Cu/Pd-Catalyzed Synthesis of Fully Decorated Polycyclic Triazoles: Introducing C-H Functionalization to Multicomponent Multicatalytic Reactions ((MC)2R)

A robust method for the dual-metal-catalyzed combination of organic azides, terminal alkynes, and internal alkynes is reported. The reaction is initiated with a chemoselective copper-catalyzed azide alkyne cycloaddition (CuAAC) followed by a palladium-catalyzed incorporation of an internal alkyne. The simple one-pot procedure introduces C-H functionalization to the growing field of multicomponent multicatalytic reactions ((MC)R-2). With inexpensive CuI and the Herrmann-Beller palladacycle as catalysts, four bonds and two heterocyclic rings are created with HI as the sole byproduct. The broad scope with respect to all components showcases this versatile transformation, leading to a new class of fully substituted polycyclic triazoles. 'H NMR and deuterium-labeling studies provide insight into the rate differences of the copper and palladium steps.