A mixture of (5-chloro-2-methylindol-1-yl)acetic acid methyl ester (0.50 g), 2-(pyrimidine-5-sulfonyl)benzaldehyde (0.35 g) and dichloroethane (50 mL) at −70° C. was treated sequentially with triethylsilane (2.5 g) and trifluoroacetic acid (0.81 g), and the resulting mixture was stirred at −70° C. for 1 hour. The mixture was slowly warmed to room temperature and stirred at this temperature for 18 hours. The mixture was diluted with saturated aqueous sodium hydrogen carbonate solution and the phases were separated. The organic phase was concentrated under reduced pressure and the residue was purified by column chromatography on silica gel, eluting with a mixture of cyclohexane and ethyl acetate (4:1 to 2:3 by volume) to afford the title compound as a brown oil (0.12 g).
