Asymmetric Palladium-Catalyzed Hydrosilylation Of 1,3-Diynes To Access Silicon-Stereogenic Enynes

In recent years,the syntheses and performance research of silicon-stereogenic compounds have been increasingly emphasized,and have become one of the frontier topics in the fields of synthetic chemistry,medicinal chemistry,and new functional materials.Due to the absence of naturally occurring chiral-at-silicon substances in nature,it is difficult to construct silicon-stereogenic compounds using natural sources of chirality,and the sources are relatively scarce.Chemical synthesis methods are needed to solve this problem.In previous studies,the asymmetric hydrosilylation reaction has been proven to be a feasible synthetic strategy for constructing siliconstereogenic centers.Although it has been reported in the past that chiral organosilicon compounds can be synthesized by using transition metal-catalyzed hydrosilylation reactions,the construction of vinylsilanes containing silicon-stereogenic centers with the aid of palladium catalysis remains a challenging task.Notably,the development of efficient new catalytic systems is highly desired.This thesis focuses on the catalytic construction of silicon-stereogenic centers,and want to develop a new chiral palladium catalytic system around the asymmetric hydrosilylation reaction of 1,3-diyne compounds and dihydrosilane.The author conducts a series of in-depth studies,and the main scientific findings shows as following:(1)By using a new type of phosphoramidite ligand based on a BINOL skeleton with bulky substituents and palladium source,we have achieved the first asymmetric hydrosilylation reaction of 1,3-diynes and dihydrosilanes,successfully constructing enyne compounds with silicon-stereogenic centers.In the specific implementation process,the optimal conditions for the hydrosilylation reaction were optimized by screening the palladium sources,solvents,temperature,and modifying the chiral phosphoramidite ligand based on the BINOL skeleton.In addition,in the study of the substrate scope of the reaction,it was found that the reaction could be applied to the synthesis of a series of silicon-stereogenic enyne compounds with different substituents on the silicon center,which showed good yields,excellent regioselectivity and enantioselectivity(up to 91% yield,99:1 reaction ratio,>99% enantioselectivity).And in the study of downstream transformations of silicon-stereogenic enynes,methylation,oxidation,and cross-coupling reactions of the products with silicon-stereogenic centers were achieved,and the target products obtained with the same high stereoselectivity.(2)In the study of asymmetric palladium-catalyzed hydrosilylation reaction of 1,3-diynes,it was found that the catalytic systems could be applied to the synthesis of macromolecular silylenynes with silicon-stereogenic centers,and the spectroscopic characterizations such as circular dichroism,UV,and scanning electron microscopy were carried out.The experimental results showed that the chiral palladium/phosphorus catalytic system could also be successfully applied to the synthesis of chiral Sipolymers.This method provides a new approach for the synthesis of functional materials with silicon-stereogenic centers.In addition,the mechanism of the related reaction was further explored in this wrok.Through yield kinetic monitoring,nonlinear effects,qualitative and quantitative control experiments,it was found that there was a significant self-catalytic process induced by the aggregation of chiral products in the reaction.The continuous aggregation of chiral silylenyne products could accelerate the reaction process,and the key to achieving excellent enantioselectivity lies in the noncovalent interactions induced by the aggregation of the catalyst and substrate.This discovery has important implications for the activation of Si-H bonds and enhancing enantioselectivity of Pd-catalyzed hydrosilylation.In summary,this work develops a class of structurally novel and chiral phosphine ligands through in-depth study of the asymmetric palladium-catalyzed hydrosilylation reaction of 1,3-diynes.It also provides an efficient catalytic system for the hydrosilylation reaction and a novel method for the synthesis of silicon-stereogenic silylenyne compounds,providing new strategies for the construction of chiral-at-silicon compounds.