反应详情

Lithium diisopropylamide mono(tetrahydrofuran) (1.5M in cyclohexane, 6.18 mL, 9.26 mmol) was added to a stirred suspension of 6,7-dichloro-2,3-dimethoxyquinoxaline (Preparation 1, 2.0 g, 7.72 mmol) in dry tetrahydrofuran (150 mL) at −78° C., under nitrogen. After 1 hour at −78° C., trimethyl borate (1.47 mL, 2.0 g, 19.3 mmol) was added. The solution was stirred for a further 1 hour and then left to reach room temperature over 18 hours. Water (50 mL) was added, the solution was acidified to pH 1 with 2M aqueous hydrochloric acid solution and extracted with dichloromethane (3×150 mL). The combined organic extracts were dried (MgSO4) and concentrated under reduced pressure. The residue was purified by flash chromatography on silica gel, by gradient elution using dichloromethane:methanol (100:0 changing to 99:1, by volume) as the eluent to afford 6,7-dichloro-2,3-dimethoxyquinoxaline-5-boronic acid (0.610 g, 26%) as a light brown solid.

1. waitleft
2. waitto reach room temperature over 18 hours
3. extractionextracted with dichloromethane (3×150 mL)
4. dry with materialThe combined organic extracts were dried (MgSO4)
5. concentrationconcentrated under reduced pressure
6. customThe residue was purified by flash chromatography on silica gel, by gradient elution