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Anion-Initiated Trifluoromethylation by TMSCF3: Deconvolution of the Siliconate–Carbanion Dichotomy by Stopped-Flow NMR/IR
The mechanism of CF3 transfer from R3SiCF3 (R = Me, Et, iPr) to ketones and aldehydes, initiated by M+X– (
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| Published in: | Journal of the American Chemical Society 2018-09, Vol.140 (35), p.11112-11124 |
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| Main Authors: | , , , , , , , |
| Format: | Article |
| Language: | English |
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| container_end_page | 11124 |
| container_issue | 35 |
| container_start_page | 11112 |
| container_title | Journal of the American Chemical Society |
| container_volume | 140 |
| creator | Johnston, Craig P West, Thomas H Dooley, Ruth E Reid, Marc Jones, Ariana B King, Edward J Leach, Andrew G Lloyd-Jones, Guy C |
| description | The mechanism of CF3 transfer from R3SiCF3 (R = Me, Et, iPr) to ketones and aldehydes, initiated by M+X– ( |
| doi_str_mv | 10.1021/jacs.8b06777 |
| format | article |
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The kinetics, reaction orders, and selectivity vary substantially with reagent (R3SiCF3) and initiator (M+X–). Traces of exogenous inhibitors present in the R3SiCF3 reagents, which vary substantially in proportion and identity between batches and suppliers, also affect the kinetics. Some reactions are complete in milliseconds, others take hours, and others stall before completion. Despite these differences, a general mechanism has been elucidated in which the product alkoxide and CF3 – anion act as chain carriers in an anionic chain reaction. Silyl enol ether generation competes with 1,2-addition and involves protonation of CF3 – by the α-C–H of the ketone and the OH of the enol. The overarching mechanism for trifluoromethylation by R3SiCF3, in which pentacoordinate siliconate intermediates are unable to directly transfer CF3 – as a nucleophile or base, rationalizes why the turnover rate (per M+X– initiator) depends on the initial concentration (but not identity) of X–, the identity (but not concentration) of M+, the identity of the R3SiCF3 reagent, and the carbonyl/R3SiCF3 ratio. It also rationalizes which R3SiCF3 reagent effects the most rapid trifluoromethylation, for a specific M+X– initiator.</description><identifier>ISSN: 0002-7863</identifier><identifier>ISSN: 1520-5126</identifier><identifier>EISSN: 1520-5126</identifier><identifier>DOI: 10.1021/jacs.8b06777</identifier><identifier>PMID: 30080973</identifier><language>eng</language><publisher>American Chemical Society</publisher><ispartof>Journal of the American Chemical Society, 2018-09, Vol.140 (35), p.11112-11124</ispartof><rights>Copyright © 2018 American Chemical Society 2018 American Chemical Society</rights><lds50>peer_reviewed</lds50><oa>free_for_read</oa><woscitedreferencessubscribed>false</woscitedreferencessubscribed><orcidid>0000-0003-2128-6864 ; 0000-0003-1325-8273</orcidid></display><links><openurl>$$Topenurl_article</openurl><openurlfulltext>$$Topenurlfull_article</openurlfulltext><thumbnail>$$Tsyndetics_thumb_exl</thumbnail><link.rule.ids>230,314,780,784,885,27924,27925</link.rule.ids></links><search><creatorcontrib>Johnston, Craig P</creatorcontrib><creatorcontrib>West, Thomas H</creatorcontrib><creatorcontrib>Dooley, Ruth E</creatorcontrib><creatorcontrib>Reid, Marc</creatorcontrib><creatorcontrib>Jones, Ariana B</creatorcontrib><creatorcontrib>King, Edward J</creatorcontrib><creatorcontrib>Leach, Andrew G</creatorcontrib><creatorcontrib>Lloyd-Jones, Guy