Wikipedia
Methoxymethylenetriphenylphosphine
Methoxymethylenetriphenylphosphine is a Wittig reagent with used as an reagent in the homologization of aldehydes and ketones to extended aldehydes, an organic reaction first reported in 1958 . This reagent is quite unstable to even mild temperatures and water. As such it must be made in situ, taking on a blood red color, indicative of destabalized ylides.