- Elucidation of reaction process through β-halogen elimination in CuCN-mediated cyanation of (E)-1-bromo-2-iodoalkene
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The previously unknown reaction process involved with metal-mediated β-halogen elimination is described, including a description of a vinylic Rosenmund-von Braun reaction of (E)-(1-bromo-2-iodobut-1-en-1-yl)benzene. We investigated the product structures on the basis of crystallographic analyses and revealed that copper cyanide would form bifurcated paths to deliver the isomeric mixtures.
- Endo, Naoki,Kanaura, Mao,Iwasawa, Tetsuo
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Read Online
- A new method for the preparation of alkynes from vinyl triflates
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Treatment of vinyl triflates with lithium diisopropylamide results in the selective formation of alkynes in moderate to high yields.
- Brummond, Kay M.,Gesenberg, Kirsten Dilzer,Kent, Joseph L.,Kerekes, Angela D.
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Read Online
- Migratory Aptitudes in Rearrangements of Destabilized Vinyl Cations
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The Lewis acid-promoted generation of destabilized vinyl cations from β-hydroxy diazo ketones leads to an energetically favorable 1,2-shift across the alkene followed by an irreversible C-H insertion to give cyclopentenone products. This reaction sequence overcomes typical challenges of counter-ion trapping and rearrangement reversibility of vinyl cations and has been used to study the migratory aptitudes of nonequivalent substituents in an uncommon C(sp2) to C(sp) vinyl cation rearrangement. The migratory aptitude trends were consistent with those observed in other cationic rearrangements; the substituent that can best stabilize a cation more readily migrates. However, density functional theory calculations show that the situation is more complex. Selectivity in the formation of one conformational isomer of the vinyl cation and facial selective migration across the alkene due to an electrostatic interaction between the vinyl cation and the adjacent carbonyl oxygen work in concert to determine which group migrates. This study provides valuable insight into predicting migration preferences when applying this methodology to the synthesis of structurally complex cyclopentenones that are differentially substituted at the α and β positions.
- Brewer, Matthias,Cleary, Sarah E.,Hensinger, Magenta J.,Hong, Xin,Qin, Zhi-Xin
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Read Online
- Direct Deamination of Primary Amines via Isodiazene Intermediates
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We report here a reaction that selectively deaminates primary amines and anilines under mild conditions and with remarkable functional group tolerance including a range of pharmaceutical compounds, amino acids, amino sugars, and natural products. An anomeric amide reagent is uniquely capable of facilitating the reaction through the intermediacy of an unprecedented monosubstituted isodiazene intermediate. In addition to dramatically simplifying deamination compared to existing protocols, our approach enables strategic applications of iminium and amine-directed chemistries as traceless methods. Mechanistic and computational studies support the intermedicacy of a primary isodiazene which exhibits an unexpected divergence from previously studied secondary isodiazenes, leading to cage-escaping, free radical species that engage in a chain, hydrogen-atom transfer process involving aliphatic and diazenyl radical intermediates.
- Berger, Kathleen J.,Driscoll, Julia L.,Yuan, Mingbin,Dherange, Balu D.,Gutierrez, Osvaldo,Levin, Mark D.
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supporting information
p. 17366 - 17373
(2021/11/04)
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- Cu2O Nanocrystals-Catalyzed Photoredox Sonogashira Coupling of Terminal Alkynes and Arylhalides Enhanced by CO2
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Herein the first visible-light-activated Sonogashira C?C coupling reaction at room temperature catalyzed by single-metal heterogeneous Cu2O truncated nanocubes (Cu2O TNCs) was developed. A wide variety of aryl halides and terminal alkynes worked well in this recyclable heterogeneous photochemical process to form the corresponding Sonogashira C?C coupling products in good yields. Mechanistic control studies indicated that CO2 enhances the formation of light-absorbing heterogeneous surface-bound CuI-phenylacetylide (λmax=472 nm), which further undergoes single-electron transfer with aryl iodides/bromides to enable Sonogashira Csp2 ?Csp bond formation. In contrast to literature-reported bimetallic TiO2-containing nanoparticles as photocatalyst, this work avoided the need of cocatalysis by TiO2. Single-metal CuI in Cu2O TNCs was solely responsible for the observed Csp2 ?Csp coupling reactions under CO2 atmosphere.
