- 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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- 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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- Iridium-Catalyzed Hydrochlorination and Hydrobromination of Alkynes by Shuttle Catalysis
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Described herein are two different methods for the synthesis of vinyl halides by a shuttle catalysis based iridium-catalyzed transfer hydrohalogenation of unactivated alkynes. The use of 4-chlorobutan-2-one or tert-butyl halide as donors of hydrogen halides allows this transformation in the absence of corrosive reagents, such as hydrogen halides or acid chlorides, thus largely improving the functional-group tolerance and safety profile of these reactions compared to the state-of-the-art. This method has granted access to alkenyl halide compounds containing acid-sensitive groups, such as tertiary alcohols, silyl ethers, and acetals. The synthetic value of those methodologies has been demonstrated by gram-scale synthesis where low catalyst loading was achieved.
- Yu, Peng,Bismuto, Alessandro,Morandi, Bill
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supporting information
p. 2904 - 2910
(2020/01/25)
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- Synthesis of Highly Substituted Polyenes by Palladium-Catalyzed Cross–Couplings of Sterically Encumbered Alkenyl Bromides and N-Tosylhydrazones
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A new method for the synthesis of polysubstituted conjugated dienes is described, through the palladium-catalyzed cross-coupling between N-tosylhydrazones and alkenyl bromides. The reaction proceeds efficiently when a combination of a highly substituted bromoalkene and a hydrazone derived from a ketone are employed, pointing to the convenience of a sterically encumbered environment. This unprecedented process allows for the stereocontrolled preparation of highly substituted dienes and polyenes. (Figure presented.).
- Paraja, Miguel,Barroso, Raquel,Cabal, M. Paz,Valdés, Carlos
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p. 1058 - 1062
(2017/03/27)
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- HBr–DMPU: The First Aprotic Organic Solution of Hydrogen Bromide
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HBr and DMPU (1,3-dimethyl-3,4,5,6-tetrahydro-2-pyrimidinone) form a room-temperature-stable complex that provides a mild, effective, and selective hydrobrominating reagent toward alkynes, alkenes, and allenes. HBr–DMPU could also replace other halogenating reagents in the halo-Prins reaction, ether cleavage, and deoxy-bromination reactions.
- Li, Zhou,Ebule, Rene,Kostyo, Jessica,Hammond, Gerald B.,Xu, Bo
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supporting information
p. 12739 - 12743
(2017/09/25)
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- Regioselective Synthesis of Vinyl Halides, Vinyl Sulfones, and Alkynes: A Tandem Intermolecular Nucleophilic and Electrophilic Vinylation of Tosylhydrazones
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A diazo species is trapped in an intermolecular fashion by two independent ion species in tandem at the carbene center to install an electrophile and a nucleophile on the same carbon. This metal-free concept, which is unprecedented, has been illustrated by regioselective synthesis of a variety of vinyl halides, vinyl sulfones, and alkyne derivatives. (Chemical Equation Presented).
- Ojha, Devi Prasan,Prabhu, Kandikere Ramaiah
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- Nucleophile-selective cross-coupling reactions with vinyl and alkynyl bromides on a dinucleophilic aromatic substrate
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A nucleophile-selective cross-coupling reaction on an aromatic compound bearing two metal groups, Bpin and SnMe3, has been developed. Previously, only aryl bromides and iodides could be used as electrophilic components, but in this work, the scope could be extended to vinyl and alkynyl bromides as electrophiles. This means that the roles typical in Sonogashira couplings or Heck reactions of the aromatic ring as the dielectrophile coupling to vinyl and alkynyl metal species are reversed, which presents a new tool for organic synthesis. The first nucleophilic site to react is the stannyl group, and subsequently, a Suzuki-Miyaura cross-coupling reaction can take place on the same molecule.
- He, Lu-Ying,Schulz-Senft, Mathias,Thiedemann, Birk,Linshoeft, Julian,Gates, Paul J.,Staubitz, Anne
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supporting information
p. 2498 - 2502
(2015/04/22)
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- Metal-free regioselective hydrobromination of alkynes through CH/CBr activation
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A metal-free regioselective hydrobromination of alkynes has been developed to provide the Markovnikov-type vinyl bromides in good yields using dibromomethane/N,N-dimethylaniline as in-situ 'HBr' source. This protocol also represents an elegant example of the activation of sp2 CH and CBr bonds in one pot, in which 'HBr' is generated and transferred under mild metal-free conditions. D-incorporated experiments were employed to investigate the reaction mechanism and a plausible reaction path was proposed.
