- N -Hydroxyphthalimide/benzoquinone-catalyzed chlorination of hydrocarbon C-H bond using N -chlorosuccinimide
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The direct chlorination of C-H bonds has received considerable attention in recent years. In this work, a metal-free protocol for hydrocarbon C-H bond chlorination with commercially available N-chlorosuccinimide (NCS) catalyzed by N-hydroxyphthalimide (NHPI) with 2,3-dicyano-5,6-dichlorobenzoquinone (DDQ) functioning as an external radical initiator is presented. Aliphatic and benzylic substituents and also heteroaromatic ones were found to be well tolerated. Both the experiments and theoretical analysis indicate that the reaction goes through a process wherein NHPI functions as a catalyst rather than as an initiator. On the other hand, the hydrogen abstraction of the C-H bond conducted by a PINO species rather than the highly reactive N-centered radicals rationalizes the high chemoselectivity of the monochlorination obtained by this protocol as the latter is reactive towards the C(sp3)-H bonds of the monochlorides. The present results could hold promise for further development of a nitroxy-radical system for the highly selective functionalization of the aliphatic and benzylic hydrocarbon C-H.
- Li, Zi-Hao,Fiser, Béla,Jiang, Biao-Lin,Li, Jian-Wei,Xu, Bao-Hua,Zhang, Suo-Jiang
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supporting information
p. 3403 - 3408
(2019/04/01)
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- Method for synthesizing aromaticnitrile by using metalloporphyrin to catalyze aromatic olefin
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The invention discloses a method for synthesizing aromaticnitrile by using metalloporphyrin to catalyze aromatic olefin. The method is characterized in that an aromatic alkene compound or an aromaticheterocyclic alkene compound and nitrite are reacted to generate an aromaticnitrile compound or an aromatic heterocyclic nitrile compound under the catalyzing function of the metalloporphyrin by a one-step method in air atmosphere and an acid solution system. The method has the advantages that (1) the reaction conditions are moderate, the operation is simple, the control is easy, and the yield rate is higher; (2) the high-efficiency metalloporphyrin catalyst is used, but the poisonous CN (carbon-nitrogen) negative ion reagent is not used, so that the pollution to the environment is decreased;(3) the prices of raw materials, nitrogen sources, acid reagents and the like are low, the obtaining is easy, the production cost is obviously reduced, and the method can be popularized and applied toindustrialized production.
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Paragraph 0133-0137
(2018/03/01)
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- Mild Aliphatic and Benzylic Hydrocarbon C-H Bond Chlorination Using Trichloroisocyanuric Acid
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We present the controlled monochlorination of aliphatic and benzylic hydrocarbons with only 1 equiv of substrate at 25-30 °C using N-hydroxyphthalimide (NHPI) as radical initiator and commercially available trichloroisocyanuric acid (TCCA) as the chlorine source. Catalytic amounts of CBr4 reduced the reaction times considerably due to the formation of chain-carrying ·CBr3 radicals. Benzylic C-H chlorination affords moderate to good yields for arenes carrying electron-withdrawing (50-85%) or weakly electron-donating groups (31-73%); cyclic aliphatic substrates provide low yields (24-38%). The products could be synthesized on a gram scale followed by simple purification via distillation. We report the first direct side-chain chlorination of 3-methylbenzoate affording methyl 3-(chloromethyl)benzoate, which is an important building block for the synthesis of vasodilator taprostene.
- Combe, Sascha H.,Hosseini, Abolfazl,Parra, Alejandro,Schreiner, Peter R.
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p. 2407 - 2413
(2017/03/11)
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- Direct synthesis of nitriles from cleavage of C=C double bond with nitrite as the nitrogen source and oxidant
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The transformation of the C=C bond of olefin to nitriles has been developed, using easily available NaNO2 as both the nitrogen source and oxidant. Several aryl, heterocyclic nitriles with various substituting groups could be successfully prepared in good to high yields. Based upon experimental observations, a possible reaction mechanism is proposed.
- Liu, Qiang,Fang, Bao,Bai, Xiaohui,Liu, Yuan,Wu, Yao,Xu, Guiming,Guo, Cancheng
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supporting information
p. 2620 - 2623
(2016/06/01)
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- Sulfite formation versus chlorination of benzyl alcohols with thionyl chloride
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Recently, we have reported the photolytic decay of a library of para-substituted dibenzylic sulfites in a Srinivasan-Griffin-Rayonet photochemical reactor. In an attempt to synthesize the complete library for that study we discovered that bis(p-methoxybenzyl) sulfite and bis(p-phenoxybenzyl) sulfite could not be formed and only their corresponding benzyl chlorides were synthesized. Thus, sulfite formation versus chlorination of a range of para-substituted benzyl alcohols with thionyl chloride was investigated. Sulfite formation was observed to be parabolically related to Swain and Lupton's Field ?-values while chloride formation was found to be linearly related to Swain and Lupton's Field ?-values.
