- Homogeneous catalysis and selectivity in electrochemistry
-
The relationship between homogeneous catalysis and electrochemistry is examined in light of two examples based on our work concerning (a) catalyst activation, regarding selective electrochemical C-H oxidation with RuIII/RuIV mediation, and (b) catalyst suppression, regarding controlling selectivity in electrochemical aromatic chlorination. The first example (a) deals with the role of catalysis at the working electrode. The electrochemical (EC) oxidation of specific hydrocarbons such as tetralin and indane is performed using tris(acetonitrile)ruthenium trichloride (Ru(CH3CN)3Cl3) as a mediator. The role of this mediator in the oxidation of tetralin has been reported. This homogeneous C-H activation by electron transfer (ET) is accompanied by the redox transitions of the mediator in the course of the catalytic oxidation, and these are the main points of interest here. Additional studies with a rotating ring disk electrode (RRDE) provided a follow-up of creation and recovery of RuIII/RuII and RuIII/RuIV species in the process. Using electrochemistry linked with electrospray ionization mass spectrometry (EC/ESI-MS) gave additional information on the structure of the reduced and oxidized forms of Ru(CH3CN)3Cl3 and the effect of water in the solvent on their lifetimes. The second example (b) of electrochlorination has been reported elsewhere and is brought up as complementary remarks. Aromatic electrophilic chlorination of 1,4-dimethoxy-2-tertbutylbenzene is autocatalyzed and unselective. The EC procedure provides a simple means to inhibit the catalytic runaway reaction. This example shows how the counter electrode affects catalysis and selectivity. (Figure Presented)
- Michman, Michael,Appelbaum, Lina,Gun, Jenny,Modestov, Alexander D.,Lev, Ovadia
-
-
Read Online
- Simple and efficient chlorination and bromination of aromatic compounds with aqueous TBHP (or H2O2) and a hydrohalic acid
-
A combination of aqueous tert-butylhydroperoxide (70%) or hydrogen peroxide (34%) and a hydrohalic acid was found effective in chlorination and bromination of aromatic compounds.
- Barhate, Nivrutti B.,Gajare, Anil S.,Wakharkar, Radhika D.,Bedekar, Ashutosh V.
-
-
Read Online
- Efficient halogenation synthesis method of aryl halide
-
The invention discloses an efficient halogenation synthesis method of aryl halide. The method comprises the following step: in the presence of a catalyst (sulfoxide or oxynitride), a halogenation reagent and a solvent, carrying out a halogenation reaction on an aromatic ring compound to obtain the aryl halide. According to the present invention, in the presence of a catalyst (sulfoxide or nitrogenoxide), a halogenation reagent and a solvent, the aromatic ring is subjected to an efficient halogenation reaction, such that the very useful aryl halide can be obtained with high activity and high selectivity; and by adopting the method disclosed by the invention, aryl halides can be efficiently synthesized, and the method has a wide application prospect in actual production.
- -
-
Paragraph 0184-0186
(2021/03/31)
-
- Method for synthesizing 4-chloro-2, 5-dimethoxynitrobenzene by using microreactor
-
The invention relates to a method for synthesizing 4-chloro-2, 3, 5-tetramethylpiperidine by using a microreactor. According to the method, intermediate 2, 5-dimethoxychlorobenzene of 4-chloro-2, 5-dimethoxynitrobenzene and nitric acid are used as raw materials, 4-chloro-2, 5-dimethoxynitrobenzene is synthesized through the microreactor, in the reaction process, the mass fraction of nitric acid is50%-95%, and the mass fraction of a 2, 5-dimethoxychlorobenzene solution is 15%-50%; the feeding molar ratio of nitric acid to 2, 5-dimethoxychlorobenzene is (1.0-1.5): 1, the reaction temperature is50-85 DEG C, the feeding temperature is not higher than 50 DEG C, and the reaction retention time is 30-120 seconds. According to the method, on one hand, the process conditions such as the materialratio and the reaction temperature are accurately controlled, the dosage of nitric acid is reduced, the method is environmentally friendly, the conversion rate of 2, 5-dimethoxychlorobenzene reaches 99.98%, and the yield of 4-chloro-2, 5-dimethoxynitrobenzene reaches 99.5% or above; on the other hand, the key problems of corrosivity of nitric acid, difficulty in controlling the reaction temperature, poor mass and heat transfer effect, poor safety and the like in the conventional synthesis process are solved, and the reaction risk is low; strong operability.
