Abstract3‐Alkylamino, 3‐alkoxy or 3‐alkylthioacrylonitriles whose leaving group is incorporated in a saturated heterocyclic ring are 1,3‐bifunctional electrophiles. They react with hydrazine hydrate at the cyano group by addition as well as at position 3 by opening the saturated ring. By this ring transformation new 5‐aminopyrazoles are formed which are additionally substituted by an ω‐functionalized alkyl chain in position 3.