The deoxyfluorination of alcohols is a fundamentally important approach to access alkyl fluorides, and thus the development of shelf‐stable, easy‐to‐handle, fluorine‐economical, and highly selective deoxyfluorination reagents is highly desired. This work describes the development of a crystalline compound, N‐tosyl‐4‐chlorobenzenesulfonimidoyl fluoride (SulfoxFluor), as a novel deoxyfluorination reagent that possesses all of the aforementioned merits, which is rare in the arena of deoxyfluorination. Endowed by the multi‐dimensional modulating ability of the sulfonimidoyl group, SulfoxFluor is superior to 2‐pyridinesulfonyl fluoride (PyFluor) in fluorination rate, and is also superior to perfluorobutanesulfonyl fluoride (PBSF) in fluorine‐economy. Its reaction with alcohols not only tolerates a wide range of functionalities including the more sterically hindered alcoholic hydroxyl groups, but also exhibits high fluorination/elimination selectivity. Because SulfoxFluor can be easily prepared from inexpensive materials and can be safely handled without special techniques, it promises to serve as a practical deoxyfluorination reagent for the synthesis of various alkyl fluorides.
A novel Friedel–Crafts-type alkylation of arenes to access valuable 1-fluoroalkyl-1,1-biaryl compounds is established under mild conditions. The key to success is the efficient generation of a destabilized benzylic carbocation intermediate via two consecutive single-electron transfer processes by virtue of visible-light photoredox catalysis. This unique activation pattern avoids using strong Lewis acids and high temperatures that are required for generation of destabilized carbocations in traditional Friedel–Crafts reactions. This protocol demonstrates the first example of photoredox-catalyzed heterolysis of electronically deactivated benzylic C–Br bonds for the formation of destabilized carbocation intermediates.
The incorporation of fluorine atoms or fluorinated moieties into organic molecules can often lead to significant changes of their physical, chemical, or biological properties. Consequently, fluorinated organic molecules are widely used in areas of pharmaceuticals, agrochemicals and materials. Traditional approaches for the incorporation of fluorinated moieties into organic molecules include nucleophilic, electrophilic, and radical pathways. Among them, radical fluoroalkylations under visible-light photoredox catalysis have attracted much attention because of the mild reaction conditions and broad functionalgroup tolerance. In our previous work, the radical fluoroalkylation of isocyanides with fluorinated sulfones as the fluoroalkyl radical precursors via R f -SO 2 Ar bond cleavage has been achieved under visible-light photoredox catalysis (Rong, J. et al. Angew. Chem., Int. Ed. 2016, 55, 2743. Herein, as a logical extension of our previous research, we report the radical fluoroalkylation of aryl alkenes with fluorinated sulfones as the practical fluoroalkyl radical precursors under visible-light photoredox catalysis. Various fluoroalkyl radicals, including trifluoromethyl (CF 3 ), difluoromethyl (HCF 2 ), 1,1-difluoroethyl (CH 3 CF 2 ) and (phenyl)difluoromethyl (PhCF 2 ) radicals, can be incorporated into styrene derivatives via this method, delivering the oxyfluoroalkylation products in 46%~93% yields. Typical procedures for this reaction are given as follows: to a Schlenk tube were added 2-vinylnaphthalene (1a) (0.20 mmol, 30.8 mg, 1.0 equiv.), trifluoromethyl 2-benzo[d]thiazolyl sulfone (2b) (0.24 mmol, 64.1 mg, 1.2 equiv.), fac-Ir(ppy) 3 (2.7 mg, 0.004 mmol, 2 mol%), H 2 O (0.5 mL), and acetone (4.5 mL) sequentially. The resulting mixture was degassed with a freeze-pump-thaw procedure (3 times) and irradiated by a 6 W blue LED for 12 h. After the reaction completed, the mixture was extracted with Et 2 O and dried over anhydrous MgSO 4 . The organic solvent was removed under reduced pressure and the residue was purified by column chromatography on silica gel by using a 10∶1 (V/V) mixture of petroleum ether/EtOAc as an eluent to provide the hydroxytrifluoromethylation product 3a (31.2 mg, 65% yield).
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