- -
-
Paragraph 0021-0028
(2020/12/05)
-
- Preparation method of 2,5-dimethoxychlorobenzene
-
The invention relates to a preparation method of 2,5-dimethoxychlorobenzene, which comprises the following steps: 1) one-pot oxidatiion and chlorination: dissolving phenol in a solvent, putting a formed solution into a high-pressure reaction kettle, adding a copper salt catalyst, conducting stirring to conduct reaction at a temperature range of room temperature to 50 DEG C under the oxygen pressure of 0.5-3 MPa, introducing 0.1-2 MPa dry HCl gas into the solution after the reaction is completed, and conducting stirring to conduct reaction at room temperature, and after the reaction is completed, conducting decompressing and rectifying to obtain a 2-chlorohydroquinone intermediate; and 2) methylation: adding 2-chlorohydroquinone into a high-pressure reaction kettle, conducting dissolving, introducing 0.1-2MPa of chloromethane gas under an alkaline condition, maintaining the pressure, conducting reacting at 50-120 DEG C until the raw materials are completely consumed, conducting filtering and desolventizing, and carrying out reduced pressure distillation to obtain the product 2,5-dimethoxychlorobenzene. Compared with a traditional preparation method, the method has the advantages ofless emission of three wastes, low cost, environmental friendliness and the like.
- -
-
Paragraph 0029; 0032-0033; 0038-0042
(2020/12/15)
-
- In situ Generation of Hypervalent Iodine Reagents for the Electrophilic Chlorination of Arenes
-
Efficient metal-free methods for the electrophilic chlorination of arenes using PIFA and simple chlorine sources are reported. The in situ formation of PhI(Cl)OCOCF3 from PIFA and KCl is proposed, which resulted in a chlorinating species for moderately activated arenes. Moreover, the in situ formation of PhICl2 from PIFA and TMSCl resulted in an excellent approach for the chlorination of a great variety of arenes (20 examples) in high yields, even when working on a multigram scale.
- Granados, Albert,Jia, Zhiyu,del Olmo, Marc,Vallribera, Adelina
-
p. 2812 - 2818
(2019/04/08)
-
- Preparation, structure, and oxidative reactivity of (dichloroiodo)pyridines: Recyclable hypervalent iodine reagents
-
New pyridine-based hypervalent iodine reagents, (dichloroiodo)pyridines, were prepared by chlorination of 2-, 3-, or 4-iodopyridines with NaOCl-HCl at room temperature. Structures of 2-(dichloroiodo)pyridine and 2-(dichloroiodo)-3-propoxypyridine were established by X-ray crystallography. The new (dichloroiodo)pyridines can be used as efficient reagents for oxidation of alcohols to carbonyl compounds and also as chlorinating reagents. The reduced form of the reagents such as 2-iodo-3-propoxypyridine, can be recovered from the reaction mixture in good yields by an acid-base liquid-liquid biphasic protocol.
- Yoshimura, Akira,Nguyen, Khiem C.,Nemykin, Victor N.,Zhdankin, Viktor V.
-
-
- Aromatic Monochlorination Photosensitized by DDQ with Hydrogen Chloride under Visible-Light Irradiation
-
Photochlorination of aromatic substrates by hydrogen chloride with 2,3-dichloro-5,6-cyano-p-benzoquinone (DDQ) occurs efficiently to produce the corresponding monochlorinated products selectively under visible-light irradiation. The yields for the chlorination of phenol were 70 % and 18 % for p- and o-chlorophenol, respectively, without formation of further chlorinated products. The photoinduced chlorination is initiated by electron transfer from Cl- to the triplet excited state of DDQ. The radical intermediates involved in the photochemical reaction have been detected by time-resolved transient absorption measurements.
