- Solvent effects on the formation and decay of an exciplex between the lowest excited singlet state of 9,10-dibromoanthracene and ground-state amine (N,N-dimethylaniline or triethylamine)
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Picosecond laser photolysis reveals the formation of an exciplex between the lowest excited singlet state [DBA*(S1)] of 9,10-dibromoanthracene (DBA) and ground-state amine in acetonitrile (CH3CN) and ethanol (EtOH) containing N,N-dimethylaniline (DMA) [and n-heptane (HP) containing DMA or triethylamine (TEA)]. Only in CH3CN-DMA, however, can decomposition of the DBA-DMA exciplex into the DBA radical anion (DBA.-) and the DMA radical cation be seen, indicating very small generation of DBA.- from the DBA-amine exciplex formed in EtOH-DMA and HP-amine (DMA or TEA). Interestingly, no DBA-TEA exciplex is formed in CH3CN and EtOH containing TEA but nanosecond laser photolysis reveals the existence of DBA.- in the former solvent. Furthermore, the rate of DBA → 9-bromoanthracene debromination upon steady-state photolysis in CH3CN-TEA is 1 order of magnitude smaller than that in CH3CN-DMA but 2 or 3 orders of magnitude greater than those in EtOH and HP containing amine. This suggests that diffusion-controlled quenching of DBA*(S1) by TEA in CH3CN and EtOH gives rise to the formation of a nonemissive short-lived encounter complex or ion pair. It thus be concluded that generation of DBA.- from the DBA-amine exciplex or the encounter complex (or the ion pair) is affected by the dielectric constant of a pure solvent.
- Nakayama, Toshihiro,Hamana, Tetsuya,Jana, Pallabi,Akimoto, Seiji,Yamazaki, Iwao,Hamanoue, Kumao
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Read Online
- Photochemical reactions of hydroarenes with N-bromosuccinimide
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The photochemical reactions of 1,2,3,4-tetrahydronaphthalene (THN), 9,10-dihydrophenanthrene (DHP), 9,10-dihydroanthracene (DHA), and acenaphthene (AN) with N-bromosuccinimide (NBS) were investigated under N2 atmosphere at room temperature. The results show that the relative reactivities of the hydroarenes toward a photochemical reaction with NBS are THN DHP AN DHA, which is consistent with the stabilities of the radicals produced by benzylic hydrogen abstraction from the hydroarenes. Photochemical reactions of THN and DHP mainly afforded dehydrogenated products, while the photobrominations of the dehydrogenated products from AN and DHA with NBS proceeded readily.
- Zong, Zhi-Min,Zhang, Wei-Hong,Jiang, Qun,Lu, Jin,Wei, Xian-Yong
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Read Online
- Construction of Donor-Acceptor Polymers via Cyclopentannulation of Poly(arylene ethynylene)s
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A one-step postpolymerization modification that converts three high bandgap poly(arylene ethynylene)s into low bandgap donor-acceptor copolymers is described. The strategy relies on a palladium-catalyzed cyclopentannulation reaction between the main-chain ethynylene functionality and a small molecule aryl bromide (6-bromo-1,2-dimethylaceanthrylene). The reaction installs new cyclopenta[hi]aceanthrylene electron-accepting groups between the electron rich arylenes along the polymer backbone. The modified polymers include poly(9,9-didodecyl-fluorene-2,7-ethynylene), poly(9-dodecyl-carbazole-2,7-ethynylene), and poly(2,5-dioctyloxyphenylene-1,4-ethynylene). The functionalization efficiency was evaluated via isotopic 13C labeling of the polymeric ethynylene carbons and then monitoring the chemical environment of those carbons via NMR spectroscopy. Near complete conversion of the sp carbon species to sp2 carbon species was observed, which demonstrates the high efficiency of the modification strategy. Gel permeation chromatography shows that the hydrodynamic radius of the polymers is reduced considerably going from linear to kinked polymer morphology upon functionalization, and molecular dynamics simulations illustrate the underlying morphological change. The newly formed donor-acceptor polymers showed dramatically different optical and electrochemical properties from the precursor poly(arylene ethynylene) polymers. A new absorption band centered at ～650 nm represents a red-shift of >300 nm for the onset of absorption compared with that of precursor polymers and cyclic voltammetry shows two new low-lying reduction peaks that coincide with the cyclopenta[hi]aceanthrylene moiety.
- Zhu, Xinju,Bheemireddy, Sambasiva R.,Sambasivarao, Somisetti V.,Rose, Peter W.,Torres Guzman, Rubicelys,Waltner, Amanda G.,Dubay, Kateri H.,Plunkett, Kyle N.
