由醛酮或酚制备硼酸酯的新方法

近期， 四川大学曾小明教授课题组报道了一种由酮和酚制备硼酸酯的新方法。在铬催化下，利用频哪醇硼烷和各种烯基三氟甲磺酸酯和非活化的芳基羧酸酯反应分别得到相应的烯基和芳基硼酸酯 。【 Org. Lett. 2022, 24, 17, 3227–3231；https://doi.org/10.1021/acs.orglett.2c01015】

反应操作

Procedure A for the selective Borylation of vinyl triflates: In a dried Schlenk tube were placed vinyl triflates (0.2 mmol), CrCl3 (3 mg, 0.02 mmol), dtbpy (5 mg, 0.02 mmol), Mg (5 mg, 0.2 mmol) and HBpin (58 µL, 0.4 mmol) under atmosphere of nitrogen. After the addition of a freshly distilled THF (1 mL) by syringe, the resulting mixture was stirred at 40 °C in an oil bath for 18 h. The volatiles were removed under vacuum, and the crude product was purified by silica gel chromatography to give the corresponding vinyl boronate esters (3a-3h, 3j-3o, 3r, 3w)

Procedure E for the selective Borylation of aryl pivalates with HBpin: In a dried Schlenk tube were placed aryl pivalates (0.2 mmol), dtbpy-Cr complex (9 mg, 0.02 mmol), Mg (5 mg, 0.2 mmol) and HBpin (73 µL, 0.5 mmol) followed by adding a freshly distilled THF (1 mL) by syringe under atmosphere of nitrogen, and the reaction mixture was stirred at 90 °C in an oil bath for 6 h. The volatiles were removed under vacuum, and the crude product was purified by silica gel chromatography to give the aryl boronate esters (5a-5d, 5j-5l, 5n-5o, 5r)

参考资料

Chromium-Catalyzed Selective Borylation of Vinyl Triflates and Unactivated Aryl Carboxylic Esters with Pinacolborane；Li Gong, Chao Li, Fangyan Yuan, Senlin Liu, and Xiaoming Zeng*； Org. Lett. 2022, 24, 17, 3227–3231