Conformational properties and photochemistry of tetrazolylpyridines in low temperature matrices. Spectroscopic evidence for the photochemical carbon-to-nitrogen rearrangement

Pagacz-Kostrzewa, Magdalena; Krupa, Justyna; Olbert‐Majkut, Adriana; Podruczna, M.; Bronisz, Robert; Wierzejewska, Maria

doi:10.1016/j.tet.2011.08.055

Cited by 14 publications

(12 citation statements)

References 31 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

Section: ■ Results and Discussionmentioning

confidence: 85%

“…The validity of the mechanism in Scheme 4 was supported by 13 C-labeling. In the mass spectrum of 5-13 C-tetrazole 12a- 13 C, m/z 92 is the base peak (100%), proving that 13 C is retained, i.e., H 13 CN has not been eliminated (Scheme 5 and Table S1). The resulting phenylnitrene ion 9a-13 C •+ is expected to be labeled primarily in the ortho position following the previously established mechanisms of rearrangement of 2pyridylcarbene 4 and its radical cation 8 (see Scheme 6).…”

Section: ■ Results and Discussionmentioning

confidence: 85%

“…Substantial energy differences were also found for the electronic states of phenylnitrene radical cation. 8 A reason why the 5-tetrazolyl-α-azines behave so differently can be sought in the fact that, thanks to an intramolecular hydrogen bond, the 1H-tautomers of 5-tetrazolyl-α-azines are by far the most stable in the gas phase, accounting for 98−99% of the ensemble of tautomers, 13 whereas for other 5aryltetrazoles the 2H-tautomers (1) dominate in the gas phase. 8 Thus, the intramolecularly H-bonded tetrazole 12a •+ (Scheme 4) lies ca.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…In contrast, in the spectrum of the similarly labeled 4-pyridyl derivative 12c-13 C, N 2 + H 13 CN are eliminated, yielding the 4pyridylnitrene ion 18c •+ (Scheme 5 and Figures S1−S3, Supporting Information). Although 9a-13 C •+ and 18c •+ have the same mass (m/z 92), high-resolution measurements of the unlabeled ions confirmed their different compositions, C 6 H 5 N and C 5 H 4 N 2 , respectively.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…The spectra in Figure 5 were recorded on a Hewlett-Packard GC 5890-MS 5970 instrument. The linked scans, high-resolution measurements, and comparative scans of 13 C-labeled and unlabeled compounds were performed on a Thermo-Fischer DFS inverse geometry (BE) double-focusing, high-resolution instrument. CID experiments were performed using He as a collision gas in the first field-free region of the spectrometer and a 5 keV accelerating voltage.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

See 4 more Smart Citations

Heteroarylcarbene–Arylnitrene Radical Cation Isomerizations

et al. 2019

View full text Add to dashboard Cite

5-Phenyltetrazole 1e is an important source of phenylnitrene or the phenylnitrene radical cation (m/z 91) under thermal, photochemical, and electron impact conditions. Similarly, 3-or 4-(5-tetrazolyl)pyridines 12b,c yield pyridylnitrene radical cations 9a •+ (m/z 92) upon electron impact. In contrast, 2-(5-tetrazolyl)pyridine 12a •+ generates 2-pyridyldiazomethane 24 •+ and 2-pyridylcarbene 26 •+ radical cations (m/z 119 and 91) upon electron impact. The 2-pyridylcarbene radical cation undergoes a carbene−nitrene rearrangement to yield the phenylnitrene radical cation. Calculations at the B3LYP/6-311G(d,p) level have revealed facile H-transfer from the tetrazole to the pyridine ring in 2-(5-tetrazolyl)pyridine, 12a •+ → 21 •+ , taking place in the radical cations. Subsequent losses of N 2 generate the pyridinium diazomethyl radical 22 •+ or pyridinium-2-carbyne 23 •+ . These two ions can isomerize to 2-pyridyldiazomethane 24 •+ and 2pyridylcarbene 26 •+ , the latter rearranging to the phenylnitrene radical cations 9a •+ . 13 C-labeling of the tetrazole rings confirmed that 2-(5-tetrazolyl)pyridine 12a generates 2-pyridylcarbene/phenylnitrene radical cations retaining the 13 C label, but 4-(5tetrazolyl)pyridine 12c generates 4-pyridylnitrene 18c •+ , which has lost the 13 C label. 2-Pyridylcarbene/phenylnitrene radical cations (m/z 91) also constitute the base peak in the mass spectrum of 1,2,3-triazolo[1,5-a]pyridine 34. Similarly, 4pyridylnitrene radical cation 18c •+ or its isomers (m/z 92) is obtained from 1,2,3-triazolo[1,5-a]pyrazine 36. Several other αheteroaryltetrazoles behave in the same way as 2-(5-tetrazolyl)pyridine, yielding heteroarylcarbene/arylnitrene radical cations in the mass spectrometer, and this was confirmed by 13 C-labeling in the case of 1-(5-tetrazolyl)isoquinoline 42-13 C. In general, 5aryltetrazoles generate arylnitrene radical cations under electron impact, but α-heteroaryltetrazoles generate α-heteroarylcarbene radical cations.

show abstract