[{"@context":"http:\/\/schema.org\/","@type":"BlogPosting","@id":"https:\/\/wiki.edu.vn\/en\/wiki41\/%ce%b2-carbon-elimination-wikipedia\/#BlogPosting","mainEntityOfPage":"https:\/\/wiki.edu.vn\/en\/wiki41\/%ce%b2-carbon-elimination-wikipedia\/","headline":"\u03b2-Carbon elimination &#8211; Wikipedia","name":"\u03b2-Carbon elimination &#8211; Wikipedia","description":"before-content-x4 From Wikipedia, the free encyclopedia after-content-x4 \u03b2-Carbon elimination (beta-carbon elimination) is a type of reaction in organometallic chemistry wherein","datePublished":"2014-11-18","dateModified":"2014-11-18","author":{"@type":"Person","@id":"https:\/\/wiki.edu.vn\/en\/wiki41\/author\/lordneo\/#Person","name":"lordneo","url":"https:\/\/wiki.edu.vn\/en\/wiki41\/author\/lordneo\/","image":{"@type":"ImageObject","@id":"https:\/\/secure.gravatar.com\/avatar\/c9645c498c9701c88b89b8537773dd7c?s=96&d=mm&r=g","url":"https:\/\/secure.gravatar.com\/avatar\/c9645c498c9701c88b89b8537773dd7c?s=96&d=mm&r=g","height":96,"width":96}},"publisher":{"@type":"Organization","name":"Enzyklop\u00e4die","logo":{"@type":"ImageObject","@id":"https:\/\/wiki.edu.vn\/wiki4\/wp-content\/uploads\/2023\/08\/download.jpg","url":"https:\/\/wiki.edu.vn\/wiki4\/wp-content\/uploads\/2023\/08\/download.jpg","width":600,"height":60}},"image":{"@type":"ImageObject","@id":"https:\/\/upload.wikimedia.org\/wikipedia\/commons\/thumb\/1\/12\/%CE%92-carbon_elimination.png\/418px-%CE%92-carbon_elimination.png","url":"https:\/\/upload.wikimedia.org\/wikipedia\/commons\/thumb\/1\/12\/%CE%92-carbon_elimination.png\/418px-%CE%92-carbon_elimination.png","height":"65","width":"418"},"url":"https:\/\/wiki.edu.vn\/en\/wiki41\/%ce%b2-carbon-elimination-wikipedia\/","wordCount":6638,"articleBody":"     (adsbygoogle = window.adsbygoogle || []).push({});before-content-x4From Wikipedia, the free encyclopedia       (adsbygoogle = window.adsbygoogle || []).push({});after-content-x4\u03b2-Carbon elimination (beta-carbon elimination) is a type of reaction in organometallic chemistry wherein an allyl ligand bonded to a metal center is broken into the corresponding metal-bonded alkyl (aryl) ligand and an alkene.[1] It is a subgroup of elimination reactions. Though less common and less understood than \u03b2-hydride elimination, it is an important step involved in some olefin polymerization processes and transition-metal-catalyzed organic reactions.[2]       (adsbygoogle = window.adsbygoogle || []).push({});after-content-x4Table of ContentsOverview[edit]\u03b2-alkyl elimination[edit]Classification\/Driving force[edit]\u03b2-alkyl elimination with early transition metal complexes[edit]\u03b2-alkyl elimination with middle and late transition metal complexes[edit]Applications[edit]Ring-opening polymerization (ROP)[edit]Organic synthesis[edit]\u03b2-aryl elimination[edit]References[edit]Overview[edit]Like \u03b2-hydride elimination, \u03b2-carbon elimination requires the metal to have an open coordination site cis to the alkyl group for this reaction to occur. \u03b2-carbon elimination is usually less favored than hydride elimination because the metal\u2013hydride bond is stronger than the metal\u2013carbon bond for most metals in catalytic reactions. The principles governing \u03b2-alkyl elimination are not well-established experimentally. One reason for this is that breaking C\u2212C bonds in the presence of other reactive C\u2212H bonds is a rare event, and systems designed to interrogate the reaction are more difficult to devise.[2]  \u03b2-alkyl elimination[edit]\u03b2-alkyl elimination is the most common and useful type among all \u03b2-carbon elimination reactions.Classification\/Driving force[edit]\u03b2-alkyl elimination with early transition metal complexes[edit]In terms of thermodynamics, more electron-deficient metal centers increase the likelihood of \u03b2-alkyl elimination. For example, \u03b2-alkyl elimination is more favorable than \u03b2-hydride elimination when it is bonded to electron-deficient early transition metals (Hf, Ti, Zr, Nb, etc.) with d0 configuration. Computational studies show a thermodynamic preference for \u03b2-Me elimination over \u03b2-H elimination in these complexes due to additional stability for the metal\u2013alkyl species.