- Heterogeneous Catalytic Oxidative Bromination and Oxidation of Thioethers By Vanadium(IV) Oxido Complex of Benzoylacetone and Effect of Solid Supports
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Vanadium(IV) oxido complex of 1-Phenyl-1,3-butanedione [VIVO(bzac)2] (1) was prepared, characterized, and heterogenized onto APTMS modified graphene oxide, as well as imidazole modified polystyrene beads. Graphene oxide supported complex GO-APTMS-[VIVO(bzac)2] (2) and polymer anchored complex PS-im-[VIVO(bzac)2] (3) were used for the oxidative bromination of a number of small organic molecules and oxidation of a series of thioethers. Both 2 and 3 evolve as excellent heterogeneous catalysts. The nature of solid support does not impact substrate conversion (%) during the oxidative bromination of salicylaldehyde, phenol, or styrene, whereas it influences the substrate conversion (%) as well as the product selectivity (%) during the oxidation of thioethers. Graphic Abstract: [Figure not available: see fulltext.]
- Kesharwani, Neha,Chaudhary, Nikita,Haldar, Chanchal
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p. 3562 - 3581
(2021/03/24)
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- Oxidovanadium (V and IV) complexes incorporating coumarin based O^N^O ligand: Synthesis, structure and catalytic activities
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The tridentate ligand H2L1, [(E)-7-Hydroxy-8-[(2-hydroxy-phenylimino)-methyl]-4-methyl-chromen-2-one] has been used in the present work towards the synthesis of mononuclear oxidovanadium complexes. Three mononuclear complexes [VOL1(OMe)(MeOH)], 1; [VO(L1)(8-Hq)], 2 and [VO(L1)(1,10-phen)], 3 have been successfully synthesized with high yields by reacting [VO(acac)2] with H2L1 in 1:1 ratio in methanol under refluxing conditions where 8-hydroxyquinoline and 1,10-phenanthroline were used as co-ligands in the synthesis of complex 2 and 3. X-ray crystallographic studies reveal that in all the complexes synthesized in the present study, the ligand H2L1 binds as O^N^O coordinating ligand. The synthesized complexes were well characterized by using UV–Vis, IR, NMR and Mass spectral techniques. The physiochemical properties have been well interpreted by density functional theory (DFT) and time dependent density functional theory (TDDFT) calculations. The synthesized complexes were established to show some distinctive properties e.g. oxidative bromination of aromatic aldehyde with high conversion rate and enhanced selectivity as well as high TON and TOF. The above properties were all well matched and demonstrated by using UV–visible and fluorescence as well as quenching studies. Complex 1 reacts with 3,5-DTBC catalytically in presence of molecular oxygen to generate corresponding ortho-benzoquinone.
- Majumder, Mitali,Krishna Rajak, Kajal
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- Synthesis and characterization of dimeric μ-oxidovanadium complexes as the functional model of vanadium bromoperoxidase
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Two vanadium (IV) complexes [VIVO(Haeae-sal)(MeOH)]+ (1) and [VIVO(Haeae-hyap)(MeOH)]+ (2) were prepared by reacting [VO(acac)2] with ligands [H2aeae-sal] (I) and [H2aeae-hyap] (II) respectively. Condensation of 2-(2-aminoethylamino)ethanol with salicylaldehyde and 2-hydroxyacetophenone produces the ligands (I) and (II) respectively. Both vanadium complexes 1 and 2 are sensitive towards aerial oxygen in solution and rapidly convert into vanadium(V) dioxido species. Vanadium(V) dioxido species crystalizes as the dimeric form in the solid-state. Single-crystal XRD analysis suggests octahedral geometry around each vanadium center in the solid-state. To access the benefits of heterogeneous catalysis, vanadium(V) dioxido complexes were anchored into the polymeric chain of chloromethylated polystyrene. All the synthesized neat and supported vanadium complexes have been studied by a number of techniques to confirm their structural and functional properties. Bromoperoxidase activity of the synthesized vanadium(V) dioxido complexes 3 and 4 was examined by carrying out oxidative bromination of salicylaldehyde and oxidation of thioanisole. In the presence of hydrogen peroxide, 3 shows 94.4% conversion (TOF value of 2.739 × 102 h?1) and 4 exhibits 79.0% conversion (TOF value of 2.403 × 102 h?1) for the oxidative bromination of salicylaldehyde where 5-bromosalicylaldehyde appears as the major product. Catalysts 3 and 4 also efficiently catalyze the oxidation of thioanisole in the presence of hydrogen peroxide where sulfoxide is observed as the major product. Covalent attachment of neat catalysts 3 and 4 into the polymer chain enhances substrate conversion (%) and their catalytic efficiency increases many folds, both in the oxidative bromination and oxidation of thioether. Polymer supported catalysts 5 displayed 98.8% conversion with a TOF value of 1.127 × 104 h?1 whereas catalyst 6 showed 95.7% conversion with a TOF value of 4.675 × 103 h?1 for the oxidative bromination of salicylaldehyde. These TOF values are the highest among the supported vanadium catalysts available in the literature for the oxidative bromination of salicylaldehyde.
- Chaudhary, Nikita,Haldar, Chanchal,Kachhap, Payal,Kesharwani, Neha,Mahato, Arun Kumar,Maurya, Abhishek,Mishra, Vivek Kumar
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- Peroxo–tungstate(VI) complexes: syntheses, characterization, reactivity, and DFT studies
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Abstract: Three new oxodiperoxo–tungsten(VI) complexes containing benzene core carboxylic acids, viz., benzoic acid, 2-chlorobenzoic acid, and 3-aminobenzoic acid as co-ligands have been synthesized from reaction of Na2WO6H4, 30% H2O2 and the corresponding co-ligands in aqueous medium. The compounds have been comprehensively characterized by elemental analyses, FT-IR, 1H NMR, UV–Vis spectral studies as well as by mass spectrometric and TGA analyses. The infrared spectra suggest occurrence of terminally bonded W=O as well as triangular bidentate peroxo groups (C2v) and monodentate carboxylate group bound to the WO4+ center. The mass spectra of the compounds are in good agreement with proposed molecular formulations. Thermogravimetric analyses indicate the existence of both lattice and coordinated water molecules in the complexes. Density functional theory (DFT) calculations were used to compute the frequencies of relevant vibrational modes, electronic properties and also to investigate structure of the compounds. Compound potassium(aquo)(2-chlorobenzoato)oxodiperoxo–tungstate(VI)dihydrate acts as an oxidant for bromide ion in aqueous phase bromination of chosen organic substrates to their corresponding bromo-organics. Graphical abstract: [Figure not available: see fulltext.]
