- The phenyl vinyl ether–methanol complex: A model system for quantum chemistry benchmarking
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The structure of the isolated aggregate of phenyl vinyl ether and methanol is studied by combining a multi-spectroscopic approach and quantum-chemical calculations in order to investigate the delicate interplay of noncovalent interactions. The complementa
- Bernhard, Dominic,Dietrich, Fabian,Fatima, Mariyam,Pérez, Cristóbal,Gottschalk, Hannes C.,Wuttke, Axel,Mata, Ricardo A.,Suhm, Martin A.,Schnell, Melanie,Gerhards, Markus
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Read Online
- Enhanced bulk catalyst dissolution for self-healing materials
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A model was developed to aid in the selection of healing monomers that can rapidly dissolve catalysts in self-healing materials. Predictions are made regarding dissolution rates of Grubbs' catalyst in a small library of ring-opening metathesis polymerizat
- Mauldin, Timothy C.,Kessler, Michael R.
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Read Online
- Synthesis of vinyl phenyl ether and its use for ammetric titration of silver(I)
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Catalytic vinylation of phenol with acetylene at atmospheric pressure was studied. The yield of vinyl phenyl ether was determined as influenced by the solvent, reaction temperature, and catalyst amount. The mechanism of formation of vinyl phenyl ether was proposed. Ammetric titration of silver(I) with a solution of vinyl phenyl ether in nonaqueous acetic acid solutions was performed.
- Nurmanov,Gevorgyan,Matmuratov,Kasimova,Sirlibaev,Kalyadin
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Read Online
- Reductive C-O, C-N, and C-S Cleavage by a Zirconium Catalyzed Hydrometalation/β-Elimination Approach
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A zirconium catalyzed reductive cleavage of Csp3 and Csp2 carbon-heteroatom bonds is reported that makes use of a tethered alkene functionality as a traceless directing group. The reaction is successfully demonstrated on C-O, C-N, and C-S bonds and proposed to proceed via a hydrozirconation/β-heteroatom elimination sequence of an in situ formed zirconium hydride catalyst. The positional isomerization of the catalyst further enables the cleavage of homoallylic ethers and the removal of terminal allyl and propargyl groups.
- Matt, Christof,K?lblin, Frederic,Streuff, Jan
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supporting information
p. 6983 - 6988
(2019/09/09)
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- Reusable rhodium catalyst for the selective transvinylation of sp2-C linked carboxylic acid
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The vinyl benzoate derivatives were successfully synthesized by the transvinylation reactions that vinyl group transferred from vinyl acetate to aromatic carboxylic acids with the recoverable catalyst RhCl3·3H2O. This catalyst features air stable and tolerance of water, good reusable ability, meanwhile, shows high selectivity for aromatic carboxylic acid in the presence of phenolic hydroxyl. With this method, a variety of vinyl benzoate derivatives can be produced with up to 95% yield.
- Jiang, Ruihang,Chen, Zhangpei,Zhan, Kun,Liu, Lei,Zhou, Junjie,Ai, Yongjian,Li, Shuang,Bao, Hongjie,Hu, Ze'nan,Qi, Li,Wang, Jingting,Sun, Hong-bin
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p. 3279 - 3282
(2018/07/21)
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- Vinylation of Aryl Ether (Lignin Β-O-4 Linkage) and Epoxides with Calcium Carbide through C?O Bond Cleavage
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Calcium carbide has been increasingly used as a sustainable, easy-to-handle, and low-cost feedstock in organic synthesis. Currently, methodologies of using calcium carbide as “solid acetylene” in synthesis are strictly limited to activation and reaction w
- Teong, Siew Ping,Lim, Jenny,Zhang, Yugen
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p. 3198 - 3201
(2017/09/02)
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- Direct vinylation of natural alcohols and derivatives with calcium carbide
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Vinyl ethers are essential synthetic building blocks for organic synthesis, especially for polymer synthesis and highly vinylated polyol substrates. Herein, a transition metal-free, mild, and safe protocol has been developed for direct vinylation of natural alcohols with calcium carbide. Various sugar alcohols, phenol and its derivatives were tested and proved successful using this green methodology. Selectivity of full vinylated products of the reaction decreases with increasing hydroxyl groups because of side reactions occurring under the basic medium. Electron-donating substituted phenols work more efficiently than electron-withdrawing substituted phenols in general. This methodology may provide new insights on selective vinylation of electron-rich biomass-derived materials.
