Počet záznamů: 1
Evidence for an Intermediate in the Methylation of CB11H12- with Methyl Triflate: Comparison of Electrophilic Substitution in Cage Boranes and in Arenes
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SYSNO ASEP 0397510 Druh ASEP J - Článek v odborném periodiku Zařazení RIV J - Článek v odborném periodiku Poddruh J Článek ve WOS Název Evidence for an Intermediate in the Methylation of CB11H12- with Methyl Triflate: Comparison of Electrophilic Substitution in Cage Boranes and in Arenes Tvůrce(i) Kaleta, Jiří (UOCHB-X) RID, ORCID
Akdag, Akin (UOCHB-X)
Crespo, R. (ES)
Piqueras, M. C. (ES)
Michl, Josef (UOCHB-X) RID, ORCIDCelkový počet autorů 5 Zdroj.dok. ChemPlusChem. - : Wiley - ISSN 2192-6506
Roč. 78, č. 9 (2013), s. 1174-1183Poč.str. 10 s. Jazyk dok. eng - angličtina Země vyd. DE - Německo Klíč. slova alkylation ; boranes ; carboranes ; electrophilic substitution ; hydrogen scrambling Vědní obor RIV CC - Organická chemie Institucionální podpora UOCHB-X - RVO:61388963 UT WOS 000324043400037 EID SCOPUS 84883886859 DOI 10.1002/cplu.201300219 Anotace The trideuteriomethylation of BH vertices in CB11H12- and its derivatives with CD3OTf (OTf=triflate, trifluoromethanesulfonate) yields a mixture of BCD3 and BCHD2 substitution products, thus demonstrating the intermediacy of a species with a long enough lifetime for hydrogen scrambling between the boron vertex and the methyl substituent. No such scrambling is observed if CD3OTf is used to methylate toluene. According to density functional theory calculations, the intermediate in BH vertex methylation is a three-center bonded sigma adduct of a methyl cation to the BH bond and the proton scrambling occurs via a transition structure containing a distorted square-pyramidal methane attached axially to a naked boron vertex. The subsequent proton or deuteron loss is presently not understood in detail. A general comparison of electrophilic substitution on closo-boranes and arenes is provided and similarities as well as differences are discussed. A recalculation of the optimized geometry of the CB11Me12. radical produced a second Jahn-Teller distorted minimum and resulted in a somewhat improved agreement between calculated and measured proton hyperfine coupling constants. Pracoviště Ústav organické chemie a biochemie Kontakt asep@uochb.cas.cz ; Kateřina Šperková, Tel.: 232 002 584 ; Viktorie Chládková, Tel.: 232 002 434 Rok sběru 2014
Počet záznamů: 1