- On the planarity of styrene and its derivatives: The molecular structures of styrene and (Z)-β-bromostyrene as determined by ab initio calculations and gas-phase electron diffraction
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The molecular structures of styrene and (Z)-β-bromostyrene have been studied in the gas phase at nozzle temperatures of 303 and 338 K respectively. For both molecules the electron diffraction data were consistent with the results from ab initio calculatio
- Cochran, John C.,Hagen, Kolbjorn,Paulen, Gunnar,Shen, Quang,Tom, Samson,Traetteberg, Marit,Wells, Christopher
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- Regio- and stereoselective synthesis of bromoalkenes by homolytic hydrobromination of alkynes with hydrogen bromide
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Homolytic hydrobromination of terminal and internal alkynes with a commercially available solution of hydrogen bromide in acetic acid has been investigated for regio- and stereoselective synthesis of bromoalkenes. Under an aerobic atmosphere at room temperature, the reaction of ethynylarenes with a small excess of HBr efficiently gave (2-bromoethenyl)arenes with good to high E-selectivity. (Alk-1-ynyl)arenes, or internal alkynes bearing both phenyl and alkyl groups at the sp-carbons also underwent the air-initiated hydrobromination to exhibit high Z-selectivity under kinetic conditions using a half equivalent of HBr.
- Kumaki, Wataru,Kinoshita, Hidenori,Miura, Katsukiyo
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- Illuminatinganti-hydrozirconation: controlled geometric isomerization of an organometallic species
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A general strategy to enable the formalanti-hydrozirconation of arylacetylenes is reported that mergescis-hydrometallation using the Schwartz Reagent (Cp2ZrHCl) with a subsequent light-mediated geometric isomerization atλ= 400 nm. Mechanistic delineation of thecontra-thermodynamic isomerization step indicates that a minor reaction product functions as an efficientin situgenerated photocatalyst. Coupling of theE-vinyl zirconium species with an alkyne unit generates a conjugated diene: this has been leveraged as a selective energy transfer catalyst to enableE→Zisomerization of an organometallic species. Through anUmpolungmetal-halogen exchange process (Cl, Br, I), synthetically useful vinyl halides can be generated (up toZ?:?E= 90?:?10). This enabling platform provides a strategy to access nucleophilic and electrophilic alkene fragments in both geometric forms from simple arylacetylenes.
- Gilmour, Ryan,Hostmann, Theresa,Nevesely, Tomá?
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p. 10643 - 10648
(2021/08/20)
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- Visible light-mediated metal-free double bond deuteration of substituted phenylalkenes
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Various bromophenylalkenes were reductively photodebrominated by using 1,3-dimethyl-2-phenyl-1H-benzo-[d]imidazoline (DMBI) and 9,10-dicyanoanthracene. With deuterated DMBI analogs (the most effective was DMBI-d11), satisfactory to excellent isotopic yields were obtained. DMBI-d11 could also be regenerated from the reaction mixtures with a recovery rate of up to 50%. The combination of the photodebromination reaction with conventional methods for bromoalkene synthesis enables sequential monodeuteration of a double bond without the necessity of a metal catalyst. This journal is
- Iakovenko, Roman,Hlavá?, Jan
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p. 440 - 446
(2021/01/28)
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- Chemical validation of a druggable site on Hsp27/HSPB1 using in silico solvent mapping and biophysical methods
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Destabilizing mutations in small heat shock proteins (sHsps) are linked to multiple diseases; however, sHsps are conformationally dynamic, lack enzymatic function and have no endogenous chemical ligands. These factors render sHsps as classically “undruggable” targets and make it particularly challenging to identify molecules that might bind and stabilize them. To explore potential solutions, we designed a multi-pronged screening workflow involving a combination of computational and biophysical ligand-discovery platforms. Using the core domain of the sHsp family member Hsp27/HSPB1 (Hsp27c) as a target, we applied mixed solvent molecular dynamics (MixMD) to predict three possible binding sites, which we confirmed using NMR-based solvent mapping. Using this knowledge, we then used NMR spectroscopy to carry out a fragment-based drug discovery (FBDD) screen, ultimately identifying two fragments that bind to one of these sites. A medicinal chemistry effort improved the affinity of one fragment by ~50-fold (16 μM), while maintaining good ligand efficiency (~0.32 kcal/mol/non-hydrogen atom). Finally, we found that binding to this site partially restored the stability of disease-associated Hsp27 variants, in a redox-dependent manner. Together, these experiments suggest a new and unexpected binding site on Hsp27, which might be exploited to build chemical probes.
- Makley, Leah N.,Johnson, Oleta T.,Ghanakota, Phani,Rauch, Jennifer N.,Osborn, Delaney,Wu, Taia S.,Cierpicki, Tomasz,Carlson, Heather A.,Gestwicki, Jason E.
