cas 2039-85-2, 3-Chlorostyrene | Articles data

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Photoredox Catalyzed Sulfonylation of Multisubstituted Allenes with Ru(bpy)3Cl2 or Rhodamine B
A highly regio- and stereoselective sulfonylation of allenes was developed that provided direct access to α, β-substituted unsaturated sulfone. By means of visible-light photoredox catalysis, the free radicals produced by p-toluenesulfonic acid reacted with multisubstituted allenes to obtain Markovnikov-type vinyl sulfones with Ru(bpy)3Cl2 or Rhodamine B as photocatalyst. The yield of this reaction could reach up to 91%. A series of unsaturated sulfones would be used for further transformation to some valuable compounds.
Chen, Jingyun,Chen, Shufang,Jiang, Jun,Lu, Qianqian,Shi, Liyang,Xu, Zekun,Yimei, Zhao
supporting information

(2021/11/09)

Switchable Chemoselectivity of Reactive Intermediates Formation and Their Direct Use in A Flow Microreactor
A chemoselectivity switchable microflow reaction was developed to generate reactive and unstable intermediates. The switchable chemoselectivity of this reaction enables a selection for one of two different intermediates, an aryllithium or a benzyl lithium, at will from the same starting material. Starting from bromo-substituted styrenes, the aryllithium intermediates were converted to the substituted styrenes, whereas the benzyl lithium intermediates were engaged in an anionic polymerization. These chemoselectivity-switchable reactions can be integrated to produce polymers that cannot be formed during typical polymerization reactions.
Ashikari, Yosuke,Tamaki, Takashi,Kawaguchi, Tomoko,Furusawa, Mai,Yonekura, Yuya,Ishikawa, Susumu,Takahashi, Yusuke,Aizawa, Yoko,Nagaki, Aiichiro
supporting information
p. 16107 - 16111
(2021/10/12)

Controlling the Lewis Acidity and Polymerizing Effectively Prevent Frustrated Lewis Pairs from Deactivation in the Hydrogenation of Terminal Alkynes
Two strategies were reported to prevent the deactivation of Frustrated Lewis pairs (FLPs) in the hydrogenation of terminal alkynes: reducing the Lewis acidity and polymerizing the Lewis acid. A polymeric Lewis acid (P-BPh3) with high stability was designed and synthesized. Excellent conversion (up to 99%) and selectivity can be achieved in the hydrogenation of terminal alkynes catalyzed by P-BPh3. This catalytic system works quite well for different substrates. In addition, the P-BPh3 can be easily recycled.
Geng, Jiao,Hu, Xingbang,Liu, Qiang,Wu, Youting,Yang, Liu,Yao, Chenfei
p. 3685 - 3690
(2021/05/31)

Copper-Catalyzed Sulfonylation of Cyclobutanone Oxime Esters with Sulfonyl Hydrazides
A copper-catalyzed radical cross-coupling of cyclobutanone oxime esters with sulfonyl hydrazides has been developed. The copper-based catalytic system proved crucial for cleavage of the C-C bond of cyclobutanone oximes and for selective C-S bond-formation involving persistent sulfonyl-metal radical intermediates. This protocol is distinguished by the low-cost catalytic system, which does not require ligand, base, or toxic cyanide salt, and by the use of readily accessible starting materials, as well as broad substrate scope, providing an efficient approach to various diversely substituted cyano-containing sulfones.
Dong, Bingbing,Lu, Jiansha,Bao, Honghao,Zhang, Yuanyuan,Liu, Yingguo,Leng, Yuting
supporting information
p. 3769 - 3776
(2021/07/14)

Electrochemistry enabled selective vicinal fluorosulfenylation and fluorosulfoxidation of alkenes
Both sulfur and fluorine play important roles in organic synthesis, the life science, and materials science. The direct incorporation of these elements into organic scaffolds with precise control of the oxidation states of sulfur moieties is of great significance. Herein, we report the highly selective electrochemical vicinal fluorosulfenylation and fluorosulfoxidation reactions of alkenes, which were enabled by the unique ability of electrochemistry to dial in the potentials on demand. Preliminary mechanistic investigations revealed that the fluorosulfenylation reaction proceeded through a radical-polar crossover mechanism involving a key episulfonium ion intermediate. Subsequent electrochemical oxidation of fluorosulfides to fluorosulfoxides were readily achieved under a higher applied potential with the adventitious H2O in the reaction mixture.
Jiang, Yimin,Shi, Zhaojiang,Wu, Jinnan,Wu, Shaofen,Ye, Keyin,Yu, Yi,Yuan, Yaofeng
supporting information

(2021/11/17)

Iron-Catalyzed Direct Julia-Type Olefination of Alcohols
Herein, we report an iron-catalyzed, convenient, and expedient strategy for the synthesis of styrene and naphthalene derivatives with the liberation of dihydrogen. The use of a catalyst derived from an earth-abundant metal provides a sustainable strategy to olefins. This method exhibits wide substrate scope (primary and secondary alcohols) functional group tolerance (amino, nitro, halo, alkoxy, thiomethoxy, and S- A nd N-heterocyclic compounds) that can be scaled up. The unprecedented synthesis of 1-methyl naphthalenes proceeds via tandem methenylation/double dehydrogenation. Mechanistic study shows that the cleavage of the C-H bond of alcohol is the rate-determining step.
Landge, Vinod G.,Babu, Reshma,Yadav, Vinita,Subaramanian, Murugan,Gupta, Virendrakumar,Balaraman, Ekambaram
p. 9876 - 9886
(2020/09/03)

