Nano and Sub-nano Gold–Cobalt Particles as Effective Catalysts in the Synthesis of Propargylamines via AHA Coupling

Abstract

Titania supported Au–Co catalysts with nano- and sub-nanoparticles, were prepared with 1% Au and different contents of cobalt by one pot deposition precipitation with urea. Monometallic gold and cobalt catalysts were also prepared by the same method for a comparative purpose. The characterization of bimetallic catalyst evidenced the presence of sub-nanoparticles where 50% of cobalt and 40% of gold particles are smaller than 1 nm and the formation Au–Co particles. The results show a positive effect of cobalt on gold particles size and the catalytic activity. The effectiveness of these catalysts in the synthesis of several propargylamines via amine, CH2Cl2 and alkyne coupling (AHA coupling) was demonstrated. Different propargylamines were synthesized with very good yields (71%–88%). A comparative study of monometallic gold, monometallic cobalt and bimetallic gold–cobalt catalysts was investigated. The most efficient catalyst was reused for up to six reaction cycles without significant activity loss.