反应详情

1-Benzyl-3-(5-carboxy-2-furyl)indazole, potassium salt: 70.26 g (0.3 mol) of 5-(2-fluorobenzoyl)furan-2-carboxylic acid were initially charged in 350 ml of methanol, 109.95 g (0.9 mol) of benzylhydrazine were added and the mixture was, after addition of 8 ml of glacial acetic acid, heated under reflux for 6 h. For work-up, the mixture was concentrated using a rotary evaporator, the residue was taken up in 2 N aqueous sodium hydroxide solution and extracted with ethyl acetate. The aqueous phase was acidified with 2 N hydrochloric acid and extracted with ethyl acetate. The residue that remained after drying and concentration using a rotary evaporator was recrystallized from ethyl acetate/n-hexane. The 68.3 g (0.20 mol) of 5-(2-fluorobenzoyl)furan-2-carboxylic acid benzylhydrazone (m.p.: 147° C. (decomp.)) obtained in this manner were dissolved in 400 ml of DMF, 45.38 g (0.40 mol) of potassium tert-butoxide were introduced and the mixture was heated under reflux for 30 minutes. The precipitate was filtered off with suction, washed with dichloromethane and recrystallized from ethanol/water (95:5). This gave 57.7 g (54%) of the title compound. The corresponding cyclization of the precursor which was still contained in the mother liquor gave 25.9 g of product. m.p.: >300° C.

1. temperatureheated
2. temperatureunder reflux for 6 h
3. concentrationFor work-up, the mixture was concentrated
4. customa rotary evaporator
5. extractionextracted with ethyl acetate
6. extractionextracted with ethyl acetate
7. customafter drying
8. concentrationconcentration
9. customa rotary evaporator
10. customwas recrystallized from ethyl acetate/n-hexane