Methoxymethylenetriphenylphosphorane

Methoxymethylenetriphenylphosphorane
Names
	IUPAC name Methoxymethylidene(triphenyl)-λ5-phosphane
Identifiers
CAS Number	20763-19-3;
3D model (JSmol)	Interactive image;
PubChem CID	11748776;
CompTox Dashboard (EPA)	DTXSID901282268 ;
	InChI InChI=1S/C20H19OP/c1-21-17-22(18-11-5-2-6-12-18,19-13-7-3-8-14-19)20-15-9-4-10-16-20/h2-17H,1H3 Key: DYROHZMICXBUMX-UHFFFAOYSA-N;
	SMILES COC=P(C1=CC=CC=C1)(C2=CC=CC=C2)C3=CC=CC=C3;
Properties
Chemical formula	C20H19OP
Molar mass	306.345 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

Methoxymethylenetriphenylphosphorane is a Wittig reagent used for the homologization of aldehydes, and ketones to extended aldehydes, a organic reaction first reported in 1958.^[1] The reagent is generally prepared and used in situ. It has blood-red color, indicative of destabilized ylides.

Preparation

The reagent can be prepared in two steps from triphenylphosphine. The first step is P-alkylation with chloromethyl methyl ether.

PPh₃ + CH₃OCH₂Cl → [CH₃OCH₂PPh₃]Cl

In the second step, the resulting phosphonium salt is deprotonated.

[CH₃OCH₂PPh₃]Cl + LiNR₂ → CH₃OCH=PPh₃ + LiCl + HNR₂

In place of chloromethyl methyl ether, a mixture of methylal and acetyl chloride can be used.

Uses

This reagent reacts with a ketone or aldehyde in a Wittig reaction to give an enol ether, which can be converted to the aldehyde by acid-induced hydrolysis.

The initial report of the reaction demonstrated its use on the steroid tigogenone.^[2]

It was later used in the Wender Taxol total synthesis and the Stork quinine total synthesis.

References

^ A new aldehyde synthesis Samuel G. Levine J. Am. Chem. Soc.; 1958; 80(22); 6150–6151. doi:10.1021/ja01555a068