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- Stable and Highly Regioselective Anionic Polymerization of (Z)-1-Phenyl[3]dendralene
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The anionic polymerization of (Z)-1-phenyl[3]dendralene (1Z-P3D) in THF with potassium naphthalenide (K-Naph) as an initiator was investigated. At -78 °C, a polymer of predictable molecular weight and narrow molecular-weight distribution (Mw/Mn = 1.26) was obtained quantitively in 24 h. The active chain-end carbanion derived from 1Z-P3D was significantly stabilized by conjugation with a phenyl substituent at the C1 position of the monomer; side reactions such as nucleophilic addition to the double bond in other polymer main chains were not observed over a wide temperature range (-78-0 °C). The microstructure of the obtained poly(1Z-P3D) contained a predominant amount of the 1,4 structure (>90%). Thus, the polymerizability of 1Z-P3D was different from that of previously reported 2-phenyl[3]dendralene (P3D), in terms of the nucleophilicity of the active chain end and regioselectivity in the propagation reaction.
- Miya, Masamitsu,Takagi, Tsukasa,Takenaka, Katsuhiko,Toda, Tomoyuki
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p. 4326 - 4332
(2021/05/29)
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- Method for synthesizing beta-bromostyrene through metal-free catalysis
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The invention discloses a method for synthesizing beta-bromostyrene through metal-free catalysis, and belongs to the technical field of organic chemistry. Substituted styrene 1 is used as a raw material and is reacted in the presence of a bromination reagent, sodium persulfate and dichloroethane, and the beta-bromostyrene compound 2 can be obtained in one step. The method is capable of solving thetechnical problem that in the traditional synthesis method, conversion into alkenyl boron, alkenyl silicon and other intermediates under the catalysis of noble metals and then further halogenation are needed; the defects of expensive reaction reagent, high catalytic cost, complex operation, incapability of large-scale preparation and the like in the traditional preparation method are avoided; byadopting the method, a series of beta-bromostyrene compounds can be obtained, and the method has a potential application prospect.
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Paragraph 0023-0028; 0031-0033
(2020/02/06)
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- Facile Synthesis of β-Bromostyrenes by Direct Bromination of Styrenes with N -Bromosuccinimide and Sodium Persulfate
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A new, direct, efficient, and transition-metal-free method is reported for the synthesis of β-bromostyrenes from styrenes by using N -bromosuccinimide as the brominating reagent and sodium persulfate (Na 2S 2O 8) as the oxidant. This convenient and concise reaction is practical, operationally simple, and can be adapted for large-scale syntheses.
- Chen, Xuenian,Gao, Yan,Jing, Yi,Ma, Yan-Na,Zhao, Qianyi
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supporting information
(2020/09/09)
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- Photocatalytic Isomerization of Styrenyl Halides: Stereodivergent Synthesis of Functionalized Alkenes
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An efficient and general method for the isomerization of styrenyl halides under different photocatalytic conditions (fac-Ir(ppy)3 in methanol for E to Z isomerization and fluorescein in 1,4-dioxane for Z to E isomerization, respectively) is disclosed. A series of stereospecific transformations constitute preliminary validation of this strategy in the synthesis of functionalized alkenes, including two diaryl alkenes, a styrenyl boronic ester and an enyne. The photocatalytic isomerization and subsequent cross coupling reaction can be run in a one-pot manner. The stereodivergent synthesis of all four isomers of a conjugated diene, as well as the antitumor agent DMU-212 and its (Z)-isomer highlights the synthetic applicability of this method.
- Zhang, Hao,Xu, Qing,Yu, Lei,Yu, Shouyun
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supporting information
p. 1472 - 1477
(2019/11/03)
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- A Facile Access to trans -3-Styryl-4-hydrazinocyclopentenes via Palladium-Catalyzed Ring Opening of Diazanorbornenes with (Z)-β-Bromostyrenes/2,3-Dibromohydrocinnamic Acids
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trans -3-Styryl-4-hydrazinocyclopentenes have been synthesized via palladium-catalyzed desymmetrization of diazanorbornenes with (Z)-β-bromostyrenes. The reaction also works well with (Z)-β-bromostyrenes generated in situ from 2,3-dibromohydrocinnamic acids. The synthesized hydrazinocyclopentenes provide an easy route towards synthetic intermediates of many scaffolds of biological potential.
- Saranya,Chand, S. Sarath,Gopalan, Greeshma,Jijitha,Radhakrishnan
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p. 184 - 192
(2017/10/13)
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- Ir-Catalyzed Intramolecular Transannulation/C(sp2)-H Amination of 1,2,3,4-Tetrazoles by Electrocyclization
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An efficient strategy for the intramolecular denitrogenative transannulation/C(sp2)-H amination of 1,2,3,4-tetrazoles bearing C8-substituted arenes, heteroarenes, and alkenes is described. The process involves the generation of the metal-nitrene intermediate from tetrazole by the combination of [CpIrCl2]2 and AgSbF6. It has been shown that the reaction proceeds via an unprecedented electrocyclization process. The method has been successfully applied for the synthesis of a diverse array of α-carbolines and 7-azaindoles.