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Read Online
- Bis-selenonium Cations as Bidentate Chalcogen Bond Donors in Catalysis
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Lewis acids are frequently employed in catalysis but they often suffer from high moisture sensitivity. In many reactions, catalysts are deactivated because of the problem that strong Lewis acids also bond to the products. In this research, hydrolytically stable bidentate Lewis acid catalysts derived from selenonium dicationic centers have been developed. The bis-selenonium catalysts are employed in the activation of imine and carbonyl groups in various transformations with good yields and selectivity. Lewis acidity of the bis-selenonium salts was found to be stronger than that of the monoselenonium systems, attributed to the synergistic effect of the two cationic selenonium centers. In addition, the bis-selenonium catalysts are not inhibited by strong bases or moisture.
- He, Xinxin,Wang, Xinyan,Tse, Ying-Lung Steve,Ke, Zhihai,Yeung, Ying-Yeung
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p. 12632 - 12642
(2021/10/21)
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- Bromination of phenyl ether and other aromatics with bromoisobutyrate and dimethyl sulfoxide
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Bromoisobutyrate has been used for the first time as a general brominating source for the direct bromination of a diverse of simple phenyl ethers. Aromatic ethers bearing various substituents could be compatible in this reaction system delivering brominated arenes in moderate to good yields. The reaction system can also be expanded to bromination of phenols and unactivated arene. This process can be regarded as an alternative for the well-established bromination systems for bromoarene synthesis.
- Li, Jia-Qin,Chen, Xiao-Hui,Wang, Xian-Xun,Cui, Hai-Lei
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supporting information
(2021/09/09)
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- Stepwise mechanism for the bromination of arenes by a hypervalent iodine reagent
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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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- A sensitive TICT Probe exhibiting ratiometric fluorescence repose to detect hydrazine in solution and gas phase
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A twisted intramolecular charge transfer (TICT) based probe, dicyanovinyl-9-phenylanthracene (DPA) has been designed and synthesized for the detection of hydrazine (N2H4) with good limit of detection (LOD, 7.85 nM (0.25 ppb)). Upon interaction with hydrazine the terminal electron withdrawing dicyanovinyl function is changed to electron donating amino/hydrazone function. Consequently, the significant change in the photophysical property of the probe is attributed to a change in orientation of charge propagation. The probe with hydrazine shows ratiometric fluorescence “turn-on” response as well as naked-eye sensitive color change in the medium. The surface morphology studies (SEM and TEM) suggested about amorphousness and crystalline nature of the probe DPA and derivative DPA-HDz, respectively. The conducting behavior of the probe decreases upon interaction with hydrazine because of decrease in amorphousness of the matrix and increase in relatively more rigid crystalline structure. Additionally, the probe been utilized to detect hydrazine vapor in solution and on test paper strip with good naked-eye sensitive responses.
- Gupta, Ramesh C.,Dwivedi, Sushil K.,Ali, Rashid,Razi, Syed S.,Tiwari, Rudramani,Krishnamoorthi,Misra, Arvind
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supporting information
(2020/02/22)
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- Cooperativity within the catalyst: alkoxyamide as a catalyst for bromocyclization and bromination of (hetero)aromatics
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Alkoxyamide has been reported as a catalyst for the activation ofN-bromosuccinimide to perform bromocyclization and bromination of a wide range of substrates in a lipophilic solvent, where adequate suppression of the background reactions was observed. The key feature of the active site is the alkoxy group attached to the sulfonamide moiety, which facilitates the acceptance as well as the delivery of bromonium species from the bromine source to the substrates.
- Mondal, Haripriyo,Sk, Md Raja,Maji, Modhu Sudan
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supporting information
p. 11501 - 11504
(2020/10/12)
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- Catalyst-Free Photodriven Reduction of α-Haloketones with Hantzsch Ester
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Catalyst-free dehalogenation of α-haloketones under visible light irradiation is studied. The reactions were carried out in common organic solvent. The outcomes of dechlorination are excellent in yields up to 92%, and it is also applicable to bromides, which give even higher yields. The reaction is tolerable to a broad spectrum of substrates, especially to aromatic ketones, including various aryl and hetaryl groups. There are two examples of aliphatic ketones presented in the paper, although their reactivities are not as high as that of the aromatic ketones.
- Lu, Zheng,Yang, Yong-Qing
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p. 508 - 515
(2019/01/10)
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- A new cross-linkable 9,10-diphenylanthracene derivative as a wide bandgap host for solution-processed organic light-emitting diodes
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Efficient organic light-emitting diodes (OLEDs) can be obtained using multilayered architectures where the processes of charge injection, transport and recombination are separated and optimized in each layer. Processing these structures from solution requires strategies to avoid redissolution or damage of the previously deposited layers. Several reports have demonstrated the development of cross-linkable hole transport materials, while less literature describes the synthesis and applications of such wide bandgap host materials for multilayered OLEDs. In this work we introduce a cross-linkable derivative of 9-(4-(10-phenylanthracene-9-yl)phenyl)-9H-carbazole incorporating styrene moieties (SPhPC) which can be efficiently cross-linked via radical polymerization. We present the synthesis and characterization of SPhPC, as well as its application as the host in the light-emitting layer to prove the concept of solution processed blue OLEDs.
