Methoxymethylenetriphenylphosphorane

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.

Methoxymethylene­triphenylphosphorane
Names
IUPAC name
Methoxymethylidene(triphenyl)-λ5-phosphane
Identifiers
3D model (JSmol)
  • 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
  • COC=P(C1=CC=CC=C1)(C2=CC=CC=C2)C3=CC=CC=C3
Properties
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).

Preparation

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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

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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

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