- Das, Sandip Kumar,Roy, Satyajit,Khatua, Hillol,Chattopadhyay, Buddhadeb
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supporting information
p. 8429 - 8433
(2018/07/09)
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- Direct Access to Aryl Bis(trifluoromethyl)carbinols from Aryl Bromides or Fluorosulfates: Palladium-Catalyzed Carbonylation
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A palladium-catalyzed carbonylative approach for the direct conversion of (hetero)aryl bromides into their α,α-bis(trifluoromethyl)carbinols is described, and it employs only stoichiometric amounts of carbon monoxide and trifluoromethyltrimethylsilane. In addition, aryl fluorosulfates proved highly compatible with these reaction conditions. The method is tolerant of a diverse set of functional groups, and it is adaptable to late-stage carbon-isotope labeling.
- Domino, Katrine,Veryser, Cedrick,Wahlqvist, Benjamin A.,Gaardbo, Cecilie,Neumann, Karoline T.,Daasbjerg, Kim,De Borggraeve, Wim M.,Skrydstrup, Troels
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supporting information
p. 6858 - 6862
(2018/05/08)
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- TsNBr2 promoted decarboxylative bromination of α,β-unsaturated carboxylic acids
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A rapid process for decarboxylative bromination of α,β-unsaturated carboxylic acids have been developed using N,N-dibromo-p-toluenesulfonamide (TsNBr2). Treatment of cinnamic acids with TsNBr2 in presence of potassium carbonate in acetonitrile produces corresponding β-bromostyrenes at room temperature. Exclusive formation of (E)-β-bromostyrenes was observed in a stereoselective manner within a very short period of time (5–15 min). This method was further extended for obtaining 1-bromoalkynes from corresponding propiolic acids. Instantaneous formation of bromoalkynes was observed when the reaction was carried out in presence of DBU as a base in acetonitrile at room temperature. A wide variety of cinnamic acids and propiolic acids could be converted to corresponding β-bromostyrenes and 1-bromoalkynes respectively under mild reaction condition with high to excellent yield.
- Hazarika, Debojit,Phukan, Prodeep
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p. 4593 - 4596
(2018/11/23)
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- cis-β-Bromostyrene derivatives from cinnamic acids via a tandem substitutive bromination-decarboxylation sequence
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cis-β-Bromostyrene derivatives were synthesized stereospecifically from cinnamic acids through β-lactone intermediates. The synthetic sequence did not require the purification of the β-lactone intermediates although they were found to be stable and readily purified in most cases.
- Tang, Khanh G.,Kent, Greggory T.,Erden, Ihsan,Wu, Weiming
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p. 3894 - 3896
(2017/09/15)
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- Stereoselective Synthesis of Vinyl Iodides through Copper(I)-Catalyzed Finkelstein-Type Halide-Exchange Reaction
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An efficient method for the stereoselective synthesis of vinyl iodides is described. The reactions of vinyl bromides with potassium iodide proceed smoothly in the presence of a copper catalyst under mild reaction conditions to produce the corresponding vinyl iodides stereospecifically and in satisfactory to excellent yields.
- Feng, Xiujuan,Zhang, Haixia,Lu, Wenbo,Yamamoto, Yoshinori,Almansour, Abdulrahman I.,Arumugam, Natarajan,Kumar, Raju Suresh,Bao, Ming
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supporting information
p. 2727 - 2732
(2017/06/13)
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- A stereoselective synthesis of (E)- or (Z)-β-arylvinyl halides via a borylative coupling/halodeborylation protocol
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A new stereoselective method for the synthesis of (E)-β-arylvinyl iodides and (E)- or (Z)-β-arylvinyl bromides from styrenes and vinyl boronates on the basis of a one-pot procedure via borylative coupling/halodeborylation is reported. Depending on the halogenating agent as well as the mode of the halodeborylation reaction, (E) or (Z) isomers are selectively formed.
- Szyling, Jakub,Franczyk, Adrian,Pawlu?, Piotr,Marciniec, Bogdan,Walkowiak, J?drzej
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p. 3207 - 3215
(2017/04/21)
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- Palladium-Catalyzed Two-Component Domino Coupling Reaction of (Z)-β-Bromostyrenes with Norbornenes: Synthesis of 1,5-Enynes
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Polyfunctional molecules, 1,5-enynes, have been achieved via a palladium(0)-catalyzed domino coupling reaction of (Z)-β-bromostyrenes with norbornenes in the presence of cesium carbonate and N,N-dimethylformamide. The process involves a double Heck-type procedure, two-fold C(sp2) H activation and formation of two carbon-carbon bonds. There are possibilities of diversified transformation for the domino coupling of (Z)-β-bromostyrenes with norbornenes, the procedure is successfully driven to 1,5-enynes via accurate adjustment of the reaction conditions. (Figure presented.) .