- Hallani, Rawad K.,Fallah Hamidabadi, Vahid,Huckaba, Aron Joel,Galliani, Gianmarco,Babaei, Azin,La-Placa, Maria-Grazia,Bahari, Ali,McCulloch, Iain,Nazeeruddin, Mohammad Khaja,Sessolo, Michele,Bolink, Henk J.
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p. 12948 - 12954
(2019/01/03)
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- A novel phosphorus-containing organic ligand 1 - (9 - anthryl) - 2 - diphenyl phosphine - imidazole synthesis method and application
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1-(9-anthracene)-2-diphenylphosphino-imidazole is a phosphorus-containing imidazole-containing nitrogen-phosphorus bidentate ligand, and can be conveniently synthesized by deoprotonating anthracene imidazole and then reacting with diphenylchlorophosphine at one step. The ligand is simple and convenient to synthetize, and large-scale industrial production can be realized as the ligand can stably exist in the air under a normal-temperature condition. Sonogashira is catalyzed in situ by the ligand and alladium dichloride to have cross coupling reaction, and the ligand has good reaction activity on aryl iodides and aryl bromides. The catalyst inherits the advantage that the usage amount of the traditional phosphorus catalyst is less, and can be used for overcoming the defect that the aryl bromides are difficult to react. Reaction is carried out in an acetonitrile system by adopting cesium carbonate as a base, the catalyst is less in usage amount, mild in reaction conditions, short in reaction time, and convenient in aftertreatment, and has important application in synthesis of important chemical raw material aryl acetylene, thus having great application prospect in industrial production.
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Paragraph 0023; 0028; 0029
(2018/04/20)
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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
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supporting information
p. 12869 - 12873
(2018/09/14)
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- Environmentally benign indole-catalyzed position-selective halogenation of thioarenes and other aromatics
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Halogenated aromatic compounds are the cores of many pharmaceutical, agricultural and chemical products but they are commonly prepared using electrophilic halogenation reactions in non-green chlorinated solvents under harsh conditions. A separate problem happens in the aromatic halogenation of thioarenes because they readily undergo oxidative side-reactions. Herein we report an environmentally benign electrophilic bromination of aromatics using an indole-catalytic protocol, which is suitable for a wide range of substrates including thioarenes.
- Shi, Yao,Ke, Zhihai,Yeung, Ying-Yeung
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supporting information
p. 4448 - 4452
(2018/10/17)
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- Method for synthesizing bromo-polycyclic aromatic hydrocarbon compound
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The invention discloses a method for synthesizing bromo-polycyclic aromatic hydrocarbon compounds. The method comprises the following steps: utilizing a polycyclic aromatic hydrocarbon compound shown by a formula I as a substrate, adding base metal bromide into a mixed solution of water and an organic solvent, then slowly adding ZnAl-BrO3--LDHs, reacting for 4 to 8h under 25 to 55 DEG C and treating a reaction mixture by an aftertreatment process to obtain a mono bromo-polycyclic aromatic hydrocarbon compound shown by a formula II or a dual bromo-polycyclic aromatic hydrocarbon compound shown by a formula III after the reaction is finished. A substance amount ratio of the polycyclic aromatic hydrocarbon compound shown by the formula I to the base metal bromide to the ZnAl-BrO3--LDHs is 1 to (0.6 to 1.5) to (0.9 to 1.9). A brominating reagent utilized in the method disclosed by the invention is solid matter and is low in cost, easy to obtain and environmentally friendly. The method has the advantages of moderate reaction condition, convenience in aftertreatment, simpleness in reaction operation, high atom utilization rate, high selectivity, high target product yield and small side reaction. The three formulas are shown in the description.
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Paragraph 0022-0052
(2018/04/01)
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- Zwitterionic-Salt-Catalyzed Site-Selective Monobromination of Arenes
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A zwitterionic-salt-catalyzed electrophilic monobromination of arenes with high regioselectivity has been developed. Under mild reaction conditions, a wide range of monobrominated aromatic compounds can be obtained in excellent yields. The reaction can be operated using an extremely low catalyst loading (0.05 mol %) with the inexpensive brominating agent N-bromosuccinimide. The versatility of this catalytic protocol has been demonstrated by the scale-up reaction with a 0.01 mol % catalyst loading to provide the selectively halogenated compound in quantitative yield.
