4-Fluorobenzaldehyde → 5-Fluoro-6-(4-fluoro-benzylamino)-1,3-dihydro-indol-2-one

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Reaction Steps

6-Amino-5-fluoro-1,3-dihydro-indol-2-one 3d (2.26 g, 13.6 mmol) was dissolved in 40 ml of ethanol under stirring at room temperature, the resulting solution was cooled down to 0° C. in an ice-water bath, and added with 4-fluoro-benzaldehyde (1.5 ml, 13.6 mmol) to the solution. Upon completion of the addition, the resulting solution was stirred for 1 hour at room temperature, added with sodium borohydride (1.08 g, 28.5 mmol) and heated to reflux for 18 hours. After thin lay chromatography showed the disappearance of starting materials, the reaction mixture was naturally cooled down to room temperature, added with ice water and lots of precipitates were formed, filtered and washed with water (50 ml×3). The residue was purified by silica gel column chromatography to obtain the title compound 5-fluoro-6-(4-fluoro-benzylamino)-1,3-dihydro-indol-2-one 3e (1.67 g, yield 45%) as a white solid.

Provenance & Evidence