- Shanmugam, Munusamy,Sagadevan, Arunachalam,Charpe, Vaibhav Pramod,Pampana, V. Kishore Kumar,Hwang, Kuo Chu
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p. 287 - 292
(2019/11/05)
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- Binuclear Pd(I)-Pd(I) Catalysis Assisted by Iodide Ligands for Selective Hydroformylation of Alkenes and Alkynes
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Since its discovery in 1938, hydroformylation has been thoroughly investigated and broadly applied in industry (>107 metric ton yearly). However, the ability to precisely control its regioselectivity with well-established Rh- or Co-catalysts has thus far proven elusive, thereby limiting access to many synthetically valuable aldehydes. Pd-catalysts represent an appealing alternative, yet their use remains sparse due to undesired side-processes. Here, we report a highly selective and exceptionally active catalyst system that is driven by a novel activation strategy and features a unique Pd(I)-Pd(I) mechanism, involving an iodide-assisted binuclear step to release the product. This method enables β-selective hydroformylation of a large range of alkenes and alkynes, including sensitive starting materials. Its utility is demonstrated in the synthesis of antiobesity drug Rimonabant and anti-HIV agent PNU-32945. In a broader context, the new mechanistic understanding enables the development of other carbonylation reactions of high importance to chemical industry.
- Zhang, Yang,Torker, Sebastian,Sigrist, Michel,Bregovi?, Nikola,Dydio, Pawe?
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supporting information
p. 18251 - 18265
(2020/11/02)
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- Palladium-catalyzed methylation of terminal alkynes
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In this communication, a palladium-catalyzed procedure for the methylation of terminal alkynes has been developed. With N,N,N-trimethylbenzenaminium trifluoromethanesulfonate as the methyl source, various desired products were obtained in moderate to good yields. Both aromatic and aliphatic alkynes are applicable.
- Wang, Wei-Feng,Wu, Xiao-Feng
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- Synthesis of trisubstituted alkenes by Ni-catalyzed hydroalkylation of internal alkynes with cycloketone oxime esters
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A method for Ni-catalyzed hydroalkylation of internal alkynes with cycloketone oxime esters was developed. The reaction has a broad substrate scope. This hydroalkylation shows excellent regio-and stereo-selectivity. This method enables readily available starting materials to be used to access a range of cyano-substituted single-configuration trisubstituted alkenes. These are valuable feedstock chemicals and are widely used in synthetic and medicinal chemistry.
- Lu, Xiao-Yu,Liu, Chuang-Chuang,Jiang, Run-Chuang,Yan, Lu-Yu,Liu, Qi-Le,Wang, Qing-Qing,Li, Jia-Mei
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supporting information
p. 14191 - 14194
(2020/11/24)
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- Facile Access to Diverse Libraries of Internal Alkynes via Sequential Iododediazoniation/Decarboxylative Sonogashira Reaction in Imidazolium ILs without Ligand or Additive
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Convenient access to diverse libraries of internal alkynes via decarboxylative Sonogashira reaction of alkynyl-carboxylic acids with iodoarenes, employing imidazolium-ILs as solvent, along with piperidine-appended imidazolium [PAIM][NTf2] as task-specific basic IL is demonstrated, without the need for any ligand or additive. The feasibility to perform these reactions by sequential one-pot iododediazoniation/decarboxylative Sonogashira reaction is also shown, and the scope of the methods is underscored by providing 29 examples. The potential for recycling and reuse of the IL solvent is also examined.
- Prabhala, Pavankumar,Savanur, Hemantkumar M.,Kalkhambkar, Rajesh G.,Laali, Kenneth K.
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p. 2061 - 2064
(2019/03/07)
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- RETRACTED ARTICLE: Copper-Catalyzed Decarboxylative C(sp2)-C(sp3) and C(sp)-C(sp3) Coupling of Substituted Cinnamic Acids and 3-Phenyl Propiolic Acid with N-Tosyl Oxaziridines
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A mild and efficient strategy for decarboxylative C(sp2)-C(sp3) and C(sp)-C(sp3) coupling of α,β-unsaturated carboxylic acids such as substituted cinnamic acids and 3-phenyl propiolic acid with N-Tosyl oxaziridines was developed. The corresponding products were achieved in moderate to good yields with excellent stereoselectivity. Base-free and oxidant-free conditions allow good functional group tolerance. Radical inhibitors such as TEMPO and BHT completely suppressed the reactions suggesting a radical mechanism was involved. This study is supposed to broaden the frontier of oxaziridines' chemistry and to open up a novel cascade for alkylating reagents.
