Synthesis
Under nitrogen protection, 4-bromo-2-methylpyridine, a certain proportion of tributyl borate and tetrahydrofuran were added to a four-necked flask, and the temperature was lowered to -68-70. Add n-butyllithium dropwise into the quartet until the solution was yellow. The solution was kept warm for 1 h. Dilute HCl was then added immediately to hydrolyze the solution. The solution first produced precipitation, with the gradual disappearance of precipitation, adjust the pH value of the system to 1. To the solution of NaOH solution with a mass fraction of 25% was added dropwise to the pH value of 13, stirring for 1 h. Separation of the liquid, the organic phase was extracted with 15 mL of NaOH with a mass fraction of 10%, and the aqueous phase was combined, and the alkaline solution was extracted with 15 mL of THF for 2 times, respectively. The obtained alkaline solution was adjusted to pH with dilute HCl, turbidity was generated at the beginning, flocculent appeared slowly, and the pH was adjusted to 5.0. The aqueous phase was extracted with 70 mL of tetrahydrofuran, and the organic phase was spin-dried and purified to obtain the product 2-methyl-4-pyridineboronic acid in 82.20% yield.
