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A mechanistic approach to the electrografting of carbon surfaces and electrochemical properties of the grafted films – A critical review. Electrochim Acta 2022. [DOI: 10.1016/j.electacta.2022.140693] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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2
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Kohara K, Trowbridge A, Smith MA, Gaunt MJ. Thiol-Mediated α-Amino Radical Formation via Visible-Light-Activated Ion-Pair Charge-Transfer Complexes. J Am Chem Soc 2021; 143:19268-19274. [PMID: 34762420 DOI: 10.1021/jacs.1c09445] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Visible-light-activated electron donor-acceptor complexes offer distinct reaction pathways for the synthesis of complex molecules under mild conditions. Herein, we report a method for the reductive generation of α-amino radicals via the reaction of a visible-light-activated ion-pair charge-transfer complex formed between an in situ-generated alkyl-iminium ion and a thiophenolate. This distinct activation mode is demonstrated through the development of a multicomponent coupling reaction to form substituted aminomethyl-cyclopentanes from secondary amines, cyclopropyl aldehydes, and alkenes. The operationally straightforward transformation displays broad scope and provides a means to generate cyclic amine-containing scaffolds from readily available feedstocks.
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Affiliation(s)
- Keishi Kohara
- Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, United Kingdom, CB2 1EW
| | - Aaron Trowbridge
- Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, United Kingdom, CB2 1EW
| | - Milo A Smith
- Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, United Kingdom, CB2 1EW
| | - Matthew J Gaunt
- Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, United Kingdom, CB2 1EW
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Yang W, Zhang T, Han C, Tang N, Yang H, Xue X. Photoenhanced heterogeneous reaction of O 3 with humic acid: Focus on O 3 uptake and changes in the composition and optical property. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2021; 268:115696. [PMID: 33010673 DOI: 10.1016/j.envpol.2020.115696] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2020] [Revised: 09/15/2020] [Accepted: 09/16/2020] [Indexed: 06/11/2023]
Abstract
Heterogeneous photochemical reaction of O3 with humic acid (HA) under simulated sunlight was performed using a flow tube reactor coupled to an O3 analyzer at ambient pressure. It was confirmed that light significantly enhanced the uptake of O3 on HA. The initial uptake coefficient (γi) and the steady-state uptake coefficient (γss) of O3 under irradiation increased by 1.6 and 3.8 times compared to those in the dark, respectively. The γi and γss on HA varied in the range of 0.76-2.77 × 10-5 and 1.50-9.55 × 10-6, respectively, which were dependent on various environmental factors including HA mass, total irradiance, initial O3 concentration, O2 content, temperature, relative humidity (RH) and HA solution pH. Both γi and γss showed linear dependence on the total irradiance (0-2.07 × 1016 photons/(cm2⋅s)) of the light source, and increased with the HA mass (0-3.2 μg/cm2), temperature (278-298 K) and HA solution pH (4.0-9.6). However, they showed negative correlations with the initial O3 concentration and O2 content. The γi remained constant in the RH range of 7%-60%, while γss exhibited the maximum value at RH = 20%. During the ozonization of HA under irradiation, some functional groups were consumed, including CH2, CH3, aromatic CC, OH, CO, COOH and COO-. HA aged by O3 exhibited a decrease in the mass absorption efficiency (MAE) and a small increase in the absorption Ångström exponent between 300 and 600 nm wavelength (AAE300,600), which was ascribed to changes in the composition of HA during the photochemical ozonization process.
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Affiliation(s)
- Wangjin Yang
- School of Metallurgy, Northeastern University, Shenyang, 110819, China
| | - Tingting Zhang
- School of Metallurgy, Northeastern University, Shenyang, 110819, China
| | - Chong Han
- School of Metallurgy, Northeastern University, Shenyang, 110819, China.