- Ohkubo, Kei,Fujimoto, Atsushi,Fukuzumi, Shunichi
-
p. 996 - 999
(2016/04/20)
-
- Electrophilic aryl-halogenation using N-halosuccinimides under ball-milling
-
We report here a methodology of chemo- and regio-selective aryl bromination and iodination using respective N-halosuccinimides at room temperature in the absence of any solvents, catalyst/additives under ball-milling condition. However, for chlorination ceric ammonium nitrate was used as additive. The coupled product succinimide, produced from the reactions, was recycled via regeneration of NBS. This methodology works with the electron-donor substituted or unsubstituted arenes.
- Bose, Anima,Mal, Prasenjit
-
p. 2154 - 2156
(2015/03/18)
-
- Electrophilic aryl-halogenation using N-halosuccinimides under ball-milling
-
We report here a methodology of chemo- and regio-selective aryl bromination and iodination using respective N-halosuccinimides at room temperature in the absence of any solvents, catalyst/additives under ball-milling condition. However, for chlorination ceric ammonium nitrate was used as additive. The coupled product succinimide, produced from the reactions, was recycled via regeneration of NBS. This methodology works with the electron-donor substituted or unsubstituted arenes.
- Bose, Anima,Mal, Prasenjit
-
supporting information
p. 2154 - 2156
(2014/04/03)
-
- An efficient monochlorination of electron-rich aromatic compounds catalysed by ammonium iodide
-
An efficient monochlorination of electron-rich aromatic compounds is developed, with which a series of regioselective monochlorinated products are obtained in good yields. In the reaction, ammonium iodide is used as catalyst and m-chloroperbenzoic acid is used as the terminal oxidant. Ammonium iodide is first oxidised to hypoiodous acid by m-chloroperbenzoic acid. The in situ generated active iodine species then reacts with the aromatic compound to form the active hypervalent iodine intermediate in two steps and this reacts with lithium chloride to afford eventually the chlorinated compounds.
- Min, Zhu,Ying-Guo, Fang
-
p. 197 - 199
(2014/05/06)
-
- Halogenated volatiles from the fungus Geniculosporium and the actinomycete Streptomyces chartreusis
-
Two unidentified chlorinated volatiles X and Y were detected in headspace extracts of the fungus Geniculosporium. Their mass spectra pointed to the structures of a chlorodimethoxybenzene for X and a dichlorodimethoxybenzene for Y. The mass spectra of some constitutional isomers for X and Y were included in our databases and proved to be very similar, thus preventing a full structural assignment. For unambiguous structure elucidation all possible constitutional isomers for X and Y were obtained by synthesis or from commercial suppliers. Comparison of mass spectra and GC retention times rigorously established the structures of the two chlorinated volatiles. Chlorinated volatiles are not very widespread, but brominated or even iodinated volatiles are even more rare. Surprisingly, headspace extracts from Streptomyces chartreusis contained methyl 2-iodobenzoate, a new natural product that adds to the small family of iodinated natural products.
- Wang, Tao,Rabe, Patrick,Citron, Christian A.,Dickschat, Jeroen S.
-
supporting information
p. 2767 - 2777
(2014/01/06)
-
- An efficient chlorination of aromatic compounds using a catalytic amount of iodobenzene
-
An efficient method was developed for chlorination of aromatic compounds with electron-donating groups using iodobenzene as the catalyst and m-chloroperbenzoic acid as the terminal oxidant in the presence of 4-methylbenzenesulfonic acid in THF at room temperature for 24 h, and a series of the monochlorinated compounds was obtained in good yields. In this protocol, the catalyst iodobenzene was first oxidized into the hypervalent iodine intermediate, which then treated with lithium chloride and finally reacted with aromatic compounds to form the chlorinated compounds.