- Nguyen, Bich-Ngoc,Cao, Hai-Thuong
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supporting information
p. 5912 - 5915
(2019/08/07)
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- Synthesis of trisubstituted olefins via nickel-catalyzed decarboxylative hydroalkylation of internal alkynes
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A novel NiH-catalyzed decarboxylative hydroalkylation of internal alkynes has been developed. Trisubstituted olefins were obtained in moderate to good yields with good regioselectivities. The reaction involves cis addition of NiH to the internal alkyne. The reaction shows good functional-group tolerance.
- Lu, Xiao-Yu,Li, Jing-Song,Hong, Mei-Lan,Wang, Jin-Yu,Ma, Wen-Jing
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supporting information
p. 6979 - 6984
(2018/11/03)
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- Stereo-defined synthesis of differentially all-carbon tetrasubstituted alkenes derived from (E)-1-bromo-2-iodoalkenes
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An intuitive approach to differentially all-carbon tetrasubstituted olefins from a scaffold of (E)-1-bromo-2-iodoalkenes is described. The iodine atom of the scaffold selectively undertook CuTC-mediated cross-coupling reactions with organotin reagents, suppressing a side-reaction of β-halogen elimination. The resultant vinyl bromides were successfully subjected to various transformations into tetrasubstituted olefins bearing four different carbon-linked groups. The crystallographic analysis revealed that the configuration of the double bonds is fully retained in those two steps. Thus, the template strategy would provide a new entry for preparing stereo-defined tetrasubstituted alkenes.
- Endo, Naoki,Iwasawa, Tetsuo
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p. 5833 - 5840
(2017/09/08)
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- "Anti-Michael addition" of Grignard reagents to sulfonylacetylenes: Synthesis of alkynes
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In this work, the addition of Grignard reagents to arylsulfonylacetylenes, which undergoes an "anti-Michael addition", resulting in their alkynylation under very mild conditions is described. The simplicity of the experimental procedure and the functional
- Esteban, Francisco,Boughani, Lazhar,García Ruano, José L.,Fraile, Alberto,Alemán, José
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p. 3901 - 3908
(2017/07/11)
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- Nickel-catalyzed decarboxylative coupling of an alkynyl carboxylic acid with aryl iodides
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A decarboxylative coupling reaction with an alkynyl carboxylic acid and aryl iodides in the presence of a nickel catalyst was developed. When the reaction was conducted with NiCl2 (10?mol%), Xantphos (15?mol%), Mn (1.0?equiv), and Cs2CO3 (1.5?equiv), the desired diaryl alkynes were formed in moderated to good yields. Furthermore, this method does not produce the diyne, which is formed in the homocoupling of alkynyl carboxylic acids.
- Son, Yujeong,Kim, Han-Sung,Lee, Ju-Hyeon,Jang, Jisun,Lee, Chin-Fa,Lee, Sunwoo
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p. 1413 - 1416
(2017/03/17)
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- Direct Conversion of Internal Alkynes into α-Iodoenones: One-Step Collaborative Iodination and Oxidation
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The reaction of an internal alkyne with 2,6-dichloropyridine N-oxide, a nucleophilic oxidant, and electrophilic N-iodosuccinimide (NIS) simultaneously enables the direct access to versatile α-iodoenones. Electronically biased internal alkynes undergo the one-step transformation with excellent regioselectivities and with practical Z/E ratios. In comparison to the related oxidative gold catalysis using pyridine N-oxides, this reaction employs NIS as the stoichiometric ynophile instead of the soft acidic noble metal catalyst and affords products featuring an additional versatile C-I bond. Similar strategies for replacing ynophilic cationic gold(I) complexes in oxidative gold catalysis with likewise ynophilic stoichiometric electrophiles would enable the development of new synthetic methods.
- Wang, Youliang,Genoux, Alexandre,Ghorai, Subir,Chen, Hongyi,Todd, Robert,Zhang, Liming
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supporting information
p. 1417 - 1420
(2016/05/19)
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- TETRASUBSTITUTED ALKENE COMPOUNDS AND THEIR USE
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Disclosed herein are compounds, or pharmaceutically acceptable salts thereof, and methods of using the compounds for treating breast cancer by administration to a subject in need thereof a therapeutically effective amount of the compounds or pharmaceutically acceptable salts thereof. The breast cancer may be an ER-positive breast cancer and/or the subject in need of treatment may express a mutant ER-α protein.