- Chen, Xiuling,Chen, Tieqiao,Xiang, Yuqiang,Zhou, Yongbo,Han, Daoqing,Han, Li-Biao,Yin, Shuang-Feng
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supporting information
p. 4572 - 4575
(2014/12/10)
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- Radical-chain oxidative addition mechanism for the reaction of an [Re(CO)5]- anion with α-bromostilbene
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E-α-Bromostilbene spontaneously reacts with Na[Re(CO)5] at 22 °C in THF to give Na[ReBr(CO)4{Z-C(Ph)CHPh}] and Na[Re 2(CO)9{Z-C(Ph)CHPh}] as the main products. Z-α-Bromostilbene is less reactive, but gives the same products. The reaction is stimulated by visible light or a source of solvated electrons (NaK2.8) and can be inhibited by a quinomethide radical trap. With an excess of Na[Re(CO)5] one can observe the initial formation of Na[ReBr(CO)4{Z-C(Ph)CHPh}] and its complete transformation into Na[Re2(CO)9{Z-C(Ph)CHPh}]. Treatment of Na[ReBr(CO) 4{Z-C(Ph)CHPh}] with CO almost quantitatively converts it to [Re(CO)5{Z-C(Ph)CHPh}], the structure of which is established by a single-crystal X-ray diffraction study. A radical-chain mechanism is proposed for the reaction comprising the following steps: (a) coupling of a Vin radical with Na[Re(CO)5], (b) CO-dissociation from the formed 19-electron radical-anion and (c) bromine atom abstraction by [Re(CO)4{Z-C(Ph) CHPh}]- from α-bromostilbene. The mechanism is confirmed by the formation of the same Na[ReBr(CO)4{Z-C(Ph)CHPh}] product in the presence of NaI. When the radical-chain process is inhibited, a slow halogenophilic reaction is observed, mainly giving the Z and E-isomers of the acylrhenate Na[Re2(CO)9{C(O)C(Ph)CHPh}].
- Sazonov, Petr K.,Ptushkin, Dmitry S.,Khrustalev, Victor N.,Kolotyrkina, Natal'Ya G.,Beletskaya, Irina P.
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p. 4223 - 4232
(2013/04/23)
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- Palladium-catalysed cross-coupling reactions of triorganoindium reagents with alkenyl halides
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The regio- and stereoselectivity of the palladium-catalysed cross-coupling reactions of indium organometallics with stereodefined 1-haloalkenes and 1,1-dihaloalkenes have been studied. Triorganoindium reagents (R3In; R = alkyl, alkenyl, aryl an
- Riveiros, Ricardo,Saya, Lucia,Sestelo, Jose Perez,Sarandeses, Luis A.
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experimental part
p. 1959 - 1966
(2009/04/03)
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- Sol-gel entrapped pyridinium hydrobromide perbromide as a recyclable bromination agent: Its application to a one-pot bromination and dehydrobromination process
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Silica sol-gel encaged pyridinium hydrobromide perbromide can be used for clean, odorless bromination of a variety of substrates, including alkenes, ketones, and arenes. The used heterogenized bromination reagent can be recharged with bromine and recycled. In the presence of sol-gel entrapped 1,5,7-triazabicyclo[4.4.0]dec-5-ene, dibromides are dehydrobrominated to give vinyl monobromides and/or alkynes. Encapsulation of the pyridinium derivative and the guanidine base within separate sol-gel matrices enables the use of both opposing reagents in one-pot reactions without their mutual destroying each other. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
- Levin, Yevgenia,Hamza, Khalil,Abu-Reziq, Raed,Blum, Jochanan
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p. 1396 - 1399
(2007/10/03)
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- Halodephosphorylation of α,β-unsaturated phosphonic acid monoesters
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Reaction of α,β-ethylenic and acetylenic phosphonic acid monoesters with (biscollidine)iodine(I) or (biscollidine)bromine(I) hexafluorophosphate led to α,β-unsaturated halides by, without precedent, dephosphorylation reactions.
- Lahrache, Hind,Robin, Sylvie,Rousseau, Gérard
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p. 1635 - 1637
(2007/10/03)
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- Convenient synthesis of aryl-substituted halo olefins from aromatic ketones and acetyl halides in the presence of silica gel-supported zinc halides
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A simple and efficient procedure has been developed for the synthesis of aryl-substituted chloro and bromo olefins from aromatic ketones and acetyl halides in the presence of silica gel-supported zinc halides. The Z-isomer is selectively formed.