- Teong, Siew Ping,Chua, Ariel Yi Hui,Deng, Shiyun,Li, Xiukai,Zhang, Yugen
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supporting information
p. 1659 - 1662
(2017/06/07)
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- A solid acetylene reagent with enhanced reactivity: Fluoride-mediated functionalization of alcohols and phenols
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The direct vinylation of an OH group in alcohols and phenols was carried out utilizing a novel CaC2/KF solid acetylene reagent in a simple K2CO3/KOH/DMSO system. The functionalization of a series of hydroxyl-group-containing substrates and the post-modification of biologically active molecules were successfully performed using standard laboratory equipment, providing straightforward access to the corresponding vinyl ethers. The overall process developed involves an atom-economical addition reaction employing only inorganic reagents, which significantly simplifies the reaction set-up and the isolation of products. A mechanistic study revealed a dual role of the F- additive, which both mediates the surface etching/renewal of the calcium carbide particles and activates the CC bond towards the addition reaction. The development of the fluoride-mediated nucleophilic addition of alcohols eliminates the need for strong bases and may substantially extend the areas of application of this attractive synthetic methodology due to increasing functional group tolerance. As a replacement for dangerous and difficult to handle high-pressure acetylene, we propose the solid reagent CaC2/KF, which is easy to handle, does not require dedicated laboratory equipment and demonstrates enhanced reactivity of the acetylenic triple bond. Theoretical calculations have shown that fluoride-mediated activation of the hydroxyl group towards nucleophilic addition significantly reduces the activation barrier and facilitates the reaction.
- Werner, Georg,Rodygin, Konstantin S.,Kostin, Anton A.,Gordeev, Evgeniy G.,Kashin, Alexey S.,Ananikov, Valentine P.
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supporting information
p. 3032 - 3041
(2017/07/24)
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- Heterogeneous Gold-Catalyzed Selective Semireduction of Alkynes using Formic Acid as Hydrogen Source
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A convenient and robust protocol for the selective transfer semireduction of alkynes was developed, using bio-renewable formic acid as the hydrogen source and easily handled supported gold nanoparticles as the catalyst. The catalytic system showed several attractive features such as high activity and selectivity, recyclability, scalability and adaptability to continuous operation under mild reaction conditions, thus providing a practical alternative to current methods for alkyne semireduction.
- Li, Shu-Shuang,Tao, Lei,Wang, Fu-Ze-Rong,Liu, Yong-Mei,Cao, Yong
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supporting information
p. 1410 - 1416
(2016/05/19)
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- Coupling Reaction of Enol Derivatives with Silyl Ketene Acetals Catalyzed by Gallium Trihalides
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A cross-coupling reaction between enol derivatives and silyl ketene acetals catalyzed by GaBr3took place to give the corresponding α-alkenyl esters. GaBr3showed the most effective catalytic ability, whereas other metal salts such as BF3?OEt2, AlCl3, PdCl2, and lanthanide triflates were not effective. Various types of enol ethers and vinyl carboxylates as enol derivatives are amenable to this coupling. The scope of the reaction with silyl ketene acetals was also broad. We successfully observed an alkylgallium intermediate by using NMR spectroscopy, suggesting a mechanism involving anti-carbogallation among GaBr3, an enol derivative, and a silyl ketene acetal, followed by syn-β-alkoxy elimination from the alkylgallium. Based on kinetic studies, the turnover-limiting step of the reaction using a vinyl ether and a vinyl carboxylate involved syn-β-alkoxy elimination and anti-carbogallation, respectively. Therefore, the leaving group had a significant effect on the progress of the reaction. Theoretical calculations analysis suggest that the moderate Lewis acidity of gallium would contribute to a flexible conformational change of the alkylgallium intermediate and to the cleavage of the carbon?oxygen bond in the β-alkoxy elimination process, which is the turnover-limiting step in the reaction between a vinyl ether and a silyl ketene acetal.
