%0 Journal Article
%@ 0040-4020
%A Wipf, P
%A Xu, W
%D 1995
%F pittir:25723
%J Tetrahedron
%N 15
%P 4551 - 4562
%T Zirconocene-catalyzed cationic Diels-Alder reactions
%U http://d-scholarship-dev.library.pitt.edu/25723/
%V 51
%X In situ prepared Cp2ZrCl⊕ catalyzes the formation of dioxolenium ions from α,β-unsaturated epoxy esters. As a consequence of this activation process, acrylate, methacrylate and crotonate derivatives undergo a rapid and stereoselective cationic [4+2] cycloaddition with a wide range of dienes. Ring-extended carboxylic acid derivatives are formed in 1-7 h at 0-21 °C and in 50-90% yield after saponification of the intermediate diol esters. Simple Lewis acid catalysis by Cp2ZrCl⊕ can be excluded on the basis of the experimental results. © 1995.