C</creatorcontrib><title>Anion-Initiated Trifluoromethylation by TMSCF3: Deconvolution of the Siliconate–Carbanion Dichotomy by Stopped-Flow NMR/IR</title><title>Journal of the American Chemical Society</title><addtitle>J. Am. Chem. Soc</addtitle><description>The mechanism of CF3 transfer from R3SiCF3 (R = Me, Et, iPr) to ketones and aldehydes, initiated by M+X– (<0.004 to 10 mol %), has been investigated by analysis of kinetics (variable-ratio stopped-flow NMR and IR), 13C/2H KIEs, LFER, addition of ligands (18-c-6, crypt-222), and density functional theory calculations. The kinetics, reaction orders, and selectivity vary substantially with reagent (R3SiCF3) and initiator (M+X–). Traces of exogenous inhibitors present in the R3SiCF3 reagents, which vary substantially in proportion and identity between batches and suppliers, also affect the kinetics. Some reactions are complete in milliseconds, others take hours, and others stall before completion. Despite these differences, a general mechanism has been elucidated in which the product alkoxide and CF3 – anion act as chain carriers in an anionic chain reaction. Silyl enol ether generation competes with 1,2-addition and involves protonation of CF3 – by the α-C–H of the ketone and the OH of the enol. The overarching mechanism for trifluoromethylation by R3SiCF3, in which pentacoordinate siliconate intermediates are unable to directly transfer CF3 – as a nucleophile or base, rationalizes why the turnover rate (per M+X– initiator) depends on the initial concentration (but not identity) of X–, the identity (but not concentration) of M+, the identity of the R3SiCF3 reagent, and the carbonyl/R3SiCF3 ratio. It also rationalizes which R3SiCF3 reagent effects the most rapid trifluoromethylation, for a specific M+X– initiator.</description><issn>0002-7863</issn><issn>1520-5126</issn><issn>1520-5126</issn><fulltext>true</fulltext><rsrctype>article</rsrctype><creationdate>2018</creationdate><recordtype>article</recordtype><recordid>eNpVkctq3DAUhkVpSSaXXR_Ay2ycHF0syV0EwiSTDCQtZCZrIclyR4NsTW05ZaCLvEPeME8STzpQujqc8_98cPgQ-orhHAPBF2tt-3NpgAshPqEJLgjkBSb8M5oAAMmF5PQQHfX9elwZkfgAHVIACaWgE_TnqvWxzeetT14nV2XLztdhiF1sXFptg05jnJlttnxYTGf0W3btbGyfYxg-glhnaeWyhQ9-PI-At5fXqe6M3lGza29XMcVmuwMsUtxsXJXPQvydfX94vJg_nqAvtQ69O93PY_Q0u1lO7_L7H7fz6dV9rqmElGNdWsJLKcAJy7kthLaUVVDLylBBHcHGSEZsgRmTpARmai4oLbAwRQlVQY_R5V_uZjCNq6xrU6eD2nS-0d1WRe3V_0nrV-pnfFYcU0ooHwFne0AXfw2uT6rxvXUh6NbFoVcEJCuJYKz4Vx21qHUcunb8TGFQO1lqJ0vtZdF3clqImw</recordid><startdate>20180905</startdate><enddate>20180905</enddate><creator>Johnston, Craig P</creator><creator>West, Thomas H</creator><creator>Dooley, Ruth E</creator><creator>Reid, Marc</creator><creator>Jones, Ariana B</creator><creator>King, Edward J</creator><creator>Leach, Andrew G</creator><creator>Lloyd-Jones, Guy C</creator><general>American Chemical Society</general><scope>7X8</scope><scope>5PM</scope><orcidid>https://orcid.org/0000-0003-2128-6864</orcidid><orcidid>https://orcid.org/0000-0003-1325-8273</orcidid></search><sort><creationdate>20180905</creationdate><title>Anion-Initiated Trifluoromethylation by TMSCF3: Deconvolution of the Siliconate–Carbanion Dichotomy by Stopped-Flow NMR/IR</title><author>Johnston, Craig P ; West, Thomas H ; Dooley, Ruth E ; Reid, Marc ; Jones, Ariana B ; King, Edward J ; Leach, Andrew G ; Lloyd-Jones, Guy C</author></sort><facets><frbrtype>5</frbrtype><frbrgroupid>cdi_FETCH-LOGICAL-a380t-1a9c269870e7c66c57ac34d0f8db373e21bb842c514482904bf6733517b590d53</frbrgroupid><rsrctype>articles</rsrctype><prefilter>articles</prefilter><language>eng</language><creationdate>2018</creationdate><toplevel>peer_reviewed</toplevel><toplevel>online_resources</toplevel><creatorcontrib>Johnston, Craig