[3] The origin of the additional bonding interaction comes from an orbital centered on the CH3 weakly \u03c0-donating to the LUMO of the d0 of the metal center which is analogous to the hyperconjugation effect (see figure on the right), thus increasing the stability of M\u2212CH3 over M\u2212H species. Their calculations predict that a more electrophilic metal ion enhances the \u2212CH3 \u03c0-donation, which consequently increases the stability of M\u2212CH3 over M\u2212H species. Conversely, a more electron-rich metal ion will favor M\u2212H formation (for example, using the more electron-donating Cp* ligand in Cp*2MX2).       (adsbygoogle = window.adsbygoogle || []).push({});after-content-x4In terms of kinetics, steric effects of ligands could play a role in increasing the energy barrier of \u03b2-H elimination relative to \u03b2-alkyl elimination, specifically when the ligand is Cp*. A model was proposed to illustrate this effect:[4] In both \u03b2-methyl elimination (A) and \u03b2-hydride elimination (B), the transferring group aligns perpendicular to the Cp*(centroid)\u2212Zr\u2212Cp*(centroid), allowing the \u03c3C\u2212C or \u03c3C\u2212H bond to overlap with the metal d-orbital. However, to achieve the prerequisite geometry for \u03b2-H elimination (B), the adjacent methyl group experiences a significant steric repulsion from the Cp* ligand, thereby elevating the barrier to hydride transfer. By contrast, transition state A for \u03b2-Me elimination experiences less steric interaction with the Cp* ligand.\u03b2-alkyl elimination with middle and late transition metal complexes[edit]In middle and late transition metal complexes, there is larger thermodynamic preference for \u03b2-H elimination over \u03b2-alkyl elimination, where the difference is usually >15 kcal\/mol.[2] Examples involved middle and late transition metal complexes are either absent of \u03b2-hydrogens or use ring strain relief and aromaticity as driving forces to favor \u03b2-alkyl elimination over \u03b2-hydride elimination.[5]Applications[edit]Ring-opening polymerization (ROP)[edit]Ring-opening polymerization that involves \u03b2-alkyl elimination can be catalyzed by Ti,[6] Zr,[7][8] Pd[9]-based catalyst, and some Lanthanide-based metallocene catalyst,[10][11] where different polymerization patterns vary when catalysts are different. Examples of copolymerization with alkene [10] or carbon monoxide[12][13] were also reported. The key step of this kind of ROP is string-driven \u03b2-alkyl elimination, which provides linear polymer with unsaturation in the polymer chain.Organic synthesis[edit]There is enormous amount of catalytic processes involving \u03b2-alkyl elimination that are synthetically useful. \u03b2-alkyl elimination in this case, however, is often considered as an alternative way of C\u2013C bond cleavage while oxidative addition is the direct way.[14] One of the examples is \u03b2-alkyl elimination of tert-alcoholates which can generate from either addition of an organometallic reagent or ligand exchange.[15][16][17] The consequent organometallic species can undergo various downstream reactivities (reductive elimination, carbonyl insertion, etc.) to generate useful building blocks.In addition to ring strain, aromaticity-driven \u03b2-Me elimination can be effectively employed to dealkylate steroid derivatives and some other cyclohexyl compounds.[18][19]  \u03b2-aryl elimination[edit]\u03b2-aryl elimination is much less common and understood than \u03b2-alkyl elimination. Examples are reported to occur from metal alkoxide and amido complexes.[20][21][22] A theoretical study showed that these reactions are driven by consequent extensive conjugation system.