- Das, Nandita,Chowdhury, Shubhamoy,Purkayastha, Ranendra N. Dutta
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p. 1255 - 1266
(2019/07/04)
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- Mono- and dinuclear oxidovanadium(v) complexes of an amine-bis(phenolate) ligand with bromo-peroxidase activities: Synthesis, characterization, catalytic, kinetic and computational studies
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The mono- and dinuclear oxidovanadium(v) complexes [VVO(L1)(Cl)] (1) and [L1VVO(μ2-O)VO(L1)] (2) of ONNO donor amine-bis(phenolate) ligand (H2L1) were readily synthesized by the reaction between H2L1 and VCl3.(THF)3 or VO(acac)2 in MeOH or MeCN, respectively, and then characterized through mass spectroscopy, 1H-NMR and FTIR techniques. Both the complexes possess distorted octahedral geometry around each V centre. Upon the addition of 1 equivalent or more acid to a MeCN solution of complex 1, it immediately turned into the protonated form, which might be in equilibrium as: [L1ClVVOH]+ ? [L1ClVV-OH]+ (in the case of [L1ClVVOH]+ oxo-O is just protonated, whereas in [L1ClVV-OH]+ it is a hydroxo species), with the shift in λmax from 610 nm to 765 nm. Similar was the case for complex 2. The complexes 1 and 2 could efficiently catalyze the oxidative bromination of salicylaldehyde in the presence of H2O2 to produce 5-bromo salicylaldehyde as the major product with TONs of 405 and 450, respectively, in the mixed solvent system (H2O:MeOH:THF = 4:3:2, v/v). The kinetic analysis of the bromide oxidation reaction indicated a first-order mechanism in the protonated peroxidovanadium complex and a bromide ion and limiting first-order mechanism on [H+]. The evaluated kBr and kH values were 5.78 ± 0.20 and 11.01 ± 0.50 M-1 s-1 for complex 1 and 6.21 ± 0.13 and 20.14 ± 0.72 M-1 s-1 for complex 2, respectively. The kinetic and thermodynamic acidities of the protonated oxido species of complexes 1 and 2 were pKa = 2.55 (2.35) and 2.16 (2.19), respectively, which were far more acidic than those reported by Pecoraro et al. for peroxido-protonation instead of oxido protonation. On the basis of the chemistry observed for these model compounds, a mechanism of halide oxidation and a detailed catalytic cycle are proposed for the vanadium haloperoxidase enzyme and these were substantiated by detailed DFT calculations.
- Debnath, Mainak,Dolai, Malay,Pal, Kaberi,Bhunya, Sourav,Paul, Ankan,Lee, Hon Man,Ali, Mahammad
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supporting information
p. 2799 - 2809
(2018/02/28)
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- Two dinuclear oxidovanadium(V) complexes of N2O2 donor amine-bis(phenolate) ligands with bromo-peroxidase activities: Kinetic, catalytic and computational studies
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Two dinuclear oxidovanadium(V) complexes [LiVVO(μ2-O)VVO(Li)] (i = 1, H2L1, complex 1 and i = 2 for H2L2, complex 2) of two ONNO donor amine-bis(phenolate) ligands have been synthesized and characterized by X-ray diffraction studies which exhibited distorted octahedral geometry around each V center. In MeCN the complexes exist as dimers as indicated by HRMS studies, however, in the presence of 2 or more equivalents of H+ the dimers turned into monomers, ([LiVV = O]+ which exists in equilibrium with ([LiVV = OH]2+ and evidenced from the shift in λmax from 685 nm to 765 nm for complex 1 and 600 to 765 nm for complex 2. The complexes 1 and 2 efficiently catalyze the oxidative bromination of salicylaldehyde in the presence of H2O2 to produce 5-bromo-salicylaldehyde as the major product with TONs 405 and 450, respectively in the mixed solvent system (H2O:MeOH:THF = 4:3:2, v/v). The kinetic analysis of the bromide ion oxidation reaction indicates a mechanism which is first order in peroxidovanadium complex and bromide ion and limiting first-order on [H+]. The evaluated kBr and kH values are (8.82 ± 0.35) and (65.0 ± 2.23) M?1 s?1 for complex 1 and (6.74 ± 0.19) and (61.87 ± 2.27) M?1 s?1 for complex 2, respectively. The Ka of protonated species ([LiVV = OH]2+ are: Ka = (4.3 ± 0.40) × 10?3 (pKa = 2.37) and (4.7 ± 0.50) × 10?3 (pKa = 2.33) for complex 1 and 2 respectively. On the basis of the chemistry displayed by these model compounds, a mechanism of bromide oxidation and a tentative catalytic cycle have been framed which might be relevant to vanadium haloperoxidase enzymes and supported by DFT calculations.
- Debnath, Mainak,Dolai, Malay,Pal, Kaberi,Dutta, Arpan,Lee, Hon Man,Ali, Mahammad
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p. 149 - 158
(2018/05/28)
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- Polymer-anchored [Fe(III)Azo] complex: An efficient reusable catalyst for oxidative bromination and multi-components reaction for the synthesis of spiropiperidine derivatives
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A heterogeneous catalyst was prepared by attaching Fe(III) into organically modified chloromethylated polytstyrene and characterized by AAS, IR, PXRD, TG-DTA, UV–Vis, and SEM studies. In presence of H2O2 and KBr as bromine source, the catalyst showed remarkably high conversion with para-selectivity towards the oxidative bromination reaction in acetic acid medium. The catalyst was also very active and highly efficient for the production of spiropiperidine derivatives through multi-component reaction in isopropyl alcohol at room temperature. The catalyst was not leached during the catalytic reactions, moreover, after five cycles the catalytic activity and selectivity of the catalyst were not decreased very significantly.
