Trimethyl borate → (2-Bromo-6-methoxyquinolin-3-yl)boronic acid

Participants

Reaction Conditions

Reaction Steps

n-BuLi (1.6 N in hexanes, 14.4 mL, 23.0 mmol) was added at −78° C. to a solution of 2,2,6,6-tetramethylpiperidine (3.11 g, 22.05 mmol) in anhydrous THF (59 mL), and the mixture was then warmed to 0° C. for 0.5 h. The mixture was cooled back to −78° C. and treated with a solution of 2-bromo-6-methoxyquinoline (4.57 g, 19.17 mmol) in THF (14 mL). After stirring for 1 h, a solution of trimethyl borate (2.46 mL, 22.05 mmol) in THF (14 mL) was added, and the mixture was maintained at −78° C. for a further 2 h. A mixture of THF (14 mL) and H2O (3.5 mL), were added then the solution was warmed to −10° C. and treated with water (70 mL) and Et2O (70 mL). Aqueous NaOH (1 N, 75 mL) was added, and the aqueous layer was separated and acidified to pH 4 with aqueous HCl (3 N). The aqueous phase was extracted with Et2O, and the combined extracts were washed with brine and dried over Na2SO4. Filtration and removal of the volatiles afforded the title compound (4.64 g, 86% yield) as an oily solid that was used directly in the subsequent step. LCMS (ES+) m/z 282, 284 (M+H)+.

Provenance & Evidence