تفاعل #53677
ord-8579ef7fd7f44d7fa171ae257a9d3fa3
معادلة التفاعل
الكواشف
ظروف التفاعل
المعالجة
- 1درجة الحرارةis maintained at −20° C. for one hour
- 2تركيزThe reaction medium is concentrated by evaporation under reduced pressure
- 3أخرىthe residue thus obtained
- 4أخرىThe solution thus obtained
- 5درجة الحرارةis cooled to 0° C.
- 6أخرىis brought slowly to a temperature in the region of 25° C.
- 7درجة الحرارةto reflux for 3 hours
- 8أخرىagain brought to a temperature in the region of 0° C
- 9workup.ADDITIONare added dropwise
- 10درجة الحرارةto reflux for one hour
- 11أخرىis brought to a temperature in the region of 25° C.
- 12تركيزconcentrated under reduced pressure by evaporation
- 13أخرىThe residue thus obtained
- 14استخلاصextracted with 3 times 100 ml of ethyl acetate
- 15تجفيفdried over magnesium sulfate
- 16ترشيحfiltered
- 17تركيزconcentrated by evaporation under reduced pressure
- 18أخرىThe residue thus obtained
- 19أخرىis purified by chromatography on a silica column with a dichloromethane/methanol (99/1 by volume) mixture as eluent
الإجراء التجريبي
3-Methylamino-5-nitro-1H-indazole can be obtained in the following way: 2.4 ml of formic acid are added dropwise to a solution, cooled to 0° C., of 5 ml of acetic anhydride. The solution is then brought to 50° C. for one hour and then again cooled to −20° C. 3.5 g of 3-amino-5-nitro-1H-indazole in solution in 150 ml of tetrahydrofuran are then added and stirring is maintained at −20° C. for one hour. The reaction medium is concentrated by evaporation under reduced pressure and the residue thus obtained is dissolved in 50 ml of tetrahydrofuran. The solution thus obtained is cooled to 0° C. and 25 ml of borane-dimethyl sulfide complex (2M solution in tetrahydrofuran) are added dropwise. The reaction medium is brought slowly to a temperature in the region of 25° C. and then brought to reflux for 3 hours and again brought to a temperature in the region of 0° C. After addition of 100 ml of methanol, 50 ml of 3M hydrochloric methanol are added dropwise and the mixture is brought to reflux for one hour. The medium is brought to a temperature in the region of 25° C. and concentrated under reduced pressure by evaporation. The residue thus obtained is taken up with 100 ml of water and neutralized to pH 11 by addition of aqueous ammonia, and then extracted with 3 times 100 ml of ethyl acetate. The organic phases are pooled, dried over magnesium sulfate, filtered and concentrated by evaporation under reduced pressure. The residue thus obtained is purified by chromatography on a silica column with a dichloromethane/methanol (99/1 by volume) mixture as eluent. 1.1 g of 3-methylamino-5-nitro-1H-indazole are thus obtained in the form of an orange solid melting at 252° C.