- Nishimoto, Yoshihiro,Kita, Yuji,Ueda, Hiroki,Imaoka, Hiroto,Chiba, Kouji,Yasuda, Makoto,Baba, Akio
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supporting information
p. 11837 - 11845
(2016/08/05)
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- Nucleophilic addition to acetylenes in superbasic catalytic systems: XVIII. Vinylation of phenols and naphthols with acetylene
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Phenols and naphthols react with acetylene in a superbasic system KOH-DMSO forming the corresponding aryl vinyl ethers in up to 80% yields.
- Trofimov,Oparina,Kolyvanov,Vysotskaya,Gusarova
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p. 188 - 194
(2015/04/14)
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- A method of manufacturing an aromatic vinyl ether
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[Problem] To provide a method for producing an aromatic vinyl ether, which can overcome disadvantages of the conventional techniques and can produce aromatic vinyl ethers having various structures safely using a simple apparatus without using any expensive catalyst. [Solution] This method for producing an aromatic vinyl ether is characterized by comprising heating an aromatic vinyl ether (1) that has such a structure that a hydrogen atom in a phenolic hydroxy group is substituted by a vinyloxyethyl group and is represented by formula (1) (wherein R represents a residue of a phenol having n phenolic hydroxy groups; and n represents an integer of 1 to 3) without any solvent or in an aprotic polar solvent in the presence of an alkali metal compound to thereby convert the aromatic vinyl ether (1) into an aromatic vinyl ether (2) that has such a structure that a hydrogen atom in a phenolic hydroxy group is substituted by a vinyl group and is represented by formula (2) (wherein R and n are as defined above).
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Paragraph 0080; 0086
(2016/12/16)
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- Diarylrhodates as promising active catalysts for the arylation of vinyl ethers with grignard reagents
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Anionic diarylrhodium complexes, generated by reacting [RhCl(cod)] 2 with 2 equiv of aryl Grignard reagents, were found to be effective active catalysts in cross-coupling reactions of vinyl ethers with aryl Grignard reagents, giving rise to the production of vinyl arenes. In this catalytic system, vinyl-O bonds were preferably cleaved over Ar-O or Ar-Br bonds. A lithium rhodate complex was isolated, and its crystal structure was determined by X-ray crystallography.
- Iwasaki, Takanori,Miyata, Yoshinori,Akimoto, Ryo,Fujii, Yuuki,Kuniyasu, Hitoshi,Kambe, Nobuaki
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supporting information
p. 9260 - 9263
(2014/07/21)
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- Three-component reaction between vinyl ethers, secondary phosphines, and elemental selenium: One-pot synthesis of 1-(Alkoxy)ethyl and 1-(Aryloxy)ethyl phosphinodiselenoates
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A family of previously unknown phosphinodiselenoic esters containing a selenoacetal moiety, R2(=Se)SeCH(Me)OR1 (R1, R2=alkyl, aryl, etc.), were synthesized by means of a three-component reaction between the elem
- Gusarova, Nina K.,Artemev, Alexander V.,Oparina, Ludmila A.,Kolyvanov, Nikita A.,Malysheva, Svetlana F.,Vysotskaya, Oksana V.,Trofimov, Boris A.
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experimental part
p. 431 - 438
(2012/03/11)
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- Solid-phase organic synthesis of aryl vinyl ethers using sulfone-linking strategy
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A novel facile solid-phase organic synthesis of aryl vinyl ethers by reaction of polystyrene-supported 2-phenylsulfonylethanol with phenols under Mitsunobu conditions and subsequent elimination reaction with DBU has been developed. The advantages of this method include straightforward operation, good yield and high purity of the products. Alternatively, a typical example of Suzuki coupling reaction on-resin was further applied to prepare 4-phenylphenyl vinyl ether for extending this method.
