title: Selective (15)N-labeling and analysis of (13)C-(15)N J couplings as an effective tool for studying the structure and azide-tetrazole equilibrium in a series of tetrazolo[1,5-b][1,2,4]triazines and tetrazolo[1,5-a]pyrimidines.
abstract: Two general methods for the selective incorporation of an (15)N-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 (15)N-labeled nitrous acid, and the second approach was based on fusion of the azine ring to [2-(15)N]-5-aminotetrazole. The synthesized compounds were studied by (1)H, (13)C, and (15)N 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 (15)N-label led to the appearance of (13)C-(15)N J coupling constants (J(CN)), which can be measured easily using either 1D (13)C spectra with selective (15)N decoupling or with amplitude modulated 1D (13)C spin-echo experiments with selective inversion of the (15)N nuclei. The observed J(CN) 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 J(CN) patterns and (15)N chemical shifts was found to be the most efficient way to study the azido-tetrazole equilibrium.
authors.affiliation: Yeltsin Ural Federal University, 19 Mira Street, 620002 Ekaterinburg, Russia. deevsl@yandex.ru
authors.forename: Sergey L
authors.initials: SL
authors.lastname: Deev
authors.forename: Zakhar O
authors.initials: ZO
authors.lastname: Shenkarev
authors.forename: Tatyana S
authors.initials: TS
authors.lastname: Shestakova
authors.forename: Oleg N
authors.initials: ON
authors.lastname: Chupakhin
authors.forename: Vladimir L
authors.initials: VL
authors.lastname: Rusinov
authors.forename: Alexander S
authors.initials: AS
authors.lastname: Arseniev
mesh_terms: D001386:Azides / Q000737:chemistry*; D002247:Carbon Isotopes / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D009587:Nitrogen Isotopes / Q000737:chemistry*; D011743:Pyrimidines / Q000737:chemistry*; D014227:Triazines / Q000737:chemistry*
chemical_list: D001386:Azides; D002247:Carbon Isotopes; D009587:Nitrogen Isotopes; D011743:Pyrimidines; D014227:Triazines