Decarboxylative 3-Indole Methylenation of 4-Aminocoumarin and Application in the Synthesis of Fused Polycyclic Compounds

The decarboxylative indole methylenation of 4-aminocoumarins in the C3-site has been realized with copper promotion using 3-indolyl acetic acids as reaction partners. In addition to providing a practical method for the synthesis of indole methylene-functionalized 4-aminocoumarins, the metal-free intramolecular amination and aromatization have been achieved for the synthesis of complex pentacyclic compounds, namely, coumarin-fused α-carbolines, with broad scope and generally excellent efficiency.