- R4NHal/NOHSO4: A Usable System for Halogenation of Isoxazoles, Pyrazoles, and beyond
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A new convenient and versatile halogenating system (R4NHal/NOHSO4), giving straightforward and general access to halogenated 3,5-diaryl- and alkylarylisoxazoles, pyrazoles and electron-rich benzenes from the corresponding scaffolds, is suggested. The method provides excellent regioselectivity, scalability to the gram scale, and a broad scope for both aromatics and halogens. A three-step, one-pot reaction protocol was developed, and a series of 3,5-diaryl-4-haloisoxazoles has been efficiently synthesized from 1,2-diarylcyclopropanes under suggested nitrosating-halogenating conditions.
- Bondarenko, Oksana B.,Karetnikov, Georgy L.,Komarov, Arseniy I.,Pavlov, Aleksandr I.,Nikolaeva, Svetlana N.
-
supporting information
p. 322 - 332
(2021/01/14)
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- Triptycenyl Sulfide: A Practical and Active Catalyst for Electrophilic Aromatic Halogenation Using N-Halosuccinimides
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A Lewis base catalyst Trip-SMe (Trip = triptycenyl) for electrophilic aromatic halogenation using N-halosuccinimides (NXS) is introduced. In the presence of an appropriate activator (as a noncoordinating-anion source), a series of unactivated aromatic compounds were halogenated at ambient temperature using NXS. This catalytic system was applicable to transformations that are currently unachievable except for the use of Br2 or Cl2: e.g., multihalogenation of naphthalene, regioselective bromination of BINOL, etc. Controlled experiments revealed that the triptycenyl substituent exerts a crucial role for the catalytic activity, and kinetic experiments implied the occurrence of a sulfonium salt [Trip-S(Me)Br][SbF6] as an active species. Compared to simple dialkyl sulfides, Trip-SMe exhibited a significant charge-separated ion pair character within the halonium complex whose structural information was obtained by the single-crystal X-ray analysis. A preliminary computational study disclosed that the πsystem of the triptycenyl functionality is a key motif to consolidate the enhancement of electrophilicity.
- Nishii, Yuji,Ikeda, Mitsuhiro,Hayashi, Yoshihiro,Kawauchi, Susumu,Miura, Masahiro
-
supporting information
p. 1621 - 1629
(2020/02/04)
-
- Preparation method of monobrominated aromatic hydrocarbon compound
-
The invention discloses a preparation method of a monobrominated aromatic hydrocarbon compound, which comprises the following steps: by using an aromatic hydrocarbon compound as a raw material, wateras a solvent and liquid bromine as a bromine source, reacting at room temperature for 4.5 hours, and after the reaction is finished, carrying out aftertreatment on the obtained reaction mixed solutionto obtain the monobrominated target product. According to the method, a high-selectivity bromination method is realized on the aromatic hydrocarbon compound under the action of water, and the monobrominated aromatic hydrocarbon compound is prepared. The method is high in reaction applicability, mild in condition, high in yield, green and environment-friendly.
- -
-
Paragraph 0075-0080
(2020/11/23)
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- Stepwise mechanism for the bromination of arenes by a hypervalent iodine reagent
-
A mild, metal-free bromination method of arenes has been developed using the combination of bis(trifluoroacetoxy)iodobencene and trimethylsilyl bromide. In situ-formed dibromo(phenyl)-λ3-iodane (PhIBr2) is proposed as the reactive intermediate. This methodology using PIFA/TMSBr has been applied with success to a great number of substrates (25 examples). The treatment of mono-substituted activated arenes led to para-brominated products (2u-z) in excellent 83-96% yields. Density functional theory calculations indicate a stepwise mechanism involving a double bromine addition followed by a type II dyotropic reaction with concomitant re-aromatization of the six-membered ring.
- Arrieta, Ana,Cossío, Fernando P.,Granados, Albert,Shafir, Alexandr,Vallribera, Adelina
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p. 2142 - 2150
(2020/03/11)
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- Molecular Vises for Precisely Positioning Ligands near Catalytic Metal Centers in Metal-Organic Frameworks
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We report the construction of a molecular vise by pairing a tritopic phenylphosphorus(III) linker and a monotopic linker in opposite positions within a metal-organic framework. The angle between these linkers at metal sites is fixed upon changing the functionality in the monotopic linker, while the distance between them is precisely tuned. This distance within the molecular vise is accurately measured by 1H-31P solid-state nuclear magnetic resonance spectroscopy. This unveils the impact of the distance on catalytic performance without interference from electrostatic effects or changes in the angle of the ligand, which is unprecedented in classic organometallic complexes.
- Yan, Wei,Li, Shenhui,Yang, Tao,Xia, Yucong,Zhang, Xinrui,Wang, Chao,Yan, Zier,Deng, Feng,Zhou, Qianghui,Deng, Hexiang
-
supporting information
p. 16182 - 16187
(2020/10/26)
-
- Molecular tweezers based on trivalent phosphine, preparation method of molecular tweezers, metal-molecular tweezers catalyst, and preparation method and application of metal-molecular tweezers catalyst
-
The invention relates to the technical field of inorganic-metal organic crossing and relates to the technical field of molecular tweezers, in particular to molecular tweezers based on trivalent phosphine, a preparation method of the molecular tweezers, a metal-molecular tweezer catalyst, a preparation method of the metal-molecular tweezer catalyst and an application of the metal-molecular tweezercatalyst, the molecular tweezer based on trivalent phosphine is named as P-MV-PCN-521-R, and R is any one of benzoic acid, p-nitrobenzoic acid, formic acid, p-methylbenzoic acid and dichloroacetic acid. The molecular tweezers based on the trivalent phosphine have distance adjustability. The trivalent phosphine-based metal-molecular tweezer catalyst provided by the invention has a high crystallinesurface area and a high specific surface area. The trivalent phosphine-based metal-molecular tweezer catalyst has good chemical stability and thermal stability, and is a primary condition for applyingthe trivalent phosphine-based metal-molecular tweezer catalyst to the actual field. The trivalent phosphine-based metal-molecular tweezer catalyst with adjustable distance provided by the invention has good selectivity for bromination of aromatic compounds.
