Questions tagged [wittig-reactions]
This tag should be applied to questions about the Wittig reaction and its variants, including the Horner–Wadsworth–Emmons reaction.
15
questions
6
votes
1
answer
100
views
H-NMR: Why are coupling and integration values not matching?
I am trying to synthesize Ethyl 2-(triphenylphosphoranylidene)propionate.
I recently ran an NMR which is attached below.
I am ignoring impurities for now.
Considering the ethyl group, the number of ...
- 567
1
vote
0
answers
125
views
Wittig reaction without ketone or aldehyde?
In the reaction below the ethylene glycol would react with the ketone in the first step turning it into a protecting group. How would the ylide react, as I thought it only reacts with ketones and ...
- 107
7
votes
1
answer
368
views
Synthesis of (1S,2S,4S)-4-ethenyl-5-methylcyclohexane-1,2-diol
I'm trying to devise a synthesis for the following question.
I am aware it involves retrosynthetic, Wittig, Grignard and diels alder reactions, but unfortunately I can't really grasp all concepts ...
- 139
5
votes
0
answers
75
views
Wittig reagent with metal–oxo bonds
Could you use the Wittig reagent to attack a metal–oxo bond and replace the oxygen with a carbene?
Specifically, is it possible for the Wittig reagent to do σ-bond metathesis with an electrophilic ...
- 51
4
votes
1
answer
2k
views
Wittig reaction in presence of carboxylic acids
The following reaction came in a recent test:
According to this reaction, the acidic hydrogen would protonate the ylide, and the standard wittig reaction would not take place. This source agrees with ...
- 6,278
6
votes
2
answers
862
views
Reagent choice in the formation of Wittig reagent
During the formation of Wittig reagent, BuLi is used as it is a VERY strong base (pKa = 50). According to Wikipedia, however, sulfur ylide is 'especially conveniently' made from dimsyl anion (pKa = 35)...
- 549
5
votes
2
answers
2k
views
What will be the major product of the reaction between (2R,3R)-2,3-dimethyloxirane and triphenylphosphine?
Problem
My Attempt
But answer is given B. Where did I go wrong?
- 623
1
vote
1
answer
378
views
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 ...
- 10.7k
-3
votes
1
answer
74
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?
2
votes
1
answer
3k
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 ...
- 321
5
votes
1
answer
287
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.
- 14.4k
8
votes
1
answer
5k
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 ...
- 71.6k
12
votes
1
answer
1k
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 ...
- 8,495
25
votes
2
answers
3k
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 ...
- 68.4k
32
votes
1
answer
22k
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 ...
- 475