Methoxymethylenetriphenylphosphorane is a Wittig reagent used for the homologization of aldehydes, and ketones to extended aldehydes, an 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.

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.

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.

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