Palladium-catalyzed proaromatic C(Alkenyl)-H olefination: Synthesis of densely functionalized 1,3-dienes
An example of proaromatic C(alkenyl)-H olefination is reported. This protocol utilized a free carboxylic acid as a directing group for C(alkenyl)-H activation of 1,4-cyclohexadiene and coupled with various alkenes. Direct and sequential bisolefinations of proaromatic acids were achieved. The synthetic applicability has been exhibited by [4 + 2] cycloaddition and decarboxylative aromatization of the resulting proaromatic 1,3-dienes. Additionally, several kinetic studies also have been carried out to elucidate the reaction mechanism.
Wang, Yu-Chun,Huang, Yen-Hsiang,Tsai, Hung-Chang,Sidick Basha,Chou, Chih-Ming
supporting information
p. 6765 - 6770
(2020/09/15)

Metal-free and base-free decarboxylation of substituted cinnamic acids in a deep eutectic solvent
A metal-free and base-free strategy was developed in DES to synthesize styrenes for the first time by decarboxylation of cinnamic acid derivatives, which provided a renewable and cost efficiently protocol to access various styrenes including those with functional groups such as 4-vinylphenol and 1-chloro-4-vinylbenzene.
Chen, Chen,Jian, Yuqing,Lei, Yuxin,Li, Bin,Peng, Caiyun,Sheng, Wen-Bing,Sumera, Yasmin,Wang, Wei,Zhang, Ming
p. 558 - 563
(2020/01/24)

Design, synthesis of novel 4,5-dihydroisoxazole-containing benzamide derivatives as highly potent FtsZ inhibitors capable of killing a variety of MDR Staphylococcus aureus
Antibiotic resistance among clinically significant bacterial pathogens, such as methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant S. aureus (VRSA) is becoming a prevalent threat to public health, and new antibacterial agents with novel mechanisms of action hence are in an urgent need. As a part of continuing effort to develop antibacterial agents, we rationally designed and synthesized two series of 4,5-dihydroisoxazol-5-yl and 4,5-dihydroisoxazol-3-yl-containing benzamide derivatives that targeted the bacterial cell division protein FtsZ. Evaluation of their activity against a panel of Gram-positive and -negative pathogens revealed that compound A16 possessing the 4,5-dihydroisoxazol-5-yl group showed outstanding antibacterial activity (MIC, ≤0.125–0.5 μg/mL) against various testing strains, including methicillin-resistant, penicillin-resistant and clinical isolated S. aureus strains. Besides, further mouse infection model revealed that A16 could be effective in vivo and non-toxic to Hela cells. Finally, a detailed discussion of structure-activity relationships was conducted, referring to the docking results. It is worth noting that substituting a 4,5-dihydroisoxazole ring for the isoxazole ring not only broadened the antibacterial spectrum but also resulted in a significant increase in antibacterial activity against S. aureus strains. Taken together, these results suggest a promising chemotype for the development of new FtsZ-targeting bactericidal agents.
Song, Di,Bi, Fangchao,Zhang, Nan,Qin, Yinhui,Liu, Xingbang,Teng, Yuetai,Ma, Shutao
supporting information

(2020/09/11)

Nitrogen-fixing of ultrasmall Pd-based bimetallic nanoclusters on carbon supports
Synthesis of supported Pd-based bimetallic catalysts is of great importance in the heterogeneous catalysis field owing to their optimal geometric and electronic effects. Downsizing active metals to ultrasmall nanocluster (2-reduction at 400–500 °C. Through the nitrogen-fixing strategy, we prepare 9 sub-2 nm Pd-based bimetallic nanocluster catalysts by conventional impregnation process. The prepared supported bimetallic Pd-Pb nanocluster catalyst exhibit a high turnover frequency of 1092 h?1 for the semihydrogenation of phenylacetylene under a mild condition (30 °C, 5 bar H2), along with a high selectivity of >93% to styrene, demonstrating the alloying and small-size effects in the bimetallic nanocluster catalysts.
Chen, Ping,Liang, Hai-Wei,Shen, Shan-Cheng,Wang, Lei,Xu, Shi-Long,Yin, Peng,Zhang, Le-Le
p. 297 - 304
(2020/07/03)

Nickel(ii)-catalyzed direct olefination of benzyl alcohols with sulfones with the liberation of H2
A nickel(ii)-catalyzed direct olefination of benzyl alcohols with sulfones to access various terminal and internal olefins with the liberation of hydrogen gas is reported.
Landge, Vinod G.,Yadav, Vinita,Subaramanian, Murugan,Dangarh, Pragya,Balaraman, Ekambaram
supporting information
p. 6130 - 6133
(2019/06/03)

