What is the mechanism of Wittig reaction?
Mechanism of the Wittig Reaction. (2+2) Cycloaddition of the ylide to the carbonyl forms a four-membered cyclic intermediate, an oxaphosphetane. Preliminary posultated mechanisms lead first to a betaine as a zwitterionic intermediate, which would then close to the oxaphosphetane.
Is the Wittig reaction stereospecific?
The Z-stereoselective Wittig reaction consists of a stereoselective first step forming the syn oxaphosphetane. This is then followed by a stereospecific elimination of this intermediate to form the Z alkene.
How do Wittig reagents form?
Wittig reagents are usually prepared from a phosphonium salt, which is in turn prepared by the reaction of triphenylphosphine with an alkyl halide via an SN2 reaction. The alkylphosphonium salt is deprotonated with a strong base such as n-butyllithium: [Ph3P+CH2R]X− + C4H9Li → Ph3P=CHR + LiX + C4H.
What is Wittig reaction with example?
| Wittig reaction | |
|---|---|
| Reaction type | Coupling reaction |
| Reaction | |
| aldehyde or ketone + triphenyl phosphonium ylide ↓ alkene + triphenylphosphine oxide | |
| Conditions |
Which functional group is formed in a Wittig reaction?
The Wittig reaction is a popular method for the synthesis of alkene from ketones and aldehydes. The Wittig reagent can generally tolerate carbonyl compounds containing several kinds of functional groups such as OH, OR, aromatic nitro and even ester groups.
Where is the Wittig reaction used?
Wittig reactions are most commonly used to convert aldehydes and ketones to alkenes. Most often, the Wittig reaction is used to introduce a methylene group using methylenetriphenylphosphorane (Ph3P=CH2). Using this reagent, even a sterically hindered ketone such as camphor can be converted to its methylene derivative.
Which reagent is used in Wittig reaction?
triphenyl phosphonium ylide
The Wittig reaction or Wittig olefination is a chemical reaction of an aldehyde or ketone with a triphenyl phosphonium ylide called a Wittig reagent.
Why is sodium hydroxide used in Wittig reaction?
In the second step, a base, such as sodium hydroxide (NaOH) or butyl lithium (BuLi), is used to deprotonate and forms the ylide (Wittig reagent). The ylide is used in the Wittig reaction. The ylide then acts as a nucleophile and adds to the carbonyl carbon. The overall reaction is given below.