- Khatun, Resmin,Biswas, Surajit,Ghosh, Swarbhanu,Islam, Sk. Manirul
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- Dioxidomolybdenum(VI) complexes bearing sterically constrained aroylazine ligands: Synthesis, structural investigation and catalytic evaluation
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Seven new dioxidomolybdenum(VI) complexes [MoO2L1(X)].X (1) and [MoO2L2–7(X)] (2–7) [Where X = EtOH in case of 1 and 5 and X = DMSO in case of 2–4 and 6, 7] of aroylazines containing a bulky 3-hydroxy-2-naphthoic substituent, were isolated and structurally characterized. The aroylazine ligands H2L1–7 were derived from the condensation of 3-hydroxy-2-naphthoic acid hydrazide with several substituted aromatic aldehydes/ketones. All the synthesized ligands and metal complexes were successfully characterized by elemental analysis, IR, UV–Vis and NMR spectroscopy. X-ray structures of 1–6 revealed that the ligands coordinate to the metal center as a dibasic tridentate ligand. Cyclic voltammetry of the complexes shows two irreversible reductive responses within the potential window ?0.50 to ?1.36 V, due to MoVI/MoV and MoV/MoIV processes. The synthesized complexes 1–7 were used as catalysts for the oxidation of benzoin, and for the oxidative bromination of salicylaldehyde, as a functional mimic of haloperoxidase. It was found that the percentage of conversion increased significantly in the presence of catalysts 1–7 which contained bulky substituents, and showed high percentage of conversion (>90%) with high turnover frequency (>1100 h?1) than previously reported catalysts. Benzil, benzoic acid and benzaldehyde-dimethylacetal were formed selectively for the oxidation of benzoin. Formation of 5-bromosalicylaldehyde and 3,5-dibromosalicylaldehyde took place during the oxidative bromination of salicylaldehyde in presence of H2O2 as an oxidant and therefore 1–7 act as functional models of vanadium dependent haloperoxidases.
- Majumder, Sudarshana,Pasayat, Sagarika,Roy, Satabdi,Dash, Subhashree P.,Dhaka, Sarita,Maurya, Mannar R.,Reichelt, Martin,Reuter, Hans,Brzezinski, Krzysztof,Dinda, Rupam
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p. 366 - 378
(2017/10/06)
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- Graphene Oxide Promoted Oxidative Bromination of Anilines and Phenols in Water
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The mildly acidic and oxidative nature of graphene oxide, with its large surface area available for catalytic activity, has been explored in aromatic nuclear bromination chemistry for the first time. The versatile catalytic activity of graphene oxide (GO) has been used to selectively and rapidly brominate anilines and phenols in water. The best results were obtained at ambient temperatures using molecular bromine in a protocol promoted by oxidative bromination catalyzed by GO; these transformations proceeded with 100% atom economy with respect to bromine and high selectivities for the tribromoanilines and -phenols. Reduced graphene oxide (r-GO) was observed to form after the second recycle (third use) of GO. This technique is also effective with N-bromosuccinimide (NBS) as the brominating reagent. In the case of NBS, reactions were instantaneous and the GO displayed excellent recyclability without any loss of activity over several cycles.
- Ghorpade, Prashant Vasantrao,Pethsangave, Dattatray Appasha,Some, Surajit,Shankarling, Ganapati Subray
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p. 7388 - 7397
(2018/07/29)
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- A regenerable zinc(II) coordination polymer as a dual-luminescent sensor for detection of Cr2O72– and 2,4,6-trinitrophenol in aqueous phase
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Developing a fast and sensitive method for the detection of 2,4,6-trinitrophenol (TNP) or Cr2O72– in aqueous solution has received great attention. In this work, a regenerable fluorescent coordination polymer [Zn(L)(H
- Wu, Yu,Huang, Yun,Wang, Yulan,Zou, Xiang,Wang, Jun,Wu, Weiping
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p. 3994 - 4006
(2018/12/11)
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- Syntheses and characterization of monobasic tridentate Cu(II) Schiff-base complexes for efficient oxidation of 3,5-di-: tert -butylcatechol and oxidative bromination of organic substrates
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Two monomeric copper complexes [CuII(sal-ppzH)Cl2] (1) and [CuII(hyap-ppzH)Cl2] (2) were synthesized by reacting CuCl2·2H2O with the monobasic tridentate Schiff-base ligands [Hsal-ppz] (I) and [Hyap-ppz] (II) (derived by reacting 1-(2-aminoethyl) piperazine with salicylaldehyde and 2-hydroxyacetophenone) respectively. Elemental analysis, IR, UV-Vis, 1H NMR and 13C NMR data confirm the structures of the ligands and those of the complexes. Both complexes are monomeric in nature in the solid state and in solution as well. Single crystal XRD data suggest a distorted square pyramidal geometry for 1 crystallized in the P1 space group. DFT studies established a similar molecular structure for 2. The synthesized metal complexes [CuII(sal-ppzH)Cl2] (1) and [CuII(hyap-ppzH)Cl2] (2) successfully catalyzed the oxidation of 3,5-di-tert-butylcatechol (3,5-DTBC) in methanol in the presence of H2O2 with high Kcat values of 1.182 × 104 mmol h-1 and 2.880 × 104 mmol h-1, respectively. [CuII(sal-ppzH)Cl2] (1) and [CuII(hyap-ppzH)Cl2] (2) were also anchored into the polymeric matrix of chloromethylated polystyrene and were analyzed by TGA, atomic absorption spectroscopy (AAS), EPR, scanning electron microscopy (SEM) as well as energy dispersive X-ray (EDX) analysis. The polymer grafted metal complexes were used as catalyst precursors in the oxidative bromination of salicylaldehyde in the presence of H2O2, KBr and HClO4. Under optimized reaction conditions, both catalysts show nearly quantitative oxidative bromination of salicylaldehyde, with the order of % products formed being 5-bromosalicylaldehyde > 3,5-dibromosalicylaldehyde > 3-bromosalicylaldehyde. Plausible reactive species involved in the catalytic cycle are identified by UV-Vis spectroscopy, pH metric titration, ESI-MS, EPR and DFT studies.