- Rodriguez, Deana A.,Priefer, Ronny
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p. 3045 - 3048
(2014/05/20)
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- Large-scale preparation of polyfunctional benzylic zinc reagents by direct insertion of zinc dust into benzylic chlorides in the presence of lithium chloride
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Highly functionalized benzylic zinc chlorides are prepared by the direct insertion of commercially available zinc dust into the corresponding benzylic chlorides in the presence of stoichiometric amount of lithium chloride. These polyfunctional zinc organometallics react with various electrophiles leading to a broad range of functionalized products. Georg Thieme Verlag Stuttgart.
- Metzger, Albrecht,Argyo, Christian,Knochel, Paul
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experimental part
p. 882 - 891
(2010/10/01)
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- Reaction of PbO2 with Solutions of Methylbenzonitriles
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The yield of products formed by low-temperature oxidation of methylbenzonitriles with PbO2 in fluorosulfonic acid solutions was studied in relation to the stabilization factor of the reaction system. The revealed correlation is common for methylbenzonitriles differing in the degree of alkylation and in the oxidation mechanism.
- Kol'tsov,Salfetnikova
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p. 389 - 393
(2007/10/03)
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- Process for producing cyanobenzyl compounds
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An industrially advantageous process for producing cyanobenzyl compounds under mild conditions from relatively easily available cyanobenzylamine having a cyano group on the benzene ring or a compound thereof which is ring-substituted with a chlorine atom, a fluorine atom, etc. The process for producing a cyanobenzyl compound includes transforming an aminomethyl group of a cyanobenzylamine compound into a hydroxymethyl group, a halogenomethyl group, or an acyloxymethyl group without causing damage to a cyano group on the benzene ring. The transformation may be carried out by use of nitrosonium ions.
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- Oxidation of Aromatic Compounds. V. Oxidation of Substituted Benzonitriles and 2,4,6-Triaryl-1,3,5-Triazines in System HSO3F-PbO2
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Low-temperature oxidation of substituted benzonitriles by the system HSO3F-PbO2 proceeds with intermediate formation of cation-radicals and leads to substitution of hydrogen atoms of the methyl group or benzene ring. This reaction provides a route for preparation of chloromethylsubstituted benzonitriles, diarylmethanes, diaryls, arylfluorosulfonates and substituted benzamides with cyano groups. In the case of methyl derivatives of 2,4,6-triphenyl-1,3,5-triazine substitution of the first and then the second hydrogen atom of the same methyl group transforms it into hydroxy or chloromethyl group, or into the aldehyde function.
- Rudenko,Salfetnikova,Vasil'ev
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p. 1447 - 1470
(2007/10/03)
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- THE ESR SPECTRA, STRUCTURE, AND REACTIVITY OF AROMATIC RADICAL-CATIONS IN SUPERACIDS
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The oxidation of aromatic compounds by lead dioxide in superacids based on fluorosulfonic acid at -75 deg C takes place by a one-electron mechanism and leads in many cases to relatively stable radical-cations.The ESR spectra, the isotropic hyperfine coupling constants, data on the reactivity of the radical-cations, and the structures of the final products from their transformations under "long-life" conditions are presented.
- Rudenko, A. P.
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p. 1946 - 1980
(2007/10/03)
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- AN EFFECTIVE CHLORINATING AGENT BENZYLTRIMETHYLAMMONIUM TETRACHLOROIODATE, BENZYLIC CHLORINATION OF ALKYLAROMATIC COMPOUNDS
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The reaction of alkylaromatic compounds with benzyltrimethylammonium tetrachloroiodate in carbon tetrachloride in the presence of AIBN under reflux for several hours gave α-chloro-substituted compounds in fairly good yields.
- Kajigaeshi, Shoji,Kakinami, Takaaki,Moriwaki, Masayuki,Tanaka, Toshio,Fujisaki, Shizuo
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p. 5783 - 5786
(2007/10/02)
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- Electrochemical reductive alkylation of (benzophenone)Cr(CO)3 and (benzophenone)2
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The electrochemical reduction of (benzophenone)Cr(CO)3 and (benzophenone)2 in the presence of a series of alkyl chlorides which are more difficult to reduce, has been carried out in N,N-dimethylformamide on a mercury pool cathode.When methyl chloride and p-cyanobenzyl chloride are used as alkylating agents, complexed monoalkylated ethers are exclusively obtained as substitution products, in yields ranging from 36 to 54percent.Complexed alkylated alcohols are isolated as the major products when (benzophenone)Cr(CO)3 is reduced in the presence of benzyl-chloride and its 2,3,5-trimethyl derivative, in 48 and 44percent yields, respectively.These last results suggest the intermediate formation of a charge transfer complex between the aromatic ring of the electrophile and the complexed ketone.
- Gautheron, B.,Degrand, C.,Bikrani, M.
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p. 349 - 356
(2007/10/02)
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- MECHANISMS OF FREE-RADICAL REACTIONS. XX. REACTIVITY IN THE FREE-RADICAL HALOGENATION REACTIONS OF ARYLFLUOROALKANES
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The free-radical chlorination and bromination of meta- and para-substituted benzyl fluorides and 1,1-difluoro-2-phenylethane and also the chlorination of 1-fluoro-2-arylethanes by phenylchloroiodonium chloride and the bromination of meta- and para-substituted benzyl bromides were studied by the method of competing reactions.In all cases a good correlation is observed between log krel and the Brown ?+ constants.In cases where change in the reactivity in the transition from one reaction series to another is due mainly to the polar effect of the substituent whilethe selectivity is measured in relation to the polar effect direct relationships are observed between the reactivity and the selectivity.
