SCHEDULED MAINTENANCE
A PEG/copper(i) halide cluster as an eco-friendly catalytic system for C–N bond formation†
*a
Dun-Ru
Zhu
*d
Abstract
The catalytic activities of eight copper(I) halide clusters assembled from copper(I) halide and ferrocenyltelluroethers, 1–8, were investigated in C–N formation under various conditions. A catalytic procedure using poly(ethylene glycol) (PEG-400) as a greener alternative organic solvent has been developed. The PEG-400/5 system can achieve 99% targeted yield with a mild reaction temperature and short reaction time. After the isolation of the products by extraction with diethyl ether, this PEG-400/cluster system could be easily recycled. Spectroscopic studies elucidate a stepwise mechanism: firstly, proton-coupled electron transfer (PCET) involving the transfer of an electron from Cu+ and a proton from imidazole results in the formation of a labile penta-coordinated Cu2+ and aryl radical; the following effective electron transfer from the ferrocene unit reduces Cu2+ and forms the target product; finally, the ferrocenium unit is reduced by the I− anion. The merits of this eco-friendly synthesis are the efficient utilization of reagents and easy recyclability.
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