- Kumari, Sweta,Mahato, Arun Kumar,Maurya, Abhishek,Singh, Vijay Kumar,Kesharwani, Neha,Kachhap, Payal,Koshevoy, Igor O.,Haldar, Chanchal
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p. 13625 - 13646
(2017/11/27)
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- Cis-Dioxomolybdenum(VI) complexes with unsymmetric linear tetradentate ligands: Syntheses, structures and bromoperoxidase activities
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Reactions of [MoO2(acetylacetonate)2], 2-((2-(2-hydroxyethylamino)ethylamino)methyl)-4-R-phenols (H2Ln, n = 1-5 for R = H, Me, OMe, Cl and Br, respectively) and KOH in 1:1:2 mole ratio in methanol afford a series of complexes having the general formula cis-[MoO2(Ln)] (1, 2, 3, 4, 5) in 81-86% yields. The complexes have been characterized using elemental analysis, spectroscopy (infrared, UV-visible, and 1H NMR, 13C NMR and 13C-DEPT NMR) and electrochemical measurements. The molecular structures of 1, 2, 3, 4 have been determined using single-crystal X-ray crystallography. In each of 1, 2, 3, 4, the ONNO-donor 6,5,5-membered fused chelate rings forming (Ln)2- and the two mutually cis oxo groups assemble a distorted octahedral N2O4 coordination sphere around the metal centre. In the crystal lattice, each of 1, 2, 3, 4 forms a one-dimensional infinite chain structure via intermolecular N-H...O hydrogen bonding interactions. In cyclic voltammograms, the diamagnetic complexes display an irreversible metal-centred reduction in the potential range -0.73 to -0.88 V (vs Ag/AgCl). The physicochemical data are consistent with a very similar gross molecular structure for all of 1, 2, 3, 4, 5. All the complexes exhibit decent bromoperoxidase activities and are also able to effectively catalyse benzoin and methyl(phenyl)sulfide oxidation reactions.
- Kurapati, Sathish Kumar,Pal, Samudranil
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p. 116 - 124
(2016/02/18)
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- Novel dyes of branched chain polymeric metal complexes based on cyclopentadithiophene derivatives: synthesis, characterization and photovoltaic performance for dye-sensitized solar cells
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Abstract: In this work, four novel D–A polymeric metal complexes (P1–P4) were designed and synthesized as dye sensitizers for high-performance dye-sensitized solar cells (DSSCs), which use cyclopentadithiophene or fluorene derivatives as donor (D) and the
- Liu, Ye,Xie, Qiufang,Liao, Yanlong,Zhu, Chunxiao,Chen, Xu,Chen, Tianqi,Zhong, Chaofan
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p. 6163 - 6179
(2016/06/01)
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- Complexes of cis-dioxomolybdenum(VI) with unsymmetrical tripodal NO3-donor ligands: Synthesis, characterization and catalytic applications
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A series of cis-dioxomolybdenum(VI) complexes of general formula cis-[MoO2(HLn)] (1-4) have been synthesized in 80-85% yields by reacting equimolar amounts of [MoO2(acac)2] (acac- = acetylacetonate) with 2,2′-(2-hydroxy-3,5-R1,R2-benzylazanediyl)diethanols (H3Ln, n = 1-4) in methanol. Characterization of the complexes has been performed by elemental analysis, spectroscopic (IR, UV-Vis, 1H and 13C NMR) and electrochemical measurements. The molecular structures of all four complexes have been determined by single-crystal X-ray diffraction studies. In each of these analogous complexes, the metal centre is in a distorted octahedral NO5 coordination sphere assembled by the single edge shared 5,5,6-membered chelate rings forming NO3-donor (HLn)2- and two cis oriented oxo groups. Crystal structures of the complexes reveal formation of discrete centrosymmetric dimeric species via a pair of reciprocal intermolecular O-HO hydrogen bonding interactions. Spectroscopic data of all the complexes are consistent with their molecular structures. In the cyclic voltammograms, the redox-active complexes display a quasi-reversible to irreversible metal centred reduction with the cathodic peak potential in the range -0.92 to -1.12 V (versus Ag/AgCl). All the complexes have been evaluated for their catalytic activities in oxidative bromination reactions of styrene and salicylaldehyde and in benzoin oxidation reaction.
- Kurapati, Sathish Kumar,Maloth, Swamy,Pal, Samudranil
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- Synthesis, structural studies and catalytic activity of dioxidomolybdenum(VI) complexes with aroylhydrazones of naphthol-derivative
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Reaction of the salicylhydrazone of 2-hydroxy-1-naphthaldehyde (H 2L1), anthranylhydrazone of 2-hydroxy-1-naphthaldehyde (H2L2), benzoylhydrazone of 2-hydroxy-1-acetonaphthone (H2L3) and anthranylhydrazone of 2-hydroxy-1- acetonaphthone (H2L4; general abbreviation H2L) with [MoO2(acac)2] afforded a series of 5- and 6- coordinate Mo(VI) complexes of the type [MoO2L1-2(ROH)] [where R = C2H5 (1) and CH3 (2)], and [MoO 2L3-4] (3 and 4). The substrate binding capacity of 1 has been demonstrated by the formation of one mononuclear mixed-ligand dioxidomolybdenum complex [MoO2L1(Q)] {where Q = γ-picoline (1a)}. Molecular structure of all the complexes (1, 1a, 2, 3 and 4) is determined by X-ray crystallography, demonstrating the dibasic tridentate behavior of ligands. All the complexes show two irreversible reductive responses within the potential window -0.73 to -1.08 V, due to Mo VI/MoV and MoV/MoIV processes. Catalytic potential of these complexes was tested for the oxidation of benzoin using 30% aqueous H2O2 as an oxidant in methanol. At least four reaction products, benzoic acid, benzaldehyde-dimethylacetal, methyl benzoate and benzil were obtained with the 95-99% conversion under optimized reaction conditions. Oxidative bromination of salicylaldehyde, a functional mimic of haloperoxidases, in aqueous H2O2/KBr in the presence of HClO4 at room temperature has also been carried out successfully.
