Methoxymethylenetriphenylphosphorane
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Methoxymethylenetriphenylphosphorane is a Wittig reagent used for the homologization of
aldehyde In organic chemistry, an aldehyde () (lat. ''al''cohol ''dehyd''rogenatum, dehydrogenated alcohol) is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred ...
s, and
ketone In organic chemistry, a ketone is an organic compound with the structure , where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group (a carbon-oxygen double bond C=O). The simplest ketone is acetone ( ...
s to extended aldehydes, an
organic reaction Organic reactions are chemical reactions involving organic compounds. The basic organic chemistry reaction types are addition reactions, elimination reactions, substitution reactions, pericyclic reactions, rearrangement reactions, mechanistic organ ...
first reported in 1958. The
reagent In chemistry, a reagent ( ) or analytical reagent is a substance or compound added to a system to cause a chemical reaction, or test if one occurs. The terms ''reactant'' and ''reagent'' are often used interchangeably, but reactant specifies a ...
is generally prepared and used in situ. It has blood-red color, indicative of destabilized
ylide An ylide () or ylid () is a neutral dipolar molecule containing a formally negatively charged atom (usually a carbanion) directly attached to a heteroatom with a formal positive charge (usually nitrogen, phosphorus or sulfur), and in which both ...
s.


Preparation

The reagent can be prepared in two steps from triphenylphosphine. The first step is ''P''-
alkylation Alkylation is a chemical reaction that entails transfer of an alkyl group. The alkyl group may be transferred as an alkyl carbocation, a free radical, a carbanion, or a carbene (or their equivalents). Alkylating agents are reagents for effecting al ...
with chloromethyl methyl ether. : In the second step, the resulting phosphonium salt is deprotonated. : In place of chloromethyl methyl ether, a mixture of methylal and
acetyl chloride Acetyl chloride () is an acyl chloride derived from acetic acid (). It belongs to the class of organic compounds called acid halides. It is a colorless, corrosive, volatile liquid. Its formula is commonly abbreviated to AcCl. Synthesis On an ...
can be used.


Uses

This reagent reacts with a ketone or aldehyde in a
Wittig reaction The Wittig reaction or Wittig olefination is a chemical reaction of an aldehyde or ketone with a triphenyl phosphonium ylide called a Wittig reagent. Wittig reactions are most commonly used to convert aldehydes and ketones to alkenes. Most o ...
to give an
enol ether In organic chemistry an enol ether is an alkene with an alkoxy substituent. The general structure is R2C=CR-OR where R = H, alkyl or aryl. A common subfamily of enol ethers are vinyl ethers, with the formula ROCH=CH2. Important enol ethers incl ...
, which can be converted to the aldehyde by acid-induced hydrolysis. The initial report of the reaction demonstrated its use on the
steroid A steroid is an organic compound with four fused compound, fused rings (designated A, B, C, and D) arranged in a specific molecular configuration. Steroids have two principal biological functions: as important components of cell membranes t ...
tigogenone. : It was later used in the Wender Taxol total synthesis and the Stork quinine total synthesis.


References

# {{Note, Levine ''A new aldehyde synthesis'' Samuel G. Levine J. Am. Chem. Soc.; 1958; 80(22); 6150–6151. doi:10.1021/ja01555a068 Homologation reactions Organophosphanes Methoxy compounds