Selective Semi-Hydrogenation of Terminal Alkynes Promoted by Bimetallic Cu-Pd Nanoparticles
The selective semi-hydrogenation of terminal alkynes was efficiently performed, under mild reaction conditions (H 2 balloon, 110 °C), promoted by a bimetallic nanocatalyst composed of copper and palladium nanoparticles (5:1 weight ratio) supported on mesostructured silica (MCM-48). The Cu-PdNPS@MCM-48 catalyst, which demonstrated to be highly chemoselective towards the alkyne functionality, is readily prepared from commercial materials and can be recovered and reused after thermal treatment followed by reduction under H 2 atmosphere.
Buxaderas, Eduardo,Volpe, María Alicia,Radivoy, Gabriel
p. 1466 - 1472
(2019/03/07)

Copper-Catalyzed Oxidative Difunctionalization of Terminal Unactivated Alkenes
The copper(II)-promoted free-radical oxidative difunctionalization of terminal alkenes to access ketoazides by utilizing molecular oxygen has been reported. A series of styrene derivatives have been evaluated and were found to be compatible to give the desired difunctionalized products in moderate to good yields. The role of molecular oxygen both as an oxidant and oxygen atom source in this catalytic transformation has been unquestionably demonstrated by 18O-labeling studies and a radical mechanistic pathway involving the oxidative formation of azidyl radicals is also designed. This environment-friendly catalytic oxidative protocol can transform aldehyde to nitrile.
Hussain, Muhammad Ijaz,Feng, Yangyang,Hu, Liangzhen,Deng, Qingfu,Zhang, Xiaohui,Xiong, Yan
p. 7852 - 7859
(2018/05/30)

Chlorination of phenylallene derivatives with 1-chloro-1,2-benziodoxol-3-one: Synthesis of vicinal-dichlorides and chlorodienes
Allyl and vinyl chlorides represent important structural motifs in organic chemistry. Herein is described the chemoselective and regioselective reaction of aryl- and α-substituted phenylallenes with the hypervalent iodine (HVI) reagent 1-chloro-1,2-benz-iodoxol-3-one. The reaction typically results in vicinal dichlorides, except with proton-containing α-alkyl substituents, which instead give chlorinated dienes as the major product. Experimental evidence suggests that a radical mechanism is involved.
Zhao, Zhensheng,Murphy, Graham K.
supporting information
p. 796 - 802
(2018/04/16)

Catalytic Asymmetric Dearomatization by Visible-Light-Activated [2+2] Photocycloaddition
A novel method for the catalytic asymmetric dearomatization by visible-light-activated [2+2] photocycloaddition with benzofurans and one example of a benzothiophene is reported, thereby providing chiral tricyclic structures with up to four stereocenters including quaternary stereocenters. The benzofurans and the benzothiophene are functionalized at the 2-position with a chelating N-acylpyrazole moiety which permits the coordination of a visible-light-activatable chiral-at-rhodium Lewis acid catalyst. Computational molecular modeling revealed the origin of the unusual regioselectivity and identified the heteroatom in the heterocycle to be key for the regiocontrol.
Hu, Naifu,Jung, Hoimin,Zheng, Yu,Lee, Juhyeong,Zhang, Lilu,Ullah, Zakir,Xie, Xiulan,Harms, Klaus,Baik, Mu-Hyun,Meggers, Eric
supporting information
p. 6242 - 6246
(2018/05/03)

Phosphine-free cobalt pincer complex catalyzed: Z -selective semi-hydrogenation of unbiased alkynes
Herein, we report a novel, molecularly defined NNN-type cobalt pincer complex catalyzed transfer semi-hydrogenation of unbiased alkynes to Z-selective alkenes. This unified process is highly stereo- and chemo-selective and exhibits a broad scope as well as wide functional group tolerance. Ammonia-borane (AB), a bench-stable substrate with high gravimetric hydrogen capacity, was used as a safe and practical transfer hydrogenating source.
Landge, Vinod G.,Pitchaimani, Jayaraman,Midya, Siba P.,Subaramanian, Murugan,Madhu, Vedichi,Balaraman, Ekambaram
p. 428 - 433
(2018/02/07)

Fluorinative Rearrangements of Substituted Phenylallenes Mediated by (Difluoroiodo)toluene: Synthesis of α-(Difluoromethyl)styrenes
Phenylallenes undergo fluorinative rearrangement upon the action of (difluoroiodo)toluene in the presence of 20 mol % BF3?OEt2 to yield α-difluoromethyl styrenes. This unprecedented reaction was entirely chemoselective for the internal allene π bond, and showed remarkable regioselectivity during the fluorination event. Substituted phenylallenes, phenylallenes possessing both phenyl- and α-allenyl substituents, and diphenylallenes were investigated, and good functional-group compatibility was observed throughout. The ease with which allenes can be prepared on a large scale, and the operational simplicity of this reaction allowed us to rapidly access fluorine-containing building blocks that have not been accessed by conventional deoxyfluorination strategies.
Zhao, Zhensheng,Racicot, Léanne,Murphy, Graham K.
supporting information
p. 11620 - 11623
(2017/09/11)

