- Radical Truce-Smiles reactions on an isoxazole template: Scope and limitations
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The use of TiCl3-HCl as promotor in the radical Truce-Smiles reactions of 2-(((3,5-dimethylisoxazol-4-yl)sulfonyl)oxy)benzenediazonium salts has been investigated in detail. During these reactions the desired Truce-Smiles rearrangement (via an ipso-substitution reaction) is accompanied by the formation of a number of by-products including dihydrobenzo[5,6][1,2]oxathiino[3,4-d]isoxazole 4,4-dioxides, dioxidobenzo[e][1,2]oxathiin-3-yl)ethan-1-ones, anilines and chloroaromatics. Replacing TiCl3-HCl by Cu(NO3)2-Cu2O as reductant in these reactions was found to afford broadly comparable product distributions. Competition and radical clock experiments also provide an indication of the relative susceptibility of the isoxazole nucleus towards attack by aryl radicals.
- Rashid, Srood O.,Almadhhi, Sultan S.,Berrisford, David J.,Raftery, James,Vitorica-Yrezabal, Inigo,Whitehead, George,Quayle, Peter
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p. 2413 - 2430
(2019/03/23)
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- Acceptorless Dehydrogenation of Hydrocarbons by Noble-Metal-Free Hybrid Catalyst System
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A hybrid catalysis that comprises an acridinium photoredox catalyst, a thiophosphate organocatalyst, and a nickel catalyst-enabled acceptorless dehydrogenation of hydrocarbons is reported. The cationic nickel complex played a critical role in the reactivity. This is the first example of acceptorless dehydrogenation of hydrocarbons by base metal catalysis under mild reaction conditions of visible light irradiation at room temperature.
- Fuse, Hiromu,Kojima, Masahiro,Mitsunuma, Harunobu,Kanai, Motomu
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supporting information
p. 2042 - 2045
(2018/04/16)
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- Hybrid Catalysis Enabling Room-Temperature Hydrogen Gas Release from N-Heterocycles and Tetrahydronaphthalenes
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Hybrid catalyst systems to achieve acceptorless dehydrogenation of N-heterocycles and tetrahydronaphthalenes-model substrates for liquid organic hydrogen carriers-were developed. A binary hybrid catalysis comprising an acridinium photoredox catalyst and a Pd metal catalyst was effective for the dehydrogenation of N-heterocycles, whereas a ternary hybrid catalysis comprising an acridinium photoredox catalyst, a Pd metal catalyst, and a thiophosphoric imide organocatalyst achieved dehydrogenation of tetrahydronaphthalenes. These hybrid catalyst systems allowed for 2 molar equiv of H2 gas release from six-membered N-heterocycles and tetrahydronaphthalenes under mild conditions, i.e., visible light irradiation at rt. The combined use of two or three different catalyst types was essential for the catalytic activity.
- Kato, Shota,Saga, Yutaka,Kojima, Masahiro,Fuse, Hiromu,Matsunaga, Shigeki,Fukatsu, Arisa,Kondo, Mio,Masaoka, Shigeyuki,Kanai, Motomu
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supporting information
p. 2204 - 2207
(2017/02/23)
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- A mild and ligand-free Ni-catalyzed silylation via C-OMe cleavage
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Metal-catalyzed transformations that forge carbon-heteroatom bonds are of central importance in organic synthesis. Despite the formidable potential of aryl methyl ethers as coupling partners, the scarcity of metal-catalyzed C-heteroatom bond formations via C-OMe cleavage is striking, with isolated precedents requiring specialized, yet expensive, ligands, high temperatures, and π-extended backbones. We report an unprecedented catalytic ipso-silylation of aryl methyl ethers under mild conditions and without recourse to external ligands. The method is distinguished by its wide scope, which includes the use of benzyl methyl ethers, vinyl methyl ethers, and unbiased anisóle derivatives, thus representing a significant step forward for designing new C-heteroatom bond formations via C-OMe scission. Applications of this transformation in orthogonal silylation techniques as well as in further derivatizations are also described. Preliminary mechanistic experiments suggest the intermediacy of Ni(0)-ate complexes, leaving some doubt that a canonical catalytic cycle consisting of an initial oxidative addition of the C-OMe bond to Ni(0) species comes into play.
