Photoinduced Synthesis of C3-Arylated 7-Aminocoumarins with Aryl Iodides

C3-Arylated 7-aminocoumarins have found extensive applications as fluorescent probes and laser dyes. In this study, we report a photoinduced synthesis of 3-aryl-7-diethylaminocoumarins using readily available aryl iodides. The proposed mechanism involves a photoinduced single electron transfer process between aryl iodides and 7-diethylaminocoumarins in their first singlet excited states (S₁), leading to the formation of aryl radicals that are crucial for the C3-arylation reaction. The resulting C3-arylated 7-diethylaminocoumarins exhibit distinct fluorescence quantum yields in the solid state and in solution, which are significantly influenced by the electronic properties of the C3-aryl groups.