- -
-
Paragraph 0038; 0059-0060
(2020/12/14)
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- Orthogonal Stability and Reactivity of Aryl Germanes Enables Rapid and Selective (Multi)Halogenations
-
While halogenation is of key importance in synthesis and radioimaging, the currently available repertoire is largely designed to introduce a single halogen per molecule. This report makes the selective introduction of several different halogens accessible. Showcased here is the privileged stability of nontoxic aryl germanes under harsh fluorination conditions (that allow selective fluorination in their presence), while displaying superior reactivity and functional-group tolerance in electrophilic iodinations and brominations, outcompeting silanes or boronic esters under rapid and additive-free conditions. Mechanistic experiments and computational studies suggest a concerted electrophilic aromatic substitution as the underlying mechanism.
- Deckers, Kristina,Fricke, Christoph,Schoenebeck, Franziska
-
supporting information
p. 18717 - 18722
(2020/08/25)
-
- Shelf-Stable (E)- A nd (Z)-Vinyl-λ3-chlorane: A Stereospecific Hyper-vinylating Agent
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We report the first stereoselective synthesis of stable (E)- A nd (Z)-β-chlorovinyl-λ3-chlorane via direct mesitylation of 1,2-dichloroethylene with mesityldiazonium tetrakis(pentafluorophenyl)borate under mild reaction conditions. The structure of the (E)-vinyl-λ3-chlorane was established by single-crystal X-ray analysis. Because of the enormously high leaving group ability of the aryl-λ3-chloranyl group, vinyl-λ3-chloranes undergo not only SNVσ-type reaction with extremely weak nucleophiles such as perfluoroalkanesulfonate, iodobenzene, and aromatic hydrocarbons but also coupling with phenylcopper(I) species.
- Kanazawa, Junichiro,Miyamoto, Kazunori,Takagi, Taisei,Uchiyama, Masanobu,Watanabe, Yuichiro
-
supporting information
p. 3469 - 3473
(2020/04/30)
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- Aromatic Halogenation Using N-Halosuccinimide and PhSSiMe3 or PhSSPh
-
We developed a mild aromatic halogenation reaction using a combination of N-halosuccinimide and PhSSiMe3 or PhSSPh. Less reactive aromatic compounds, such as methyl 4-methoxybenzoate, were brominated with PhSSiMe3 or PhSSPh and N-bromosuccinimide in high yields. No reaction was observed in the absence of PhSSiMe3 or PhSSPh. This method is also applicable to chlorination reactions using N-chlorosuccinimide and PhSSPh.
- Hirose, Yuuka,Yamazaki, Mirai,Nogata, Misa,Nakamura, Akira,Maegawa, Tomohiro
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p. 7405 - 7410
(2019/06/14)
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- Regioselective Halogenation of Arenes and Heterocycles in Hexafluoroisopropanol
-
Regioselective halogenation of arenes and heterocycles with N-halosuccinimides in fluorinated alcohols is disclosed. Under mild condition reactions, a wide diversity of halogenated arenes are obtained in good yields with high regioselectivity. Additionally, the versatility of the method is demonstrated by the development of one-pot sequential halogenation and halogenation-Suzuki cross-coupling reactions.
- Tang, Ren-Jin,Milcent, Thierry,Crousse, Benoit
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p. 930 - 938
(2018/01/28)
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- Applications of Selenonium Cations as Lewis Acids in Organocatalytic Reactions
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The use of trisubstituted selenonium salts as organic Lewis acids in electrophilic halogenation and aldol-type reactions has been developed. The substrate scope is broad. The reaction conditions are mild and compatible with various functionalities. This study opens a new avenue for the development of nonmetallic Lewis acid catalysis.
- He, Xinxin,Wang, Xinyan,Tse, Ying-Lung (Steve),Ke, Zhihai,Yeung, Ying-Yeung
-
supporting information
p. 12869 - 12873
(2018/09/14)
-
- Carbocation Catalyzed Bromination of Alkyl Arenes, a Chemoselective sp3 vs. sp2 C?H functionalization.
-
The versatility of the trityl cation (TrBF4) as a highly efficient Lewis acid organocatalyst is demonstrated in a light induced benzylic brominaion of alkyl-arenes under mild conditions. The reaction was conducted at ambient temperature under common hood light (55 W fluorescent light) with catalyst loadings down to 2.0 mol% using N-bromosuccinimide (NBS) as the brominating agent. The protocol is applicable to an extensive number of substrates to give benzyl bromides in good to excellent yields. In contrast to most previously reported strategies, this protocol does not require any radical initiator or extensive heating. For electron-rich alkyl-arenes, the trityl ion catalyzed bromination could be easily switched between benzylic sp3 C?H functionalization and arene sp2 C?H functionalization by simply alternating the solvent. This chemoselective switch allows for high substrate control and easy preparation of benzyl bromides and bromoarenes, respectively. The chemoselective switch was also applied in a one-pot reaction of 1-methylnaphthalene for direct introduction of both sp3 C?Br and sp2 C?Br functionality. (Figure presented.).
