preparation | in the past few decades, coupling reactions have been widely used in the synthesis of novel alkyl compounds or aromatic heterocyclic compounds. Among these transition metal-catalyzed coupling reactions, Suzuki coupling reactions are favored due to their mild reaction conditions, suitability for a variety of functional groups, relative stability in air, and relatively low toxicity. Therefore, chemical workers have a strong interest in the synthesis and activity of new boronic acid derivatives, these compounds, especially the nitrogen-containing heterocyclic boronic acid compounds, can be used for the establishment of combinatorial compound libraries in medicinal chemistry research. With 1-methyl -4-[(trifluoromethylsulfonyl) oxy]-1,2,3, 6-tetrahydropyridine as the starting material, preparation of 1-methyl -1,2,3, 6-tetrahydropyridine-4-boronic acid alkanol ester by esterification with boric acid. The reaction scheme is shown below: Fig. 1 1-methyl -1,2,3, 6-tetrahydropyridine-4-boronic acid zeolites reaction formula add 1-methyl -4-[(trifluoromethylsulfonyl) oxy]-1,2,3 to a 500 mL three-neck flask, 6-tetrahydropyridine, 150 mL of dry Tetrahydrofuran, stirred evenly under the protection of argon, 40mL of n-butyl lithium was slowly added dropwise below 5 ℃, and reacted at room temperature for 1 hour after dropping, the temperature was then lowered to -80 °c, 15 mL of trimethyl borate was added dropwise, and the mixture was stirred at -80 °c for 0.5 hours. The temperature was slowly raised to room temperature, and a 150 mL 15% ammonium chloride solution was added dropwise to neutralize the acid in the reaction solution, followed by stirring at room temperature for 1 hour. The organic layer was separated, the aqueous layer was extracted with ethyl acetate, and the organic phases were combined and dried over anhydrous magnesium sulfate. The filtrate was filtered with suction and evaporated to dryness under reduced pressure to give crude 1-methyl -1,2,3, 6-tetrahydropyridine-4-boronic acid, which was recrystallized from 5 volumes of water. Add 1-methyl -1,2,3, 6-tetrahydropyridine-4-boronic acid to a 250 mL three-necked flask, 100 dry Tetrahydrofuran, 1.8g( 0.015 3 mol) after dissolving the phanol by stirring, molecular sieve was added and the reaction was stirred at room temperature for 2 hours. After filtration, the filtrate was evaporated to dryness and dissolved in 100 of n-hexane. The organic phase was washed with water and dried over anhydrous magnesium sulfate. Suction filtration, and evaporation of the filtrate to dryness gave 1-methyl -1,2,3, 6-tetrahydropyridine-4-boronic acid cytanol ester. |