3-(4-Nitro-1H-pyrazol-1-yl)pyridine → Pyridine, 3-(4-aminopyrazol-1-yl)-

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Reaction Steps

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 (water-moist 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.

Provenance & Evidence