- Pasayat, Sagarika,Dash, Subhashree P.,Roy, Satabdi,Dinda, Rupam,Dhaka, Sarita,Maurya, Mannar R.,Kaminsky, Werner,Patil, Yogesh P.,Nethaji
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- Polymer-grafted and neat vanadium(V) complexes as functional mimics of haloperoxidases
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The monobasic tridentate ONN donor ligand 1-(2-pyridylazo)-2-naphthol [Hpan (I)] reacts with [VIVO(acac)2] in dry methanol to yield the oxidovanadium(IV) complex [VIVO(acac)(pan)] (1). The dioxidovanadium(V) complex [{VVO(pan)}2(μ-O) 2] (2) is obtained by aerial oxidation of 1 in methanol. Complex 2 can also be prepared directly by reacting [VIVO(acac)2] with I followed by aerial oxidation in methanol. Treatment of 1 or 2 in methanol with H2O2 yields the oxidomonoperoxidovanadium(V) complex [VVO(O2)(pan)(MeOH)] (3). Reaction of imidazolomethylpolystyrene cross-linked with 5% divinylbenzene (PS-im) with 2 in DMF resulted in the formation of the polymer-grafted dioxidovanadium(V) complex PS-im[VVO2(pan)] (4). All these complexes are characterized by various spectroscopic techniques (IR, electronic, NMR ( 1H and 51V) and electron paramagnetic resonance (EPR)), thermal, field-emission scanning electron micrographs (FE-SEM) as well as energy dispersive X-ray (EDX) studies. The crystal and molecular structure of 3 has been determined, confirming the ONN binding mode of I. The polymer-grafted complex 4 has been used for the oxidative bromination of styrene, salicylaldehyde and trans-stilbene. Various parameters, such as amounts of catalyst, oxidant (aqueous 30% H2O2), KBr and aqueous 70% HClO4 have been optimized to obtain the maximum oxidative bromination of the substrates. Under the optimized reaction conditions, styrene gave a maximum of 99% conversion after 2 h of reaction, with the main products having a selectivity order of: 1-phenylethane-1,2-diol (75%) > 2-bromo-1- phenylethane-1-ol (20%) > 1,2-dibromo-1-phenylethane (1.2%). With nearly same conversion in same time, the oxidative bromination of salicylaldehyde gave three products with the selectivity order: 5-bromosalicylaldehyde > 2,4,6-tribromophenol > 3,5-dibromosalicylaldehyde. A maximum of 91% conversion of trans-stilbene has been obtained in 2 h of reaction time, where selectivity of the obtained reaction products varied in the order: 2,3-diphenyloxirane (trans-stilbene oxide) > 1,2-dibromo-1,2-diphenylethane > 2-bromo-1,2-diphenylethanol. The catalytic activity of the non-polymer grafted complex 2 is lower than that of the polymer-grafted one. In addition, the recycling ability of the grafted complex makes it better over the neat complex.
- Maurya, Mannar R.,Chaudhary, Nikita,Avecilla, Fernando
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p. 436 - 448
(2013/11/19)
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- Cu(OAc)2·H2O-promoted tandem β-alkynyl elimination of α-or β-hydroxy propargylic alcohols and homocoupling of the resulting alkynyl species
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α or β-hydroxy propargylic alcohols undergo tandem C(sp)-C(sp3) bond cleavage via β-alkynyl elimination and homocoupling of the resulted alkynyl species in the presence of Cu(OAc)2·H2O to produce the corresponding hydroxycarbonyl com
- Xu, Xiangsheng,Huang, Zhenyong,Lu, Yanfeng
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p. 546 - 549
(2013/10/22)
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- Cu-Mn spinel oxide catalyzed regioselective halogenation of phenols and N-heteroarenes
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A novel simple, mild chemo- and regioselective method has been developed for the halogenation of phenols using Cu-Mn spinel oxide as a catalyst and N-halosuccinimide as halogenating agent. In the presence of Cu-Mn spinel oxide B, both electron-withdrawing and electron-donating groups bearing phenols gave monohalogenated products in good to excellent yields with highest para-selectivity. The para-substituted phenol gave monohalogenated product with good yield and ortho-selectivity. N-Heteroarenes such as indoles and imidazoles also gave monohalogenated products with high selectivity. Unlike the copper-catalyzed halogenation, the present method works well with electron-withdrawing group bearing phenols and gives comparatively better yields and selectivity. The Cu-Mn spinel catalyst is robust and reused three times under optimized conditions without any loss in catalytic activity. Nonphenolics did not undergo this transformation.
- Singh, Parvinder Pal,Thatikonda, Thanusha,Kumar, K. A. Aravinda,Sawant, Sanghapal D.,Singh, Baldev,Sharma, Amit Kumar,Sharma,Singh, Deepika,Vishwakarma, Ram A.
