Studies On Visible Light Catalyzed Reactions Of Ketene Dithioacetals

The comprehensive developments of Green Chemistryistry are good solutions to many global problems,such as environmental pollution and energy shortage.Visible-light is an ideal clean energy with abundant source.The conversions and utilizations of visible light meet the requirements of sustainable development and have been widely applied in organic transformations.In most cases,the visible-light photoredox catalyzed reactions possess the advantages,such as mild reaction conditions,atom-economic,and high selectivity.With unique reaction mechanism,visible-light photoredox catalyzed reactions have successfully applied to many reactions that have been difficult by thermochemistry.Ketene dithioacetals are a kind of important intermediates in organic synthesis.They can be used in many reactions for their functional group multiplicity and special stereoelectronic effects and they could react with electrophilic reagents,nucleophilic reagents and free radicals.In this thesis,based on the unique reaction mechanism of visible-light catalysis,the studies on visible-light photo catalyzed reactions of ketene dithioacetals is aiming to develop new reactions and new synthetic methods.The thesis is divided into five chapters.Chapter 1 illustrates the characteristics of photochemistry and several important works from visible-light catalysis base on alkenes.Then,the thesis proposal is presented in chapter two.In the third chapter,the first example of visible-light photoredox-catalyzed C(sp~2)–H/C(sp~2)–H cross-coupling hydrogen-evolution reaction between two kinds of alkenes was described.The reaction can be carried out using photocatalyst and cobalt dual catalyst,and a series of 1,3-dienes were constructed.It was found that sunlight could also induced the reaction to run gram-scale synthesis under ambient conditions.In the fourth chapter,visible-light induced sulfur-alkenylation of alkenes,including both activated and unactivated alkenes is described.This sulfur-alkenylation reaction involves the visible-light induced conversion of a ketene dithioacetal to the thiavinyl 1,3-dipole intermediate.And it is a novel,high selectivity and tolerance strategy for alkenes difunctionalization.Furthermore,it is also an efficient approach for the late-stage functionalization of natural products and complex molecules.The fifth chapter conducts an in-depth and comprehensive study on the mechanisms involved in Chapters 3 and 4 through a variety of experiments and tests.The researches confirm that ketene dithioacetals can be used as different intermediate forms under visible light.These discoveries are significant and can find potential application.