Although boric acid (B(OH)3) and boronic acids (RB(OH)2) behave as oligomeric mixtures, these boron compounds, as well as borane, electrophilically activate carboxylic acids as a mixed anhydride under equilibrium. In particular, electron-deficient arylboronic acids are useful as Lewis or Brønsted acid catalysts. The pKa of boronic acids is in the range of 5–9, which is significantly higher than that of the strong protic acids. However, diortho-substituted arylboronic acids with electron-withdrawing groups are unstable and are easily decomposed by basepromoted protodeboronation. In this chapter, the main emphasis is upon the recent progress on boronic acid-catalyzed reactions of carboxylic acids, as well as a few other reactions which can be catalyzed by boronic acids.
Ishihara, K. (2015). Boronic acid-catalyzed reactions of carboxylic acids. Topics in Organometallic Chemistry, 49, 243–270. https://doi.org/10.1007/978-3-319-13054-5_8