Boronic acids can be obtained via several methods. The most common way is reaction of organometallic compounds based on lithium or magnesium (Grignards) with borate esters. For example, phenylboronic acid is produced from phenylmagnesium bromide and trimethyl borate followed by hydrolysis
:PhMgBr + B(OMe) → PhB(OMe) + MeOMgBr
:PhB(OMe) + 2 HO → PhB(OH) + 2 MeOH
Another method is reaction of an arylsilane (RSiR) with boron tribromide (BBr) in a transmetallation to RBBr followed by acidic hydrolysis.
A third method is by palladium catalysed reaction of aryl halides and triflates with diboronyl esters in a coupling reaction known as the Miyaura borylation reaction. An alternative to esters in this method is the use of diboronic acid or tetrahydroxydiboron ([B(OH)]).