Azirine is three-membered heterocyclic unsaturated (i.e. it contain a double bond) compound containing a nitrogen atom and related to the saturated analogue aziridine. Azirines 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.
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
Substituted azirines can be produced via the Neber rearrangement.
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.
Azirines readily hydrolyse to give aminoketones which are themselves susceptible to self-condensation.
See also
- Dysidazirine, one of only a few naturally-occurring azirines
References
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. https://web.archive.org/web/20060928104209/http://bentham.org/cos/contabs/cos1-3.htm ↩
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. /wiki/Doi_(identifier) ↩
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. Bibcode:1966JAChS..88.1844U. doi:10.1021/ja00960a066. /wiki/Bibcode_(identifier) ↩
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. PMID 36151600. /wiki/Doi_(identifier) ↩