Fluorination of heterocycles

Despite continued interest in the halogenation of heteroaromatic systems [149-151], there are still relatively few reports concerning the direct fluorination of heterocycles compared to publications that describe analogous chlorination and bromination reactions. 

The fluorination of heterocyclic compounds with xenon difluoride has received much less attention. Pyridine reacts readily with xenon difluoridc in dichloromethane without a catalyst to form 2-fluoropyridine (35 %), 3-fluoropyridine (20 %) and 2,6-difluoropyridine (11 %).80 8-Hydroxyquinoline treated with xenon difluoride forms 5-fluoro-8-hydroxyquinoline at room temperature in 35% yield.80 Uracil reacts with xenon difluoride to give 5-fluorouracil in 10% yield.81 Only one example exists of a highly substituted pyrrole fluorinated with xenon difluoride in acetonitrile in 35% yield.82... 

Direct Fluorination of Heterocyclic Aromatics Selective fluorination of quinoline aromatics leads to various commercially important products such as 5-fluoroadl, 5-fluoroprimaquine and ciprofloxacin with the fluorine moiety being decisive of their chemical and biological properties. 

Though partially fluorinated heterocycles are focus of much biological interest, limited examples of selective anodic fluorination of heterocycles have been reported [Eqs. (23-27)] [62-66]. These processes are limited to nitrogen- and oxygen-containing heterocycles, and the yields are generally quite low. In addition, no successful anodic fluorination of sulfur-containing heterocycles has been reported up to 1991. 

Fluorination of heterocycles, methods of 850R(34)319 81AG659. Fluorination of heterocycles and reactivity of fluorinated heterocycles ... 

Erian, A.W., Konno, A., and Euchigami, T., Electrolytic partial fluorination of organic compounds. Part 19. A novel synthesis of fluorothieno[2,3-h]pyridines using anodic fluorination of heterocyclic sulfides as a key step, J. Org. Chem., 60, 7654, 1995. 

Furin, G.G. Fluorine-containing heterocycles. Part. IV. Electrochemical fluorination of heterocyclic compounds. Adv. Heterocycl. Chem. 2006, 90, 239-310. 

Fluorine-containing Heterocycles. Part IV. Electrochemical Fluorination of Heterocyclic Compounds... 

III. Electrolytic Fluorination of Heterocyclic Compounds in Trialkylamine Complexes... 

A. Electrol5dic Fluorination of Heterocyclic Compounds whose Substituents... 

Direct fluorination of aliphatics and non-C moieties Direct fluorination of benzenoid aromatics Direct fluorination of heterocyclic aromatics Oxidations of alcohols, diols and ketones with fluorine Photo-oxidation of a-terpinene and cyclopentadiene Oxidation of benzyl alcohol to benzaldehyde Homogeneously catalyzed oxidation of butyraldehyde Oxidation of sulfite to sulfate Photochlorination of aromatic isocyanates... 

Hou Y, Fuchigami T (2000) Electrolytic partial fluorination of organic compounds XL. Solvent effects on anodic fluorination of heterocyclic sulfides. JElectrochem Soc 147 4567-4572... 

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