Lithiation and silylation of 7-amino-3-tert-butyl-4-oxopyrazolo[5,1-c][1,2,4]triazines

The treatment of 7-amino-8-bromo-3-tert-butylpyrazolo[5,1-c][1,2,4]triazin-4(6H)-one with an excess of NaH in THF and AlkLi (Alk = Bun, But) at -97 °C produced disodium (8-lithio-3-tert-butyl-4-oxopyrazolo[5,1-c][1,2,4]triazin-1-id-7-yl)amide unstable under ambient conditions. The chemical properties of the newly synthesized compound were studied. The electrophilic attack occurs at the N(1), C(7)—N, or C(8) ring positions depending on the nature of the electrophilic agent (PhCHO, ButCOCl, TMSBr). The treatment of the N(1)-Boc-protected derivative with BuLi resulted in the C(8)-metalation accompanied by the addition of alkyl at the carbonyl groups or at the N(2) atom. The low-temperature reaction with pivaloyl chloride was studied using deuterium labeling of the amino group, which confirmed the hydrogen atom transfer from the C(7)—NH group to the C(8) position of the heterocycle. The structures of the synthesized compounds were established by IR spectroscopy, 1H, 2H, 13C, and 2D 1H—29Si HMBC NMR spectroscopy, high-resolution mass spectrometry, and single-crystal X-ray dif raction.