Pd(II)-Catalyzed Oxidative Annulation via Double C-H Activations: Synthesis and Photophysical Properties of Bis-Coumarins.

A Pd(II)-catalyzed oxidative annulation reaction of 4-hydroxycoumarin and arylcarboxylic acid via double C-H bond activations has been accomplished for the synthesis of bis-coumarins. This synthetic strategy provides a wide range of structurally diversified bis-coumarins in moderate to good yields with a variety of functional group compatibility. Moreover, photophysical properties of synthesized bis-coumarins have been evaluated, which reveals their interesting fluorescent properties.