Some Investigations On Asymmetric Organocatalysis And Electrochemical Oxidation Reactions Involving Sulfur Dioxide

Sulfones are widely present in biologically active compounds,pharmaceuticals,and organic synthesis.The development of efficient route for the construction of sulfones,especially chiral sulfones,has attracted more and more attention in organic synthesis and drug discovery.In the past decade,outstanding success has been achieved in the synthesis of sulfonyl compounds via sulfur dioxide insertion strategy,due to the mild reaction conditions and high efficiency of these methodologies.However,the application of sulfur dioxide insertion strategy in asymmetric synthesis and electrocatalytic synthesis is rarely developed.This dissertation focuses on the synthesis of various sulfonyl compounds through sulfur dioxide insertion strategy under asymmetric catalysis and electrocatalysis,which is divided into three parts as below:Part 1.Access to sulfonyl-containing axially chiral styrenes via sulfur dioxide insertion process1.A visible light induced asymmetric radical reaction of potassium alkyltrifluoroborates,K₂S₂O₅,and 1-alkynylnaphthalen-2-ols is accomplished.Sulfonyl-containing axially chiral styrenes are produced with excellent enantioselectivity,regioselectivity and good yields.The transformation involves in situ generation of alkylsulfonyl radicals,tandem enantioselective radical addition,and a reduction process of radical species.2.An efficient route toγ-keto sulfones through a metal-free reaction is developed.γ-Keto sulfinate intermediates were generated in situ in the presence of cyclopropanols and DABCO.（SO₂）₂,which further react with electron-deficient olefins or alkyl halides leading toγ-keto sulfones.3.Sulfonyl-containing axially chiral styrenes are constructed through a cinchona alkaloid catalyzed three-component asymmetric reaction of cyclopropanols,DABCO.（SO₂）₂and 1-alkynyl-2-naphthols.Part 2.Access to chiralγ-keto sulfones via photoinduced organocatalytic asymmetric radical sulfonylation with sulfur dioxideA photoinduced three-component asymmetric sulfonylation of potassium alkyltrifluoroborates,DABCO.（SO₂）₂andα,β-unsaturated carbonyl compounds is achieved.The corresponding chiralγ-keto sulfones are generated in moderate to good yields with excellent enantioselectivity under mild conditions.Part 3.Electrochemical oxidative radical sulfonation of olefins with sulfur dioxideSulfonation of olefins through electrochemical synthesis is developed,by using sulfinate as the sulfur dioxide source.Sulfites undergo anodic oxidation,which further react with alcohols to afford sulfonate radicals.Then,sulfonate radicals combine with olefins to provide sulfonation products.