- Kodomari, Mitsuo,Nagaoka, Takashi,Furusawa, Yuhsuke
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p. 3105 - 3107
(2007/10/03)
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- A modified Suzuki reaction of 1,1-dibromo-1-alkenes
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The (E)-bromides in 1,1-dibromo-1-alkenes were stereoselectively coupled with aryl- or alkenylboronic acids to give the corresponding (Z)-1- Aryl(alkenyl)-1-bromo-1-alkenes. Tris(2-furyl)phosphine (TFP) was used as the ligand to palladium, and the combination of 1,4-dioxane and aqueous sodium carbonate produced the best results.
- Shen, Wang
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p. 737 - 739
(2007/10/03)
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- The Stille Reaction of 1,1-Dibromo-1-alkenes: Preparation of Trisubstituted Alkenes and Internal Alkynes
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The Stille reaction of 1,1-dibromo-1-alkenes 1 with aryl- and vinylstannanes produces different products depending on the reaction conditions. When the reaction is run in toluene or 1,4-dioxane with tris(2-furyl)phosphine (TFP) as the ligand, (Z)-bromoalkenes 2 are obtained stereospecifically in good to excellent yields with most substrates. However, 2-aryl-1,1-dibromo-1-alkenes (1e,1g) having an electron-donating methoxy group in the para- or ortho- position give poor yields. This method has been applied to the one-pot syntheses of stereospecifically trisubstituted alkenes 5. When the Stille reaction is conducted in a highly dipolar solvent (DMF), monobromides 2 and/or internal alkynes 4 are the products. The less reactive phenylstannane favors the formation of alkynes 4, regardless of which ligand is used. More reactive organostannanes (vinyl, furyl) require a very electron rich ligand, tris(4-methoxyphenyl)phosphine, for the formation of alkynes 4. This new method for internal alkyne preparation is general, requires very mild reaction conditions, and gives high yields.
- Shen, Wang,Wang, Le
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p. 8873 - 8879
(2007/10/03)
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- P(CH3NCH2CH2)3N: A Nonionic Superbase for Efficient Dehydrohalogenation
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The commercially available nonionic Superbase P(CH3NH2CH2)3N (1) is far superior to DBU for the conversion of primary and secondary alkyl halides to alkenes. A reason for the efficacy of acetonitrile as a solvent for the halides requiring extended reaction times is presented.
- Arumugam, Subramaniam,Verkade, John G.
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p. 4827 - 4828
(2007/10/03)
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- Rhodium-catalyzed reaction of aroyl chlorides with alkynes
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Aroyl chlorides react with terminal alkynes accompanied by decarbonylation in the presence of a catalytic amount of [RhCl(cod)]2 and PPh3 to give the corresponding vinyl chloride derivatives regioand stereoselectively in good yields.
- Kokubo, Ken,Matsumasa, Kenji,Miura, Masahiro,Nomura, Masakatsu
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p. 6941 - 6946
(2007/10/03)
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- Surface-Mediated Reactions. 4. Hydrohalogenation of Alkynes
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The use of appropriately prepared silica gel and alumina has been found to mediate the addition of hydrogen halides to alkynes.The technique has been rendered even more convenient by the use of various organic and inorganic acid halides that react in the presence of silica gel or alumina to generate hydrogen halides in situ.Treatment in this fashion of 1-propynylbenzene (1), which underwent no reaction in CH2Cl2 solution saturated with HCl, readily afforded the syn addition product, alkenyl chloride (E)-4a.On extended treatment (E)-4a underwent subsequent iaomerization to the thermodynamically more stable Z isomer.Thus either isomer of 4a could be obtained in good yield depending on the reaction conditions.In a similar way bromides (E)- and (Z)-4b were obtained without competing formation of the radical products (E)- and (Z)-5, which occurred in solution.In contrast with solution-phase hydroiodination of alkyne 1, which slowly afforded iodide (E)-4c, surface-mediated addition readily afforded (E)-4c, followed by isomerization to the Z isomer.E ->/- Z equilibration of the alkenyl halides 4 was shown to involve, at last in part, addition-elimination via the gem-dihalides 13.Analogous behavior was exhibited by the phenylalkynes 2 and 3 on surface-mediated hydrohalogenation.Surface-mediated addition of HBr and HI to the internal alkylalkyne 14 afforded principally the anti addition products (Z)-15b,c.Treatment of the terminal alkynes 17 and 22 with (COBr)2 over alumina gave the dibromides 20 and 24/25, respectively, whereas use of acetyl bromide as the HBr precursor afforded the alkenyl bromides 18b and 23.
