Hydrochloric Acid → (5-Methylthiophen-3-yl)boronic acid

Participants

Reaction Conditions

Reaction Steps

4-Bromo-2-methylthiophene (300 mg, 1.69 mmol) and triisopropyl borate (486 μL, 2.12 mmol) were dissolved in THF (1 mL) and the solution was vacuumed and filled with N2 3 times. The solution was cooled to −70° C. using an acetone/dry ice bath. 2.5 M of n-BuLi in hexane (1.0 mL, 2.54 mmol) was added drop wise and the mixture was stirred for an additional 30 minutes while the temperature was held at −70° C. The reaction mixture was allowed to warm up to −20° C. and 2 mL of 3 N HCl was added. When the mixture was warmed up to room temperature, two layers were separated. The water layer was neutralized to about pH 7, using 5 N NaOH. Both layers were extracted with EtOAc and washed with brine. The organic layer was dried over anhydrous Na2SO4. The material was not further purified and was used directly in the next step. MS (ESI): 143.05 [M+H]+; HPLC tR=1.30 min (HPLC: Anayltical—2 min).

Provenance & Evidence