Metal-free regioselective CH chalcogenylation of coumarins/(hetero)arenes at ambient temperature

A novel, practical and metal-free approach for the regioselective selenation of coumarins employing (bis(trifluoroacetoxy)iodo)benzene (PIFA) at room temperature is presented. The developed method is suitable for a wide substrate scope and affords 3-selenyl coumarins in good to excellent yields with high selectivity. A radical mechanism is proposed for this new transformation. Furthermore, the application of sulfenylation with coumarines and selenation with other (hetero)arenes in this transformation is successful. A novel and practical method for the direct regioselective chalcogenylation of coumarins at the C3-postion and selenation of other (hetero)arenes has been achieved using PIFA as a promoter at room temperature.