反应详情

To a mixture of N′-hydroxy-2-(4-nitrophenyl)ethanimidamide (6.17 g) and N,N-dimethylacetamide (50 mL) was added propionyl chloride (3.22 g) at room temperature. The reaction mixture was stirred at room temperature for 2 hrs. Water was poured into the reaction mixture and the mixture was extracted with ethyl acetate. The organic layer was washed with saturated brine, dried over anhydrous magnesium sulfate and concentrated. A mixture of the obtained residue and xylene (200 mL) was heated under reflux for 15 hrs. with azeotropic dehydration. The reaction mixture was concentrated and the obtained residue was subjected to silica gel column chromatography to give 5-ethyl-3-(4-nitrobenzyl)-1,2,4-oxadiazole as brown crystals (4.40 g, yield 60%) from a fraction eluted with hexane-ethyl acetate (3:1-2:1, v/v). Recrystallization thereof from ethyl acetate-hexane gave pale-yellow prism crystals. melting point: 69-70° C.

1. extractionthe mixture was extracted with ethyl acetate
2. washThe organic layer was washed with saturated brine
3. dry with materialdried over anhydrous magnesium sulfate
4. concentrationconcentrated
5. additionA mixture of the obtained residue and xylene (200 mL)
6. temperaturewas heated
7. temperatureunder reflux for 15 hrs
8. concentrationThe reaction mixture was concentrated