Bridged Synthons from Tetrabromocyclopropene: Studies on the Rearrangement of the Primary Diels−Alder Adduct with 2,5-Dimethylfuran

The reaction of tetrabromocyclopropene and
furan leads directly to 8-oxabicyclo[3.2.1]octadiene derivatives. It has been proposed that this involves an initial
Diels−Alder reaction followed by rearrangement of the
primary adduct. We have, for the first time, isolated a
primary adduct and established through X-ray crystallographic analysis that the adduct is the product of an exo-selective addition. Kinetic studies suggest the intermediacy
of charged intermediates during the rearrangement.