A mixture of ethyl 7-[(2-thienylsulfonyl)amino]-5-(trifluoromethoxy)-1H-indole-2-carboxylate (3.0 g), 1N aqueous sodium hydroxide solution (20 mL), tetrahydrofuran (10 mL) and ethanol (10 mL) was stirred at 60° C. for 1 hr. The reaction mixture was acidified with 1N hydrochloric acid, and extracted with ethyl acetate. The ethyl acetate layer was washed with saturated brine, dried (MgSO4), and concentrated. The residue was washed with hexane to give the title compound (2.60 g, yield 93%) as pale-yellow crystals. The crystals were recrystallized from ethyl acetate-hexane to give pale-yellow prism crystals. melting point 288-290° C. (decomposition).
