Electrophilic trifluoromethylation reactions have been the latest approach to achieve the fluoroalkylation of compounds with newly-discovered reagents, such as the Togni's (1-trifluoromethyl-1,2-benziodoxol-3-(1 H)-one), Umemoto's (S-(trifluoromethyl)dibenzothiophenium tetrafluoroborate), Yagupolskii's (S-(trifluoromethyldiarylsulfonium salts), Shreeve's (S-(trifluoromethyl)dibenzothiophenium triflate), and Shibata's (trifluoromethylsulfoximine salts) reagents. All these reagents produce an electrophilic trifluoromethylating (CF3 (+) ) species that undergoes reaction with nucleophiles. In addition, these latter reactive species (i.e. CF3 (+) ) can undergo electron-transfer (ET) processes affording CF3 (⋅) radicals that expand the scope to substrates other than conventional nucleophiles that can undergo reaction. In this Review, we shall discuss the trifluoromethylation reactions of diverse families of organic substrates of biological interest as a means to comparing the reagents scope and best reaction conditions. Some, though not all, of these reactions require the assistance of metal or organometallic catalysts. Some require additives and catalysts to promote the fluoroalkylation reaction, but invariably all are initiated and carried out by electrophilic trifluoromethylating species.
Different synthetic strategies for accomplishing regio- and stereoselective fluorinations of carbohydrate scaffolds are discussed in light of the biological implications arising from such substitutions.
The photoinduced electron transfer (PET) substitution reaction of electron‐rich aromatic nuclei with perfluoroalkyl Rf groups was carried out in water or aqueous mixtures to render substitution products resulting from replacement of aromatic H atoms with the Rf moiety in good yields (57–88 %). Some mechanistic aspects are discussed, supporting the notion of a PET reaction leading to a classical radical homolytic aromatic substitution (HAS) followed by an electron transfer (ET) and then a proton transfer (PT) sequence. A radical mechanism superimposed on a redox process is proposed to account for product formation. Evidence for the radical cation species (as an initiation event) generated from electron‐rich arenes in the presence of perfluoroalkyl halides is provided by the UV/Vis transient spectra obtained by Nanosecond Laser Flash Photolysis techniques.
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