- Isomerisation of 1,4-dichlorobenzene using highly acidic alkali chloroaluminate melts
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The isomerisation reaction of 1,4-dichlorobenzene leading to the thermodynamically favoured and technically desired 1,3-dichlorobenzene has been studied comparing highly acidic chloroaluminate melts with organic imidazolium and alkali metal ions. Interestingly, the inorganic melts show much higher reactivity and full recyclability if small AlCl3 losses are compensated and the reaction is carried out under slight HCl pressure. This journal is
- Messner,Schulz,Taccardi,Kuhlmann, Sven,Wasserscheid
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Read Online
- Photoredox-catalyzed reduction of halogenated arenes in water by amphiphilic polymeric nanoparticles
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The use of organic photoredox catalysts provides new ways to perform metal-free reactions controlled by light. While these reactions are usually performed in organic media, the application of these catalysts at ambient temperatures in aqueous media is of considerable interest. We here compare the activity of two established organic photoredox catalysts, one based on 10-phenylphenothiazine (PTH) and one based on an acridinium dye (ACR), in the light-activated dehalogenation of aromatic halides in pure water. Both PTH and ACR were covalently attached to amphiphilic polymers that are designed to form polymeric nanoparticles with hydrodynamic diameter DH ranging between 5 and 11 nm in aqueous solution. Due to the hydrophobic side groups that furnish the interior of these nanoparticles after hydrophobic collapse, water-insoluble reagents can gather within the nanoparticles at high local catalyst and substrate concentrations. We evaluated six different amphiphilic polymeric nanoparticles to assess the effect of polymer length, catalyst loading and nature of the catalyst (PTH or ACR) in the dechlorination of a range of aromatic chlorides. In addition, we investigate the selectivity of both catalysts for reducing different types of aryl-halogen bonds present in one molecule, as well as the activity of the catalysts for C-C cross-coupling reactions. We find that all polymer-based catalysts show high activity for the reduction of electron-poor aromatic compounds. For electron-rich compounds, the ACR-based catalyst is more effective than PTH. In the selective dehalogenation reactions, the order of bond stability is C-Cl > C-Br > C-I irrespective of the catalyst applied. All in all, both water-compatible systems show good activity in water, with ACR-based catalysts being slightly more efficient for more resilient substrates.
- Eisenreich, Fabian,Kuster, Tom H. R.,Palmans, Anja R. A.,van Krimpen, David
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supporting information
(2021/10/05)
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- Metal- and base-free synthesis of aryl bromides from arylhydrazines
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An efficient method was developed to synthesize brominated aromatic compounds from arylhydrazine hydrochlorides by using BBr3 in DMSO/CPME (cyclopentyl methyl ether) under air at 80 °C for 1 h without the use of bases or metal catalysts. In particular, this method could be carried out satisfactorily using electron-withdrawing groups to afford aryl bromides in a moderate to excellent yields.
- Phuc Tran, Dat,Nomoto, Akihiro,Mita, Soichiro,Dong, Chun-ping,Kodama, Shintaro,Mizuno, Takumi,Ogawa, Akiya
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supporting information
(2020/05/08)
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- PROCESS FOR THE PREPARATION OF ORGANIC BROMIDES
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The present invention provides a process for the preparation of organic bromides, by a radical bromodecarboxylation of carboxylic acids with a bromoisocyanurate.
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Paragraph 00139; 00144
(2017/07/28)
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- Stereoselective oxidation of alkanes with: M -CPBA as an oxidant and cobalt complex with isoindole-based ligands as catalysts
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Two complexes with isoindole-core ligands of general formula [M{C6H4C(NH2)NC(ONCMe2)2}2](NO3)2 (M = Co for 1 and M = Ni for 2) were studied as catalysts for the mild stereoselective alkane oxidation with m-chloroperbenzoic acid (m-CPBA) as an oxidant and cis-1,2-dimethylcyclohexane (cis-1,2-DMCH) as a main model substrate. Complex 1 disclosed a pronounced activity, with high retention of stereoconfiguration of substrates (>98% for cis-1,2-DMCH) and highest cis/trans ratio of tertiary alcohols (products) of 56, under mild conditions. The best achieved yields of tertiary cis-alcohols were of 13.7 and 50.5%, based on the substrate (cis-1,2-DMCH) and the oxidant (m-CPBA) respectively. Kinetic experiments, high bond and stereoselectivity parameters, kinetic isotope effect of 7.2(2) in the oxidation of cyclohexane, and incorporation of 18O from H218O support the involvement of CoIVO high-valent metal-oxo intermediates as main C-H attacking species.
- Nesterova, Oksana V.,Kopylovich, Maximilian N.,Nesterov, Dmytro S.
