Diels-Alder reaction of <Emphasis Type="Italic">para</Emphasis>-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.Translated from Zhurnal Organicheskoi Khimii, Vol. 40, No. 9, 2004, pp. 1324–1328.Original Russian Text Copyright © 2004 by Magerramov, Mustafaev, Velieva, Murshudova, Allakhverdiev.     

Polybromocyclopentadienes in Diels–Alder Reactions. Reactions of Hexabromo- and 5,5-Dimethoxytetrabromo-1,3-cyclopentadienes with para-Substituted Allyl Benzoates

The Diels–Alder reaction of hexabromo- and 5,5-dimethoxytetrabromo-1,3-cyclopentadienes with para-substituted allyl benzoates occurs with high stereoselectivity, yielding the corresponding endo adducts. The kinetics of this reaction were studied, and its activation parameters were determined. The reaction is favored by the presence of both electron-donor and electron-acceptor substituents in the aromatic ring. The diene–dienophile system was assumed to react according to the neutral pattern.