Visible light-promoted dihydroxylation of styrenes with water and dioxygen
An efficient visible light promoted metal-free dihydroxylation of styrenes with water and dioxygen has been developed for the construction of vicinal alcohols. The protocol was operationally simple with a broad substrate scope. The mechanistic studies demonstrated that one of the hydroxyl groups came from water and the other one came from molecular oxygen. Additionally, the β-alkyoxy alcohols could also be obtained using a similar strategy.
Yang, Bo,Lu, Zhan
supporting information
p. 12634 - 12637
(2017/12/02)

Selective Semihydrogenation of Alkynes with N-Graphitic-Modified Cobalt Nanoparticles Supported on Silica
For the first time N-graphitic-modified cobalt nanoparticles (Co/phen@SiO2-800) are shown to be active in the semihydrogenation of alkynes to alkenes. Key to success for efficient catalysis is both the modification of the metal nanoparticles by nitrogen-doped graphitic layers and the use of silica as support. Several internal alkynes are converted to the Z isomer in high yields with up to 93% selectivity. In addition, a variety of terminal alkynes, including sensitive functionalized compounds, are readily converted into terminal alkenes. Notably, this non-noble-metal catalyst allows for the purification of alkenes by selective hydrogenation of the corresponding alkyne in the presence of an excess of olefin.
Chen, Feng,Kreyenschulte, Carsten,Radnik, J?rg,Lund, Henrik,Surkus, Annette-Enrica,Junge, Kathrin,Beller, Matthias
p. 1526 - 1532
(2017/08/15)

Benzocarbazoles dioxane derivatives, its preparation process and its use in medicine
The invention relates to a benzodioxane derivative, a preparation method thereof and application of the derivative in medicines. Specifically, the invention relates to a novel benzodioxane derivative shown as a formula (I), medial salt thereof or a medicine composition containing the derivative, and a preparation method of the derivative. The invention further relates to a use of the benzodioxane derivative and the medial salt thereof or the medicine composition containing the derivative in preparing therapeutic agent, especially GPR 40 agonist, and a drug for treating the diseases such as diabetes, metabolic disorders and the like, wherein each substituent group in the formula (I) is as defined in the description.
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Paragraph 0832; 0834-0837

(2016/10/10)

Heterogeneous Gold-Catalyzed Selective Semireduction of Alkynes using Formic Acid as Hydrogen Source
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
supporting information
p. 1410 - 1416
(2016/05/19)

Noble-metal-free deoxygenation of epoxides: Titanium dioxide as a photocatalytically regenerable electron-transfer catalyst
Catalytic deoxygenation of epoxides into the corresponding alkenes is a very important reaction in organic synthesis. Early reported systems, however, require noble metals, high reaction temperatures (>373 K), or toxic reducing agents. Here, we report a noble-metal-free heterogeneous catalytic system driven with alcohol as a reducing agent at room temperature. Photoirradiation (λ 2) with alcohol promotes efficient and selective deoxygenation of epoxides into alkenes. This noble-metal-free catalytic deoxygenation is facilitated by the combination of electron transfer from surface Ti3+ atoms on TiO2 to epoxides, which promotes deoxygenation of epoxides, and photocatalytic action of TiO2, which regenerates oxidized surface Ti atoms with alcohol as a reducing agent.
Shiraishi, Yasuhiro,Hirakawa, Hiroaki,Togawa, Yoshiki,Hirai, Takayuki
p. 1642 - 1649
(2014/06/24)

Efficient and exceptionally selective semireduction of alkynes using a supported gold catalyst under a CO atmosphere
A new efficient method for chemo- and regio-selective semireduction of alkynes using CO/H2O as the hydrogen source catalyzed by gold supported on high surface area TiO2 was developed. A facile and practical synthesis of 1,2-dideuterioalkenes was also realized by using CO/D2O as the reducing agent. the Partner Organisations 2014.
Li, Shu-Shuang,Liu, Xiang,Liu, Yong-Mei,He, He-Yong,Fan, Kang-Nian,Cao, Yong
supporting information
p. 5626 - 5628
(2014/05/20)

Flow Chemistry Syntheses of Styrenes, Unsymmetrical Stilbenes and Branched Aldehydes
Two tandem flow chemistry processes have been developed. A single palladium-catalysed Heck reaction with ethylene gas provides an efficient synthesis for functionalised styrenes. Through further elaboration the catalyst becomes multi-functional and performs a second Heck reaction providing a single continuous process for the synthesis of unsymmetrical stilbenes. In addition, the continuous, rhodium-catalysed, hydroformylation of styrene derivatives with syngas affords branched aldehydes with good selectivity. Incorporation of an in-line aqueous wash and liquid-liquid separation allowed for the ethylene Heck reaction to be telescoped into the hydroformylation step such that a single flow synthesis of branched aldehydes directly from aryl iodides was achieved. The tube-in-tube semi-permeable membrane-based gas reactor and liquid-liquid separator both play an essential role in enabling these telescoped flow processes.
Bourne, Samuel L.,O'Brien, Matthew,Kasinathan, Sivarajan,Koos, Peter,Tolstoy, Paeivi,Hu, Dennis X.,Bates, Roderick W.,Martin, Benjamin,Schenkel, Berthold,Ley, Steven V.
p. 159 - 172
(2013/03/13)

