Dewar benzene or bicyclohexa-2,5-diene is a bicyclic isomer of benzene with the molecular formula C6H6. The compound is named after James Dewar who included this structure in a list of possible C6H6 structures in 1867. However, he did not propose it as the structure of benzene, and in fact he supported the correct structure previously proposed by August Kekulé in 1865.
Read more about Dewar Benzene: Synthesis and Properties of Bicyclohexa-2,5-diene, "Dewar Benzene" and Benzene, Hexamethyl Dewar Benzene