I[C:2]1[C:12]2[O:11][CH2:10][CH2:9][C:8]([C:13]([O:15][CH2:16][CH3:17])=[O:14])=[CH:7][C:6]=2[CH:5]=[CH:4][CH:3]=1.[C:18](=O)([O-:20])[O-:19].[K+].[K+].[C]=O>CN(C)C=O.C([O-])(=O)C.[Pd+2].C([O-])(=O)C>[C:18]([C:2]1[C:12]2[O:11][CH2:10][CH2:9][C:8]([C:13]([O:15][CH2:16][CH3:17])=[O:14])=[CH:7][C:6]=2[CH:5]=[CH:4][CH:3]=1)([OH:20])=[O:19]To a mixture of ethyl 2,3-dihydro-9-iodo-1-benzoxepin-4-carboxylate (5.62 g), potassium carbonate (9.03 g), and palladium(II) acetate (0.73 g) in aqueous N,N-dimethylformamide (48 ml, 67% v/v) was introduced carbon monoxide for 30 minutes. The reaction mixture was stirred for 2 days at ambient temperature in an atmosphere of carbon monoxide and partitioned between ethyl acetate and water. The aqueous layer was acidified with 1H hydrochloric acid and extracted with ethyl acetate. The organic layer was washed successively with saturated aqueous sodium thiosulfate and brine, dried over anhydrous magnesium sulfate, and evaporated in vacuo to give a solid of ethyl 9-carboxy-2,3-dihydro-1-benzoxepin-4-carboxylate (3.8 g).
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