Department of Chemistry
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Item Copper-catalysed Csingle bondN/Csingle bondO coupling in water: a facile access to N-coumaryl amino acids and fluorescent tyrosine & lysine labels(Elsiever, 2016-06) Bajaj, Kiran; Sakhuja, RajeevA mild, efficient, ligand free and environmentally benign approach towards the construction of sp2 C-sp3 N bond has been developed via copper catalysed Ullmann type of coupling between 4-chlorocoumarin with N-terminus unprotected amino acids in microwave-aqua conditions, yielding a series of N-coumaryl amino acids in good to excellent yields. Excellent photo-physical properties exhibited by these N-coumaryl amino acids and their chemical applicability as C-terminus coupling partners for N-terminus peptides make them potential fluorescent probes in labelling studies. The methodology was extended towards the Csingle bondO and Csingle bondN coupling for the synthesis of fluorescent coumaryl labelled tyrosine and lysine labels respectively. Application of coumaryl labelled tyrosine was further explored towards the synthesis of fluorescent labelled opioid tetrapeptide, Endomorphin-2 derivative.Item Selective and Sensitive Recognition of Cu2+ in an Aqueous Medium: A Surface-Enhanced Raman Scattering (SERS)-Based Analysis with a Low-Cost Raman Reporter(Wiley, 2012-04-04) Basu, MrinmoyeeIn the present study, surface-enhanced Raman spectra of a bifunctional Raman reporter, 2-mercaptobenzimidazole, has been found to be responsive exclusively towards Cu(2+) ions while the reporter remains anchored on the Au nanoparticle surface. Thus a specific Cu(2+)-ion-detection protocol emerges. The simplicity, sensitivity, and reproducibility of the method allow routine and quantitative detection of Cu(2+) ions. An interference study involving a wide number of other metal ions shows the procedure to be uniquely selective and analytically rigorous. A theoretical study was carried out to corroborate the experimental results. Finally, the method is promising for real-time assessment of Cu(2+) ions in aqueous samples and also has the ability to discriminate Cu(I) and Cu(II) ions in solution.Item Copper triflate-mediated synthesis of 1,3,5-triarylpyrazoles in [bmim][PF6] ionic liquid and evaluation of their anticancer activities(RSC, 2013) Kumar, AnilA simple, efficient, and environment friendly protocol for the synthesis of 1,3,5-triarylpyrazoles and 1,3,5-triarylpyrazolines in [bmim][PF6] ionic liquid mediated by Cu(OTf)2 is described. The reaction protocol gave 1,3,5-triarylpyrazoles in good to high yields (71–84%) via a one-pot addition–cyclocondensation between chalcones and arylhydrazines, and oxidative aromatization without the requirement for an additional oxidizing reagent. The catalyst can be reused for up to four cycles without much loss in the catalytic activity. The pyrazoles (4a–o) and pyrazolines (3a–n) were evaluated for their antiproliferative activity in SK-OV-3, HT-29, and HeLa human cancer cells lines. Among all the compounds, 3b inhibited cell proliferation of HeLa cells by 80% at a concentration of 50 μM.Item Copper-Catalyzed Tandem Azide–Alkyne Cycloaddition, Ullmann Type C–N Coupling, and Intramolecular Direct Arylation(ACS, 2013) Kumar, Anil; Khungar, BhartiA ligand-free copper-catalyzed tandem azide–alkyne cycloaddition (CuAAC), Ullmann-type C–N coupling, and intramolecular direct arylation has been described. The designed strategy resulted in the synthesis of a novel trazole-fused azaheterocycle framework. The reaction gave good yields (59–77%) of 1,2,3-triazole-fused imidazo[1,2-a]pyridines in a single step.Item Ligand-Free, Copper-Catalyzed Ullmann-Type C–N Coupling: Regioselective Synthesis of Azole-Substituted Imidazo[1,2-a]pyridines(Thieme, 2013) Kumar, AnilA simple and highly efficient protocol for the regioselective synthesis of azole-substituted imidazo[1,2-a]pyridines has been developed using a ligand-free, copper-catalyzed Ullmann-type C–N coupling of 2-(2-bromophenyl)imidazo[1,2-a]pyridines with different azoles and in situ generated 1,2,3-triazoles. The