Pericyclic reactions of cyclopentadienones with nonactivated olefins in phenolic solvents. Enhancement of the reactivity and periselectivity

Article abstract of DOI:10.1016/S0040-4020(99)00259-8

The solvent effect of phenols on the reactivity and periselectivity for the pericyclic reactions of cyclopentadienones with olefins involving conjugated medium-ring polyenes has been investigated. The use of phenols as a solvent accelerates tile reaction rates of cycloadditions of cyclopentadienones with nonactivated olefins. In the reaction of cycloheptatriene in p-chlorophenol, the exo [4+6]π cycloadduct was produced predominantly, in which a 15-fold increase of the reaction rate was observed as compared with that in benzene. The [3,3]-sigmatropy and decarbonylation of the primary cycloadducts were also accelerated by phenols. The possible role of phenols is discussed on the basis of kinetic and molecular orbital (MO) calculation data.