Electrophilic fluorination reagents trifluoromethyl hypofluorite

Trifluoromethyl hypofluorite, CF3OF, the first organic hypofluorite, reacts as if the O-F bond is homolyzed to the trifluoromethoxy radical and a fluorine radical in many reactions, but it has been used effectively as a selective electrophilic fluorination reagent in organic chemistry. It has limited selectivity as a fluorination reagent in inorganic chemistry bnt it can be oxidatively added to numerous compounds. 

Fluoroaromatic compounds 8 are synthesized by reaction of aryltrialkyltin derivatives with electrophilic fluorinating reagents, such as cesium fluoroxysulfate,12,13 trifluoromethyl hypo-fluorite1314 and acetyl hypofluorite,1516 or with elemental fluorine.13 15 18 In Table 4 examples of these reactions arc summarized. 

Several reagents were used for the electrophilic fluorination of indole. The first one used for this aim was trifluoromethyl hypofluorite (CF3OF). Treatment of V-acylindole 1 with trifluoromethyl hypofluorite in CF3CI at -78 °C afforded a mixture of 2-fluoro-3-trifluoromethoxy- and 2,3-difluoroindoline derivatives 2-4 in high combined yield. Subsequent treatment of difluoride 4 with potassium hydroxide in methanol afforded quantitatively 3-fluoroindole 5. Similarly, starting from l-formyl-2-methylindole reaction with trifluoromethyl hypofluorite resulted in formation of 2-methyl-3-fluoroindole 7 in low yield in mixture with 2-methyl-3-trifluormethoxyindole 8 [7]. 

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