Carbon Dioxide → 6-((tert-Butoxycarbonyl)amino)-2,3-difluorobenzoic acid

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Reaction Steps

400 ml (600 mmol) of tert.butyllithium (1.5M in pentane) were added dropwise within 1 hour to a solution, cooled to -70°, of 57.2 g (250 mmol) of N-(tert.butoxycarbonyl)-3,4-difluoroaniline in 500 ml of tetrahydrofuran. Subsequently, 160 g of dry ice were added in small portions to the yellow suspension, the mixture was left to warm to 0° and 400 ml of water were added dropwise. The tetrahydrofuran and the pentane were distilled off and the aqueous phase was washed twice with ether and subsequently adjusted to pH=1 with conc. hydrochloric acid. The acidic aqueous phase was extracted three times with methylene chloride; the organic phase was dried over sodium sulfate, filtered and evaporated. The beige solid obtained was recrystallized from ethylene chloride and there were obtained 52 g (76%) of 2-(tert.-butoxycarbonyl)amino-5,6-difluorobenzoic acid as colourless needles of m.p. 159.5°-160.5°.

Provenance & Evidence