Acetyl chloride → (2,4-Dichloro-3-methoxyphenyl)boronic acid

Participants

Reaction Steps

To a solution of 1-bromo-2,4-dichloro-3-methoxybenzene (5.12 g, 20 mmol) in diethyl ether cooled to −70° C. was added 2.5M n-butyl lithium (8.8 mL, 22 mmol) in portions keeping the temperature below −60° C. The resulting reaction mixture was then stirred for 10 minutes before triisopropylborate (6.9 mL, 30 mmol) was added in portions keeping the temperature below −60° C. The reaction mixture was then allowed to warm to room temperature and acetyl chloride (60 mmol) was added. The reaction mixture was stirred for an hour at room temperature and concentrated. The residue was partitioned between ethyl acetate and 1N NaOH (40 mL) and the organic phase was extracted with additional 1N NaOH (10 mL). The sodium hydroxide extracts were combined, ice was added, and the solution was acidified to pH 3-4 with concentrated HCl. The product was then extracted with ethyl acetate and the organic phase was dried and concentrated to yield 2,4-dichloro-3-methoxyphenylboronic acid (3.27 g, 14.8 mmol): 1H NMR (CDCl3): δ 8.44 (br s, 2H), 7.42 (d, 1H), 7.15 (d, 1H), 3.8 (s, 3H).

Provenance & Evidence