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98.9 g (520 mmol) of 3-(4-nitro-1H-pyrazol-1-yl)pyridine were dissolved in 1.3 l of warm dioxane, and twice evacuated and filled with argon. 500 ml of ammonia in methanol (˜7 mol/l) were added and the mixture was again twice evacuated and filled with argon. 27.5 g of Raney nickel (watermoist slurry) were added and the mixture was twice evacuated and filled with argon, and three times more evacuated and filled with hydrogen. The suspension was stirred under a hydrogen balloon overnight. A further 32 g of Raney nickel were added and the mixture was stirred under a hydrogen atmosphere for a further 24 hours. The hydrogen atmosphere was exchanged for argon, and the reaction mixture was filtered through Hyflo and washed with 500 ml of dioxane. The filtrate was concentrated on a rotary evaporator and dried under HV (high vacuum). The brown oil obtained crystallized in a refrigerator. The crude product was dissolved in 750 ml of ethyl acetate, 20 g of activated carbon were added and the mixture was stirred at 50° C. for 30 minutes. After filtration, activated carbon was added again and the mixture was again stirred at 50° C. for 30 minutes. Filtration through Hyflo was followed by concentration to approx. 250 g. 350 ml of diisopropyl ether were added and the mixture was stirred at room temperature. The solid was filtered off and washed with diisopropyl ether and heptane. Drying on a rotary evaporator gave a beige solid.

1. customtwice evacuated
2. additionfilled with argon
3. addition500 ml of ammonia in methanol (˜7 mol/l) were added
4. customthe mixture was again twice evacuated
5. additionfilled with argon
6. addition27.5 g of Raney nickel (watermoist slurry) were added
7. customthe mixture was twice evacuated
8. additionfilled with argon, and three times
9. custommore evacuated
10. additionfilled with hydrogen
11. additionA further 32 g of Raney nickel were added
12. stirringthe mixture was stirred under a hydrogen atmosphere for a further 24 hours
13. filtrationthe reaction mixture was filtered through Hyflo
14. washwashed with 500 ml of dioxane
15. concentrationThe filtrate was concentrated on a rotary evaporator
16. customdried under HV (high vacuum)
17. customThe brown oil obtained
18. customcrystallized in a refrigerator
19. dissolutionThe crude product was dissolved in 750 ml of ethyl acetate
20. addition20 g of activated carbon were added
21. stirringthe mixture was stirred at 50° C. for 30 minutes
22. filtrationAfter filtration, activated carbon
23. additionwas added again
24. stirringthe mixture was again stirred at 50° C. for 30 minutes
25. filtrationFiltration through Hyflo
26. concentrationwas followed by concentration to approx. 250 g
27. addition350 ml of diisopropyl ether were added
28. stirringthe mixture was stirred at room temperature
29. filtrationThe solid was filtered off
30. washwashed with diisopropyl ether and heptane
31. customDrying on a rotary evaporator
32. customgave a beige solid