Chemistry:Azirine
Azirines are heterocyclic organic compounds containing a three-membered ring with two carbon atoms and one nitrogen atom, the unsaturated analogs of aziridines. Azirine, the parent compound, has two isomers: the antiaromatic 1H-azirine, containing a carbon–carbon double bond, is not stable and rearranges to the tautomeric 2H-azirine, containing a carbon–nitrogen double bond, which is at least 30 kcal·mol−1 lower in energy.[1] 2H-Azirines can be considered strained imines and are isolable. They are highly reactive yet have been reported in a few natural products such as dysidazirine.[2]
Preparation
2H-Azirine is most often obtained by the thermolysis of vinyl azides.[3] 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.[4] Due to the weak N–O bond, the isoxazole ring tends to collapse under UV irradiation, rearranging to azirine.[5]
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
- Azirinomycin
References
- ↑ Januar, Lawrence A.; Molinski, Tadeusz F. (17 May 2013). "Acremolin from Acremonium strictum is N2,3-Etheno-2'-isopropyl-1-methylguanine, not a 1H-Azirine. Synthesis and Structural Revision". Organic Letters 15 (10): 2370–2373. doi:10.1021/ol400752s.
- ↑ Pinho e Melo, Teresa M. V. D.; d'A. Rocha Gonsalves, António M.. "Exploiting 2-Halo-2H-Azirine Chemistry". Current Organic Synthesis 1 (3): 275–292. doi:10.2174/1570179043366729. https://www.researchgate.net/profile/Teresa-Melo-3/publication/233640215_Exploiting_2-Halo-2H-Azirine_Chemistry/links/0fcfd50d1ffdc2d0e0000000/Exploiting-2-Halo-2H-Azirine-Chemistry.pdf.
- ↑ "2H-Azirines as synthetic tools in organic chemistry". Eur. J. Org. Chem. 2001 (13): 2401–2414. 2001. doi:10.1002/1099-0690(200107)2001:13<2401::AID-EJOC2401>3.0.CO;2-U.
- ↑ Ullman, Edwin F.; Singh, Balwant (April 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. Bibcode: 1966JAChS..88.1844U.
- ↑ Cheng, K.; Qi, J.; Ren, X.; Zhang, J.; Li, H.; Xiao, H.; Wang, R.; Liu, Z. et al. (2022). "Developing Isoxazole as a Native Photo-Cross-Linker for Photoaffinity Labeling and Chemoproteomics.". Angew. Chem. Int. Ed. 61 (47). doi:10.1002/anie.202209947. PMID 36151600.
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