- Yu, Lamei,Tang, Ni,Sheng, Shouri,Chen, Rubing,Liu, Xiaoling,Cai, Mingzhong
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experimental part
p. 1027 - 1030
(2012/07/28)
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- Gallium tribromide catalyzed coupling reaction of alkenyl ethers with ketene silyl acetals
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A 'Ga'llant couple: The α-alkenylation of esters was accomplished by GaBr3-catalyzed coupling between alkenyl ethers and ketene silyl acetals. In this reaction system, various alkenyl ethers, including those with vinyl and substituted alkenyl groups, were applicable, and the scope of applicable ketene silyl acetals was sufficiently broad. The mechanism is also discussed. Copyright
- Nishimoto, Yoshihiro,Ueda, Hiroki,Yasuda, Makoto,Baba, Akio
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supporting information; experimental part
p. 8073 - 8076
(2012/08/29)
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- Synthesis of 4-amino-4,5-dideoxy-L-lyxofuranose derivatives and their evaluation as fucosidase inhibitors
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The nitrone 4 (4,5-dideoxy-4-hydroxylamino-3,4-O-isopropylidene-L- lyxofuranose) was synthesised from d-ribose and used as key intermediate for the preparation of fucosidase inhibitors. We describe two transformations of 4. Hydrolysis with aqueous sulfur
- Chevrier, Carine,Le Nou?n, Didier,Defoin, Albert,Tarnus, Céline
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experimental part
p. 1202 - 1211
(2011/07/09)
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- Solid-Phase synthesis of aryl vinyl ethers based on polystyrenesupported aβ-phenylselenoethanol
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A novel facile solid-phase organic synthesis of aryl vinyl ethers by reaction of polystyrene-supported β-phenylselenoethanol with phenols under Mitsunobu conditions and subsequent oxidation-elimination with 30% hydrogen peroxide has been developed. The ad
- Zhang, Jia-Li,Sheng, Shou-Ri,Liub, Xue,Lin, Shu-Ying
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experimental part
p. 287 - 289
(2010/02/28)
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- β-Phenylselenoethanol, an efficient reagent for the one-pot synthesis of aryl vinyl ethers
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β-Phenylselenoethanol was treated with phenols under Mitsunobu conditions and subsequent oxidation-elimination with 30% hydrogen peroxide furnished aryl vinyl ethers with good yields (85-90%) in a one-pot, two-step transformation.
- Fu, Gui-Yun,Yu, La-Mei,Mao, Xue-Chun,Wu, Dan
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experimental part
p. 595 - 597
(2009/10/15)
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- Catalytic dehydrogenation of o-alkylated or o-alkoxylated iodoarenes with concomitant hydrogenolysis
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Palladium-catalyzed dehydrogenation of suitable chains bonded to an ortho position of an iodoarene has been achieved by two methods both involving oxidative addition of the iodoarene to palladium(0) and palladacycle formation under mild conditions.
- Motti, Elena,Catellani, Marta
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experimental part
p. 565 - 569
(2009/05/07)
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- Au(I) complexes-catalyzed transfer vinylation of alcohols and carboxylic acids
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Au(I) complexes-catalyzed transfer vinylation of alcohols and carboxylic acids has been achieved. The catalyst system consists of 2 mol % AuClPPh3 and 2 mol % AgOAc. Primary alcohols and secondary alcohols were converted into corresponding vinyl ethers in good yield (64-93%); however, tertiary alcohols showed poor reactivities. Carboxylic acids were also transformed into corresponding vinyl esters in good yield (78-96%).
- Nakamura, Aki,Tokunaga, Makoto
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p. 3729 - 3732
(2008/09/20)
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- Polymer-supported β-bromoethyl selenide: An efficient reagent for the synthesis of aryl vinyl ethers
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A simple and efficient procedure for the solid-phase synthesis of aryl vinyl ethers using polymer-supported β-bromoethyl selenide with traceless linker strategy is described.
- Sheng, Shou-Ri,Liu, Xiao-Ling,Wang, Xing-Cong,Xin, Qin,Song, Cai-Sheng
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p. 2833 - 2836
(2007/10/03)
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- Decomposition of vinyl ethers by alkalide K- K+ (15-crown-5)2 via organopotassium intermediates
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The structure of vinyl ethers determines the direction of the C-O bond cleavage by alkalide K-, K+(15-crown-5)2 1. Highly reactive organopotassium compounds are intermediate products formed in the system containing phenyl vinyl ether, butyl vinyl ether, ethylene glycol butyl vinyl ether or triethylene glycol methyl vinyl ether. Vinylpotassium and butylpotassium react with 15-crown-5. The oxacyclic ring of the latter is opened in this case. Organopotassium ethers possessing CH2CH2O units eliminate ethylene. It results in various potassium alkoxides. The reaction of 1 with butyl vinyl ether occurs very slow as compared to other vinyl ethers and most of other reagents used till now.
