S 45 Selective (15)N-Labeling and Analysis of (13)C(15)N J Couplings as an Effective Tool for Studying the Structure and AzideTetrazole Equilibrium in a Series of Tetrazolo[1,5-b][1,2,4]triazines and Tetrazolo[1,5-a]pyrimidines [Text] / S. L. Deev, Z. O. Shenkarev, T. S. Shestakova, O. N. Chupakhin, V. L. Rusinov, A. S. Arseniev // Journal of Organic Chemistry. - 2010. - Vol. 75, № 24. - P8487-8497 Рубрики: ХИМИЧЕСКИЕ НАУКИ Аннотация: Two general methods for the selective incorporation of an 15N-label in the azole ring of tetrazolo[1,5-b][1,2,4]triazines and tetrazolo[1,5-a]pyrimidines were developed. The first approach included treatment of azinylhydrazides with 15N-labeled nitrous acid, and the second approach was based on fusion of the azine ring to [2-15N]-5-aminotetrazole. The synthesized compounds were studied by 1H, 13C, and 15N NMR spectroscopy in both DMSO and TFA solution, in which the azide tetrazole equilibrium is shifted to tetrazole and azide forms, respectively. Incorporation of the 15N-label led to the appearance of 13C 15N J coupling constants (JCN), which can be measured easily using either 1D 13C spectra with selective 15N decoupling or with amplitude modulated 1D 13C spin echo experiments with selective inversion of the 15N nuclei. The observed JCN patterns permit unambiguous determination of the type of fusion between the azole and azine rings in tetrazolo[1,5-b][1,2,4]triazine derivatives. Joint analysis of JCN patterns and 15N chemical shifts was found to be the most efficient way to study the azido-tetrazole equilibrium \\\\Expert2\\nbo\\Journal of Organic Chemistry\\2010, v.75, p.8487.pdf |