Acetyl chloride → 2-(4-Chloro-2-fluoro-3-methoxyphenyl)-1,3,2-dioxaborinane

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To a solution of 1-bromo-4-chloro-2-fluoro-3-methoxybenzene (10.4 g, 0.043 mol) in diethyl ether (150 mL) at −78° C. was slowly added n-butyl lithium (2.5M, 19.0 mL, 0.0475 mol), and the solution was stirred for thirty minutes. A solution of triisopropyl borate (12.0 g, 0.064 mL) in THF (25 mL) was slowly added and the solution warmed to 0° C. Acetyl chloride (10.0 g, 0.13 mol) was added. After stirring for one hour the solution was concentrated and the solid residue was partitioned between ethyl acetate (150 mL) and 1N sodium hydroxide (50 mL). Ice was added to the aqueous phase that was subsequently acidified with sufficient concentrated hydrochloric acid to obtain a pH of 2. The heterogeneous mixture was extracted with ethyl acetate (2×150 mL) and the combined organic phases were dried and concentrated. The resulting solid was slurried in toluene, propane-1,3-diol (6.6 g, 0.09 mol) was added, and the resulting mixture was heated under reflux to remove water via a Dean-Stark trap. After two hours, the mixture was allowed to cool and was concentrated under vacuum. The resulting oil was dissolved in methylene chloride (50 mL), washed with water (25 mL), dried, and concentrated to give 2-(4-chloro-2-fluoro-3-methoxyphenyl)-[1,3,2]-dioxaborinane (6.4 g, 0.062 mol): 1H NMR (CDCl3): δ 7.15 (m, 1H), 6.95 (dd, 1H), 4.05 (t, 4H), 3.8 (s, 3H), 1.95 (t, 2H).

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