- Grobelny, Zbigniew,Stolarzewicz, Andrzej,Maercker, Adalbert,Krompiec, Stanis,Kasperczyk, Janusz,Rzepa, Józef
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p. 1580 - 1585
(2007/10/03)
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- Process for producing vinyl ether compounds
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A process produces vinyl ether compounds and includes allowing a vinyl ester compound represented by following Formula (1): 1wherein R1, R2, R3 and R4 are the same or different and are each a hydrogen atom or an organic group, to react with a hydroxy compound represented by following Formula (2):R5OH??(2)wherein R5 is an organic group, in the presence of at least one transition element compound to thereby yield a vinyl ether compound represented by following Formula (3): 2wherein R2, R3, R4 and R5 have the same meanings as defined above. Such transition element compounds include iridium compounds and other compounds containing Group VIII elements.
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- Mechanism and structure-reactivity correlation in the homogeneous, unimolecular elimination kinetics of 2-substituted ethyl methylcarbonates in the gas phase
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The gas-phase elimination kinetics of 2-substituted ethyl methylcarbonates were determined in a static reaction system over the temperature range of 323-435 °C and pressure range 28.5-242 Torr. The reactions are homogeneous, unimolecular and follow a first-order rate law. The kinetic and thermodynamic parameters are reported. The 2-substituents of the ethyl methylcarbonate (CH3OCOOCH2CH2Z, Z = substituent) give an approximate linear correlation when using the Taft-Topsom method, log(k z/kH)= -(0.57 ± 0.19)σα + (1.34 ± 0.49)σR (r = 0.9256; SD = 0.16) at 400 °C. This result implies the elimination process to be sensitive to steric factors, while the electronic effect is unimportant. However, the resonance factor has the greatest influence for a favorable abstraction of the β-hydrogen of the C3- H bond by the oxygen carbonyl. Because ρα is significant, a good correlation of the alkyl substituents of carbonates with Hancock's steric parameters was obtained: log(kR/kH versus Esc for CH 3OCOOCH2CH2R at 400°C, R = alkyl, δ= -0.17 (r=0.9993, SD = 0.01). An approximate straight line was obtained on plotting these data with the reported Hancock's correlation of 2-alkyl ethylacetates. This result leads to evidence for the β-hydrogen abstraction by the oxygen carbonyl and not by the alkoxy oxygen at the opposite side of the carbonate. The carbonate decompostion is best described in terms of a concerted six-membered cyclic transition state type of mechanism. Copyright
- Chuchani, Gabriel,Marquez, Edgar,Herize, Armando,Dominguez, Rosa Maria,Tosta, Maria,Brusco, Doris
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p. 839 - 848
(2007/10/03)
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- Flash vacuum pyrolysis over magnesium. Part 1 - Pyrolysis of benzylic, other aryl/alkyl and aliphatic halides
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Flash vacuum pyrolysis over a bed of freshly sublimed magnesium on glass wool results in efficient coupling of benzyl halides to give the corresponding bibenzyls. Where an ortho halogen substituent is present further dehalogenation gives some dihydroanthracene and anthracene. Efficient coupling is also observed for halomethylnaphthalenes and halodiphenylmethanes while chlorotriphenylmethane gives 4,4′-bis(diphenylmethyl)biphenyl. By using α,α′-dihalo-o-xylenes, benzocyclobutenes are obtained in good yield, while the isomeric α,α′-dihalo-p-xylenes give a range of high thermal stability polymers by polymerisation of the initially formed p-xylylenes. Other haloalkylbenzenes undergo largely dehydrohalogenation where this is possible, in some cases resulting in cyclisation. Deoxygenation is also observed with haloalkyl phenyl ketones to give phenylalkynes as well as other products. With simple alkyl halides there is efficient elimination of HCl or HBr to give alkenes. For aliphatic dihalides this also occurs to give dienes but there is also cyclisation to give cycloalkanes and dehalogenation with hydrogen atom transfer to give alkenes in some cases. For 5-bromopent-1-ene the products are those expected from a radical pathway but for 6-bromohex-1-ene they are clearly not. For 2,2-dichloropropane and 1,1-dichloropropane elimination of HCl occurs but for 1,1-dichlorobutane, -pentane and -hexane partial hydrolysis followed by elimination of HCl gives E, E-, E,Z- and Z,Z- isomers of the dialk-1-enyl ethers and fully assigned 13C NMR data are presented for these. With 6-chlorohex-1-yne and 7-chlorohept-1-yne there is cyclisation to give methylenecycloalkanes and -cycloalkynes. The behaviour of 1,2-dibromocyclohexane and 1,2-dichlorocyclooctane under these conditions is also examined. Various pieces of evidence are presented that suggest that these processes do not involve generation of free gas-phase radicals but rather surface-adsorbed organometallic species.
