title: Asymmetric catalysis at the mesoscale: gold nanoclusters embedded in chiral self-assembled monolayer as heterogeneous catalyst for asymmetric reactions.
abstract: Research to develop highly versatile, chiral, heterogeneous catalysts for asymmetric organic transformations, without quenching the catalytic reactivity, has met with limited success. While chiral supramolecular structures, connected by weak bonds, are highly active for homogeneous asymmetric catalysis, their application in heterogeneous catalysis is rare. In this work, asymmetric catalyst was prepared by encapsulating metallic nanoclusters in chiral self-assembled monolayer (SAM), immobilized on mesoporous SiO2 support. Using olefin cyclopropanation as an example, it was demonstrated that by controlling the SAM properties, asymmetric reactions can be catalyzed by Au clusters embedded in chiral SAM. Up to 50% enantioselectivity with high diastereoselectivity were obtained while employing Au nanoclusters coated with SAM peptides as heterogeneous catalyst for the formation of cyclopropane-containing products. Spectroscopic measurements correlated the improved enantioselectivity with the formation of a hydrogen-bonding network in the chiral SAM. These results demonstrate the synergetic effect of the catalytically active metallic sites and the surrounding chiral SAM for the formation of a mesoscale enantioselective catalyst.
authors: Department of Chemistry, University of California, Berkeley, California 94720, USA.
authors: Elad
authors: E
authors: Gross
authors: Jack H
authors: JH
authors: Liu
authors: Selim
authors: S
authors: Alayoglu
authors: Matthew A
authors: MA
authors: Marcus
authors: Sirine C
authors: SC
authors: Fakra
authors: F Dean
authors: FD
authors: Toste
authors: Gabor A
authors: GA
authors: Somorjai
mesh_terms: D000475:Alkenes / Q000138:chemical synthesis* / Q000737:chemistry; D002384:Catalysis; D006046:Gold / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry*; D015394:Molecular Structure; D016062:Porosity; D012822:Silicon Dioxide / Q000737:chemistry; D013499:Surface Properties
chemical_list: D000475:Alkenes; D006046:Gold; D012822:Silicon Dioxide