reactions proceeded smoothly to furnish azolo-imidazo[1,2-a]pyridines in good to excellent yields (65–96%).Item Copper and palladium-catalyzed sequential reactions: one-pot synthesis of isoindolo[2,1-b]isoquinolin-7(5H)-ones(RSC, 2019) Kumar, AnilA highly efficient protocol has been developed for the synthesis of diversely substituted isoindolo[2,1-b]isoquinolin-7(5H)-ones through sequential Cu(II)-catalyzed Sonogashira coupling, intramolecular hydroamidation followed by palladium-catalyzed ligand-free Heck reaction. Good to excellent yields (41–94%) were observed with excellent substrate scope and functional group tolerance. The developed method represents a practical strategy for the construction of bioactive isoindolo[2,1-b]isoquinolin-7(5H)-ones.Item Tri- and Tetranuclear Copper(II) Complexes Consisting of Mononuclear Cu(II) Chiral Building Blocks with a Sugar-Derived Schiff's Base Ligand(ACS, 2006) Sah, Ajay KumarA new sugar-derived Schiff's base ligand N-(3-tert-butyl-2-hydroxybenzylidene)-4,6-O-ethylidene-β-d-glucopyranosylamine (H3L1) has been developed which afforded the coordinatively labile, alcoholophilic trinuclear Cu(II) complex [Cu3(L1)2(CH3OH)(H2O)] (1). Complex 1 has been further used in the synthesis of a series of alcohol-bound complexes with a common formula of [Cu3(L1)2(ROH)2] (R = Me (2), Et (3), nPr (4), nBu (5), nOct (6)). X-ray structural analyses of complexes 2−6 revealed the collinearity of trinuclear copper(II) centers with Cu−Cu−Cu angles in the range of 166−172°. The terminal and central coppers are bound with NO3 and O4 atoms, respectively, and exhibit square-planar geometry. The trinuclear structures of 2−6 can be viewed as the two {Cu(L1)}- fragments capture a copper(II) ion in the central position, which is further stabilized by a hydrogen-bonding interaction between the alcohol ligands and the sugar C-3 alkoxo group. Complex 2 exhibits a strong antiferromagnetic interaction between the Cu(II) ions (J = −238 cm-1). Diffusion of methanol into a solution of complex 1 in a chloroform/THF mixed solvent afforded the linear trinuclear complex [Cu3(L1)2(CH3OH)2(THF)2] (7). The basic structure of 7 is identical to complex 2; however, THF binding about the terminal coppers (Cu−OTHF = 2.394(7) and 2.466(7) Å) has introduced the square-pyramidal geometry, indicating that the planar trinuclear complexes 2−6 are coordinatively unsaturated and the terminal metal sites are responsible for further ligations. In the venture of proton-transfer reactions, a successful proton transfer onto the saccharide C-3 alkoxo group has been achieved using 4,6-O-ethylidene-d-glucopyranose, resulting in the self-assembled tetranuclear complex, [Cu4(HL1)4] (8), consisting of the mononuclear Cu(II) chiral building blocks, {Cu(HL1)}.Item Saccharide derived dinuclear Cu(II) complex: An efficient catalyst for oxidation of catechol and benzylic alcohols(Elsiever, 2012-01) Sah, Ajay Kumar; Kumar, AnilCatalytical aspect of 4,6-O-ethylidene-β-D-glucopyranosylamine derived dinuclear Cu(II) complex has been explored. The complex exhibits good catecholase like activity and oxidizes model substrate 3,5-di-tert-butylcatechol to 3,5-di-tert-butyl-o-quinone. The complex also acts as selective catalyst to oxidize the primary and secondary alcohols to corresponding carbonyl compounds in excellent yield (65–82%) under mild conditions.Item Synthesis of cupric acetate selective receptor derived from alanyl glycoconjugate and their application in selective oxidation of benzylic alcohols(ACS, 2012-11) Sah, Ajay KumarCupric acetate sensing ability of alanyl-(4,6-O-ethylidene-β-D-glucopyranosylamine) derived receptor (L-N2O2) has been explored using fluorescence and UV–visible absorption spectroscopy. Cupric acetate quenches the fluorescence intensity of L-N2O2 with a correlation coefficient, R = 0.978 and Stern Volmer constant, KSV = 38,067 M− 1 revealing the possibilities of interaction via dynamic mode. Further, copper complex of L-N2O2 has been utilized in selective oxidation of primary and secondary alcohols into the corresponding carbonyl compounds.