Radical [1,3] Rearrangements of Breslow Intermediates

Breslow intermediates that bear radical‐stabilizing N substituents, such as benzyl, cinnamyl, and diarylmethyl, undergo facile homolytic CN bond scission under mild conditions to give products of formal [1,3] rearrangement rather than benzoin condensation. EPR experiments and computational analysis...

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Bibliographic Details
Published in:Angewandte Chemie International Edition 2016-01, Vol.55 (1), p.355-358
Main Authors: Alwarsh, Sefat, Xu, Yi, Qian, Steven Y., McIntosh, Matthias C.
Format: Article
Language:English
Subjects:
Alcohols - chemical synthesis
Alcohols - chemistry
Benzoin
Breslow intermediates
Carboxy-Lyases - chemistry
Carboxy-Lyases - metabolism
Cleavage
Computer applications
Condensates
Enzymes
Free Radicals - chemical synthesis
Free Radicals - chemistry
Intermediates
Molecular Structure
N-heterocyclic carbenes
Quantum Theory
radicals
rearrangement
Thiamine
Thiamine - chemical synthesis
Thiamine - chemistry
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Summary:Breslow intermediates that bear radical‐stabilizing N substituents, such as benzyl, cinnamyl, and diarylmethyl, undergo facile homolytic CN bond scission under mild conditions to give products of formal [1,3] rearrangement rather than benzoin condensation. EPR experiments and computational analysis support a radical‐based mechanism. Implications for thiamine‐based enzymes are discussed. Taking radical action: The reaction of azolium salts having radical‐stabilizing N substituents with aromatic aldehydes affords products of formal [1,3] rearrangement instead of benzoin condensation. The surprising instability of the Breslow intermediate leads to NC bond homolysis at temperatures as low as room temperature.
ISSN:1433-7851
1521-3773
DOI:10.1002/anie.201508368