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Carbometalation
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<h2 id="carboboration">Carboboration</h2> <p><a href="/facts/Carboboration/J67Dxsgk">Carboboration</a> is one of the most versatile carbometallation reactions. See <i><a href="/facts/Carboboration/J67Dxsgk">Carboboration</a></i>. </p> <h2 id="carboalumination">Carboalumination</h2> <p>The carboalumination reaction is most commonly catalyzed by <a href="/facts/Zirconocene_dichloride/q7ggJln2">zirconocene dichloride</a> (or related catalyst). Some carboaluminations are performed with <a href="/facts/Titanocene/4sGXUdHd">titanocene</a> complexes.<a class="footnote-ref" id="fnref:2" href="#fn:2"><sup>2</sup></a> This reaction is sometimes referred to as the <a href="/facts/ZACA_reaction/ayPvQgkD">Zr- catalyzed asymmetric carboalumination of alkenes</a> (ZACA) or the Zr-catalyzed methylalumination of alkynes (ZMA).<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a> </p> <p>The most common trialkyl aluminium reagents for this transformation are <a href="/facts/Trimethylaluminium/QxlKB90v">trimethylaluminium</a>, <a href="/facts/Triethylaluminium/CTLVqBbP">triethylaluminium</a>, and sometimes <a href="/facts/Triisobutylaluminium/oRBsz2e7">triisobutylaluminium</a>. When using trialkylaluminium reagents that have <a href="/facts/Beta-Hydride_elimination/x0BBXj9K">beta-hydrides</a>, eliminations and hydroaluminium reactions become competing processes. The general mechanism of the ZMA reaction can be described as first the formation of the active catalytic species from the pre-catalyst zirconocene dichloride through its reaction with trimethyl aluminium. First <a href="/facts/Transmetalation/Mm0hQzp3">transmetalation</a> of a methyl from the aluminium to the zirconium occurs. Next, chloride abstraction by aluminium creates a <a href="/facts/Ion/3bePpDna">cationic</a> zirconium species that is closely associated with an anionic aluminium complex. This zirconium cation can coordinate an alkene or alkyne where <a href="/facts/Migratory_insertion/k09XRSx9">migratory insertion</a> of a methyl then takes place. The resultant vinyl or alkyl zirconium species can undergo a reversible, but stereoretentive <a href="/facts/Transmetalation/Mm0hQzp3">transmetalation</a> with an <a href="/facts/Organoaluminium_chemistry/GM0K5eKE">organoaluminium</a> to provide the carboalumination product and regeneration of the zirconocene dichloride catalyst. This process generally provides the syn-addition product; however, conditions exist to provide the anti-addition product though a modified mechanism. </p><p><a href="/facts/Trimethylsilyl/RJuCYXfk">Trimethylsilyl</a> (TMS) protected alkynes, trimethyl <a href="/facts/Germanium/wtoALHGs">germanium</a> alkynes, and <a href="/facts/Alkyne/VHI4N5Wo">terminal alkynes</a> can produce anti-carboalumination products at room temperature or elevated temperatures if a coordinating group is nearby on the <a href="/facts/Substrate_(chemistry)/6MnaV19h">substrate</a>.<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a> In these reactions, first syn-carboalumination takes place under the previously outlined mechanism. Then, another equivalent of aluminium that is coordinated to the directing group can displace the vinyl aluminium, inverting the geometry at the carbon where displacement takes place. </p> <p>This forms a <a href="/facts/Chemical_stability/j0YIgc6F">thermodynamically</a> favorable <a href="/facts/Metallacycle/qj2m90JC">metallacycle</a> to prevent subsequent inversions. Formally, this process provides anti-carboalumination products that can be quenched with electrophiles. A limitation of this methodology is that the directing group must be sufficiently close to the carbon-carbon π-bond to form a thermodynamically favorable ring or else mixtures of <a href="/facts/Cis%25E2%2580%2593trans_isomerism/vqlchJly">geometric