Rhodium-Catalyzed Dual C-H Activation for Regioselective Triple Annulation of Enaminones: Access to Polycyclic Naphthopyran Derivatives

Rh-catalyzed C-H activation of arenes for oxidative annulations with alkynes stands out as a protocol for polycyclic scaffolds. This perspective drives us to disclose herein a rhodium catalyzed regioselective triple annulation of enaminones with hydroxyl-alkynoates via double C-H functionalization for polycyclic naphtho-pyran scaffolds. Secondary coordination of OH in alkynoate dictated the regioselectivity. Initial lactonization occurred chemoselectively on to enamine part via carbo rhodation followed by reductive elimination. This protocol was scalable and has shown high functionality tolerance. KIE studies were done to get insight in to the mechanism, and some downstream transformations were achieved to show the synthetic potential of the method.