N[C:2]1[C:12]([O:13][CH3:14])=[CH:11][C:5]([C:6]([O:8][CH2:9][CH3:10])=[O:7])=[CH:4][C:3]=1[Cl:15].C(#N)C.[I:19]CI.N(OCCC(C)C)=O>CCCCCCC.C(OCC)(=O)C>[Cl:15][C:3]1[CH:4]=[C:5]([CH:11]=[C:12]([O:13][CH3:14])[C:2]=1[I:19])[C:6]([O:8][CH2:9][CH3:10])=[O:7]To ethyl 4-amino-3-chloro-5-methoxybenzoate (15.8 g, 68.8 mmol) were added acetonitrile (40 mL) and diiodomethane (22.2 mL, 275 mmol) in that order, and then the mixture was stirred at 70° C. and isoamyl nitrite (13.9 mL, 103 mmol) was added dropwise over a period of 10 minutes. The mixture was then stirred at 70° C. for 40 minutes. After returning the mixture to room temperature, the solvent in the mixture was distilled off under reduced pressure and the residue was purified by silica gel column chromatography (mixture of n-heptane and ethyl acetate: n-heptane/ethyl acetate=8/1 then 5/1) to obtain the title compound (15.6 g, 45.8 mmol).
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