- Ni, Shengjun,El Remaily, Mahmoud Abd El Aleem Ali Ali,Franzén, Johan
-
supporting information
p. 4197 - 4204
(2018/09/25)
-
- Direct Transformation of Arylamines to Aryl Halides via Sodium Nitrite and N-Halosuccinimide
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A one-pot universal approach for transforming arylamines to aryl halides via reaction with sodium nitrite (NaNO2) and N-halosuccinimide (NXS) in DMF at room temperature under metal- and acid-free condition is described. This new protocol that is complementary to the Sandmeyer reaction, is suggested to involve the in situ generation of nitryl halide induce nitrosylation of aryl amine to form the diazo intermediate which is halogenated to furnish the aryl halide.
- Mukhopadhyay, Sushobhan,Batra, Sanjay
-
supporting information
p. 14622 - 14626
(2018/09/21)
-
- Transition-metal-free decarboxylative bromination of aromatic carboxylic acids
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Methods for the conversion of aliphatic acids to alkyl halides have progressed significantly over the past century, however, the analogous decarboxylative bromination of aromatic acids has remained a longstanding challenge. The development of efficient methods for the synthesis of aryl bromides is of great importance as they are versatile reagents in synthesis and are present in many functional molecules. Herein we report a transition metal-free decarboxylative bromination of aromatic acids. The reaction is applicable to many electron-rich aromatic and heteroaromatic acids which have previously proved poor substrates for Hunsdiecker-type reactions. In addition, our preliminary mechanistic study suggests that radical intermediates are not involved in this reaction, which is in contrast to classical Hunsdiecker-type reactivity. Overall, the process demonstrates a useful method for producing valuable reagents from inexpensive and abundant starting materials.
- Quibell, Jacob M.,Perry, Gregory J. P.,Cannas, Diego M.,Larrosa, Igor
-
p. 3860 - 3865
(2018/04/26)
-
- The Photostability of Two Optical Materials Based on Perylene Diimide Substituted by Different Aromatic Groups at the Bay Area
-
The perylene diimide substituented by thiophene rings at bay area shows photoactivity and can be used as a photo sensor, but another one substituented by mestylene groups is photostable. The single crystal of 1,7-mesitylene perylene diimide was obtained. X-ray diffraction data of the crystal revealed that the plane of the perylene core was hardly twisted by introduction of mesitylene groups. These mestylene groups are like clips maintaining the planarity of the perylene core. Density functional theory calculation was applied to study the difference of photophysical and photochemical properties. The discovery is valuable for design guidance of perylene diimides.
- He, Junjie,Li, Song,Zeng, Heping
-
p. 2800 - 2807
(2017/09/26)
-
- Accessing Pincer Bis(carbene) Ni(IV) Complexes from Ni(II) via Halogen and Halogen Surrogates
-
This communication describes the two-electron oxidation of (DIPPCCC)NiX (DIPPCCC = bis(diisopropylphenyl-benzimidazol-2-ylidene)phenyl); X = Cl or Br) with halogen and halogen surrogates to form (DIPPCCC)NiX3. These complexes represent a rare oxidation state of nickel, as well as an unprecedented reaction pathway to access these species through Br2 and halogen surrogate (benzyltrimethylammonium tribromide). The NiIV complexes have been characterized by a suite of spectroscopic techniques and can readily reduce to the NiII counterpart, allowing for cycling between the NiII/NiIV oxidation states.
- Martinez, Gabriel Espinosa,Ocampo, Cristian,Park, Yun Ji,Fout, Alison R.
-
supporting information
p. 4290 - 4293
(2016/05/10)
-
- A new recoverable Au(III) catalyst supported on magnetic polymer nanocomposite for aromatic bromination
-
This Letter presents a facile alternative synthesis of a recoverable Au(III) catalyst supported on Fe3O4@SiO 2～MPS grafted by poly(N-vinyl-2-pyrrolidone) (PVP). The solid magnetic support was prepared by anchoring 3-methacryloxypropyltrimethoxysilane (MPS) onto the Fe3O4@SiO2 surfaces followed by free radical polymerization with N-vinyl-2-pyrrolidone. Au(III) was immobilized onto the magnetic support in aqueous media to afford Au(III)/Fe 3O4@SiO2～PVP (catalyst 1). Catalyst 1 was characterized by FT-IR, TEM, VSM, TGA, XRD, and ICP-AES. The amount of Au in catalyst 1 was measured to be 0.64 wt % by ICP-AES. This newly prepared catalyst can catalyze the aromatic bromination reaction with comparable activity as homogeneous AuCl3. Moreover, the supported catalyst is easy to recover and can be used in four cycles without apparent loss of activity.