- Xiong, Xiaodong,Tan, Fei,Yeung, Ying-Yeung
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supporting information
p. 4243 - 4246
(2017/08/23)
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- A gold - {2 - (9 - anthracene phenyl) II cyclohexyl phosphine} - acetonitrile complex synthesis and application of
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The invention relates to a gold metal complex which is [Au{dicyclohexyl-[2-(9-anthracene)phenyl]phosphine}-NCCH3](SbF6), and the gold metal complex can be conveniently synthesized. The ligand can be synthesized in a simple mode, and large scale industrial production can be realized through stable existence of the ligand in air under normal temperature. The gold complex is capable of catalyzing a cycloaddition reaction of 1,6-eneyne, and has good reaction activity. The catalyst has the advantage of less catalyst amount of a traditional metal complex, and overcomes the disadvantage of expensive cost of noble metal catalysts such as Pd and Pt. The reaction is carried out in a dichloromethane system, the catalyst amount is less, reaction condition is mild, reaction time is short, and post-treatment is convenient. The catalyst has important application in the cycloaddition reaction, and has large application prospect in industrial production.
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Paragraph 0035; 0036
(2017/08/25)
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- Asymmetrically twisted anthracene derivatives as highly efficient deep-blue emitters for organic light-emitting diodes
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Deep-blue emission is particularly important for applications of organic light-emitting diodes (OLEDs) in full colour flat-panel displays and solid-state lighting resources. Two asymmetrically twisted anthracene derivatives, 4,5-diphenyl-1,2-bis(4-(10-phenylanthracen-9-yl)phenyl)-1H-imidazole (DPA-PIM) and 1,2-bis(4-(10-phenylanthracen-9-yl)phenyl)-1H-phen-anthro[9,10-d]imidazole (DPA-PPI), for deep-blue OLEDs have been designed and synthesized. The asymmetrically twisted conformations between anthracene and imidazole units in compounds efficiently interrupt molecular π-conjugation and inhibit π-π intermolecular interactions, resulting in high thermal stability and efficient deep-blue emission. The two anthracene derivatives in non-doped OLEDs exhibited blue emission. In particular, the non-doped device based on DPA-PIM achieved an external quantum efficiency (EQE) of 6.5% with CIE coordinates of (0.15, 0.08). In addition, the two emitters in doped devices achieved high EQEs of over 5.0% and much purer blue emission with CIE coordinates of (0.15, 0.06) for DPA-PPI and (0.15, 0.05) for DPA-PIM, which nearly match the CIE coordinates of the European Broadcasting Union (EBU) blue standard of (0.15, 0.06).
- He, Chuanyou,Guo, Haoqing,Peng, Qiming,Dong, Shengzhi,Li, Feng
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supporting information
p. 9942 - 9947
(2015/10/06)
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- Selective Halogenation Using an Aniline Catalyst
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Electrophilic halogenation is used to produce a wide variety of halogenated compounds. Previously reported methods have been developed mainly using a reagent-based approach. Unfortunately, a suitable "catalytic" process for halogen transfer reactions has yet to be achieved. In this study, arylamines have been found to generate an N-halo arylamine intermediate, which acts as a highly reactive but selective catalytic electrophilic halogen source. A wide variety of heteroaromatic and aromatic compounds are halogenated using commercially available N-halosuccinimides, for example, NCS, NBS, and NIS, with good to excellent yields and with very high selectivity. In the case of unactivated double bonds, allylic chlorides are obtained under chlorination conditions, whereas bromocyclization occurs for polyolefin. The reactivity of the catalyst can be tuned by varying the electronic properties of the arene moiety of catalyst.
- Samanta, Ramesh C.,Yamamoto, Hisashi
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supporting information
p. 11976 - 11979
(2015/08/18)
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- Palladacycles promote the base-free homocoupling of arylboronic acids in air at room temperature
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Homocoupling of arylboronic acids can be successfully achieved in commercial grade THF using [Pd(Phbz)(X)(PPh3)] palladacycles as catalysts (Phbz = N-phenylbenzaldimine; X = imidate or acetate). Symmetric biaryls were obtained in good yields working under mild conditions in an air atmosphere at room temperature. The reaction occurs without the addition of an exogenous base. The reaction conditions were optimized to provide the homocoupled products in excellent yield. Evidence for the transmetallation step being important for precatalyst activation has been gathered. The influence of electronic properties of the arylboronic acids on the outcome of the homocoupling reaction has been assessed through competition experiments. This journal is
- Kapdi, Anant R.,Dhangar, Gopal,Serrano, Jose Luis,De Haro, Jose A.,Lozano, Pedro,Fairlamb, Ian J. S.
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p. 55305 - 55312
(2015/02/18)
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- Efficient indium-mediated dehalogenation of aromatics in ionic liquid media
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An efficient indium-mediated dehalogenation reaction of haloaromatics and haloheteroaromatics in ionic liquids has been studied. This method is simple and effective in the presence of [bmim]Br. Furthermore, this methodology is environmentally friendly compared with conventional ones.
- Canete, Alvaro F.,Salas, Cristian O.,Zacconi, Flavia C.
