The mixture of 4-tert-butyl-2-{5-[(3-cyano-6-methylindol-1-yl)methyl]benzofuran-2-yl}thiazole (0.19 g), sodium azide (0.32 g) and ammonium chloride (0.30 g) in N,N-dimethylformamide (2 ml) was stirred at 120° C. for 72 hours. After being cooled to room temperature, the reaction mixture was poured into ice-water and the mixture was acidified with diluted hydrochloric acid. The resulting precipitates were collected by filtration and air-dried. The precipitates were subjected to column chromatography on silica gel and eluted with a mixture of dichloromethane and methanol. The fractions containing the objective compound were combined and concentrated under reduced pressure to give 5-{1-{[2-(4-tert-butylthiazol-2-yl)benzofuran-5-yl]methyl}-6-methylindol-3-yl}-1H-tetrazole (0.04 g).