- Mao, Jiangang,Li, Huifang,Wen, Herui,Li, Min,Fan, Xiaolin,Bao, Weiliang
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p. 1873 - 1879
(2016/07/06)
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- Preparation of Vinyl Arenes by Nickel-Catalyzed Reductive Coupling of Aryl Halides with Vinyl Bromides
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This work emphasizes the synthesis of substituted vinyl arenes by reductive coupling of aryl halides with vinyl bromides under mild and easy-to-operate nickel-catalyzed reaction conditions. A broad range of aryl halides, including heteroaromatics, and vinyl bromides were employed to yielding products in moderate to excellent yields with high functional-group tolerance. The nickel-catalytic system displays good chemoselectivity between the two C(sp2)-halide coupling partners, thus demonstrating a mechanistic pathway distinct from other stepwise protocols.
- Liu, Jiandong,Ren, Qinghua,Zhang, Xinghua,Gong, Hegui
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p. 15544 - 15548
(2016/12/09)
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- Pd-Catalyzed C(sp3)-C(sp2) cross-coupling of Y(CH2SiMe3)3(THF)2 with vinyl bromides and triflates
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Pd-Catalyzed C(sp3)-C(sp2) cross-coupling of Y(CH2SiMe3)3(THF)2 with vinyl bromides and triflates has been developed for efficient synthesis of various allyltrimethylsilanes. The cross-coupling reaction was conducted at room temperature with low catalyst loading of either Pd(PPh3)4 or Pd(PPh3)2Cl2, and exhibited high efficiency and a broad substrate scope. In combination with the cross-coupling by the Lewis-acid catalyzed Hosomi-Sakurai reaction, a novel three-component one-pot cascade reaction was then accomplished to deliver homoallylic alcohols and ethers with high regioselectivity and diastereoselectivity. The three-component reaction defined the yttrium complex as a novel one-carbon synthon, which could either trigger bifunctionalization of alkenes or link two electrophiles and would find applications in organic synthesis.
- Cai, Guilong,Zhou, Zhibing,Wu, Wenchao,Yao, Bo,Zhang, Shaowen,Li, Xiaofang
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supporting information
p. 8702 - 8706
(2016/10/03)
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- LSD1 INHIBITORS AND USES THEREOF
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Provided are novel compounds of Formula (I) and pharmaceutically acceptable salts thereof, which are useful for treating a variety of diseases, disorders or conditions, associated with LSDl. Also provided are pharmaceutical compositions comprising the novel compounds of Formula (I), pharmaceutically acceptable salts thereof, and methods for their use in treating one or more diseases, disorders or conditions, associated with LSDl.
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Paragraph 00357-00358
(2016/11/17)
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- Ohmic Heating and Ionic Liquids in Combination for the Indium-Promoted Synthesis of 1-Halo Alkenyl Compounds: Applications to Pd-Catalysed Cross-Coupling Reactions
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We have explored the combination of ohmic heating (ΩH) with ionic liquids for indium-promoted reactions and report herein the indium-promoted dehalogenation of gem-dibromo alkenes and the indium-mediated reductive elimination of chlorohydrins for the synthesis of 1-halo alkenyl derivatives. Heck, Stille, Suzuki, Kumada and Sonogashira couplings of the resulting 1-halo-1-alkenes with appropriate reagents were carried out to give alkenes, dienes and enynes. We report herein the combination of ohmic heating (ΩH) with ionic liquids for the indium-promoted dehalogenation of gem-dibromo alkenes and the indium-mediated reductive elimination of chlorohydrins. The 1-halo alkenyl derivatives synthesized were then submitted to a series of cross-coupling reactions to give conjugated alkenes, dienes and enynes.
- Soengas, Raquel G.,Silva, Vera L. M.,Pinto, Joana,Rodríguez-Solla, Humberto,Silva, Artur M. S.
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- Metal-Mediated Debromination of gem-Dibromoalkenes under Mild Conditions
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We describe the facile and efficient metal-promoted reduction of C-Br bonds of gem-dibromides. When the reaction is mediated by indium, the corresponding vinyl bromides are obtained in good yields and high E-stereoselectivities. Alternatively, when the reduction is mediated by samarium diiodide, vinyl bromides are obtained in moderate yields and good Z-selectivities.
- Soengas, Raquel G.,Rodríguez-Solla, Humberto,Silva, Artur M.S.
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supporting information
p. 1096 - 1099
(2016/05/19)
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- A General Copper-Catalyzed Vinylic Halogen Exchange Reaction
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An efficient and general system for the halogen exchange reaction in alkenyl halides has been developed. Upon reaction with catalytic amounts of copper iodide and trans-N,N′-dimethylcyclohexane-1,2-diamine in the presence of tetramethylammonium chloride or bromide, a wide range of easily accessible alkenyl iodides can be smoothly transformed to their far less available chlorinated and brominated derivatives in excellent yields and with full retention of the double bond geometry. This reaction also enables the chlorination of bromoalkenes and could be extended to the use of gem-dibromoalkenes.
