S(=O)(=O)(O)O.[NH2:6][C:7]1[C:12]2[CH2:13][CH2:14][O:15][C:11]=2[C:10]([C:16]([OH:18])=[O:17])=[CH:9][C:8]=1[Cl:19].[CH3:20]O.N>CO>[NH2:6][C:7]1[C:12]2[CH2:13][CH2:14][O:15][C:11]=2[C:10]([C:16]([O:18][CH3:20])=[O:17])=[CH:9][C:8]=1[Cl:19]Sulfuric acid (18 ml) was added dropwise to cooled methanol (90 ml). 4-Amino-5-chloro-2,3-dihydro-7-benzofurancarboxylic acid (20 g) was added to the mixture which was subsequently stirred and refluxed for 3 hours. The reaction mixture was cooled and alkalized with CH3OH/NH3. The solvent was evaporated and the residue stirred in water. The precipitate was filtered off and washed with water and DIPE. The remaining solid was dried, yielding 17.2 g (81%) of methyl 4-amino-5-chloro-2,3-di-hydro-7-benzofurancarboxylate (intermediate 1; mp. 135.4° C.).
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