Oxidative defluorination

Olson, M.J., C.A.Reidy, J.TJohnson, and T.C.Pederson. 1990b. Oxidative defluorination of 1,1,1,2-tetrafluoroethane by rat liver microsomes. Drug Metab. Dispos. 18 992-998. 

N-oxidation/S-oxidation Dihydroxylation Dehydrogenation or reduction Demethylation Deethylation Depropylation Oxidative deamination Oxidative dechlorination Oxidative defluorination Hydration Methyl to an acid Conjugation Glucuronidation Sulfation... 

The defluorination of the complex acids is a key step in the production of tantalum and niobium oxides as it defines the quality of the products and durability of the production equipment. 

Ammonium hydrofluoride is relatively stable, even in the molten state. In addition to being in contact with tantalum or niobium oxide, the compound will initiate the fluorination process yielding complex tantalum or niobium fluoride compounds. There is no doubt that thermal treatment of the hydroxides at high temperatures and/or at a high temperature rate leads to the enhancement of the defluorination processes, which in turn results in an increase in fluorine content of the final oxides. 

Certain metals can be used for gas-phase defluorinations to give fluoroaromatic compounds. Thus, dehalogenations occur when the compounds in a gas phase are passed at high temperature over fillings or gauze made of copper,124 125 iron,126 131 iron oxides,132 or platinum,133... 

Aromatic molecules with fluorine or fluorine-containing substituents frequently have high bioactivity [39] and are therefore used for medical and agrochemical applications, in which they are deliberately introduced to organisms and/or the environment (Fig. 2). They are typically less bioaccumulative and less environmentally persistent than saturated fluorocarbons, and may be degraded oxidatively under aerobic conditions, where defluorination may or may not occur.5 The world market for fluoroaromatics was estimated at 10,000 tonne per annum in... 

Hydrogenation of the trifluorostyrene 92 over platinum oxide results in partial defluorination during saturation of the side chain (eq. 13.126).226... 

In the case of diazirines, both difluorodiaztrine and bis(trifluoromethyl)diazirine have been obtained. Difluorodiazirine was originally prepared by reductive defluorination of bis(difluoroamino)difluoromethane [320, 321], but it can also be obtained by an interesting fluoride-ion-induced rearrangement of difluorocyanamide [322] (Figure 8.125). Bis(trifluoromethyl)diazirine [318, 323] is best obtained by the oxidation of 2,2-diaminohexafluoropropane, prepared from hexafluoroacetone, with sodium hypochlorite (Figure 8.126). 

Oxidative additions of 2-haloalkenes to in situ generated Cp2Zr equivalents have been observed. Defluorination of perfluorocarbons and perfluoroaromatics can be effected through reduced zirconocene species an attractive, possible pathway is via oxidative addition of the C-F bond to Cp2Zr. ... 

Oxidations. Clean products are generally obtained by using alumina-supported reagents. For the oxidative dimerization of thiols by OMSO or NalOj, the conversion of hydroquinones to quinones and 2-naphthols to BINOLs in the presence of CuSO, the formation of lactones from a,co-diols under the influence of NaBrOj, and the hydrolytic defluorination of certain perfluoroalkylarenes, alumina has unique or positive effects. 

Perfluoroaromatic compounds can be obtained by reductive aromatization of readily accessible perfluorocycloaliphatic precursors [73]. Defluorination can be accomplished by contact with hot (500 °C) iron or iron oxide. After reducing the per-fluoroaliphatic compound the metal surface can be regenerated by passage of hydrogen gas. This method has been scaled up to a continuous flow process for industrial synthesis of a variety of perfluorinated aromatic compounds (Scheme 2.27). 

Oleum (fuming sulfuric acid) Oxidation catalyst made from porcelain Porchloric acid Peroxides, inorganic Phosphates, except defluorinated and ammoniated... 

Oxidative addition. 5.2 Hydrodefluorination, M-F bond formation. 5.3 Nuoleophilio attaok. 5.4 Defluorination... 

We classify the fundamental processes of intermolecular G-F bond activation in the following six categories (i) oxidative addition of fluorocarbon, (ii) M-G bond formation with HF elimination, (iii) M-G bond formation with fluorosilane elimination, (iv) hydrodefluorination of fluorocarbon with M-F bond formation, (v) nucleophilic attack on fluorocarbon, and (vi) defluorination of fluorocarbon (Scheme 4). Table 2 shows the occurrence of these processes for intermolecular G-F activation, classified according to the type of G-F bond. For instance, oxidative addition is a characteristic process for fluoroaromatics but not for fluoroalkanes, while defluorination is characteristic of fluoroalkanes but not fluoroaromatics. We include processes as intermolecular even if they involve coordination of the fluorocarbon in one of the modes in Section 1.26.1.1 prior to G-F bond breaking. Notice that processes (ii), (iii), and (iv) could be described as cr-bond metatheses we have avoided this descriptor, since it has mechanistic connotations that are only appropriate in some cases. It should also be recognized that secondary processes may make some reactions awkward to classify under this scheme. 

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