- Nitelet, Antoine,Evano, Gwilherm
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supporting information
p. 1904 - 1907
(2016/05/19)
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- Development of a general copper-catalyzed vinylic Finkelstein reaction—application to the synthesis of the C1–C9 fragment of laingolide B
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An efficient and broadly applicable procedure for the copper-catalyzed vinylic Finkelstein reaction is reported. Using a simple, readily available and cheap catalytic system, a broad range of alkenyl iodides and bromides can be smoothly converted to their lower homologues with high yields and full retention of the double bond geometry. Key features of this vinylic Finkelstein reaction are its broad applicability, enabling the conversion of readily available alkenyl iodides to their less available brominated and chlorinated counterparts, and the mild reaction conditions compatible with a range of highly functionalized substrates. The potential of this vinylic halogen exchange reaction in total synthesis and medicinal chemistry was demonstrated by its successful use for the synthesis of the C1–C9 fragment of laingolide B and for the late-stage modification of drug-like molecules. The extension of this halogen exchange to the acetylenic and allenic Finkelstein reactions is also reported.
- Nitelet, Antoine,Jouvin, Kévin,Evano, Gwilherm
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p. 5972 - 5987
(2016/09/16)
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- Palladium(0)-Catalyzed Methylcyclopropanation of Norbornenes with Vinyl Bromides and Mechanism Study
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An unusual methylcyclopropanation from [2 + 1] cycloadditions of vinyl bromides to norbornenes catalyzed by Pd(OAc)2/PPh3 in the presence of CH3ONa and CH3OH has been established. A methylcyclopropane subunit was installed by a 3-fold domino procedure involving a key protonation course. Preliminary deuterium-labeling studies revealed that the proton came from methyl of CH3OH and also exposed an additional hydrogen/deuterium exchange process. These two proton-concerned reactions were fully chemoselective.
- Mao, Jiangang,Xie, Hujun,Bao, Weiliang
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p. 3678 - 3681
(2015/08/18)
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- Palladium(0)-catalyzed methylenecyclopropanation of norbornenes with vinyl bromides
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Highly strained methylenecyclopropane derivatives have been achieved via a novel and efficient Pd(0)-catalyzed domino reaction. The formal [2 + 1] cycloaddition reaction of vinyl bromides to norbornenes involves a Heck-type coupling and a C(sp2)-H bond activation.
- Mao, Jiangang,Bao, Weiliang
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p. 2646 - 2649
(2014/06/09)
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- Palladium-catalyzed [2+1+1] annulation of norbornenes with (z)-bromostyrenes: Synthesis of bismethylenecyclobutanes via twofold C(sp2)-H bond activation
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The first Pd-catalyzed intermolecular [2+1+1] annulation reaction of (Z)-bromostyrene derivatives and norbornenes has been realized. Bismethylenecyclobutane derivatives were obtained with high yields. The domino coupling reaction involves a double Heck-type coupling process, twofold C(sp2)-H bond activation and formation of three carbon-carbon bonds.
- Mao, Jiangang,Bao, Weiliang
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p. 15726 - 15729
(2015/01/08)
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- Stereoselective synthesis of (Z)-β-arylvinyl bromides from anti-2,3-dibromo-3-arylpropanoic acids
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A novel method for the stereoselective synthesis of (Z)-β-arylvinyl bromides in excellent yields by debrominative decarboxylation of anti-2,3-dibromo-3-arylpropanoic acids using NaN3 was developed. This facile transformation was achieved under room temperature for 1-2 h.
- Xv, Wenjing,Zhang, Wensheng,Zhang, Fei,Kuang, Chunxiang
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p. 115 - 117
(2014/03/21)
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- H-β-zeolite catalyzed synthesis of β-bromostyrenes from styrene bromohydrins
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Synthesis of β-bromostyrenes from styrene bromohydrins using H-β-zeolite as catalyst under moderate conditions is reported. The catalyst could be regenerated and reused up to three consecutive cycles.
- Pappula, Venkatanarayana,Donthiri, Ramachandra Reddy,Darapaneni, Chandra Mohan,Subbarayappa, Adimurthy
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supporting information
p. 1793 - 1795
(2014/03/21)
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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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- Formation of quaternary stereogenic centers by copper-catalyzed asymmetric conjugate addition reactions of alkenylaluminums to trisubstituted enones
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Alkenylaluminums undergo asymmetric copper-catalyzed conjugate addition (ACA) to β-substituted enones allowing the formation of stereogenic all-carbon quaternary centers. Phosphinamine-copper complexes proved to be particularly active and selective compared with phosphoramidite ligands. After extensive optimization, high enantioselectivities (up to 96 % ee) were obtained for the addition of alkenylalanes to β-substituted enones. Two strategies for the generation of the requisite alkenylaluminums were explored allowing for the introduction of aryl- and alkyl-substituted alkenyl nucleophiles. Moreover, alkyl-substituted phosphinamine (SimplePhos) ligands were identified for the first time as highly efficient ligands for the Cu-catalyzed ACA. Chiral synthesis made easy: The copper-catalyzed conjugate addition of alkenylaluminum reagents to 3-substituted cyclic enones allows for the formation of all-carbon chiral quaternary centers (see scheme; CuTC=copper(I) thiophene-2-carboxylate). Chiral phosphinamine (SimplePhos) ligands were found to be highly efficient for this transformation.
