ArticleChemistry (Weinheim an der Bergstrasse, Germany)2021
Breslow Intermediates (Amino Enols) and Their Keto Tautomers: First Gas-Phase Characterization by IR Ion Spectroscopy.
Article in Chemistry (Weinheim an der Bergstrasse, Germany), 2021. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 10 papers.
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10 citing papers in PubMed, 25 citations in OpenAlex.
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- Light on Catalytic Reaction Mechanisms: Uncovering the Conformation of Thiourea-Based Organocatalysts and Their Interaction with Nitroolefins Using Mid-infrared Spectroscopy.The journal of physical chemistry letters · 2025Article
- Recent Advances in Chemical Synthesis of Amino Sugars.Molecules (Basel, Switzerland) · 2023Review
- Rate and equilibrium constants for the addition of triazolium salt derived N-heterocyclic carbenes to heteroaromatic aldehydes.Chemical science · 2022Article
- Synthesis of Highly Congested Tertiary Alcohols via the [3,3] Radical Deconstruction of Breslow Intermediates.Organic letters · 2022Article
- Formation of Breslow Intermediates from N-Heterocyclic Carbenes and Aldehydes Involves Autocatalysis by the Breslow Intermediate, and a Hemiacetal.Angewandte Chemie (International ed. in English) · 2022Article
- An Unexpected Inactivation ofFrontiers in chemistry · 2022Article
- Critical Assessment of the Reducing Ability of Breslow-type Derivatives and Implications for Carbene-Catalyzed Radical Reactions*.Angewandte Chemie (International ed. in English) · 2021Article
- Tale of the Breslow intermediate, a central player in N-heterocyclic carbene organocatalysis: then and now.Chemical science · 2021Review
- Breslow Intermediates (Amino Enols) and Their Keto Tautomers: First Gas-Phase Characterization by IR Ion Spectroscopy.Chemistry (Weinheim an der Bergstrasse, Germany) · 2021Article
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11 authors at 3 institutions in 3 countries.
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Abstract
Breslow intermediates (BIs) are the crucial nucleophilic amino enol intermediates formed from electrophilic aldehydes in the course of N-heterocyclic carbene (NHC)-catalyzed umpolung reactions. Both in organocatalytic and enzymatic umpolung, the question whether the Breslow intermediate exists as the nucleophilic enol or in the form of its electrophilic keto tautomer is of utmost importance for its reactivity and function. Herein, the preparation of charge-tagged Breslow intermediates/keto tautomers derived from three different types of NHCs (imidazolidin-2-ylidenes, 1,2,4-triazolin-5-ylidenes, thiazolin-2-ylidenes) and aldehydes is reported. An ammonium charge tag is introduced through the aldehyde unit or the NHC. ESI-MS IR ion spectroscopy allowed the unambiguous conclusion that in the gas phase, the imidazolidin-2-ylidene-derived BI indeed exists as a diamino enol, while both 1,2,4-triazolin-5-ylidenes and thiazolin-2-ylidenes give the keto tautomer. This result coincides with the tautomeric states observed for the BIs in solution (NMR) and in the crystalline state (XRD), and is in line with our earlier calculations on the energetics of BI keto-enol equilibria.
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