Issue 23, 2021

Wanzlick's equilibrium in tri- and tetraaminoolefins

Abstract

The dissociation mechanism of electron-rich olefins into their parent carbenes has been a controversial topic since Wanzlick's pioneering work. Herein, we present a combined synthetic and computational study on the formation (dissociation, respectively) of hetero- and homo-carbene dimers derived from benzimidazolin-2-ylidenes (benzNHCs), imidazolidin-2-ylidenes (saNHC), and cyclic (alkyl) (amino) carbenes (CAACs) through sublimation (in vacuo) as well as in condensed phase. We quantify the effect of proton catalysis and report that even triaminoolefins dissociate to their free carbenes, yet only under proton catalysis. Accordingly, we report how the judicious choice of the base (KOtBu vs. KHMDS) and solvent (hexane/benzene vs. THF) allows N,N′-dimethylbenzimidazolin-2-ylidene to be obtained quantitatively as a metastable, kinetic product. This free carbene had been previously reported to dimerize directly to the olefin-dimer, which is the thermodynamic product.

Graphical abstract: Wanzlick's equilibrium in tri- and tetraaminoolefins

Supplementary files

Article information

Article type
Research Article
Submitted
05 Sep 2021
Accepted
13 Okt 2021
First published
14 Okt 2021
This article is Open Access
Creative Commons BY-NC license

Org. Chem. Front., 2021,8, 6663-6669

Wanzlick's equilibrium in tri- and tetraaminoolefins

J. Messelberger, M. Kumar, S. J. Goodner and D. Munz, Org. Chem. Front., 2021, 8, 6663 DOI: 10.1039/D1QO01320C

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