Abstract
A convenient method for construction of polycyclic fused nitrogen-containing heterocycles has been developed. The methodology involves palladium-catalyzed intermolecular carbopalladation-annulation cascade reaction of haloaryl heterocyclic derivatives with different alkynes under relatively mild reaction conditions. Thus, the palladium-catalyzed cascade cyclization of bromophenyl derivatives of indolizine and indole with alkynes afforded tetracycles, possessing a newly formed fused six-membered ring. The reaction of 3-(2-iodobenzyl)-indoles with a variety of alkynes afforded polycyclic compounds with fused seven-membered rings. Annulation with unsymmetrical alkynes exhibited varied regioselectivity. Overall, this approach allows for quick and efficient assembly of polycyclic derivatives of indole and indolizine from easily available precursors.
Highlights
Polycyclic derivatives of indole[1] and indolizine[2] are important scaffolds, widely found in natural and unnatural bioactive molecules
We wish to report the palladiumcatalyzed intermolecular cascade annulation reactions of bromophenyl and iodobenzyl derivatives of indole and indolizine with alkynes leading to the formation of polycyclic fused six and sevenmembered heterocycles
H2O) allowed for efficient arylation/annulations cascade of 2-(2-bromophenyl)indolizine 1 with 5decyne leading to tetracyclic indolizine 2a in 70% yield (Table 1, entry 1)
Summary
Polycyclic derivatives of indole[1] and indolizine[2] are important scaffolds, widely found in natural and unnatural bioactive molecules. We wish to report the palladiumcatalyzed intermolecular cascade annulation reactions of bromophenyl and iodobenzyl derivatives of indole and indolizine with alkynes leading to the formation of polycyclic fused six and sevenmembered heterocycles.
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