Selective iron-catalyzed transfer hydrogenation of terminal alkynes
A novel iron-catalyzed transfer hydrogenation of alkynes to the corresponding alkenes applying formic acid as a hydrogen donor is reported. An in situ combination of Fe(BF4)2·6H2O and tetraphos allows for highly selective hydrogenation of a broad range of aromatic and aliphatic alkynes tolerating different functional groups.
Wienhoefer, Gerrit,Westerhaus, Felix A.,Jagadeesh, Rajenahally V.,Junge, Kathrin,Junge, Henrik,Beller, Matthias
supporting information; experimental part
p. 4827 - 4829
(2012/06/04)

NOVEL INHIBITORS
The invention relates to novel pyrrolidine derivatives of formula (I): wherein R1, R2 and R3 are as defined herein, as inhibitors of glutaminyl cyclase (QC, EC 2.3.2.5). QC catalyzes the intramolecular cyclization of N-terminal glutamine residues into pyroglutamic acid (5-oxo-prolyl, pGlu*) under liberation of ammonia and the intramolecular cyclization of N-terminal glutamate residues into pyroglutamic acid under liberation of water.
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Page/Page column 116

(2011/05/03)

One-pot Suzuki/Heck sequence for the synthesis of (E)-stilbenes featuring a recyclable silica-supported palladium catalyst via a multi-component reaction in 1,3-propanediol
The synthesis of (E)-stilbenes was performed following a one-pot Suzuki/Heck sequence through the use of potassium vinyltrifluoroborate. The combination of heterogeneous palladium/silica (Pd/SiO2) catalyst with potassium phosphate monohydrate (K3PO4?H 2O) as base resulted in useful to good isolated yields regardless of the ortho-, meta- or para-substitution of the aryl halides employed. In a sustainable approach, we found that bio-sourced 1,3- propanediol could advantageously replace N-methylpyrrolidone (NMP) as similar yields were obtained. Moreover, the reactivity gap between aryl iodides and bromides resulting from the use of 1,3-propanediol allowed an efficient multi-component approach toward the synthesis of (E)-stilbenes. Furthermore, this heterogeneous catalyst was found to be extremely robust despite the use of aerobic conditions and was successfully re-used over several cycles.
Joucla, Lionel,Cusati, Giuseppe,Pinel, Catherine,Djakovitch, Laurent
scheme or table
p. 1993 - 2001
(2010/10/20)

Ruthenium-catalyzed synthesis of β-oxo esters in aqueous medium: Scope and limitations
The ability of the hydrosoluble ruthenium(ii) complexes [RuCl 2(η6-arene)(PTA)] 3a-d, [RuCl2(η 6-arene)(PTA-Bn)] 4a-d, [RuCl2(η6-arene) (DAPTA)] 5a-d, [RuCl2(η6-arene)(TPPMS)] 6a-d (arene = C6H6, p-cymene, 1,3,5-C6H3Me 3, C6Me6) to promote the atom-economic formation of β-oxo esters, by addition of carboxylic acids to terminal propargylic alcohols in water has been explored. Scope, limitations and catalyst recycling have been evaluated using the most active catalyst [RuCl 2(η6-C6H6)(TPPMS)], 6a.
Cadierno, Victorio,Francos, Javier,Gimeno, Jose
experimental part
p. 135 - 143
(2010/05/18)

Low pressure vinylation of aryl and vinyl halides via Heck-Mizoroki reactions using ethylene
Aryl bromides and iodides in the presence of catalytic amounts of a palladacycle derived from acetophenone oxime and 2 equiv of potassium acetate react with ethylene under ambient pressure (15-30 psi) to give the corresponding vinylarenes. The reactions work with both electron-deficient and electron-rich aryl compounds and tolerate wide variety of common functional groups. Vinyl bromides lead to 1,3-dienes in moderate yields.
Smith, Craig R.,RajanBabu
supporting information; experimental part
p. 1102 - 1110
(2010/03/25)

Enantioconvergent hydrolysis of styrene epoxides by newly discovered epoxide hydrolases in mung bean
Two novel epoxide hydrolases were discovered in mung bean (Phaseolus radiatus L.) for the first time, either of which can catalyze enantioconvergent hydrolysis of styrene epoxides. Their regioselectivity coefficients are more than 90% for the p-nitrostyrene oxide. Furthermore, the crude mung bean powder was also shown to be a cheap and practical biocatalyst, allowing a one-step asymmetric synthesis of chiral (R)-diols from racemic epoxides, in up to >99% ee and 68.7% overall yield (after recrystallization).
Xu, Wei,Xu, Jian-He,Pan, Jiang,Gu, Qing,Wu, Xin-Yan
p. 1737 - 1740
(2007/10/03)

Bacterial monooxygenase mediated preparation of nonracemic chiral oxiranes: Study of the effects of substituent nature and position
Monooxygenation of styrene derivatives using recombinant E. coli biocatalyst is an efficient way to prepare the corresponding oxiranes. The electronic and geometric effects of the ring substituents are described and show the relaxed specificity of the enzyme and its high stereoselectivity.
Bernasconi, Silvana,Orsini, Fulvia,Sello, Guido,Di Gennaro, Patrizia
p. 1603 - 1606
(2007/10/03)

Unexpected chemoselective debromination and reduction of 1,1-dibromo-1-alkenes mediated by samarium metal in methanol
An unexpected samarium metal mediated chemoselective debromination and reduction of 1,1-dibromo-1-alkenes in methanol has been developed, which generates vinyl monobromides, alkenes, and alkanes respectively with appropriate molar ratio of samarium to 1,1-dibromo-1-alkene.
Wang, Lei,Li, Pinhua,Xie, Yuanyuan,Ding, Yanbin
p. 1137 - 1140
(2007/10/03)

Formation and decomposition of chloroaromatic compounds in chlorine-containing benzene/oxygen flames
Premixed chlorine-containing, fuel-rich, low-pressure benzene/oxygen flames were analysed for the formation of (oxygenated) chloroaromatic compounds and their radicals by means of the condensation/radical-scavenging method (Hausmann, M., Homann, K.-H., 1995. Ber. Busenges. Phys. Chem. 99, 853-862). Several chlorinated organic compounds (methyl chloride, t-butyl chloride, chlorobenzene, chloroform) were used as additives within a maximum concentration of 10% of total fuel. Product identification and quantification were performed by GC/MS. The extent of formation of chloroaromatic compounds in these flames was largest in the cases of chlorobenzene and chloroform as additives. For chlorobenzene, 12 different chloroaromatics could be analysed in between C7H7Cl and C12H9Cl. Their formation is mainly due to conversion of initial chlorobenzene into substituted or oxidised derivatives, or growth products. Additional chlorination of aromatics is shown to be of minor importance in chlorobenzene-containing flames. Three isomeric (o/m/p) scavenging products could be identified for the chlorophenyl radical. In the chloroform case, 15 chloroaromatics could be analysed in between C6H5Cl and C14H9Cl. The weak C-Cl bond in chloroform is responsible for the high extent of chloroaromatics formation, either by Cl abstraction from the additive or by chlorination reactions via Cl radicals. Additionally, specific pathways to (di)chloroaromatics and chlorinated fulvene-type structures are outlined via CHCl2 and CCl2 radicals.
Burfeindt,Homann
p. 439 - 447
(2007/10/03)

A practical synthesis of (R)-3-chlorostyrene oxide starting from 3- chloroethylbenzene
A novel and practical synthesis of (R)-3-chlorostyrene oxide (-)-1 was achieved starting from commercially available 3-chloroethylbenzene 3. Enantiopure (-)-3-chlorostyrene bromohydrin (-)-5 was obtained by the treatment of racemic (±)-5 with lipase QL in the presence of acylating reagents. 3-Chloro-α,β-dibromoethylbenzene 4, a precursor of (±)-5, was synthesized via the expeditious bromination of 3 which was developed by these authors.
Tanaka, Ken,Yasuda, Mari
p. 3275 - 3282
(2007/10/03)

Oxidative addition of dimethyl malonate to styrenes mediated by cerium(IV) ammonium nitrate: Some novel observations
The oxidative addition of dimethyl malonate to ring substituted styrenes leads to the formation of substituted dimethyl (2-oxo-2-phenylethyl) malonate and methyl 2-oxo-5-phenyltetrahydrofuran-3-carboxylate along with small amounts of substituted dimethyl [2-(nitrooxy)-2-phenylethyl] malonate and dimethyl 2-methoxy-2-phenylethyl) malonate. A tentative mechanism which supports the formation of these products is also presented.
Nair, Vijay,Mathew, Jessy,Nair, Latha G.
p. 3053 - 3064
(2007/10/03)

Use of kinetic isotope effects in mechanism studies. Isotope effects and element effects associated with Hydron-Transfer steps during alkoxide-promoted dehydrohalogenations
The Arrhenius behavior of the primary kinetic isotope effect, (k(H)/k(D))(Obs) and (k(H)/k(T))(Obs), associated with the methanolic sodium methoxide-promoted dehydrohalogenations of m-ClC6H4C(i)HClCH2Cl (I), m-CF3C6H4C(i)-HClCH2Cl (II) and p-CF3C6H4C(i)HClCH2F (III) has been used to calculate the internal-return parameters, a = k(-1)/K(Elim)(X), in a two-step mechanism featuring a hydrogen-bonded carbanion. This carbanion partitions between returning the hydron to carbon, k(-1), and the loss of halide, K(Elm)(X). Isotope effects at 25°C for I, (k(H)/k(D))(Obs) = 3.40 and (k(H)/ k(T))(Obs) = 6.20, and II, (k(H)/k(D))(Obs) = 3.49 and (k(H)/k(T))(Obs) = 6.55, result in similar values for a: a(H) = 0.59, a(D) = 0.13-0.14 and a(T) = 0.07. Smaller values of (k(H)/k(D))(Obs) = 2.19 and (k(H)/k(T))(Obs) = 3.56 for III are due to more internal return [a(H) = 1.9, a(D) = 0.50, and a(T) = 0.28] associated with the dehydrofluorination reaction. Calculation of k1 ( k(Obs) [a + 1]) results in similar isotope effects for hydron transfer in these reactions: k1(H)/k1(D) = 4.74 and k1(H)/K1(T) = 9.20; II, k1(H)/k1(D) = 4.91 and k1(H)/k1(T) = 9.75; III, k1(H)/k1(D) = 4.75 and k1(H)/k1(T) = 9.17. Reactions of m-ClC6H4C(i)HBrCH2Br and m-ClC6H4C(i)HClCH2Br have very small amounts of internal return, a(H) = 0.05 and a(D) = 0.01, and (k(H)/k(D))(Obs) = 4.95 results in k1(H)/k1(D) = 5.11 The measured isotope effects are therefore due to differences in the amount of internal return and not in the symmetry of transition state structures for the hydron transfer, and the element effect, (k(HBr)/ k(HCl)) = 29, for m-ClC6H4CHClCH2X is mainly due to the hydron-transfer step, k1(HBr)/k1(HCl) = 19, and not the breaking of the C-X bend. The kinetic solvent isotope effects, k(MeOD)/k(MeOH) ~ 2.5, are consistent with three methanols of solvation lost prior to the hydron-transfer step. The energetics associated with desolvation of methoxide ion are part of the measured reaction energetics of these systems.
Koch, Heinz F.,Lodder, Gerrit,Koch, Judith G.,Bogdan, David J.,Brown, Geoffrey H.,Carlson, Carrie A.,Dean, Amy B.,Hage, Ronald,Han, Patrick,Hopman, Johan C. P.,James, Lisa A.,Knape, Petra M.,Roos, Eric C.,Sardina, Melissa L.,Sawyer, Rachael A.,Scott, Barbara O.,Testa III, Charles A.,Wickham, Steven D.
p. 9965 - 9974
(2007/10/03)

