Ag(I) complexes of benzimidazol-2-ylidene ligands: a study of catalytic efficiency towards three-component coupling reactions

The N-heterocyclic carbene (NHC)-Ag(I) complexes 3a-c were synthesized from benzimidazolium chlorides (2a-c = NHC center dot HCl), incorporating benzyl derivatives and a 2-methoxyethyl group (a: N-3 = 2,4,6-trimethylbenzyl; b: N-3 - 2,3,5,6-tetramethylbenzyl; c: N-3 - pentamethylbenzyl). The compounds were characterized by spectroscopic and elemental analyses. The synthesized NHC-Ag(I) complexes (3a-c) were tested as catalysts for the catalytic three component coupling reaction of aldehyde, alkyne, and amine to propargylamines in various solvents. All complexes were active catalysts for catalytic three-component coupling reactions with good yields under neat and mild conditions (after 4 h, yields of up to 94%).