The reaction between benzaldehyde and an ylide (such as phosphonium ylide) results in the formation of a betaine intermediate, which subsequently undergoes a [2+2] cycloaddition to afford a substituted alkene.
Mechanism of the reaction:
1. Formation of betaine intermediate:
The ylide attacks the electrophilic carbonyl carbon of benzaldehyde, resulting in the formation of a betaine intermediate. One of the lone pairs on the oxygen atom of the carbonyl group forms a new bond with the carbon of the ylide, leading to the formation of the betaine.
2. [2+2] cycloaddition reaction:
The betaine intermediate undergoes a [2+2] cycloaddition reaction, where the carbon-carbon double bond is formed between the carbon of the ylide and the carbonyl carbon of the benzaldehyde. The oxygen atom of the carbonyl group acts as a nucleophile attacking the carbon of the ylide, resulting in the formation of a substituted alkene.
Overall reaction:
Benzaldehyde + Ylide -> Substituted alkene
Show the reaction between the benzaldehyde and ylide and show the mechanism of the reaction.
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