- Li, Bai,Gao, Linfeng,Bian, Fengling,Yu, Wei
-
supporting information
p. 1063 - 1066
(2013/04/10)
-
- Metal and H2O2 free aerobic oxidative aromatic halogenation with [RNH3+] [NO3-]/HX and [BMIM(SO3H)][NO3)x(X)y] (X = Br, Cl) as multifunctional ionic liquids
-
Novel multifunctional ionic liquids (ILs) are generated by addition of HBr or HCl to alkylammonium nitrates ([RNH3+] [NO 3-]) and to 3-methyl-1-(butyl-4-sulfonyl)imidazolium nitrate ([BMIM(SO3H)][NO3]). The resulting [RNH 3+] [NO3-]/HX and mono (3-methyl-1-(butyl-4-sulfonyl)imidazolium) monohalogenide mononitrate ([BMIM(SO3H)][NO3)x(X)y] (X = Br, Cl)) systems act as solvent and promoter for aerobic oxidative halogenation of arenes under mild conditions in high yields that can be repeated over several cycles.
- Prebil, Rok,Laali, Kenneth K.,Stavber, Stojan
-
supporting information
p. 2108 - 2111
(2013/06/05)
-
- Fast and efficient bromination of aromatic compounds with ammonium bromide and Oxone
-
A highly efficient, rapid and regioselective protocol was developed for the ring bromination of aromatic compounds under mild conditions with ammonium bromide as a source of bromine source and Oxone (potassium peroxysulfate) as an oxidant. No metal catalyst or acidic additive is required. A variety of aromatic compounds, including methoxy, hydroxy, amino, and alkyl arenes, reacted smoothly to give the corresponding monobrominated products in good to excellent yields in very short reaction times. Moreover, dibromination of deactivated anilines to give the corresponding dibromides proceeded in high yields. Interestingly, 1-(2-naphthyl)ethanone provided a ring-brominated product. Georg Thieme Verlag Stuttgart . New York.
- Naresh, Mameda,Arun Kumar, Macharla,Mahender Reddy, Marri,Swamy, Peraka,Nanubolu, Jagadeesh Babu,Narender, Nama
-
p. 1497 - 1504
(2013/06/27)
-
- Catalyst and solvent-free bromination of toluene derivatives by HBr-H 2O2 with visible-light photocatalysis using a continuous-flow micro reactor
-
The efficiency of the bromination of toluene derivatives has been improved significantly by utilising a combination of hydrogen peroxide (30%) and hydrogen bromide (40%) in a continuous-flow micro reactor. This catalyst and solvent-free reaction takes place by visible-light photocatalysis.
- Yu, Wu-Bin,Yu, Dong-Ping,Zheng, Ming-Ming,Shan, Shu-Ting,Li, Yu-Jin,Gao, Jian-Rong
-
experimental part
p. 258 - 260
(2012/09/22)
-
- Aromatic substitution in ball mills: Formation of aryl chlorides and bromides using potassium peroxomonosulfate and NaX
-
Aryl chlorides and bromides are formed from arenes in a ball mill using KHSO5 and NaX (X = Cl, Br) as oxidant and halogen source, respectively. Investigation of the reaction parameters identified operating frequency, milling time, and the number of milling balls as the main influencing variables, as these determine the amount of energy provided to the reaction system. Assessment of liquid-assisted grinding conditions revealed, that the addition of solvents has no advantageous effect in this special case. Preferably activated arenes are halogenated, whereby bromination afforded higher product yields than chlorination. Most often reactions are regio- and chemoselective, since p-substitution was preferred and concurring side-chain oxidation of alkylated arenes by KHSO5 was not observed. The Royal Society of Chemistry.
- Schmidt, Robert,Stolle, Achim,Ondruschka, Bernd
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p. 1673 - 1679
(2013/02/22)
-
- In situ acidic carbon dioxide/water system for selective oxybromination of electron-rich aromatics catalyzed by copper bromide
-
Carbon dioxide, being one of the major greenhouse gases responsible for global warming, its atmospheric level grows ever faster since the beginning of industrial era. Great efforts have been devoted to developing versatile technologies/processes to adjust and manipulate the rapid growth of CO 2 emission. Besides CO2 capture and storage/sequestration (CCS) to control its emission, chemical utilization of the captured CO 2 (CCU) emerges to be a rational technique for economical benefits as well as environmental concerns. As for the aim of CO2 utilization, an environmentally benign CO2/water reversible acidic system was developed for the copper (II)-catalyzed selective oxybromination of electron-rich aromatics without the need of any conventional acid additive and organic solvent. Notably, up to 95% yields of the bromination products were attained with good regio-selectivity when cupric bromide was used as the catalyst and lithium bromide as a cheap and easy handling bromine source under supercritical CO2. The catalytic system worked well for electron-rich aromatics including ethers, sulfides and mesitylene. Carbonic acid in situ formed from CO2 and water is supposed to act as the proton donator in the Bronsted acid-promoted reaction. Notably, CO2 in this study serves as a reaction medium and a promoter in conjunction with water and also provides safe environment for aerobic reactions. Given with excellent reaction efficiency as well as no need of neutralization disposal, this process thus represents an environmentally friendly approach for aerobic bromination of aromatics with essential reduction of CO2 emission as well as an economically beneficial way for application of captured CO2.
- Liu, An-Hua,Ma, Ran,Zhang, Meng,He, Liang-Nian
-
-
- An efficient and regioselective monobromination of electron-rich aromatic compounds using catalytic hypervalent iodine(III) reagent
-
An efficient and regioselective monobromination of electron-rich aromatic compounds is reported in which iodobenzene is used as the recyclable catalyst in combination with m-chloroperbenzoic acid as the terminal oxidant. The bromination of electron-rich aromatic compounds with lithium bromide was fast in tetrahydrofuran at room temperature, providing regioselective monobrominated products in good yields.