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Page/Page column 48; 81
(2016/12/22)
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- Photosensitizer-Free Visible-Light-Mediated Gold-Catalyzed 1,2-Difunctionalization of Alkynes
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Under visible-light irradiation, the gold-catalyzed intermolecular difunctionalization of alkynes with aryl diazonium salts in methanol affords a variety of α-aryl ketones in moderate to good yields. In contrast to previous reports on gold-catalyzed reactions that involve redox cycles, no external oxidants or photosensitizers are required. The reaction proceeds smoothly under mild reaction conditions and shows broad functional-group tolerance. Further applications of this method demonstrate the general applicability of the arylation of a vinyl gold intermediate instead of the commonly used protodemetalation step. This step provides facile access to functionalized products in one-pot processes. With a P,N-bidentate ligand, a stable aryl gold(III) species was obtained, which constitutes the first direct experimental evidence for the commonly postulated direct oxidative addition of an aryl diazonium salt to a pyridine phosphine gold(I) complex.
- Huang, Long,Rudolph, Matthias,Rominger, Frank,Hashmi, A. Stephen K.
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supporting information
p. 4808 - 4813
(2016/04/19)
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- Nickel-catalyzed three-component domino reactions of aryl grignard reagents, alkynes, and aryl halides producing tetrasubstituted alkenes
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Three-component reaction of aryl Grignard reagents, alkynes, and aryl halides in the presence of 1 mol % of NiCl2 proceeded sequentially through carbomagnesiation of the alkyne followed by cross-coupling of the resulting alkenyl Grignard reagent with aryl halide to give tetrasubstituted alkenes in high yields.
- Xue, Fei,Zhao, Jin,Hor, T. S. Andy,Hayashi, Tamio
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supporting information
p. 3189 - 3192
(2015/03/30)
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- A copper-free Sonogashira reaction using nickel ferrite as catalyst in water
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The Sonogashira reaction using nickel ferrite nanoparticles as catalyst and under copper-free conditions was investigated in water as a green solvent. Various types of aryl and alkyl halides were successfully coupled with phenyl acetylene under the optimized reaction conditions with very good to excellent yields at a short time. The catalyst is easily recoverable and can be reused for several runs with a good turnover number.
- Moghaddam, Firouz Matloubi,Tavakoli, Ghazal,Rezvani, Hamid Reza
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- Copper-catalyzed aerobic oxidative transformation of ketone- Derived N-tosyl hydrazones: An entry to alkynes
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A novel strategy involving Cu-catalyzed oxidative transformation of ketone-derived hydrazone moiety to various synthetic valuable internal alkynes and diynes has been developed. This method features inexpensive metal catalyst, green oxidant, good functional group tolerance, high regioselectivity and readily available starting materials. Oxidative deprotonation reactions were carried out to form internal alkynes and symmetrical diynes. Cross-coupling reactions of hydrazones with halides and terminal alkynes were performed to afford functionalized alkynes and unsymmetrical conjugated diynes. A mechanism proceeding through a Cu-carbene intermediate is proposed for the CC triple bond formation.
- Li, Xianwei,Liu, Xiaohang,Chen, Huoji,Wu, Wanqing,Qi, Chaorong,Jiang, Huanfeng
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p. 14485 - 14489
(2015/02/05)
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- Re/Mg bimetallic tandem catalysis for [4+2] annulation of benzamides and alkynes via C-H/N-H functionalization
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A rhenium-magnesium cocatalyzed [4+2] annulation of benzamides and alkynes via C-H/N-H functionalization is described. The reaction features a divergent and high level of diastereoselectivities, which are readily switchable by subtle tuning of reaction conditions. Thus, a wide range of both cis- and trans-3,4-dihydroisoquinolinones is expediently synthesized in a highly atom-economical manner. Moreover, mechanistic studies unraveled a tandem mode of action between rhenium and magnesium in the catalytic cycles.
- Tang, Qiuzheng,Xia, Dexin,Jin, Xiqing,Zhang, Qing,Sun, Xiao-Qiang,Wang, Congyang
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supporting information
p. 4628 - 4631
(2013/05/21)
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- Gold-catalyzed isomerization of unactivated allenes into 1,3-dienes under ambient conditions
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We have developed a gold-catalyzed isomerization of unactivated allenes into 1,3-dienes with nitrosobenzene as an additive. This reaction proceeded almost exclusively at room temperature for highly substituted allenes. The utility of this reaction is manifested by the development of one-pot [4+2]-cycloaddition of allenes and reactive alkenes.
