Wittig reaction

The Wittig reaction converts an aldehyde or ketone into an alkene using a phosphorus ylide, typically forming triphenylphosphine oxide as a byproduct.

Phosphorus ylide: A phosphorus compound with a negatively charged carbon adjacent to a positively charged phosphorus atom. Its carbon attacks the carbonyl carbon and supplies one alkene carbon.
Aldehyde: An organic compound containing a terminal carbonyl group bonded to hydrogen. Aldehydes are common Wittig substrates and often react more readily than ketones.
Stereoselective synthesis: The synthesis of products in which one stereoisomer forms preferentially over others. Ylide choice can influence whether the newly formed alkene is E or Z.
Georg Wittig: A German chemist who developed phosphorus-ylide olefination and shared the 1979 Nobel Prize in Chemistry. The named reaction reflects his development of this synthetic method.
Oxaphosphetane: A four-membered ring containing one oxygen, one phosphorus, and two carbon atoms. This proposed intermediate connects carbonyl addition to alkene and phosphine oxide formation.
Ketone: An organic compound whose carbonyl carbon is bonded to two carbon groups. Ketones are valid substrates, though steric hindrance can make them less reactive.
Retrosynthetic analysis: A method for planning synthesis by mentally disconnecting a target molecule into simpler precursors. Disconnecting an alkene into a carbonyl compound and a ylide suggests Wittig disconnections.
Wittig rearrangement: A base-induced rearrangement of an ether involving a carbon–carbon bond migration. Despite sharing Wittig’s name, this is a distinct reaction rather than an olefination.
Carbonyl group: A functional group consisting of a carbon atom double-bonded to an oxygen atom. The reaction replaces this group’s oxygen with a carbon from the ylide.
Triphenylphosphine: An organophosphorus compound with phosphorus bonded to three phenyl groups. It is commonly used to construct the phosphonium precursor to a Wittig ylide.

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