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p. 398 - 407
(2013/03/13)
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- Dynamics of the formation of a charge transfer state in 1,2-bis(9-anthryl)acetylene in polar solvents: Symmetry reduction with the participation of an intramolecular torsional coordinate
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We have studied 1,2-bis(9-anthryl)acetylene as a model compound for the characterization of the process of solvent-mediated symmetry reduction in an excited state. Thanks to the acetylenic bridge that joins the two anthracenic moieties, this system maintains minimal steric hindrance between the end chromophores in comparison with the classic 9,9a?2-bianthryl model compound. The acetylenic bridge also allows for significant electronic coupling across the molecule, which permits a redistribution of electron density after light absorption. Femtosecond resolved fluorescence measurements were used to determine the spectral evolution in acetonitrile and cyclohexane solutions. We observed that, for 1,2-bis(9-anthryl)acetylene, the formation of a charge transfer state occurs in a clear bimodal fashion with well separated time scales. Specifically, the evolution of the emission spectrum involves a first solvent-response mediated subpicosecond stage where the fluorescence changes from that typical of nonpolar solvents (locally excited) to an intermediate, partial charge transfer state. The second stage of the evolution into a full charge transfer state occurs with a much longer time constant of 37.3 ps. Since in this system the steric hindrance is minimized, this molecule can undergo much larger amplitude motions for the torsion between the two anthracenic moieties associated with the charge redistribution in comparison with the typical model compound 9,9a?2-bianthryl. Clearly, the larger range of motions of 1,2-bis(9-anthryl)acetylene gives the opportunity to study the electron transfer process with a good separation of the time scales for the formation of a partial charge transfer state, determined by the speed of solvent response, and the intramolecular changes associated with the formation of the fully equilibrated charge transfer state. ? 2013 American Chemical Society.
- Gutieì?rrez-Arzaluz, Luis,Guarin, Cesar A.,Rodriì?guez-Coì?rdoba, William,Peon, Jorge
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p. 12175 - 12183
(2013/11/06)
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- Dinuclear Pd(i) complexes - Solely precatalysts? Demonstration of direct reactivity of a Pd(i) dimer with an aryl iodide
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This report provides experimental, computational and spectroscopic data in support of the direct reactivity of a Pd(i) dimer with an aryl iodide, resulting in Br/I halogen exchange between the complex and the aryl iodide. The reactivity could not be achieved through analogous Pd(0) conditions, demonstrating the distinct reactivities at such multiple Pd-sites. Computational studies support that the direct oxidative addition to ArI by the dinuclear metal complex is energetically feasible.
- Bonney, Karl J.,Proutiere, Fabien,Schoenebeck, Franziska
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p. 4434 - 4439
(2013/11/19)
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- Aromatic substitution in ball mills: Formation of aryl chlorides and bromides using potassium peroxomonosulfate and NaX
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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)
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- Synthesis and reactivity studies of a new reagent, ethyltriphenylphosphonium tribromide
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A new reagent, ethyltriphenyl phosphonium tribromide (ETPPTB), has been synthesized and studied. Results show that the reagent is quite efficient for various reactions such as organic bominations, acylations, and isothiocyanate preparation. Copyright
- Jamir, Latonglila,Alimenla,Kumar, Anil,Sinha, Dipak,Sinha, Upasana B.
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experimental part
p. 147 - 155
(2011/03/17)
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- Mild persubstitution of di- and tetrabrominated arenes with arylthiolate nucleophiles
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A mild selective protocol was used to prepare tetrakis(2-chlorophenylthio) anthracene from tetrabromoanthracene and sodium 2-chlorobenzenethiolate avoiding the thiolate self-attack. The uncatalyzed nucleophilic substitution of a series of mono-, di-, and tetrabrominated arenes by arylthiolate ions was attempted in mild conditions to investigate the scope of the substitution reaction regarding the size of the aromatic system as well as the number of bromine atoms. Successful reactions afforded only the persubstituted products in good purity and yield after a simple workup and chemoselectivity of Br versus Cl substituents was achieved for the tetrabromide.
- Del Rosso, Pablo G.,Almassio, Marcela F.,Bruno, Mattia,Garay, Raúl O.
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supporting information; body text
p. 6730 - 6733
(2011/02/25)
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- Oxidative bromination reaction using Cu2+- perfluorophthalocyanine-immobilized silica gel catalyst under mild reaction conditions
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A simplified, facile route has been applied for the grafting of copper(II) perfluorophthalocyanine complex onto functionalized silica gel. The resulting organic-inorganic hybrid material is used as an efficient and recyclable catalyst for the regioselective oxidative bromination of various aromatic substrates using KBr/H2O2 as the reagents, affording high yields under mild conditions. High catalytic activity efficiency could be attributed to the heterogenization of soluble metal complexes on the high surface area host.
- Sharma,Sharma, Chetna
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experimental part
p. 4415 - 4418
(2010/09/20)
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- Green synthesis of tetraalkylammonium tribromide using cerium(IV) ammonium nitrate (CAN) as oxidant
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Cerium(IV) ammonium nitrate (CAN) mediates oxidation of tetraalkylammonium bromide to tetraalkylammonium tribromide in greener reaction conditions using water as solvent. The procedure is simple, convenient, and environmentally benign for the synthesis of tetraalkylammonium tribromide with great yields. Copyright Taylor & Francis Group, LLC.
