Friedel–Crafts Transannular Alkylation of Aromatic Compounds with Nonconjugated Cyclic Dienes

Abstract Friedel–Crafts transannular alkylation of aromatic compounds with nonconjugated cyclic dienes such as (Z,Z)-1,5-cyclooctadiene (1,5-COD), bicyclo[2.2.1]hepta-2,5-diene (norbornadiene), and 1,4-cyclohexadiene was studied. The five to six isomers of phenylbicyclooctanes were produced in the alkylation of benzene with 1,5-COD in the presence of either Brönsted acid or Lewis acid as the catalyst. The isomer ratios depended on the nature and the amount of catalyst, the reaction time, and the reaction temperature. In the AlCl3-catalyzed reaction of 1,5-COD with toluene it was disclosed that an initial para-rich isomer distribution of the products shifted to a meta-rich one in a prolonged reaction. With norbornadiene a transannular cyclized compounds was obtained, while with 1,4-cyclohexadiene no transannular cyclization was observed.