Isothiourea-catalyzed Desymmetrization Of Silicon-centered Bisphenols

In the past few decades,organosilicon compounds have been broadly applied in the fields of synthetic chemistry,medicinal chemistry and materials science due to their unique advantages in stability,solubility,toxicity and other aspects.Recently,along with the new development of organosilicon chemistry,optically active organosilanes bearing a stereogenic center at the silicon atom have attracted more and more attention because they can be used as chiral auxiliaries,chiral precursors and chiral catalysts in asymmetric synthesis.However,unlike its carbon congener,which can be prepared through diverse routes,the asymmetric construction of a chiral silicon center is much more challenging.Traditional methods to access silicon-stereogenic silanes are through chiral auxiliaries or reagents promoted optical or kinetic resolution of racemic silanes.In recent years,a series of transition metal-catalyzed desymmetrization reactions of prochiral silanes have been developed.However,the synthesis of silicon-stereogenic organosilanes through more environmentally benign organocatalysis is still rarely developed.In this thesis,we mainly focus on the isothiourea-catalyzed desymmetrization reaction of silicon-centered bisphenols to afford a variety of silicon-stereogenic organosilanes with moderate to excellent enantioselectivities.There are two chapters in this thesis.Chapter 1 first briefly introduced the applications of some chiral silicon compounds in material physics,pharmaceutical chemistry and asymmetric synthesis,then intensively introduced the construction of silicon-stereogenic organosilanes through optical resolution,kinetic asymmetric conversion/kinetic resolution,transition metal catalysis and organocatalysis.Chapter 2 first summarized the recent progress on the isothiourea-catalyzed desymmetrization of bisphenols or glycols to afford optically active compounds,then mainly investigated the ITU-catalyzed monoacylation of silicon-centered bisphenols with 2,2-diphenylacetic pivalic anhydride,leading to silicon-stereogenic organosilanes with moderate to high yields and moderate to excellent enantioselectivities.This reaction can be amplified to gram-scale,and the products can be further derivatized to other valuable compounds.