| | - Ning Tang
- Institute of Nature and Environmental Technology, Kanazawa University, Kanazawa, 920-1192, Japan
| | - He Yang
- School of Metallurgy, Northeastern University, Shenyang, 110819, China
| | - Xiangxin Xue
- School of Metallurgy, Northeastern University, Shenyang, 110819, China
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Feskov S. The Green’s function technique for numerical simulations of multichannel electron transfer reactions in electron-donor-acceptor complexes. COMPUT THEOR CHEM 2018. [DOI: 10.1016/j.comptc.2018.10.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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5
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Le CC, MacMillan DWC. Fragment Couplings via CO2 Extrusion-Recombination: Expansion of a Classic Bond-Forming Strategy via Metallaphotoredox. J Am Chem Soc 2015; 137:11938-41. [PMID: 26333771 DOI: 10.1021/jacs.5b08304] [Citation(s) in RCA: 92] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
In this study we demonstrate that molecular fragments, which can be readily coupled via a simple, in situ RO-C═OR bond-forming reaction, can subsequently undergo metal insertion-decarboxylation-recombination to generate Csp(2)-Csp(3) bonds when subjected to metallaphotoredox catalysis. In this embodiment the conversion of a wide variety of mixed anhydrides (formed in situ from carboxylic acids and acyl chlorides) to fragment-coupled ketones is accomplished in good to high yield. A three-step synthesis of the medicinal agent edivoxetine is also described using this new decarboxylation-recombination protocol.
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Affiliation(s)
- Chi Chip Le
- Merck Center for Catalysis at Princeton University , Princeton, New Jersey 08544, United States
| | - David W C MacMillan
- Merck Center for Catalysis at Princeton University , Princeton, New Jersey 08544, United States
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The mechanism of mediated oxidation of carboxylates with ferrocene as redox catalyst in absence of grafting effects. An experimental and theoretical approach. Electrochim Acta 2014. [DOI: 10.1016/j.electacta.2014.04.189] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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7
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Valencia DP, Astudillo PD, Galano A, González FJ. Self-decarboxylation of trichloroacetic acid redox catalyzed by trichloroacetate ions in acetonitrile solutions. Org Biomol Chem 2013; 11:318-25. [PMID: 23165440 DOI: 10.1039/c2ob26961a] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Affiliation(s)
- Drochss P Valencia
- Departamento de Química del Centro de Investigación y de Estudios Avanzados del I.P.N., Av. IPN 2508, Col. San Pedro Zacatenco, 07360, Distrito Federal, Mexico
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Wu J, Zhang F, Zhang H. Facile synthesis of carboxymethyl curdlan-capped silver nanoparticles and their application in SERS. Carbohydr Polym 2012; 90:261-9. [DOI: 10.1016/j.carbpol.2012.05.033] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2012] [Revised: 04/02/2012] [Accepted: 05/01/2012] [Indexed: 10/28/2022]
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9
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Galicia M, González-Fuentes MA, Valencia DP, González FJ. The effect of substituents on the anodic oxidation of aliphatic carboxylates and the passage towards a pseudo-Kolbe reaction. J Electroanal Chem (Lausanne) 2012. [DOI: 10.1016/j.jelechem.2012.03.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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10
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Baduel C, Monge ME, Voisin D, Jaffrezo JL, George C, Haddad IE, Marchand N, D'Anna B. Oxidation of atmospheric humic like substances by ozone: a kinetic and structural analysis approach. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2011; 45:5238-5244. [PMID: 21574573 DOI: 10.1021/es200587z] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
This work explores the heterogeneous reaction between HUmic-LIke Substances (so-called HULIS) and ozone. Genuine atmospheric HULIS were extracted from aerosol samples collected in Chamonix (France) in winter and used in coated flow tube experiments to evaluate heterogeneous uptake of O₃ on such mixtures. The uptake coefficient (γ) was investigated as a function of pH (from 2.5 to 10), O₃ concentration (from 8 to 33 × 10¹¹ molecules cm⁻³), relative humidity (20 to 65%) and photon flux (from 0 to 1.66 × 10¹⁵ photons cm⁻² s⁻¹). Reactive uptake was found to increase in the irradiated experiment with pH, humidity and photon flux. The extract was characterized before and after exposure to O₃ and/or UV light in the attempt to elucidate the effect of the photochemical aging. Carbon content measurements, UV-vis spectroscopy and functional groups analysis revealed a decrease of the UV absorbance as well as of the carbon mass content, while the functionalization rate (COOH and C═O) and therefore the polarity increased during the simulated photochemical exposure.