isomers</a> will form. </p> <p>The carboalumination of alkenes to form substituted alkanes can be rendered enantioselective if <a href="/facts/Prochirality/31Cpe8tC">prochiral</a> alkenes are used. In these reactions, a <a href="/facts/Chirality_(chemistry)/p5a9pftB">chiral</a> <a href="/facts/Transition_metal_indenyl_complex/UovkVaQK">indenyl</a> zirconium <a href="/facts/Catalysis/LPBS7TQC">catalyst</a> is used to induce enantioselectivity. In these reactions, high enantioselectivities were obtained for several trialkyl aluminium reagents, however, the yield decreases dramatically with each additional carbon of the <a href="/facts/Alkyl/vmEk8X4v">alkyl</a> chain on the trialkyl aluminium reagent.<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a> </p> <h2 id="carbolithiation">Carbolithiation</h2> <p>Carbolithiation is the addition of an <a href="/facts/Organolithium_reagent/xgYnjhP3">organolithium reagent</a> across a carbon-carbon pi-bond. The organolithium reagents used in this transformation can be commercial (such as <a href="/facts/N-Butyllithium/v4Rz4Dc1">n-butyllithium</a>) or can be generated through <a href="/facts/Deprotonation/SmUSh369">deprotonation</a> or <a href="/facts/Lithium-halogen_exchange/g0zvPIU0">lithium-halogen exchange</a>.<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a><a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a> Both inter- and <a href="/facts/Intramolecular_reaction/a369zhCw">intramolecular</a> examples of carbolithiation exist and can be used in synthesis to generate complexity. Organolithiums are highly reactive chemicals and often the resulting organolithium reagent generated from the carbolithiation can continue to react with electrophiles or remaining starting material (resulting in <a href="/facts/Polymerization/1hmBz7Ur">polymerization</a>).<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a> This reaction has been rendered enantioselective<a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a><a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a> through the use of <a href="/facts/Sparteine/MHJN5Wef">sparteine</a>, which can <a href="/facts/Chelation/4G79sXBB">chelate</a> the lithium ion and induce <a href="/facts/Chirality_(chemistry)/p5a9pftB">chirality</a>.<a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a> Today, this is not a common strategy due to a shortage of natural sparteine. However, recent advances in the synthesis of sparteine surrogates and their effective application in carbolithiation have reactivated interest in this strategy.<a class="footnote-ref" id="fnref:12" href="#fn:12"><sup>12</sup></a> </p><p>Another demonstration of this reaction type is an alternative route to <a href="/facts/Tamoxifen/oHU8n7ch">tamoxifen</a> starting from <a href="/facts/Diphenylacetylene/d6APXh1A">diphenylacetylene</a> and <a href="/facts/Organolithium/xgYnjhP3">ethyllithium</a>:<a class="footnote-ref" id="fnref:13" href="#fn:13"><sup>13</sup></a> The capturing electrophile here is <a href="/facts/Borate/5XwkBTv1">triisopropyl borate</a> forming the <a href="/facts/Boronic_acid/BtN4s5B4">boronic acid</a> R–B(OH)2. The second step completing tamoxifen is a <a href="/facts/Suzuki_reaction/aRISucCH">Suzuki reaction</a>. </p> <p>As a consequence of the high reactivity of organolithiums as strong <a href="/facts/Base_(chemistry)/M9wA7qeM">bases</a> and strong <a href="/facts/Nucleophile/xYccoaJQ">nucleophiles</a>, the substrate scope of the carbolithiation is generally limited to chemicals that do not contain <a href="/facts/Acid/FySU18n1">acidic</a> or <a href="/facts/Electrophile/1AHFg1zm">electrophilic</a> <a href="/facts/Functional_group/GXkSPsjM">functional groups</a>. </p> <h2 id="carbomagnesiation-and-carbozincation">Carbomagnesiation and carbozincation</h2> <p>Due to the decreased <a href="/facts/Nucleophile/xYccoaJQ">nucleophilicity</a> of <a href="/facts/Grignard_reagent/0vkLtPo1">Grignard reagents</a> (organomagnesium) and <a href="/facts/Organozinc_compound/xpcLJCT4">organozinc</a> reagents, non-catalyzed carbomagnesiation and carbozincation reactions are typically only observed on activated or <a href="/facts/Strain_(chemistry)/xhAQQMH8">strained</a> alkenes and alkynes.