Amidoxime fibers-copper–catalyzed cross-dehydrogenative coupling of N,N-dimethylanilines and aromatic terminal alkynes

Abstract

A heterogeneous Cu(II)-AOFs catalyst, Cu(II) supported on amidoxime fibers (AOFs), is successfully applied to the cross-dehydrogenative coupling of aromatic terminal alkynes and N,N-dimethylanilines to form propargylamines. The Cu(II)-AOFs catalyst shows high catalytic activity with the yields of the corresponding propargylamines reaching 90% at 70 °C for 4 h without the protection of an inert gas. The Cu(II)-AOFs coordinate with the imine ion intermediate generated during the reaction, making the coupling facile. X-ray photoelectron spectrometer, scanning electron microscope, and energy dispersive X-ray spectroscopy results show that Cu(II) successfully coordinates with N and O atoms on the surface of the fibers with the mutual conversion between monovalent and divalent Cu in the Cu-AOFs being the catalytically active center. The catalyst can be recycled more than four times, and the catalytic activity is not obviously reduced. This process represents a new pathway for the formation of propargylamines using a Cu(II)-AOFs catalyst.