- Aitken, R. Alan,Hodgson, Philip K.G.,Morrison, John J.,Oyewale, Adebayo O.
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p. 402 - 415
(2007/10/03)
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- An experimental and computational evaluation of the energetics of the isomeric methoxyphenylcarbenes generated in carbon atom reactions
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Carbon atom reactions with anisole and methoxybenzaldehyde demonstrate the reversible ring expansion of methoxyphenylcarbene (CH3O-C6H4-C-H). Trapping with HBF4 yields the methoxytropylium ion, analogous to the
- Geise, C. Michael,Hadad, Christopher M.,Zheng, Fengmei,Shevlin, Philip B.
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p. 355 - 364
(2007/10/03)
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- Development of a highly efficient catalytic method for synthesis of vinyl ethers
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A new method for the preparation of alkyl vinyl ethers has been developed. Thus, various types of alkyl vinyl ethers were synthesized by the reaction of alcohols with vinyl acetate under the influence of a catalytic amount of [Ir(cod)Cl]2 combined with Na2CO3 in good to excellent yields. Copyright
- Okimoto, Yoshio,Sakaguchi, Satoshi,Ishii, Yasutaka
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p. 1590 - 1591
(2007/10/03)
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- Intramolecular triplet energy transfer in flexible molecules: Electronic, dynamic, and structural aspects
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Exothermic intramolecular triplet energy transfer (TET) rate constants in various flexible bichromophoric systems D-(CH2)n-O-A (D = benzoyl, 4-methylbenzoyl; A = 2-naphthyl, 4-, 3-, 2-biphenyl; n = 3-14) have been determined from steady-state quenching and quantum yield measurements. The magnitude of the rate constants in molecules where n = 3 is comparable to those in molecules with a rigid spacer between chromophores, so that a through-bond mechanism is presumed to remain important. A very gradual drop in TET rate constants as the connecting polymethylene chain becomes longer indicates that through-space interactions compete and apparently provide the only mechanism responsible for transfer when n ≥ 5. Rate constants in long molecules (n = 11-14) remain remarkably high (~108 s-1) - lower than in those with four-atom tethers by only 1 order of magnitude. This effect is explained on the basis of rapid conformational equilibria always keeping a sufficient fraction of the molecules coiled so that the two chromophores are close enough to interact within 10 ns, the time required for the competing γ-hydrogen abstraction used to monitor triplet lifetimes. Energy transfer accounts for 40-75% of triplet decay for the longer molecules. This high efficiency indicates that only a small fraction involves static quenching in ground-state conformers with the two ends within 4 A. The majority must represent a combination of rate-determining bond rotations to such geometries and equilibrated conformations with their ends farther apart but still able to undergo energy transfer within 10 ns. Thus, the measured rate constants are, in fact, a weighted average of three different conformational mechanisms. The decrease in rate constant with tether length is not monotonic: a relative increase in rate for medium-chain-length molecules is explained by a larger number of favorable conformers and further, in biphenyl derivatives, by a rotation along the terminal O-C bond between the tether and the aromatic ring. As was expected, replacement of the polymethylene tether with poly(ethylene oxide) promotes better flexibility and thus higher transfer rates. Rate constants were found to be lower by a factor of ~2 when biphenyl rather than naphthyl is the acceptor, in agreement with earlier bimolecular measurements. With the 4-methylbenzoyl group (π,π* lowest triplet) as donor instead of benzoyl (n,π* lowest triplet), a small (~1.5x) but consistent rate increase occurred for all tether lengths.
