Phenylnitrene, phenylcarbene, and pyridylcarbenes. Rearrangements to cyanocyclopentadiene and fulvenallene.

Kvaskoff, David, Lüerssen, Holger, Bednarek, Pawel and Wentrup, Curt (2014) Phenylnitrene, phenylcarbene, and pyridylcarbenes. Rearrangements to cyanocyclopentadiene and fulvenallene.. Journal of the American Chemical Society, 136 43: 15203-15214. doi:10.1021/ja506151p

Author Kvaskoff, David
Lüerssen, Holger
Bednarek, Pawel
Wentrup, Curt
Title Phenylnitrene, phenylcarbene, and pyridylcarbenes. Rearrangements to cyanocyclopentadiene and fulvenallene.
Journal name Journal of the American Chemical Society   Check publisher's open access policy
ISSN 1520-5126
Publication date 2014-10-29
Year available 2014
Sub-type Article (original research)
DOI 10.1021/ja506151p
Volume 136
Issue 43
Start page 15203
End page 15214
Total pages 12
Place of publication Washington, DC, United States
Publisher American Chemical Society
Collection year 2015
Language eng
Formatted abstract
Flash vacuum thermolysis (FVT) of phenyl azide 29 as well as precursors of 2-pyridylcarbene 34 and 4-pyridylcarbene 25 affords phenylnitrene 30 (labeled or unlabeled), as revealed by matrix isolation electron spin resonance spectroscopy. FVT of 1-13C-phenyl azide 29 affords 1-cyanocyclopentadiene (cpCN) 32, which is exclusively labeled on the CN carbon, thus demonstrating direct ring contraction in phenylnitrene 30 without the intervention of cycloperambulation and 1,3-H shifts. However, the cpCN obtained by rearrangement of pyridyl-2-(13C-carbene) 34 carries 13C label on all carbon atoms, including the CN carbon. Calculations at the B3LYP/6-31G* level and in part at the CASSCF/6-31G* and CASPT2/cc-pVDZ//CASSCF(8,8)/cc-pVDZ levels support a new mechanism whereby 2-pyridylcarbene rearranges in part via 1-azacyclohepta-1,2,4,6-tetraene 36 to phenylnitrene, which then undergoes direct ring contraction to cpCN. Another portion of 2-pyridylcarbene undergoes ring expansion to 4-azacyclohepta-1,2,4,6-tetraene 42, which then by trans-annular cyclization affords 6-azabicyclo[3.2.0]cyclohepta-1,3,5-triene 43. Further rearrangement of 43 via the spiroazirine 44 and biradical/vinylnitrene 45 affords cpCN with the label on the CN group. An analogous mechanisms accounts for the labeling pattern in fulvenallene 60 formed by ring contraction of 1-13C-phenylcarbene 59 in the FVT of 1-13C-phenyldiazomethane 58.
Keyword Flash vacuum thermolysis (FVT)
Phenylnitrene 30
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: Official 2015 Collection
School of Chemistry and Molecular Biosciences
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Created: Fri, 24 Oct 2014, 09:25:33 EST by Mrs Louise Nimwegen on behalf of School of Chemistry & Molecular Biosciences