[H-].[Na+].[Br:3][C:4]1[CH:5]=[C:6]([CH2:16][C:17]([O:19][CH2:20][CH3:21])=[O:18])[CH:7]=[C:8]([Cl:15])[C:9]=1[O:10][CH2:11][CH:12]1[CH2:14][CH2:13]1.Cl>CN(C=O)C.O>[Br:3][C:4]1[CH:5]=[C:6]([CH:16]([CH2:4][CH2:9][O:10][CH3:11])[C:17]([O:19][CH2:20][CH3:21])=[O:18])[CH:7]=[C:8]([Cl:15])[C:9]=1[O:10][CH2:11][CH:12]1[CH2:13][CH2:14]1
To a stirred solution of NaH (0.3 g, 12.5 mmol) in DMF (10 mL) was added ethyl 2-(3-bromo-5-chloro-4-(cyclopropylmethoxy)phenyl)acetate (2.0 g, 5.70 mmol) at 0° C. The reaction mixture was stirred at 0° C. over a period of 30 min. To the reaction mixture was added 2-bromo ethyl methyl ether (0.87 g, 6.25 mmol) and stirred at 0° C. for 30 min. After completion of starting material (by TLC), the reaction mixture was diluted with water (20 mL), acidified with 1N HCl (pH=5) and extracted with EtOAc (3×50 mL). Combined organic layers were washed with water (3×25 mL), brine and dried over anhydrous Na2SO4. After filtration and concentration under reduced pressure, the crude material was purified by column chromatography to afford ethyl 2-(3-bromo-5-chloro-4-(cyclopropylmethoxy)-phenyl)-4-methoxybutanoate (560 mg) as an off white solid.
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