- Mueller, Daniel,Alexakis, Alexandre
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p. 15226 - 15239
(2013/11/06)
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- Nickel(II)-magnesium-catalyzed cross-coupling of 1,1-dibromo-1-alkenes with diphenylphosphine oxide: One-pot synthesis of (E)-1-alkenylphosphine oxides or bisphosphine oxides
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A novel nickel(II)-magnesium-mediated cross-coupling of diphenylphosphine oxide with a variety of 1,1-dibromo-1-alkenes has been developed, which provides a powerful and general methodology for the stereoselective synthesis of various (E)-1-alkenylphosphine oxides or bisphosphine oxides, with operational simplicity of the procedure, good to high yields and broad substrate applicability. Mechanistic studies reveal that the reaction might involve a Hirao reduction, cross-coupling and Michael addition. Copyright
- Liu, Liu,Wang, Yulei,Zeng, Zhiping,Xu, Pengxiang,Gao, Yuxing,Yin, Yingwu,Zhao, Yufen
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p. 659 - 666
(2013/04/10)
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- On the Origin of E/Z Selectivity in the Modified Julia Olefination - Importance of the Elimination Step
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The mechanism and origin of high E selectivity in the modified Julia olefination of aromatic aldehydes have been explored by computational and experimental means. Reversibility of addition and hence selectivity of the formation of sulfinate 5 is very variable and depends on the nature of the sulfone substrate. However, in all cases, elimination occurs through a concerted antiperiplanar and synperiplanar mechanism for sulfinates anti-5 and syn-5, respectively. Both syn and anti diastereomeric pathways thus lead preferentially to the (E)-alkene. Copyright
- Robiette, Raphael,Pospisil, Jiri
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supporting information
p. 836 - 840
(2013/03/29)
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- A new entry of highly nucleophilic CHBr3-TiCl4-Mg system for the stereoselective synthesis of 1-alkenyl bromides
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This TiCl4-Mg promoted coupling of CHBr3 with various aldehydes and ketones, especially in sterically hindered or enolizable ketones, provides a simple, practical, and stereoselective carbonyl-bromomethylenation leading primarily to (E)-vinyl bromides.
- Bhorge, Yeshwant Ramchandra,Chang, Su-Haur,Chang, Cheng-Ta,Yan, Tu-Hsin
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experimental part
p. 4846 - 4851
(2012/08/07)
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- Palladium-catalyzed oxidative intramolecular C-C bond formation via double sp2 C-H activation between the 2-position of imidazoles and a benzene ring
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Oxidative intramolecular C-C bond formation via double sp2 C-H activation between the 2-position of imidazoles and a benzene ring catalyzed by palladium(II) has been developed, which provides an atom-economical, concise and efficient methodology to synthesize imidazole- or benzimidazole-fused isoquinoline polyheteroaromatic compounds. Copyright
- Sun, Manman,Wu, Huandong,Zheng, Junnan,Bao, Weiliang
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supporting information; experimental part
p. 835 - 838
(2012/05/20)
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- An efficient, overall [4+1] cycloadditon of 1,3-dienes and nitrene precursors
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Intermolecular cycloadditions of conjugated dienes and nitrene precursors usually produce aziridines. A generally useful method was lacking to directly provide the [4+1] cycloadducts, 3-pyrrolines. We have realized this transformation by using an uniquely active catalyst, copper(II) 1,1,1,5,5,5-hexafluoroacetylacetonate ([Cu(hfacac)2]). The method is applicable to a wide array of dienes with good yields. When 1,4-disubsituted dienes are used as substrates, good-to-excellent cis or trans selectivity can be obtained. Interestingly, the cis or trans preference depends on the nature of the substituents, rather than diene geometry. Mechanistic studies reveal that the [4+1] cycloaddition proceeds through diene aziridination and subsequent ring expansion. Among common copper catalysts, only [Cu(hfacac)2] can efficiently catalyze both steps, which explains the unique efficiency of the catalyst.
- Wu, Qiong,Hu, Jian,Ren, Xinfeng,Zhou, Jianrong
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supporting information; experimental part
p. 11553 - 11558
(2011/11/29)
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- An efficient microwave-promoted route to (Z)-stilbenes from trans-cinnamic acids: Synthesis of combretastatin A-4 and analogues
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cis-Stilbenes were synthesized from trans-cinnamic acids, involving ethylenic-bond bromination and a subsequent one-pot microwave-promoted stereoselective debrominative decarboxylation-Suzuki cross-coupling strategy. This sequence represents a useful way to prepare a variety of combretastatin A-4 derivatives.
