Fluorinating agents group 15 fluorides

Thus, aryl-substituted antimony fluorides provide replacement of chlorine by fluorine atoms in aromatic compounds containing trichloromethyl and pentachloro- or dichlorotri-fluoroethyl groups. Their activity as fluorinating agents decreases in the order tetrafluoro(phenyl)-A5-stibane > trifluorodi(phenyl)-25-stibane >antimony(lIl) fluoride dill uorotri(phenyl)-/i.5-stibane. 

Silver(II) fluoride and potassium tetrafluoroargentate(III) are too powerful as fluorinating agents for cyclohexanone, as no products containing a carbonyl group are detected.11... 

In the same way as intramolecular displacement leads to particularly stable atomic groupings within a molecule, the disproportionation reactions between several molecules are attributable to the tendency for the more stable compound with the higher fluorine content to form. Reactions of this kind are sometimes used to obtain highly fluorinated compounds from products with lower fluorine contents, for example, the catalytic fluorination of chloroalkanes with hydrogen fluoride or with fluorination agents such as antimony(V) fluoride or antimony(III) fluoride. The chlorine compound formed as the second product of the disproportionation process is reused as the starting material for the preparation of the compound to be dispropor-tionated. 

Furin GG, Bardin VV (1989) Higher Fluorides of Group V and VI Elements as Fluorinating Agents in Organic Synthesis. In ibid, p 117... 

A cyclopropylfluorosilane was formed in excellent yield on reaction of a l-(allyldimethyl-silyl)bicyclo[4.1. Ojheptane derivative 1 with a slight excess of bromine and then with pyridinium poly(hydrogen fluoride). The reaction appears to be sensitive to the nature of the neighboring groups and the quality of the fluorinating agent (see Section 5.2.5.1.9.2.). ... 

The conversion of carboxyl groups into trifluoromethyl groups proceeds in two steps. The first step, exchange of the hydroxy group by fluorine, can be accomplished easily by use of less potent fluorination agents such as a-fluoroenamines or DAST. Subsequent conversion of the carboxylic acid fluoride into the trifluoromethyl group requires more drastic conditions and can be achieved only with SF4. The most convenient procedure is the one-step direct reaction of carboxylic acids with SF4 in aHF as solvent (Scheme 2.66). For most aliphatic and aromatic carboxylic acids, excellent yields can be obtained even at room temperature or below. 

The synthesis of fluorinated analogs of biologically important amines has been explored extensively. Their direct preparation is difficult since most of the common fluorination agents can also react with the amino group. However, by the use of appropriate solvents, like liquid hydrogen fluoride which protects the amine functionality by protonation, successful... 

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