- Zhou, Zhongshi,He, Xuehan
-
experimental part
p. 207 - 209
(2011/03/18)
-
- Nucleophilic substitution of hydrogen in naphthalene by chloride (Cl -) in ionic liquids
-
Nucleophilic aromatic substitution of hydrogen in non-activated aromatic ring, a very rare phenomenon in organic chemistry, is found in ionic liquids containing Cl- as anion under mild reaction conditions. The reaction may be carried out by the addition of the halogen-bonding adduct (Br 2Cl-) as nucleophile to aromatic ring carbon atom, leading to the formation of the nucleophilic substitution product.
- Shi, Shen Yi,Kong, Ai Guo,Zhao, Xin Hua,Ding, Han Ming,Yang, Fan,Shan, Yong Kui
-
experimental part
p. 147 - 150
(2012/01/03)
-
- Gold(III)-catalyzed direct acetoxylation of arenes with iodobenzene diacetate
-
AuCl3-catalyzed direct acetoxylation of electron-rich aromatic compounds has been achieved with iodobenzene diacetate as the acetoxylation reagent.
- Qiu, Di,Zheng, Zhitong,Mo, Fanyang,Xiao, Qing,Tian, Yu,Zhang, Yan,Wang, Jianbo
-
supporting information; experimental part
p. 4988 - 4991
(2011/11/13)
-
- Gold-catalyzed halogenation of aromatics by N-halosuccinimides
-
(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
-
scheme or table
p. 2028 - 2032
(2010/06/17)
-
- Bromination of aromatic compounds using ammonium bromide and oxone
-
A simple, efficient and mild method for the selective bromination of activated aromatic compounds using ammonium bromide as the source of bromine and Oxone as the oxidant in methanol or water as solvent is reported. The reaction proceeds at ambient temperature in yields ranging from moderate to excellent without a catalyst. Georg Thieme Verlag Stuttgart.
- Arunkumar, MacHarla,Rohitha, Chozhiyath Nappunni,Kulkarni, Shivanand Janardhan,Narender, Nama
-
experimental part
p. 1629 - 1632
(2010/06/20)
-
- PROCESS FOR PRODUCING ORGANIC COMPOUND AND ORGANIC COMPOUND OBTAINED BY THE SAME
-
Disclosed herein are a reaction method and a production method of an organic compound which are capable of achieving high reaction selectivity according to the purpose and a high production rate of a target substance. The methods include at least two fluids, wherein at least one kind of the fluids is a fluid containing at least one organic compound and at least one kind of the fluids other than the above fluid is a fluid containing at least one reactant in the form of a liquid or solution, and the respective fluids join together in a thin film fluid formed between processing surfaces arranged to be opposite to each other so as to be able to approach to and separate from each other, at least one of which rotates relative to the other, whereby an organic reaction is performed in the thin film fluid.
- -
-
Page/Page column 78
(2010/08/18)
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- Environmentally benign electrophilic and radical bromination 'on water': H2O2-HBr system versus N-bromosuccinimide
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A H2O2-HBr system and N-bromosuccinimide in an aqueous medium were used as a 'green' approach to electrophilic and radical bromination. Several activated and less activated aromatic molecules, phenylsubstituted ketones and styrene were efficiently brominated 'on water' using both systems at ambient temperature and without an added metal or acid catalyst, whereas various non-activated toluenes were functionalized at the benzyl position in the presence of visible light as a radical activator. A comparison of reactivity and selectivity of both brominating systems reveals the H2O2-HBr system to be more reactive than NBS for benzyl bromination and for the bromination of ketones, while for electrophilic aromatic substitution of methoxy-substituted tetralone it was higher for NBS. Also, higher yields of brominated aromatics were observed when using H2O2-HBr 'on water'. Bromination of styrene reveals that not just the structure of the brominating reagent but the reaction conditions: amount of water, organic solvent, stirring rate and interface structure, play a key role in defining the outcome of bromination (dibromination vs bromohydroxylation). In addition, mild reaction conditions, a straightforward isolation procedure, inexpensive reagents and a lower environment impact make aqueous brominating methods a possible alternative to other reported brominating protocols.
- Podgor?ek, Ajda,Stavber, Stojan,Zupan, Marko,Iskra, Jernej
-
experimental part
p. 4429 - 4439
(2009/10/09)
-
- Synthesis of arylbromides from arenes and Nbromosuccinimide bromosuccinimide (NBS) in acetonitrile - A convenient method for aromatic bromination
-
Regioselective and chemoselective electrophilic bromination of a wide series of activated arenes using N-bromosuccinimide (NBS) in acetonitrile occurs readily. Environmentally friendly conditions, large substrate scope, and ease of synthesis enhance the utility of this method over other electrophilic bromination conditions.
- Zysman-Colman, Eli,Arias, Karla,Siegel, Jay S.
