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. 2021 Feb 23;12(1):1249.
doi: 10.1038/s41467-021-21489-6.

Enantioselective construction of six- and seven-membered triorgano-substituted silicon-stereogenic heterocycles

Shuyou Chen #  1 , Delong Mu #  1 , Pei-Lin Mai  1 , Jie Ke  1 , Yingzi Li  1 , Chuan He  2
Affiliations

Enantioselective construction of six- and seven-membered triorgano-substituted silicon-stereogenic heterocycles

Shuyou Chen et al. Nat Commun. .

Abstract

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.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Fig. 1
Fig. 1. Construction of silicon-containing π-conjugated molecules.
a Representative silicon-containing π-conjugated molecules. b Asymmetric synthesis of six-membered tetraorgano-substituted Si-stereogenic silanes (previous work). c Enantioselective construction of six- and seven-membered triorgano-substituted Si-stereogenic heterocycles (this work).
Fig. 2
Fig. 2. Development of reaction conditions.
Conditions: 1a (0.1 mmol), [Rh(cod)Cl]2 (1 mol%), ligand (3 mol%), in 1.0 mL solvent under Argon atmosphere. The yield was determined by 1H NMR using CH2Br2 as internal standard, yield in brackets is isolated yield. The ee values were determined by chiral HPLC.
Fig. 3
Fig. 3. Scope of six-membered triorgano-substituted silicon-stereogenic heterocycles.
Reaction conditions: 1 (0.1 mmol), [Rh(cod)Cl]2 (1 mol%), L1 (3 mol%) in toluene (1 mL) at 70 °C for 6 h. a Reaction was performed at 5 mmol scale. b L5 was used as ligand. c [Rh(cod)Cl]2 (4 mol%), L1 (8 mol%) was used. d [Rh(cod)Cl]2 (2 mol%), L1 (4 mol%) in toluene (1 mL) at 60 °C for 8 h. e [Rh(cod)Cl]2 (2 mol%), L1 (6 mol%) was used. f L7 was used as ligand. X-ray crystallographic analysis of 2j allowed to determine the absolute configuration; and configurations of the products 2 were assigned by analogy.
Fig. 4
Fig. 4. Scope of seven-membered triorgano-substituted silicon-stereogenic heterocycles.
Reaction conditions: 3 (0.1 mmol), [Rh(cod)Cl]2 (1 mol%), L3 (3 mol%) in toluene (1 mL) at 100 °C for 12 h.
Fig. 5
Fig. 5. Derivatization of the Si-stereogenic heterocycles.
Reaction conditions: a [Rh(cod)Cl]2 (2 mol%), (racemic)-Josiphos L1 (4 mol%), vinyl ether (2.0 equiv), toluene, 60 °C, 12 h, de = diastereomic excess. b Pt(dvds) (10 µL, 0.1 M in xylene), 1,2-diphenylacetylene (2.0 equiv), toluene, 40 °C, 12 h. c Pd(tBu3P)2 (2 mol%), 4-iodoanisole (2.0 equiv), K3PO4 (3.0 equiv), NMP, rt, 12 h. d [Rh(cod)Cl]2 (2 mol%), (racemic)-Josiphos L1 (4 mol%), acetone (2.0 equiv), toluene, 60 °C, 12 h. e [Rh(cod)Cl]2 (2 mol%), (racemic)-Josiphos L1 (4 mol%), vinyl ferrocene (2.0 equiv), toluene, 60 °C, 12 h. X-ray crystallographic analysis of 6a allowed to determine the absolute configuration; and configurations of the products 4 were assigned by analogy.
Fig. 6
Fig. 6. Photophysical properties investigations.
a Fluorescence images of selected silicon-bridged heterocycles (λex = 365 nm). b Absorption spectra of selected silicon-bridged heterocycles in CHCl3 (10−5 M). c Emission spectra of selected silicon-bridged heterocycles in CHCl3 (10−5 M). d CD (circular dichroism) spectra of compound (R)-4d (purple line, 91% ee) and (S)-4d (green line, 88% ee) in CHCl3 (2.0 × 10−4 M) at room temperature. e CPL (circular polarized luminescence) spectra of compound (R)-4d (purple line, 91% ee) and (S)-4d (green line, 88% ee) in CHCl3 (2.0 × 10−3 M) at room temperature, excited at 339 nm. f glum (Luminescence dissymmetry factor) values-wavelength curve for (R)-4d (purple line, 91% ee) and (S)-4d (green line, 88% ee).
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