N-Heterocyclic Carbene-Catalyzed Desymmetrization Of Silicon-centered Dialdehydes

Organosilicon compounds belong to one of the most important class of molecules which have been widely used in medicinal chemistry,synthetic chemistry,and materials science.Among them,optically active organosilanes bearing a stereogenic center at the silicon atom have attracted more and more attention because they can be applied as chiral reagents,chiral auxiliaries and chiral catalysts.Traditionally,the construction of Si-stereogenic centers was mainly completed by chiral auxiliaries promoted optical or kinetic resolution of racemic silanes.In the past two decades,due to the vigorous development of transition metal catalysis,a number of methods have been reported to obtain Si-stereocenters by using transition metalcatalysts to mediate the desymmetrization reactions of prochiral silanes.Very recently,the synthesis of silicon-stereogenic organosilanes through organocatalysis has also been developed,but still in its infancy.In this thesis,we mainly focus on the Nheterocyclic carbene(NHC)-catalyzed desymmetrization of silicon-centered dialdehydes to afford a variety of silicon-stereogenic organosilanes with moderate to excellent enantioselectivities.There are three chapters in this thesis.Chapter 1 first briefly introduced some typically useful silicon-stereogenic organosilicon compounds,then intensively introduced the construction of siliconstereogenic organosilanes through optical resolution,kinetic resolution,transition metal catalysis and organocatalysis.Chapter 2 mainly investigated the NHC-catalyzed desymmetric benzoin reaction of silicon-centered dialdehydes,allowing facile access to a variety of dibenzo[b,f]silepin-10-ones possessing 1,4-carbon-and silicon-stereogenic centers with good to excellent yields,moderate to excellent diastereoselectivities,and good to excellent enantioselectivities.This reaction can be amplified to gram-scale,and the products can be further derivatized to other valuable compounds.Chapter 3 mainly explored the NHC-catalyzed desymmetric monoesterification of silicon-centered dialdehydes with alcohols or phenols,providing a series of siliconstereogenic organosilanes with moderate to good yields and good to excellent enantioselectivities.Further scale-up synthesis and derivatization experiments showed that this reaction had potential applicable values.