- PROCESS FOR FLUORINATING COMPOUNDS
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Methods of preparing a fluorinated aryl or heteroaryl substrate by combining a quaternary ammonium cyanide and an aryl or heteroaryl substrate substituted with at least one chloro, bromo, sulfonyl, or nitro group to thereby provide a mixture, and combining the mixture with hexafluorobenzene to thereby provide the fluorinated substrate.
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Paragraph 0087; 0090
(2015/05/26)
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- Mild fluorination of chloropyridines with in situ generated anhydrous tetrabutylammonium fluoride
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This paper describes the fluorination of nitrogen heterocycles using anhydrous NBu4F. Quinoline derivatives as well as a number of 3- and 5-substituted pyridines undergo high-yielding fluorination at room temperature using this reagent. These results with anhydrous NBu4F compare favorably to traditional halex fluorinations using alkali metal fluorides, which generally require temperatures of ≥100 °C.
- Allen, Laura J.,Muhuhi, Joseck M.,Bland, Douglas C.,Merzel, Rachel,Sanford, Melanie S.
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p. 5827 - 5833
(2014/07/08)
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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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- Creating structural manifolds from a common precursor: Basicity gradient-driven isomerization of halopyridines
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5-Chloro-2,3-difluoropyridine, an intermediate in the manufacturing process of an industrial pesticide, can be hydrolyzed to 5-chloro-3-fluoro-2H-pyridinone and the latter converted into 2,5-dichloro-3-fluoropyridine (1a), 2-bromo-5-chloro-3-fluoropyridine (1b), 5-chloro-3-fluoro-2-iodopyridine (1c) and 3-chloro-5-fluoropyridine (1d). Consecutive treatment of these four substrates with lithium diisopropylamide and carbon dioxide or lithium diisopropylamide and iodine affords the corresponding 4-pyridinecarboxylic acids 2 and 4-iodopyridines 3, respectively. Amide-promoted deprotonation of such 4-iodopyridines 3 triggers an isomerization in which lithium and iodine change places. The resulting species can be trapped with carbon dioxide to give the acids 5a-c or neutralized to give the halopyridines 4a-c. The iodopyridines 4a and 4b can be converted into the acids 6a and 6b, the latter product leading also to the congeners 6c and 6d. The diiodopyridine 4c provides an entry to the halopyridine 4d, which at the same time may act as the precursor to the acid 5d, the acid 7 or the bisacid 8. Finally, the acid 9 is accessible from either one of the 5-chloro-3-fluoro-2-halopyridines 1b and 1c. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2002).
- Schlosser, Manfred,Bobbio, Carla
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p. 4174 - 4180
(2007/10/03)
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