The exploitation of chirality at silicon in asymmetric catalysis is one of the most intriguing and challenging tasks in synthetic chemistry. In particular, construction of enantioenriched mediem-sized silicon-stereogenic heterocycles is highly attractive, given the increasing demand for the synthesis of novel functional-materials-oriented silicon-bridged compounds. Here, we report a rhodium-catalyzed enantioselective construction of six- and seven-membered triorgano-substituted silicon-stereogenic heterocycles. This process undergoes a direct dehydrogenative C−H silylation, giving access to a wide range of triorgano-substituted silicon-stereogenic heterocycles in good to excellent yields and enantioselectivities, that significantly enlarge the chemical space of the silicon-centered chiral molecules. Further elaboration of the chiral monohydrosilane product delivers various corresponding tetraorgano-substituted silicon-stereogenic heterocycles without the loss of enantiopurity. These silicon-bridged heterocycles exhibit bright blue fluorescence, which would have potential application prospects in organic optoelectronic materials.
A novel catalyst-free addition reaction of thiols to silyl glyoxylates is developed in water, providing an efficient route for the synthesis of α-hydroxysilanes.
Despite
the growing demand for the enantioenriched silicon-stereogenic
silanols in materials science, medicinal chemistry, and modern synthetic
chemistry, the catalytic asymmetric synthesis of which remains a considerable
challenge compared with their carbinol analogues. Herein, a copper-catalyzed
desymmetrization of silanediols for the synthesis of various functionalized
chiral silanols is demonstrated. The reaction features high atom economy,
decent yield with excellent stereoselectivity, and H2 as
the sole byproduct. Key to the success for discrimination of the gem-diol
groups in silanediol relies on an enantioselective σ-bond metathesis
process. Further straightforward elaboration of the enantioenriched
silicon-stereogenic silanols delivers several interesting chiral silane
scaffolds without the loss of enantiopurities.
A direct organocatalytic asymmetric vinylogous aldol reaction of allyl aryl ketones to silyl glyoxylates has been developed through the bifunctional catalyst, giving the α-hydroxysilanes with excellent enantioselectivity (up to 95% ee) and in high yields (up to 96%). The success of this catalytic methodology offers an opportunity to tackle the problems in the nucleophilic addition to acylsilanes. To activate both allyl aryl ketones and acylsilanes, the utilized bifunctional catalyst was an ideal organocatalyst in this unprecedented transformation.
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