Electro-catalytic multicomponent reaction toward asymmetrical biaryls through heteroarylation of in situ generated fused polycyclic heteroaromatics

Biaryls have a wide range of applications in medicines, natural products, materials and ligands for metal catalysts. However, it is a huge challenge to achieve the selective cross-coupling between two different heteroarenes compared to homo-coupling. Moreover, the cross-coupling between different heteroarene groups is usually confined to two simple heteroarenes, which sacrifices the richness of products. Herein, we report a straightforward electrosynthesis of highly complex and asymmetrical biheterocyclic hydrocarbons through sequential site-selective cyclization and cross-coupling of in situ generated fused polycyclic heteroaromatics under metal-, oxidant-, and additive-free conditions. This sustainable and green methodology features mild reaction conditions, excellent H₂O and air tolerance, high atom economy and step economy and good functional group compatibility. Moreover, a possible mechanism has been proposed on the basis of radical-trapping, isotope labeling, KIE, verification of intermediates and cyclic voltammetry experiments.