The hydrazinolysis of heterocyclic compounds. I. 1,4,6-Trimethylpyrimidine-2(1H)-thione and related compounds

The reaction of hydrazine hydrate with 1,4,6-trimethylpyrimidine-2(1H)- thione is shown to follow two major pathways. The first gives 4-amino- 5-hydrazino-1,2,4-triazole-3-thiol and 3,5-dimethyl-pyrazole. The second leads rapidly to 1-amino-4,6-dimethylpyrimidin-2(1H)-one hydrazone, a bright red intermediate compound which is rapidly consumed yielding 3,5-dimethylpyrazole and triaminoguanidine. The N- aminopyrimidine structure assigned to the intermediate is discussed in terms of its spectroscopic and chemical properties. Hydrazinolysis of 1,4,6-trimethylpyrimidin-2(1H)-imine similarly gives the same N- aminopyrimidine as well as 2-methylamino-and 2-hydrazino-4,6- dimethylpyrimidine from the Dimroth rearrangement. 1,4,6- Trimethylpyrimidin-2(1H)-one gives only 3,5-dimethylpyrazole under the same conditions. Mechanisms of the reactions are discussed.