Question

Show how the following compound can be prepared from starting materials that have no more than five carbons:

Short answer

If an aldol addition uses two different carbonyl compounds, such reactions are crossed aldol addition.

A single product can be obtained in this reaction if one of the aldehydes does not comprise alpha hydrogen and cannot form an enolate ion.

Step-by-step solution

Crossed Aldol addition

If an aldol addition uses two different carbonyl compounds, such reactions are crossed aldol addition.

A single product can be obtained in this reaction if one of the aldehydes does not comprise alpha hydrogen and cannot form an enolate ion.

Identifying how the given compound can be prepared from starting materials that have no more than five carbons

The given compound is prepared from the starting material with no more than five carbons through a series of steps. An - unsaturated carbonyl compound is reacted with a base leading to the formation of an enolate ion.

This ion attacks another cyclic unsaturated compound. An intramolecular cyclization happens in the last transformation, and the formation of the required compound takes place. The reaction is given below.