A rhodium-catalyzed tandem enantioselective
C–H silylation/alkene
hydrosilylation of dihydrosilanes, which enables the streamlined construction
of a wide range of silicon-stereogenic silanes, is successfully developed.
This process involves a SiH2-steered highly enantioselective
C–H silylation to furnish the corresponding desymmetric monohydrosilanes,
which are subsequently trapped with alkenes in a stereospecific fashion
to build functionally diverse asymmetrically tetrasubstituted silanes.
This general strategy combines readily available dihydrosilanes and
alkenes to construct various enantioenriched silicon-stereogenic silanes,
including 9-silafluorenes, Si-bridged ladder compounds, and benzosilolometallocenes,
in a single step with good to excellent yields and enantioselectivities.
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 rhodium-catalyzed
enantioselective construction of triorgano-substituted
silicon-stereogenic siloxanes and alkoxysilanes is developed. This
process undergoes a direct intermolecular dehydrogenative Si–O
coupling between dihydrosilanes with silanols or alocohols, giving
access to a variety of highly functionalized chiral siloxanes and
alkoxysilanes in decent yields with excellent stereocontrol, that significantly expand the chemical space of the silicon-centered
chiral molecules. Further utility of this process was illustrated
by the construction of CPL-active (circularly polarized luminescence)
silicon-stereogenic alkoxysilane small organic molecules. Optically
pure bis-alkoxysilane containing two silicon-stereogenic centers and
three pyrene groups displayed a remarkable g
lum value with a high fluorescence quantum efficiency (g
lum = 0.011, ΦF = 0.55), which
could have great potential application prospects in chiral organic
optoelectronic materials.
Intermolecular C−H silylation for the synthesis of acyclic silanes bearing a silicon‐stereogenic center in one enantiomeric form remains unknown to date. Herein, we report the first enantioselective intermolecular C−H silylation of heteroarenes for the synthesis of acyclic silicon‐stereogenic heteroarylsilanes. This process undergoes a rhodium‐catalyzed direct intermolecular dehydrogenative Si−H/C−H cross‐coupling, giving access to a variety of acyclic heteroarylated silicon‐stereogenic monohydrosilanes, including bis‐Si‐stereogenic silanes, in decent yields with excellent chemo‐, regio‐, and stereo‐control, which significantly enlarge the chemical space of the optically active silicon‐stereogenic monohydrosilanes.
Asymmetric Catalysis An enantioselective intermolecular C−H silylation of heteroarenes for the synthesis of acyclic Si‐stereogenic silanes is reported by Chuan He et al. in their Communication (e202117820).
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