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Affiliation(s)
- Christine Baduel
- UJF-Grenoble 1/CNRS, Laboratoire de Glaciologie et Géophysique de l'Environnement (LGGE), UMR 5183, Grenoble, F-38041, France
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11
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Hallett-Tapley GL, Schepp NP, Cozens FL. The reactivity of diarylmethyl carbocations within non-protic zeolites. CAN J CHEM 2011. [DOI: 10.1139/v10-150] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The generation of diarylmethyl carbocations within non-protic zeolites (LiY, NaY, KY, RbY, CsY, and NaX) was carried out via laser excitation (266 nm or 266 nm / 308 nm) of diarylacetic acids. Rapid loss of CO2, followed by photochemical oxidation of the diarylmethyl radicals resulted in the formation of the diarylmethyl carbocations. The reactivity of the diarylmethyl carbocations was found to be highly dependent on the alkali metal counterion and the Si/Al ratio of the zeolite framework. Furthermore, the effect of various para-electron donating substituents (4-H, 3-CH3, 4-CH3, 4,4′-CH3, and 4-OCH3) on the diarylmethyl carbocation reactivity was investigated. Comparison of the Hammett plots constructed for the reactivity of the diarylmethyl carbocations in zeolites with those in solution (CH3CN–H2O (1:2) and TFE) showed decreased sensitivity of the electrophilic species towards para-electron donating substituents in the heterogeneous media. The leveling effect observed in the zeolite Hammett plots has been attributed to the presence of an isokinetic relationship, specifically, a low isokinetic temperature for the reaction of diarylmethyl carbocations with the aluminosilicate zeolite framework.
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Affiliation(s)
| | - Norman P. Schepp
- Department of Chemistry, Dalhousie University, Halifax, NS B3H 4J3, Canada
| | - Frances L. Cozens
- Department of Chemistry, Dalhousie University, Halifax, NS B3H 4J3, Canada
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Balcells D, Moles P, Blakemore J, Raynaud C, Brudvig GW, Crabtree RH, Eisenstein O. Molecular recognition in Mn-catalyzed C-H oxidation. Reaction mechanism and origin of selectivity from a DFT perspective. Dalton Trans 2009:5989-6000. [PMID: 19623399 PMCID: PMC2908378 DOI: 10.1039/b905317d] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Experimental studies have shown that the C-H oxidation of Ibuprofen and methylcyclohexane acetic acid can be carried out with high selectivities using [(terpy')Mn(OH(2))(mu-O)(2)Mn(OH(2))(terpy')](3+) as catalyst, where terpy' is a terpyridine ligand functionalized with a phenylene linker and a Kemp's triacid serving to recognize the reactant via H-bonding. Experiments, described here, suggest that the sulfate counter anion, present in stoichiometric amounts, coordinates to manganese in place of water. DFT calculations have been carried out using [(terpy')Mn(O)(mu-O)(2)Mn(SO(4))(terpy')](+) as a model catalyst, to analyze the origin of selectivity and its relation to molecular recognition, as well as the mechanism of catalyst inhibition by tert-butyl benzoic acid. The calculations show that a number of spin states, all having radical oxygen character, are energetically accessible. All these spin states promote C-H oxidation via a rebound mechanism. The catalyst recognizes the substrate by a double H bond. This interaction orients the substrate inducing highly selective C-H oxidation. The double hydrogen bond stabilizes the reactant, the transition state and the product to the same extent. Consequently, the reaction occurs at lower energy than without molecular recognition. The association of the catalyst with tert-butyl benzoic acid is shown to shield the access of unbound substrate to the reactive oxo site, hence preventing non-selective hydroxylation. It is shown that the two recognition sites of the catalyst can be used in a cooperative manner to control the access to the reactive centre.
