反应详情

Under an atmosphere of argon, 5.49 g (83.2 mmol, 85% pure) of potassium hydroxide (powder) are initially charged in 110 ml of dimethyl sulphoxide, 6.43 g (27.5 mmol) of ethyl 5-nitro-1H-indole-2-carboxylate (A. Guy, J.-P. Guetté, Synthesis 1980, 222–223) are added at RT and the mixture is stirred for 30 min. With ice-cooling, at an internal temperature of 5–10° C., 2,6-difluorobenzyl chloride (10.0 g, 61.5 mmol) is then added dropwise over a period of 15 min, and the mixture is stirred at RT for 16 h. For work-up, the mixture is poured into 500 ml of water and acidified with dil. hydrochloric acid and the precipitated solid is filtered off with suction and pre-purified chromatographically on silica gel 60 (mobile phase gradient dichloromethane→dichloromethane-methanol 3:1). The resulting product is recrystallized from ethanol. This gives 4.33 g (47% of theory) of a pale-yellow crystalline solid.

1. customGuetté, Synthesis 1980, 222–223)
2. additionare added at RT
3. additionis then added dropwise over a period of 15 min
4. stirringthe mixture is stirred at RT for 16 h
5. filtrationthe precipitated solid is filtered off with suction
6. custompre-purified chromatographically on silica gel 60 (mobile phase gradient dichloromethane→dichloromethane-methanol 3:1)
7. customThe resulting product is recrystallized from ethanol