Urea-Induced Acid Amplification: A New Approach for Metal-Free Insertion Chemistry

The enhanced catalytic activity of difluoroboronate ureas proved to be essential as an acidity amplifier to promote metal‐free OH and SH insertion reactions of α‐aryldiazoacetates in high yield. This methodology was found to be generally applicable to a broad substrate scope and presents a concept...

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Bibliographic Details
Published in:Chemistry : a European journal 2014-07, Vol.20 (27), p.8283-8287
Main Authors: Couch, Erica D., Auvil, Tyler J., Mattson, Anita E.
Format: Article
Language:English
Subjects:
acidity
Amplification
Arrays
Chemical reactions
Chemistry
diazo compounds
Esters
Insertion
organocatalysis
Strategy
Transformations
urea
Ureas
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Summary:The enhanced catalytic activity of difluoroboronate ureas proved to be essential as an acidity amplifier to promote metal‐free OH and SH insertion reactions of α‐aryldiazoacetates in high yield. This methodology was found to be generally applicable to a broad substrate scope and presents a conceptually new approach for organocatalytic diazo insertion reactions. Mechanistic investigations suggest that the reaction pathway involves a urea‐induced protonation of the α‐aryldiazoester. All amped up: Boronate ureas amplify the acidity of protic heteroatoms for metal‐free, catalytic OH and SH insertions by α‐diazocarbonyls. The enhanced activity of difluoroboronate ureas is essential for successful insertion reactions; conventional (thio)ureas do not catalyze the desired transformations. This new strategy for metal‐free insertions provides access to a broad array of α‐acyloxy esters and α‐mercaptoesters in high yield (see scheme).
ISSN:0947-6539
1521-3765
DOI:10.1002/chem.201403283