On the mechanism of the meta photocycloaddition of ethylenes to benzenoid compounds

Abstract

cis-Cyclo-octene undergoes locoselective meta photocycloaddition to isopropylbenzene, t-butylbenzene, p-methylcumene, anisole, and p-methylanisole. The results are discussed in terms of substituent stabilisation of the intermediates produced either by meta ethylene cycloaddition to the S₁ arene or by meta bonding in the photoexcited benzene derivative. The mechanistic pathway preferred appears to be influenced by steric effects of the arene and ethylene substituents.