[23] A very recent example of catalytic \u03b2-aryl elimination which leads to enantioselective synthesis of biaryl atropisomers is driven by release of distorted ring string.[24]References[edit]^ Smits, G.; Audic, B.; Wodrich, M. D.; Corminboeuf, C.; Cramer, N. (24 August 2017). &#8220;A \u03b2-Carbon elimination strategy for convenient in situ access to cyclopentadienyl metal complexes&#8221;. Chemical Science. 8 (10): 7174\u20137179. doi:10.1039\/C7SC02986A. ISSN\u00a02041-6520. PMC\u00a05635420. PMID\u00a029081949. Wikidata\u00a0Q42705934.^ a b c O\u2019Reilly, Matthew E.; Dutta, Saikat; Veige, Adam S. (2016-07-27). &#8220;\u03b2-Alkyl Elimination: Fundamental Principles and Some Applications&#8221;. Chemical Reviews. 116 (14): 8105\u20138145. doi:10.1021\/acs.chemrev.6b00054. ISSN\u00a00009-2665. PMID\u00a027366938.^ Sini, Gjergji; Macgregor, Stuart A.; Eisenstein, Odile; Teuben, Jan H. (April 1994). &#8220;Why Is .beta.-Me Elimination Only Observed in d0 Early-Transition-Metal Complexes? An Organometallic Hyperconjugation Effect with Consequences for the Termination Step in Ziegler-Natta Catalysis&#8221;. Organometallics. 13 (4): 1049\u20131051. doi:10.1021\/om00016a001. ISSN\u00a00276-7333.^ Eshuis, Johan J. W.; Tan, Yong Y.; Meetsma, Auke; Teuben, Jan H.; Renkema, Jaap; Evens, George G. (January 1992). &#8220;Kinetic and mechanistic aspects of propene oligomerization with ionic organozirconium and -hafnium compounds: crystal structures of [Cp*2MMe(THT)]+[BPh4]- (M = zirconium, hafnium)&#8221; (PDF). Organometallics. 11 (1): 362\u2013369. doi:10.1021\/om00037a061. ISSN\u00a00276-7333.^ Miura, Masahiro; Satoh, Tetsuya (2005-06-20),  Tsuji, Jiro (ed.), &#8220;Catalytic Processes Involving \u03b2-Carbon Elimination&#8221;, Palladium in Organic Synthesis, Springer Berlin Heidelberg, vol.\u00a014, pp.\u00a01\u201320, doi:10.1007\/b104133, ISBN\u00a09783540239826^ Rossi, R.; Diversi, P.; Porri, L. (May 1972). &#8220;On the Ring-Opening Polymerization of Methylenecyclobutane&#8221;. Macromolecules. 5 (3): 247\u2013249. Bibcode:1972MaMol&#8230;5..247R. doi:10.1021\/ma60027a004. ISSN\u00a00024-9297.^ Beswick, Colin L.; Marks, Tobin J. (October 2000). &#8220;Metal-Alkyl Group Effects on the Thermodynamic Stability and Stereochemical Mobility of B(C 6 F 5 ) 3 -Derived Zr and Hf Metallocenium Ion-Pairs&#8221;. Journal of the American Chemical Society. 122 (42): 10358\u201310370. doi:10.1021\/ja000810a. ISSN\u00a00002-7863.^ Jia, Li; Yang, Xinmin; Seyam, Affif M.; Albert, Israel D. L.; Fu, Peng-Fei; Yang, Shengtian; Marks, Tobin J. (January 1996). &#8220;Ring-Opening Ziegler Polymerization of Methylenecycloalkanes Catalyzed by Highly Electrophilic d 0 \/f n Metallocenes. Reactivity, Scope, Reaction Mechanism, and Routes to Functionalized Polyolefins&#8221;. Journal of the American Chemical Society. 118 (34): 7900\u20137913. doi:10.1021\/ja960811w. ISSN\u00a00002-7863.^ Takeuchi, Daisuke; Kim, Sunwook; Osakada, Kohtaro (2001-07-16). &#8220;Ring-Opening Polymerization of 1-Methylene-2-phenylcyclopropane Catalyzed by a Pd Complex To Afford Regioregulated Polymers&#8221;. Angewandte Chemie International Edition. 40 (14): 2685\u20132688. doi:10.1002\/1521-3773(20010716)40:143.0.CO;2-9. ISSN\u00a01433-7851.^ a b Jensen, Tryg R.; O&#8217;Donnel, James J.; Marks, Tobin J. (February 2004). &#8220;d 0 \/f n -Mediated Ring-Opening Ziegler Polymerization (ROZP) and Copolymerization with Mono- and Disubstituted Methylenecyclopropanes. Diverse Mechanisms and a New Chain-Capping Termination Process&#8221;. Organometallics. 23 (4): 740\u2013754. doi:10.1021\/om030407n. ISSN\u00a00276-7333.^ Yang, Xinmin; Seyam, A. M.; Fu, Peng-Fei; Mark, Tobin J. (August 1994). &#8220;exo-Methylene-Functionalized Polyethylenes via Ring-Opening Ziegler Polymerization. Product Control in Organolanthanide-Catalyzed Methylenecyclopropane Polymerization\/Copolymerization&#8221;. Macromolecules. 