azirine
{{Chembox
| ImageFile = Azirin.svg
| ImageSize = 100px
| IUPACName = 2H-Azirine
| OtherNames =
| Section1 = {{Chembox Identifiers
| CASNo = 157-16-4
| Beilstein = 1633516
| ChEBI = 30971
| ChEMBL =
| ChemSpiderID = 119750
| DrugBank =
| EC_number =
| KEGG =
| MeSHName =
| PubChem = 135972
| InChI = 1S/C2H3N/c1-2-3-1/h1H,2H2
| InChIKey = NTJMGOWFGQXUDY-UHFFFAOYSA-N
| SMILES = C1C=N1
}}
| Section2 = {{Chembox Properties
| C=2 | H=3 | N=1
| Appearance =
| Density =
| MeltingPt =
| BoilingPt =
| Solubility =
}}
| Section3 = {{Chembox Hazards
| MainHazards =
| FlashPt =
| AutoignitionPt =
}}
}}
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.{{cite journal|author=Teresa M. V. D. Pinho e Melo and Antonio M. d’A. Rocha Gonsalves|journal=Current Organic Synthesis|volume=1|issue=3|year=2004|pages=275–292|title=Exploiting 2-Halo-2H-Azirine Chemistry|url=http://www.bentham.org/cos/contabs/cos1-3.htm#5|doi=10.2174/1570179043366729|url-status=dead|archive-url=https://web.archive.org/web/20060928104209/http://bentham.org/cos/contabs/cos1-3.htm|archive-date=2006-09-28 }} 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.
Preparation
2H-Azirine is most often obtained by the thermolysis of vinyl azides.{{cite journal|title=2H-Azirines as synthetic tools in organic chemistry|vauthors=Palacios F, Ochoa de Retana AM, Martinez de Marigorta E, de los Santos JM|journal=Eur. J. Org. Chem.|year=2001|pages=2401–2414|doi=10.1002/1099-0690(200107)2001:13<2401::AID-EJOC2401>3.0.CO;2-U|volume=2001|issue=13}} 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.{{cite journal | author =Edwin F. Ullman| title = Photochemical Transposition of Ring Atoms in Five-Membered Heterocycles. The Photorearrangement of 3,5-Diphenylisoxazole | journal = J. Am. Chem. Soc. |volume = 88 |issue = 8 | pages = 1844–1845 | date = 1966| doi = 10.1021/ja00960a066 }} Due to the weak N-O bond, the isoxazole ring tends to collapse under UV irradiation, rearranging to azirine. {{cite journal | author1 = Cheng, K. |author2=Qi, J. |author3=Ren, X. |author4=Zhang, J. |author5=Li, H. |author6=Xiao, H. |author7=Wang, R. |author8=Liu, Z. |author9=Meng, L |author10=Ma, N. |author11=Sun, H.| title = Developing Isoxazole as a Native Photo-Cross-Linker for Photoaffinity Labeling and Chemoproteomics. | journal = Angew. Chem. Int. Ed. |volume=61 |issue= 47 | pages = e202209947 | date = 2022| doi = 10.1002/anie.202209947 }}
:File:Synth-Azirin.svg{{Clear|left}}
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
{{Reflist}}