F[C:2]1[C:9]([C:10]([F:13])([F:12])[F:11])=[CH:8][CH:7]=[CH:6][C:3]=1[CH:4]=O.[C:14]([O:18][CH3:19])(=[O:17])[CH2:15][SH:16].C(=O)([O-])[O-].[K+].[K+].CN(C=O)C>O>[F:11][C:10]([F:13])([F:12])[C:9]1[C:2]2[S:16][C:15]([C:14]([O:18][CH3:19])=[O:17])=[CH:4][C:3]=2[CH:6]=[CH:7][CH:8]=1
A mixture of 600 mg of 2-fluoro-3-(trifluoromethyl)benzaldehyde, 398 mg of methyl thioglycolate, 694 mg of potassium carbonate and 10 ml of DMF was stirred at 140° C. for 2 hours. The reaction mixture was cooled down to room temperature. To the reaction mixture was added water, and the mixture was washed with tert-butyl methyl ether three times. To the aqueous layer was added hydrochloric acid, then, the mixture was extracted with tert-butyl methyl ether three times. The combined organic layers were washed with water and saturated saline, and dried over magnesium sulfate, then, concentrated under reduced pressure. To the residue was added water to cause deposition of a solid which was then collected by filtration, and dried under reduced pressure. To the resultant solid were added 20 ml of methanol and 0.31 ml of oxalyl chloride, and the mixture was stirred at 80° C. for 2 hours. The reaction mixture was cooled down to room temperature, then, concentrated under reduced pressure. The residue was subjected to silica gel column chromatography, to obtain 338 mg of methyl 7-(trifluoromethyl)benzo[b]thiophene-2-carboxylate (present condensed ring compound 4).
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