反应详情

To a solution of (Z)—N′-hydroxy-4-methyl-3-nitrobenzimidamide (27) (30 g, 153.71 mmol, 1.00 equiv) and DIEA (39.7 g, 307.18 mmol, 2.00 equiv) in tetrahydrofuran (300 mL) was added dropwise to a solution of triphosgene (18.2 g) in tetrahydrofuran (50 mL). The reaction was stirred for 1 hour at room temperature then heated to reflux for an additional hour. The resulting solution was poured into 500 mL of water and extracted with 3×300 mL of ethyl acetate. The combined organic layers were washed with brine (3×200 mL), dried over anhydrous sodium sulfate, concentrated under vacuum, and purified by flash chromatography (DCM/MeOH=20:1) to afford of 3-(4-methyl-3-nitrophenyl)-1,2,4-oxadiazol-5(4H)-one as a pale yellow solid (106). MS m/z 222.1 (M+1)+.

1. temperaturethen heated
2. temperatureto reflux for an additional hour
3. extractionextracted with 3×300 mL of ethyl acetate
4. washThe combined organic layers were washed with brine (3×200 mL)
5. dry with materialdried over anhydrous sodium sulfate
6. concentrationconcentrated under vacuum
7. custompurified by flash chromatography (DCM/MeOH=20:1)