Numerous methods exist to synthesize phenylboronic acid. One of the most common synthesis uses phenylmagnesium bromide and trimethyl borate to form the ester PhB(OMe), which is then hydrolyzed to the product.
:PhMgBr + B(OMe) → PhB(OMe) + MeOMgBr
:PhB(OMe) + HO → PhB(OH) + MeOH
Other routes to phenylboronic acid involve electrophilic borates to trap phenylmetal intermediates from phenyl halides or from directed ortho-metalation. Phenylsilanes and phenylstannanes transmetalate with BBr, followed by hydrolysis form phenylboronic acid. Aryl halides or triflates can be coupled with diboronyl reagents using transition metal catalysts. Aromatic C-H functionalization can also be done using transition metal catalysts.