Pyrolysis of (2-Phenylethyl)phenylsulfonium Ylides
In order to obtain information concerning the reaction mechanism of the pyrolysis of sulfonium ylides bearing a substituted phenyl group on the 2-position in the S-ethyl group of ethylphenylsulfonium ylide, (2-phenylethyl)phenylsulfonium bis(methoxycarbonyl)methylide (1) and dicyanomethylide(2) were subjected to pyrolysis in benzene.The reaction rates of 1 and 2 at 140 deg C were 6.0- and 3.2-times faster than those of ethylphenylsulfonium bis(methoxycarbonyl)methylide and dicyanomethylide, respectively.The activation parameters for 1 were ΔH++=125 kJ mol-1 and ΔS++=-3.8 JK-18mol-1, while those for 2 were ΔH++=124 kJ mol-1 and ΔS++=-2.5 JK-1 mol-1.Substituent efects on the β-phenyl groups in 1 and 2 afforded positive Hammett ρ-values: ρ = 0.49 (γ = 0.997) and ρ = 0.26 (γ = 0.993), respectively.From the obtained results, it was suggested that the pyrolysis proceeds through essentially a concerted intramolecular cis-elimination inclined toward a slightly carbanion-like type from an E1-like type by introducing a phenyl substituent at the 2-position of the ethyl group in the ethylphenylsulfonium ylide.
Yoshimura, Toshiaki,Motoyama, Atsushi,Morishige, Akiko,Tsukurimichi, Eiichi,Shimasaki, Choichiro,Hasegawa, Kiyoshi
p. 174 - 180
(2007/10/02)

REACTIONS OF DIHALOCARBENES WITH SUBSTITUTED SPIROHEPTA-4,6-DIENES
Reactions of dihalocarbenes with spirohepta-4,6-diene lead to the formation of 1-halo-3-(2-haloethyl)benzenes, which readily undergo dehydrohalogenation to 3-halostyrenes.From 1-arylspirohepta-4,6-dienes and dihalocarbenes 3-halostilbenes are obtained.
Molchanov, A. P.,Kostikov, R. R.
p. 935 - 937
(2007/10/02)

Silicon Effects. II. Structure and Stability of 1-Phenyl-2-(trimethylsilyl)ethyl Cation in Solution
Solvolysis rates have been measured in various solvents at 25 deg C for 1-(substituted phenyl)-2-(trimethylsilyl)ethyl trifluoroacetates (1a - 1g; R=H, 4-Me, 4-Cl, 4-Br, 3-Cl, 3,4-Cl2, and 3,5-Cl2, respectively) and structurally related compounds, 1-phenylethyl-, 3,3-dimethyl-1-phenylbutyl-, and 1-(4-methylphenyl)ethyl trifluoroacetates (3a, 4, and 5).In dioxane/water mixtures 1g solvolyzes with the same sensitivity to the change in solvent ionizing power as that for a kc substrate 5.The solvolyses of 1e and 5 exhibit almost identical α-deuterium kinetic isotope effects (kH/KD) of 1.18 - 1.19 in aq dioxane.Substituent effect on the solvolysis of 1 in 90 percent aq dioxane is expressed by an LArSR equation: log kX/kH = -3.05 (?0 + 1.05 Δ?(mean)+R) (R = 0.9997).These findings are consistent with kc mechanism for the solvolysis of 1.Relative rates for the solvolysis of 1a, 3a, and 4 in 30 percent aq dioxane are 2.99x105:2.84:1.0 indicating solvolytic generation of α-(trimethylsilylmethyl)benzyl cation to be about 7 kcal mol-1 energetically more favorable than that of the corresponding α-alkylbenzyl cations.
Shimizu, Nobujiro,Watanabe, Shin-ichiro,Tsuno, Yuho
p. 2249 - 2254
(2007/10/02)