- Borah, Ruli,Thakur, Ashim Jyoti
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p. 933 - 939
(2007/10/03)
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- Pd-catalyzed reduction of aryl halides using dimethylformamide as the hydride source
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The Pd-catalyzed homocoupling of aryl halides in a basic DMF solution is often accompanied by the dehalogenation of the substrate as side reaction. When an inorganic base such as sodium bicarbonate is used, the reducing role of the solvent has been demonstrated using DMF-d7 and GC/MS analysis.
- Zawisza, Anna Maria,Muzart, Jacques
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p. 6738 - 6742
(2008/02/13)
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- Mild and regioselective bromination of aromatic compounds with N,N,N′,N′-Tetrabromobenzene-1,3-disulfonylamide and poly(N-bromobenzene-1,3-disulfonylamide)
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N,N,N′,N′-Tetrabromobenzene-1,3-disulfonylamide (TBBDA) and poly[N-bromobenzene-1,3-disulfonylamide] (PBBS) can be used for the regioselective bromination of aromatic compounds in excellent yields under mild conditions.
- Ghorbani-Vaghei, Ramin,Jalili, Hamid
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p. 1099 - 1102
(2007/10/03)
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- A new method for the oxybromination of aromatic compounds with copper(II)bromide and potassium dichromate
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A new and mild method for oxybromination of aromatic compounds with CuBr2 and K2Cr2O7 in HOAC is reported. Copyright Taylor & Francis Inc.
- Badri, Rashid,Shushizadeh, Mohammad Reza
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p. 533 - 536
(2007/10/03)
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- Regioselective synthesis of para-bromo aromatic compounds
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Reaction of substituted benzenerings with N-bromophthalimide, underneutral conditions, gave the corresponding bromo derivatives with a preference for the formation of the para bromoisomer over the ortho isomer. The sim pie work-up procedure minimizes loss of product and the yields are good.
- Khazaei, Ardeshir,Manesh, Abbas Amini,Safi, Vahid Reza
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p. 559 - 562
(2007/10/03)
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- Synthesis of unsymmetric anthracene compounds
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A process for forming an unsymmetric anthracene compound comprises a first step of forming a 9-perfluoroalkylsulfonate derivative of anthrone by reacting the anthrone with a perfluoroalkyl sulfonating agent, followed by a second step of contacting the reaction product with an aryl or heteroaryl boronic acid, ester or anhydride, and a palladium catalyst for a period of time sufficient to form an unsymmetric anthracene compound having at least one 9-position aromatic substituent.
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Page/Page column 8
(2010/02/14)
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- Environmentally benign chlorination and bromination of aromatic amines, hydrocarbons and naphthols
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A simple and efficient procedure for chlorination and bromination of aromatic amines, hydrocarbons and naphthols by the action of aqueous hydrohalic acid and hydrogen peroxide is described. This environmentally clean and safe procedure involves in situ generation of the active halogen and its uncatalyzed reaction with the substrates in this study.
- Vyas, Punita V.,Bhatt, Anjani K.,Ramachandraiah, Gadde,Bedekar, Ashutosh V.
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p. 4085 - 4088
(2007/10/03)
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- Regioselective bromination of organic substrates by tetrabutylammonium bromide promoted by V2O5-H2O2: An environmentally favorable synthetic protocol
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(matrix presented) Vanadium pentoxide very effectively promotes the bromination of organic substrates, including selective bromination of some aromatics, by tetrabutylammonium bromide in the presence of hydrogen peroxide; mild conditions, high selectivity, yield, and reaction rate, and redundancy of bromine and hydrobromic acid are some of the major advantages of the synthetic protocol.
- Bora, Upasana,Bose, Gopal,Chaudhuri, Mihir K.,Dhar, Siddhartha S.,Gopinath, Rangam,Khan, Abu T.,Patel, Bhisma K.
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p. 247 - 249
(2007/10/03)
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- Halogenations of Anthracenes and Dibenz[a,c]anthracene with N-Bromosuccinimide and N-Chlorosuccinimide
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Halogenation of dibenz[a,c]anthracene (1) by NBS in CCl4 affords the products of 9- and 10-monobromination in the ratio of 9:1. The reaction is accelerated by iodine, and HBr effects rearrangement of 9-bromo product to the sterically less crowded 10-bromo isomer. The mechanism is proposed to involve reversible addition of Br2, followed by elimination of HBr. Reaction of NCS with 1 in CCl4 requires addition of HCl and affords exclusively 9-chlorination. The different reactivities of NBS and NCS are ascribed to the relative amounts of free halogen produced (due to differences in N-X bond strengths involving Br and Cl), and the different sizes of the halogens. Under similar conditions, NCS chlorinates 9-bromoanthracene (2a) to afford 9,10-dichloroanthracene and 9-bromo-10-chloroanthracene in the ratio of 65:35. This reaction ostensibly occurs by addition of Cl2 to 2a, followed by preferential loss of HBr rather than HCl. 9-Methylanthracene (3) affords exclusively 9-(bromomethyl)anthracene with NBS in the absence of iodine, but mainly (67%) 9-bromo-10-methylanthracene in the presence of iodine. Chlorination of 3 with NCS in the presence of HCl also affords mostly (65%) nuclear halogenation. Nuclear bromination of anthracene, 9-methylanthracene, and dibenz[a,c]anthracene by NBS in the absence of added HBr is accelerated by iodine. This effect is probably due to an increase in the amount of bromine produced from NBS in the presence of iodine.
