Ligand effect on the CuI-catalyzed C–S coupling reaction: A density functional theoretical study

The mechanism of C–S coupling reaction from benzenethiol and 1-bromo-4-methoxybenzene to (4-methoxyphenyl)(phenyl)sulfane catalyzed by CuI/BtH has been investigated by using density functional theory (DFT). The co-catalytic effect of the ligand benzotriazole (BtH) was analyzed in details based on a previous experiment reported by Verma that a general and efficient C–S coupling reaction by means of inexpensive catalysts CuI/BtH (Verma et al., 2007). In order to provide comparative data, the structures have been optimized at the B3LYP/6-31+G(d) level in the gas phase and in solution, N,N-dimethyl formamide being the solvent. Our calculated results interpreted that the ligand of BtH can significantly promote the C–S coupling reaction, i.e., reduce the energy barriers in the steps of the C–S coupling and the CuBr dissociation. Furthermore, the mechanism we proposed can be extended to other C–S coupling reaction catalyzed by Cu(I) complexes.