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p. 93756 - 93767
(2016/10/21)
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- Substd. photoisomerization arom. compd. method
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Isomerizing substituted aromatic compounds (I), comprises carrying out isomerization in the presence of a salt melt, which contains a metal compound (II) and at least one metal compound (III). Isomerizing substituted aromatic compounds of formula (Ar1-R n) (I) or their mixtures, comprises carrying out isomerization in the presence of a salt melt, which contains a metal compound of formula ([M1][X1] m 1) (II) and at least one metal compound of formula ([M2][X2] m 2) (III). Ar1 : n-valent aryl radical; R : halo, alkyl, fluoroalkyl, aryl, alkyl-aryl or amino; M1 : Al, Ga, In, Cu, Fe, Co or Ni; X1, X2 : halo, preferably Cl or Br; M2, m2 : alkaline earth metal or alkali metal, where M2 is preferably Li, Na, or K; m1 : Al, Ga, In, Fe(III), Co, Ni or Cu(II); and n : >= 2, preferably 2.
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Paragraph 0066
(2017/01/02)
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- Halogen exchange via a halogenation of diaryliodonium salts with cuprous halide
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An efficient halogenation reaction has been developed with diaryliodonium salts and cuprous halides. Various diaryliodonium salts 1 could perform the reaction with readily available CuBr or CuCl in CH3CN at 80°C, assembling bromoarenes or chloroarenes in up to 92% yields. This provides us a method for the transformation from iodoarenes to other haloarenes.
- Li, Jian,Liu, Li,Ding, Dong,Sun, Jiang-Tao
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p. 541 - 548
(2014/01/06)
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- Visible-light-induced photocatalytic reductive transformations of organohalides
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A photo opportunity: A visible-light-excited iridium catalyst delivers electrons from an amine to an organohalide. The electron transfer then induces reductive scission of the carbon-halogen bond, generating the corresponding alkyl, alkenyl, and aryl radical that can undergo cyclization and hydrodehalogenation reactions. Copyright
- Kim, Hyejin,Lee, Chulbom
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supporting information
p. 12303 - 12306
(2013/02/23)
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- Carboxylic acids as traceless directing groups for formal meta-selective direct arylation
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Without a trace: The first meta-selective direct C-H arylation that uses iodoarenes as coupling partners is reported (see scheme, EWG=electron- withdrawing group). This process utilizes carboxylic acid units as temporary directing groups that are cleaved during the reaction, leaving no trace in the resulting biaryl products.
- Cornella, Josep,Righi, Marika,Larrosa, Igor
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scheme or table
p. 9429 - 9432
(2011/11/06)
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- Gold-catalyzed halogenation of aromatics by N-halosuccinimides
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(Chemical Equation Presented) Golden bromination: A highly efficient and mild AuCl3-catalyzed bromination of aromatic rings with Nbromosuccinimide (NBS) has been developed. This method works with a low catalyst loading (down to 0.01 mol %) and can be combined with transition metal catalyzed transformations to deliver various aryl products.
- Mo, Fanyang,Yan, Jerry Mingtao,Qiu, Di,Li, Fei,Zhang, Yan,Wang, Jianbo
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scheme or table
p. 2028 - 2032
(2010/06/17)
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- The synthesis and crystal structure of new bis(3-chlorophenyl)-[5-methyl-1- (4-methylphenyl)-1,2,3-triazol-4-yl]-methanol
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The title compound bis(3-chlorophenyl)-[5-methyl-1-(4-methylphenyl)-1,2,3- triazol-4-yl]-methanol 8 has been synthesized and established by H NMR, IR and MS spectra and X-ray diffraction crystallography. Compound 8, C 23H29Cl2N3O, Mr = 424.31, crystallizes in the monoclinic space group P21/c with unit cell parameters a = 14.5402(6) A, b = 12.5888(5) A, c = 11.6510(5) A, α = 90°, β = 100.183°(2), γ = 90°, V = 2099.05(15) A3, Dx = 1.343 mg m-3 and Z = 4. The final R was 0.0514. The molecular conformation and packing is stabilized by interactions of intermolecular O1-H1...;N3′.
- Dong, Heng-Shan,Huo, Guo-Yong
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scheme or table
p. 28 - 31
(2009/06/06)
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- Silver-catalysed protodecarboxylation of ortho-substituted benzoic acids
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Catalytic amounts of Ag(i) salts in DMSO have been found to promote the protodecarboxylation of a wide variety of ortho-substituted benzoic acids under mild conditions and in excellent yields, highlighting a possible role for silver in decarboxylative cross-couplings. The Royal Society of Chemistry 2009.
