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For stabilized Wittig reagents bearing conjugated electron-withdrawing groups, even relatively weak bases like aqueous sodium hydroxide or potassium carbonate can be employed. [Ph 3 PCH 3] + Br −, typical phosphonium salt. The identification of a suitable base is often an important step when optimizing 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. [1] [2] [3] Most often, the Wittig reaction is used to introduce a methylene group using ...
Methylenetriphenylphosphorane is an organophosphorus compound with the formula Ph 3 PCH 2. It is the parent member of the phosphorus ylides, popularly known as Wittig reagents. It is a highly polar, highly basic species.
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.
For example, the reaction of triphenylphosphine with methyl bromide gives methyltriphenylphosphonium bromide: PPh 3 + CH 3 Br → [CH 3 PPh 3] + Br −. The methyl group in such phosphonium salts is mildly acidic, with a pK a estimated to be near 15: [5] [CH 3 PPh 3] + + base → CH 2 =PPh 3 + [Hbase] + This deprotonation reaction gives Wittig ...
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.
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.
Methyltriphenylphosphonium bromide is the organophosphorus compound with the formula [(C 6 H 5) 3 PCH 3]Br. It is the bromide salt of a phosphonium cation. It is a white salt that is soluble in polar organic solvents.