- Ting, Chun-Ming,Hsu, Yi-Ling,Liu, Rai-Shung
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supporting information; experimental part
p. 6577 - 6579
(2012/07/31)
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- Silver triflate-catalyzed cyclopropenation of internal alkynes with donor-/acceptor-substituted diazo compounds
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Silver triflate was found to be an efficient catalyst for the cyclopropenation of internal alkynes using donor-/acceptor-substituted diazo compounds as carbenoid precursors. Highly substituted cyclopropenes, which cannot be synthesized directly via rhodium(II)-catalyzed carbenoid chemistry, can now be readily accessed.
- Briones, John F.,Davies, Huw M. L.
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supporting information; experimental part
p. 3984 - 3987
(2011/09/16)
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- Lewis acid activation of molybdenum nitrides for alkyne metathesis
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The substantial kinetic barrier to molybdenum nitride-alkyne metathesis is facilitated by precomplexation of the borane Lewis acid B(C6F 5)3, providing convenient access to metathesis-active molybdenum alkylidynes. Spectroscopic and X-ray structural analysis suggest MoN bond weakening upon borane complexation.
- Finke, Aaron D.,Moore, Jeffrey S.
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supporting information; experimental part
p. 7939 - 7941
(2011/01/04)
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- Experimental and theoretical study of tunable 1,3-lithium shift of proparglie/allem lie species, transmetallation and Pd-catalyzed crosscoupling reactions
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The highly selective tuning of the isomerization from 1-arylalka1,2-dien-l- yllithium to l-arylalka-1,2dien-3-yllithium has been realized in the deprotonation of 1-arylalk-l-yne (conditions A and B) and carbolithiation of l-arylbut-3-en-l-yne with alkyllithium (conditions C and D). Subsequent transmetallation and Pd-catalyzed Negishi coupling reactions afforded 1,1-diaryl or 1,3-diaryl alienes with high selectivity. Deuterium-labeling cross experiments indicated that an intermolecular lithiation process occurred in both 1,3-lithium shift conditions (conditions B and D). 1-Arylalka1,2-diene was confirmed experimentally to be the intermediate. A computational study at the B3LYP level for the isomerization indicated that the acidity of H at the 3-position is higher than that of the H at the 1-position of 1phenyl-l,2-butadiene. Under conditions B, (Pr2NH acts as a proton carrier to finish the 1,3-lithium shift. The overall activation barrier for the rate-determining step in the solvated models is ≈ 21.0 kcal mol-1, indicating that the isomerization is reasonable at room temperature. For the isomerization under conditions D, DFT calculations indicated that the addition of TMEDA (tetramethylethylenediamine) and HMPA (hexamethylphosphoramide) changes the global minimum of the system; among the possible mechanisms (P1-P5) considered, the mechanism catalyzed by dilithiated species (P5) is the most probable one. The overall activation barriers for isomerization in THF and TMEDA solvated models are 22.6 and 19.7 kcal mol-1, respectively, proving that the isomerization may proceed at RT in THF or at -78°C with TMEDA, due to the fact that the solvation of the additives may increase the concentration of 1-phenyl1,2-butadienyllithium monomer by a deaggregation effect.
- Zhao, Jinbo,Liu, Yu,He, Qiwen,Li, Yuxue,Ma, Shengming
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scheme or table
p. 11361 - 11372
(2010/05/18)
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- Thieme Chemistry Journal Awardees - Where are they now? A general one-step synthesis of alkynes from enolisable carbonyl compounds
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Terminal and internal acetylenes were obtained in good to excellent isolated yields from carbonyl compounds by converting the carbonyl functionality into the enol nonaflate intermediate followed by elimination to give the C-C triple bond. The one-pot transformations were uniformly induced by phosphazene bases combined with mildly electrophilic nonafluorobutane-1-sulfonyl fluoride. The method is the most general among those reported to date as it applies to both acyclic ketones and aldehydes. Only moderate kinetic regioselectivity in favour of alk-1-yne achieved from methyl n-alkyl ketone represents a limitation of the method. In all the other instances, individual acetylenic products were obtained. Georg Thieme Verlag Stuttgart.