P</creatorcontrib><creatorcontrib>West, Thomas H</creatorcontrib><creatorcontrib>Dooley, Ruth E</creatorcontrib><creatorcontrib>Reid, Marc</creatorcontrib><creatorcontrib>Jones, Ariana B</creatorcontrib><creatorcontrib>King, Edward J</creatorcontrib><creatorcontrib>Leach, Andrew G</creatorcontrib><creatorcontrib>Lloyd-Jones, Guy C</creatorcontrib><collection>MEDLINE - Academic</collection><collection>PubMed Central (Full Participant titles)</collection><jtitle>Journal of the American Chemical Society</jtitle></facets><delivery><delcategory>Remote Search Resource</delcategory><fulltext>fulltext</fulltext></delivery><addata><au>Johnston, Craig P</au><au>West, Thomas H</au><au>Dooley, Ruth E</au><au>Reid, Marc</au><au>Jones, Ariana B</au><au>King, Edward J</au><au>Leach, Andrew G</au><au>Lloyd-Jones, Guy C</au><format>journal</format><genre>article</genre><ristype>JOUR</ristype><atitle>Anion-Initiated Trifluoromethylation by TMSCF3: Deconvolution of the Siliconate–Carbanion Dichotomy by Stopped-Flow NMR/IR</atitle><jtitle>Journal of the American Chemical Society</jtitle><addtitle>J. Am. Chem. Soc</addtitle><date>2018-09-05</date><risdate>2018</risdate><volume>140</volume><issue>35</issue><spage>11112</spage><epage>11124</epage><pages>11112-11124</pages><issn>0002-7863</issn><issn>1520-5126</issn><eissn>1520-5126</eissn><abstract>The mechanism of CF3 transfer from R3SiCF3 (R = Me, Et, iPr) to ketones and aldehydes, initiated by M+X– (<0.004 to 10 mol %), has been investigated by analysis of kinetics (variable-ratio stopped-flow NMR and IR), 13C/2H KIEs, LFER, addition of ligands (18-c-6, crypt-222), and density functional theory calculations. The kinetics, reaction orders, and selectivity vary substantially with reagent (R3SiCF3) and initiator (M+X–). Traces of exogenous inhibitors present in the R3SiCF3 reagents, which vary substantially in proportion and identity between batches and suppliers, also affect the kinetics. Some reactions are complete in milliseconds, others take hours, and others stall before completion. Despite these differences, a general mechanism has been elucidated in which the product alkoxide and CF3 – anion act as chain carriers in an anionic chain reaction. Silyl enol ether generation competes with 1,2-addition and involves protonation of CF3 – by the α-C–H of the ketone and the OH of the enol. The overarching mechanism for trifluoromethylation by R3SiCF3, in which pentacoordinate siliconate intermediates are unable to directly transfer CF3 – as a nucleophile or base, rationalizes why the turnover rate (per M+X– initiator) depends on the initial concentration (but not identity) of X–, the identity (but not concentration) of M+, the identity of the R3SiCF3 reagent, and the carbonyl/R3SiCF3 ratio. It also rationalizes which R3SiCF3 reagent effects the most rapid trifluoromethylation, for a specific M+X– initiator.</abstract><pub>American Chemical Society</pub><pmid>30080973</pmid><doi>10.1021/jacs.8b06777</doi><tpages>13</tpages><orcidid>https://orcid.org/0000-0003-2128-6864</orcidid><orcidid>https://orcid.org/0000-0003-1325-8273</orcidid><oa>free_for_read</oa></addata></record> |
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| source | American Chemical Society:Jisc Collections:American Chemical Society Read & Publish Agreement 2022-2024 (Reading list) |
| title | Anion-Initiated Trifluoromethylation by TMSCF3: Deconvolution of the Siliconate–Carbanion Dichotomy by Stopped-Flow NMR/IR |
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