<a class="footnote-ref" id="fnref:14" href="#fn:14"><sup>14</sup></a> For example, <a href="/facts/Polar_effect/GDzV1DXL">electron withdrawing</a> groups like <a href="/facts/Esters/FoUAIIw4">esters</a>, <a href="/facts/Nitrile/Gz7RCnC6">nitriles</a> or <a href="/facts/Sulfone/LJLP1RcT">sulfones</a> must be in conjugation with the carbon-carbon π-system (see <a href="/facts/Michael_reaction/yqLD22AQ">Michael reaction</a>) or a directing group like an <a href="/facts/Alcohol_(chemistry)/Y0SCTDkh">alcohol</a> or <a href="/facts/Amine/JvfYJfP6">amine</a> must be nearby to direct the reaction. These reactions can be catalyzed by a variety of transition metals such as iron,<a class="footnote-ref" id="fnref:15" href="#fn:15"><sup>15</sup></a><a class="footnote-ref" id="fnref:16" href="#fn:16"><sup>16</sup></a> copper,<a class="footnote-ref" id="fnref:17" href="#fn:17"><sup>17</sup></a> zirconium,<a class="footnote-ref" id="fnref:18" href="#fn:18"><sup>18</sup></a> nickel,<a class="footnote-ref" id="fnref:19" href="#fn:19"><sup>19</sup></a><a class="footnote-ref" id="fnref:20" href="#fn:20"><sup>20</sup></a> cobalt<a class="footnote-ref" id="fnref:21" href="#fn:21"><sup>21</sup></a> and others. </p><p>Illustrative is the Fe-catalyzed reaction of methylphenylacetylene with <a href="/facts/Phenylmagnesium_bromide/lx5S0Jl6">phenylmagnesium bromide</a>, which generates a vinyl magnesium intermediate. Hydrolysis affords the diphenylalkene:<a class="footnote-ref" id="fnref:22" href="#fn:22"><sup>22</sup></a><a class="footnote-ref" id="fnref:23" href="#fn:23"><sup>23</sup></a> </p> <h2 id="carbopalladation">Carbopalladation</h2> <p>Carbopalladations can be a description of the elementary step of a reaction catalyzed by a palladium catalyst (<a href="/facts/Heck_reaction/I9E7pLUC">Mizoroki-Heck reaction</a>)<a class="footnote-ref" id="fnref:24" href="#fn:24"><sup>24</sup></a> and can also refer to a carbometalation reaction with a palladium catalyst (alkene difunctionalization,<a class="footnote-ref" id="fnref:25" href="#fn:25"><sup>25</sup></a> <a href="/facts/Hydrofunctionalization/2alcBH3G">hydrofunctionalization</a>,<a class="footnote-ref" id="fnref:26" href="#fn:26"><sup>26</sup></a><a class="footnote-ref" id="fnref:27" href="#fn:27"><sup>27</sup></a> or reductive Heck<a class="footnote-ref" id="fnref:28" href="#fn:28"><sup>28</sup></a>) </p> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>Negishi, Ei-ichi; Tan, Ze (2005), "Diastereoselective, Enantioselective, and Regioselective Carboalumination Reactions Catalyzed by Zirconocene Derivatives", Metallocenes in Regio- and Stereoselective Synthesis: -/-, Topics in Organometallic Chemistry, Springer Berlin Heidelberg, pp. 139–176, doi:10.1007/b96003, ISBN 9783540314523 <a href="9783540314523" target="_blank">9783540314523</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>Negishi, Ei-ichi; Tan, Ze (2005), "Diastereoselective, Enantioselective, and Regioselective Carboalumination Reactions Catalyzed by Zirconocene Derivatives", Metallocenes in Regio- and Stereoselective Synthesis: -/-, Topics in Organometallic Chemistry, Springer Berlin Heidelberg, pp. 139–176, doi:10.1007/b96003, ISBN 9783540314523 <a href="9783540314523" target="_blank">9783540314523</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>Xu, Shiqing; Negishi, Ei-ichi (2016-10-18). "Zirconium-Catalyzed Asymmetric Carboalumination of Unactivated Terminal Alkenes". Accounts of Chemical Research. 49 (10): 2158–2168. doi:10.1021/acs.accounts.6b00338. ISSN 0001-4842. PMID 27685327. