Biaryls are a key structural motif in compounds with various applications, ranging
from pharmaceuticals to material science, including ligands for organic synthesis.
Given the growing concern about the use of transition metals in organic synthesis in terms
of reaction condition mildness, substituents tolerance, reagents costs and toxicity, and purification
of the products from metal traces, several alternatives have been developed to
overcome the limitations of metal-catalyzed biaryls synthesis. Herein, we review the transition
metal-free approaches to biaryls, which can be divided into metal-free crosscoupling
of aromatics and metal-free benzannulation of aryl-substituted chains, as both
fields have shown an impressive growth in recent years.
Keywords: Biaryls, metal-free, cross-coupling, diels-alder, annulation, oxidative coupling.
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