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Yolk‐Shell‐Mesostructured Silica‐Supported Dual Molecular Catalyst for Enantioselective Tandem Reactions
Author(s) -
Wu Liang,
Li Yilong,
Meng Jingjing,
Jin Ronghua,
Lin Jingrong,
Liu Guohua
Publication year - 2018
Publication title -
chempluschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.801
H-Index - 61
ISSN - 2192-6506
DOI - 10.1002/cplu.201800377
Subject(s) - bifunctional , catalysis , enantioselective synthesis , mesoporous silica , aryl , chemistry , bifunctional catalyst , combinatorial chemistry , mesoporous material , organic chemistry , alkyl
Yolk‐shell‐mesostructured silica was used as a support in the development of an active‐site‐isolated bifunctional catalyst that can mediate a sequential organic transformation. Herein, through immobilization, the location of two catalytic species is controlled: a base functionality is anchored in the channels of the outer silica shell and a chiral ruthenium/diamine functionality is anchored on the inner silica yolk. The result is a yolk‐shell‐mesostructured silica‐supported active‐site‐isolated dual molecule catalyst. Structural analysis through solid‐state carbon 13 C NMR spectroscopy reveals its well‐defined single‐site dual active centers. Electron microscopy investigations disclose its uniformly distributed mesoporous nanoparticles. As envisaged, this bifunctional catalyst enables a controllable aza‐Michael addition/asymmetric transfer hydrogenation catalytic sequence, where the base‐catalyzed aza‐Michael addition of enones and amines to aryl‐substitutedβ ‐secondary amino ketones is followed by a Ru‐catalyzed asymmetric transfer hydrogenation. Various aryl‐substituted γ‐secondary amino alcohols are obtained in high yields and enantioselectivities via this one‐pot enantioselective organic transformation. Furthermore, the heterogeneous catalyst can be applied in a continuous‐flow process, which was shown to be particularly attractive for the practical preparation of aryl‐substituted γ‐secondary amino alcohols in an environmentally friendly medium.