5-Fluorobenzothiophene-2-boronic acid

70060-12-7

121-43-7

501944-42-9

General procedure for the synthesis of 5-fluorobenzothiophene-2-boronic acid from 5-fluorobenzothiophene and trimethyl borate: 5-fluorobenzothiophene (0.374 g, 2.5 mmol) was dissolved in anhydrous tetrahydrofuran (3.5 mL) in a three-necked flask under argon protection. n-Butyllithium (1.2 mL, 3 mmol) was slowly added at -78 °C to -68 °C and reacted for 25 min. Subsequently, trimethyl borate (0.33 mL, 3 mmol) was added dropwise and the reaction mixture was slowly brought to room temperature with continuous stirring for 3 hours. Upon completion of the reaction, the pH was adjusted to 6 by adding dilute hydrochloric acid and diluted with water (50 mL). Extracted with ethyl acetate (50 mL x 3), the organic phases were combined, washed once with saturated saline (50 mL) and dried over anhydrous sodium sulfate. Purified by silica gel column chromatography with dichloromethane:methanol=25:1 as eluent, a light yellow solid powder was obtained (target product 5-fluorobenzothiophene-2-boronic acid, 0.2 g, yield 38%).