Terminal alkynes hydroamination catalyzed by copper nanoparticles

Nitrogen-containing compounds, such as amines, enamines and imines, are valuable and of great industrial and pharmaceutical relevance. The hydroamination (HA) is a reaction that involve the direct formation of a new C-N bond by addition of an amine to an unsaturated CC bond. HA is one of the most atom efficient processes and can be performed under catalysis of a wide range of metals, being especially versatile the late-transition metals.

In this work we present a study of the reaction of HA of terminal alkynes catalyzed by supported-copper nanoparticles, with very low catalyst loading (< 2 mol%) . Through the methodology of our research group, which involve the addition of the support to a suspension of freshly prepared copper nanoparticles, a wide range of terminal alkynes were regioselectively converted to imines by intermolecular HA. Imines were obtained in moderate to quantitative yields, which were then easily reduced to the corresponding amines. Finally, the heterogeneous and low-cost copper catalyst can be reused in several catalytic cycles with no yield and selectivity decrease.