Di-tert-butyl azodicarboxylate → (S)-3-methoxy-1-(1-methylpyrrolidin-3-yl)-4-nitro-1H-pyrazole

Participants

Reaction Steps

To a suspension of 3-methoxy-4-nitro-1H-pyrazole (2.00 g, 14.0 mmol, 1.00 eq), (R)-1-methyl-pyrrolidin-3-ol (1.56 g, 15.4 mmol, 1.10 eq), and polystyrene bound triphenylphosphine (6.53 g, 19.6 mmol, 1.40 eq, 3 mmol/gram) in THF (140 mL) was added a solution of di-tert-butyl azodicarboxylate (4.51 g, 19.6 mmol, 1.40 eq) in THF (25 mL) in a drop-wise manner over 5 min. The reaction mixture was allowed to stir for 18 hr. The reaction mixture was then diluted with EtOAc (100 mL), filtered and the filtrate concentrated. The crude reaction mixture was purified via flash chromatography on silica gel eluting with a gradient of 50-100% EtOAc in heptane then to 10% 7 N methanolic ammonia/EtOAc to give the title compound (2.39 g, 80% yield) as a white solid. 1H NMR (400 MHz, DMSO-d6) δ ppm 8.69 (s, 1H), 4.84-4.72 (m, 1H), 3.94 (s, 3H), 2.86-2.75 (m, 2H), 2.72 (dd, J=7.0, 10.0 Hz, 1H), 2.40 (dt, J=6.2, 8.4 Hz, 1H), 2.36-2.29 (m, 1H), 2.28 (s, 3H), 2.16-2.06 (m, 1H). m/z (APCI+) for C9H15N4O3 227.2 (M+H)+.

Provenance & Evidence