Synthesis
Under nitrogen protection, 300 g of anhydrous tetrahydrofuran was added to the reaction flask with stirring turned on, followed by the addition of 12 g of 3-cyanopyridine and cooling of the system to -30°C. The reaction was carried out under nitrogen protection. Slowly 70 mL of 2.0 M n-butyllithium solution was added dropwise. After stirring for 30 minutes, 1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclododecane solution was added slowly dropwise. After 2 hours of reaction, 41 mL of triisopropyl borate was slowly added dropwise. Stirring was continued at -30°C for 1 hour, then slowly warmed to room temperature and stirred for 1 hour. To the reaction mixture was added 400 g of concentrated hydrochloric acid and stirred for 1 hour for hydrolysis. After completion of the reaction, the reaction was left to partition and the organic layer was washed with water three times (100 g each). The aqueous layer was combined and extracted once with 100 mL of petroleum ether. The organic layers were combined, dried with 50 g of anhydrous sodium sulfate and filtered. The filtrate was concentrated to dryness to give 14 g of 3-cyano-4-pyridineboronic acid.