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Affiliation(s)
- David Balcells
- Université Montpellier 2, Institut Charles Gerhardt, CNRS 5253, cc-1501 Place Eugène Bataillon, 34095, Montpellier, France. Fax: +33 467144839; Tel: +33 467143306
| | - Pamela Moles
- Departament de Química Física i Analítica, Universitat Jaume I, 12080 Castelló, Spain. Fax: +34 964728066; Tel: +34 964728069
| | - James Blakemore
- Yale Chemistry Dept, New Haven, CT, USA.. Fax: +1 203 432 6144; Tel: +1 203 432 3925
| | - Christophe Raynaud
- Université Montpellier 2, Institut Charles Gerhardt, CNRS 5253, cc-1501 Place Eugène Bataillon, 34095, Montpellier, France. Fax: +33 467144839; Tel: +33 467143306
| | - Gary W. Brudvig
- Yale Chemistry Dept, New Haven, CT, USA.. Fax: +1 203 432 6144; Tel: +1 203 432 3925
| | - Robert H. Crabtree
- Yale Chemistry Dept, New Haven, CT, USA.. Fax: +1 203 432 6144; Tel: +1 203 432 3925
| | - Odile Eisenstein
- Université Montpellier 2, Institut Charles Gerhardt, CNRS 5253, cc-1501 Place Eugène Bataillon, 34095, Montpellier, France. Fax: +33 467144839; Tel: +33 467143306
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13
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Gurzadyan GG, Reynisson J, Steenken S. Photoionization versus photoheterolysis of all-trans-retinol. The effects of solvent and laser radiation intensity. Phys Chem Chem Phys 2006; 9:288-98. [PMID: 17186072 DOI: 10.1039/b609165m] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The time-resolved formation of the retinyl carbocation from all-trans-retinol and all-trans-retinol acetate was studied by use of picosecond flash photolysis. From both precursors, the retinyl cation is produced by heterolytic C-O bond cleavage in solvents of medium polarity (acetonitrile, tetrahydrofuran, propanol with Reichardt polarity parameter ET(N) approximately 0.5) and high polarity (EtOH, MeOH, TFE, HFIP, ET(N) > 0.6) during the laser pulse (< or =5 ps) where its lifetime is >10 ns. The absorption maximum of the cation at early times (t < 100 ps) is at lambda = 590-600 nm; it shifts to shorter wavelengths (Deltalambda = 5-10 nm) within 1-10 ns. This spectral shift is suggested to be due to contact ion pair --> solvent-separated ion pair --> free-ion transformation. The quantum yield of cation formation phi(cat) is independent of excitation wavelength (213, 266 or 355 nm). Photoheterolysis proceeds via a one-quantum process. In chlorinated solvents, i.e. n-BuCl, 1,2-dichloroethane, chloroform or CCl(4), formation of the retinol radical cation (which is characterized by a peak at 610 nm and further absorption maxima at approximately 840 and approximately 940 nm) by intermolecular electron transfer to the solvent molecules was detected. The radical cation lifetime in all these solvents is 1.5-2 ns, except for CCl(4) where it is 0.25 ns. The formation of the radical cation or cation was not detected in the low polarity solvents: cyclohexane, hexane, dioxane and p-xylene. However, in solvents of medium and high polarity, at high radiation intensities the radical cation may form in addition to the cation (as a result of two-quantum ionization). DFT calculations confirm our experimental results. The rate of retinol S(1) depopulation (k = 0.3-1 x 10(9) s(-1)) is almost independent of the solvent polarity in the range from cyclohexane to methanol. In highly polar solvents (ET(N) > 0.9) the rate increases to (0.5-5) x 10(10) s(-1).
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Affiliation(s)
- Gagik G Gurzadyan
- Max-Planck-Institut für Bioanorganische Chemie (formerly Max-Planck-Institut für Strahlenchemie), D-45413, Mülheim, Germany.