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scheme or table
p. 5823 - 5828
(2012/09/05)
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- Synthesis, characterization, catalytic and antiamoebic activity of vanadium complexes of binucleating bis(dibasic tridentate ONS donor) ligand systems
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[VIVO(acac)2] (acac = acetylacetonate) was treated with ligands CH2(H2L)2 in methanol heated at reflux to yield two neutral binuclear VIV complexes with the formula [CH2{VIVOL(H2O)}2], namely, 1 and 2. Ligands CH2(H2L)2 I and II were derived from 5,5'-methylenebis(salicylaldehyde) and S-benzyldithiocarbazate [CH 2(H2sal-sbdt)2, I] or S-methyldithiocarbazate [CH2(H2sal-smdt)2, II]. Aerial oxidation of 1 and 2 in the presence of KOH or CsOH·H2O resulted in the formation of dioxidovanadium(V) complexes, K2[CH2{V VO2(sal-sbdt)}2]·2H2O (3), Cs2[CH2{VVO2(sal-sbdt)} 2]·2H2O (4), K2[CH2{V VO2(sal-smdt)}2]·2H2O (5) and Cs2[CH2{VVO2(sal-smdt)} 2]·2H2O (6). The compounds were characterized in the solid state and in solution, namely, by spectroscopic techniques (IR, UV/Vis, EPR, 1H, 13C and 51V NMR spectroscopy). It is demonstrated that the VVO2 complexes 3-6 are efficient and selective towards the oxidative bromination by H2O 2 of styrene to yield 1,2-dibromo-1-phenylethane, 1-phenylethane-1,2-diol and 2-bromo-1-phenylethane-1-ol, and of salicylaldehyde to yield 5-bromosalicylaldehyde, 3,5-dibromosalicylaldehyde and 2,4,6-tribromophenol; they therefore act as functional models of vanadium-dependent haloperoxidases. It is also shown that Cs2[CH 2{VVO2(sal-sbdt)}2]·2H 2O (4) and Cs2[CH2{VVO 2(sal-smdt)}2]·2H2O (6) are catalyst precursors for the catalytic oxidation of styrene by peroxide to yield styrene oxide, benzaldehyde, 1-phenylethane-1,2-diol, benzoic acid and phenylacetaldehyde. Plausible intermediates involved in these catalytic processes were established by UV/Vis, EPR and 51V NMR spectroscopic studies. The VVO2 complexes along with ligands I and II were also screened against HM1:1MSS strains of Entamoeba histolytica; the IC50 values of compounds 3, 4 and 5 were significantly lower than that of metronidazole, thereby suggesting that they may be promising drugs for the treatment of amoebiasis. Copyright
- Maurya, Mannar R.,Haldar, Chanchal,Khan, Aftab Alam,Azam, Amir,Salahuddin, Attar,Kumar, Amit,Costa Pessoa, Joao
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experimental part
p. 2560 - 2577
(2012/08/14)
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- Selective oxidation of sulfides and oxidative bromination of organic substrates catalyzed by polymer anchored Cu(II) complex
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A new polymer-anchored Cu(II) complex has been synthesized and characterized. The catalytic performance of the complex has been tested for the oxidation of sulfides and in oxidative bromination reaction with hydrogen peroxide as the oxidant. Sulfides have been selectively oxidized to the corresponding sulfoxides in excellent yields and in the presence of KBr as the bromine source, organic substrates have been selectively converted to mono bromo substituted compounds using polymer-anchored Cu(II) catalyst. This catalyst showed excellent catalytic activity, high selectivity, and recyclability. The polymer-anchored Cu(II) catalyst could be easily recovered by filtration and reused more than five times without appreciable loss of its initial activity.
- Islam,Roy, Anupam Singha,Mondal, Paramita,Tuhina, Kazi,Mobarak, Manir,Mondal, John
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scheme or table
p. 127 - 131
(2012/01/17)
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- Structural models of vanadate-dependent haloperoxidases, their reactivity, immobilization on polymer support and catalytic activities
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The design of structural and functional models of enzymes vanadate-dependent haloperoxidases (VHPO) and the isolation and/or generation of species having {VO(H2O)}, {VO2}, {VO(OH)} and {VO(O 2)} cores, proposed as intermediate(s) during catalytic action, in solution have been studied. Catalytic potential of these complexes have been tested for oxo-transfer as well as oxidative bromination and sulfide oxidation reactions. Some of the oxidovanadium(IV) and dioxidovanadium(V) complexes have been immobilized on polymer support in order to improve their recycle ability during catalytic activities and turn over number. The formulations of the polymer-anchored complexes are based on the respective neat complexes and conclusions drawn from the various characterization studies. These catalysts have successfully been used for all catalytic reactions mentioned above. These catalysts are stable and recyclable. Indian Academy of Sciences.
- Maurya, Mannar R.
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experimental part
p. 215 - 228
(2012/03/12)
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- An instant and facile bromination of industrially-important aromatic compounds in water using recyclable CaBr2-Br2 system
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Various industrially-important brominated intermediates have been instantly synthesized using aq. CaBr2-Br2 system as an efficient and recyclable brominating reagent under aqueous conditions at room temperature without the need for metal catalysts or acidic additives. Structurally-diverse phenol and aniline derivatives with strong electron-withdrawing groups such as carboxylic, nitro and formyl show remarkable reactivity to the brominating reagent and brominated in 92-98% yield with high purity (>99%) in a very short reaction time. Organic solvent-free conditions, a feature of the green chemistry, were successively used not only for the reactions but also for the isolation of products at the end of the reaction. The recycling of HBr by its neutralization, thereby generating additional amounts of industrially-important CaBr2 has been designed and developed. The brominating reagent has been recycled and regenerated, and the process was repeated up to 4 cycles after the fresh batch using the regenerated brominating reagent having almost identical selectivity and isolated yields, which seems to be the most promising methodology from the viewpoint of the green approach to organic synthesis.
- Kumar, Lalit,Mahajan, Tanu,Agarwal
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experimental part
p. 2187 - 2196
(2011/09/16)
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- An efficient regioselective NBS aromatic bromination in the presence of an ionic liquid
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A simple, efficient, and rapid method was developed for high-yielding regioselective monobromination of activated aromatic compounds using NBS in combination with ionic liquid 1-butyl-1-methylimidazolium bromide ([Bmim]Br) or dioxane. The ionic liquid is recyclable and can be reused with minimal loss in the catalytic efficiency if the ionic liquid is rapidly microwaved prior to reactions.
- Pingali, Subramanya R.K.,Madhav, Monika,Jursic, Branko S.
