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.

Automated summary

The Rh-catalyzed C-H activation of arenes for oxidative annulations with alkynes is an efficient method to form polycyclic scaffolds. In this study, a regioselective triple annulation of enaminones with hydroxyl-alkynoates via double C-H functionalization was achieved by rhodium catalysis, resulting in polycyclic naphtho-pyran scaffolds. The regioselectivity was controlled by the secondary coordination of hydroxyl group in alkynoate.