Heterocyclization of 2-Acetylcyclopentanone

Various heterocyclic compounds, including pyrazole, pyrimidine, pyrazolo[1,5-a]pyrimidine, and [1,2,4]triazolo[1,5-a]pyrimidine derivatives, as well as the corresponding N-methyl iodides, have been synthe­sized on the basis of 2-acetylcyclopentanone. In some cases, we succeeded in determining the structure of the synthesized compounds by using NOESY spectra. The proposed efficient structure determination method involves N-alkylation of the compounds with methyl iodide, followed by analysis of the NOESY spectra of the resulting iodides.