7-cyanobenzo[b]thiophen-2-ylboronic acid

22780-71-8

1119899-37-4

The general procedure for the synthesis of 7-cyanobenzo[b]thiophene-2-ylboronic acid using benzo[B]thiophene-7-carbonitrile as starting material was as follows: first, benzo[B]thiophene-7-carbonitrile (20 g, 0.126 mol) was dissolved in anhydrous THF (500 mL) under nitrogen protection. Subsequently, the reaction mixture was cooled to -90 °C in a liquid nitrogen bath and n-butyllithium (2.5 M hexane solution, 60 mL, 0.15 mol) was slowly added dropwise with continuous stirring. After the dropwise addition was completed, the reaction mixture was continued to be stirred at -90 °C for 30 minutes. Next, trimethyl borate (26 g, 0.25 mol) was added to the reaction system and the reaction was continued at the same temperature for 30 minutes. Upon completion of the reaction, 2M HCl aqueous solution (300 mL) was added to neutralize the reaction mixture, at which point a solid precipitated. The mixture was continued to be stirred for 30 minutes and gradually warmed up to room temperature (about 30°C). Subsequently, the reaction mixture was poured into water (200 mL) and the precipitated solid was collected by filtration. Finally, the solid was washed with ice water and dried to give the target product 7-cyanobenzo[b]thiophen-2-ylboronic acid (18 g, 72% yield) as a white solid.