Simultaneous N2 and N3 coordination of inverse triazolyl-pyridine ligands in Ag(i) complexes: synthesis, structure, and application in the A3 coupling reaction to propargylamine under solvent free and low catalyst loading conditions

Traditional methods in synthesizing large-scale propargylamines have various limitations such as low reaction temperature, formation of byproducts and requirement of anhydrous reaction conditions. In recent times, a potent alternative for the synthesis of these crucial scaffolds has been identified as A3-coupling processes (aldehydes, amines, and alkynes), which are generally mediated by a suitable transition metal catalyst. For the further development of catalysts for A3-coupling reactions, we have designed and synthesized two new isomeric inverse triazolyl-pyridine ligands (2 and 3) and their Ag(i) complexes (4 and 5). Complexes 4 and 5 are fully characterized using different spectroscopic techniques including molecular structure determination using single crystal X-ray diffraction studies. The activity of both the complexes was tested on an A3-coupling reaction and it was found that both complexes are highly active. The superior reactivity of the newly synthesized complexes in comparison to the known catalysts can be attributed to the particular electronic properties and coordination of the inverse triazolyl-pyridine ligand.