[Cl:1][C:2]1[CH:13]=[CH:12][C:5]2[CH2:6][CH:7]([C:9]([OH:11])=[O:10])[O:8][C:4]=2[C:3]=1[Cl:14].[O:15]1[CH:19]=[CH:18][CH:17]=[C:16]1[C:20](Cl)=[O:21].[Cl-].[Al+3].[Cl-].[Cl-]>C(Cl)Cl>[Cl:1][C:2]1[C:13]([C:20]([C:16]2[O:15][CH:19]=[CH:18][CH:17]=2)=[O:21])=[CH:12][C:5]2[CH2:6][CH:7]([C:9]([OH:11])=[O:10])[O:8][C:4]=2[C:3]=1[Cl:14]To a well stirred mixture of 6,7-dichloro-2,3-dihydro-benzofuran-2-carboxylic acid (3.3 g.), furan-2-carbonyl-chloride (3.6 g.) and 200 ml. methylene chloride, protected from the atmosphere with a calcium chloride tube is added anhydrous aluminum chloride (3.7 g.) over a one-half hour period. The reaction solution is stirred 18 hours at 25° C. and then refluxed for 1 hour. The solvent is removed and the residue added to ice water (200 ml.) and hydrochloric acid (20 ml.). The product is extracted into ether, washed with water, then extracted into aqueous sodium bicarbonate (200 ml.) from which the sodium salt of the product precipitates. The sodium salt of the product is placed in a separatary funnel with dilute hydrochloric acid (100 ml.) and ether (100 ml.) and shaken until the solid dissolves. The ether solution is washed with water, brine, dried over magnesium sulfate and the ether distilled at reduced pressure. The 6,7-dichloro-2,3-dihydro-5-(2-furoyl)benzofuran-2-carboxylic acid melts at 166° C after crystallization from acetonitrile/n-butyl chloride.
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