[CH2:1]([O:3][C:4](=[O:16])/[CH:5]=[C:6](/[O:8][C:9]1[CH:14]=[CH:13][CH:12]=[CH:11][C:10]=1[Cl:15])\[CH3:7])[CH3:2].[Br:17]N1C(=O)CCC1=O.O>ClCCl.N(C(C)(CC(C)C)C#N)=NC(C)(CC(C)C)C#N>[CH2:1]([O:3][C:4](=[O:16])/[CH:5]=[C:6](/[O:8][C:9]1[CH:14]=[CH:13][CH:12]=[CH:11][C:10]=1[Cl:15])\[CH2:7][Br:17])[CH3:2]To a solution of (E)-3-(2-chloro-phenoxy)-but-2-enoic acid ethyl ester (1880 g, 7.82 mol) in dichloromethane (18.6 L) was added N-bromosuccinimide (1490 g, 8.29 mol) and 2,2′-azobis(2,4-dimethylvaleronitrile) (47 g, 0.188 mol) and the resulting solution heated to reflux for 23 h. The light yellow solution was cooled to room temperature and transferred to an extractor before water (19 L) was added. The biphasic mixture was stirred at room temperature for 1 h. The mixture was separated and the organic phase washed with a 20% sodium chloride solution (19 L). The solution was evaporated to give (E)-4-bromo-3-(2-chloro-phenoxy)-but-2-enoic acid ethyl ester (87.8% pure by HPLC, 2824 g, 99%) as a red oil.
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