- Duan, Shaoming,Turk, Jeff,Speigle, Joseph,Corbin, Jean,Masnovi, John,Baker, Ronald J.
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p. 3005 - 3009
(2007/10/03)
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- An environmentally benign synthesis of organic ammonium tribromides (OATB) and bromination of selected organic substrates by tetrabutylammonium tribromide (TBATB)
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Stable crystalline organic ammonium tribromides (OATB), like Me4NBr3, Et4NBr3, Bu4NBr3, cetyltrimethylammonium tribromide, PyHBr3, can be readily synthesised from the reaction of the corresponding bromides with V2O5 and aqueous H2O2. Typically, TBATB, Bu4NBr3, brominates a variety of organic substrates rather easily under mild conditions. An activated aromatic ring is selectively brominated in the presence of an olefinic double bond.
- Chaudhuri, Mihir K.,Khan, Abu T.,Patel, Bhisma K.,Dey, Deepa,Kharmawophlang, Wancydora,Lakshmiprabha,Mandal, Gagan C.
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p. 8163 - 8166
(2007/10/03)
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- Iodine Cyanide Promoted Iodination of Aromatic Compounds. A Simple Synthesis of 1-Iodopyrene
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A simple method for the iodination of reactive aromatic compounds, using ICN in the presence of a Lewis acid as the source of iodine, is presented. 1-Iodopyrene is obtained in 81percent isolated yield from the reaction of pyrene and ICN with AlCl3 in CH3NO2/(C2H5)2O.Anthracene undergoes partial chlorination in the presence of AlCl3, but with BF3, 9-iodoanthracene is obtained in 48percent isolated yield.
- Radner, Finn
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p. 481 - 484
(2007/10/02)
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- Electron Transfer Activation in the Thermal and Photochemical Osmylation of Aromatic EDA Complexes with Osmium(VIII) Tetroxide
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Various types of arenes (Ar) spontaneously form with osmium tetroxide a series of highly colored solutions of electron donor-acceptor or EDA complexes such as in nonpolar solvents.Charge-transfer or CT osmylation is simply effected by the actinic irradiation of the absorption bands (hνCT), and the molecular structures of the OsO4 adducts of benzene (B) and anthracene (A) are elucidated by X-ray crystallography.The metastable ion pair is established as the seminal intermediate in CT osmylation by time-resolved picosecond spectroscopy attendant upon the specific excitation of the EDA complex.According to Scheme II, the rapid collapse of the ion pair (eq 16) with a rate constant k ca. 1E9 s-1 represents the critical transformation in adduct formation.Importantly, this ion-pair mechanism accomodates (a) the osmylation of a wide range of arene donors from the mononuclear benzenes to the electron-rich polycyclic arenes (Table V) under the common umbrella of photoexcitation and (b) the profound effect on the regiochemistry of anthracene (Table VI) by subtle variations in solvent polarity.In the absence of deliberate irradiation (i.e., in the dark), the EDA complexes of OsO4 with electron-rich arenes, especially the polynuclear naphthalene, anthracene and phenanthrene, slowly undergo the direct thermal or DT osmylation to yield the same series of adducts.As such, there is a close relationship between the photoexcited state leading to CT osmylation and the activated complex in DT osmylation.Indeed the formation of the highly unusual adduct A by OsO4 addition to the terminal ring of anthracene binds in common the transition state for DT osmylation and the ion-pair collapse in CT osmylation.Thus the electron-transfer mechanism in Scheme IV employs the adiabatic ion pair (eq 20) to account for the same regiospecificities in DT osmylations.Such a unified view of arene osmylation can be extended to the promoted thermal or PT osmylation via the five-coordinate OsO4(py), as a commonly practiced for bis-hydroxylation of alkenes.
- Wallis, J. M.,Kochi, J. K.
