Ruthenium-catalyzed C-H oxygenation of Coumarin Benzenoid Ring

Coumarins represent a versatile class of heterocycles of great importance in drug discovery and the development of functional materials due to their wide range of biological and technological properties.[1][2] Although classical synthesis methods are efficient, the harsh conditions they require have driven the search for new synthetic strategies. In this context, C–H activation has emerged as an advantageous approach, offering fewer synthetic steps and readily available starting materials. However, C–H functionalization of the benzenoid ring of coumarins remains rare and largely limited to the C6 and C8 positions, leaving the C5 position unexplored.[3] Therefore, this work aims to develop a ruthenium-catalyzed methodology for the selective C-H oxygenation at the C5 position of the coumarin benzenoid ring through a directing group-assisted strategy. This synthetic strategy avoids pre-functionalization by directly activating C-H bonds, enabling rapid late-stage diversification of the coumarin scaffold. Preliminary studies identified suitable conditions for the desired transformation.