Perfluoroalkyl halide

Kperjluorocarboxylic acid or its salt reacts with fluorosulfonylhypohalites to produce the corresponding perfluoroalkyl halide [69] (equations 55 and 56). 

The reactivities of the substrate and the nucleophilic reagent change vyhen fluorine atoms are introduced into their structures This perturbation becomes more impor tant when the number of atoms of this element increases A striking example is the reactivity of alkyl halides S l and mechanisms operate when few fluorine atoms are incorporated in the aliphatic chain, but perfluoroalkyl halides are usually resistant to these classical processes However, formal substitution at carbon can arise from other mecharasms For example nucleophilic attack at chlorine, bromine, or iodine (halogenophilic reaction, occurring either by a direct electron-pair transfer or by two successive one-electron transfers) gives carbanions These intermediates can then decompose to carbenes or olefins, which react further (see equations 15 and 47) Single-electron transfer (SET) from the nucleophile to the halide can produce intermediate radicals that react by an SrnI process (see equation 57) When these chain mechanisms can occur, they allow reactions that were previously unknown Perfluoroalkylation, which used to be very rare, can now be accomplished by new methods (see for example equations 48-56, 65-70, 79, 107-108, 110, 113-135, 138-141, and 145-146)... 

A peculiar reaction of perfluoroalkyl halides with chlorine fluorosulfate yields perfluoroalkyl fluorosulfales [iS (equation 17)... 

Allylation of perfluoroalkyl halides with allylsilanes is catalyzed by iron or ruthenium carbonyl complexes [77S] (equation 119) Alkenyl-, allyl-, and alkynyl-stannanes react with perfluoroalkyl iodides 111 the presence ot a palladium complex to give alkenes and alkynes bearing perfluoroalkyl groups [139] (equation 120)... 

Under sonication conditions, the reaction of perfluoroalkyl bromides or iodides with zinc can be used to effect a variety of functionalization reactions [39, 40, 41, 42] (equation 30) Interestingly, the ultrasound promoted asymmetric induction with the perfluoroalkyl group on the asymmetric carbon was achieved by the reaction of perfluoroalkyl halides with optically active enamines in the presence of zinc powder and a catalytic amount of dichlorobisftc-cyclopenta-dienyl)titanium [42] (equation 31)... 

Solvent plays a significant role in these reactions In contrast to the formation of organocadmium compounds in the duect reaction of perfluoroalkyl iodides and cadmium powder in DMF [729], dimerization of the perfluoroalkyl halide was observed in acetonitrile [777] (equation 100)... 

Direct electrochemical reduction of perfluoroalkyl halides generates perfluoroalkyl radicals or anions depending on the electrolytic conditions and starting halides. Calas et al. have performed the electrocatalytic addition of perfluoroalkyl iodides to 3-hydroxyalkynes in aqueous KCI emulsion using a... 

In contrast to the direct reduction as described above, the indirect electrochemical reduction of perfluoroalkyl halides is a versatile and novel method for generating perfluoroalkyl radicals selectively. Saveant et al. have demonstrated many successful examples. Using terephthalonitrile as a mediator, the indirect reduction of CF3Br in the presence of styrene leads to the dimer of the radical adduct obtained by the attack of CF on styrene. On the other hand, in the presence of butyl vinyl ether, the mediator reacts with the radical adduct obtained by the attack of CF3. on the olefin (Scheme 3.4) [14]. 

Furthermore, Saveant et al. have shown elegant examples of electrochemi-cally induced nucleophilic substitution of perfluoroalkyl halides. The reaction mechanism is a slightly modified version of the classical SRNI mechanism in... 

The title reaction has been achieved by the treatment of alkenes and alkynes with sodium phenyltellurolate in the presence of perfluoroalkyl halides. ... 

The reaction proceeds via a single electron transfer (SET) from sodium tellurolate to perfluoroalkyl halides followed by a radical chain reaction of the SRN mechanism. 

It is important to note that the substitution of trifluoromethyl and perfluoroalkyl halides goes through a specific process. The displacement of the halogen atom never occurs via the usual Sn 1 or Sn2 processes rather it occurs either via a halophilic attack and a monoelectronic transfer (SnrI) or via an a-elimination of a fluoride ion and... 

Perfluoroalkyl iodides reacted with trialkylsilyl chloride in DMF in the presence of zinc followed by hydrolysis with acid to give perfluoroaldehydes in good yields [55]. Recently, Hu reported a new preparation of perfluoroalkyl aldehydes via reaction of perfluoroalkyl halides and DMF, initiated by redox... 

Other sulfonate derivatives are obtained by the use of trifluoromethanesulfonyl hypochlorite and hypobromite (CF3S020C1 and CF3S020Br) in reactions with perfluoroalkyl halides and their derivatives [30]. These reactions lead to the corresponding trifluoromethanesulfonate derivatives of alkanes (equation 28) (Table 11). The reaction proceeds with complete retention of stereochemistry at the carbon center [30]. 

Recently, the electrocarboxylations of benzyl and aryl halides and perfluoroalkyl-halides [39] in supercritical mixture or in supercritical carbon dioxide (scC02) and of aryl and benzyl halides in microemulsion [40], were also investigated in order to exploit the possible effect of the use of these solvents on the selectivity of the... 

Hunsdiecker reactions of salts of perfluoroalkanoic acids are known primarily as perhaps the best way of making perfluoroalkyl halides [58,306,307], but there have been other synthetic uses found for the perfluoroalkyl radicals which are formed by this decarboxylative process [308]. 

The first successful syntheses utilizing trifluoromethyl iodide in transition metal chemistry were reported by Stone and his students. Stone reasoned that if CF3I would not react with transition metal anions to form trifluoromethyl derivatives [see Eq. (3)] then perhaps compounds containing perfluoroalkyl substituents could be generated by the oxidative addition of perfluoroalkyl halides to low valent transition metal substrates (9,10). The first reported trifluoromethyl-substi-tuted transition metal complex prepared by this route is shown in Eq. (4) (41). 

Electrochemical catalyst regeneration was tested for addition reactions of perfluoroalkyl halides 41b to a-methylstyrene 42 (Fig. 8) [96], Dimers 43 were isolated in 50% and 70% yield, respectively, using 6-10 mol% of Ni(bipy)Br2 as the catalyst in a divided cell at -1.2 V at a platinum cathode. Under these conditions the Ni(II) complex is first reduced to Ni(0). 

Castle and Widdowson were first to disclose alkyl-alkyl Kumada coupling reactions catalyzed by Pd(dppf)Cl2 [195]. This report was later questioned and corrected by Scott [196]. Matsubara and colleagues established formal Stille-type coupling reactions of perfluoroalkyl halides with allyl, alkynyl, or vinyl stannanes catalyzed by 10 mol% of Pd(PPh3)4, which have to be considered, however, better as radical addition/elimination reactions rather than as coupling reactions (see Sect. 3.1) [184],... 

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