A solution of 55 grams (1.1 mol) of hydrazine hydrate in 100 ml of methanol
was cooled in a water bath and stirred while a solution of 48 grams (0.50
mol) of pure γ-pyrone in 100 ml of methanol was added over a period of
about 15 minutes. After the addition was complete, the solution was allowed
to stand at room temperature for about 1 hour, and was placed in a 1 liter
hydrogenation bomb. 25 ml of liquid ammonia were added cautiously with
stirring, followed by about 15 cc of Raney nickel catalyst. The bomb was
charged with hydrogen to 1,800 pounds pressure, heated to 90°C and
agitated. The quantity of hydrogen required to convert the hydrazone into the
desired aminoethylpyrazole was taken up in about 3 hours. The bomb was
cooled and opened, and the contents filtered. The filtrate was evaporated
under reduced pressure to remove the methanol and the residual liquid was
distilled under reduced pressure, whereby there were obtained 44.5 grams
(81% yield) of 3-β-aminoethylpyrazole boiling at 118°-123°C at a pressure of
0.5 mm of Hg.
