A mixture of N-{2-[5-(2-cyanoethyl)-1,3-thiazol-2-yl]-1H-indol-7-yl}-N-methylthiophene-2-sulfonamide (0.30 g), dibutyltin oxide (35 mg), trimethylsilylazide (0.74 mL) and tetrahydrofuran (10 mL) was heated under reflux for 3 days. The reaction mixture was concentrated. The residue was subjected to silica gel column chromatography, and the title compound (0.22 g, yield 67%) was obtained as yellow crystals from a fraction eluted with tetrahydrofuran-methanol (9:1, volume ratio). The crystals were recrystallized from ethyl acetate. melting point 211-212° C.
