Citric Acid → 4-(Methylthio)phenylboronic acid

Participants

Reaction Conditions

Reaction Steps

A stirred solution of 4-bromothioanisole (5.0 g, 0.0246 mol) in anhydrous tetrahydrofuran (THF) was chilled to −78° C. under a nitrogen atmosphere. A 2.5 M solution of n-butyl lithium (12 mL, 0.030 mol) in hexanes was added dropwise to the chilled solution. When the addition was complete, the reaction mixture was stirred at −78° C. for about 45 minutes. Trimethylborate (8.5 mL, 0.0748) was introduced via syringe. The reaction mixture was then allowed to warm to room temperature overnight. The room temperature solution was treated successively with 10% aqueous sodium hydroxide solution (50 mL) and water (33.5 mL) and stirred at room temperature for 1 hour. The reaction mixture was lowered to about pH=4-5 using 10% aqueous citric acid and the THF was removed under reduced pressure. The aqueous residue was saturated with sodium chloride and extracted with ethyl acetate. The organic extract was dried over MgSO4 and filtered. The filtrate was concentrated under reduced pressure to provide a white solid which was washed with hexanes to provide the product as a white solid (yield: 1.5 g; 36%). mp 170° C. 1H NMR (300 MHz, DMSO-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