Phenyl chloroformate → 5-cyano-3-(2-ethoxypyridin-3-yl)-2-oxo-1-(phenylsulfonyl)-2,3-dihydro-1H-indol-3-yl phenyl carbonate

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Reaction Steps

2.65 g (6.09 mmol) of optically active 3-(2-ethoxypyridin-3-yl)-3-hydroxy-2-oxo-1-(phenylsulfonyl)indoline-5-carbonitrile from example 4B.1 were dissolved in 4.9 ml of pyridine and 6.0 ml of dichloromethane while cooling at 0° C. in ice, the solution becoming brown in color. At this temperature, 1.24 g (7.91 mmol) of phenyl chloroformate were slowly added dropwise. The reaction mixture was stirred in an ice bath for 2 hours. After conversion was complete, the reaction mixture was further diluted with dichloromethane and poured into ice-water. The phases were separated, and the organic phase was washed again with saturated sodium chloride solution (1×) and water (1×). The solvent was evaporated in vacuo, and excess pyridine was removed by codistillation with toluene. 50 ml of diisopropyl ether were added to precipitate the product, and, after the solid had been filtered off with suction and washed with diisopropyl ether, a total of 2.16 g (3.89 mmol, 64%) of the optically active 5-cyano-3-(2-ethoxypyridin-3-yl)-2-oxo-1-(phenylsulfonyl)-2,3-dihydro-1H-indol-3-yl phenyl carbonate was isolated. Further purification of the mother liquor by normal-phase chromatography with dichloromethane as mobile phase resulted in 800 mg of the optically active 5-cyano-3-(2-ethoxypyridin-3-yl)-2-oxo-1-(phenylsulfonyl)-2,3-dihydro-1H-indol-3-ylphenyl carbonate.

Provenance & Evidence