- Lyapkalo, Ilya M.,Vogel, Michael A. K.,Boltukhina, Ekaterina V.,Vav?ík, Ji?í
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scheme or table
p. 558 - 561
(2009/07/09)
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- Iron-catalyzed arylmagnesiation of aryl(alkyl)acetylenes in the presence of an N-heterocyclic carbene ligand
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(Chemical Equation Presented) Addition of arylmagnesium bromides to aryl(alkyl)acetylenes proceeded in the presence of an iron catalyst and a N-heterocyclic carbene ligand to give high yields of the corresponding alkenylmagnesium reagents, which were transformed into tetrasubstituted alkenes by subsequent treatment with electrophiles.
- Yamagami, Takafumi,Shintani, Ryo,Shirakawa, Eiji,Hayashi, Tamio
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p. 1045 - 1048
(2007/10/03)
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- A fine-tuned molybdenum hexacarbonyl/phenol initiator for alkyne metathesis
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A new, highly potent activator for molybdenum hexacarbonyl and 2-fluorophenol is described. An "instant" catalyst formed in situ from molybdenum hexacarbonyl and 2-fluorophenol shows high activity for cross- and ring-closing alkyne metathesis reaction. The use of 2-fluorophenol can be combined with other activation methods to allow alkyne metathesis at relatively low temperature (80 °C).
- Sashuk, Volodymyr,Ignatowska, Jolanta,Grela, Karol
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p. 7748 - 7751
(2007/10/03)
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- Vinyl carbocations: Solution studies of alkenyl(aryl)iodonium triflate fragmentations
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Generation of vinyl cations is facile by fragmentation of alkenyl(aryl)iodonium trifluoromethanesulfonates. Kinetics and electronic effects were probed by 1H NMR spectroscopy in CDCl3. Products of fragmentation include six enol triflate isomers in addition to iodoarenes. The enol triflates arise from direct reaction of a triflate anion with the starting iodonium salts as well as triflate reaction with rearranged secondary cations derived from those salts. G2 calculations of the theoretical isodesmic hydride-transfer reaction between secondary vinyl cation 7 and primary vinyl cation 6 reveal that cation 6 is 17.8 kcal/mol higher in energy. Activation parameters for fragmentation of (Z)-2-ethyl-1-hexenyl(3,5-bis-trifluoromethylphenyl)iodonium triflate, 17e, were calculated using the Arrhenius equation: Ea = 26.8 kcal/mol, ΔH? = 26.2 kcal/mol, and ΔS? = 11.9 cal/mol·K. Added triflate increases the rate of fragmentation slightly, and it is likely that for most β,β-dialkyl-substituted vinylic iodonium triflates enol triflate fragmentation products are derived from three competing mechanisms: (a) vinylic SN2 substitution; (b) ligand coupling (LC); and (c) concerted aryliodonio departure and 1,2-alkyl shift leading to secondary rather than primary vinyl cations.
- McNeil,Hinkle,Rouse,Thomas,Thomas
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p. 5556 - 5565
(2007/10/03)
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- Flash vacuum pyrolysis of pyrazoles as an alternative way to study vinylcarbenes
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Flash vacuum pyrolysis (FVP) reactions of 3,5-diphenylpyrazole (1) and 3(5)-methyl-5(3)-phenylpyrazole (2) were carried out. The reaction products expected for nitrogen extrusion were formed through different rearrangements in the vinylcarbene intermediate. Kinetic parameters for nitrogen extrusion from 1 are reported. To show that FVP reactions of pyrazoles are useful to obtain vinylcarbenes, the reactions of other pyrazoles previously studied are also discussed.
- Moyano, Elizabeth L.,Yranzo, Gloria I.,Elguero, Jose
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p. 8188 - 8191
(2007/10/03)
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- Indirect electroreductive sequential radical reaction catalyzed by a Ni(II) complex. One-step preparation of functionalized (methylene)cyclopentanes
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Substituted (methylene)cyclopentanes were prepared by one-step reaction at room temperature from butynyl iodides and activated olefins by sequencing of free radical addition and cyclization reactions. The reactions, which were conducted by indirect electroreduction catalyzed by a nickel(II) complex, proceeded with modest selectivity for formation of the Z(methylene)cyclopentanes.
