[O:1]=[C:2]1[C:10]2[C:5](=[CH:6][C:7]([O:13][CH2:14][C:15]([OH:17])=[O:16])=[C:8]([Cl:12])[C:9]=2[Cl:11])[CH2:4][CH:3]1[CH2:18][CH3:19].[Br:20]Br.S(=O)(O)[O-].[Na+]>C(O)(=O)C.Br>[O:1]=[C:2]1[C:10]2[C:5](=[CH:6][C:7]([O:13][CH2:14][C:15]([OH:17])=[O:16])=[C:8]([Cl:12])[C:9]=2[Cl:11])[CH2:4][C:3]1([Br:20])[CH2:18][CH3:19]To a stirred suspension of (1-oxo-2-ethyl-6,7-dichloro-5-indanyloxy)acetic acid (30.3 g., 0.10 moles) in acetic acid (300 ml.) is added a solution of bromine (16.0 g., 0.10 moles) in acetic acid (50 ml.) over a period of 30 minutes. The reaction is catalyzed by the addition of 48% aqueous hydrobromic acid (2 drops). The clear yellow solution is stirred at room temperature for 30 minutes then poured into ice water (1 l.) containing sodium bisulfite (2 g.). The crude (1-oxo-2-bromo-2-ethyl-6,7-dichloro-5-indanyloxy)acetic acid (36 g., 97%) thus obtained is filtered, washed with water and dried. It melts at 189°-191° C. after recrystallization from a mixture of ethyl acetate and hexane.
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