Paul, Mathias, Breugst, Martin ORCID: 0000-0003-0950-8858, Neudoerfl, Joerg-Martin, Sunoj, Raghavan B. and Berkessel, Albrecht ORCID: 0000-0003-0470-7428 (2016). Keto-Enol Thermodynamics of Breslow Intermediates. J. Am. Chem. Soc., 138 (15). S. 5044 - 5052. WASHINGTON: AMER CHEMICAL SOC. ISSN 1520-5126
Full text not available from this repository.Abstract
Breslow intermediates, first postulated in 1958) are pivotal intermediates in carbene-catalyzed umpolung. Attempts to, isolate and characterize these fleeting amino enol species first met with success in 2012 when we found that saturated bis-Dip/Mes imidazolidinylidenes readily form isolable, though reactive diamino enols with aldehydes and enals. In contrast, triazolylidenes, upon stoichiometric reaction with aldehydes, :gave exclusively the keto tautomer, and no isolable enol. Herein, we present the synthesis of the missing keto tautomers of imidazolidinylidene-derived diamino enols, and computational thermodynamic data for 15 enol ketone pairs derived, from various carbenes/aldehydes. Electron-with-drawing substituents on the aldehyde favor enol formation, the same holds for N,N'-Dipp [2,6-di(2-propyl)phenyl] and N,N'-Mes [2,4,6-trimethylphenyl] substitution on the carbene component. The latter effect rests on stabilization of the diamino enol tautomer by Dipp substitution, and could be-attributed to dispersive interaction of the 2-propyl groups with the enol moiety. For three enol-ketone pairs, equilibration of the, thermodynamically disfavored tautomer was attempted, with acids and bases but could not be effected, indicating kinetic inhibition of proton transfer.
Item Type: | Journal Article | ||||||||||||||||||||||||
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URN: | urn:nbn:de:hbz:38-278430 | ||||||||||||||||||||||||
DOI: | 10.1021/jacs.5b13236 | ||||||||||||||||||||||||
Journal or Publication Title: | J. Am. Chem. Soc. | ||||||||||||||||||||||||
Volume: | 138 | ||||||||||||||||||||||||
Number: | 15 | ||||||||||||||||||||||||
Page Range: | S. 5044 - 5052 | ||||||||||||||||||||||||
Date: | 2016 | ||||||||||||||||||||||||
Publisher: | AMER CHEMICAL SOC | ||||||||||||||||||||||||
Place of Publication: | WASHINGTON | ||||||||||||||||||||||||
ISSN: | 1520-5126 | ||||||||||||||||||||||||
Language: | English | ||||||||||||||||||||||||
Faculty: | Faculty of Mathematics and Natural Sciences | ||||||||||||||||||||||||
Divisions: | Faculty of Mathematics and Natural Sciences > Department of Chemistry > Institute of Organic Chemistry | ||||||||||||||||||||||||
Subjects: | no entry | ||||||||||||||||||||||||
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Refereed: | Yes | ||||||||||||||||||||||||
URI: | http://kups.ub.uni-koeln.de/id/eprint/27843 |
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