- Wagner, Peter J.,Klan, Petr
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p. 9626 - 9635
(2007/10/03)
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- Acetals as New 2′-O-Protecting Functions for the Synthesis of Oligoribonucleotides: Synthesis of Uridine Building Blocks and Evaluation of Their Relative Acid Stability
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A broad variety of new acyclic vinyl ethers (see 6-41) have been synthesized via the vinyl-interchange reaction of ethyl vinyl ether at room temperature using mercury(II) trifluoroacetate as a highly efficient catalyst. The appropriate vinyl ethers were r
- Matysiak, Stefan,Fitznar, Hans-Peter,Schnell, Ralf,Pfleiderer, Wolfgang
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p. 1545 - 1566
(2007/10/03)
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- Cobalt-mediated Radical Reactions in Organic Synthesis. Oxidative Cyclisations of Aryl and Alkyl Halides leading to Functionalised Reduced Heterocycles and Butyrolactones
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Reactions between the CoI species derived from cobalt(III) salen (11) or cobalt(II) salophen (12) and (O-allyl) or (O-but-3-enyl) iodophenols lead to isolatable cobalt complexes, viz. (16) and (27), which can be converted into substituted benzofurans, i.e. (17) and (23), and benzopyrans, i.e. (28) and (34); similarly, interaction between compound (36) and Co1 salen led in one step to 1,3-dimethylindole (37).Radical cyclisation of the acetal (38a) in the presence of Co1 cobaloxime leads to the cis-ring-fused alkyl cobalt complex (42), which can be converted in a preparative manner into lactone (44) following 1,2-elimination and hydrolysis/oxidation, and into lactone (53) following insertion of molecular oxygen , reduction and hydrolysis/oxidation.
- Bhandal, Harcharan,Patel, Vinod F.,Pattenden, Gerald,Russell, Jamie J.
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p. 2691 - 2701
(2007/10/02)
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- ARYLATION OF CYCLIC ETHERS BY GASEOUS PHENYLIUM IONS. FORMATION AND BEHAVIOR OF PHENOXENIUM IONS IN THE GAS PHASE
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Free, unsolvated phenylium ions formed by the spontaneous decay of 1,4-ditritiobenzene have been allowed to react with gaseous cyclic ethers (oxirane, propene oxide, and oxetane) and acetaldehyde in the pressure range 30-250 Torr and in the presence of a thermal radical scavenger (O2, 4 Torr).The effects of a gaseous base (NMe3, 20 Torr) and of an energy moderator (He, 630-720 Torr) were also investigated.Phenylium ion confirms its considerable site selectivity, demonstrated by the distinct preference for the n-type center of the substrate, although appreciable insertion into the carbocyclic structure of propene oxide and oxetane is observed as well.The stability features of the ionic intermediates from addition of phenylium ion to selected substrates have been evaluated as well as their fragmentation and isomerization mechanisms.The behavior of gaseous phenylium ion toward cyclic ethers, in particular its ability to formally abstract an oxygen atom from the ether to give the phenoxenium ion, a reaction first observed in the present study, is discussed and compared with previous mechanistic investigations carried out in the gas phase and in solution.
- Fornarini, Simonetta,Speranza, Maurizio
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p. 2506 - 2514
(2007/10/02)
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- CYCLIC ELIMINATION AND INTRAMOLECULAR INSERTION REACTIONS OF THERMALLY-GENERATED MONOMERIC METAPHOSPHORIC ESTERS (METAPHOSPHATES)
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2-Aryl-1,3,2-dioxaphospholanes (aryloxyphosphites) decompose thermally in the gas phase with loss of ethylene to generate aryl metaphosphates which cyclise by intramolecular insertion (phosphonylation) or abstract a β-hydrogen to form a terminal alkene by loss of HPO3.
- Cadogan, J.I.G.,Gosney, Ian,Wright, Peter M.
