Question

Dimethyl cyclopropanes can be prepared by the reaction of an α, β-unsaturated carbonyl compound X with two equivalents of a Wittig reagent Y. Draw a stepwise mechanism for this reaction.

Short answer

Answer

Step-by-step solution

Wittig Reaction

The organic reaction involving the conversion of carbonyl compounds to alkenes using the ylide reagent is known as the ‘Wittig Olefination’.

Mechanism

a. The ylide of the phosphonium salt would attack the carbonyl carbon forming a C-C bond.

Carbonyl compound reacts with phosphonium ylide

b. The nucleophilic carbon would attack the electrophilic carbon center as the pi-electrons are delocalized.

Delocalisation of pi-electrons

c. The lone pair of electrons on the carbon would attack the electrophilic ylide to form a new C-C bond.

Formation of product