Difluorocarbene-derived Trifluoromethylselenolation Of Benzyl Halides

The difluorocarbene plays an important role in organfluorine chemistry.We have developed a difluorocarbene reagent previously,difluoromethylene phosphobetaine Ph₃P⁺CF₂COO^-?PDFA?.We found that difluorocarbene could undergo sulfuration with elemental sulfur to give thiocarbonyl fluoride?S=CF₂?.This unprecedented finding may open up new opportunities for the chemistry of difluorocarbene.There are only a few reports about difluorocarbene reacting with nonmetallic elements so far,which we think is a new reaction type.Of course it's benefical for organfluorine chemistry.There are some similar properties between Se and S because they're cognate elements.In this thesis,we mainly discuss the reaction between difluorocarbene and Se in order to develop a novel method of trifluoromethylselenolation.We developed a method about difluorocarbene-derived trifluoromethylselenolation of halides.Firstly,difluorocarbene was released by the decarboxylation of PDFA under heating conditions.Then difluorocarbene reacted with F^-,Se and CuI to give a highly active intermediate--CuSeCF₃.The intermediate reactedwithhalidesquicklytoproducethetargetmaterialof trifluoromethylselenolation.It's propitious to get the target material under mild conditions for benzyl chloride and benzyl bromide.However,it's nonnegligible of steric effect.Yield is lower when substituent group at the ortho-than meta-or para-position.Futhermore,yield decreased significantly when secondary halogenates replaced primary halides.It's necessary to improve the tolerance of the trifluoromethylselenolation.