-
experimental part
p. 440 - 447
(2009/12/01)
-
- Halo- and azidodediazoniation of arenediazonium tetrafluoroborates with trimethylsilyl halides and trimethylsilyl azide and Sandmeyer-type bromodediazoniation with Cu(I)Br in [BMIM][PF6] ionic liquid
-
(Chemical Equation Presented) Reaction of [ArN2][BF4] salts immobilized in [BMIM][PF6] ionic liquid (IL) with TMSX (X = I, Br) and TMSN3 represents an efficient method for the preparation of iodo-, bromo-, and azido-derivatives via dediazoniation. The reactions can also be effected starting with ArNH2 by in situ diazotization with [NO][BF4] followed by reaction with TMSX or TMSN3. Depending on the substituents on the benzenediazonium cation, competing fluorodediazoniation (ArF formation) and hydrodediazoniation (ArH formation) were observed. Dediazoniation with TMSN3 and with TMSI generally gave the highest chemoselectivity toward ArN3 and ArI formation. The IL was recycled and reused up to 5 times with no appreciable decrease in the conversions. Multinuclear NMR monitoring of the interaction of [ArN 2][BF4]/TMSX, [BMIM][PF6]/TMSX, and [BMIM][PF6]/TMSX/[ArN2][BF4] indicated that TMSF is formed primarily via [ArN2][BF4]/ TMSX, generating [ArN2][X] in situ, which gives ArX on dediazoniation. Competing formation of ArF in Sandmeyer-type bromodediazoniation of [ArN 2][BF4] with Cu(I)Br immobilized in the IL points to significant involvement of heterolytic dediazoniation.
- Hubbard, Abigail,Okazaki, Takao,Laali, Kenneth K.
-
p. 316 - 319
(2008/09/17)
-
- Contrasting chemoselectivities in the ultrasound and microwave assisted bromination reactions of substituted alkylaromatics with N-bromosuccinimide
-
Ultrasound and microwave assisted bromination reactions of various alkylaryls with N-bromosuccinimide, either neat or in water, shows diverse chemoselectivity. Thus, ring substitution occurs in water with ultrasound, whereas with microwaves both side-chain α-bromination and ring substitution occur. With neat reactants, side-chain α-bromination predominates for microwave assisted reactions. In the presence of water the chemoselectivity with microwave-promoted bromination is similar to that observed using classical methods.
- Heropoulos, Georgios A.,Cravotto, Giancarlo,Screttas, Constantinos G.,Steele, Barry R.
-
p. 3247 - 3250
(2008/02/02)
-
- Method for brominating organic compounds
-
The present invention relates to processes for the bromination of organic compounds, and to bromination microreactors for carrying out these processes.
- -
-
Page/Page column 5-6
(2008/06/13)
-
- Visible light induced 'on water' benzylic bromination with N-bromosuccinimide
-
Benzylic bromination of various 4-substituted toluenes (Me, tert-Bu, COOEt and COMe) was effectively conducted with NBS in pure water and with a 40 W incandescent light-bulb as an initiator of the radical chain process, while electron donating groups (OMe and NHAc) directed the reaction to electrophilic aromatic substitution.
- Podgor?ek, Ajda,Stavber, Stojan,Zupan, Marko,Iskra, Jernej
-
p. 1097 - 1099
(2007/10/03)
-
- Association of fluorous "phase-vanishing" method with visible-light activation in benzylic bromination by bromine
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In this study the "phase-vanishing" method for diffusion-controlled addition of a reagent (Br2) to a reaction phase via a fluorous membrane (C8F18) is combined with an additional mode of activation (visible-light) to achieve the benzyl bromination of various alkyl-substituted aromatic compounds in a concentrated solution. Benzyl bromination of p-tert-butyl-toluene proceeded in various solvents including hexane and methanol, while the reaction of the neat substrate showed a similar selectivity as in carbon tetrachloride. The effect of the substituent on the para position of toluene on the course of bromination revealed three processes: benzyl bromination with H, Me, tBu and CO2Et substituents, aromatic bromination with OMe and NHAc substituents and the reaction of the 4-acetyl derivative at the substituent to form an α-bromo ketone. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
- Podgorsek, Ajda,Stavber, Stojan,Zupan, Marko,Iskra, Jernej
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p. 483 - 488
(2007/10/03)
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- One-pot halogenation-Heck coupling reactions in ionic liquids
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Traditional cross-coupling approaches rely upon two steps - halogenation and coupling - each of which is viewed and conducted independently. In an effort to develop a one-pot approach, we have noted that the halogenation and Heck coupling reactions can both be conducted in a room-temperature ionic liquid without the need to isolate the halogenated intermediate. Application to several systems shows that this approach works well for moderately to highly electron-rich aromatics. Georg Thieme Verlag Stuttgart.
- Handy, Scott T.
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p. 3176 - 3178
(2008/02/13)
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- Synthesis and molecular structures of zirconium and hafnium complexes bearing dimethylsilandiyl-bis-2,4,6-trimethylindenyl and dimethylsilandiyl-bis- 2-methyl-4,6-diisopropylindenyl ligands
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Zirconium and hafnium ansa-complexes containing 2,4,6-trialkyl-substituted indenyl fragments were synthesized and unambiguously characterized. Mixtures of rac- and meso-Me2Si(2-Me-4,6-R2C9H 3-η5)2MCl2, where R = Me, i-Pr and M = Zr, Hf, were obtained by a treatment of MCl4 by dilithium salts of the respective bis(2,4,6-trialkylindenyl)dimethylsilanes in toluene. Alternatively, better yields of the same complexes can be obtained by the reaction between metal tetrachlorides and indenyl-tin derivatives gave the desired ansa-metallocenes. All rac- and meso-complexes of Zr and Hf were isolated in an analytically pure form, and six of these ansa-metallocenes were characterized by X-ray crystal structure analysis.
- Izmer, Vyacheslav V.,Sorokin, Denis A.,Kuz'Mina, Lyudmila G.,Churakov, Andrei V.,Howard, Judith A.K.,Voskoboynikov, Alexander Z.
