Silicon enantiomeric convergence and Z/E stereocontrolled catalysis of olefins

Professor Chuan He's research group at Southern University of Science and Technology reported an example of asymmetric Si–H/O–H coupling between racemic monohydrosilanes and alcohols in the same catalytic system, simultaneously achieving enantiomeric construction of the silicon chiral center and precise control of the Z/E configuration of the alkene. Through mechanistic studies combined with DFT calculations, the stereopolymerization of silicon chirality and the cis-trans isomerization process of the alkene were elucidated in detail. This reaction exhibits excellent yields and good to excellent enantiomeric selectivity, providing a new scheme for the efficient synthesis of four stereoisomers [( R,Z), (R,E), (S,Z), (S,E)]. The article was published as an open access Research Article in CCS Chemistry, the flagship journal of the Chinese Chemical Society.

Background information:

Stereochemistry is the "soul" of organic molecule function. Whether it's a drug molecule or a functional material, its activity, recognition ability, and optical properties often depend on the molecule's three-dimensional spatial structure. Among the many stereochemical elements, the chiral center and the Z/E configuration of the alkene are particularly crucial. However, how to precisely control both simultaneously in synthesis, especially to efficiently prepare all four stereoisomers [(R,Z), (R,E), (S,Z), (S,E)] from the same starting material , has always been a major challenge in synthetic chemistry.

To address this challenge, the team led by Chuan He at Southern University of Science and Technology achieved enantiomeric aggregation and Z/E selective synthesis of alkenyl siloxanes by using racemic alkyne-substituted monohydrosilanes and various alcohols for enantiomeric aggregation Si–H/O–H coupling. This method enables rapid enantiomeric conversion of monohydrosilanes, simultaneously generating C=C double bonds with specific stereoconfigurations and exhibiting good to excellent enantiomeric selectivity. Preliminary mechanistic studies revealed the crucial role of the alkenyl-Rh intermediate in Si-H activation and the indispensability of chloride ions in the enantiomeric aggregation process. Furthermore, Rh catalysis enabled controllable isomerization of olefin geometry, making the conversion from Z-form to E-form products possible.

Highlights of this article:

1. Killing two birds with one stone: In the same catalytic system, the enantiomeric transformation of silicon chiral centers and the selective synthesis of olefin Z/E configurations are achieved simultaneously.
2. Stereo-divergent synthesis: By adjusting the reaction time, temperature and chiral ligands, all four stereoisomers can be prepared efficiently.
3. 100% atom economy: The reaction conditions are mild and there are no byproducts, which is in line with the concept of green chemistry.
4. Wide substrate applicability: a variety of alcohols and alkynyl silanes can participate in the reaction efficiently, and it is compatible with a variety of functional groups.

Summary and Outlook:

In this study, the authors achieved asymmetric Si–H/O–H coupling of racemic monohydrosilanes with alcohols, while simultaneously completing the enantiomeric aggregation of the silicon chiral center and precise control over the Z/E configuration of the olefin. This method opens a new avenue for the efficient synthesis of structurally diverse silicon chiral Z/E-olefinic silyl ethers with high enantioselectivity and stereoselectivity. This dual precise control over the chirality of the silicon center and the olefin configuration demonstrates the great potential of innovative catalytic strategies in solving complex stereochemical problems. Furthermore, the successful synthesis of all four stereoisomers [(R,Z), (R,E), (S,Z), (S,E)] also provides new schemes for stereochemical research.

This research was recently published in CCS Chemistry. Researcher Chuan He and Assistant Research Professor Jie Ke from Southern University of Science and Technology (SUSTech), and Dr. Yingzi Li from the Institute of Chemistry in Catalonia, Spain, are the corresponding authors. Doctoral students Liexin Wu and Liqing Ren from SUSTech are co-first authors. This work was supported by the National Natural Science Foundation of China and the Shenzhen Science and Technology Innovation Commission.

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About the journal: CCS Chemistry is the Chinese Chemical Society’s flagship publication, established to serve as the preeminent international chemistry journal published in China. It is an English language journal that covers all areas of chemistry and the chemical sciences, including groundbreaking concepts, mechanisms, methods, materials, reactions, and applications. All articles are diamond open access, with no fees for authors or readers. More information can be found at https://www.chinesechemsoc.org/journal/ccschem.

About the Chinese Chemical Society: The Chinese Chemical Society (CCS) is an academic organization formed by Chinese chemists of their own accord with the purpose of uniting Chinese chemists at home and abroad to promote the development of chemistry in China. The CCS was founded during a meeting of preeminent chemists in Nanjing on August 4, 1932. It currently has more than 120,000 individual members and 184 organizational members. There are 7 Divisions covering the major areas of chemistry: physical, inorganic, organic, polymer, analytical, applied and chemical education, as well as 31 Commissions, including catalysis, computational chemistry, photochemistry, electrochemistry, organic solid chemistry, environmental chemistry, and many other sub-fields of the chemical sciences. The CCS also has 10 committees, including the Woman’s Chemists Committee and Young Chemists Committee. More information can be found at https://www.chinesechemsoc.org/.