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p. 8207 - 8223
(2007/10/02)
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- Photochemical Debromination of Meso-Substituted Bromoanthracenes Studied by Steady-State Photolysis and Laser Photolysis
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Debrominations of 9-bromoanthracene (BA) and 9,10-dibromoanthracene (DBA) in acetonitrile containing triethylamine (TEA) or N,N-dimethylaniline (DMA) have been studied by means of steady-state photolysis and laser photolysis.By the addition of TEA, the decay constants of the lowest excited singlet states of BA and DBA increase and the maximum yields of the triplet states decrease.The singlet quenching rate constants by TEA are calculated to be of the order of 1E10 M-1 s-1, showing that the reactions are diffusion controlled.Compared with the result of γ-radiolysis and pulse radiolysis, it is suggested that the photochemical debrominations of BA and DBA in the presence of amines take place via the anion radicals which are produced through exciplexes between amines and the lowest excited singlet states of bromoanthracenes.
- Hamanoue, Kumao,Tai, Shigeyoshi,Hidaka, Toshiharu,Nakayama, Toshihiro,Kimoto, Masaki,Teranishi, Hiroshi
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p. 4380 - 4384
(2007/10/02)
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- Magnesium-μ-(9,10-dihydro-9,10-anthrylene)-aluminates; Complexes of "Anthracenemagnesium"
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The relatively insoluble "anthracenemagnesium" 1a*n THF reacts in THF with dialkylaluminium hydrides to give magnesium-μ-(9,10-dihydro-9,10-anthrylene)-dialkylhydridoaluminates 2a-c, with aluminium trihydride the corresponding -trihydridoaluminate 2d and with ethoxydiethylaluminium the -ethoxydiethylaluminate 6.The structures of the compounds 2a-c and 6 dissolved in THF were determined by NMR spectroscopy.An X-ray crystallographic investigation of 2b (alkyl = ethyl) shows that Al and Mg occupy axial positions in a 9,10-dihydro-9,10-anthrylene system.The Mg+ cation interacts with the hydride of the aluminate anion.Analogous complexes 3 with trialkylaluminium can only be obtained if 1a*n THF is reacted with (n+1) AlR3 (R = methyl, ethyl) in non-Lewis base solvents.Ether cause the cleavage of 3 into trialkylaluminium etherate, e.g. 4 or 5, and 1a, which is unstable in diethyl ether and decomposes into magnesium and anthracene.
- Lehmkuhl, Herbert,Mehler, Klaus,Benn, Reinhard,Rufinska, Anna,Schroth, Gerhard,Krueger, Carl
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p. 389 - 403
(2007/10/02)
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- Carbon-13 NMR Spectroscopic Study of Substituted Anthracene Dications
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A series of substituted anthracenes (2-10 and 20-21) were oxidized by SbF5/SO2ClF at 0 to -30 deg C to their dications (11-19 and 22-23), which were observed by carbon-13 NMR spectroscopy.In the studied anthracene dications substantial positive charge was found to be localized at C9 and C10 positions.Methyl substitution in these dications was found to deshield the α-carbons as compared to their shielding effect in the corresponding monocations.The proportionality factor of (13)C chemical shift to electron density was found to be 174.1-217.0 ppm/e-, clearly proving the dicationic nature of the ions.
- Olah, George A.,Singh, Brij P.
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p. 4830 - 4835
(2007/10/02)
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- COMPETITION ENTRE SUBSTITUTION NULCEOPHILE ET REDUCTION CHEZ LES BROMO-9 ANTHRACENES DANS L'ACTION DES ANIONS PHENATE ET METHYLATE; APPLICATION A LA MONO-DEUTERIATION SPECIFIQUE EN MESO EN SERIE ANTHRACENIQUE
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Treatment of meso-substituted 9-bromoanthracenes bearing no hydrogen in the α position with potassium phenoxide in DMF gives rise to a competition between nucleophilic substitution and reductive dehalogenation.Derivatives carrying electron attracting groups, 1c (Br), 1e (CN) and 1f (NO2), react essentially by substitution leading to phenolic ethers 2, whereas with non-activated bromides, 1a (H), 1b (C6H5) and 1d (OC6H5), the main reaction is a reduction to anthracenes 3 which should arise from an electron transfer.A reduction of 9-bromoanthracene into anthracene is also observed with sodium methoxide and it is shown, by labelling, that this one must result from a hydride transfer from methoxide.It may be applied to the specific meso-monodeuterization of various anthracenic derivatives.
- Rigaudy, J.,Seuleiman, A.M.,Cuong, Nguyen Kim
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p. 3157 - 3162
(2007/10/02)
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- Photochemical Reactions of Bromoanthracenes with N,N-Dimethylaniline in Solution
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Major products of the photolysis of 9-bromoanthracene and 9,10-dibromoanthracene in benzene and acetonitrile as well as photochemical reaction products of the two bromoanthracenes with N,N-dimethylaniline in these solvents have been isolated and identified.The mechanisms of partial reactions are discussed and attention is paid to the medium effect on the photochemical transformations. - Keywords: Photochemical Reactions, Bromoanthracenes
- Fulara, Jan,Latowski, Tadeusz
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p. 846 - 851
(2007/10/02)
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