- Ozaki,Mitoh,Ohmori
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p. 1435 - 1440
(2007/10/03)
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- Electrolytically Induced Allene-Alkyne Isomerization
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Preparative-scale electrolyses at mercury cathodes in dimethylformamide containing tetra-n-butylammonium perchlorate have revealed that 1-phenyl-1,2-hexadiene exhibits no evidence of isomerization to form 1-phenyl-1-hexyne via an electrolytically induced, base-catalyzed rearrangement; similarly, 1-phenyl-1,2-butadiene exhibits only a slight tendency (1-2percent) to form 1-phenyl-1-butyne.In contrast, voltammetric and electrolytic experiments demonstrate that isomerization of 1-phenyl-1-butyne, 1-phenyl-1-pentyne, and 1-phenyl-1-hexyne to the corresponding allenes occurs muchmore readily.Observations from several investigations show that the extent of allene-to-alkyne rearrangement increases from 1-phenyl-1,2-hexadiene to 1-phenyl-1,2-butadiene to phenylpropadiene, whereas the reverse alkyne-to-allene isomerization decreases in significance from 1-phenyl-1-hexyne to 1-phenyl-1-pentyne to 1-phenyl-1-butyne to 1-phenyl-1-propyne.Steric and electronic factors, which affect protonation of the conjugate bases of the various starting materials at acrbons 1 and 3, can be invoked to explain these trends.
- Stemple, Joseph Z.,Peters, Dennis G.
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p. 5318 - 5323
(2007/10/02)
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- EIN EINFACHES VERFAHREN ZUR ALKYLIERUNG VON ARYLALKINEN
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Arylalkynes are alkylated in a rapid reaction and under mild conditions by alkyl iodides in the presence of powdered KOH and 18-crown-6
- Lissel, Manfred
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p. 1843 - 1844
(2007/10/02)
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- The Autoxidation of 1-Phenylalk-1-ynes. Proof of Oxirenes as Intermediates in the Oxidation of Acetylenes
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In the autoxidations of 1-phenylprop-1-yne, 1-phenylbut-1-yne, and 1-phenyl-3-methylbut-1-yne a considerable attack at the CC triple bond takes place.Both products of the oxidative cleavage of the CC bond and products formed through the corresponding oxirenes were detected.The oxirenes rearrange via the isomeric ketocarbenes to ketenes, which yield the corresponding carboxylic acids or their esters.A part of the intermediate ketenes is oxidized with decarboxylation to lower ketones.All products were identified and quantitatively determined after LiAlH4 reduction to the corresponding alcohols.
- Dao, Le Thi Anh,Blau, Karla,Pritzkow, Wilhelm,Schmidt-Renner, Wolfgang,Voerckel, Volkmar,Willecke, Lothar
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- MECHANISMES DE LA PROTONOLYSE DES ORGANO-CHROMIQUES ISSUS DE BROMURES PROPARGYLIQUES.
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The reaction of CrCl2 with propargylic bromides leads to an allenic organo-chromic derivative protonated without rearrangement by carboxylic acids.Alcohols like menthol transform this metallic to its propargylic isomer and then protonate it with rearrangement(SEi' type mechanism).
- Cazes, Bernard,Verniere, Catherine,Gore, Jacques
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p. 3501 - 3504
(2007/10/02)
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- PREPARATION OF α-TRIALKYLSILYL KETONES FROM α-PHENYLSELENO DERIVATIVES VIA THEIR SILYL ENOL ETHERS
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On treatment with metallic lithium in the presence of dimethylaminonaphthalene, trialkylsilyl enol ethers of α-phenylseleno ketones were converted into the corresponding α-trialkylsilyl ketones in good yields.
- Kuwajima, Isao,Takeda, Ryo
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p. 2381 - 2384
(2007/10/02)
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- NOUVELLE VOIE D'ACCES A DES ALLENES ET VINYLALLENES ENANTIOMERIQUEMENT ENRICHIS.
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The reduction of three racemic propargylic bromides by Hiyama's reagent (CrCl2 in THF) in the presence of protonic chiral reagents and HMPT efficiently affords optically active allenic compounds with an enantiomeric purity of 15-25 percent.
- Verniere, Catherine,Cazes, Bernard,Gore, Jacques
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p. 103 - 106
(2007/10/02)
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- KETENE-ANTHRACENE ADDUCT, A PRECURSOR OF SUBSTITUTED ACETYLENES
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The ketene-anhracene adduct 1 serves as a good precursor in the synthesis of substituted acetylenes, in wich the key step is the retro Diels-Alder reaction.
- Tarnchompoo, Bongkoch,Thebtaranonth, Yodhathai,Utamapanya, Suchada,Kasemsri, Prapani
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p. 1241 - 1242
(2007/10/02)
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