyl derivatives and metal ion complexes of the CO2H derivative(RSC, 2000) Sah, Ajay KumarA saccharide based ligand suitable for metal binding (HLCOOH) has been synthesized using 4,6-O-ethylidene-α-D-glucopyranose (4,6-O-EGP) and anthranilic acid. A few analogous glycosylamines with chloro and fluoro ortho substitutions have also been synthesized and characterised. Complexes of HLCOOH with Na+, K+, Mg2+, Ca2+, Ba2+, Cd2+ and Hg2+ have been isolated and characterised fully. The crystal structures of 4,6-O-EGP, the chloro analogue of HLCOOH and the K+ complex of LCOOH are established. The anomeric nature, orientation of the binding core and the co-ordination aspects of K+ have been derived from these structures.Item First Crystallographic Investigation of Complexes of cis-VO2+, cis-MoO22+, and trans-UO22+ Species with Schiff-Base Molecules Derived from 4,6-O-Ethylidene-β-D-glucopyranosylamine(EJIC, 2001-09) Sah, Ajay KumarThe interaction of Schiff-base ligands derived from 4,6-O-ethylidene-β-D-glucopyranosylamine with cis-VO2+, cis-MoO22+, and trans-UO22+ species have been studied by isolating and characterizing the corresponding products. The structures of one complex of each type of species have been established by single-crystal X-ray diffraction analysis. In all the complexes, the saccharide moiety adopts a chair conformation and has a β-anomeric form. A gradual increase in coordination number (5, 6, and 7) and a gradual variation in the geometry (distorted trigonal-bipyramidal, distorted octahedral, and pentagonal-bipyramidal) are observed on going from the complexes of cis-VO2+ (mononuclear) to cis-MoO22+ (mononuclear) to trans-UO22+ (dinuclear). A variation in the binding mode of the ligand towards these dioxometal species is also observed. Intermolecular interactions of the type O−H···O, C−H···O, and N−H···O present in the lattices of these complexes lead to the formation of interesting structures.Item Synthesis, characterization and the first crystal structure of the Zn(II) complex of 4,6-O-ethylidine-N-(2-hydroxybenzylidene)-β-d-glucopyranosylamine(Elsiever, 2001-12) Sah, Ajay Kumar4,6-O-Ethylidine-N-(2-hydroxybenzylidene)-β-d-glucopyranosylamine (H3L1) and N-(5-bromo-2-hydroxybenzylidene-4,6-O-ethylidine-β-d-glucopyranosylamine (H3L2) molecules possessing a C-1NC(H) moiety for metal-ion binding were synthesized by condensing the 4,6-O-ethylidene-β-d-glucopyranosylamine with salicylaldehyde or 5-bromosalicylaldehyde. Complexes of these ligands with Zn(II) were isolated and characterized using elemental analysis, FTIR, UV–Vis absorption, NMR spectroscopic and FAB mass spectrometric techniques. The structure of the Zn(II) complex derived from H3L1 was established for the first time by a single-crystal X-ray diffraction study. The anomeric nature of the saccharide moiety was established based on 1H NMR studies and was confirmed by the crystal structure. Further, the structure and binding aspects of the ligand, and the coordination features of this in its Zn(II) complex were derived from the corresponding crystal structure.Item Structure of the first tetranuclear Ni(II) complex derived from N-(2-hydroxybenzylidene)-4,6-O-ethylidene-β-D-glucopyranosylamine(Chemical Society of Japan., 2001) Sah, Ajay KumarIn order to understand the binding nature of the glycosylamines possessing imine functionality, a novel tetranuclear Ni(II) complex of N-(2-hydroxybenzylidene)-4,6-O-ethylidene-β-D-glucopyranosylamine having twisted Ni4O4 cubane core was synthesized and structurally characterized.Item Crystal structure of 4,6-O-ethylidene-N-(2-hydroxybenzylidene)-β-d-glucopyranosylamine(Elsiever, 2002-01) Sah, Ajay Kumar4,6-O-Ethylidene-N-(2-hydroxybenzylidene)-β-d-glucopyranosylamine was synthesized and characterized using analytical, spectral and single-crystal X-ray diffraction methods. The anomeric nature of the saccharide moiety was proposed based on 1H NMR studies and was confirmed by the crystal structure. The lattice structure of this compound was compared with that of its analogues