¹⁵N NMR spectra and reactivity of 2,4,6‐triazidopyridines, 2,4,6‐triazidopyrimidine and 2,4,6‐triazido‐s‐triazine

Abstract

2,4,6-Triazido-s-triazine, 2,4,6-triazidopyrimidine and six different 2,4,6-triazidopyridines were studied by (15)N NMR spectroscopy. The assignment of signals in the spectra was performed using the gauge-independent atomic orbital (GIAO)-Tao-Perdew-Staroverov-Scuseria exchange-correlation functional (TPSS)h/6-311+G(d,p) calculations on the M06-2X/6-311+G(d,p) optimized molecular geometries. The Truhlar and coworkers' continuum solvation model called SMD was applied to treat solvent effects. With this approach, the root mean square error in estimations of the (15)N chemical shifts for the azido groups was just 1.9 ppm. It was shown that the different reactivity of the α- and γ-azido groups in pyridines correlates well with the chemical shifts of the Nα signals of these groups. Of two nonequivalent azido groups of azines, the azido group with the most shielded Nα signal is the most electron-deficient and reactive toward electron-rich reagents. By contrast, the azido group of azines with the most deshielded Nα signal is the most reactive toward electron-poor reagents.

Multistep Thermolysis Mechanisms of Azido-s-triazine Derivatives and Kinetic Compensation Effects for the Rate-Limiting Processes

“…In particular, incorporation of a nitrogen linkage has been postulated to decrease sensitivity and improve energy 7 . The substitution of azido with amino group for TAT could decrease its 2 instance, their polyazido products have higher density, heats of formation, as well as the melting point 17 . Such compounds include 4,4',6,6'-tetra(azido)hydrazo-1,3,5-triazine (TAHT) and 4,4',6,6'-tetra(azido)azo-1,3,5-triazine (TAAT).…”

13C and 15N NMR spectra of high‐energy polyazidocyanopyridines

“…These sets can be differentiated by the signal intensity that increases in the order N α < N γ < N β . It has been shown that the GIAO‐TPSSh/M06‐2X calculations allow one to correctly assign the signals in each of the three sets even when the differences in the chemical shifts of the signals are smaller than the overall MAD between the experimental and calculated δ N values. The correct assignment is possible owing to the fact that the calculation errors of δ N values for a given type of the azido group atoms (N α , N β or N γ ) are mostly systematic; in the case of (hetero)aromatic azides, the systematic error varies with the nature of the (hetero)aromatic core.…”

“…Thus, the C‐2/C‐6 signal of triazide 1 and the C‐4 signal of 2,4,6‐triazidopyrimidine are manifested at 160.1 and 161.2 ppm, respectively. The 15 N NMR spectrum of triazide 1 exhibits the N α , N β and N γ signals of the α‐azido groups at −260.4, −144.6 and −132.0 ppm, whereas the corresponding signals of the 2‐azido group of 2,4,6‐triazidopyrimidine are observed at −262.7, −140.0 and −135.1 ppm. Among all known 2,4,6‐triazidopyridines, compound 1 shows the most shielded signal of the pyridine ring nitrogen ( δ N = −135.7 ppm), the nearest to the signal of the pyrimidine ring nitrogen of 2,4,6‐triazidopyrimidine ( δ N = −145.6 ppm) …”

“…The 13 C and 15 N chemical shifts were calculated by the gauge‐independent atomic orbital (GIAO) method with the Tao–Perdew–Staroverov–Scuseria hybrid (TPSSh) functional . This approach has been successfully used to predict the 13 C and 15 N chemical shifts of many heteroaromatic azides in CDCl 3 and DMSO‐ d 6 …”

Chemoselective Staudinger‐Phosphite Reaction on the Azido Groups of 2,4,6‐Triazido‐3,5‐dibromopyridine

“…The most electron‐deficient azido groups of organic polyazides have the lowest total negative charge of the N 3 − moiety and display the most shielded N α signal in 15 N NMR spectra . Thus, the most electron‐deficient azido group of triazide 1 is the group located in the γ‐position of the pyridine ring . This group selectively reacts with electron‐rich dipolarophiles, adds triphenylphosphine, and is reduced till the amino group (Scheme ).…”