- Li, Ting-Ting,Xu, Cui,Xiang, Chang-Bin,Yan, Jie
-
p. 535 - 538
(2013/07/27)
-
- Bis- N -heterocyclic carbene palladium(IV) tetrachloride complexes: Synthesis, reactivity, and mechanisms of direct chlorinations and oxidations of organic substrates
-
This Article describes the preparation and isolation of novel octahedral CH2-bridged bis-(N-heterocyclic carbene)palladium(IV) tetrachlorides of the general formula LPdIVCl4 [L = (NHC)CH 2(NHC)] from LPdIICl2 and Cl2. In intermolecular, nonchelation-controlled transformations LPdIVCl 4 reacted with alkenes and alkynes to 1,2-dichlorination adducts. Aromatic, benzylic, and aliphatic C-H bonds were converted into C-Cl bonds. Detailed mechanistic investigations in the dichlorinations of alkenes were conducted on the 18VE PdIV complex. Positive solvent effects as well as kinetic measurements probing the impact of cyclohexene and chloride concentrations on the rate of alkene chlorination support a PdIV-Cl ionization in the first step. Product stereochemistry and product distributions from various alkenes also support Cl+-transfer from the pentacoordinated PdIV-intermediate LPdIVCl 3+ to olefins. 1-Hexene/3-hexene competition experiments rule out both the formation of π-complexes along the reaction coordinate as well as in situ generated Cl2 from a reductive elimination process. Instead, a ligand-mediated direct Cl+-transfer from LPd IVCl3+ to the π-system is likely to occur. Similarly, C-H bond chlorinations proceed via an electrophilic process with in situ formed LPdIVCl3+. The presence of a large excess of added Cl- slows cyclohexene chlorination while the presence of stoichiometric amounts of chloride accelerates both PdIV-Cl ionization and Cl+-transfer from LPdIVCl3 +. 1H NMR titrations, T1 relaxation time measurements, binding isotherms, and Job plot analysis point to the formation of a trifurcated Cl-...H-C bond in the NHC-ligand periphery as a supramolecular cause for the accelerated chemical events involving the metal center.
- McCall, A. Scott,Wang, Hongwang,Desper, John M.,Kraft, Stefan
-
supporting information; experimental part
p. 1832 - 1848
(2011/04/15)
-
- Grindstone chemistry: (Diacetoxyiodo)benzene-mediated oxidative nuclear halogenation of arenes using NaCl, NaBr or I2
-
A technique of "Grindstone chemistry" is applied to the solvent-free halogenation of arenes with NaCl, NaBr or I2 using (diacetoxyiodo)benzene as the oxidant. Improved yields and higher purities of the products are observed compared with those from established methods.
- Karade,Tiwari,Huple,Siddiqui
-
p. 366 - 368
(2007/10/03)
-
- Halogenation of Aromatic Compounds by N-chloro-, N-bromo-, and N-iodosuccinimide
-
An efficient and mild method for the halogenation of aromatic compounds using N-chloro-, N-bromo-, and N-iodosuccinimide in the presence of NH 4NO3 or FeCl3 in acetonitrile was developed.
- Tanemura, Kiyoshi,Suzuki, Tsuneo,Nishida, Yoko,Satsumabayashi, Koko,Horaguchi, Takaaki
-
p. 932 - 933
(2007/10/03)
-
- A facile synthesis of 1,4-dialkoxy-2,5-diiodobenzenes: reaction of dialkoxybenzenes with iodine monochloride in alcoholic solvents
-
A facile synthesis of 1,4-dialkoxy-2,5-diiodobenzenes via diiodination of the corresponding dialkoxybenzenes with iodine monochloride has been developed. Employment of ah alcoholic solvent as a reaction medium is crucial for attaining a high yield; the reaction in a nonalcoholic solvent usually resulted in a poor yield. The diiodobenzene derivatives are useful intermediates in the synthesis of such advanced materiais as soluble phenylenevinylene polymers anal dialkoxy derivatives of 7,7,8,8-tetracyanoquinodimethane.
