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.

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\dPPh3  +  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.
 * [[Image:Titogenone.png|500px|Titogenone homologation]]

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