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experimental part
p. 1383 - 1385
(2010/04/25)
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- Dinuclear oxidovanadium(IV) and dioxidovanadium(V) complexes of 5,5′-methylenebis(dibasic tridentate) ligands: Synthesis, spectral characterisation, reactivity, and catalytic and antiamoebic activities
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The synthesis of dinuclear oxidovanadium(IV) and dioxidovanadium(V) complexes of two hydrazones [CH2(H2Salnah)2 (I) and CH2(H2sal-inh)2 (II)] derived from 5,5′-methylenebis(salicylaldehyde)
- Maurya, Mannar R.,Khan, Aftab Alam,Azam, Amir,Kumar, Amit,Ranjan, Samir,Mondal, Neelima,Costa Pessoa
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experimental part
p. 5377 - 5390
(2010/06/14)
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- Synthesis of arylbromides from arenes and Nbromosuccinimide bromosuccinimide (NBS) in acetonitrile - A convenient method for aromatic bromination
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Regioselective and chemoselective electrophilic bromination of a wide series of activated arenes using N-bromosuccinimide (NBS) in acetonitrile occurs readily. Environmentally friendly conditions, large substrate scope, and ease of synthesis enhance the utility of this method over other electrophilic bromination conditions.
- Zysman-Colman, Eli,Arias, Karla,Siegel, Jay S.
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experimental part
p. 440 - 447
(2009/12/01)
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- Antiangiogenic versus cytotoxic activity in analogues of aeroplysinin-1
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A series of analogues of the potentially angiogenic inhibitor aeroplysinin-1 1 were synthesized and their in vitro antiangiogenic and cytotoxic activities evaluated. In the case of epoxy ketone 6 and azlactone 36 the relationship sprouting inhibition assay/cytotoxicity in BAE cells was enhanced by one order and two orders of magnitude, respectively, with respect to the reference. These results imply more specific antiangiogenic properties for the synthesized derivatives.
- Cordoba, Ruben,Tormo, Nelida Salvador,Medarde, Antonio Fernandez,Plumet, Joaquin
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p. 5300 - 5315
(2008/03/13)
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- Polymer supported vanadium and molybdenum complexes as potential catalysts for the oxidation and oxidative bromination of organic substrates
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The Schiff base (H2fsal-ohyba) derived from 3-formylsalicylic acid and o-hydroxybenzylamine has been covalently bonded to chloromethylated polystyrene cross-linked with 5% divinylbenzene (abbreviated as PS-H 2fsal-ohyba, I). Treatmen
- Maurya, Mannar R.,Kumar, Umesh,Manikandan
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p. 3561 - 3575
(2007/10/03)
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- Synthesis, characterisation and catalytic potential of hydrazonatovanadium(v) model complexes with [VO]3+ and [VO 2]+ cores
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Reaction between [VO(acac)2] and H2L (H2L are the hydrazones H2sal-nah I or H2sal-fah II; sal = salicylaldehyde, nah = nicotinic acid hydrazide and fah = 2-furoic acid hydrazide) in methanol leads to the formation of oxovanadium(IV) complexes [VOL·H2O] (H2L = I: 1, H2L = II: 4). Aerial oxidation of the methanolic solutions of 1 and 4 yields the dinuclear oxo-bridged monooxovanadium(V) complexes [{VOL}2μ-O] (H 2L = I: 2, H2L = II: 5). These dinuclear complexes slowly convert, in excess methanol, to [VO(OMe)MeOH)L] (H2L = I: 9, H 2L = II: 10), the crystal and molecular structures of which have been determined, confirming the ONO binding mode of the dianionic ligands in their enolate form. Reaction of aqueous K[VO3] with the ligands at pH ca. 7.5 results in the formation of [K(H2O)][VO2L] (H 2L = I: 3, H2L = II: 6). Treatment of 3 and 6 with H 2O2 yields (unstable) oxoperoxovanadium(V) complexes K[VO(O2)L], the formation of which has been monitored spectrophotometrically. Acidification of methanolic solutions of 3 and 6 with HCl affords oxohydroxo complexes, while the neutral complexes [VO 2(Hsal-nah)] 7 and [VO2(Hsal-fah)] 8 were isolated on treatment of aqueous solutions of 3 and 6 with HClO4. These complexes slowly transform into 9 and 10 in methanol, as confirmed by 1H, 13C and 51V NMR. The anionic complexes 3 and 6 catalyse the oxidative bromination of salicylaldehyde in water in the presence of H 2O2/KBr to 5-bromosalicylaldehyde and 3,5- dibromosalicylaldehyde, a reaction similar to that exhibited by vanadate-dependent haloperoxidases. They are also catalytically active for the oxidation of benzene to phenol and phenol to catechol and p-hydroquinone.
- Maurya, Mannar R.,Agarwal, Shalu,Bader, Cerstin,Ebel, Martin,Rehder, Dieter
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p. 537 - 544
(2007/10/03)
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- Does the DABCO-catalysed reaction of 2-hydroxybenzaldehydes with methyl acrylate follow a Baylis-Hillman pathway?
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Evidence is presented which supports the intermediacy of dipolar Baylis-Hillman-type adducts in the synthesis of coumarin and chromene derivatives from the reaction of 2-hydroxybenzaldehydes with methyl acrylate in the presence of 1,4-diazabicyclo[2.2.2]octane (DABCO).
- Kaye, Perry T.,Musa, Musiliyu A.,Nocanda, Xolani W.,Robinson, Ross S.
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p. 1133 - 1138
(2007/10/03)
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- Pyridinium hydrobromide perbromide induces ipsobromodeformylation in o-hydroxy and o-methoxy substituted aromatic aldehydes
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The reaction of o-hydroxy and o-methoxy substituted aromatic aldehydes with PHPB in pyridine gives aromatic bromination products including those arising from ipsobromodeformylation.
- Córdoba, Rubén,Plumet, Joaquín
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p. 9303 - 9305
(2007/10/03)
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- Ortho-substituted aromatic ether compounds and their use in pharmaceutical compositions for pain relief
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The invention provides compounds of formula I: STR1 wherein A, B, D, X, R1, and R3 have any of the values defined in the specification, as well as N-oxides thereof, S-oxides thereof, pharmaceutically acceptable salts thereof, and in vivo hydrolizable esters and amides thereof, that are useful to relieve pain. The invention also provides pharmaceutical compositions as well as synthetic and therapeutic methods relating to such compounds.
