N-Alkyl-4-boronopyridinium Halides versus Boric Acid as Catalysts for the Esterification of α-Hydroxycarboxylic Acids
- 1 October 2005
- journal article
- letter
- Published by American Chemical Society (ACS) in Organic Letters
- Vol. 7 (22) , 5047-5050
- https://doi.org/10.1021/ol052061d
Abstract
Boric acid is a highly effective catalyst for the dehydrative esterification reaction between equimolar mixtures of α-hydroxycarboxylic acids and alcohols. In contrast, N-methyl-4-boronopyridinium iodide (2a) is a more effective catalyst than boric acid for the similar esterification in excess alcohol. A heterogeneous catalyst, such as N-polystyrene-bound 4-boronopyridinium chloride, is also an effective catalyst and can be recovered by filtration.Keywords
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