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14
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Iglesias-Arteaga MA, Juaristi E, González FJ. An electrochemical interpretation of the mechanism of the chemical decarboxylation of 6-carboxyperhydropyrimidin-4-ones. Tetrahedron 2004. [DOI: 10.1016/j.tet.2004.02.052] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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15
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Abel B, Assmann J, Buback M, Grimm C, Kling M, Schmatz S, Schroeder J, Witte T. Ultrafast Decarboxylation of Carbonyloxy Radicals: Influence of Molecular Structure. J Phys Chem A 2003. [DOI: 10.1021/jp0350823] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Bernd Abel
- Institut für Physikalische Chemie, Universität Göttingen, Tammannstrasse 6, 37077 Göttingen, Germany
| | - Jens Assmann
- Institut für Physikalische Chemie, Universität Göttingen, Tammannstrasse 6, 37077 Göttingen, Germany
| | - Michael Buback
- Institut für Physikalische Chemie, Universität Göttingen, Tammannstrasse 6, 37077 Göttingen, Germany
| | - Christian Grimm
- Institut für Physikalische Chemie, Universität Göttingen, Tammannstrasse 6, 37077 Göttingen, Germany
| | - Matthias Kling
- Institut für Physikalische Chemie, Universität Göttingen, Tammannstrasse 6, 37077 Göttingen, Germany
| | - Stefan Schmatz
- Institut für Physikalische Chemie, Universität Göttingen, Tammannstrasse 6, 37077 Göttingen, Germany
| | - Jörg Schroeder
- Institut für Physikalische Chemie, Universität Göttingen, Tammannstrasse 6, 37077 Göttingen, Germany
| | - Thomas Witte
- Institut für Physikalische Chemie, Universität Göttingen, Tammannstrasse 6, 37077 Göttingen, Germany
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16
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Kling M, Schmatz S. Decarboxylation of carbonyloxy radicals: a density functional study. Phys Chem Chem Phys 2003. [DOI: 10.1039/b304544g] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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17
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1,3-dimethoxy-5-methylene-1,3-cyclohexadiene compounds with leaving groups at C6: generation, solvolytic reactivity, and their importance in the photochemistry of 3,5-dimethoxybenzyl derivatives. J Org Chem 2000; 65:4698-705. [PMID: 10959877 DOI: 10.1021/jo000387o] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The photochemistry of 3,5-dimethoxybenzyl compounds with the leaving groups acetate (1a), chloride (1b), bromide (1c), iodide (1d), diethyl phosphate (1e), and trimethylamine (1f), as the chloride, was examined by both product studies and flash photolysis. The isomeric triene, 5-methylene-1,3-cyclohexadiene derivative was observed for the acetate (2a), diethyl phosphate (2e) and trimethylammonium chloride (2f). The solvolysis of these derivatives, 2, was examined in alcohol solvents and the rate correlation with YOTS values gave m = 0.47 (2a) and 0.63 (2e), suggesting SN1 reactivity but with an early transition state. Quantum yields for formation of 2a and 2e indicated that these trienes play only a minor role (approximately 16%) in the overall photochemistry of the corresponding arylmethyl substrates.
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Donor/acceptor organizations and the electron-transfer paradigm for organic reactivity. ADVANCES IN PHYSICAL ORGANIC CHEMISTRY 2000. [DOI: 10.1016/s0065-3160(00)35014-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register]
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19
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Bockman TM, Hubig SM, Kochi JK. Direct Measurement of Ultrafast Carbon−Carbon Cleavage Rates via the Subpicosecond Charge-Transfer Activation of Pinacols. J Am Chem Soc 1998. [DOI: 10.1021/ja980097d] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- T. M. Bockman
- Contribution from the Chemistry Department, University of Houston, Houston, Texas 77204-5641
| | - S. M. Hubig
- Contribution from the Chemistry Department, University of Houston, Houston, Texas 77204-5641
| | - J. K. Kochi
- Contribution from the Chemistry Department, University of Houston, Houston, Texas 77204-5641
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Cozens FL, Cano ML, García H, Schepp NP. Alkali Metal Cation Control of Oxidation Reactions of Radicals in Zeolites. J Am Chem Soc 1998. [DOI: 10.1021/ja971524a] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Frances L. Cozens
- Contribution from the Department of Chemistry, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4J3, and Instituto de Tecnología Química UPV-CSIC, Universidad Politécnica de Valencia, Apartado 22012, 46071 Valencia, Spain
| | - Maria Luz Cano
- Contribution from the Department of Chemistry, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4J3, and Instituto de Tecnología Química UPV-CSIC, Universidad Politécnica de Valencia, Apartado 22012, 46071 Valencia, Spain
