A mixture of ethyl 6-chloro-7-[(2-thienylsulfonyl)amino]-1H-indole-2-carboxylate (1.00 g), methyl iodide (0.17 mL), potassium carbonate (0.36 g) and N,N-dimethylformamide (10 mL) was stirred at room temperature overnight. Water was added to the reaction mixture, and the obtained crystals were filtrated, washed with water and dried. The obtained crystals were subjected to NH silica gel column chromatography and the title compound (0.80 g, yield 77%) was obtained as colorless crystals from a fraction eluted with ethyl acetate-hexane (1:2, volume ratio). melting point 156-157° C.
