Wittig Reaction


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Wittig Reaction

 

a method of preparing olefins by reacting carbonyl-containing compounds—for example, aldehydes, ketones, formamides, isocyanates, and ketenes— with triphenylphosphine alkylidenes. An example is the formation of isobutene from triphenylphosphine methylene and acetone:

The starting triphenylphosphine methylene is prepared by the action of alkaline reagents on a triphenylmethyl phosphonium salt, which in turn is obtained from triphenylphosphine and an alkyl halide:

The alkaline reagents may be organolithium compounds, sodium amide, alkoxides, and so on.

The Wittig reaction is a very promising process of synthesis, which makes possible the preparation of various olefins, among them polynes (olefins with a large number of multiple bonds).

The synthesis of vitamin A is based on the Wittig reaction, which may also be used to prepare squalene (a precursor of cholesterol), lycopene, bixin esters, and so on.

The Wittig reaction was discovered by the German chemists G. Wittig and U. Schollkopf in 1954.

References in periodicals archive ?
Noshiranzadeh, Magnesium Sulfate Catalyzed Intermolecular Wittig Reaction of Dialkyl 2-(1-acetyl-2-oxopropyl)-3-(triphenyl-phosphoranylidene) Succinates with Ninhydrin in Solvent-Free Conditions, Phosphorus, Sulfur, Silicon Relat.
The well-known Wittig reaction methodology was employed to synthesize D--A conjugated polymer PDTOFV containing 3,4-didodecyloxythiophene, fluorene and 1,3,4-oxadiazole units.
The polymer, PDTOFV, carrying fluorene units was synthesized using a Wittig reaction whereas a Knoe-venagel condensation reaction was used to synthesize polymer PDTOCN which contains cyanophenylenevinylene units.
Among the reactions are Aldol condensation, the Dakin reaction, the Knoevengagel condensation, the Prins reaction, and the Wittig reaction.
Wittig reaction was performed with n-pentyl bromide and C-11 aldehyde which resulted in the formation of 1, 11--hexadecadiene of mearly 85% purity.
Mechanically induced solid-state generation of phosphorus ylides and the solvent-free Wittig reaction.
Since its development in 1953, the Wittig reaction has been employed in numerous synthetic transformations and several variants have appeared.
Gilheany, The Modern Interpretation of the Wittig Reaction Mechanism,Chem.
Maercker, The Wittig Reaction, Organic Reactions, John Wiley and Sons, Inc.
Wittig reaction was used for the preparation of first two compounds and third one by Knoevehagel condensation.
Keywords: dendralene, Wittig reaction, cross- conjugation, UV-Vis, Knoevehagel condensation