Studies On Difluorocyclopropanation And Its Conversion Reactions Of ?,?-unsaturated Ketones Based On TMSCF₂Br

The methodological study of the introduction of fluorine atoms or fluorine-containing structural fragments into organic molecules is a hot topic in organic synthesis chemistry.Among them,the use of simple,readily available organofluorine reagents combined with the use of new synthesis strategies is an important means of establishing economical,efficient,and innovative synthetic methods.In recent years,the development of difluorocarbene,which can efficiently introduce fluorine atoms or fluorine-containing structural fragments into organic molecules,has been extremely rapid.Not only the use of classical difluorocarbene reagents extends the scope of application of the substrate,but also some new,environmentally friendly difluorocarbene reagents and new reaction forms involving difluorocarbene have been reported.Commercially available bromodifluoromethyltrimethylsilane?TMSCF₂Br?is an efficient,broad-spectrum difluorocarbene reagent,but it is only used as a difluorocarbene source in synthesis.According to its own structural characteristics,the research on the efficient use of this reagent needs to be developed.Based on the fact that TMSCF₂Br is a difluorocarbene source and creatively utilizes the characteristics of both TMS transfer and bromide anion release source,we have mainly studied the series of cascade reactions of TMSCF₂Br with?,?-unsaturated ketones.The thesis is divided into five chapters.The first chapter mainly summarizes the development of difluorocarbene chemistry,the preparation method and application of TMSCF₂Br,and puts forward the basis for this paper.In Chapter 2,we have studied the catalytic ring expansion reactions of TMSCF₂Br with indanones and 2-cyclopentenones.By using TMSCF₂Br as a difluorocarbene source,it also serves as a multi-reaction property of TMS transfer reagent,potential catalytic ion?Br^-,F^-?release sources.The catalytic ring expansion of indanones and 2-cyclopentenones have been realized,and high-regionselectively constructed fluorinated phenolic compounds.In Chapter 3,we have studied the catalytic domino reactions of TMSCF₂Br with methylketenes.Using TMSCF₂Br as a unique difluorocarbene source and its own self-assist strategy,a simple,efficient new method for the construction of?,?-difluorocyclopentanone derivatives has been developed.The reaction conditions are mild,the substrate range is broad,and the functional groups are compatible.The fourth chapter describes the one-pot cascade reaction of TMSCF₂Br with?-methyl ketenes.Based on using TMSCF₂Br as a difluorocarbene source,difluorocyclopropanation of?-methyl ketenes compounds have been realized by its own complete self-assisted strategy,Under copper catalysis,?,?-difluorocyclopentenones have been successfully constructed in one pot.The materials are easily available and the reaction is simple and efficient.In chapter five,we have studied palladium-catalyzed C-S bond activation and isocyanides insertion reaction of?-acyl ketene dithioacetals.With the help of silanes,palladium-catalyzed unique imidization,hydrogenation,aerobic oxidation,intramolecular nucleophilic addition tandem reaction of?-acyl ketene dithioacetals with isocyanides has been achieved,and?-Lactams was efficiently constructed.It was found that the reaction involved an unprecedented aerobic oxidation process of imine intermediates.This reaction provides a new synthetic strategy for the preparation of nitrogen-containing heterocyclic compounds,and extends new nucleophilic coupling partners for palladium-catalyzed C-S bond activation reactions.