Theoretical and Experimental Studies: Cu(I)/Cu(II) Catalytic Cycle in CuI/Oxalamide-Promoted C–N Bond Formation

In modern Ullmann–Goldberg reactions, cheaper aryl chlorides are poor substrates. Recently, attention has been paid to facile CuI/oxalamide-promoted arylation of heteroatoms (N, O, and S) using cheaper aryl chlorides. However, the mechanism of the reaction and the role of oxalamides have not yet been investigated. In the present investigation, theoretical (density functional theory) and supporting in situ ¹H NMR spectroscopy, UV–vis spectroscopy, Fourier transform infrared spectroscopy, and cyclic voltammetry studies have been performed to provide insight into the various aspects of the mechanism. Five different possible pathways have been investigated. [LCu­(NHNu)] is the active copper catalytic species, in which L (oxalamide) coordinates Cu­(I) through both −CO groups. Our studies show that the reaction follows an outer-sphere single-electron transfer pathway. Moreover, these studies also address the reason for the deactivation of a copper catalyst.