反应详情

温度

-60 °C

Dry tetrahydrofuran (84.6 ml) was added to diisopropylamine (dried with potassium hydroxide, 9.85 g, 0.0973 mole) nder a nitrogen atmosphere. The solution was cooled to -60° C. and thereto was added a 15% solution of n-butyllithium in n-hexane (58.5 ml, 0.0901 mole). After being stirred at 0° C. for 30 minutes, it was cooled to -75° C. A mixture of t-butyl trifluoroacetate (10.80 g, 0.0635 mole), 5-dimethylamino-3-methyl-1,2,4-oxadiazole (5.72 g, 0.0423 mole) and dry tetrahydrofuran (423 ml) was added dropwise to it at -73--75° C. over 1.5 hours. After being stirred at -75° C. for 1 hour, it was allowed to warm to room temperature over 1 hour. It was further heated to 50° C. and stirred for 30 minutes. 1N hydrochloric acid (190 ml) was then added thereto with ice cooling and tetrahydrofuran and n-hexane were distilled off under reudced pressure in a water bath at 40° C. After being extracted with methylene chloride, the extract was concentrated and purified column chromatrography on silica gel to give the crude title compound (8.91 g, crude yield 94.4%). Repeated recrystallizations from benzene gave colorless fine needles, m.p. 126.0°-126.5° C. The structure of this compound was confirmed by IR, NMR and elemental analysis.

1. temperatureit was cooled to -75° C
2. additionwas added dropwise to it at -73--75° C. over 1.5 hours
3. stirringAfter being stirred at -75° C. for 1 hour
4. temperatureto warm to room temperature over 1 hour
5. temperatureIt was further heated to 50° C.
6. stirringstirred for 30 minutes
7. distillationwith ice cooling and tetrahydrofuran and n-hexane were distilled off under reudced pressure in a water bath at 40° C
8. extractionAfter being extracted with methylene chloride
9. concentrationthe extract was concentrated
10. custompurified column chromatrography on silica gel