- Cornella, Josep,Sanchez, Carolina,Banawa, David,Larrosa, Igor
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supporting information; experimental part
p. 7176 - 7178
(2010/03/25)
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- Relative basicities of ortho-, meta-, and para-substituted aryllithiums
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(Chemical Equation Presented) The relative basicities of aryllithiums bearing methoxy, chlorine, fluorine, trifluoromethyl and trifluoromethoxy substituents at the ortho, meta, and para positions have been assessed. To this end, two aryllithiums of compar
- Gorecka-Kobylinska, Joanna,Schlosser, Manfred
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experimental part
p. 222 - 229
(2009/04/11)
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- Catalytic Sandmeyer bromination
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An efficient catalyst system for Sandmeyer bromination is proposed. Aryl bromides and dibromides can be obtained with excellent yield by this synthetic protocol. Georg Thieme Verlag Stuttgart.
- Beletskaya, Irina P.,Sigeev, Alexander S.,Peregudov, Alexander S.,Petrovskii, Pavel V.
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p. 2534 - 2538
(2008/03/13)
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- Regioselective halogen-metal exchange reaction of 3-substituted 1,2-dibromo arenes: The synthesis of 2-substituted 5-bromobenzoic acids
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Regioselective halogen-metal exchange reactions using isopropylmagnesium chloride were carried out on 3-substituted 1,2-dibromo arenes. Eleven examples are given. Georg Thieme Verlag Stuttgart.
- Menzel, Karsten,Dimichele, Lisa,Mills, Paul,Frantz, Doug E.,Nelson, Todd D.,Kress, Michael H.
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p. 1948 - 1952
(2008/02/08)
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- The conversion of phenols to the corresponding aryl halides under mild conditions
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Mild, novel procedures have been developed for the syntheses of aryl halides from the corresponding phenols in modest to good yields via boronate ester intermediates.
- Thompson, Alicia L. S.,Kabalka, George W.,Akula, Murthy R.,Huffman, John W.
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p. 547 - 550
(2007/10/03)
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- Halodediazoniations of dry arenediazonium o-benzenedisulfonimides in the presence or absence of an electron transfer catalyst. Easy general procedures to prepare aryl chlorides, bromides, and iodides
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The paper reports the results of a wide study aimed at preparing aryl chlorides 3 (19 examples), bromides 4 (19 examples), and iodides 5 (9 examples) by halodediazoniation of dry arenediazonium o-benzenedisulfonimides 1 with tetraalkylammonium halides 2. The reactions were carried out in anhydrous acetonitrile at room temperature (~20 °C) in the presence of copper powder and at 60 °C or room temperature without the catalyst. In optimal conditions the yields were from good to excellent (60 reactions, 61- 94% yield), with only a few exceptions (8 reactions, 51-55% yield). A good amount of the o-benzenedisulfonimide (7) was always recovered from the reactions and could then be reused to prepare salts 1. An interesting aspect of this research is the surprising role of the anion of o- benzenedisulfonimide (9) as an electron transfer agent.
- Barbero,Degani,Dughera,Fochi
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p. 3448 - 3453
(2007/10/03)
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- Arenediazonium tetrachlorocuprates(ii). Modification of the meerwein and sandmeyer reactions
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In the copper-catalysed reactions of arenediazonium chlorides with unsaturated compounds arenediazonium tetrachlorocuprates(II) are formed as intermediates. A general method of preparation of these complexed diazonium salts is described. In polar solvents these salts undergo chlorinative dediazoniation to give chloroarenes in high yield. The reaction of an arenediazonium tetrachlorocuprate(II) with an activated alkene results in the same products as the Meerwein reaction. A radical cation mechanism for this reaction is proposed.
- Obushak, Mykola D.,Lyakhovych, Mykhaylo B.,Ganushchak, Mykola I.
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p. 9567 - 9570
(2007/10/03)
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- Mild preparation of haloarenes by ipso-substitution of arylboronic acids with N-halosuccinimides
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Aryl and heteroaryl boronic acids react with N-iodosuccinimide and N-bromosuccinimide to give the corresponding iodo-and bromo- arenes in good to excellent yields. The reaction is usually highly regioselective and yields only the ipso-substituted product. Esters of arylboronic acids react similarly, but less readily.
- Thiebes, Christoph,Prakash, G. K. Surya,Petasis, Nicos A.,Olah, George A.
