- Nitrene Photochemistry of Manganese N-Haloamides**
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Manganese complexes supported by macrocyclic tetrapyrrole ligands represent an important platform for nitrene transfer catalysis and have been applied to both C?H amination and olefin aziridination catalysis. The reactivity of the transient high-valent Mn nitrenoids that mediate these processes renders characterization of these species challenging. Here we report the synthesis and nitrene transfer photochemistry of a family of MnIII N-haloamide complexes. The S=2 N-haloamide complexes are characterized by 1H NMR, UV-vis, IR, high-frequency and -field EPR (HFEPR) spectroscopies, and single-crystal X-ray diffraction. Photolysis of these complexes results in the formal transfer of a nitrene equivalent to both C?H bonds, such as the α-C?H bonds of tetrahydrofuran, and olefinic substrates, such as styrene, to afford aminated and aziridinated products, respectively. Low-temperature spectroscopy and analysis of kinetic isotope effects for C?H amination indicate halogen-dependent photoreactivity: Photolysis of N-chloroamides proceeds via initial cleavage of the Mn?N bond to generate MnII and amidyl radical intermediates; in contrast, photolysis of N-iodoamides proceeds via N?I cleavage to generate a MnIV nitrenoid (i.e., {MnNR}7 species). These results establish N-haloamide ligands as viable precursors in the photosynthesis of metal nitrenes and highlight the power of ligand design to provide access to reactive intermediates in group-transfer catalysis.
- Bhuvanesh, Nattamai,Das, Anuvab,Figgins, Matthew T.,Hicks, Madeline H.,Ozarowski, Andrew,Powers, David C.,Reid, Kaleb A.,Telser, Joshua,Van Trieste, Gerard P.
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supporting information
p. 26647 - 26655
(2021/11/18)
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- Spectrophotometric Oxidative Decolorization of Methyl Red with Chloramine-T and Bromamine-T: Comparative Kinetic Modeling and Mechanistic Study
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Abstract: Methyl Red (MR) is a synthetic mono-azo dye which is extensively used as a colorant in textile and paper printing industries. The widespread amount of MR dye in wastewater poses potential threat to ecosystem and human health. In this context, we have developed a simple and expeditious oxidative decolorization technique for the removal of MR dye by organic N-haloamines viz., chloramine-T (CAT) and bromamine-T (BAT) present in the wastewater. The reaction was focused to changes in: (i) concentration of p-toluenesulfonamide, (ii) ionic strength, (iii) dielectric permittivity, (iv) polymerization study, and (v) halide ions effects. The activation parameters were deduced. Oxidation products of MR dye were identified. The rate of oxidation of MR is about four times faster with BAT than with CAT. The chemical oxygen demand value of the dye was determined. Phytotoxicity and economic analysis were carried out for the proposed decolorization process. A plausible mechanism conforming the kinetic data, reaction stoichiometry and product analysis has been proposed. Further, the present redox system can be adopted for treating MR dye present in industrial effluents with suitable modifications to reduce the toxicity caused by MR dye in wastewater.
- Adalagere Somashekar Manjunatha,Sukhdev, Anu,Puttaswamy
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p. 2647 - 2655
(2019/02/26)
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- Bromamine-T as an efficient amine source for Sharpless asymmetric aminohydroxylation of olefins
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Asymmetric aminohydroxylation of various olefins was carried out using bromamine-T as nitrogen source in the presence of (DHQ)2PHAL ligand. The new nitrogen source has been found to be effective in terms of yield and reaction time. The optical purities of the products could be obtained with up to 99% ee.
- Borah, Arun Jyoti,Phukan, Prodeep
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supporting information
p. 713 - 715
(2014/01/23)
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- Mechanistic chemistry of oxidation of balsalazide with acidic chloramine-T and bromamine-T: A comparative spectrophotometric kinetic study
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Balsalazide (BSZ) belongs to a class of non-steroidal anti-inflammatory drugs. Kinetics and mechanism of oxidation of BSZ with sodium N-halo-p-toluenesulfonamides viz., chloramine-T(CAT) and bromamine-T(BAT) in HClO4 medium have been spectrophotometrically investigated (λ max = λambda -{max } =$ 357nm) at 303 K. Under comparable experimental conditions, reactions with both the oxidants follow a first-order dependence of rate on [BSZ] and fractional-order dependence on each [oxidant] and [HClO4]. Activation parameters and reaction constants have been computed. 2-hydroxy-5-nitroso-benzoic acid and 3-(4-nitroso-benzoylamino)-propionic acid are identified as the oxidation products of BSZ with both CAT and BAT. The rate of oxidation of BSZ is about five-fold faster with BAT than with CAT. Plausible mechanism and related rate law have been deduced for the observed kinetics. [Figure not available: see fulltext.]
