Trimethyl borate → 4-(Methylthio)phenylboronic acid

Participants

Reaction Steps

Under nitrogen, a stirred solution of 30 g (150 mmol of 4-bromothioanisole (Aldrich) in 1500 mL of anhydrous THF at -78° C. was treated with 180 mmol of n-butyllithium in hexane. After 30 minutes, 51 mL (450 mmol) of trimethylborate was added neat and the reaction was allowed to warm to ambient temperature overnight. A solution of 300 mL of 10% NaOH was added and the mixture stirred vigorously for 1 hour. The solvent was removed in vacuo, the pH adjusted to 4-5, and the product collected by filtration. Repeated washings with hexane and water provided 21 g (83%) of 4-methylthiophenylboronic acid (21 in Synthetic Scheme VII when R5 =SCH3 and R3, R4, R6, and R7 =H) as a colorless solid: NMR (DHSO-d6) δ 2.47 (s, 3H), 7.20 (d, J=8 Hz, 2H), 7.71 (d, J=8 Hz, 2H), 7.96 (br s, 2H).

Provenance & Evidence