Structure of Trimers Derived from Diels-Alder Reactions between Cyclopentadiene and Isoprene

Abstract

In order to elucidate the stereochemistry of 1:2 adducts derived from the Diels-Alder reactions of cyclopentadiene and isoprene, 1:1 adducts were allowed to react with additional cyclopentadiene or isoprene. Several trimers having a norbornane or a norbornene skeleton were the predominant products, comprising more than 80% of the trimers yielded. Although a few isoprene dimers were obtained, no 1:2 adduct involving isoprene dimer was produced. The configuration of 1:2 adducts 8 through 15, except for 10 and 11, was established by means of ¹³C-NMR spectroscopy.