- Wariishi, Koji,Morishima, Sin-Ichi,Inagaki, Yoshio
-
-
- Novel process for generating useful electrophiles from common anions using Selectfluor fluorination agent
-
In the present work, the electrophile equivalents C1+, Br+, SCN+, and NO2+ are generated from their respective sodium, potassium, and in some cases ammonium salts (M+X-) by reaction with Selectfluor electrophilic fluorination agent in acetonitrile solution at room temperature. These generated electrophilic species subsequently react in situ with a variety of aromatic substrates containing one or more substituent groups including H, F, C1, CH3, COOH, C(O)CH3, NO2, and OR′ and NR′R″ where R′ and R″ are H or CH3. The resulting substitution products are, in most cases, isolable as pure compounds in high yield. Variations in the process include the use of other anions, electrophilic fluorination agents, and solvents.
- Syvret, Robert G.,Butt, Kathleen M.,Nguyen, Tung P.,Bulleck, Victoria L.,Rieth, Ryan D.
-
p. 4487 - 4493
(2007/10/03)
-
- A simple and practical halogenation of activated arenes using potassium halide and oxone in water-acetonitrile medium
-
A simple and practical halogenation of activated arenes using a reagent combination of potassium halide and oxone in water-acetonitrile medium is presented. The halogenated products were obtained with good yields and in high purity.
- Tamhankar,Desai,Mane,Wadgaonkar,Bedekar
-
p. 2021 - 2027
(2007/10/03)
-
- Aromatic iodination: A new investigation on the nature of the mechanism
-
Following a suggestion by the late Lennart Eberson, we have employed the ICl-HFP (HFP being hexafluoropropan-2-ol) system in iodination reactions, and found unambiguous evidence for the occurrence of an ET-mechanism of halogenation. The evidence is based on the use of 'intelligent' substrates, which make it possible to fix the boundaries between the occurrence of an ET-mechanism and of a conventional polar mechanism. In an 'intelligent' substrate, in fact, the nature of the product(s) changes significantly depending on the operating mechanism. The ICl-HFP combination is instrumental to the onset of a one-electron oxidation with electron-rich substrates, followed by halogenation. The most prominent example is that of the electron-rich substrate durene (1,2,4,5-tetramethylbenzene, DUR), when compared to mesitylene (1,3,5-trimethylbenzene, MES): with a 'conventional' iodination system (i.e., I2/ Ag+) and in common solvents, where the polar mechanism holds, durene is less reactive (kMES/kDUR = 46 ± 3), but becomes more reactive (kMES/kDUR = 0.23) in HFP with ICl, where the ET-mechanism takes over. Other substrates also support the onset of ET-pathways in HFP. Finally, a preliminary survey of a biohalogenation reaction induced by laccase indicates the modest occurrence of a polar process of iodination with a few substrates.
- Fabbrini, Maura,Galli, Carlo,Gentili, Patrizia,Macchitella, Daniele,Petride, Horia
-
p. 1516 - 1521
(2007/10/03)
-
- Simple and practical halogenation of arenes, alkenes and alkynes with hydrohalic acid/H2O2 or TBHP)
-
A simple protocol for the halogenation of arenes utilizing a combination of aqueous hydrogen peroxide (34 %) or tert-butylhydroperoxide (70 %) and hydrohalic acid is presented. A similar procure of oxyhalogenation involving the in situ generation of positive halogen reagents is applied for the preparation of vicinal trans-dibromoalkanes and dichloroalkanes from alkenes. The reaction of alkenes with a combination of hydrochloric acid and hydrobromic acid with hydrogen peroxide gave a mixture of 1-bromo 2-chloro alkanes and 1,2-dibromoalkanes: Oxidative bromination of alkynes is also reported under similar conditions.
- Barhate, Nivrutti B.,Gajare, Anil S.,Wakharkar, Radhika D.,Bedekar, Ashutosh V.
