Microenvironment modulation of cuprous cluster enables inert aryl chlorides activation in single-molecule metallaphotoredox amination

Abstract

Amination of aryl halides is an important tool in organic synthesis and the activation of inert aryl chlorides is particular difficult. We herein report the first study of aromatic microenvironment modulation of cuprous clusters as single-molecule metallaphotocatalysts (SMPs) for direct phneyl chloride activation in CN coupling reactions. Selenoether L1 was designed to afford aromatic microenvironment with ferrocenyl and phenyl groups. The cuprous cluster [Cu2I2(L1)] (C1) was proved to be an effective white light-driven SMP, successfully catalyzing the amination of aryl halides with carbazole. This method showed a diverse substrate scopes of aryl halides with electronical and structural variety, affording the highest yield of 63% for 4-chlorobenzonitrile. X-ray crystallographic, in situ electron paramagnetic resonance (EPR) spectroscopic study and density functional theory (DFT) calculations demonstrated that the aromatic microenvironment in C1 promoted the effective intermolecular electron transfer via π-π interactions between SMPs and aryl halides. Interestingly, the mechanism of the amination was dependent on the substrates applied. A single electron transfer (SET) and formation of Cu2+ intermediate was found when Ph-I/Ph-Br were applied, while an energy transfer (EnT) route with Cu3+-intermediate was identified when Ph-Cl substrates were used.