Carbon Dioxide → 2-(tert-Butoxycarbonylamino)-3-fluoro-benzoic acid

Participants

Reaction Conditions

Reaction Steps

To a solution of tert-butyl 2-fluorophenylcarbamate (44.0 g, 208 mmol) in tetrahydrofuran (660 mL) at −78° C. was added tert-butyllithium in pentane (1.7 M, 306 mL, 2.5 equiv) drop wise. After addition was complete, the reaction was stirred at −78° C. for 30 min. The solution was allowed to gradually reach −20° C. before being recooled to −78° C. and transferred via canula to a slurry of carbon dioxide (excess) and tetrahydrofuran (500 mL). The solution was allowed to slowly warm to room temperature. The reaction mixture was concentrated to remove most of the tetrahydrofuran, and poured into a sep funnel containing water and diethyl ether. The layers were separated, and the aqueous extracted with diethyl ether twice more. The ethereals were discarded. The aqueous was acidified with 5% citric acid, extracted with diethyl ether (3×). The ethereal was dried over magnesium sulfate, and concentrated to give a light yellow solid which was recrystallized from hot toluene to give 37.1 g (70%) as a faint yellow solid. 1H-NMR (CDCl3, 500 MHz) δ 1.50 (s, 9H), 6.25 (bs, 1H), 7.18 (ddd, J=7.9, 7.9, 4.9, 1H), 7.33 (dd, J=9.5, 9.2, 1H), 7.79 (d, J=7.9, 1H), 7.94 (s, 1H). Mass spec.: 278.21 (MNa)+.

Provenance & Evidence