Alkyne hydroamination is widely used in the pharmaceutical industry to prepare imines and is often catalyzed by gold nanoparticles. While the mechanism of hydroamination on a gold surface is not understood, analysis of homogeneous reaction mechanisms suggests that protonation and deprotonation steps are present in the catalytic cycle. We prepared alkylamine-functionalized, hollow, mesoporous silica shells containing encapsulated gold nanoparticles to determine whether the colocalization of ligands containing labile hydrogens and the reactive gold surface would improve catalyst performance. The chemical structure of the grafted alkylamines was characterized with <sup>13</sup>C solid-state, magic angle spinning, nuclear magnetic resonance spectroscopy (MAS-NMR) and Fourier-transform infra-red spectroscopy. The loading of the alkylamine was further quantified with thermogravimetric analysis and suggested that the heterogeneous catalyst was approximately 20 % alkylamine by weight. We calcined an aliquot of the catalysts to investigate the significance of alkylamine functionalization on the hydroamination of 1-octyne and monitored the reaction with quantitative nuclear magnetic resonance spectroscopy at 360 K in a series of batch reactions. The results suggest that the colocalization of grafted alkylamines significantly improves catalyst performance when compared to the calcined embedded nanoparticles. Further studies will investigate the catalytic properties of gold nanoparticles embedded in silica containing grafted alkylguanidinium and alkylimidazole ligands, which mimic basic, histidine and arginine residues, respectively. The grafting of organic promoters to support materials offers additional strategies to tailor catalytically active surface properties.

Promotion effect of alklyamine functionalized silica on embedded gold nanoparticle hydroaminations

255th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.