- Bazin, Marc-Antoine,Jouanne, Marie,El-Kashef, Hussein,Rault, Sylvain
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experimental part
p. 2789 - 2794
(2010/03/03)
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- Solid-phase oxidative halodecarboxylation of β-arylacrylic acids with the ceric ammonium nitrate-alkali halide system
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The solid-phase oxidation of cinnamic, 4-methoxy- and 3,4-dimethoxycinnamic acids with Ce(NH4)2(NO3)6-MHal system leads to β-halostyrenes. Similar procedure in the absence of a metal halide results in a cleavage of the C=C bond giving the corresponding benzaldehydes.
- Nikishin,Sokova,Makhaev,Kapustina
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experimental part
p. 118 - 123
(2009/04/13)
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- Ionic liquid-promoted stereoselective synthesis of (Z)-vinyl bromides by [bmIm]OH under organic solvent-free conditions: A green approach
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A simple and easily accessible ionic liquid, 1-butyl-3-methylimidazolium hydroxide ([bmIm]OH), has been demonstrated as an efficient promoter and reaction medium for the highly stereoselective synthesis of (Z)-vinyl bromides by the debrominative decraboxylation of dibrominated α,β-unsaturated carboxylic acids in high yields. The reaction does not require either a conventional base or an organic solvent. Copyright Taylor & Francis Group, LLC.
- Ranu, Brindaban C.,Banerjee, Subhash,Gupta, Jhinuk
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p. 2869 - 2876
(2008/02/12)
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- Synthesis of (Z)-1-bromo-1-alkenes and terminal alkynes from anti-2,3-dibromoalkanoic acids by microwave-induced reaction
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(Z)-1-Bromo-1-alkenes were stereoselectively prepared in high yields in a short reaction time by microwave irradiation of the corresponding anti-2,3-dibromoalkanoic acids in a Et3N/DMF system. A one-pot synthesis of terminal alkynes and enynes from 2,3-dibromoalkanoic acids were also developed by microwave-induced reaction.
- Kuang, Chunxiang,Yang, Qing,Senboku, Hisanori,Tokuda, Masao
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p. 4043 - 4052
(2007/10/03)
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- A one-pot synthesis of terminal alkynes from anti-3-aryl-2,3- dibromopropanoic acids under microwave irradiation
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A facile one-pot synthesis of terminal alkynes was achieved by microwave irradiation of a mixture of anti-3-aryl-2,3-dibromopropanoic acids, Et 3N and DMF and subsequent irradiation in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU). This method requires short reaction time (1-2 min) and gives terminal alkynes in high yields. Copyright
- Kuang, Chunxiang,Senboku, Hisanori,Tokuda, Masao
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- Stereoselective synthesis of (E)-β-arylvinyl bromides by microwave-induced Hunsdiecker-type reaction
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(E)-β-Arylvinyl bromides were readily prepared in a short reaction time (1-2 min) by microwave irradiation of the corresponding 3-arylpropenoic acids in the presence of N-bromosuccinimide and a catalytic amount of lithium acetate. Furthermore, two facile strategies for the efficient synthesis of (E)-β-bromo-4-arylethynylstyrene and (E)-β-bromo-4-arylstyrene have been developed by respectively combining Sonogashira and Suzuki coupling reaction with Hunsdiecker-type reaction. Formation of cis-α-bromo-β- lactone by microwave irradiation of cis-cinnamic acid with NBS provides a useful support for the mechanistic study of the present halodecarboxylation reaction. Georg Thieme Verlag Stuttgart.
- Kuang, Chunxiang,Yang, Qing,Senboku, Hisanori,Tokuda, Masao
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p. 1319 - 1325
(2007/10/03)
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- Stereoselective synthesis of (E)-β-arylvinyl bromides by microwave-induced reaction of anti-3-aryl-2,3-dibromopropanoic acids using an AgOAc-AcOH system
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(E)-β-Arylvinyl bromides were stereoselectively prepared in high yields by microwave irradiation of the corresponding anti-3-aryl-2,3- dibromopropanoic acids in AcOH in the presence of AgOAc for 0.5-3.0 min. (E)-β-Arylvinyl bromides were stereoselectively prepared in high yields by microwave irradiation of the corresponding anti-3-aryl-2,3-dibromo-propanoic acids in AcOH in the presence of AgOAc for 0.5-3.0 min.
- Kuang, Chunxiang,Senboku, Hisanori,Tokuda, Masao
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p. 637 - 642
(2007/10/03)
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- Benzocycloheptynedicobalt complexes by intramolecular Nicholas reactions
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Lewis acid mediated intramolecular Nicholas reactions of aryl (Z)-enyne propargyl acetate-Co2(CO)6 complexes 1 afford benzocycloheptenyne-Co2(CO)6 complexes 2 and their heterocyclic analogues.
