Study On The Selective Defluorination And Alkylation Of Trifluoromethyl Alkenes And Gem-difluoroalkenes

Due to the strong electron-withdrawing effect of fluorine atoms,fluorine-containing compounds have unique chemical and biological properties,so organic fluorine compounds have a very wide range of applications in medicinal chemistry and agricultural chemistry.However,the high dissociation energy of the C-F bond is the primary challenge to be overcome.With the in-depth study of its structure and properties,many strategies have been developed to achieve the C-F bond dissociation.The radical defluorination reaction induced by visible-light and catalyzed by cheap metals has become a novel subject for the functionalization of it under mild reaction conditions.Among many fluorine-containing compounds,gem-difluoroalkenes are bio-isosteres of carbonyl compounds,with similar electronic effects,and higher metabolic stability.Due to its easy preparation and high reactivity,α-trifluoromethyl alkenes are often used to prepare gem-difluoroalkenes.Therefore,it is very important to study the reaction of these two compounds.In this paper,the selective defluorination and alkylation of α-trifluoromethyl alkenes and gem-difluoroalkenes is achieved through radical.The main content includes the following three parts:The first part: through literature research,summed up The research progress of defluorination functionalization of α-trifluoromethyl alkenes and gem-difluoroalkene in metal and visible light catalytic systems respectively was reviewed.The research direction and subject were determined by comparing and analyzing the research contents of two kinds of fluorinated alkenes.The second part: researched that under the reduction of zinc powder,the alkylation agent NHPI ester generates alkyl radicals,addition toα-trifluoromethyl alkenes,and then eliminates them to obtain alkyl-substituted gem-difluoroalkenes products.Completed the screening of the solvent,metal reducing agent and other conditions of the reaction,the optimal conditions were determined,and then the universality of the substrate was studied under the conditions,as well as the derivatizative exploration,and finally the mechanism of the reaction was explored.The third part: the reaction of alkylation agent Hantzsch esters and gem-difluoroalkenes under visible-light catalysis is studied,and the corresponding alkylation monofluoroalkene compound is obtained by radical-radical coupling.First,the reaction conditions such as photosensitizer,solvent and light source were screened,and the best reaction conditions were obtained.Then the general applicability of the substrate was studied under this condition,and then the sugars was modified with the corresponding product,which proved the practicality of the experimental scheme.Finally,the mechanism of the reaction is explored,and a reasonable and feasible mechanism cycle process is proposed.