-
p. 11127 - 11142
(2007/10/03)
-
- Radical cation mechanism of aromatic halogenation by halogens or iodine chloride in 1,1,1,3,3,3-hexafluoropropan-2-ol
-
The reaction between aromatic compounds ArH and halogenating agents, viz. iodine chloride, chlorine, bromine, iodine, N-bromosuccinimide and N-chlorosuccinimide, in 1,1,1,3,3,3-hexafluoropropan-2-ol (HFP) has been investigated. EPR spectroscopy established that these reagents produced persistent radical cations ArH.+ from ArH with Erev(ArH.+/ArH) up to 1.6, 1.3, 1.4, 1.1, 1.5 and 1.2 V vs. Ag/AgCl, respectively. Cyclic voltammetry of the halogenating species shows that no effect of complexation with halide ion is observed in HFP, as expected from its capacity to drastically attenuate nucleophilic reactivity, and that the cathodic peak potentials Epc (referenced to the internal ferricinium/ferrocene redox couple) are significantly or remarkably higher in HFP than in acetonitrile. For N-bromosuccinimide, the difference amounts to almost 1 V. The persistency of the radical cations in HFP is such that the kinetics of reactions between a halogenating agent, such as iodine chloride or bromine, and ArH, such as 1,4-dimethoxybenzene [Erev(ArH.+/ArH) = 1.50 V vs. Ag/AgCl] or 1,4-dimethoxy-2,3-dimethylbenzene [Erev(ArH.+/ArH) = 1.16 V], have been studied at room temperature over periods of hours. The initial concentration of the radical cation corresponds to yields in the range of 40-100%, depending on the reaction conditions. It is thus possible to establish that the radical cation decays via two pathways, one being the well known oxidative substitution reaction with halide ion. The second mechanism involves halogen atom transfer from the halogenating agent (Cl atom from ICl, Br atom from bromine). In the case of the radical cation of 1,4-dimethoxy-2,3-dimethylbenzene reacting with bromide ion or bromine, the latter reaction is >102 times faster.
- Eberson, Lennart,Hartshorn, Michael P.,Radner, Finn,Persson, Ola
-
-
- Selective aromatic chlorination of activated arenes with sodium chlorite, (salen)manganese(III) complex, and alumina in dichloromethane
-
The reaction of alkyl phenyl ethers with sodium chlorite in dichloromethane in the presence of a (salen)manganese(III) complex and alumina preloaded with a small amount of water afforded monochlorination products with unusually high para selectivities under mild conditions. The NaClO2-based biphasic system can also be successfully used for the regioselective monochlorination of substituted anisoles and polymethoxybenzenes.
- Hirano,Yakabe,Monobe,Morimoto
-
p. 1905 - 1912
(2007/10/03)
-
- Cation Radicals as Intermediates in Aromatic Halogenation with Iodine Monochloride: Solvent and Salt Effects on the Competition between Chlorination and Iodination
-
Three distinct classes of substitutional reactivity can be discerned in the halogenation of a series of methyl-substituted methoxybenzenes (ArH) with iodine monochloride (ICl), namely, exclusive iodination, exclusive chlorination, and mixed iodination/chlorination.Spectral studies establish the prior formation of the charge-transfer complex which suffers electron transfer to afford the reactive triad .+,I.,Cl(-)> according to Scheme 1.Separate reactivity studies show that chlorination and iodination can result from the quenching of the aromatic cation radical by chloride and iodine (atom), respectively.Iodination versus chlorination thus represents the competition between radical-pair and ion-pair collapse from the reactive triad, and it is predictably modulated by solvent polarity and added salt.
- Hubig, S. M.,Jung, W.,Kochi, J. K.
