3-Cyano-4-(4,4,5,5-tetramethyl-[1,3,2]dioxaborolan-2-yl)pyridine

100-54-9

76-09-5

878194-92-4

In a dry 500 mL three-necked flask protected by nitrogen, 2,2,6,6-tetramethylpiperidine (57.6 mmol) was dissolved in anhydrous tetrahydrofuran (200 mL), and after the reaction system was cooled to -10 °C, n-butyllithium (57.6 mmol, 2.5 M hexane solution) was added slowly and dropwise over a period of 2 minutes. After the dropwise addition, stirring was continued for 10 min, followed by cooling the reaction system to -78 °C. Triisopropyl borate (65.3 mmol) was added within 2 min at -78 °C and stirred for 5 min at this temperature. Then, 3-cyanopyridine (48 mmol) dissolved in anhydrous tetrahydrofuran (50 mL) was added with a dropwise addition time of 5 minutes. The reaction mixture was slowly warmed to room temperature in a dry ice bath and stirred overnight. Upon completion of the reaction, the reaction was quenched with glacial acetic acid (67.2 mmol) followed by the addition of pinacol (72 mmol). Stirring was continued for 2 hours at room temperature. The reaction mixture was transferred to a dispensing funnel, diluted by adding dichloromethane (75 mL) and washed with 10% w/v aqueous potassium dihydrogen phosphate solution (4 x 60 mL). The aqueous phase was back-extracted once with dichloromethane (15 mL), the organic phases were combined and dried over anhydrous magnesium sulfate. The solvent was concentrated under reduced pressure to afford the target product 3-cyano-4-pyridineboronic acid pinacol ester (3b) as a yellow solid in 18% yield with a melting point of 88°C. The product was analyzed by IR, 1H NMR and 1H NDT. The product was characterized by IR, 1H NMR and 13C NMR to confirm the structure.