Diels-Alder reaction of para-substituted allyl and 2-propynyl benzoates with hexabromo- and tetrabromo-5,5-dimethoxy- 1,3-cyclopentadienes

para-Substituted 2-propynyl benzoates are more reactive than the corresponding allyl esters in the Diels-Alder reactions with hexabromo- and tetrabromo-5,5-dimethoxy-1,3-cyclopentadienes. The cycloaddition is favored by the presence of both electron-donor and electron-acceptor substituents in the aromatic ring, in keeping with the “ neutral” reaction scheme. The reactivity of the addends is likely to be determined not only by their donor-acceptor properties but also by the localization energy.