- Puttaswamy,Dakshayani
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p. 1655 - 1664
(2015/02/05)
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- CO2-induced amidobromination of olefins with bromamine-T
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The carbon dioxide (CO2)-induced amidobromination of olefins with bromamine-T is described. The method can be used in reactions with a wide range of olefins, both aromatic and aliphatic, as well as electron-rich and deficient olefins, leading to the regioselective formation of amidobrominated compounds.
- Hayakawa, Junpei,Kuzuhara, Mitsuhiro,Minakata, Satoshi
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experimental part
p. 1424 - 1430
(2010/06/18)
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- Kinetic and mechanistic studies on the oxidation of ninhydrin by sodium N-bromo-p-toluenesulphonamide in perchloric acid medium
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Kinetics of oxidation of ninhydrin (Nin) by sodium N-bromo-p- toluenesulphonamide (bromamine - T or BAT) in aqueous perchloric acid medium have been studied at 40°C. The rate shows a first order dependence on [BAT], fractional order in [Nin] and inverse fractional order in [H+]. The variation of ionic strength and the addition of the reaction product (p- toluenesulphonamide) and halide ions have no significant effect on the reaction rate. The dielectric effect is negative. Solvent isotope effect is studied using D2O. The reaction fails to induce the polymerisation of acrylonitrile. Composite activation parameters for the reaction have been evaluated from Arrhenius plot by studying the reaction at different temperatures. Michaelis - Menten type of kinetics is proposed and the activation parameters for the rate - determining step have also been computed. The oxidation product of ninhydrin, phthalic acid, has been identified by spot tests and confirmed by IR and PMR spectral data. A mechanism consistent with the observed kinetics is proposed and discussed.
- Puttaswamy,Ramachandrappa
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p. 1272 - 1276
(2007/10/03)
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- Bromamine-T: A superior source of nitrene for aziridination of olefins
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Bromamine-T as a superior source of nitrene compared to Chloramine-T in the Cu-catalyzed aziridination of olefins is reported in this communication.
- Vyas, Renu,Chanda,Bedekar, Ashutosh V.
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p. 4715 - 4716
(2007/10/03)
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- Oxidation of Diphenylmethanol by Bromamine T. A Kinetic and Mechanistic Study
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Bromamine T (BAT) oxidises diphenylmethanol and substituted diphenylmethanols smoothly and quantitatively to the respective benzophenones in aquoeus acetic acid.Mineral acids catalyse the reaction and the rate law is found to be -d/dt=k+>.The reaction is characterised by the absence of any kinetic isotope effect and a break in the Hammett plot with ρ values of -4.2 and -0.4 for the two limbs.Three alternative mechanistic pathways have been proposed involving (i) diphenylmethyl cation, (ii) a 'phenonium ion' type intermediate from the decomposition of the alkyl hydrobromite ester, or (iii) ipso substitution at the benzene ring followed by dehydrobromination and aromatization.
- Gunasekaran, Somasundaram,Venkatasubramanian, Nagaswami
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p. 949 - 954
(2007/10/02)
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- Kinetics and Mechanism of Oxidation of Fluoren-9-ol and Substituted Fluoren-9-ols by Bromamine-T
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The title reactions have been investigated in aq. acetic acid medium both in the presence and absence of perchloric acid.The reactions are first order each in and under both the conditions.There is unit dependence in perchloric acid.The effects of change in polarity of the solvent medium, added toluene-p-sulphonamide and sodium perchlorate have been studied.The reaction exhibits kinetic isotope effect (kH/kD = 2.2).Hammett ρ is found to be -2.8.Activation parameters have been evaluated.A mechanism consistent with rate data has been proposed.
- Gunasekaran, S.,Venkatasubramanian, N.
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p. 774 - 777
(2007/10/02)
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