Citric Acid → 4-(Methylthio)phenylboronic acid

Temperature

-78 °C

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).

1. additionWhen the addition
2. temperatureto warm to room temperature overnight
3. stirringstirred at room temperature for 1 hour
4. customthe THF was removed under reduced pressure
5. extractionextracted with ethyl acetate
6. extractionThe organic extract
7. dry with materialwas dried over MgSO4
8. filtrationfiltered
9. concentrationThe filtrate was concentrated under reduced pressure
10. customto provide a white solid which
11. washwas washed with hexanes

ORD record

ord-eb5ccd9d41824e8dbca17e80a2102a0b

Source dataset

uspto-grants-2001_10

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US06307047B1