title: New Insights into Aldol Reactions of Methyl Isocyanoacetate Catalyzed by Heterogenized Homogeneous Catalysts.
abstract: The Hayashi-Ito aldol reaction of methyl isocyanoacetate (MI) and benzaldehydes, a classic homogeneous Au(I)-catalyzed reaction, was studied with heterogenized homogeneous catalysts. Among dendrimer encapsulated nanoparticles (NPs) of Au, Pd, Rh, or Pt loaded in mesoporous supports and the homogeneous analogues, the Au NPs led to the highest yield and highest diastereoselectivity of products in toluene at room temperature. The Au catalyst was stable and was recycled for at least six runs without substantial deactivation. Moreover, larger pore sizes of the support and the use of a hydrophobic solvent led to a high selectivity for the trans diastereomer of the product. The activation energy is sensitive to neither the size of Au NPs nor the support. A linear Hammett plot was obtained with a positive slope, suggesting an increased electron density on the carbonyl carbon atom in the rate-limiting step. IR studies revealed a strong interaction between MI and the gold catalyst, supporting the proposed mechanism, in which rate-limiting step involves an electrophilic attack of the aldehyde on the enolate formed from the deprotonated MI.
authors.affiliation: Department of Chemistry and ‡Kavli Energy NanoScience Institute, University of California , Berkeley, California 94720, United States.|Chemical Science Division and ∥Materials Science Division, Lawrence Berkeley National Laboratory , 1 Cyclotron Road, Berkeley, California 94720, United States.
authors.forename: Rong
authors.identifier: 0000-0002-4171-5964
authors.initials: R
authors.lastname: Ye
authors.affiliation: Department of Chemistry and ‡Kavli Energy NanoScience Institute, University of California , Berkeley, California 94720, United States.|Chemical Science Division and ∥Materials Science Division, Lawrence Berkeley National Laboratory , 1 Cyclotron Road, Berkeley, California 94720, United States.
authors.forename: Jie
authors.initials: J
authors.lastname: Zhao
authors.affiliation: Department of Chemistry and ‡Kavli Energy NanoScience Institute, University of California , Berkeley, California 94720, United States.|Chemical Science Division and ∥Materials Science Division, Lawrence Berkeley National Laboratory , 1 Cyclotron Road, Berkeley, California 94720, United States.
authors.forename: Bing
authors.initials: B
authors.lastname: Yuan
authors.affiliation: Department of Chemistry and ‡Kavli Energy NanoScience Institute, University of California , Berkeley, California 94720, United States.|Chemical Science Division and ∥Materials Science Division, Lawrence Berkeley National Laboratory , 1 Cyclotron Road, Berkeley, California 94720, United States.
authors.forename: Wen-Chi
authors.initials: WC
authors.lastname: Liu
authors.affiliation: Department of Chemistry and ‡Kavli Energy NanoScience Institute, University of California , Berkeley, California 94720, United States.|Chemical Science Division and ∥Materials Science Division, Lawrence Berkeley National Laboratory , 1 Cyclotron Road, Berkeley, California 94720, United States.
authors.forename: Joyce
authors.initials: J
authors.lastname: Rodrigues De Araujo
authors.affiliation: Department of Chemistry and ‡Kavli Energy NanoScience Institute, University of California , Berkeley, California 94720, United States.|Chemical Science Division and ∥Materials Science Division, Lawrence Berkeley National Laboratory , 1 Cyclotron Road, Berkeley, California 94720, United States.
authors.forename: Franco F
authors.initials: FF
authors.lastname: Faucher
authors.affiliation: Department of Chemistry and ‡Kavli Energy NanoScience Institute, University of California , Berkeley, California 94720, United States.|Chemical Science Division and ∥Materials Science Division, Lawrence Berkeley National Laboratory , 1 Cyclotron Road, Berkeley, California 94720, United States.
authors.forename: Matthew
authors.initials: M
authors.lastname: Chang
authors.affiliation: Department of Chemistry and ‡Kavli Energy NanoScience Institute, University of California , Berkeley, California 94720, United States.|Chemical Science Division and ∥Materials Science Division, Lawrence Berkeley National Laboratory , 1 Cyclotron Road, Berkeley, California 94720, United States.
authors.forename: Christophe V
authors.initials: CV
authors.lastname: Deraedt
authors.affiliation: Department of Chemistry and ‡Kavli Energy NanoScience Institute, University of California , Berkeley, California 94720, United States.|Chemical Science Division and ∥Materials Science Division, Lawrence Berkeley National Laboratory , 1 Cyclotron Road, Berkeley, California 94720, United States.
authors.forename: F Dean
authors.initials: FD
authors.lastname: Toste
authors.affiliation: Department of Chemistry and ‡Kavli Energy NanoScience Institute, University of California , Berkeley, California 94720, United States.|Chemical Science Division and ∥Materials Science Division, Lawrence Berkeley National Laboratory , 1 Cyclotron Road, Berkeley, California 94720, United States.
authors.forename: Gabor A
authors.initials: GA
authors.lastname: Somorjai
keywords: Heterogenized homogeneous catalyst; aldol reaction; gold catalyst; mechanism; selectivity; support effect