North East Institute of Science and Technology

India

North East Institute of Science and Technology

India

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Borah B.J.,North East Institute of Science and Technology | Dutta D.,North East Institute of Science and Technology | Saikia P.P.,North East Institute of Science and Technology | Barua N.C.,North East Institute of Science and Technology | Dutta D.K.,North East Institute of Science and Technology
Green Chemistry | Year: 2011

In situ generation of Cu(0)-nanoparticles in the nanopores of modified montmorillonite and their catalytic activity in 1,3-dipolar cycloaddition reactions between azides and terminal alkynes to synthesise 1,2,3-triazoles have been carried out. The modification of montmorillonite was carried out by activation with H 2SO 4 under controlled conditions for generating nanopores to act as a "host" for the Cu(0)-nanoparticles, which is executed by successful loading of Cu(CH 3COO) 2 metal precursor through an incipient wetness impregnation technique followed by reduction with NaBH 4. A TEM study reveals that Cu(0)-nanoparticles within the size range of 0-10 nm are evenly distributed on the support. The synthesized Cu(0)-nanoparticles exhibit face centered cubic (fcc) lattice geometry and serve as an efficient green catalyst for the "Click" azide-alkyne cycloaddition to afford highly regioselective 1,4-disubstituted 1,2,3-triazoles with excellent yields and selectivity in aqueous medium. The nanocatalysts can be recycled and reused several times without significant loss of their catalytic activity. © 2011 The Royal Society of Chemistry.


Seetham Naidu P.,North East Institute of Science and Technology | Bhuyan P.J.,North East Institute of Science and Technology
Tetrahedron Letters | Year: 2012

Synthesis of some analogues of indole based marine alkaloid (±)gelliusine F, (±)gelliusine E, and total synthesis of 2,2-di(6′-bromo-3′-indolyl)ethylamine are reported. © 2011 Elsevier Ltd. All rights reserved.


Deb B.,North East Institute of Science and Technology | Sarmah P.P.,North East Institute of Science and Technology | Dutta D.K.,North East Institute of Science and Technology
European Journal of Inorganic Chemistry | Year: 2010

The reaction of P,S-chelating diphosphane ligands [bis(2-di- phenylphosphanylphenyl)ether monosulfide] (a) and [9,9-di-methyl-4,5- bis(diphenylphosphanyl)xanthene monosulfide] (b) with [Ru(CO)2Cl 2]n in a 1:1 molar ratio affords two new ruthenium(II) complexes of the type [Ru(CO)2Cl2(PnS)] (1a, 1b), where P∩S = a, b. The compounds are characterized by elemental analyses, mass spectrometry, thermal studies, and IR and NMR spectroscopy, together with single-crystal X-ray structure determination of bis(2-diphenylphosphanylphenyl) ether (DPEphos), a, 1a, and 1b. The ruthenium atom in both 1a and 1b occupies the center of a slightly distorted octahedral environment formed by a P atom, an S atom, two Cl atoms, and two CO groups. The crystal structures of a and la highlights an interesting feature, in which the P(2)-P(1)-S(1) spatial angle (ca. 174.7°) in free ligand a is reduced to around 46° upon complexation, which indicates a very high flexibility of the angle. Complex la also exhibits some hemilabile behavior in solution because of its flexible ligand back-bone, while ligand b in complex 1b remains rigid in solution. Complexes 1a and 1b are thermally stable up to about 300 °C and show high catalytic activities in the transfer hydrogenation of aldehydes and ketones to the corresponding alcohols. The highest conversion (about 99%) with the corresponding TOP value of about 1000 h-1 was obtained for 1a in the case of benzaldehyde. The catalytic efficiency of la is found to be much higher than 1b, which might result from the hemilabile behavior of ligand a. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA.


Majumder S.,North East Institute of Science and Technology | Bhuyan P.J.,North East Institute of Science and Technology
Tetrahedron Letters | Year: 2012

Some novel polycyclic thiopyrano[2,3-b]indole derivatives 7 were synthesized from simple oxindole 1 by exploring intramolecular domino hetero Diels-Alder reactions strategy. © 2011 Published by Elsevier Ltd.