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>Ma, Shengming; Negishi, Ei-ichi (1997-02-01). "Anti-Carbometalation of Homopropargyl Alcohols and Their Higher Homologues via Non-Chelation-Controlled Syn-Carbometalation and Chelation-Controlled Isomerization". The Journal of Organic Chemistry. 62 (4): 784–785. doi:10.1021/jo9622688. ISSN 0022-3263. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>Xu, Shiqing; Negishi, Ei-ichi (2016-10-18). "Zirconium-Catalyzed Asymmetric Carboalumination of Unactivated Terminal Alkenes". Accounts of Chemical Research. 49 (10): 2158–2168. doi:10.1021/acs.accounts.6b00338. ISSN 0001-4842. PMID 27685327. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>O’Shea, Donal F.; Hogan, Anne-Marie L. (2008-08-18). "Synthetic applications of carbolithiation transformations". Chemical Communications (33): 3839–3851. doi:10.1039/B805595E. ISSN 1364-548X. PMID 18726011. <a href="https://pubs.rsc.org/en/content/articlelanding/2008/cc/b805595e" target="_blank">https://pubs.rsc.org/en/content/articlelanding/2008/cc/b805595e</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>García, Graciela V.; Nudelman, Norma Sbarbati (2009-02-11). "Tandem Reactions Involving Organolithium Reagents. A Review". Organic Preparations and Procedures International. 35 (5): 445–500. doi:10.1080/00304940309355860. S2CID 98358106. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> <li id="fn:8"><p>O’Shea, Donal F.; Hogan, Anne-Marie L. (2008-08-18). "Synthetic applications of carbolithiation transformations". Chemical Communications (33): 3839–3851. doi:10.1039/B805595E. ISSN 1364-548X. PMID 18726011. <a href="https://pubs.rsc.org/en/content/articlelanding/2008/cc/b805595e" target="_blank">https://pubs.rsc.org/en/content/articlelanding/2008/cc/b805595e</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li> <li id="fn:9"><p>Norsikian, Stephanie; Marek, Ilane; Normant, Jean-F (1997-10-27). "Enantioselective Carbolithiation of β-Alkylated Styrene". Tetrahedron Letters. 38 (43): 7523–7526. doi:10.1016/S0040-4039(97)10022-3. ISSN 0040-4039. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li> <li id="fn:10"><p>Norsikian, Stephanie; Marek, Ilan; Klein, Sophie; Poisson, Jean F.; Normant, Jean F. (1999). "Enantioselective Carbometalation of Cinnamyl Derivatives: New Access to Chiral Disubstituted Cyclopropanes— Configurational Stability of Benzylic Organozinc Halides". Chemistry – A European Journal. 5 (7): 2055–2068. doi:10.1002/(SICI)1521-3765(19990702)5:7<2055::AID-CHEM2055>3.0.CO;2-9. ISSN 1521-3765. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></p></li> <li id="fn:11"><p>O’Shea, Donal F.; Hogan, Anne-Marie L. (2008-08-18). "Synthetic applications of carbolithiation transformations". Chemical Communications (33): 3839–3851. doi:10.1039/B805595E. ISSN 1364-548X. PMID 18726011. <a href="https://pubs.rsc.org/en/content/articlelanding/2008/cc/b805595e" target="_blank">https://pubs.rsc.org/en/content/articlelanding/2008/cc/b805595e</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></p></li> <li id="fn:12"><p>Tait, Michael; Donnard, Morgan; Minassi, Alberto; Lefranc, Julien; Bechi, Beatrice; Carbone, Giorgio; O'Brien, Peter; Clayden, Jonathan (2013). "Amines Bearing Tertiary Substituents by Tandem Enantioselective Carbolithiation-Rearrangement of Vinylureas". Organic Letters. 15 (1): 34–37. doi:10.1021/ol3029324. ISSN 1523-7060. PMID 23252812. <a href="https://figshare.com/articles/journal_contribution/2443165" target="_blank">https://figshare.com/articles/journal_contribution/2443165</a> <a href="#fnref:12" class="footnote-back-ref">↩</a></p></li> <li id="fn:13"><p>McKinley, Neola F.; O'Shea, Donal F. (2006). "Carbolithiation of Diphenylacetylene as a Stereoselective Route to (Z)-Tamoxifen and Related Tetrasubstituted Olefins". J. Org. Chem. (Note). 71 (25): 9552–9555. doi:10.1021/jo061949s. PMID 17137396. <a href="/wiki/J._Org._Chem." target="_blank">/wiki/J._Org._Chem.