- Zarate, Cayetana,Nakajima, Masaki,Martin, Ruben
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p. 1191 - 1197
(2017/05/16)
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- Degradation of one-side fully-chlorinated 1,2,3,4-tetrachloronaphthalene over Fe-Al composite oxides and its hypothesized reaction mechanism
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The degradation of 1,2,3,4-tetrachloronaphthalene (CN-27) featuring a one-side fully-chlorinated aromatic ring, was evaluated over three of the prepared rod-like Fe-Al composite oxides (FeAl-1, FeAl-5 and FeAl-10). The results showed that their reactive activities were in the order of FeAl-5 ≈ FeAl-10 ? FeAl-1, which could be attributed to their different pore structural properties and reactive sites caused by the different phase interaction between iron species and the γ-Al2O3. The generation of trichloronaphthalenes (1,2,3-TrCN and 1,2,4-TrCN, i.e. CN-13 and CN-14), dichloronaphthalenes (1,2-DiCN, 1,3-DiCN, 1,4-DiCN and 2,3-DiCN, i.e. CN-3, CN-4, CN-5 and CN-10) and monochloronaphthalenes (1-MoCN and 2-MoCN, i.e. CN-1 and CN-2) suggested the occurrence of successive hydrodechlorination reactions. The amount of CN-14 exceeded that of CN-13 from 71.5% to 77.7% across the three different systems, revealing the preferred occurrence of the first hydrodechlorination step at the β-position. This is dissimilar to the preference at the α-position observed during the dechlorination of octachloronaphthalene (CN-75) over micro/nano Fe3O4. The structural differences between one-side and two-side fully-chlorinated aromatic rings would have a pronounced impact on the reactivity of the chlorine substitution position. The major hydrodechlorination pathway was judged to be CN-27 → CN-14 → CN-4 → CN-2. Additionally, the detected 1,2,3,4,6-pentachloronaphthalene (CN-50) and 1,2,4,6/7-tetrachloronaphthalenes (CN-33/34) suggested the reverse chlorination reaction also happened while the hydrodechlorination reaction was occurring. The C-Cl bond dissociation energies (BDEs) of the parent and daughter polychlorinated naphthalene (PCN) congener were calculated using density functional theory (DFT), to achieve a deeper understanding of a different product yield distribution.
- Liu, Yalu,Lu, Huijie,Pan, Wenxiao,Li, Qianqian,Su, Guijin,Zheng, Minghui,Gao, Lirong,Liu, Guorui,Liu, Wenbin
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p. 17577 - 17585
(2017/03/31)
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- A mild Ni/Cu-catalyzed silylation via C -O cleavage
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A Ni/Cu-catalyzed silylation of unactivated C-O electrophiles derived from phenols or benzyl alcohols is described. This transformation is characterized by its wide scope and mild conditions, providing a direct access to synthetically versatile silylated compounds. The protocol allows for the coupling of C(sp 2)-O and even C(sp3)-O bonds with similar efficiency.
- Zarate, Cayetana,Martin, Ruben
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p. 2236 - 2239
(2014/03/21)
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- Iron(III)-mediated photocatalytic selective substitution of aryl bromine by chlorine with high chloride utilization efficiency
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An iron(III)-mediated photocatalytic method for the conversion of aryl, heteroaryl and polycyclic aromatic bromides to the corresponding chlorides with high selectivity has been achieved successfully. The mild reaction conditions and high chloride utilization efficiency promise a bright future for chlorination reactions. The Royal Society of Chemistry 2014.
