Triethylamine → 4-(2-Fluoro-4-nitrophenoxy)-2-(phenoxycarbonylamino)pyridine

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Reaction Steps

2-Amino-4-(2-fluoro-4-nitrophenoxy)pyridine (2.71 g) was dissolved in tetrahydrofuran (60 ml) under a nitrogen atmosphere, and then triethylamine (2.27 ml) and phenyl chloroformate (2.05 ml) were added dropwise thereto while cooling in an ice water bath, followed by stirring at room temperature for 25 min. The reaction mixture was partitioned between ethyl acetate and a saturated aqueous solution of sodium hydrogencarbonate. The organic layer was washed with a saturated aqueous solution of sodium hydrogencarbonate and brine in this order, and dried over anhydrous sodium sulfate. The solvent was evaporated under a reduced pressure to provide a crude product of 4-(2-fluoro-4-nitrophenoxy)-2-(phenoxycarbonylamino)pyridine (5.00 g). The crude product was dissolved in tetrahydrofuran (50 ml), and then pyrrolidine (3.64 ml) was added at room temperature, followed by stirring for 1 hr. To the reaction mixture was added a saturated aqueous solution of ammonium chloride, followed by extracting with ethyl acetate. The organic layer was washed with a saturated aqueous solution of ammonium chloride and an brine in this order, and dried over anhydrous sodium sulfate. The solvent was evaporated under a reduced pressure to give a residue, which was purified by silica gel column chromatography (eluent; hexane:ethyl acetate=1:2 to 1:4, then ethyl acetate) to provide the titled compound (2.927 g, 78%) as pale brown crystals.

Provenance & Evidence