27 (16): 4625\u20134626. Bibcode:1994MaMol..27.4625Y. doi:10.1021\/ma00094a030. ISSN\u00a00024-9297.^ Kettunen, Mika; Abu-Surrah, Adnan S; Repo, Timo; Leskel\u00e4, Markku (November 2001). &#8220;Copolymerization of carbon monoxide with exo -methylenecycloalkane and dienes: synthesis of functionalized aliphatic polyketones: Functionalized aliphatic polyketone synthesis&#8221;. Polymer International. 50 (11): 1223\u20131227. doi:10.1002\/pi.769.^ Kim, Sunwook; Takeuchi, Daisuke; Osakada, Kohtaro (February 2002). &#8220;Pd-Catalyzed Ring-Opening Copolymerization of 2-Aryl-1-methylenecyclopropanes with CO to Afford Polyketones via Alternating Insertion of the Two Monomers and C\u2212C Bond Activation of the Three-Membered Ring&#8221;. Journal of the American Chemical Society. 124 (5): 762\u2013763. doi:10.1021\/ja017460s. ISSN\u00a00002-7863. PMID\u00a011817946.^ Dong, Guangbin, ed. (2014). C\u2013C Bond Activation. Topics in Current Chemistry. Vol.\u00a0346. Berlin, Heidelberg: Springer Berlin Heidelberg. doi:10.1007\/978-3-642-55055-3. ISBN\u00a09783642550546. S2CID\u00a060212270.^ Murakami, Masahiro; Makino, Masaomi; Ashida, Shinji; Matsuda, Takanori (September 2006). &#8220;Construction of Carbon Frameworks through \u03b2-Carbon Elimination Mediated by Transition Metals&#8221;. Bulletin of the Chemical Society of Japan. 79 (9): 1315\u20131321. doi:10.1246\/bcsj.79.1315. ISSN\u00a00009-2673.^ Seiser, Tobias; Cramer, Nicolai (2009). &#8220;Enantioselective metal-catalyzed activation of strained rings&#8221;. Organic &#038; Biomolecular Chemistry. 7 (14): 2835\u201340. doi:10.1039\/b904405a. ISSN\u00a01477-0520. PMID\u00a019582290.^ Huffman, Mark A.; Liebeskind, Lanny S. (November 1990). &#8220;Insertion of (.eta.5-indeny)cobalt(I) into cyclobutenones: the first synthesis of phenols from isolated vinylketene complexes&#8221;. Journal of the American Chemical Society. 112 (23): 8617\u20138618. doi:10.1021\/ja00179a075. ISSN\u00a00002-7863.^ Halcrow, Malcolm A.; Urbanos, Francisco; Chaudret, Bruno (March 1993). &#8220;Aromatization of the B-ring of 5,7-dienyl steroids by the electrophilic ruthenium fragment &#8220;[Cp*Ru]+&#8221;&#8220;. Organometallics. 12 (3): 955\u2013957. doi:10.1021\/om00027a054. ISSN\u00a00276-7333.^ Older, Christina M.; Stryker, Jeffrey M. (March 2000). &#8220;The Mechanism of Carbon\u2212Carbon Bond Activation in Cationic 6-Alkylcyclohexadienyl Ruthenium Hydride Complexes&#8221;. Journal of the American Chemical Society. 122 (12): 2784\u20132797. doi:10.1021\/ja992987e. ISSN\u00a00002-7863.^ Zhao, Pinjing; Incarvito, Christopher D.; Hartwig, John F. (March 2006). &#8220;Direct Observation of \u03b2-Aryl Eliminations from Rh(I) Alkoxides&#8221;. Journal of the American Chemical Society. 128 (10): 3124\u20133125. doi:10.1021\/ja058550q. ISSN\u00a00002-7863. PMID\u00a016522075.^ Zhao, Pinjing; Hartwig, John F. (2005-08-24). &#8220;\u03b2-Aryl Eliminations from Rh(I) Iminyl Complexes&#8221;. Journal of the American Chemical Society. 127 (33): 11618\u201311619. doi:10.1021\/ja054132+. ISSN\u00a00002-7863. PMID\u00a016104735.^ Terao, Yoshito; Wakui, Hiroyuki; Satoh, Tetsuya; Miura, Masahiro; Nomura, Masakatsu (October 2001). &#8220;Palladium-Catalyzed Arylative Carbon\u2212Carbon Bond Cleavage of \u03b1,\u03b1-Disubstituted Arylmethanols&#8221;. Journal of the American Chemical Society. 123 (42): 10407\u201310408. doi:10.1021\/ja016914i. ISSN\u00a00002-7863. PMID\u00a011604000.^ Xue, Liqin; Ng, Ka Chun; Lin, Zhenyang (2009). &#8220;Theoretical studies on \u03b2-aryl elimination from Rh(i) complexes&#8221;. Dalton Transactions (30): 5841\u20135850. doi:10.1039\/b902539a. ISSN\u00a01477-9226. PMID\u00a019623383.^ Deng, Ruixian; Xi, Junwei; Li, Qigang; Gu, Zhenhua (May 2019). &#8220;Enantioselective Carbon-Carbon Bond Cleavage for Biaryl Atropisomers Synthesis&#8221;. Chem. 5 (7): 1834\u20131846. doi:10.1016\/j.chempr.2019.04.008.     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