Stereochemistry of Dehydrogenation of 1,4,‐Cyclohexadiene with 2,3‐Dichloro‐5,6‐dicyano‐p‐benzoquinone

cis- and trans-(3,6-D2)-1,4-cyclohexadienes 1a and 1b have been synthesized from cis-3,4-dichlorocyclobutene (5). Aromatization to benzene with DDQ is cis-stereospecific with an uncertainty of 5%. This result is discussed in relation to concerted or stepwise mechanisms for aromatization of 1,4-dihydroaromatics with 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ).