Nucleophilic addition fluoroolefins

Phenylmercury halides give the corresponding phenylmercury derivative, CgH5HgC(CF3)3 (61%) [156], and perfluorocyclobutene gives the corresponding cyclobutyl derivative [156], Mechanistically, the reaction could be interpreted as formation of the fluorocarbanion via nucleophilic addition of fluoride ion to the fluoroolefin followed by capture of the intermediate fluorocarbanion by the mercury salt [156]. The regiochemistry of the reaction is consistent with this mechanism [156] (equation 119). 

Because of thetr electron deficient nature, fluoroolefms are often nucleophihcally attacked by alcohols and alkoxides Ethers are commonly produced by these addition and addition-elimination reactions The wide availability of alcohols and fliioroolefins has established the generality of the nucleophilic addition reactions The mechanism of the addition reaction is generally believed to proceed by attack at a vinylic carbon to produce an intermediate fluorocarbanion as the rate-determining slow step The intermediate carbanion may react with a proton source to yield the saturated addition product Alternatively, the intermediate carbanion may, by elimination of P-halogen, lead to an unsaturated ether, often an enol or vinylic ether These addition and addition-elimination reactions have been previously reviewed [1, 2] The intermediate carbanions resulting from nucleophilic attack on fluoroolefins have also been trapped in situ with carbon dioxide, carbonates, and esters of fluorinated acids [3, 4, 5] (equations 1 and 2)... 

Fluoride ion produced from the nucleophilic addition-elimination reactions of fluoroolefins can cataly7e isomerizations and rearrangements The reaction of per fluoro-3-methyl-l-butene with dimethylamine gives as products 1-/V,/Vdimeth-ylamino-1,1,2,2,4,4,4-heptafluoro-3-trifluoromethylbutane, N,W-dimetliyl-2,2,4,4,4-pentafluoro 3 trifluoromethylbutyramide, and approximately 3% of an unidentified olefin [10] The butylamide results from hydrolysis of the observed tertiary amine, and thus they share a common intermediate, l-Al,A -dimethylamino-l,l 24 44-hexafluoro-3-trifluoromethyl-2-butene, the product from the initial addition-elimination reaction (equation 4) The expected product from simple addition was not found... 

A fluormated enol ether formed by the reaction of sodium ethoxide with chlorotnfluoroethylene is much less reactive than the starting fluoroolefin To replace the second fluorine atom, it is necessary to reflux the reaction mixture. The nucleophilic substitution proceeds by the addition-elimination mechanism [30] (equation 26). 

The addition of nucleophiles to cyclic fluoroolefins has been reviewed by Park et al. [2 ]. The reaction with alcohols proceeds by addition-elimination to yield the cyclic vinylic ether, as illustrated by tlie reaction of l,2-dichloro-3,3-di-fluorocyclopropene Further reaction results in cyclopropane ring opening at the bond opposite the difluoromethylene carbon to give preferentially the methyl and ortho esters of (Z)-3-chloro-2-fluoroacrylic acid and a small amount of dimethyl malonate [29] (equation 8). 

The addition of primary amines to fluoroolefins under anhydrous conditions yields imines The hexafluoropropene dimer, perfluoro-2-methyl-2-pcntcne, and ten butylamine react to yield a mixture of two compounds m a 9 4 ratio [4] (equation 3) rather than just the major keteiiimme-imine, as previously reported [5] It IS claimed that this result is possible by means of isomerization to the terminally unsaturated difluoromethylene isomer prior to nucleophilic attack Secondary amines add to fluoroolefins under anhydrous conditions to give fluonnated ternary amines m good yields If the fluoroolefin is added to the amine without cooling the reaction mixture, or if an excess of the secondary armne is used, there is a tendency toward dehvdrofluonnation of the ternary amine The products... 

Today microemulsions are used in catalysis, preparation of submicron particles, solar energy conversion, extraction of minerals and protein, detergency and lubrication [58]. Most studies in the field of basic research have dealt with the physical chemistry of the systems themselves and only recently have microemulsions been used as a reaction medium in organic synthesis. The reactions investigated to date include nucleophilic substitution and additions [59], oxidations [59-61], alkylation [62], synthesis of trialkylamines [63], coupling of aryl halides [64], nitration of phenols [65], photoamidation of fluoroolefins [66] and some Diels-Alder reactions. 

With regard to nonfluorinated olefins, the great reactivity of fluoroolefins toward nucleophiles comes from both a higher electrophilicity of the double bond, and from the stabilization of the carbanion, resulting from the addition of the nucleophile, by jS-fluorine atoms." °... 

Miller et al. [9] hypothesized rules on the regioselectivity of addition from the study of the base-catalyzed addition of alcohols to chlorotnfluoroethylene. Attack occurs al the vinylic carbon with most fluorines. Thus, isomers of dichloro-hexafluorobutene react with methanol and phenol to give the corresponding saturated and vinylic ethers The nucleophiles exclusively attack position 3 of 1,1-dichloro-l,2,3,4,4,4-hexafluoro-2-butene and position 1 of 4,4-dichloro-l,l,2,3,3,4-hexafluoro-1-butene [/0]. In l,l-dichloro-2,3,3,4,4,4-hexafluoro-l-butene, attack on position 2 is favored [1I (equation 5) Terminal fluoroolefins are almost invariably attacked at the difluoromethylene group, as illustrated by the reaction of sodium methoxide with perfluoro-l-heptene in methanol [12 (equation 6). 

The reactivity and orientation of nucleophilic attack on fluoroolefins are determined by the stability of the possible carbamon intermediates Fluoroolefins react regioselectively with nucleophiles so as to maximize the number of fluorines (3 to the electron-rich carbon in the transition state The reactivities increase in the order CF2=CF2 < CF2=CFCF3 CF2=C(CF3)2 and CF2=CF2 < CF2=CFC1 < CF2=CFBr, and nucleophdes attack exclusively at the CF2= end of these olefins [129,141] The regiochemistry of nucleophilic attack normally is predictable, but the product distribution arising from addition and addition-elimination pathways depends upon the olefin, nucleophile, and reaction conditions (equations 13-15) The various factors that control product distributions have been reviewed [142,143 144]... 

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). 

Perfluoroolefms have an activated C=C double bond in the presence of nucleophilic reagents owing to the electronegativity of fluorinated substituents. Although a hexafluoropropene trimer, F-(4-methyl-3-/sopropyl-2-pentene) (T-2), has several bulky fluorinated substituents in addition, CF3Si(CH3)3 (la) easily reacted with T-2 to give CF3-substituted fluoroolefins in high yields (Scheme 1) [8],... 

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