boronates

Boronates are a class of boron-containing compounds that include salts and esters derived from boronic acids. In their neutral form, boronic acids feature a trigonal boron center with two hydroxyl groups (R–B(OH)2). When deprotonated or esterified, the boron becomes tetrahedral, giving boronate salts (boronate anions) or boronate esters, respectively.

Boronate esters are typically prepared by reacting boronic acids with diols to form cyclic boronates. A common example is the pinacol boronate ester (BPin), formed with pinacol as the diol. These esters are valued for their stability to air and moisture compared with the parent boronic acids, and they can be converted back to boronic acids under mild conditions when needed for further reactions.

Boronate salts arise from the interaction of boronic acids with bases, producing tetrahedral boronate anions such as sodium phenylboronate. These salts are generally more water-soluble and are useful as reagents or intermediates in boron-centered transformations, including various cross-coupling and hydroboration protocols.

Applications and significance: In organic synthesis, boronates serve as versatile boron sources in reactions such as Suzuki–Miyaura cross-coupling, where transmetalation transfers the boron moiety to a palladium catalyst. In medicinal chemistry, boron-containing motifs are explored as pharmacophores and as reversible covalent inhibitors. In carbohydrate chemistry, boronates form reversible binding with diols and sugars, enabling sensing, separation, and affinity-based technologies. See also boronic acids and borates for related boron-centered chemistry.