- Wang, Ying,Li, Lina,Ji, Hongwei,Ma, Wanhong,Chen, Chuncheng,Zhao, Jincai
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supporting information
p. 2344 - 2346
(2014/03/21)
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- Analysis and structure prediction of chlorinated polycyclic aromatic hydrocarbons released from combustion of polyvinylchloride
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Chlorinated polycyclic aromatic hydrocarbons (Cl-PAHs) released from combustion of polyvinylchloride (PVC) at different furnace temperatures were investigated. A laboratory-scale tube-type furnace with electric heating was utilized to control combustion conditions. Glass fabric filters and adsorbents were used to collect the combustion emissions. Following Soxhlet extraction, concentration and column chromatography purification, isomers separation, selective detection and identification of Cl-PAHs were performed on GC/MS system on the basis of retention data and mass spectra. Their quantification was accomplished by using external standard calibration technique. About 18 Cl-PAHs were determined, most of which were monochlorinated derivatives of naphthalene, biphenyl, fluorene, phenanthrene, anthracene, fluoranthene and pyrene. Only two dichlorophenanthrenes or anthracenes were identified. The possible positions of chlorine atoms attached to the aromatic rings are predicted by quantitative structure-property relationship. The levels of these compounds were in the range of 0.30-29.08 μg/g PVC. The relationship between the formation of Cl-PAHs and PAHs was discussed.
- Wang, Dongli,Xu, Xiaobai,Chu, Shaogang,Zhang, Daren
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p. 495 - 503
(2007/10/03)
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- Formation of polychlorinated naphthalenes on fly ash
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During the oxidative degradation of carbonaceous material on fly ash, besides PCDD/F, PCPh, PCBz, PCB, polychlorinated naphthalenes (PCN or Cl(x)N) are formed. Thermal experiments were carried out with fly ash from a municipal waste incinerator at 300°C and reaction times of 0.5 h up to 4 h. For the study an analytical method using GC/MS was developed similar to that, used in dioxin-analysis. Isomer specific identification of chloronaphthalenes formed on fly ash was realized by comparison of Cl(x)N from technical PCN- mixtures (Halowax). For quantification of the PCN formed, 13C- labelled PCB-standards were used as internal standards because no 13C- labelled PCN- compounds were available. Both, technical PCN-mixtures and PCN formed on fly ash show a characteristic pattern of Cl(x)N-congeners according to their difference in formation. Cl2N - Cl3N were formed most and Cl1N - Cl3N were also found in the gas phase in high amounts. A single isomer 1,2,3,5,6,7-Cl6N, known as a strongly bioaccumulating and toxic PCN, is formed in higher amounts together with 1,2,3,4,6,7-Cl6N.
- Schneider,Stieglitz,Will,Zwick
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p. 2055 - 2070
(2007/10/03)
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- Determination of the gas-phase acidities of halogen-substituted aromatic compounds using the silane-cleavage method
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The gas-phase acidities of halogen-substituted aromatic compounds have been determined in a flowing afterglow-triple quadrupole apparatus with use of the silane cleavage method developed by DePuy and co-workers [C. H. DePuy, S. Gronert, S. E. Barlow, V. M. Bierbaum and R. Damrauer, J. Am. Chem. Sec., 111, 1968 (1989)]. In this method the relative yields of siloxide ion products produced in reactions of OH- with trimethylsilyl- or phenyidimethylsilyl-substituted aromatic compounds are correlated with the difference in gas-phase acidity of the accompanying neutral products. Acidities are reported for different ring-positions in fluoro-, chloro- and bromobenzene, chloro- and bromonaphthalene and benzyl chloride. Excellent precision is achieved in most cases, with assigned uncertainties less than 23 kcal/mol. Goad agreement is obtained between the acidities determined with use of two different types of silane precursor. Halogen-substitution increases the gas-phase acidities of benzene and naphthalene by similar amounts (13-14 kcal/mol). The effects on different ring-positions in benzene and naphthalene are shown to be primarily inductive in nature, falling-off by a consistent 2.5-3.5 kcal/mol per bond separating the acidic site from the haloges-bearing carbon in the chlorine and bromine-substituted systems. Larger effects are evident in the positional acidities of fluorobenzene. The meta and pava position acidities of halobenzenes are shown to be linearly correlated with the acidities of the corresponding meta and pava halophenols, haloanilines and halotoluenes.