| | - Hermenegildo García
- Contribution from the Department of Chemistry, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4J3, and Instituto de Tecnología Química UPV-CSIC, Universidad Politécnica de Valencia, Apartado 22012, 46071 Valencia, Spain
| | - Norman P. Schepp
- Contribution from the Department of Chemistry, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4J3, and Instituto de Tecnología Química UPV-CSIC, Universidad Politécnica de Valencia, Apartado 22012, 46071 Valencia, Spain
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21
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Lucia LA, Abboud K, Schanze KS. Outer Sphere Metal-to-Ligand Charge Transfer in Organometallic Ion Pairs. Inorg Chem 1997. [DOI: 10.1021/ic970351n] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Lucian A. Lucia
- Department of Chemistry, University of Florida, Gainesville, Florida 32611-7200
| | - Khalil Abboud
- Department of Chemistry, University of Florida, Gainesville, Florida 32611-7200
| | - Kirk S. Schanze
- Department of Chemistry, University of Florida, Gainesville, Florida 32611-7200
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Balahura RJ, Sorokin A, Bernadou J, Meunier B. Origin of the Oxygen Atom in C-H Bond Oxidations Catalyzed by a Water-Soluble Metalloporphyrin. Inorg Chem 1997; 36:3488-3492. [PMID: 11670027 DOI: 10.1021/ic9700765] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The monopersulfate oxidation of 4-isopropylbenzoic acid performed in H(2)(18)O and catalyzed by a water-soluble metalloporphyrin indicated that half of the oxygen atoms incorporated in 4-(1-hydroxy-1-methylethyl)benzoic acid, the primary hydroxylation product, came from water. A redox tautomerism of the active high-valent hydroxo-metal-oxo porphyrin intermediate coupled with an oxygen rebound mechanism explained this result. Under similar conditions, ketoprofen was directly oxidized to 3-benzoylacetophenone, via at least two different reaction pathways. Trapping of radical intermediates by molecular oxygen competed with the oxygen rebound mechanism.
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Affiliation(s)
- Robert J. Balahura
- Chemistry Department, University of Guelph, Ontario N1G 2W1, Canada, and Laboratoire de Chimie de Coordination du CNRS, 205 route de Narbonne, 31077 Toulouse Cedex 4, France
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Bockman TM, Hubig SM, Kochi JK. Direct Observation of Ultrafast Decarboxylation of Acyloxy Radicals via Photoinduced Electron Transfer in Carboxylate Ion Pairs. J Org Chem 1997; 62:2210-2221. [PMID: 11671531 DOI: 10.1021/jo9617833] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Charge-transfer (CT) photoactivation of the electron donor-acceptor salts of methylviologen (MV(2+)) with carboxylate donors (RCO(2)(-)) including benzilates [Ar(2)C(OH)CO(2)(-)] and arylacetates (ArCH(2)CO(2)(-)) leads to transient [MV(*)(+), RCO(2)(*)] radical pairs. Femtosecond time-resolved spectroscopy reveals that the photogenerated acyloxy radicals (RCO(2)(*)) rapidly lose carbon dioxide by C-CO(2) bond cleavage, in competition with back-electron transfer to restore the original ion pair, [MV(2+), RCO(2)(-)]. The decarboxylation rate constants for ArCH(2)CO(2)(*) lie in the range (1-2) x 10(9) s(-)(1), in agreement with previous reports. In striking contrast, the C-CO(2) bond scission in Ar(2)C(OH)CO(2)(*) occurs within a few picoseconds (k(CC) = (2-8) x 10(11) s(-)(1)). The rate constants for decarboxylation of these donors approach those of barrier-free unimolecular reactions. Thus, real-time monitoring of the decarboxylation of benziloxy radicals represents the means for the direct observation of the transition state for C-C bond scission.
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Affiliation(s)
- T. Michael Bockman
- Department of Chemistry, University of Houston, Houston, Texas 77204-5641
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Oki M, Fujino I, Kawaguchi D, Chuda K, Moritaka Y, Yamamoto Y, Tsuda S, Akinaga T, Aki M, Kojima H, Morita N, Sakurai M, Toyota S, Tanaka Y, Tanuma T, Yamamto G. Reactivities of Stable Rotamers. XXXIX. Thermal Decomposition oft-Butyl 3-Methyl-3-(substituted 9-triptycyl)peroxybutanoate Rotamers. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 1997. [DOI: 10.1246/bcsj.70.457] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Pincock JA. Photochemistry of Arylmethyl Esters in Nucleophilic Solvents: Radical Pair and Ion Pair Intermediates. Acc Chem Res 1997. [DOI: 10.1021/ar960177r] [Citation(s) in RCA: 108] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- James A. Pincock
- Department of Chemistry, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4J3
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