Immobilized Gold Nanoparticles Prepared from Gold(III)-Containing Ionic Liquids on Silica: Application to the Sustainable Synthesis of Propargylamines

A cycloaurated phosphinothioic amide gold(III) complex was supported on amorphous silica with the aid of an imidazolium ionic liquid (IL) physisorbed in the SiO2 pores (SiO2-IL) and covalently bonded to the SiO2 (SiO2@IL). Gold(0) nanoparticles (AuNPs) were formed in situ and subsequently immobilized on the SiO2-IL/SiO2@IL phase. The resulting catalytic systems Au-SiO2-IL and Au-SiO2@IL promoted the solvent-free A(3) coupling reaction of alkynes, aldehydes, and amines in high yields under solvent-free conditions with very low catalyst loading and without the use of additives. The Au-SiO2@IL catalyst showed good recyclability and could be reused at least five times with yields of propargylamines of >= 80%. This synthetic method provides a green and low cost way to effectively prepare propargylamines. Additionally, P-31 high resolution magic angle spinning (HRMAS) NMR spectroscopy is introduced as a simple technique to establish the Au loading of the catalyst.