-
p. 6233 - 6244
(2007/10/02)
-
- 13C and 17O NMR Study of Methoxy Groups in Chlorinated Di- and Trimethoxybenzenes
-
13C and 17O NMR data for the methoxy groups in isomeric 1,2-, 1,3- and 1,4-dimethoxybenzenes, 1,2,3-trimethoxybenzenes and most of their chlorinated derivatives and some related brominated compounds were measured for CDCl3 solutions.The 17O NMR chemical shifts show up to 60 ppm dispersion.Comparison between the compounds with and without adjacent chlorine atoms (2,6-di- and 2,4,6-trisubstitution) also showed a clear methoxy carbon chemical shift change.The number and position of the chlorine atoms in the aromatic ring give small but observable effects on the 17O NMR chemical shifts of the methoxy group if it is coplanar with the aromatic plane.Similarly, the degree and nature of the substitution have a minor effect (about 1 Hz) on the 1J(CH) direct coupling values.
- Knuutinen, J.,Kolehmainen, E.
-
p. 315 - 317
(2007/10/02)
-
- Facile Synthesis of Chloro-substituted Aromatic Ethers by Use of Benzyltrimethylammonium Tetrachloroiodate
-
The reaction of aromatic ethers with a calculated amount of benzyltrimethylammonium tetrachloroiodate in acetic acid (or dichloromethane) under mild conditions gave, selectively, the objective chloro-substituted aromatic ethers in good yields.
- Kajigaeshi, Shoji,Shinmasu, Youichi,Fujisaki, Shizuo,Kakinami, Takaaki
-
p. 415 - 418
(2007/10/02)
-
- Highly Selective Aromatic Chlorination. Part 3. Kinetics and Mechanism of Chlorination of Electron-rich Aromatic Compounds by N-Chloroamines in Acidic Solution
-
The highly selective chlorination of electron-rich aromatic compounds with N-chloroamines in trifluoroacetic acid (TFA) is first order in both the aromatic substrate and the chlorinating agent.Kinetic and competitive kinetic studies show that electron-donating substituents on the substrate and electron-withdrawing substituents on the N-chloroamine have a marked rate-enhancing effect.Two mechanisms that fit the experimentally observed kinetics and that account for the high selectivity for 4-chlorination in terms of an electronic effect are proposed, namely an arenium-ion mechanism and an electron-transfer chain reaction.Evidence from chemical trapping experiments and from other studies suggest that for the majority of the substrates the chlorination proceeds by the arenium ion mechanism.However, for substrates, such as 1,4-dimethoxybenzene, that are very susceptible to one-electron oxidation chlorination may proceed at least in part by the electron-transfer chain reaction.
- Smith, John R. Lindsay,McKeer, Linda C.,Taylor, Jonathan M.
-
p. 1529 - 1536
(2007/10/02)
-
- Highly Selective Aromatic Chlorinations. Part 2. The Chlorination of Substituted Phenols, Anisoles, Anilines, and Related Compounds with N-Chloroamines in Acidic Solution
-
Phenols, anisoles, anilines, and related compounds are chlorinated in trifluoroacetic acid at room temperature by N-chlorodialkylamines and N-chlorotrialkylammonium salts.With monsubstituted compounds and their 2- and 3-substituted derivatives the reaction occurs efficiently and selectively at the 4-position.The reactivity of these substrates and the selectivity of their chlorinations are determined by electronic rather than steric effects of the substituent.Blocking the reaction with a substituent at the 4-position generally leads to only poor or moderate yields of the 2-chlorinated product.Evidence for radical and cation radical intermediates has been obtained in the reactions of some of the 4-substituted reactants and the mechanism of chlorination is discussed in the light of these findings.The reactions of selected substrates have been scaled up to give laboratory syntheses.
- Smith, John R. Lindsay,McKeer, Linda C.,Taylor, Jonathan M.
-
p. 385 - 392
(2007/10/02)
-
- HIGH SITE-SELECTIVITY IN THE CHLORINATION OF ELECTRON-RICH AROMATIC COMPOUNDS BY N-CHLORAMMONIUM SALTS.
-
N-Chlorammonium salts are efficient and very site-selective monochlorinating agents for electron-rich aromatic compounds.
- Smith, John R. Lindsay,McKeer, Linda C.
-
p. 3117 - 3120
(2007/10/02)
-