- Hydrodefluorination of fluoroaromatics by isopropyl alcohol catalyzed by a ruthenium NHC complex. An unusual role of the carbene ligand
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The NHC (NHC = N-heterocyclic carbene) complex Cp*(IPr)RuH3 catalyzes hydrodefluorination of aromatic fluorides at 70 °C with isopropyl alcohol as the reducing reagent. The reaction is selective for aromatic fluorides, as almost negligible C(sp3)?F bond reduction takes place. The activity decreases from more to less fluorinated substrates, but polyaromatic monofluorides, such as 1-fluoronaphthalene and 6-fluoro-2-methylquinoline, can also be reduced in moderate to good yields. Kinetic studies are consistent with a mechanism based on elimination of NHC and reversible substrate coordination, followed by coordination of the alcohol.
- Mai, Van Hung,Nikonov, Georgii I.
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p. 7956 - 7961
(2018/05/23)
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- Photocatalytic hydrodefluorination: Facile access to partially fluorinated aromatics
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Polyfluorinated aromatics are essential to materials science as well as the pharmaceutical and agrochemical industries and yet are often difficult to access. This Communication describes a photocatalytic hydrodefluorination approach which begins with easily accessible perfluoroarenes and selectively reduces the C-F bonds. The method allows facile access to a number of partially fluorinated arenes and takes place with unprecedented catalytic activity using a safe and inexpensive amine as the reductant.
- Senaweera, Sameera M.,Singh, Anuradha,Weaver, Jimmie D.
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supporting information
p. 3002 - 3005
(2014/03/21)
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- Removal of fluorine from and introduction of fluorine into polyhalopyridines: An exercise in nucleophilic hetarenic substitution
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Starting from six industrially available fluorinated pyridines, an expedient access to all three tetrafluoropyridines (2-4), all six trifluoropyridines (5-10), and the five non-commercial difluoropyridines (11-14 and 16) was developed. The methods employed for the selective removal of fluorine from polyfluoropyridines were the reduction by metals or complex hydrides and the site-selective replacement by hydrazine followed by dehydrogenation-dediazotation or dehydrochlorination-dediazotation. To introduce an extra fluorine atom, a suitable precursor was metalated and chlorinated before being subjected to a chlorine/ fluorine displacement process.
- Bobbio, Carla,Rausis, Thierry,Schlosser, Manfred
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p. 1903 - 1910
(2007/10/03)
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- Preparation and reactions of 2,3,4,6-tetrafluoropyridine and its derivatives
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A reliable route to 2,3,4,6-tetrafluoropyridine has been established starting from the readily available 3,5-dichlorotrifluoropyridine by halogen exchange under controlled conditions to give 3-chlorotetrafluoropyridine and its subsequent hydrodechlorination using hydrogen over palladium on alumina at 250-270°C. The formation and reactions of the 3-lithio derivative have been studied with the aim of obtaining 3,4-disubstituted trifluoropyridines. Routes to such materials have been developed and their conversion to deazapurine derivatives as potential substrates for the generation of anti-sense nucleosides are reported.
- Coe, Paul L.,Rees, Anthony J.
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- Reductive transformations of organofluorine compounds: II. Hydrodechlorination of chloropolyfluoroarenes by the action of zinc
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Polyfluoroarenes containing chlorine atoms in the aromatic ring and/or in the benzylic position undergo hydrodechlorination by the action of zinc in aqueous dimethylformamide. The use of Zn/Cu and addition of salts (NaCl, Na2SO4, NH4Cl) favor reductive dechlorination of the Carom - Cl bond. Polyfluorobenzotrichlorides react with excess zinc to give the corresponding CH3-substituted derivatives, otherwise CH2Cl- and CHCl2-containing compounds are formed. The reduction of C6F5CCl3 and C6F5CH2Cl with zinc in the presence of copper provides lower yields of the hydrodechlorination products and leads to formation of 1,2-bis(pentafluorophenyl)ethane.
- Krasnov,Platonov
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p. 1488 - 1499
(2007/10/03)
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- FLUORINATIONS WITH POTASSIUM TETRAFLUOROCOBALTATE(III) PART VII. FURTHER INVESTIGATIONS ON THE FLUORINATION OF PYRIDINE
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The product from the fluorination of pyridine by KCoF4 at ca. 220 deg C contains eleven fluoropyridines, two fluoro-2-azahex-enes, three azahexadienes, and two fluoro-N-methylpyrrolidines, besides an azacyclohexa-1,3-diene.Four products were isolated from fluorination of pyridine by CoF3 at ca. 150 deg C, a 2-azahexene, two N-methylpyrrolidines, and 4H-nonafluoropiperidine.
- Coe, Paul L.,Holton, Andrew G.,Tatlow, John Colin
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p. 171 - 190
(2007/10/02)
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- Heterocyclic Polyfluoro-compounds. Part 32. Photochemical Reactions of 3-Chlorotetrafluoro- and 3,5-Dichlorotrifluoro-pyridines with Olefins, and their Photoreduction
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Ethylene reacts photochemically with 3-chlorotetrafluoropyridine to yield 3-(2-chloroethyl)tetrafluoropyridine, and cyclo-pentene and -hexene yield the corresponding 3-cycloalkyltetrafluoropyridines.Photochemical reaction of cyclohexene with 3,5-dichlorotrifluoropyridine yields 3-chloro-5-cyclohexyltrifluoropyridine.The chlorine in 3-chlorotetrafluoropyridine, and one of the chlorines in 3,5-dichlorotrifluoropyridine, is readily reduced photochemically in solvents such as ethanol, diethyl ether, or acetone.
- Barlow, Michael G.,Haszeldine, Robert N.,Langridge, John R.
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p. 2520 - 2522
(2007/10/02)
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