Question: One step in the synthesis of periplanone B, the chapter-opening molecule, involved anionic oxy-Cope rearrangement of the following unsaturated alcohol. Draw the product that results after protonation of the intermediate enolate.

Periplanone B is a kind of diepoxide and comprises of a structure possessing a ten-membered ring. It is a pheromone generated by the female American cockroach.

Unsaturated alcohols undergo the rearrangement termed as the oxy-cope rearrangement. The rearranged product that is acquired from oxy-cope rearrangement possesses a high yield when mild reaction conditions are utilized.

The first step is the abstraction of the proton of hydroxyl group by a strong base. The alkoxide produced in the reaction undergoes [3,3] sigmatropic rearrangement to form a resonance stabilized enolate. The reaction can be given as:

First step in the synthesis of periplanone B

The enolate formed in this reaction undergoes protonation followed by the electrocyclic ring opening of the four membered ring. A ten membered ring is formed and the chemical reaction can be given as:

Protonation of enolate in periplanone B