Study On The Construction Of Geminal Difluoromethylene Compounds By Rearrangement Reaction Involving Carben

Fluorine-containing compounds are widely used in the fields of materials,agrochemicals and pharmaceuticals.gem-Difluoromethylene（gem-CF₂）not only has the basic characteristics of general fluorinated group,but also can be regarded as the"bioisosteric"of ether oxygen or carbonyl groups,so it has unique physiological activity and medicinal value.Due to the special nature of gem-CF₂ group,it is difficult to introduce this group into organic compounds through conventional synthesis methods.Therefore,the development of simple and efficient introduction methods has been a hot field with full of challenges and opportunities in organic fluorine chemistry.In this thesis,N-sulfonyl-1,2,3-triazoles and N-tosylhydrazones with 3,3-difluoroallyl sulfides were used to synthesize a series of gem-difluoromethylene containing compounds through ylide rearrangement reaction of carbene intermediates.The main contents are as follows:1)We have introduced the gem-difluoromethylene containing compounds and their importance,and reviewed the existing research progress on their synthesis methods.The properties and applications of carbene in organic chemistry are briefly introduced,and the research topic of this thesis is put forward.2)The[2,3]-σrearrangement reaction of N-sulfonyl-1,2,3-triazoles and 3,3-difluoroallyl sulfides have been studied.Using 4-（4-chlorophenyl）-1-tosyl-1H-1,2,3-triazole and（2-bromo-3,3-difluoroallyl）（phenyl）sulfide as model substrates,we have optimized the reaction conditions such as catalyst,solvent and temperature.The optimum reaction conditions were obtained as follows:Rh₂（OAc）₄ as catalyst,DCE as solvent and temperature 120°C.Under this condition,N-sulfonyl-1,2,3-triazole and 3,3-difluoroallyl sulfides,respectively,were expanded to obtain 25 kinds of 1,1-difluoroallyl,aryl and thio-substituted sulfonylimides were obtained in 46%to 89%yields.The gram-scale experiment was also carried out,and the polysubstituted tetrahydropyrrole scaffold compound with important medicinal value was synthesized by two-step conversion of the standard product.3)The[2,3]-σrearrangement reaction of N-tosylhydrazones and 3,3-difluoroallyl sulfides have been studied.Using N’-（4-chlorobenzylidene）-4-methylbenzenesulfonohydrazide and（2-bromo-3,3-difluoroallyl）（phenyl）sulfide as template substrates,we have been optimized the reaction conditions such as catalyst,base and its amount,solvent,temperature,material ratio.The optimum reaction conditions were obtained as follows:Rh₂（esp）₂ as catalyst,1.2equivalents of Cs₂CO₃ as base,DCE as solvent,temperature of 100°C.Under this condition,the substrates of N-tosylhydrazones and 3,3-difluoroallyl sulfide were expanded,respectively,and 30 kinds of 1,1-difluoroallyl and aryl substituted sulfides were obtained with up to 99%yield.The applicability of the method has been verified by one-pot synthesis,gram-scale reaction and further conversion of the obtained product.