Defluorination Functionalization Reaction Of Trifluoromethyl Olefins

In the development of chemistry,how to transform inert chemical bond into highly active chemical bond has always been a hot issue.In recent years,transition metal catalyzed C-F bond activation has undergone vigorous development.Under the action of chiral ligands,chiral bifluoroalkene compounds with high stereoselectivity can be obtained.However,the widespread use of expensive transition metal catalysts and ligands severely restricts the application of this pathway in production.Recently,the activation of inert chemical bond has made considerable progress and has been widely used in practical production and life,but it also faces many challenges.The most important problem is to achieve its selective conversion.This paper mainly studies the relationship between various alkyl radical precursors and hydrogen atom transfer(HAT)under photocatalysis α-Reaction of trifluoromethylstyrene compounds to generate α-CF3 alkyl radicals,which can occur β-The elimination process of F results in the formation of bifluoroethylene hydrocarbon products.These free radical fragments include:1)Silanecarboxylic acid as a precursor of silyl radical in organic silicon compounds;2)those with certain steric hindrance α-3° Primary amine;3)Metal catalyzed defluorination boronization reaction of trifluoromethyl olefins is as follows:Part 1:Under photocatalytic conditions,silane carboxylic acid reacts with α-The reaction of trifluoroethylene compounds yields bifluoroethylene products.During the reaction process,the photocatalyst(PC=4CzIPN)acts as a receptor,and silane carboxylic acid(R3SiCOOH)generates methyl silyl radicals through the hydrogen atom transfer(HAT)process,α-Production of trifluoromethylstyrene compounds during the reaction processα-CF3 alkyl radical,two free groups can occur β-The elimination process of F ultimately generates bifluoroalkene products.This efficient carbon fluorine bond activation strategy has the characteristics of mild reaction conditions and a wide range of substrates.Part 2:Under photocatalytic conditions,certain active α-3° primary amine and α-The reaction of trifluoroethylene compounds yields bifluoroethylene products.From the perspective of the activation of C-N and C-F bonds,under the action of a photocatalyst(PC=4CzIPN),the activation of a certain steric hindrance α-3° primary amine forms alkyl radicals,which condense with electron rich aromatic aldehydes to form acyl intermediates that are electron deficient α-Trifluoroethylene generation β-The final product generated during the F elimination process.The mild reaction conditions and high efficiency have developed the deamination and defluorination reaction into a relatively mature stage.Part 3:Under copper catalytic conditions,trifluoromethyl alkenes are mixed with bis(pinacol)diboron to achieve their corresponding selective defluoroboronation process,and then subjected to Brown oxidation to construct α-Hydroxydifluoromethylene compounds.The key to this reaction is the formation of corresponding products through defluorinated boronization coupling with various fluorinated olefins.This process is cheap and practical,avoiding the use of precious metal catalysts,complex ligands,and harsh reaction conditions.The obtained difluoromethyl compounds can significantly improve the biological activity and stability of molecules,achieving valuable functionalization.