oxaphosphetane

{{Chembox

|OtherNames = 1,2-Oxaphosphetane
1,3-Oxaphosphetane

|ImageFileL1 = 1,2-Oxaphosphetane.png

|ImageCaptionL1 = 1,2-Oxaphosphetane

|ImageFileR1 = 1,3-Oxaphosphetane.png

|ImageCaptionR1 = 1,3-Oxaphosphetane

|ImageFileL2 = 1,2-oxaphosphetane-based-on-xtal-LIGREB-3D-bs-17.png

|ImageCaptionL2 = Ball-and-stick model of 1,2-oxaphosphetane

|ImageFileR2 = 1,3-oxaphosphetane-inspired-by-xtal-LIGREB-3D-bs-17.png

|ImageCaptionR2 = Ball-and-stick model of 1,3-oxaphosphetane

|Section1={{Chembox Identifiers

|index_label=1,2

|index3_label=1,3

|CASNo = 287-36-5

|CASNo3 = 25885-35-2

|CASNo_Ref = {{cascite|correct|CAS}}

|CASNo3_Ref = {{cascite|correct|CAS}}

|ChemSpiderID = 14123776

|DTXSID = DTXSID90633467

|PubChem = 23373974

|PubChem3 = 20362213

|InChI=1S/C2H5OP/c1-2-4-3-1/h4H,1-2H2

|InChIKey = JONKIUBSNSUGGZ-UHFFFAOYSA-N

|SMILES = C1CPO1

|InChI3=1S/C2H5OP/c1-3-2-4-1/h4H,1-2H2

|InChIKey3 = XIEBRVIWJYCCCK-UHFFFAOYSA-N

|SMILES3 = C1OCP1

}}

|Section2={{Chembox Properties

| C=2|H=5|O=1|P=1

}}

}}

File:Wittig-oxaphosphetane-from-xtal-2005-3D-sticks.png of a 1,2-oxaphosphetane that has been isolated and characterised by X-ray crystallography.{{ cite journal |author=M. Hamaguchi |author2=Y. Iyamaa |author3=E. Mochizukia |author4=T. Oshima | title = First isolation and characterization of 1,2-oxaphosphetanes with three phenyl groups at the phosphorus atom in typical Wittig reaction using cyclopropylidenetriphenylphosphorane | journal = Tetrahedron Letters | year = 2005 | volume = 46 | issue = 51 | pages = 8949–8952 | doi = 10.1016/j.tetlet.2005.10.086}}]]

An oxaphosphetane is a molecule containing a four-membered ring with one phosphorus, one oxygen and two carbon atoms. In a 1,2-oxaphosphetane phosphorus is bonded directly to oxygen, whereas a 1,3-oxaphosphetane has the phosphorus and oxygen atoms at opposite corners.

1,2-Oxaphosphetanes are rarely isolated but are important intermediates in the Wittig reaction and related reactions such as the Seyferth–Gilbert homologation and the Horner–Wadsworth–Emmons reaction.{{cite journal | first1 = Peter A. | last1 = Byrne | first2 = Declan G. | last2 = Gilheany | title = The modern interpretation of the Wittig reaction mechanism | journal = Chemical Society Reviews | year = 2013 | volume = 42 | issue = 16 | pages= 6670–6696 | doi = 10.1039/C3CS60105F | pmid = 23673458 | hdl = 10197/4939 | hdl-access = free}} Edwin Vedejs's NMR studies first revealed the importance of oxaphosphetanes in the mechanism of the Wittig reaction in the 1970s.{{cite journal | title = Studies in Heteroelement-Based Synthesis | vauthors = Vedejs E | journal = The Journal of Organic Chemistry | volume = 69 | issue = 16 | pages = 5159–5167 | date = 30 July 2004 | doi = 10.1021/jo049360l| pmid = 15287757}}{{Cite web| url=https://kb.wisconsin.edu/images/group222/shared/2018-02-05FacultySenate/2719VedejsMR.pdf |title=Memorial Resolution of the Faculty of the University of Wisconsin-Madison|work=University of Wisconsin-Madison|access-date=9 May 2020|archive-url=https://web.archive.org/web/20200509230713/https://kb.wisconsin.edu/images/group222/shared/2018-02-05FacultySenate/2719VedejsMR.pdf|archive-date=9 May 2020}}

In 2005 the first isolation of 1,2-Oxaphosphetanes (typical Wittig intermediates) was reported.{{ cite journal |author=M. Hamaguchi |author2=Y. Iyamaa |author3=E. Mochizukia |author4=T. Oshima | title = First isolation and characterization of 1,2-oxaphosphetanes with three phenyl groups at the phosphorus atom in typical Wittig reaction using cyclopropylidenetriphenylphosphorane | journal = Tetrahedron Letters | year = 2005 | volume = 46 | issue = 51 | pages = 8949–8952 | doi = 10.1016/j.tetlet.2005.10.086}} One of the compounds was characterized by X-ray crystallography and NMR. Although relatively stable, thermal decomposition of these oxaphosphetanes gave a phosphonium salt, which slowly dissociated to the Wittig reaction starting materials, the carbonyl and olefin compounds.