Propelling Chan‐Lam Cross‐Coupling Through Photocatalysis and Electrocatalysis: An Update

Abstract Contemporary modes like photocatalysis and electrocatalysis can not only bring about transformations equivalent to the existing conventional Chan‐Lam methodologies but are also compatible with traditionally difficult substrates, particularly electron‐deficient aryl boronic acids. Transition metals like Ir III and Ru II behave as single‐electron oxidants under visible light. Primarily, photocatalyzed Chan‐Lam reactions commences from the usual Cu/Ni‐catalyzed Chan‐Lam reaction mechanism. Simultaneously, the photocatalytic cycle gets initiated from a visible light induced MLCT to produce an excited metal‐complex; which then undergoes SET to facilitate the final oxidation step from Cu I → Cu II of the mechanistic cycle. Photocatalysts can thus circumvent the need of external oxidants. Other interesting reaction mechanisms involving a proton coupled electron transfer (PCET) process, a photocatalytic‐autocatalytic mechanism, a dual‐photoexcitation mechanism are also discussed in this review. Heterogeneous catalysts with a suitable band‐gap also behave as photocatalysts due to creation of electrons and holes on photoirradiation of the metal surface. On the other hand, electrocatalysis plays a significant role in refining the Cu I generated during the reaction and thus grants an improved reaction side‐product profile. Electrocatalyzed Chan‐Lam reactions through the use of pulsed electrochemistry technique and redox mediators are also discussed in the review.