Phenyl chloroformate → Phenyl 5-cyano-3-(2-ethoxypyridin-3-yl)-6-fluoro-2-oxo-3-phenoxycarbonyloxy-2,3-dihydroindole-1-carboxylate

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Reaction Steps

330 μl (2.62 mmol) of phenyl chloroformate were slowly added dropwise to a solution, cooled to 0° C., of 342 mg (0.66 mmol; 60% purity) of 3-(2-ethoxypyridin-3-yl)-6-fluoro-3-hydroxy-2-oxo-2,3-dihydro-1H-indole-5-carbonitrile (mother liquor from example a.2) in 8 ml of pyridine, and the reaction mixture was stirred at room temperature overnight. The reaction mixture was diluted with dichloromethane and extracted with water. The organic phase was washed with water and saturated sodium chloride solution, dried over magnesium sulfate and concentrated under reduced pressure. The residue was purified by chromatography on silica gel (Redisep cartridge, mobile phase gradient from 0 to 5% methanol in dichloromethane). 291 mg of the title compound were obtained.

Provenance & Evidence