Multicomponent Synthesis of Iminocoumarins via Rhodium-Catalyzed CH Bond Activation

We herein establish a multicomponent annulation method for the synthesis of valuable iminocoumarins using aryl thiocarbamates, internal alkynes, and sulfonamides as starting materials, which are safe and readily available. The key step is a Rh-catalyzed and sulfur-directed CH bond activation. Preliminary mechanistic investigations suggested that the nucleophilic attack of the sulfonamide on an active iminium cation finally completes the imine segment.