Study On The Defluorination Functionalization Reaction Of Trifluoromethyl Alkynes Based On β-F Elimination

With the increasing demand for new organic fluorine compounds in the fields of medicine and materials,organic fluorine chemistry has developed rapidly.In recent years,the defluorination functionalization of fluorine-containing compounds has a good application prospect.Because it not only provides the possibility of synthetic diversity for inert C-F bonds,but also provides a novel synthetic route for fluorine-containing functional molecules that are difficult to prepare by conventional methods.However,in recent years,the field of defluorination functionalization of fluorine-containing compounds has progressed relatively slowly,and the types of reactions currently achieved are extremely limited.The main reasons are the following two aspects:1)Because the high bond dissociation of the C-F bond can make the C-F bond quite inert,its activation is more difficult than other carbon-halogen bonds.2)The selective control of C-F bond activation of polyfluorinated compounds is difficult to achieve.Because after a C(sp~3)-F bond in the fluorine-containing functional group is broken,the dissociation energy of the remaining C(sp~3)-F bond will be reduced,so it is quite difficult to avoid excessive defluorination,especially for trifluoromethyl compounds.In this context,we carried out the selective defluorination functionalization reaction of trifluoromethyl alkynes based onβ-F elimination.This reaction has the following advantages:1)By regulating the activity and selectivity of the reaction,the selective cleavage of a C(sp~3)-F bond in the trifluoromethyl group can be achieved without excessive defluorination.2)Realize regioselective hydrodefluorination reaction.This selectivity is regulated by the ligand.When the ligand is the bidentate nitrogen ligand 4.4-diphenyl-1.10-phenanthroline,gem-difluoroalkene is generated;If it is replaced with the monodentate phosphorus ligand tricyclohexylphosphine,difluoromethyl olefin is generated.We speculate that this selectivity is caused by the steric hindrance of the ligand and the electronic effect.3)Through the capture of the key intermediate 1a’and deuterated isotope experiments,we infer that the reaction has undergone multiple additions of boron-copper(I)species to unsaturated bonds and protonation processes,and finally the corresponding hydrodefluorination products are selectively synthesized.In summary,this article provides a high-efficiency,mild reaction condition and selective synthesis of gem-difluoroolefin compounds and difluoromethyl olefin compounds.