title: N-alkyl-4-boronopyridinium halides versus boric acid as catalysts for the esterification of alpha-hydroxycarboxylic acids.
abstract: [reaction: see text] Boric acid is a highly effective catalyst for the dehydrative esterification reaction between equimolar mixtures of alpha-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.
authors.affiliation: Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa, Japan.
authors.forename: Toshikatsu
authors.initials: T
authors.lastname: Maki
authors.forename: Kazuaki
authors.initials: K
authors.lastname: Ishihara
authors.forename: Hisashi
authors.initials: H
authors.lastname: Yamamoto