Benzocyclobutadiene

Benzocyclobutadiene is the simplest polycyclic aromatic hydrocarbon, being composed of a benzene ring fused to a cyclobutadiene ring. It has chemical formula C₈H₆. Though the benzene ring is stabilized by aromaticity, the cyclobutadiene portion has a destabilizing effect. For this reason, benzocyclobutadiene will readily dimerize or polymerize and it reacts as a dienophile in Diels-Alder reactions.

Benzocyclobutadiene is used in the production of the pharmaceutical drug naflocort.