Questions tagged [wittig-reactions]

This tag should be applied to questions about the Wittig reaction and its variants, including the Horner–Wadsworth–Emmons reaction.

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Wittig reaction with an alkyl dibromide

Recently, I have come across a problem, in which a ketone needs to be converted into an alkene. However, in the alkene product, there is also another bromide functional group, at the end of the alkyl ...
-3
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1answer
45 views

how can i synthesis unsaturated ester via wittig reaction? [closed]

What is the best pocedure to synthesis ethyl cinnamate using benzaldehyde and (carbethoxymethylene)triphenylphosphorane (wittig reagent) and chloroform as solvent via wittig reaction?
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1answer
908 views

What is the function of PhLi in this reaction?

Can someone please explain the mechanism of the reaction when we add 2 moles of $ \ce{Ph3P}$ and $\ce{PhLi}$ to 1,2-dichloroethane. I know this is a type of Wittig reaction but I am not able to ...
5
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1answer
174 views

Ylides nucleophilicity comparison

Why are phosphonate-stabilised ylides used in HWE reaction more nucleophilic than phosphonium ylids used in Wittig reaction? Explanations without rationalisations using d orbitals would be welcome.
7
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1answer
2k views

Why do stabilised ylids lead to trans alkenes in the Wittig reaction?

Why do stabilised ylids (such as $\ce{Ph3P=CHCO2Me}$) lead to (E)-alkenes in the Wittig reaction, in contrast to unstabilised ylids which are (Z)-selective? The (E)-alkene is formed from ...
11
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1answer
501 views

Wittig versus Corey–Chaykovsky reaction

The Wittig and Corey–Chaykovsky reaction both involve an ylid, phosphonium ylid in the former versus a sulfonium ylid in the latter, attacking a carbonyl compound. In the Wittig reaction, a ...
22
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2answers
1k views

Which is the currently accepted mechanism of a Wittig reaction?

The Wittig reaction is one of the most significant advances in synthetic organic chemistry in the 20th century and rightfully won its discoverer, Georg Wittig, the Nobel Prize in Chemistry. A Wittig ...
30
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1answer
18k views

Why does the unstabilised Wittig reaction selectively form cis alkenes?

This question is meant for a simple unstabilised ylide. The mechanism of the Wittig reaction, as given on ChemTube3d, involves a concerted formation of the oxaphosphetane (this is generally favoured ...