3,5-Dimethylphenylmagnesium bromide reacts with triisopropyl borate to give 3,5-dimethylphenylboronic acid and bis(3,5-dimethylphenyl)borinic acid. Conditions were found which allowed the clean preparation of bis(3,5-dimethylphenyl)borinic acid, which was coupled with a vinyl triflate using Suzuki crosscoupling conditions. Both aryl groups were efficiently transferred from boron in the Suzuki step. IntroductionEndothelin receptor antagonists have generated considerable interest as pharmaceutical agents due to the involvement of endothelin in conditions such as pulmonary hypertension, congestive heart failure, and renal failure. 1 PD 0182783 (1) is a potent endothelin A antagonist which was considered for the treatment of pulmonary hypertension. 2 Early toxicological studies required the rapid synthesis of 3 kg of 1. After briefly exploring Negishi-type cross-coupling strategies utilizing an arylzincate, 3 the Suzuki cross-coupling reaction 4 was investigated to form the penultimate methyl ester 2. 5