1-Bromo-2-methylpropane → 2-(3,4-Dichloro-phenyl)-4-methyl-pentanoic acid ethyl ester

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A solution of freshly prepared lithium diisopropylamide (4.88 mL of 0.29 M stock solution, 1.41 mmol) cooled to −78° C. was treated with (3,4-dichloro-phenyl)-acetic acid ethyl ester (300 mg, 1.28 mmol) in tetrahydrofuran/hexamethylphosphoramide (3.2 mL, 3:1). The resulting solution was stirred at −78° C. for 45 min. At this time, the reaction was treated with a solution of 1-bromo-2-methyl-propane (1.53 mL, 1.41 mmol) in hexamethylphosphoramide (1 mL). The reaction mixture was stirred at −78° C. for 6 h. The reaction was then warmed to 25° C. and stirred at 25° C. for 16 h. The reaction mixture was then quenched by the dropwise addition of saturated aqueous ammonium chloride solution (1 mL). This mixture was poured into water (50 mL) and extracted with ethyl acetate (3×50 mL). The organics were dried over sodium sulfate, filtered, and concentrated in vacuo. Flash chromatography (Merck Silica gel 60, 230-400 mesh, 50/50 hexanes/ethyl acetate) afforded 2-(3,4-dichloro-phenyl)-4-methyl-pentanoic acid ethyl ester (356.4 mg, 95.8%) as a clear oil: EI-HRMS m/e calcd for C14H18Cl2O2 (M+) 288.0683, found 288.0677.

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