1.4 g (4.6 mmol) of 3-methyl-2-[2-(4-cyanophenyl)ethyl]imidazo[1,2-a]pyridin-7-yl-carboxylic acid (prepared from 4-bromo-l-(4-cyanophenyl)-1-penten-3-one and methyl 2-aminopyridine-4-carboxylate analogously to Y. Katsura et al., Chem. Pharm. Bull. 1992, 40, 1424-1438) were suspended in 15 mL of thionyl chloride and heated to boiling for 1 hour until fully dissolved. After the thionyl chloride had been distilled off, the acid chloride was dissolved in 15 mL of pyridine without any further purification and at 0° C. mixed with 1.0 g (5.2 mmol) of N-(2-ethoxycarbonylethyl)aniline. After 1 hour, the solvent was distilled off, the residue was taken up in 30 mL of methylene chloride, washed with 15 mL of 1N hydrochloric acid, and dried with sodium sulfate. After distillation of the solvent and chromatography (silica gel; methylene chloride/ethanol=0 to 2%), a brown oil was obtained. Yield: 1.48 g (64% of theory); Rf value: 0.73 (silica gel; ethyl acetate/ethanol/ammonia=90:10:1).