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- Regioselective catalytic halogenation of aromatic substrates
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Regioselective chlorination and bromination of some aromatic substances have been carried out using KCl and KBr in presence of sodium perborate as an oxidant and sodium metavanadate, sodium tungstate, ammonium metavanadate and ammonium molybdate as efficient catalysts. This environmentally friendly catalytic halogenation method gave good yields of products under mild conditions.
- Bandgar,Nigal, Neeta J.
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p. 3225 - 3229
(2007/10/03)
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- Synthesis and biological evaluation of aeroplysinin analogues: a new class of receptor tyrosine kinase inhibitors
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Receptor tyrosine kinases (RTKs), such as the epidermal growth factor receptor (EGFR) and the platelet-derived growth factor receptor (PDGFR), are critically involved in the transduction of mitogenic signals across the plasma membrane and therefore in the regulation of cell growth and proliferation. Enhanced RTK activity is associated with proliferative diseases such as cancer, psoriasis and atherosclerosis, while decreased function may be associated for instance with diabetes. EGFR and PDGFR are selectively inhibited by analogues of the marine natural product aeroplysinin. The synthetic inhibitors display IC50 values in the low micromolar range and in contrast to the natural product show pronounced inhibitory activity in cultured cells in vivo. The mechanism of inhibition is likely based on a covalent modification of the target enzymes by reaction of epoxy ketone 8 with various nucleophiles. Copyright (C) 1998 Elsevier Science Ltd.
- Hinterding, Klaus,Knebel, Axel,Herrlich, Peter,Waldmann, Herbert
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p. 1153 - 1162
(2007/10/03)
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- 3,5-Dibromo-2-methoxybenzoic acid from sea sponge Didiscus sp.
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3,5-Dibromo-2-methoxybenzoic acid was isolated from sea sponge Didiscus sp. The structure of the title compound was established by spectral methods, by X-ray diffraction analysis, and by comparing with a synthetic sample prepared from salicylaldehyde.
- Utkina,Fedoreyev,Ilyin,Antipin
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p. 2292 - 2294
(2007/10/03)
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- Molybdenum(VI)-catalysed Bromination. A Molybdenum Analogue Reaction Mimic for the Enzyme Bromoperoxidase
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The molybdenum(VI)-catalysed bromination of organic substrates such as phenols and anilides with KBr in the presence H2O2 in an aqueous medium is reported.
- Bhattercharjee, Manish,Mukherjee, Joy
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p. 238 - 239
(2007/10/03)
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- Bromination Mediated by a Vanadium(V)-Peroxo Complex (GlyH = Glycine): a Functional Model for the Enzyme Bromoperoxidase
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The reaction of potassium bromide with aromatic compounds C6H4XY (X=NHCOMe, Y=H or 4-Me; X=CHO, Y=2-OH) and 5,5-dimethylcyclohexa-1,3-dione in aqueous media in the presence of produces the corresponding brominated compounds; the reaction is proposed to be a mimic for the enzyme bromoperoxidase.
- Bhattacharjee, Manish,Ganguly, Somenath,Mukherjee, Joy
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- REACTION OF MERCAPTOACETIC ACID AND CHLOROACETYL CHLORIDE WITH BENZALAMINO THIAZOLYL COUMARINS
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2-Aryl-3--4-thiazolidinones (III), have been synthesized by the reaction of Schiff's bases (II) derived from 3-(2-amino-4-thiazolyl)-2H-1-benzopyran-2-ones (I) with mercaptoacetic acid.The Schiff's bases on reaction with chloroacetyl chloride in the presence of triethylamine in dioxane gave chloroacetamido derivative (IV) instead of expected compound V.
- Veerabhadraiah, Udarapu,Rajeswar Rao, Vedeela,Padmanabha Rao, Tadepalcy Venkata
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p. 535 - 539
(2007/10/02)
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- Process for nucleophilic fluoroalkylation of aldehydes
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Aryl difluoromethyl sulfone adds to alkehydes under phase transfer conditions to give novel substituted alcohols of the general formula wherein R is an aryl, cycloaliphatic, sec- or tert-aliphatic, or heterocyclic group and Ar is an aryl group. The substituted alcohols of formula I are of particular utility as intermediates in the synthesis of a variety of useful end products. For example, the products of formula I may be utilized in desulfonylation reactions, oxidation reactions and fluorination reactions.
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- Process of preparing hexahydropyrimidines
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This invention relates to hexahydropyrimidines (HHP) of the formula STR1 where R' is a substituted group and R is hydrogen or a substituted group; the process of preparing and the uses therefor, particularly as deterioration inhibitors in hydrocarbon fuels.
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- Metal complexes of bis-hydrazones
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Bis-hydrazone metal complexes of the formula STR1 wherein A denotes an isocyclic or heterocyclic radical, R denotes a H atom, an alkyl group or an aryl radical, M denotes a divalent transition metal and zinc or cadmium, X1 and X2 independently of one another represent alkyl, cycloalkyl, aralkyl or aryl radicals, or conjointly form a fused carbocyclic or heterocyclic aromatic ring, L denotes a ligand having one or more coordinating N or S atoms, and n denotes the number 1 - 5, are useful for coloring plastic and lacquers in fast yellow to red shades.
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- Azomethine pigments
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Azomethine pigments of the formula SPC1 And metal complexes thereof, wherein A denotes an isocyclic or heterocyclic aromatic radical, R denotes a H atom, an alkyl group containing 1-6 C atoms, or an aryl radical, X2 and X4 denote H atoms or halogen atoms, X1 and X3 denote H atoms or halogen atoms, alkoxy or alkylmercapto groups containing 1-6 C atoms, cycloalkoxy groups containing 5-6 C atoms, or aralkoxy, aryloxy or arylmercapto groups, it being possible for one of the substituents X1 -X4 also to be a nitro group which are useful for pigmenting of high molecular material.
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