Visible light-induced Pd-catalyzed cross-electrophile coupling of 2-(pseudo)haloazines

The 2,2′-bis-azaarenes and 2-heteroarylazines are intricately embedded into the medicinal chemistry, coordination chemistry, and materials. However, the synthesis of these heterobiaryls utilizing traditional cross-coupling methods remains challenging owing to the instability of 2-heteroaryl nucleophiles. A general cross-electrophile coupling exploiting the vast libraries of the relatively stable 2-heteroaryl electrophile subunits would represent a significantly advantageous strategy. Herein, we demonstrate a conceptually distinct, visible light induced, Pd-catalyzed cross-electrophile coupling platform for the construction of unsymmetrical 2,2′-bis-azaarenes and 2-heteroarylazines using the corresponding bromides and triflates as coupling partners. The synergistic interplay of light induced and ground state Pd-catalytic cycles is enhanced through the design of new phosphine-based ligands. This Pd-catalyzed cross-electrophile coupling protocol using organic base and mild conditions exhibits wide functional group tolerance and versatility to access broad spectrum of unsymmetrical 2,2′-bis-azaarenes. The efficacy of the transformation has been showcased through the synthesis of a range of 2-(hetero)arylazene cores surmounting the persistent challenges associated with 2-heteroaryl subunits, diversification of peptides and oligosaccharides. Thus, this technology enables a general platform for the synthesis of unsymmetrical 2,2′-bis-azaarenes and other 2-heteroarylazines through the development of new ligands and without involving stoichiometric toxic metals.