- Wenthold,Squires
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- The thermal conversions of 6,6-difluorobicyclo[3.1.0]hex-2-enes to fluorobenzenes. An interesting dichotomy of mechanisms
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A kinetic study of the thermal, dehydrofluorinative aromatization reactions of two ostensibly-similar 6,6-difluorobicyclo[3.1.0]hex-2-ene systems led to the conclusion that drastically different mechanisms operate for the two reactions. Activation parameters, solvent effects, kinetic isotope effects, isotope labelling experiments and observation of reactive intermediates all contributed to the conclusion that the reaction of 6,6-difluorobicyclo[3.1.0]hex-2-ene, 1, proceeds via a homolytic hydrogen-shift rearrangement, while the reaction of 2,3-benzo-6,6-difluorobicyclo[3.1.0]hex-2-ene, 6, proceeds via a solvolytic mechanism involving rate-determining carbocation formation.
- Dolbier Jr.,Keaffaber,Burkholder,Koroniak,Pradhan
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p. 9649 - 9660
(2007/10/02)
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- Generation of Radical-cations from Naphthalene and Some Derivatives, both by Photoionization and Reaction with SO4-.: Formation and Reactions Studied by Laser Flash Photolysis
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Radical-cations from naphthalene and some derivatives have been generated in aqueous acetonitrile both by direct photolysis (with λ 248 nm light via biphotonic ionization) and via reaction with SO4-..The radical-cation reacts rapidly with the parent substrate (k ca. 1E8 dm3 mol-1 s-1) and with nucleophiles (e. g. with N3- k = 4.2*1E9 dm3 mol-1 s-1 or with water, k 4*1E4 s-1 ).The radical-cation from 1-naphthylethanoic acid undergoes rapid decarboxylation (k 5*1E5 s-1).The radical cations from 4-methyl- and 4-methoxy-phenylethanoic acid also rapidly decarboxylate to yield the corresponding benzyl radicals.
- Steenken, Steen,Warren, Cathryn J.,Gilbert, Bruce C.
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p. 335 - 342
(2007/10/02)
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- Electron Transfer Reactions. XIX. Outer-Sphere Electron Transfer Reactions between Hexachloroosmate(V) and Organic Compounds
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The reaction between tetraphenylphosphonium hexachloroosmate(V), a strong one-electron oxidant, and typical organic electron transfer reagents has been studied by preparative, kinetic and theoretical methods.Like tungsten hexachloride, hexachloroosmate(V) supports characteristic oxidative nuclear and/or side-chain acetoxylation of aromatic compounds in the presence of an acetate ion source.With tetramethylstannane, the reaction is first order in both reagents and shows no dependence on ->, the acetate ion source employed in this study.For 4-methoxytoluene (PMT) and naphthalene (Naph), first order behaviour in -> and is observed whereas reaction orders of 1.4 and 0.5-0.7 in -> and -1.0 and -0.5 in 2->infinite, respectively, indicate that back electron transfer competes with base/nucleophile capture of the intermediate radical cation in a mechanism involving initial, reversible electron transfer followed by a rate-determining follow-up reaction of the radical cation.This is supported in the 4-methoxytoluene case by a strong kinetic deuterium isotope effect upon the measured rate parameter, kH/kD being 4.1(2) whis is normal for this reaction type.The electron transfer rate constants for the three substrates were evaluated (tetramethylstannane 10.1, 4-methoxytoluene 16 and naphthalene 5.3 M-1s-1) and compared with values calculated by the Marcus treatment.With the assumption that the self-exchange reorganization energies, λ(PMT-cation radical/PMT) and λ(Naph-cation radical/Naph), are high, 50 and 30 kcal mol-1, respectively, the agreement is satisfactory.
- Eberson, Lennart,Nilsson, Monica
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p. 1062 - 1070
(2007/10/02)
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- Highly Selective Aromatic Chlorination. Part 4. The Chlorination of Aromatic Hydrocarbons with N-Chloroamines in Acidic Solution
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Benzene, toluene, some polymethylbenzenes, and naphthalene have been treated with N-chlorotrialkylammonium salts and N-chlorodialkylamines in trifluoroacetic acid at room temperature.With benzene, toluene, and 1,3,5-trimethylbenzene the major products arise from aromatic chlorination whereas with the other polymethylbenzenes side-chain reactions predominate.By controlling the acidity of the reaction and the nature of the N-chloroamine, the chlorination of toluene can be made to give preferentially 2- or 4-chlorination.However, the selectivities are not as great as reported previously with electron-rich aromatic compounds with a ?-donor substituent.The products from the reaction of naphthalene are very dependent on the structure of the N-chlorinated amine.The bulky N-chlorotrialkylammonium salts selectively chlorinate the 1-position, but in low yield, whereas the less hindered N-chloropiperidine gives good yields of 1-(1-piperidino)-naphthalene.The results from these studies are discussed in terms of arenium-ion and electron-transfer mechanisms.
