Perfluorinated olefin compound

The molecular ions of perfluorinated olefins are usually observed. The m/z 31 ion is frequently more abundant in fluorinated olefins than in fluorinated saturated compounds. 

An interesting reactivity is observed with 2//-cyclopenta(d)pyridazine and its 2-methyl and 2-phenyl analogs. Monochlorination of these compounds revealed the relative reactivities are 7,1 1,7 1 [78H( 11)155). If the cyclopentyl part is substituted with chlorine atoms, the 2-methyl compounds are transformed with /V-chlorosuccinimide (NCS) into the 2-chloromethyl derivative (80JOC1695). In contrast to other perfluo-roazines, perfluoroalkylpyridazines, when fluorinated with cobalt trifluoride, lose nitrogen to give perfluorinated olefins [8IJCS(P1)2059],... 

In a recent review, Tao etal. [34] describe the partial fluorination and the perfluorination of organics with particular emphasis on medically important compounds and pharmaceuticals. The selective electrofluorination (SEF) of olefins and active methylene groups is reviewed by Noel et al. [35] In the case of heterocycles, nuclear fluorination is known to be the predominant process. However, in aromatic compounds, nuclear substitution as well as addition proceeds simultaneously, leading to the formation of a mixture of products. The influence of solvents, supporting electrolytes, and adsorption on product yield and selectivity is summarized and evaluated. Dimethoxyethane is found to be a superior solvent for SEF processes. Redox mediators have been employed to minimize anode passivation and to achieve better current efficiencies. 

Fluorinated carbocations play an important role as intermediates in electrophilic reactions of fluoroolefins and other unsaturated compounds. For example, F-allyl cation 1 was proposed as a reactive intermediate in reactions of HFP with fluoroolefins catalyzed by Lewis acids [7]. The difference in stability of the corresponding allylic cations was suggested as the explanation for regio-specific electrophilic conjugated addition to CF2=CC1CF=CF2 [11]. Allylic polyfluorinated carbocations were proposed as intermediates in the reactions of terminal allenes with HF [53] and BF3 [54], ring-opening reactions of cyclopropanes [55], Carbocations are also an important part of the classic mechanism of electrophilic addition to olefins (see Eq. 2). This section deals with the questions of existence and stability of poly- and perfluorinated carbocations. 

Reactivity of nitrosonium fluorosulfate and trifluoromethansulfonate 0N0S02X (X=F, CF3) is similar to that of nitronium fluorosulfate, although they are less active than the latter. Reaction, which occurs only with fluoroethylenes and perfluorinated vinyl ethers [ 119 -121 ], is of an electrophilic nature it results in low to moderate yields of nitrosoalkyl compounds when the olefin has a limited contact time with the reaction mixture ... 

This route is especially valuable for the transformation of electron-rich heteroaromatic compounds into their fluorinated analogues, which are not suitable for the nucleophilic exchange route. The method has been extended by addition of fluorinated olefins. The fluoroolefins add in a radical process to the 2-position of tetrahydrofuran, followed by perfluori-nation to give the perfluorinated 2-alkyl-substituted tetrahydrofurans in excellent yields [84JFC(25)523 85JFC(29)323] (Scheme 3). 

Under SbCls catalysis oxygen-bromine exchange between benzaldehyde and o-chlorobenzal bromide proceeds at 100 °C to give benzal bromide and o-chlorobenzaldehyde in moderate yields [88]. Isomeric transformation of perfluorinated epoxides to the corresponding carbonyl compounds occurs in the presence of SbFs [89]. Isomerization of polyfluorinated olefins, cyclohexadienes, and cyclopropanes is also promoted by the action of SbFs [90]. 

The synthesis of azo-compounds via condensation of perfluorinated w-nitrosoalkanecarboxylic acids or esters with amines was mentioned earlier [item (vi), p. 231]. An alternative method to the AtNHj-RfNO condensation for the preparation of azo-compounds of the type AtNiNRf (Rf = perfluoro-alkyl or -cycloalkyl) has now been discovered, viz. trapping of peifluoro-carbanions (from perfluoro-olefins + caesium or potassium fluoride) with arenediazonium salts (see Scheme 36). ... 

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