Ring contraction of a 5‐acetylpyrimidine into pyrazoles by the action of substituted hydrazines in acidic medium

We have found previously that two 5‐acetyl‐4‐methylpyrimidines could be transformed by aminoguanidine hydrochloride into 4‐acetyl‐1‐amidino‐3‐methylpyrazolyl amidinohydrazone dihydrochloride. This reaction beside the fact that it led to a molecule closely related to the antitumor drug M.G.B.G. pointed out to a new possibility of ring contraction of pyrimidines into pyrazoles. We attempted therefore to study the possibility of extending this transformation to other substituted hydrazines and to define more accurately the conditions of this reaction as well as to prepare new potential anticancer drugs.