- Dneprovskii, A. S.,Eliseenkov, E. V.
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p. 711 - 719
(2007/10/02)
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- Intramolecular Electron Transfer and Dehalogenation of Anion Radicals. 3. Halobenzonitriles and Cyanobenzyl Halides
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One-electron reduction of halobenzonitriles and cyanobenzyl halides produces the anion radicals which then undergo intramolecular electron transfer leading to dehalogenation.Kinetic spectrophotomethric pulse radiolysis allowed the observation of the halobenzonitrile anion radicals and the determination of their dehalogenation rates.The rates varied from 104 to >107 s-1 depending on the halogen and its position relative to cyano group.The production of X- was measured in steady-state radiolysis experiments, and the participation of cyanophenyl radicals as intermediates was also deduced from observation of chain reaction.The anion radicals of cyanobenzyl halides were not observed since they dehalogenate very rapidly.The cyanobenzyl radicals produced by this process were monitored spectrophotometrically.The rates of dehalogenation of the anion radicals studied here are at least 5 orders of magnitude higher than the corresponding values determined previously for analogous nitro derivatives, but the pattern of reactivities is similar in both series of radicals.
- Neta, P.,Behar, D.
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p. 103 - 106
(2007/10/02)
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- Polar Radicals. 15. Interpretation of Substituent Effects on the Mechanism of Electrolytic Reduction of the Carbon-Halogen Bond in Series of Substituted Benzyl Halides
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The electrochemical polarographic reduction of a series of substituted benzyl chlorides and benzyl bromides showed half-wave potentials which gave excellent Hammett linear free-energy correlations for each series.These correlations were obtained using ?- substituent constants.The correlation with ?- suggests that the potential-determining electrochemical process involves carbon-halogen bond breaking or, alternatively, radical anion intermediate formation.The Hammett ρ values for each correlation were calculated; their magnitudes, Cl>Br, were in the inverse order of their reactivity toward chemical reduction.As in the case of trialkyltin hydride reduction, both ρ values were positive.The results of the polarographic electroreduction of benzyl iodide and benzylmercuric iodide confirmed the previously reported mechanism for reduction;namely, that the iodide underwent reaction with mercury to form benzylmercuric iodide, which was subsequently reduced, as was benzylmercuric iodide itself, by a process having two distinct polarographic waves.The half-wave potentials for the second wave (the wave at the most negative potential) for series of substituted benzyl iodides and benzylmercuric iodides were both found to give excellent Hammett correlation, having positive ρ values.The correlations were both obtained by using ?- substituent constants.The success of the use of these substituent constants was taken as a confirmation of the suggestion, previously made, that the second step in the electroreduction was the reduction of the benzylmercuryl radical, and suggests that the process is concerted with carbon-mercury bond rupture.
- Tanner, Dennis D.,Plambeck, James A.,Reed, Darwin W.,Mojelski, Thomas W.
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p. 5177 - 5183
(2007/10/02)
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- Polar Radicals. 14. On the Mechanism of Trialkylstannane Reductions. Positive ρ Values for the Tri-n-butylstannane Reduction of Benzyl Halides. A Correlation with ?-
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The relative reactivities towards reduction by tri-n-butylstannane of a series of substituted benzyl halides have been determined.The order of reactivity was shown to be I > Br > Cl, the same as that reported for alkyl halide reductions.Under the reaction conditions (90 deg C, benzene as solvent, benzoyl peroxide initiation), both aralkyl and alkyl fluorides were shown to be completely unreactive.Activation energies were estimated for the direct abstraction of halogen by tri-n-butyl radicals, and on the basis of these estimates all of the halogens would be predicted to readily undergo abstraction.To explain the non-reactivity of the fluorides several other mechanisms were considered: reversible tin radical addition to the halogen to form an intermediate with an expanded octet, and a free radical chain mechanism involving an electron-transfer reaction between the trialkyltin radical and the benzyl halide. The benzyl halide reductions showed excellent Hammett correlations with positive ρ values; all of these correlations were obtained using ?- substituent constants.The demonstration (the first ever reported) that ?- substituent constants correlate with the relative reactivities for reduction infers that bond breaking takes place in the transition state for the reaction.The magnitudes of the ρ values were not found, as were expected, to be in the inverse order of the relative reactivities: ρ for the iodides (+0.81), for the bromides (+0.17), and for the chlorides (+0.34).To explain the anomalously high value of ρ found for the iodide reduction, it was suggested that the benzyl iodides underwent reduction by a different mechanism than the chlorides and the bromides.The relative rates of reduction of the benzyl iodides in a more polar solvent than benzene, acetonitrile, showed decreased sensitivity to substituents, whereas the reduction of the bromides and chlorides was relatively insensitive to solvent effects.
- Blackburn, Edward V.,Tanner, Dennis D.
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p. 692 - 697
(2007/10/02)
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