Metal-Catalyzed Reductive Coupling of Aryl Halides beyond Premetalated Reagents or Metallic Reductants: Biaryl Formation

Biaryl motifs figure prominently in commercial pharmaceutical and agrochemical ingredients and are used widely in organic optoelectronic materials. Traditional palladium-catalyzed cross-coupling reactions, such as Suzuki, Negishi and Stille couplings, are powerful methods for aryl-aryl bond formation, but their reliance on premetalated reagents poses practical limitations. As most arylmetal reagents derive from the corresponding aryl halides, considerable effort has been devoted to the development of direct catalytic aryl halide reductive couplings. However, most methods require metallic reductants. In this monograph, metal-catalyzed aryl halide reductive homocouplings (Ullmann reactions) and cross-couplings mediated by nonmetallic reductants are surveyed.