Isoxazole is an azole with an oxygen atom next to the nitrogen. It is also the class of compounds containing this ring. Isoxazolyl is the univalent radical derived from isoxazole.

Full structural formula
Skeletal formula with numbers
Ball-and-stick model
Space-filling model
Preferred IUPAC name
Other names
  • 288-14-2 checkY
3D model (JSmol)
  • Interactive image
  • CHEBI:35595 checkY
  • ChEMBL13257 checkY
  • 8897 checkY
ECHA InfoCard 100.005.472 Edit this at Wikidata
  • 9254
  • 00SRW0M6PW checkY
  • DTXSID7059775 Edit this at Wikidata
  • InChI=1S/C3H3NO/c1-2-4-5-3-1/h1-3H checkY
  • InChI=1/C3H3NO/c1-2-4-5-3-1/h1-3H
  • n1occc1
Molar mass 69.06202 g/mol
Density 1.075 g/ml
Boiling point 95 °C (203 °F; 368 K)
Acidity (pKa) -3.0 (of conjugate acid)[2]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references


Isoxazole rings are found in some natural products, such as ibotenic acid and muscimol.


Isoxazole can be synthesised via a variety of methods.[3][4] Examples include via a 1,3-dipolar cycloaddition of nitrile oxides with alkynes; or the reaction of hydroxylamine with 1,3-diketones or derivatives of propiolic acid.[5]

Pharmaceuticals and herbicidesEdit

Isoxazoles also form the basis for a number of drugs,[6] including the COX-2 inhibitor valdecoxib (Bextra) and a neurotransmitter agonist AMPA. A derivative, furoxan, is a nitric oxide donor. An isoxazolyl group is found in many beta-lactamase-resistant antibiotics, such as cloxacillin, dicloxacillin and flucloxacillin. Leflunomide is an isoxazole-derivative drug. Examples of AAS containing the isoxazole ring include danazol and androisoxazole. A number of pesticides are isoxazoles.[7]

Isoxaben is an example of an isoxazole used as a herbicide.

See alsoEdit


  1. ^ International Union of Pure and Applied Chemistry (2014). Nomenclature of Organic Chemistry: IUPAC Recommendations and Preferred Names 2013. The Royal Society of Chemistry. p. 140. doi:10.1039/9781849733069. ISBN 978-0-85404-182-4.
  2. ^ Zoltewicz, J. A. & Deady, L. W. Quaternization of heteroaromatic compounds. Quantitative aspects. Adv. Heterocycl. Chem. 22, 71-121 (1978)
  3. ^ Dasa S, Chanda K (2021). "An overview of metal-free synthetic routes to isoxazoles: the privileged scaffold". RSC Adv (11): 32680–32705. doi:10.1039/D1RA04624A.
  4. ^ Morita, Taiki; Yugandar, Somaraju; Fuse, Shinichiro; Nakamura, Hiroyuki (March 2018). "Recent progresses in the synthesis of functionalized isoxazoles". Tetrahedron Letters. 59 (13): 1159–1171. doi:10.1016/j.tetlet.2018.02.020.
  5. ^ Hossain M, Khan M, Kim S, Le H (2022). "Synthesis of 3,4,5-trisubstituted isoxazoles in water via a [3 + 2]-cycloaddition of nitrile oxides and 1,3-diketones, β-ketoesters, or β-ketoamides". Beilstein J. Org. Chem. (18): 446–458. doi:10.3762/bjoc.18.47. PMID 35529890.
  6. ^ Zhu, Jie; Mo, Jun; Lin, Hong-zhi; Chen, Yao; Sun, Hao-peng (2018). "The recent progress of isoxazole in medicinal chemistry". Bioorganic & Medicinal Chemistry. 26 (12): 3065–3075. doi:10.1016/j.bmc.2018.05.013.{{cite journal}}: CS1 maint: uses authors parameter (link)
  7. ^ Clemens Lamberth (2018). "Oxazole and Isoxazole Chemistry in Crop Protection". Journal of Heterocyclic Chemistry. 55 (9): 2035–2045. doi:10.1002/jhet.3252.

External linksEdit

  • Synthesis of isoxazoles (overview of recent methods)