Copper-Catalyzed Petasis-Type Reaction Enables Efficient Synthesis of C1-Substituted Tetrahydro-β-carbolines

-alkyl dihydro-β-carbolinium (DHβC) ions with aryl/alkenyl boronates through novel copper catalysis. The efficiency and utility of this protocol were demonstrated by a broad substrate scope (51 examples, up to 99% yield), excellent scalability (gram scale), and versatile transformations of products. Mechanistic studies suggest that this process proceeds via a novel mechanism involving a copper-mediated intramolecular single-electron transfer (SET). This novel Petasis-type reaction not only significantly broadens the scope of Petasis reactions but also reveals new mechanistic pathways.