Arylboronate

An arylboronate is a boronate ester in which an aryl group is bonded to boron, and boron carries two alkoxy substituents derived from a diol. The general structure is ArB(OR')2, where Ar is an aryl group and OR' comes from the diol used to form the ester. The term encompasses a family of compounds used as stable, isolable boron partners in various transformations.

Common representatives include pinacol boronate esters (often written ArB(pin)) and MIDA boronates (ArB(MIDA)). These esters are typically prepared by esterification of arylboronic acids (ArB(OH)2) with a diol under dehydrating conditions, or by transesterification of existing boronate esters with the chosen diol. The choice of diol influences stability and reactivity in subsequent reactions.

Properties of arylboronates include enhanced air and moisture stability relative to many boronic acids, which facilitates handling. Their reactivity in cross-coupling and other boron-mediated transformations can be tuned by the ester group; transmetalation steps in Suzuki–Miyaura couplings often proceed after activation by base, sometimes via boronate exchange or formation of boronate species in situ.

Applications center on cross-coupling and late-stage functionalization. Arylboronates serve as versatile partners in Suzuki–Miyaura reactions and related processes, enabling efficient formation of biaryl and substituted aryl products. MIDA boronates, in particular, are valued for their exceptional stability and are used in iterative or automated synthesis, where controlled release of the arylboron component is desirable.

See also: boronic acid, Suzuki–Miyaura coupling, MIDA boronates.