The triplet state of deprotonated mesoionic carbene Breslow intermediates is thermally accessible: Distal difunctionalization of aldehydes - CNRS - Centre national de la recherche scientifique Access content directly
Journal Articles Chem Catalysis Year : 2022

The triplet state of deprotonated mesoionic carbene Breslow intermediates is thermally accessible: Distal difunctionalization of aldehydes

Abstract

N-Heterocyclic carbene (NHC)-catalyzed transformations through electron-pair-transfer processes have witnessed remarkable developments in the past decades, especially the umpolung of aldehydes via the Breslow intermediates (BIs). The role of BIs in single-electron transfer (SET) pathways has long been established in biosynthesis, and in the last decade, it was extended to NHC organocatalysis. Here, we report that deprotonated mesoionic carbene BIs (BI-s) have an astonishing small singlet/triplet (S/T) gap of only 4.0 kcal/mol, resulting in a thermally accessible triplet state. This low-lying excited state allows for a series of distal difunctionalizations of aryl aldehydes via biradical processes. At the formyl side, an oxidative esterification reaction takes place concomitantly with a reduction of the aryl side. Here, three types of chemical transformation are demonstrated: hydro(deutero)defunctionalization, hydrogenation, and reductive alkylation.
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Dates and versions

hal-03872960 , version 1 (27-11-2023)

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Zengyu Zhang, Shiqing Huang, Chen-Yuan Li, Liang-Liang Zhao, Wei Liu, et al.. The triplet state of deprotonated mesoionic carbene Breslow intermediates is thermally accessible: Distal difunctionalization of aldehydes. Chem Catalysis, 2022, 2 (12), pp.3517-3527. ⟨10.1016/j.checat.2022.09.047⟩. ⟨hal-03872960⟩

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