BITS Faculty Publications
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Item Phenyliodine(III) Diacetate-Mediated 1,2-ipso-Migration in Mannich Bases of Imidazo[1,2-a]pyridines: Preparation of N-Acetoxymethyl/Alkoxymethyl-N-arylimidazo[1,2-a]pyridine-3-amines(ACS, 2020-05) Kumar, AnilPhenyliodine(III) diacetate -mediated 1,2-ipso-migration of an imidazo[1,2-a]pyridine ring via the formation of an aziridine intermediate in Mannich bases derived from imidazo[1,2-a]pyridines, 2-pyridylamines or arylamines, and formaldehyde is reported. The imidazo[1,2-a]pyridines bearing different substituents showed excellent migratory aptitude and resulted in corresponding N-acetoxymethyl-, N-alkoxymethyl-, and N-hydroxymethyl-N-arylimidazo[1,2-a]pyridine-3-amine derivatives in moderate to excellent (42 examples; 35–93%) yields. Radical trapping experiments confirmed the involvement of a non-radical intermediate. The developed protocol is amenable for a scale-up reaction, and synthetic utility of N-acetoxymethyl products was demonstrated by transforming them to corresponding N-(pyridin-2-yl)imidazo[1,2-a]pyridin-3-aminesItem Resin-Immobilized CuO and Cu Nanocomposites for Alcohol Oxidation(ACS, 2008-10-31) Pande, SurojitResin immobilized stable, spherical CuO nanoparticles prepared in the presence of cyclodextrin (CD) act as catalysts for liquid phase alcohol oxidation in air. The catalytic activity of the CuO nanocomposites and its green chemistry approach make it superior to the related resin-bound Cu(0) nanocomposite. The effect of alcohol chain length and electron-donating or -withdrawing groups influence product yield. The nanocomposites exhibit good reusability, simple workup procedure, and a straightforward approach to aldehyde formation.Item Resin-Immobilized CuO and Cu Nanocomposites for Alcohol Oxidation(ACS, 2008) Basu, Mrinmoyee; Pande, SurojitResin immobilized stable, spherical CuO nanoparticles prepared in the presence of cyclodextrin (CD) act as catalysts for liquid phase alcohol oxidation in air. The catalytic activity of the CuO nanocomposites and its green chemistry approach make it superior to the related resin-bound Cu(0) nanocomposite. The effect of alcohol chain length and electron-donating or -withdrawing groups influence product yield. The nanocomposites exhibit good reusability, simple workup procedure, and a straightforward approach to aldehyde formation.Item Thermodynamic and Kinetics Aspects of Spherical MnO2 Nanoparticle Synthesis in Isoamyl Alcohol: An Ex Situ Study of Particles to One-Dimensional Shape Transformation(ACS, 2010) Basu, MrinmoyeeThermodynamically stable and robust α-MnO2 nanowire has been obtained in gram quantity from low cost starting materials KMnO4 and isoamyl alcohol. Here KMnO4 acts as an oxidizing agent and eventually produces the corresponding acid which caps the spherical MnO2 particles. The MnO2 nanoparticle formation is monitored by UV−visible spectrophotometry, and the activation energy of the reaction is reported to be 44−49 kJ mol−1. The particles upon modified hydrothermolysis (MHT) reaction produce nanofibrils and the nanofrabrils finally evolved stable α-MnO2 nanowires by heat treatment. The spherical MnO2 nanoparticles under MHT conditions undergo oriented attachment and result in MnO2 nanofibrils, i.e., the shape transformation takes place from spherical MnO2 nanoparticles to nanofibrils. This has been documented in this study. The nanofibrils, being thermally unstable, upon heat treatment easily change to robust single-crystalline defect-free α-MnO2 nanowires with an exact angle of 90° between (200) and (002) crystal planes.Item Solvent effect on the optical property of uranyl acetylacetonate monohydrate(Elsiever, 2011-01) Basu, MrinmoyeeThe lability of the [UO2(acac)2H2O] complex has been exploited to decipher solvent composition of a medium. Successive blue shift of the π–π* band (λmax = 282 nm) is observed due to alcohol substitution of increasing chain length in place of water. This observation helps to quantify the chain lengths of normal alcohol. The result has been accounted theoretically. However, in non-coordinating solvent, irregular red shift of the π–π* band is observed because of the molecular complexity. Again, charge transfer (CT) band at 211 nm has been identified employing polar–polar and polar coordinating–non-coordinating solvent systems.Item α,5-Didehydro-3-picoline Diradicals from Skipped Azaenediynes: Computational and Trapping Studies of an Aza-Myers−Saito Cyclization(ACS, 2004-05) Kumar, DalipOn the basis of density functional calculations, the isomerization of skipped azaenediynes (C-alkynyl-N-propargylimines) to azaenyne allenes and subsequent rapid aza-Myers−Saito cyclization to α,5-didehydro-3-picoline were predicted. We prepared the N-propargylimine of 1-phenyl-3-tri(isopropyl)silylprop-2-yn-1-one, which undergoes proto-desilylation and isomerization to an azaenyne allene when treated with tetrabutylammonium fluoride. In the presence of 1,4-cyclohexadiene, this azaenyne allene affords 6-phenyl-3-picoline and other products corresponding to the trapping of an α,5-didehydro-3-picoline diradical.Item Anchored Pd Complex in MCM-41 and MCM-48: Novel Heterogeneous Catalysts for Hydrocarboxylation of Aryl Olefins and Alcohols(ACS, 2002) Sarkar, Bibhas R.We report here, for the first time, synthesis of anchored Pd complexes in mesoporous supports such as MCM-41 and MCM-48 as true heterogeneous catalysts for hydrocarboxylation of aryl olefins and alcohols to give excellent conversion (∼100%) and regioselectivity (∼99%) for 2-arylpropionic acids. The catalysts were characterized by powder-XRD, 31P CP-MAS NMR, FT-IR, TEM, XPS and ICP-AES. Recycle studies with these anchored Pd mesoporous catalysts were performed to confirm true heterogeneity.Item Trinuclear coordinatively labile Cu(ii) complex of 4,6-O-ethylidene-β-d-glucopyranosylamine derived Schiff baseligand and its reactivity towards primary alcohols and amines(RSC, 2005) Sah, Ajay KumarA novel neutral trinuclear Cu(II) complex of a Schiff base ligand derived from D-glucose has been synthesised and structurally characterised, which exhibits excellent alcohol binding affinity and activates the C–Cl bond of chloroform in the presence of primary amine.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 Selective Retention of Methanol over Ethanol by a Cyclen-Based Cryptand/Copper(II) Complex(ACS, 2013) Sah, Ajay KumarA cyclen-based cryptand (2) was prepared in a two-step synthesis from dioxocyclen. When a Cu(CF3SO3)2 complex with 2 was prepared in methanol, the 2/Cu(CF3SO3)2 complex incorporated one methanol in the cavity formed by the diethyleneoxy unit and the NH group of the cyclen. When prepared in ethanol, the 2/Cu(CF3SO3)2 complex similarly incorporated one ethanol. Cold electrospray ionization mass spectrometry (CSI-MS) of the 2/Cu(CF3SO3)2/alcohol complexes selectively retains methanol over ethanol under CSI-MS conditions.