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DOI: 10.1055/s-2008-1083376
Reactivity of 2-Halo-2H-azirines. Part II. Thermal Ring Expansion Reactions: Synthesis of 4-Haloisoxazoles
Publication History
Publication Date:
21 February 2009 (online)
We had reported that under thermolysis 2-benzoyl-2-halo-2H-azirine-3-carboxylates 1 undergo ring expansion giving products in high yield which were identified as being 4-haloisoxazoles 3 (Scheme 1). The same products can also be obtained in high yield from the thermolysis of haloazidoalkenes 2 via intermediate 2-benzoyl-2-halo-2H-azirines 1.
![](https://www.thieme-connect.de/media/synthesis/200905/r10509_s1.gif)
Scheme 1
Recently, new data have been disclosed allowing to demonstrate that methyl 2-benzoyl-2-halo-2H-azirine-3-carboxylates undergo thermal ring expansion to give 4-halo-5-phenyl-1,3-oxazole-2-carboxylates 4 and not the isomeric isoxazoles (Scheme 2).1 These 1,3-oxazoles can also be obtained in high yield from haloazidoalkenes 2.
![](https://www.thieme-connect.de/media/synthesis/200905/r10509_s2.gif)
Scheme 2
Reference
(1) Lopes, S.; Nunes, C. M.; Fausto, R.; Pinho e Melo, T. M. V. D. J. Mol. Struct. 2009, 919, 47.
![](https://www.thieme-connect.de/media/synthesis/200905/r10509_s1.gif)
Scheme 1
![](https://www.thieme-connect.de/media/synthesis/200905/r10509_s2.gif)
Scheme 2