- Smith, John R. Lindsay,McKeer, Linda C.,Taylor, Jonathan M.
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p. 1537 - 1544
(2007/10/02)
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- PHOTODECARBOXYLATIVE CHLORINATION OF CARBOXYLIC ACIDS VIA THEIR BENZOPHENONE OXIME ESTERS
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Decarboxylative chlorination of various aromatic and aliphatic carboxylic acids is performed successfully by the photolysis of their benzophenone oxime esters in carbon tetrachloride and corresponding chloro compounds are prepared in good yields.High selective generation of the certain radical and efficiency of the stable radical precursor, benzophenone oxime ester, afford much advantage for radical chemistry.
- Hasebe, Masato,Tsuchiya, Takashi
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p. 6287 - 6290
(2007/10/02)
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- FACILE RETRO DIELS-ALDER REACTION OF A VINYL LITHIUM COMPOUND
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Attempts to generate benzobarrelyne 8 by loss of lithium chloride from 4 resulted in a facile retro Diels-Alder reaction of the "dimeric" adduct formed by addition of 4 to 8.
- Hart, Harold,Shahlai, Khalil
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p. 5437 - 5440
(2007/10/02)
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- Acylation of naphthalenes
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Naphthalene substituted in the 2- or β-position with an electron-donating substituent can be acylated with high regioselectivity in the 6-position by using an acylating agent in substantially anhydrous hydrogen fluoride which functions both as catalyst and solvent.
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- A Computerised Least Square Method for Determination of Stability Constants of 1:1 Molecular Complexes and Chemical Shift of Pure Complexes from Nuclear Magnetic Resonance Data
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A computerised method utilising nuclear magnetic resonance data has been developed for the determination of stability constants of 1:1 molecular complexes.It is based on the principle of least squares in which the coefficients are adjusted under a constraint with the help of Lagrange's method of undetermined multipliers.The method utilises the complete expression for equilibrium constant and is mathematically rigorous, straightforward, non-iterative and requires very little computer time.
- Seal, B. K.,Mukherjee, A. K.
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p. 413 - 415
(2007/10/02)
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- Electron Transfer Reactions in Organic Chemistry. VII. Oxidative Acetoxylation of Aromatic Compounds by Tungsten Hexachloride
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Tungsten hexachloride, a high-potential oxidant, causes fast oxidative acetoxylation of ring and/or α positions of aromatic compounds, even as difficalty oxidizable ones as mesitylene and p-xylene.Chlorination is a completing reaction which cannnot be completely suppressed.The acetoxylation process in all likelihood proceeds via an electron transfer mechanism, involving initial formation of the radical cation of the substrate.
- Eberson, Lennart,Joensson, Lennart,Saenneskog, Owe
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p. 113 - 122
(2007/10/02)
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- Generation of 2-Chloronaphthalene-1,3-diyl
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Reaction of 1-bromo-3,4-benzo-6,6-dichlorobicyclohexane with potassium tert-butoxide in tetrahydrofuran yields 2-chloronaphthalene along with nine other naphthalenes which result from solvent incorporation or reaction with nucleophile (Br-, Cl-, t-BuO-).Use of tetrahydrofuran-d8 as the solvent leads to the incorporation of two deuterium atoms into the chloronaphthalene.This result is interpreted in terms of a 1,3-dehydronaphthalene opening to the diradical, followed by abstraction of deuterium atoms from the solvent.The products which result from incorporation of solvent would then arise by dimerization of radical pairs.The remaining products are thought to arise from nucleophilic addition to the closed form of the dehydronaphthalene.
- Billups, W.E.,Buynak, John D.,Butler, Dorothy
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p. 4636 - 4641
(2007/10/02)
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