Saikia K.,North East Institute of Science and Technology | Deb B.,North East Institute of Science and Technology | Dutta D.K.,North East Institute of Science and Technology
Journal of Molecular Catalysis A: Chemical | Year: 2014

New cationic carbonyl complexes of the type [M(CO)L]Cl (1) [M = Rh (a) and Ir (b); L = P(CH2CH2PPh2)3] have been synthesized and characterized by various spectroscopic techniques including the single crystal X-ray diffraction. Both the complexes crystallize in trigonal bipyramidal symmetry with the metal at the centre. Two strong intermolecular hydrogen bonds are observed in 1a. Despite the high trans effect of the CO group, the symmetrical tetradentate phosphine ligand bonded strongly to the metal centre through all sites and thereby expelling the Cl- ion outside the coordination sphere. The complexes are very stable and inert towards the oxidative addition (OA) of small molecules like CH3I, C2H5I and I2 at room as well as higher temperature. However, the complexes show catalytic activity towards the hydroformylation of alkene to the corresponding aldehydes under the reaction conditions: pressure 35 ± 2 bar, temperature 80 ± 2°C, 500 rpm and time 5-8 h. The yields of the aldehyde products are in the ranges 55-75%. The complexes exhibited dissociation of weaker MP bond under the above reaction conditions to form a vaccant coordination site for initiation of the catalytic cycle. © 2013 Elsevier B.V. All rights reserved.


Das A.M.,North East Institute of Science and Technology
Industrial and Engineering Chemistry Research | Year: 2011

A biodegradable protein fiber Antheraea assama silk (SH) was modified by using graft co-polymerization technique with methyl methacrylate (MMA; vinyl monomer) and cerric ammonium sulfate (CeIV). The grafting process was dependent on MMA, CeIV, time factors, temperatures and other properties of the fibroin composites. The possible mechanism of the SHMMA composite was explained by free radical co-polymerization, and the thermal properties were characterized by thermogravimetric analysis (TGA), differential thermogravimetry (DTG), differential thermal analysis (DTA), and differential scanning calorimetry (DSC). The kinetic parameters were also studied using the Coats and Redfern method with FORTRAN 77 computer programming and evaluating the activation energy. The structural changes of SHMMA, changes of the crystalline and amorphous characteristics after chemical process with MMA-CeIV initiator, were discussed in relation to the weight gain and X-ray diffraction curves. This study shows that silk fibroin composites modified by graft co-polymerization have improved thermal stability and chemical stability, which improve the drawbacks and make the silk fibroin a promising material in constructing textiles. © 2010 American Chemical Society.


Chaturvedi D.,North East Institute of Science and Technology | Goswami A.,North East Institute of Science and Technology | Pratim Saikia P.,North East Institute of Science and Technology | Barua N.C.,North East Institute of Science and Technology | Rao P.G.,North East Institute of Science and Technology
Chemical Society Reviews | Year: 2010

In this tutorial review, an effort towards presentation of a comprehensive account of the recent developments on various kinds of artemisinin derivatives including artemisinin dimers, trimers and tetramers has been made and their efficacy towards malaria parasites and different cancer cells lines was compared with that of artemisinins, and various other anti-malarial and anti-cancer drugs. It is expected that this review will provide first-hand information on artemisinin chemistry to organic/medicinal chemists, and pharmacologists working on anticancer and anti-malarial drug development. © 2010 The Royal Society of Chemistry.


Dutta D.K.,North East Institute of Science and Technology | Deb B.,North East Institute of Science and Technology
Coordination Chemistry Reviews | Year: 2011

This review reports several types of potential metals (rhodium and ruthenium) carbonyl complexes of functionalized phosphine-chalcogen donors ligands like: P-X (X = O, S, Se) and their catalytic applications particularly in (i) carbonylation of alcohols, (ii) hydrogenation of unsaturated substrates and (iii) hydroformylation of alkenes for industrially important organic molecules. © 2011 Elsevier B.V.


Majumder S.,North East Institute of Science and Technology | Bhuyan P.J.,North East Institute of Science and Technology
Synlett | Year: 2011

Functionalized annelated α-Carbolines have been synthesized from oxindole following a tertiary amino effect reaction strategy. © Georg Thieme Verlag Stuttgart New York.


Borah B.J.,North East Institute of Science and Technology | Dutta D.,North East Institute of Science and Technology | Dutta D.K.,North East Institute of Science and Technology
Applied Clay Science | Year: 2010

Auo-nanoparticles of 0-10nm were generated in situ by the reduction of [AuCl4]- impregnated on acid-activated montmorillonites with maximum pore diameters of about 3, 4, 6, and 8nm. The size of the Auo-nanoparticles depended on the pore diameter of the micro- and mesopores of the support. The montmorillonite was activated with HCl under control conditions for generating different pore sizes. Powder X-ray diffraction (XRD), FTIR, FESEM-EDX, HRTEM, N2 adsorption, 29Si and 27Al MAS-NMR and UV-visible spectroscopic analyses were carried out to characterize the solid porous materials before and after Auo-nanoparticle loading. N2 adsorption data revealed specific surface areas (BET) of 327-579m2/g, large specific pore volumes of ~0.7cm3/g, and pore diameters of 0-10nm. TEM, FESEM and X-ray mapping images revealed Auo-nanoparticles of 0-10nm evenly distributed on the support. The Auo-nanocrystal composites exhibited the cubic face-centered (fcc) lattice with a preferential growth direction along the (111) plane. © 2010 Elsevier B.V.

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