Rhodium-Catalyzed Dynamic Kinetic Asymmetric Hydrosilylation

Chiral organosilicon compounds with silicon-stereogenic centers have structural similarities to their isoelectronic carbon analogues,but exhibit significant differences in physical and chemical properties due to the unique properties of the silicon element.In recent years,silicon-stereogenic organosilicon compounds have received widespread attention in the fields of chemical synthesis,materials and biology.However,organosilicon compounds do not exist in nature,so developing an efficient enantioselective synthesis method is a challenging task that needs to be addressed.The strategy for constructing optically pure silicon-stereogenic organosilanes has typically relied on the desymmetrization-based catalytic asymmetric transformation of prochiral or symmetrical silane compounds,which has some limitations in terms of structural diversity synthesis.This thesis focuses on the development of a new strategy for constructing silicon-stereogenic centers,mainly studying the dynamic kinetic resolution of racemic silicon-center organosilicon compounds to develop a new strategy for constructing silicon-stereogenic compounds through dynamic kinetic asymmetric transformations.The specific research findings are as follows:（1）This study has achieved for the first time a rhodium-catalyzed dynamic kinetic asymmetric intramolecular hydrosilylation reaction（Dy KAH）.The authors have successfully developed a new type of chiral phosphoramidite ligand（simplified as Si MOS-Phos）,which has both axial chirality and multiple stereocenters with different functional groups,by optimizing the chiral phosphine ligand framework of Ar-BINMOL-Phos and evaluating it through a large number of asymmetric catalytic hydrosilylation reactions.Under the optimal conditions of Si MOS-Phos and rhodium metal catalysis,the dynamic kinetic asymmetric intramolecular hydrosilylation reaction of racemic mono-hydrosilane was achieved,and chiral silicon-stereogenic benzothiazole compounds were synthesized with high yield and excellent enantioselectivity（up to 89%of yield and up to 92%ee）.（2）In terms of mechanism research,the possibility of the dynamic kinetic asymmetric hydrosilylation reaction with the aid of Si MOS-Phos complex in the presence of Rh catalysis was demonstrated by monitoring the er values of the silicon chiral center compound and the residual silane substrate during the reaction process.Subsequently,the thermal stability and optical properties of Si MOS-Phos in Rh-catalyzed hydrosilylation were further investigated,and it was speculated that only one enantiomer of Si MOS-Phos has suitable steric repulsion and molecular recognition to assist the Rh-catalyzed Dy KAH.Finally,theoretical calculations showed that the acylamide group present in the chiral ligand is crucial for promoting the SN₂substitution of chloride ions to achieve the chiral inversion of the silicon center.In summary,this study reports for the first time a new strategy for preparing silicon-stereogenic heterocycles based on the dynamic kinetic transformation reaction of racemic silicon-center substrates,successfully breaking through the limitations of constructing silicon-stereogenic centers based on prochiral and symmetrical silane substrates.This reaction strategy provides a new pathway for preparing silicon stereocenter compounds and is expected to promote the development of silicon chiral chemistry-related fields.