Closing the Cycle as It Begins: Synthesis of ortho-Iodobiaryls via Catellani Reaction

Despite the advances in the field of carbon-halogen bond formation, the straightforward catalytic access to selectively functionalized iodoaryls remains a challenge. Here, we report a one-pot synthesis of ortho-iodobiaryls from aryl iodides and bromides by palladium/norbornene catalysis. This new example of Catellani reaction features the initial cleavage of a C(sp(2))-I bond, followed by the key formation of a palladacycle through ortho C-H activation, the oxidative addition of an aryl bromide and the ultimate restoration of the C(sp(2))-I bond. A large variety of valuable o-iodobiaryls has been synthesized in satisfactory to good yields and their derivatization have been described too. Beyond the synthetic utility of this transformation, a DFT study provides insights on the mechanism of the key reductive elimination step, which is driven by an original transmetallation between palladium(II)-halides complexes.