Cascade olefin isomerization/intramolecular Diels-Alder reaction catalyzed by N-heterocyclic carbenes.
The addition of an N-heterocyclic carbene to the carbonyl group of an α,β,γ,δ-unsaturated enol ester affords a hemiacetal azolium intermediate that enables a cascade olefin isomerization/Diels-Alder reaction, for which mechanistic studies implicate Lewis base catalysis. Preliminary studies into the utility of the products have been undertaken with reductive and oxidative cleavage, giving materials for potential use in complex-target synthesis.
School of Chemistry, Monash University, Clayton 3800, Victoria (Australia).
Marcin
M
Kowalczyk
David W
DW
Lupton
Diels-Alder reaction; N-heterocyclic carbenes; hemiacetal azolium intermediates; olefin isomerization; organocatalysis