Molecular Hybrid Catalysts in Ni/Photoredox C–N Coupling: Comparison of “in Batch” and “in Flow” Irradiation Techniques

Abstract

Molecular hybrid catalysts [(ppy)₂Ir(BL)](PF₆), [(dFCF₃)Ir(BL)](PF₆), and [(bpy)₂Ru(BL)](PF₆)₂ (where BL = N,N-di(pyridin-2-yl)-1,10-phenanthrolin-4-amine), have been investigated in Ni-catalyzed C(sp²)–N coupling under visible light irradiation. The impact of the irradiation method—“in batch” or “in flow”—on the activity of hybrid and known dual catalytic systems was initially examined. The hybrid Ru(II) system demonstrated superior efficiency “in flow” compared to dual catalytic systems. The influence of the chelating moiety on the photophysical and electrochemical properties of the photocatalysts was analyzed to elucidate the observed catalytic activity. The hybrid photocatalysts could be utilized for the successful arylation of aromatic or aliphatic amines with moderate to excellent yields (21 examples), ranging from 33% to 91%. Hybrid photocatalysts facilitated the coupling of 4,7-dichloroquinoline and 5-iodopyridin-2-amine with piperazine in the synthesis of precursors for piperaquine and ribociclib.