Methoxymethylenetriphenylphosphorane

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

Methoxymethylene­triphenylphosphorane

Names
IUPAC name Methoxymethylidene(triphenyl)-λ5-phosphane
Identifiers
CAS Number	20763-19-3
3D model (JSmol)	Interactive image
PubChem CID	11748776
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

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.

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

References

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