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p. 397 - 400
(2007/10/02)
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- Thermally Induced Gas Phase Phosphonylation of Arenes via Intramolecular Trapping of an Aryl Metaphosphate Moiety
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2-Aryloxy-1,3,2-dioxaphospholanes break down on pyrolysis in the gas phase by a mechanism best accounted for in terms of the formation of metaphosphate (ArOPO2) moieties, which rearrange to cyclic phosphonic monoesters via intramolecular insertion reactions, unless an abstractable β-hydrogen is present when a Chugaev-type reaction takes place to give a terminal alkene.
- Cadogan, J. I. G.,Cowley, Alan H.,Gosney, Ian,Pakulski, Marek,Wright, Peter M.,Yaslak, Salih
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p. 1685 - 1686
(2007/10/02)
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- Surface Photochemistry: Semiconductor Photoinduced Dimerization of Phenyl Vinyl Ether
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The dimerization of phenyl vinyl ether at an illuminated semiconductor surface has been demonstrated, and that reaction induced on ZnO was studied in detail.The involvement of surface-related processes has been shown to affect both the rate and stereochem
- Draper, Anthony M.,Ilyas, Mohammad,Mayo, Paul de,Ramamurthy, V.
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p. 6222 - 6230
(2007/10/02)
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- Photochemical Electron-Transfer Reactions: Effect of Ring Opening of the Cyclobutane Radical Cation on the Dimerization of Phenyl Vinyl Ether
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The photosensitized electron-transfer dimerization of olefins proceeds via several reversible steps.Limited kinetic data on some of these processes have been reported.We used the dependence of the product distribution in the electron-transfer-sensitized d
- Mattes, Susan L.,Luss, Henry R.,Farid, Samir
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p. 4779 - 4781
(2007/10/02)
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- Potassium Fluoride on Alumina. An Efficient Solid Base for Elimination, Addition, and Condensation
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Alumina coated with potassium fluoride proved to be a versatile solid base for olefin- and acetylene-forming elimination, the Michael addition, aldol condensation, and the Darzens condensation.
- Yamawaki, Junko,Kawate, Takehiko,Ando, Takashi,Hanafusa, Terukiyo
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p. 1885 - 1886
(2007/10/02)
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- Poly(ethylene glycols) Are Extraordinary Catalysts in Liquid-Liquid Two-Phase Dehydrohalogenation
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Poly(ethylene glycols) 3> are highly active and selective in catalyzing dehydrohalogenation in organic-aqueous hydroxide two-phase systems.
- Kimura, Yoshikazu,Regen, Steven L.
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p. 2493 - 2494
(2007/10/02)
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- Redox-photosensitised Reactions. Part 6. Stereospecific Ring Cleavage of 1-Phenoxy-1,2,2a,3,4,8b-hexahydrocyclobutanaphthalene-8b-carbonitrile and its 2-Methyl Derivatives by Redox-photosensitisation
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Ring cleavage of endo-1-phenoxy-1,2,2a,3,4,8b-hexahydrocyclobutanaphthalene-8b-carbonitrile (1a) occurs to give phenyl vinyl ether and 3,4-dihydronaphthalene-1-carbonitrile in a 1:1 ratio upon the selective photoexcitation of phenanthrene, naphthalene, or triphenylene at 313 nm in the presence of p-dicyanobenzene in acetonitrile.With the cis- and trans-2-methyl derivatives of (1a), the photosensitised ring cleavage is stereospecific.The key mechanistic pathway is suggested to be the formation of a ?-complex between the cyclobutanes and the cation radicals of the arenes, in which the phenoxy-group of the cyclobutanes plays important roles.It is speculated that the ring cleavage reaction proceeds by means of a concerted-like mechanism via the ?-complex without complete hole transfer.
- Majima, Tetsuro,Pac, Chyongjin,Sakurai, Hiroshi
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p. 2705 - 2708
(2007/10/02)
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- SYNTHESIS OF OLEFINS BY NICKEL-CATALYZED DECARBONYLATION OF S-(2-PYRIDYL) THIOATES
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S-(2-Pyridyl) thioates, especially derived from secondary and tertiary carboxylic acids, are decarbonylated by use of a catalytic amount of nickel chloride and zinc powder to give olefins in good yields.
- Goto, Toshio,Onaka, Makoto,Mukaiyama, Teruaki
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p. 709 - 712
(2007/10/02)
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