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p. 1067 - 1079
(2007/10/03)
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- Mild and efficient direct aromatic iodination
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Aryl iodides are important synthetic intermediates that can be transformed into tritium labelled compounds by metal-mediated hydrodehalogenation and also react in a number of important synthetic transformations. We present ICl/In(OTf)3 as a new reagent combination for mild iodination, suitable for acid-sensitive substrates such as carbohydrates.
- Johnsson, Richard,Meijer, Andréas,Ellervik, Ulf
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p. 11657 - 11663
(2007/10/03)
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- Novel bromination method for anilines and anisoles using NH 4Br/H2O2 in CH3COOH
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A simple, efficient, regioselective, environmentally safe, and economical method for the oxybromination of anilines and anisoles without catalyst is reported. The electrophilic substitution of bromine generated in situ from ammonium bromide as a bromine source and hydrogen peroxide as an oxidant for the first time.
- Krishna Mohan,Narender,Srinivasu,Kulkarni,Raghavan
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p. 2143 - 2152
(2007/10/03)
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- Nitrile ylide dimerization: Investigation of the carbene reactivity of nitrile ylides
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A series of novel hexaaryl diazatrienes 5 ("nitrile ylide dimers") were synthesized directly from the corresponding diaryl ketimines 12 and dichlorotoluenes 13 in a facile one-pot synthesis. The carbene character of the nitrile ylides was investigated by varying the substituents on the aromatic ring adjacent to the carbene center. The isolation of the corresponding carbene dimers as stable crystalline materials with absorption maxima (λmax) from 363 to 422 nm was shown to be promoted by the absence of strongly electron-withdrawing substituents. The crystal structures indicate that the E-isomers were isolated when phenyl, 3-methylphenyl, and 3-chlorophenyl substituents are present at the carbene carbon; the Z-isomer was isolated when the more sterically hindered 2,4,6-trimethylphenyl substituent (Mes) is present. The 1H NMR spectra of the E-isomers demonstrate the nonequivalence of the aromatic rings, in which two of the aromatic rings of the imine moiety are pseudoaxial and the remaining aromatic rings are pseudoequatorial. The reactions proceed via the intermediate nitrile ylides 1 generated by the base-promoted 1,1-elimination of HCl from the intermediate chloroimine 14. The nitrile ylide was also generated by 1,3-elimination of HCl from the imidoyl chloride 18, confirming common pathways via the nitrile ylide as the dimer products obtained from these different routes were identical. The strongly electron-withdrawing 4-nitrophenyl substituent promotes the linear carbanion character of the 1,3-dipole and no dimer is formed.
- Fergus, Suzanne,Eustace, Stephen J.,Hegarty, Anthony F.
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p. 4663 - 4669
(2007/10/03)
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- OOxidative bromination of activated aromatic compounds using aqueous nitric acid as an oxidant
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Oxidative bromination of activated aromatic compounds using alkali metal bromide salts and aqueous nitric acid to the corresponding bromo-derivatives is achieved in a liquid-liquid, two-phase system under ambient conditions. Nitric acid offers a dual function of an oxidant as well as a proton donor, which is essential for oxidative bromination using metal bromide salts. Bromination as well as chlorination could be accomplished with this simple system.
- Joshi, Ashutosh V.,Baidossi, Mubeen,Mukhopadhyay, Sudip,Sasson, Yoel
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p. 568 - 570
(2013/09/02)
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- Unexpected differences in the α-halogenation and related reactivity of sulfones with perhaloalkanes in KOH-t-BuOH
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Most alkyl phenyl sulfones are readily α-chlorinated with CCl4 and α-brominated with CBrCl3 in KOH-t-BuOH via radical-anion radical pair (RARP) reactions. While isopropyl mesityl sulfone (4) is easily α-chlorinated with CCl4, it was completely recovered when treated with the more reactive CBrCl3. Subsequent investigations showed the latter result to be due to the poor acidity of 4 together with the rapid depletion of CBrCl3 and KOH by their reaction with each other, and led to a variety of other important results. 4-Hydroxyphenyl isopropyl sulfone (6) is unreactive with either CCl4 or CBrCl3 in KOH-t-BuOH, its phenoxide anion strongly reducing the electronegativity of the sulfonyl group, thereby inhibiting α-anion formation. This effect is reversed by the electron-withdrawing influence of two α-phenyls, so that benzhydryl 4-hydroxyphenyl sulfone (8) is readily α-halogenated in KOH-t-BuOH with CCl4 or CBrCl3. On further contact with KOH-t-BuOH the α-halogenated sulfones from 8 are decomposed into benzophenone and phenol. While the α-halogenated derivatives of 4-methoxyphenyl benzhydryl sulfone (9) are stable to base, they are decomposed even under mildly acidic conditions into 4-methoxyphenyl 4-methoxybenzenethiolsulfonate (9c), phenol, and benzophenone. Mono-α-halogenation of benzyl phenyl sulfone (10) enhances the rate of the subsequent halogenation, so that α,α-dihalogenation is attained while much substrate is still present and the mono-α-halogenated product is not detected. The ease of reductive debromination of α-bromo sulfones with Cl3C- was correlated with the stability of the formed α-anions, explaining the success with α-bromobenzylic sulfones but failure with α-bromoalkyl sulfones. In the presence of air and the absence of competing halogenation, formation of the α-anions of alkyl aryl sulfones is quickly accompanied by oxidative cleavage by atmospheric O2, leading to the formation of arenesulfonyl alcohols, arenesulfonyl halides, and haloarenes.
