Unlocking the potential of water-soluble gold(i)–NHC complexes: unveiling the role of carboxylic acid in cycloisomerization of alkynyl amino acid derivatives

Abstract

Hydrocarboxylation of alkyne-containing amino acid derivatives using water-soluble gold(I)–NHC complexes in an aqueous biphasic system at room temperature is described. Addition of silver salts is not required as the carboxylic acid group of the substrate is responsible for the activation of the gold catalyst at room temperature. Our results confirm that the steric bulk of the N-heterocyclic carbene ligands is an important factor in both the stability and the catalytic activity of gold(I) complexes in aqueous medium, and consequently in the recycling (at least 15 times without any loss of activity). The catalytic activity of our most active water-soluble gold(I)–NHC complex has been demonstrated in the cycloisomerization of amino acids derivatives with terminal and internal alkynes in aqueous media at room temperature.