Unexpected transformations of 3-bromo-5,7-dimethylpyrazolo[1,5-a]pyrimidine in reactions with BuⁿLi

The possibility of generating a carbanion using the reaction of 3-bromo-5,7-dimethylpyrazolo[1,5-a]pyrimidine with BuⁿLi followed by the electrophilic addition was investigated. The obtained results provide evidence for the presence of several reaction centers in the substrate, resulting in the formation of unexpected reaction products. These results offer new prospects for the functionalization of pyrazolo[1,5-a]pyrimidines and allow the preparation of new pharmacologically active derivatives of this series. The structures and purity of all the synthesized compounds were confirmed by ¹H and ¹³C NMR spectroscopy, mass spectrometry, elemental analysis, and X-ray crystallography.