Addition to fluoroolefins

Reactivity of halogen fluorosulfates X0S02F (X=C1, Br, I) is very similar to that of halogen triflates however, all of them have higher thermal stability, and they are distillable liquids [8, 102]. The chemistry of halogen fluorosulfates, including addition to fluoroolefins, has been reviewed [8] here only a short summary of these reactions is given. 

Belen kii GG, German LS (1984) New Reactions of Electrophilic Additions to Fluoroolefins. In Volpin ME (ed) Soviet Scientific Rev/Sec B. Chemistry Reviews. HarwoodAcademic Publishers GmbH, New York, vol 5, pi83... 

The known chemistry of the bisftrifluoromethyOnitroxyl [3i, 34] includes additions to both olefins [75, 36 37] and fluoroolefins [iaddition products with chlorotnfluoroethene or tetrafluoroethene [39] The nitroso denvative, (Cp3)3NONO, reacts with a liimted set of halogenated olefins to add the (CF3)2NO and NO moieties [40]... 

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... 

The effects of a- vs. P-fluonnation imply that fluoroolefms normally react regioselectively with electrophiles to minimize the number of fluorines p to the electron-deficient carbon in the transition state. Diverse types of electrophilic additions follow this rule (equations 6-8, for example), although there aie exceptions, especially for ionic addiPons of halomethanes to fluoroolefins [124]... 

In order to locate items of interest in the book, the subject index lists, in addition to chemical operations, types of compounds rather than specific compounds (with a few exceptions). If, for example, readers do not find what they are looking for under the entry fluoroolefins , they may try olefins , double bonds, additions of , etc. 

The addition of various Kolbe radicals generated from acetic acid, monochloro-acetic acid, trichloroacetic acid, oxalic acid, methyl adipate and methyl glutarate to acceptors such as ethylene, propylene, fluoroolefins and dimethyl maleate is reported in ref. [213]. Also the influence of reaction conditions (current density, olefin-type, olefin concentration) on the product yield and product ratios is individually discussed therein. The mechanism of the addition to ethylene is deduced from the results of adsorption and rotating ring disc studies. The findings demonstrate that the Kolbe radicals react in the surface layer with adsorbed ethylene [229]. In the oxidation of acetate in the presence of 1-octene at platinum and graphite anodes, products that originate from intermediate radicals and cations are observed [230]. 

Addition of nitric oxide to fluoroolefins [109, 110]. The addition of nitric oxide to tetrafluoroolefins produces mixtures of nitroso, nitro, and other compounds. In the presence of ferric chloride, substantial quantities of certain nitroso products are formed (Eqs. 62, 63). 

The addition of phosphines to fluoroolefins is of free radical nature [6, 7, 5]... 

The last comprehensive review on electrophilic reactions of fluoroolefins was published in 1969 [6], Since then, several reviews and papers dealing with different aspects of this chemistry, such as alkylation and alkenylation reactions [7], addition of halogen fluorosulfates [8], trifluoromethanesulfonates [9] and halogen fluorides [10] to fluoroolefins have been published. Additional information on the reactions involving carbocations could be found in two recent review articles [11,12] some data on the subject are scattered in several books and journals [13-19]. 

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. 

Addition of halogens to fluoroolefins is a common reaction which usually proceeds by a radical mechanism. However, some halogenations are catalyzed by Lewis acids. This reaction has been reviewed [6,14,77]. Among recently reported reactions are ionic addition of Br2 to RC6H4CF=CFX that was found not to be stereoselective [78], and the ratio of syn- and anti-addition products was thought to be determined by a combination of steric and electronic factors. 

In general, addition of more polar interhalogen compounds (ICI, IF, BrF, ClF) to fluoroolefins proceeds as an ionic process, starting with attack of halogen bearing positive charge on the C=C bond and formation of a cyclic halonium cation (Eq. 2) [10,18]. 

Progress in the preparation and isolation of different hypohaiites [92] results in a substantial number of publications exploring the addition of these materials to fluoroolefins. In contrast to addition of hypofluorites, which at this time is viewed as a radical process, a polar mechanism was proposed for addition of poly-fluorinated hypochlorites and hypobromites to olefins. Reactions of fluoroolefins... 

No good explanation exists for deviations in orientation of addition of hypochlorites to fluoroolefins however, it could be an indication of either a different mechanism of addition, such as radical, or a compromise between two mechanisms electrophilic and radical. 

Addition of halogen fluorosulfates XOS02F (X=C1, Br, I) to fluoroolefins is considered an electrophilic reaction [8]. However, the question of whether this process is concerted or the reaction proceeds via an independent carbocationic intermediate (Eqs. 2 and 3) is still open. Formation of carboxylic acid esters as byproducts in the reaction of HFP with C10S02F, which was carried out in trifluoroacetic or heptafluorobutyric acids as solvents, could not be a solid proof of conjugate addition, since formation of esters may be a result of addition of C10C(0)Rf to olefin. These materials are known to be formed in the reaction of ClOS02F with fluorinated carboxylic acids, even at low temperature [99]. 

Introduction of nitro and fluorosulfonoxy groups can be carried out by reaction of ionic 02N0S02F with fluoroolefins [8,116-118]. Nitronium fluorosulfa-te is not as active as halogen fluorosulfates addition to CH2=CF2 and CFH=CF2 proceeds only at ambient temperature [117]. Reaction with TFE and chloro-fluoroethylene proceeds at a noticeable rate at temperature above 50 °C, while addition to 2-H-F-propene only at temperatures higher than 120 °C [117] ... 

All experimental data are in agreement with the electrophilic mechanism of addition of 02N0S02F to fluoroolefins. 

Fluoroolefins add mercuric fluoride at 50- 100 °C to give bis(polyfluoroalkyl)-mercury derivatives. Reaction is usually carried out in hydrogen fluoride as a solvent. This process was reviewed and the electrophilic nature of this process established [6]. Addition to olefin starts by the attack of cation 3 (Eq. 5) on the double bond of fluoroolefin. 

Thermal addition of SXC12 to fluoroolefins was often referred to as electrophilic addition [136, 137], although observed orientation of addition actually resembles that in radical reactions [139], Regardless of the mechanism, this reaction is highly regioselective and undoubtedly has synthetic value as a high yield route to polyfluoroalkyldisulfides. 

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