Trifluoroacetic acid → 3-(1-methyl-5-nitro-1H-pyrazol-3-yl)-1,2,4-oxadiazole

Participants

Reaction Steps

To a solution of N′-hydroxy-1-methyl-5-nitro-1H-pyrazole-3-carboximidamide (1.66 g, 8.97 mmol) and trimethoxymethane (17.6 mL, 161 mmol) in MeOH (2.8 mL) was added 2,2,2-trifluoroacetic acid (0.35 mL, 4.48 mmol) and the mixture was refluxed for about 1 h. The reaction was cooled to ambient temperature and continued to stir for about 16 h. The reaction mixture was concentrated under reduced pressure and the residue was partitioned between DCM (25 mL) and saturated NaHCO3 (10 mL). The aqueous layer was back extracted with DCM (25 mL). The combined organic layers were washed with brine (10 mL), dried over MgSO4, filtered and concentrated under reduced pressure to afford 3-(1-methyl-5-nitro-1H-pyrazol-3-yl)-1,2,4-oxadiazole (1.75 g, 8.97 mmol, 100%, which was used without further purification). LC-MS (Table 1, Method g) Rt=1.56 min, m/z 196 (M+H)+. 1H-NMR (DMSO-d6, Bruker 400 MHz) 9.79 (s, 1H), 7.72 (s, 1H), 4.27 (s, 3H).

Provenance & Evidence