Mechanism of Thermal Eliminations. Part 30. Pyrolysis of 2-Trimethylsilylethanol and 1-Aryl Derivatives
The Arrhenius parameters (Eact = 45.57 kcal mol-1, log A/s-1 = 12.865) and rate coefficient at 600 K (1.84 * 10-4 s-1) for the cis β-thermal elimination of trimethylsilanol from 2-trimethylsilylethanol are identical (within experimental error) with those reported in the literature for elimination of methyl trimethylsilyl ether from 1-methoxy-2-(trimethylsilyl)ethane.This indicates that the driving force for the reaction, formation of the Si-O bond, is such that alteration of the nucleophilicity of oxygen has little effect on the reaction rate.A series of 1-aryl-2-trimethylsilylethanols have been prepared and their rates of elimination determined.The activating effect of the 1-aryl substituent (5.2-fold) is much less than the corresponding effect in the pyrolysis of ethyl acetates (63-fold) and 2-trimethylsilylethyl acetates (87-fold).Breaking of the α-C-O bond is thus kinetically less important than in the other reactions, and this conclusion is confirmed by a correlation of the rate data with the Yukawa-Tsuno equation which gives ρ = -0.4, r = 0.3.Si-O bond formation in the reaction is thereby shown to be of over-riding kinetic importance.For the 4-methylphenyl- and 4-methoxyphenyl compounds a minor competing reaction was the elimination of water to give the corresponding 1-aryl-2-trimethylsilylethene, and this has a higher activation energy than for the elimination of trimethylsilanol.NMR spectra for the 1-aryl-2-trimethylsilylethanols show that interaction between the OH and SiMe3 groups inhibits free rotation about the C(1)-C(2) bond.Preparation of 1-aryl-2-trimethylsilylethanols gave 1,3-diaryl-4-trimethylsilylbutyl trimethylsilyl ethers as byproducts arising from elimination of water from two molecules of the alcohols in a process believed to be two-step.
Taylor, Roger
p. 1703 - 1706
(2007/10/02)

Flash vacuum pyrolysis of dialkyl diazobenzylphosphonates forming styrenes via a Wittig type intermediate
Phenylphosphonylcarbene generated in gas phase at high temperature produced 1,2-oxaphosphetane 1-oxides as a result of intramolecular C-H insertion into ester alkyl group, which underwent fragmentation leading to styrene derivatives and metaphosphate at higher temperature.
Tomioka,Watanabe,Kobayashi,Hirai
p. 5061 - 5064
(2007/10/02)

REACTION OF DICHLOROCARBENE WITH SPIROHEPTA-4,6-DIENE
Dichlorocarbene adds to spirohept-4,6-diene with the formation of 6,6-dichlorospiro(bicyclohex-2-ene-4,1'-cyclopropane).When heated the latter undergoes isomerization to 3-(2-chloroethyl)chlorobenzene, and in the presence of nucleophiles (alcohols, amines) it is converted into 3-(2-alkoxyethyl)chlorobenzenes and N-substituted 3-(2-aminoethyl)chlorobenzenes respectively.
Molchanov, A. P.,Vorob'eva, I. S.,Koroleva, L. B.,Kostikov, R. R.
p. 2186 - 2189
(2007/10/02)

WITTIG-REAKTION VON TRIPHENYLPHOSPHONIO-ALKYLIDEN MIT SUBSTITUIERTEN BENZALDEHYDEN: HAMMETT-BEZIEHUNG UND TEILWEISE REVERSIBILITAT DER ADDUKT-BILDUNG
Bei Abwesenheit loslicher Lithium-Salze vereinigen sich Triphenylphosphonio-methylid und -ethylid bereits bei -75 deg C mit Aldehyden. Elektronenanziehende Liganden beschleunigen, elektronenspendende Liganden verzogern die Anlagerung der Ylide an die substituierten Benzaldehyde.Die Addukte(Oxaphosphetane) zerfallen erst oberhalb -30 deg C zu Olefin und Triphenylphosphinoxid.Wird vor dem Zerfall ein zweiter Aldehyd oder ein zweites Ylid zugesetzt, so findet ein teilweiser Austausch der Komponenten statt.
Piskala, Alois,Rehan, Abdul Hamid,Schlosser, Manfred
p. 3539 - 3551
(2007/10/02)

Pyridinium Ylides Derived from Pyryliums and Amines and a Novel Rearrangement of 1-Vinyl-1,2-dihydropyridines
1-Benzyl-2,4-diphenylpyridiniums with benzaldehydes give oxazolopyridines which are dehydrated to 1-styryl derivatives.On pyrolysis the 1-styryl-1,2-dihydropyridine 21a gave 2,4,6-triphenylpyridine and m-chlorostyrene by a ring-enlargement-ring-contraction mechanism: this is a general reaction of 1-vinyl-1,2-dihydropyridines.
Katritzky, Alan R.,Chermprapai, Amornsri,Patel, Ranjan C.,Tarraga-Tomas, Alberto
p. 492 - 497
(2007/10/02)