Study On Direct Trifluoromethylation Of Arenes And Decarboxylative Trifluoromethylation Of Aromatic Carboxylic Acids

Owing to the special physical and chemical properties of trifluoromethyl,the introduction of trifluoromethyl group into aromatic compounds has become a hot topic in the field of organic synthesis.At present,trifluoromethylated aromatics have been widely used in medicine,pesticide and dye.However,aromatic trifluoromethylation reactions have been reported,most of which required the use of expensive trifluoromethylating reagents or metal catalysts.Therefore,the development of low cost and environmentally friendly aromatic trifluoromethylation methods is of great significance.Our research includes two parts: the investigation on direct trifluoromethylation of aromatics and decarboxylative trifluoromethylation of aromatic carboxylic acids under mild conditions.Part I: As a kind of commonly used initiators,persulfides have been widely used in radical reactions,and it is more safe and stable compared with organic peroxides.In the initial attempt,1,3,5-trimethoxybenzene was used as substrate,CF3SO2 Na as CF3-source and Na2S2O8 as initiator,the trifluoromethylated product was obtained.The optimization experiments indicated that the desired product could be achieved at an isolated yield of 98%.Then the scope of substrates were examined,and it was found that the selected substrates could be converted into corresponding products in moderate to excellent yields.In addition,this method tolerates a wide range of functional groups.Compared with the reported trifluoromethylation reactions,our method has the advantages of compatible with water,environmentally friendly,mild conditions,low cost and scaleable.Part II: When the first part work was conducting,we have unexpectedly found that 2,4,6-trimethoxybenzoic acid could be converted to decarboxylative trifluoromethylation product after a long reaction time.The optimization experiments indicated that the desired product could be achieved at an isolated yield of 77%.Then the scope of substrates were examined,and it was found that the strong electron-rich substrates could be converted into corresponding products in moderate to excellent yields.Compared with the reported decarboxylative trifluoromethylation reactions,our method has the advantages of compatible with water,environmentally friendly,mild conditions and scaleable.