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p. 141 - 142
(2007/10/03)
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- Process for preparing [R-(R*,R*)]-5-(3-chlorophenyl)-3-[2-(3,4-dimethoxylphenyl)-1-methyl-ethyl]-oxazolidin-2-one
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The present invention relates to a process for preparing [R-(R*,R*)]-5-(3-chlorophenyl)-3-[2-(3,4-dimethoxyphenyl)-1-methyl-ethyl]-oxazolidin-2-one of Formula (1), characterized in that said process comprises the step of reacting (R)-3, 4-methoxy-amphetamine of Formula (3), with (R)-3-chloro-mandelic acid, of Formula (9): STR1
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- Radical versus "oxenoid" oxygen insertion mechanism in the oxidation of alkanes and alcohols by aromatic peracids. New synthetic developments
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Evidences concerning a novel free-radical mechanism for the oxidation of alkanes by aromatic peracids are reported. The mechanism involves hydrogen abstraction from the OH group of peracids by an aroyloxyl radical; the acylperoxyl radical thus generated is responsible for the selective oxidation. The reaction is affected by the presence of oxygen and it is inhibited by TEMPO and by solvents forming hydrogen bonds with peracids. A more simple and effective synthetic procedure has been developed, on the basis of the autoxidation of aliphatic and aromatic aldehydes in the presence of alkanes. It is also shown that the previously reported inertness of alcohols toward peracids must be ascribed to solvent effects, due to the formation of hydrogen bonds; in suitable solvents alcohol oxidation smoothly occurs.
- Bravo, Anna,Bjorsvik, Hans-Rene,Fontana, Francesca,Minisci, Francesco,Serri, Anna
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p. 9409 - 9416
(2007/10/03)
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- Exchange of halogens between aromatic compounds in the presence of Cu-HZSM-5 zeolite
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The reactions between various haloaromatics in binary mixtures which were approximately equimolar, were studied in gas-phase (673 K, atmospheric: pressure) in the presence of a 2 wt % Cu-HZSM-5 zeolite. The exchange of halogens (ipso substitution) between the two compounds was assumed to occur either through a radical mechanism involving an electron transfer between an atom of copper (I) and one aromatic molecule or through a nucleophilic substitution involving arylcopper complexes as intermediates.
- Imhaoulne,Imhaoulene,Vivier,Guisnet,Petot,Perot,Gubelmann
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p. 12913 - 12922
(2007/10/02)
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- Photochemical Bromination of Simple Arenes
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Photochemical bromination of benzene, fluorobenzene, chlorobenzene, t-butylbenzene, α,α,α-trifluorotoluene, and (in tetrachloromethane) biphenyl and naphthalene gives substitution products and adducts such as 1,2,3,4,5,6-hexabromocyclohexane (1).The decomposition of (1) and of the analogous chlorobenzene adduct (3) under photochemical conditions gives the parent arene, the monobrominated halogenobenzene, and bromine which may be scavenged by toluene to give benzyl bromide or by benzene to give bromobenzene and dibromobenzenes.Addition is a kinetically controlled process, so that the mechanism of formation of these aryl bromides must be largely through the reversible formation of these adducts.This is consistent with the unusual orientation of apparent attack by bromine upon the arene substrates, since the relative amounts of the isomeric aryl bromides is a consequence of the relative stabilities and ease of elimination of HBr and Br2 from a family of adducts. The range of isomer distribution found within the reaction of each arene with bromine is consistent with two competing processes involved in the formation of the aryl bromides; one of these might by the direct homolytic substitution by bromine atoms upon the arene.
- Bolton, Roger,Bhangar, Muhammad Iqbal,Williams, Gareth H.
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p. 893 - 896
(2007/10/02)
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- Photochemical Dehalogenation of Polyhalobenzenes. I. Survey of the Reactivity in Hexane Solution
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Photochemical dechlorinations and debrominations of C6HnX6-n (X = Cl, Br) isomers were carried out in hexane.The products and residual reactant were determined quantitatively by means of gas chromatography.From these experiments, the relative rates of dehalogenation were obtained.The different rates among unequivalent sites in a molecule were interpreted by the effect of steric acceleration by the neighboring halogen atom(s).The reactivity of the halogen atom in polyhalobenzene towards photochemical elimination reaction is dependent both on its position in the molecule when compared among isomers and on the number of halogen atoms in a molecule when compared among polyhalobenzenes of various degrees of substitution.The latter effect is more predominant in the series of polybromobenzenes.
- Nakada, Masahiro,Fukushi, Sachio,Nishiyama, Hideaki,Okubo, Keiji,Kume, Kotaro,et al.
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p. 2447 - 2451
(2007/10/02)
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- Reduction of Aryldiazonium Salts to Arenes
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Aryldiazonium fluoroborates are smoothly reduced to the corresponding hydrocarbon derivatives by warming with DMF.When the amine has an electron donating substituent, the reaction proceeds at 65 deg C.When the amine has electron withdrawing substituents, the reaction proceeds rapidly at 25-45 deg C.Deamination of 2,4,6-trichlorobenzenediazonium fluoroborate with tetramethylurea gives acetaldehyde as an unexpected product together with 2,4,6-trichlorobenzene.The amines can also be deaminated with DMF without separation of the diazonium salt in aqueous or non-aqueous medium.
- Lahoti, R. J.,Parameswaran, V.,Wagle, D. R.
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p. 767 - 769
(2007/10/02)
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