Asymmetric Hydrosilylation Of The β-Silyl Styrenes

Chiral organosilanes occupy a highlighted position in the field of the organic chemistry,and they have widespread applications in silicon-based materials science1,silicon medicinal chemistry2,and organic synthesis.Therefore,it is particularly important to develop general and efficient methods for synthesizing chiral silicon compounds with various structures.In addition,the asymmetric hydrosilation reaction of olefins catalyzed by transition metals can be used to prepare chiral silicon compounds with high regioselectivity and high stereoselectivity.However,there are currently few studies on the asymmetric hydrosilation reaction of 1,2-substituted olefins.In particular,there are few studies on the asymmetric hydrosilation of olefins with silicon-based heteroatoms introduced into the end of the styrene double bond.This thesis uses the asymmetric hydrosilation reaction of β-silyl styrene as a strategy to realize the synthesis of 1,2-chiral disilicon compounds and chiral phenylsilanol.First,we used βtrimethylsilylstyrene as the standard substrate,and screened the commonly used chiral phosphorus ligands,silicon sources,reaction temperature,and reaction solvents that were directly purchased commercially.Finally,we used[PdCl(C3H5)]2,under the catalysis of the chiral spirocyclic monodentate phosphoramidite ligand(R-SIPHOS-PE),trichlorosilane was used as the silicon source,solvent-free,and 0℃ as the optimal reaction conditions to successfully synthesize the corresponding hand For silanol compounds and 1,2chiral disilicon compounds,the ee value of the standard substrate product is as high as 98%,and the yield is 95%.Then the configuration of the product is determined through the corresponding conversion,and the result is obtained through calculation and simulation optimization.The catalyst structure explains the stereoselectivity control in the reaction process and suggests possible reaction mechanisms.Subsequent development was also carried out.The silicon substituents were the substrates of triethyl silicon(SiEt3)and dimethyl phenyl silicon(SiMe2Ph),which can smoothly undergo asymmetric hydrosilation reactions under standard reaction conditions.The conversion rates are all greater than 99%,and the absolute configuration of the product is well controlled,with ee values of 97%and 84%,respectively.Silicon is substituted with dimethyl tert-butyl silicon(SiMe2tBu)substrate,and the absolute configuration of the product is well controlled,with an ee of 85%.For triisopropyl silicon(Sitr3),which has a large steric hindrance,its hydrosilation reaction is Both the conversion rate and the stereoselectivity of the product are very low.From this we conclude that the steric hindrance of the(3-position silicon group of the reaction substrate styrene has a certain effect on the stereoselectivity of the product.In addition,we also studied the influence of aromatic ring substituents on the transformation.Whether it is an electron donating group or an electron withdrawing group,when it is located in the ortho position,the ee value of the product is lower than that of the meta-and para-substituted.This shows that the steric hindrance on the benzene ring has a great influence on the stereo control of the product,that is,the greater the steric hindrance,the more unfavorable the stereo control of the product.Finally,through this synthesis strategy,we completed the synthesis of 1,2-chiral disilicon compounds and chiral silanols in 31.