Azirine

Azirines are three-membered heterocyclic unsaturated (i.e. they contain a double bond) compounds containing a nitrogen atom and related to the saturated analogue aziridine.[1] They are highly reactive yet have been reported in a few natural products such as Dysidazirine. There are two isomers of azirine: 1H-Azirines with a carbon-carbon double bond are not stable and rearrange to the tautomeric 2H-azirine, a compound with a carbon-nitrogen double bond. 2H-Azirines can be considered strained imines and are isolable.

Azirine
Names
IUPAC name
2H-Azirine
Identifiers
3D model (JSmol)
1633516
ChEBI
ChemSpider
  • InChI=1S/C2H3N/c1-2-3-1/h1H,2H2
    Key: NTJMGOWFGQXUDY-UHFFFAOYSA-N
  • C1C=N1
Properties
C2H3N
Molar mass 41.053 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Preparation

2H-Azirine is most often obtained by the thermolysis of vinyl azides.[2] During this reaction, a nitrene is formed as an intermediate. Alternatively, they can be obtained by oxidation of the corresponding aziridine. Azirine can be generated during photolysis of isoxazole.[3] Due to the weak N-O bond, the isoxazole ring tends to collapse under UV irradiation, rearranging to azirine. [4]

Azirine synthesis

Reactions

Photolysis of azirines (under 300 nm) is a very efficient way to generate nitrile ylides. These nitrile ylides are dipolar compounds and can be trapped by a variety of dipolarophiles to yield heterocyclic compounds, e.g. pyrrolines.

The strained ring system also undergoes reactions that favor ring opening and can act as a nucleophile or an electrophile.

An azirine is an intermediate in the Neber rearrangement.

See also
  • Dysidazirine, one of only a few naturally-occurring azirines

References
  1. Teresa M. V. D. Pinho e Melo and Antonio M. d’A. Rocha Gonsalves (2004). "Exploiting 2-Halo-2H-Azirine Chemistry". Current Organic Synthesis. 1 (3): 275–292. doi:10.2174/1570179043366729. Archived from the original on 2006-09-28.
  2. Palacios F, Ochoa de Retana AM, Martinez de Marigorta E, de los Santos JM (2001). "2H-Azirines as synthetic tools in organic chemistry". Eur. J. Org. Chem. 2001 (13): 2401–2414. doi:10.1002/1099-0690(200107)2001:13<2401::AID-EJOC2401>3.0.CO;2-U.
  3. Edwin F. Ullman (1966). "Photochemical Transposition of Ring Atoms in Five-Membered Heterocycles. The Photorearrangement of 3,5-Diphenylisoxazole". J. Am. Chem. Soc. 88 (8): 1844–1845. doi:10.1021/ja00960a066.
  4. Cheng, K.; Qi, J.; Ren, X.; Zhang, J.; Li, H.; Xiao, H.; Wang, R.; Liu, Z.; Meng, L; Ma, N.; Sun, H. (2022). "Developing Isoxazole as a Native Photo-Cross-Linker for Photoaffinity Labeling and Chemoproteomics". Angew. Chem. Int. Ed. 61 (47): e202209947. doi:10.1002/anie.202209947.
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