Synthesis
General procedure for the synthesis of quinoline-3-boronic acid from 3-bromoquinoline: triisopropyl borate (3.30 mL, 29.06 mmol) and 3-bromoquinoline (3.00 g, 14.49 mmol) were added to a 250 mL two-necked round-bottomed flask under nitrogen protection and dissolved in anhydrous tetrahydrofuran (100 mL). The reaction system was cooled to -78 °C and a 2M hexane solution of n-butyllithium (14.50 mL, 29.00 mmol) was slowly added dropwise through a dropping funnel over a controlled period of 1 hour. After the dropwise addition, the reaction was kept at -78 °C for 2 hours. Subsequently, the acetone/dry ice bath was removed and the reaction system was slowly warmed to 0 °C. The reaction was quenched with 2 M hydrochloric acid solution, followed by adjusting the pH with 2 M sodium bicarbonate solution to 7. The reaction mixture was extracted with ethyl acetate (3 x 100 mL). The organic phases were combined, dried over anhydrous magnesium sulfate and concentrated to dryness under reduced pressure. The product was precipitated by addition of hexane to give a white solid in 80% yield.
References
[1] Dyes and Pigments, 2013, vol. 99, # 1, p. 105 - 115
[2] Synthetic Communications, 2003, vol. 33, # 5, p. 795 - 800
[3] Journal of Organic Chemistry, 2002, vol. 67, # 15, p. 5394 - 5397
[4] Patent: US2009/181941, 2009, A1. Location in patent: Page/Page column 49-50
[5] Journal of the American Chemical Society, 2012, vol. 134, # 28, p. 11667 - 11673
