Discovery of Oxygen Induced Chemoselectivity in Pd-Catalyzed C-H Functionalization: Cross-Dehydrogenative Coupling vs C-H Amination

We have come across a substrate namely, 5-benzoyl-pyrrolo[2,1-a]isoquinoline in which three different functionalizableC-H bonds were identified that could be judiciously transformedsite selectively for the generation of complex polyring fused N-heterocycles. A Pd-catalyzed cross-dehydrogenative couplingof 5-benzoyl-pyrrolo[2,1-a]isoquinoline afforded8H-indeno-pyrrolo[2,1-a]isoquinolinoneand an oxygen induced palladium catalyzed selective C-H aminationin the same substrate provided a pentacene viz., 9H-indolo-pyrrolo[2,1-a]isoquinoline. We also observedthe formation of a multiring fused benzazepine scaffold by the siteselective C-H amination in 5-(4-nitro benzoyl)-pyrrolo[2,1-a]isoquinoline.