Ammonium Hydroxide → Methyl 1-amino-4-fluoro-1H-pyrrole-2-carboxylate

Participants

Reaction Conditions

Reaction Steps

A mixture of ammonium chloride (6.0 g, 112 mmol) in diethyl ether (220 mL) was cooled to −5° C., and concentrated aq. ammonium hydroxide (9.4 mL) was added dropwise with vigorous stirring. After the addition was complete, commercial grade aq. sodium hypochlorite solution (145 mL) was added via addition funnel at a rate such that the internal temperature was maintained below 0° C. The mixture was then stirred for 15 min, then the layers were separated, and the organic layer was washed with brine and dried over anhyd. calcium chloride. The resulting solution of chloramine was used directly as follows: In a separate flask, containing a solution of methyl 4-fluoro-1H-pyrrole-2-carboxylate (0.98 g, 6.85 mmol) in DMF (15 mL) at 0° C. was added 60% sodium hydride dispersion (0.329 g, 8.22 mmol) and the resulting mixture was allowed to warm to rt and stir for 45 minutes. At this time, a portion of the previously prepared chloramine solution (55 mL) was added via syringe over ˜1 minute. After stirring for an additional 1.5 h at rt, the reaction mixture was quenched by adding sat. aq. Na2S2O3 followed by diluting with water and extracting with diethyl ether (100 mL×2). The combined extracts were dried over anhyd. sodium sulfate, filtered and concentrated under vacuum to afford 0.98 g (91%) of the title compound as a light tan oil. HPLC (condition B): retention time=1.57 min. LCMS (condition B): m/z 159+ve. 1H NMR (400 MHz, MeOD) δ ppm 6.86 (1 H, d), 6.51 (1 H, d, J=2.42 Hz), 3.85 (3 H, s).

Provenance & Evidence