Recyclization of a Pyrimidinium Salt as a Synthetic Approach to Novel Nitrogenous Heterocycles

The recyclization of 2-(ethoxycarbonyl)methyl-1,4,6-trimethylpyrimidin-1-ium iodide under the action of ethylhydrazine and (4,6-dimethylpyrimidin-2-yl)acetic acid hydrazide, 1-ethyl-3-(ethoxycarbonyl)methyl-5-methyl-1,2,4-triazole and 5,7-dimethyl-3-(ethoxycarbonyl)-2-(4',6'-dimethylyrimidin- 2'-yl-)methylpyrazolo[1,5-a]pyrimidine were synthesized, respectively. Alkylation of 1-ethyl-3-ethoxycarbonylmethyl-5-methyl-1,2,4-triazole with various alkyl iodides yielded the corresponding N-alkyltriazolium salts, and reactions of triazolylacetic acid esters yielded their hydrazides. Based on the nuclear Overhauser effect (NOE), it was clearly demonstrated that alkylation occurs at the N-4 nitrogen atom of the triazole ring.