Oxaphosphetane

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.

Oxaphosphetane

1,2-Oxaphosphetane 1,3-Oxaphosphetane
Ball-and-stick model of 1,2-oxaphosphetane Ball-and-stick model of 1,3-oxaphosphetane
Names
Other names 1,2-Oxaphosphetane 1,3-Oxaphosphetane
Identifiers
CAS Number	1,2: 287-36-5 Y 1,3: 25885-35-2 Y
3D model (JSmol)	1,2: Interactive image 1,3: Interactive image
ChemSpider	1,2: 14123776
PubChem CID	1,2: 23373974 1,3: 20362213
CompTox Dashboard (EPA)	1,2: DTXSID90633467
InChI 1,2: InChI=1S/C2H5OP/c1-2-4-3-1/h4H,1-2H2 Key: JONKIUBSNSUGGZ-UHFFFAOYSA-N 1,3: InChI=1S/C2H5OP/c1-3-2-4-1/h4H,1-2H2 Key: XIEBRVIWJYCCCK-UHFFFAOYSA-N
SMILES 1,2: C1CPO1 1,3: C1OCP1
Properties
Chemical formula	C2H5OP
Molar mass	76.035 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Stick model of a 1,2-oxaphosphetane that has been isolated and characterised by X-ray crystallography.^[1]

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.^[2] Edwin Vedejs's NMR studies first revealed the importance of oxaphosphetanes in the mechanism of the Wittig reaction in the 1970s.^[3][4]

In 2005 the first isolation of 1,2-Oxaphosphetanes (typical Wittig intermediates) was reported.^[5] 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.