- Meyers, Cal Y.,Chan-Yu-King, Roch,Hua, Duy H.,Kolb, Vera M.,Matthews, Walter S.,Parady, Thomas E.,Horii, Toyokazu,Sandrock, Paul B.,Hou, Yuqing,Xie, Songwen
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p. 500 - 511
(2007/10/03)
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- Direct and regioselective iodination and bromination of benzene, naphthalene and other activated aromatic compounds using iodine and bromine
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Direct and regioselective iodination and bromination of benzene, naphthalene and other activated aromatic compounds with iodine and bromine or their sodium salts proceed well in the presence of Fe(NO3) 3·1.5N2O4/charcoal in CH 2Cl2 at room temperature.
- Firouzabadi,Iranpoor,Shiri
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p. 8781 - 8785
(2007/10/03)
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- Oxidative halogenation of aromatic compounds with metal halides and sodium bismuthate
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A new mild and efficient method for aromatic halogenation with a wide variety of halides in the presence of sodium bismuthate NaBO3 in AcOH is reported. Metal halides of groups Ia, IIa, IIIa, IVa, Va, and the first row of transition elements are suitable for this method.
- Muathen, Hussni A.
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p. 164 - 168
(2007/10/03)
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- Pyridinium dichlorobromate: A new stable brominating agent for aromatic compounds
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Pyridinium dichlorobromate (PyHBrCl2, 1) is a new example of iminium-trihalide complexes. The compound is prepared from pyridine and chlorine in the presence of aqueous hydrogen bromide. The crystalline trihalide is quite stable and acts as a safe source of positive bromine. It shows a remarkable reactivity towards aromatic compounds compared with other bromine complexes. It is also considered as a potential source for bromine chloride BrCl.
- Muathen, Hussni A.
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p. 169 - 171
(2007/10/03)
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- Efficient method for the preparation of aromatic bromides and iodides by ferrocenium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate-catalyzed halogenation with bromine and iodine monochloride
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Direct iodination and bromination of various aromatic compounds with 1.1-2.0 molar amounts of iodine monochloride (ICl) and 1.1-3.0 molar amounts of bromine proceeded smoothly to afford the corresponding aromatic iodides and bromides, respectively, in good to excellent yields by using 0.05 molar amount of ferrocenium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate, Cp2FeB[3,5-(CF3)2C6H 3]4 (1), in the presence of ZnO. Iodination of toluene in the co-existence of 0.5 molar amount of DDQ also proceeded to give iodotoluenes in high yield.
- Kitagawa, Hideo,Shibata, Tsuyoshi,Matsuo, Jun-Ichi,Mukaiyama, Teruaki
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p. 339 - 345
(2007/10/03)
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- Silyltrielane R'nEHal3-n (E = Al, Ga, in; R' = SitBu2Ph): Synthesen, charakterisierung, strukturen [1]
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Water- and oxygen-sensitive compounds of the type R'nEHal3-n (R' = SitBu2Ph; E = Triel) with or without donors, viz. R'AlBr2, R'3Al, R'GaCl2 'THF, R'GaCl2, R'3Ga, R'InCl2?THF and R'3 In have been synthesized by reaction of EX3 with NaSitBu2Ph (prepared for this purpose) in the absence or presence of donors. The dihalides R'EHal2 have also been obtained by reaction of R'3E with EHal3, whereas monohalides R'2EHal are not accessible via these and other routes up to date. All trielanes have been characterized by NMR and the structures of the R'3E compounds have been determined by X-ray analyses.
- Wiberg, Nils,Blank, Thomas,Lerner, Hans-Wolfram,N?th, Heinrich,Habereder, Tassilo,Fenske, Dieter
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p. 652 - 658
(2007/10/03)
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- Increasing the selectivity of bromination of aromatic compounds using Br2/SiO2
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Br2/SiO2 possessed considerable practical advantages over traditional reagents for the bromination of aromatic hydrocarbons, e.g., toluene, o-, m-, and p-xylene, anthracene and phenol. In the presence of SiO2, toluene reacted with bromine instantly. Compounds containing electron-donating substituents showed mainly bromination on the rings. The behavior of o-, m-, and p-xylene showed predominant substitution on the rings. The bromination of phenol to p-bromophenol showed good yield at 81%. Naphthalene was monobrominated to 1-bromonaphthalene with a yield of 84% in 2 has the potential to alter reaction selectivity. It may be able to switch a mechanism from radical to polar, or to influence the regioselectivity of the products formed. In the absence of SiO2, selectivity was lost and a mixture of products by substitution of bromine atom on the ring and on the side chain without any preferability was obtained. The nature of silica gel was important for the success of the reaction. Optimal results were obtained with silica gel dried at 250°C for 1 hr.
- Ghiaci,Asghari
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p. 1151 - 1152
(2007/10/03)
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- Hydrochloric acid catalysis of N-bromosuccinimide (NBS) mediated nuclear aromatic brominations in acetone
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Nuclear bromination of activated aromatic substrates can be achieved quickly and in high yields using N-bromosuccinimide (NBS) in acetone with 1 M HCl catalysis.
- Andersh, Brad,Murphy, Drew L.,Olson, Ryan J.
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p. 2091 - 2098
(2007/10/03)
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