</a> <a href="#fnref:13" class="footnote-back-ref">↩</a></p></li> <li id="fn:14"><p>Yorimitsu, Hideki; Murakami, Kei (2013-02-11). "Recent advances in transition-metal-catalyzed intermolecular carbomagnesiation and carbozincation". Beilstein Journal of Organic Chemistry. 9 (1): 278–302. doi:10.3762/bjoc.9.34. ISSN 1860-5397. PMC 3596116. PMID 23503106. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3596116" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3596116</a> <a href="#fnref:14" class="footnote-back-ref">↩</a></p></li> <li id="fn:15"><p>Yorimitsu, Hideki; Murakami, Kei (2013-02-11). "Recent advances in transition-metal-catalyzed intermolecular carbomagnesiation and carbozincation". Beilstein Journal of Organic Chemistry. 9 (1): 278–302. doi:10.3762/bjoc.9.34. ISSN 1860-5397. PMC 3596116. PMID 23503106. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3596116" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3596116</a> <a href="#fnref:15" class="footnote-back-ref">↩</a></p></li> <li id="fn:16"><p>Shirakawa, Eiji; Yamagami, Takafumi; Kimura, Takahiro; Yamaguchi, Shigeru; Hayashi, Tamio (2005). "Arylmagnesiation of Alkynes Catalyzed Cooperatively by Iron and Copper Complexes". J. Am. Chem. Soc. (Communication). 127 (49): 17164–17165. doi:10.1021/ja0542136. PMID 16332046. <a href="/wiki/J._Am._Chem._Soc." target="_blank">/wiki/J._Am._Chem._Soc.</a> <a href="#fnref:16" class="footnote-back-ref">↩</a></p></li> <li id="fn:17"><p>Yorimitsu, Hideki; Murakami, Kei (2013-02-11). "Recent advances in transition-metal-catalyzed intermolecular carbomagnesiation and carbozincation". Beilstein Journal of Organic Chemistry. 9 (1): 278–302. doi:10.3762/bjoc.9.34. ISSN 1860-5397. PMC 3596116. PMID 23503106. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3596116" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3596116</a> <a href="#fnref:17" class="footnote-back-ref">↩</a></p></li> <li id="fn:18"><p>Negishi, Eiichi; Miller, Joseph A. (1983-10-01). "Selective carbon-carbon bond formation via transition metal catalysis 37. Controlled carbometalation. 16. Novel syntheses of .alpha.,.beta.-unsaturated cyclopentenones via allylzincation of alkynes". Journal of the American Chemical Society. 105 (22): 6761–6763. doi:10.1021/ja00360a060. ISSN 0002-7863. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:18" class="footnote-back-ref">↩</a></p></li> <li id="fn:19"><p>Yorimitsu, Hideki; Murakami, Kei (2013-02-11). "Recent advances in transition-metal-catalyzed intermolecular carbomagnesiation and carbozincation". Beilstein Journal of Organic Chemistry. 9 (1): 278–302. doi:10.3762/bjoc.9.34. ISSN 1860-5397. PMC 3596116. PMID 23503106. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3596116" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3596116</a> <a href="#fnref:19" class="footnote-back-ref">↩</a></p></li> <li id="fn:20"><p>Xue, Fei; Zhao, Jin; Hor, T. S. Andy; Hayashi, Tamio (2015-03-11). "Nickel-Catalyzed Three-Component Domino Reactions of Aryl Grignard Reagents, Alkynes, and Aryl Halides Producing Tetrasubstituted Alkenes". Journal of the American Chemical Society. 137 (9): 3189–3192. doi:10.1021/ja513166w. ISSN 0002-7863. PMID 25714497. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:20" class="footnote-back-ref">↩</a></p></li> <li id="fn:21"><p>Murakami, Kei; Yorimitsu, Hideki; Oshima, Koichiro (2010). "Cobalt-Catalyzed Benzylzincation of Alkynes". Chemistry – A European Journal. 16 (26): 7688–7691. doi:10.1002/chem.201001061. ISSN 1521-3765. PMID 20521290. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:21" class="footnote-back-ref">↩</a></p></li> <li id="fn:22"><p>Shirakawa, Eiji; Yamagami, Takafumi; Kimura, Takahiro; Yamaguchi, Shigeru; Hayashi, Tamio (2005). "Arylmagnesiation of Alkynes Catalyzed Cooperatively by Iron and Copper Complexes". J. Am. Chem. Soc. (Communication). 127 (49): 17164–17165. doi:10.1021/ja0542136. 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