- Kropp, Paul J.,Crawford, Scott D.
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p. 3102 - 3112
(2007/10/02)
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- Debromination of meso- and (+/-)-1,2-Dibromo-1,2-diphenylethane by 9-Substituted Fluorenide Ions. Correlation between Stereochemical Results and Redox Potentials
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The ratio between (E)- and (Z)-1,2-diphenylethene, (E:Z), has been obtained for the reaction of ten 9-substituted fluorenide ions with 1,2-dibromo-1,2-diphenylethane in dimethyl sulfoxide.It has been demonstrated that both the redox potential of the fluorenide anion and the bulkiness of the 9-substituent are important parameters in the interpretation of the observed variation (0.08-1.64) of the E:Z ratio.
- Lund, Torben,Bjoern, Christian,Hansen, Helle S.,Jensen, Anne K.,Thorsen, Teddy K.
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p. 877 - 884
(2007/10/02)
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- Conversion of Stilbene to trisubstituted Olefins
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Determination of stereochemistry of bromination-dehydrobromination of both cis and trans-stilbene has been achieved.Coupling of the resulting vinyl bromides with alkyl or aryl groups have been done.The coupling products could serve as intermediates for the synthesis of biologically active tetrasubstituted olefins.
- Al-Hassan, Mohammed I.
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p. 463 - 472
(2007/10/02)
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- Electrochemical Methods for Determination of Rate Constants. III. Homogeneous Electron Transfer Followed by Elemination Induced by the Substrate Anion
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The indirect electrochemical reduction of 1-bromo-1,2-diphenylethene yields a mixture of 50percent stilbene and 50percent diphenylacetylene, the latter being formed by an elimination induced by the electrogenerated vinyl anion.The kinetic equations for single electron transfer (SET) followed by an elimination reaction between the reduced form of the substrate and the substrate have been solved by digital simulation for linear sweep voltammetry (LSV) and cyclic voltammetry (CV).The rate constant for the SET reaction has been determined for the indirect reduction of E and Z 1-bromo-1,2-diphenylethene by a number of mediators.The rate constant of the elimination step has also been estimated.
- Gatti, Norberto,Pedersen, Steen Uttrup,Lund, Henning
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- NAD(P)+-NAD(P)H Model. 54. Free Radical Mechanism for the Reductive Debromination of vic-Dibromides to Alkenes
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vic-Dibromides undergo reductive debromination with a model of NAD(P)H, N-benzyl-1,4-dihydronicotinamide, to afford the corresponding alkenes quantitatively.Stereochemistry of the reduction suggests that the reaction involves a free radical intermediacy.
- Yasui, Shinro,Nakamura, Kaoru,Ohno, Atsuyoshi
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p. 1847 - 1848
(2007/10/02)
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- Hydroxide Ion Initiated Reactions under Phase Transfer Catalysis Conditions. 9. Dehydrohalogenation of (Haloethyl)benzenes by Quaternary Ammonium Salts
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Elimination of HCl and HBr from (1- and (2-haloethyl)benzenes in the presence of aqueous sodium hydroxide and quaternary ammonium salts which cannot extract hydroxide anion to the organic phase is shown to proceed via a reverse phase transfer process.The catalyst QX promotes the elimination and forms QX-HX adduct which is neutralized at the interphase by the hydroxide base.First-order kinetics is observed under conditions in which the catalyst is stable.Complicated kinetics is obtained when decomposition of the catalyst takes place simultaneously with the reaction.
- Halpern, Marc,Zahalka, Hayder A.,Sasson, Yoel,Rabinovitz, Mordecai
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p. 5088 - 5092
(2007/10/02)
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- Elimination Reactions of Stilbene Dibromides. Dehydrobromination by Acetate, Cyanide or Chloride Ions in Dimethylformamide
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Rates of dehydrobromination of a series of 4-nitro- and methoxystilbene dibromides by means of acetate, cyanide or chloride ions in dimethylformamide have been measured.A product analysis was performed which indicated a strong preference for anti elimination.Probable transition state structures utilized by each of the three nucleophiles are described.Attack by the base may be at either β-hydrogen (E 2H) or Cα(E2C).The slowest reaction in with chloride ion, which also gives the highest anti/syn elimination product ratio.
- Avraamides, James,Parker, Alan J.
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p. 1705 - 1717
(2007/10/02)
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