Trimethyl borate → (4-Fluoro-2-methylphenyl)boronic acid

Participants

Reaction Steps

2-Bromo-5-fluorotoluene (52.9 mmol, 10 g) in 400 ml of tetrahydrofuran was cooled to −78° C. and n-butyllithium (2.5 M, 58.2 mmol) was added. The solution was stirred for 20 minutes, trimethoxy borane (3 eq, 0.16 mol) was added, and the reaction was allowed to warm to room temperature overnight. Sodium hydroxide (60 ml of 1.25 M) was added and the reaction was stirred for 30 minutes. The tetrahydrofuran was removed in vacuo. The remaining aqueous layer was diluted and extracted with diethyl ether. The aqueous layer was adjusted to pH 3 with 2N HCl and extracted with ethyl acetate, which was dried (MgSO4) and concentrated in vacuo to give 6.57 g (81%) of a colorless solid: MS(FAB) m/e (rel. intensity) 154(48), 136(100).

Provenance & Evidence