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Wittig reagents are usually prepared from a phosphonium salt, which is in turn prepared by the quaternization of triphenylphosphine with an alkyl halide. Wittig reagents are usually derived from a primary alkyl halide. Quaternization of triphenylphosphine with secondary halides is typically inefficient.
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. [1] [2] [3] Most often, the Wittig reaction is used to introduce a methylene group using ...
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. It was later used in the Wender Taxol total synthesis and the Stork quinine total synthesis.
The [2,3]-Wittig rearrangement is the transformation of an allylic ether into a homoallylic alcohol via a concerted, pericyclic process. Because the reaction is concerted, it exhibits a high degree of stereocontrol, and can be employed early in a synthetic route to establish stereochemistry.
It is the parent member of the phosphorus ylides, popularly known as Wittig reagents. It is a highly polar, highly basic species. It is a highly polar, highly basic species. Preparation and use
A 1,2-Wittig rearrangement is a categorization of chemical reactions in organic chemistry, and consists of a 1,2-rearrangement of an ether with an alkyllithium compound. [1] The reaction is named for Nobel Prize winning chemist Georg Wittig. [2] [3] The intermediate is an alkoxy lithium salt, and the final product an alcohol.
The Corey–Fuchs reaction is based on a special case of the Wittig reaction, where two equivalents of triphenylphosphine are used with carbon tetrabromide to produce the triphenylphosphine-dibromomethylene ylide. [2] Step 1 of the Corey-Fuchs reaction, generating the active ylide. This ylide undergoes a Wittig reaction when exposed to an aldehyde.
The mechanism of the aza-Wittig reaction is analogous to that of the Wittig reaction, with the Wittig reagent replaced by an iminophosphorane. [1] Mechanism of Aza-Wittig-reaction. In some cases, the iminophosphorane is not isolated but generated in situ. In this manifestation, the phosphine, carbonyl, and organic azide are combined