Pyrimidine Derivatives and Related Compounds. Part 45. Synthesis of 4-Allophanoylpyrazoles via a Pyrimidine-to-pyrazole Ring Transformation
Reaction of the 5-formyluracil derivatives (1a-f) with hydrazines in the presence of acetic acid produced a ring contraction to give the corresponding 4-allophanoylpyrazoles (2a-h).Further treatment of these pyrazoles (2a-h) with sodium methoxide afforded methyl pyrazole-4-carboxylate (3a).Conceivable mechanisms for the present pyrimidine-to-pyrazole transformation were discussed.
A RING TRANSFORMATION OF URACIL INTO THE PYRAZOLE RING SYSTEM. REINVESTIGATION OF THE REACTION OF 5-FORMYLURACILS WITH HYDRAZINES
Cheng et al. reported that the reaction of 5-formyluracil (1a) with hydrazine hydrate in the presence of acetic acid gave 4-ureidomethylene-1H-5-pyrazolone (3).However, results of our reinvestigation revealed that the Cheng's compound (3) should be 4-urei