- Ding, Yu,Green, James R.
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p. 271 - 274
(2007/10/03)
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- Structure-dependent oxidative bromination of unsaturated C-C bonds mediated by selectfluor
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A number of olefins were subjected to oxidative bromination using Selectfluor/KBr. For different types of substrates, addition, monobromine-substituted, or Hunsdiecker-Borodin reaction products can be readily afforded.
- Ye, Chengfeng,Shreeve, Jean'Ne M.
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p. 8561 - 8563
(2007/10/03)
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- On the stereochemistry of β-elimination of β-silyl azides
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Fluoride-mediated elimination of syn and anti β-silyl azides was shown to afford the corresponding (Z)- and (E)-olefins, respectively, demonstrating that β-elimination of β-silyl azides is stereospecifically anti.
- Chabaud, Laurent,Landais, Yannick
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p. 6995 - 6998
(2007/10/03)
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- Photochemical generation of a primary vinyl cation from (E)-bromostyrene: Mechanisms of formation and reaction
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The photochemistry of (E)-bromostyrene was investigated to determine the nature of the product-forming intermediates and to clarify the mechanism of formation of vinylic cations and vinylic radicals. Both a cation- and a radical-derived product are formed, and the ionic origin of the former product is demonstrated by significant scrambling of the label, starting from specifically deuterated (E)-bromostyrene. MO calculations show that the isolated incipient primary vinyl cation is not a metastable species, but that specific interaction with a counterion in combination with a polar environment makes it metastable. The effects of variation of the wavelength of irradiation, solvent polarity, temperature, and isotopic substitution all agree with a mechanism of direct heterolytic C-Br bond cleavage producing an ion pair followed by formation of a radical pair via electron transfer. The vinylic cation is proposed to stem directly from the indirectly populated lowest excited singlet state of bromostyrene with an energy of activation of 6.7 kcal/mol. Branching between proton loss and electron transfer in the resulting ion pair determines the ratio of cation- to radical-derived product. The E/Z-isomerization occurs in a separate process and does not involve C-Br bond cleavage.
- Gronheid, Roel,Zuilhof, Han,Hellings, Mark G.,Cornelisse, Jan,Lodder, Gerrit
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p. 3205 - 3215
(2007/10/03)
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- Allene synthesis by an asymmetric Baylis-Hillman style reaction on vinylphosphine oxides
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A novel reaction has been discovered with a mechanism similar to the Baylis-Hillman reaction. Reaction of a vinylic phosphine oxide with (R)-N-lithio-α-methylbenzylbenzylamine 2 in the presence of an aldehyde gave hydroxyphosphine oxides in good to moderate yields and moderate to poor enantioselectivities. The hydroxyphosphine oxides undergo the Horner-Wittig elimination reaction to produce allenes. Baylis-Hillman reactions of vinylic phosphine oxides with tertiary amines were also investigated.
- Fox,Medlock,Vosser,Warren
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p. 2240 - 2249
(2007/10/03)
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- Convenient and stereoselective synthesis of (Z)-1-bromo-1-alkenes by microwave-induced reaction
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(Z)-1-Bromo-1-alkenes were stereoselectively prepared in high yields in a short reaction time (0.2-1.0 min) by microwave irradiation of the corresponding 2,3-dibromoalkanoic acids in DMF in the presence of triethylamine.
- Kuang, Chunxiang,Senboku, Hisanori,Tokuda, Masao
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p. 3893 - 3896
(2007/10/03)
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- Facile generation of [bis(2-pyridyldimethylsilyl)methyl]lithium and its reaction with carbonyl compounds. New method for the stereoselective synthesis of vinylsilanes
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The generation of (2-PyMe2Si)2CHLi was easily accomplished by the deprotonation of (2-PyMe2Si)2CH2 using n-BuLi in Et2O. The 1H NMR analysis of (2-PyMe2Si)2CHLi in Et2O-d10 revealed the coordination of both pyridyl groups to lithium. Thus generated (2-PyMe2Si)2CHLi was found to react with a variety of aldehydes and ketones to give the corresponding vinylsilanes in extremely high yields with complete stereoselectivities (>99% E).
- Itami, Kenichiro,Nokami, Toshiki,Yoshida, Jun-Ichi
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p. 5045 - 5054
(2007/10/03)
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- Stereoselective synthesis of (E)-β-arylvinyl halides by microwave-induced Hunsdiecker reaction
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(E)-β-Arylvinyl halides were prepared in high yields in a short reaction (1-2 min) by microwave irradiation of the corresponding 3-arylpropenoic acids in the presence of N-halosuccinimide and catalytic LiOAc.
- Kuang,Senboku,Tokuda
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p. 1439 - 1442
(2007/10/03)
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