Alkenes fluorinated

Fluorinated alkenes can insert into C-H bonds at elevated temperatures, a relatively unusual example of simultaneous C-C and C-H bond formation [20, 21] (equations 16 and 17)... 

Ynamines also react with many fluorinated alkenes by an ionic mechanism to give fluorocyclobutenes, accompanied by varying amounts of diene depending on the fluoroalkene [107, 108] (equation 41). 

Fluorinated alkenes and alkynes are highly activated toward nucleophilic attack and reaction with bifunctional nucleophiles is a fruitful area for the synthesis of heterocycles. A review on perfluoroalkyl(aryl)acety-lenes contains many examples (91RCR501). 

The diradical mechanism b is most prominent in the reactions involving fluorinated alkenes. These reactions are generally not stereospecificand are insensitive to solvent effects. Further evidence that a diion is not involved is that head-to-head eoupling is found when an unsymmetrical molecule is dimerized. Thus dimerization of F2C=CFC1 gives 106, not 107. If one pair of electrons moved before the other, the positive end of one molecule would be expeeted to attack the negative end of the other. 

There are two possible ways to introduce fluorinated groups into silanes and silicones through the use of fluorinated organometallic reactants (mainly orga-nomagnesians and organolithians) or by hydrosilylation of fluorinated alkenes. 

The cyclodimerisation of fluorinated alkenes and formation of cyclobutane from alkenes activated by electron withdrawing groups has formed great application in laboratory and industry... 

These types of compounds can also be formed via a Wittig reaction [19]. Triphenylphosphine can be quatemized with a suitable alkyl iodide, and the resultant perfluoroalkylated phosphonium salt will react with aldehydes to give fluorinated alkenes which are easily hydrogenated (Scheme 3.4). This methodology has recently been expanded to the formation of perfluoroalkylated pyridines [20],... 

The addition of dinitrogen tetroxide across the double bonds of electron deficient fluorinated alkenes is a particularly useful route to v/c-dinitro compounds where yields are frequently high 8,37 tetrafluoroethylene gives a 53 % yield of l,2-dinitro-l,l,2,2-tetrafluoroethane. ... 

Cyclohexane is more environmentally acceptable than the more commonly-used CCl. A recent cleavage of a mono-fluorinated alkene to a ketone was thus effected. The alkene (70 mg, 0.28 mmol) was dissolved in a mixture of acetonitrile (0.5 cm ) and cyclohexane (0.5 cm ) and treated with RuClj.nH O (0.05 g, 0.2 mmol) and Na(lO ) (0.24 g, 10 mmol) in water (1 cm ). The mixture was stirred for 1.5 h, the product extracted with diethylether and dried over MgSO [330]. Other examples, using RuCyaq. 10(0H)j/CgHj2-CH3CN have been given [216]. 

A mono-fluorinated alkene has recently been oxidised to the corresponding ketone by RuCyaq. Na(IO )/CgHj3-CH3CN. Hydrolysis of the CF unit to C=0 did not occur in contrast neutral aq. I nO gave no ketone but there was extensive hydrolysis, c/ 1.11... 

Similarly, new synthetic routes to fluorinated alkenes and aryl trifluoropropynes have also been enabled by modification of the addition or addition-elimination products... 

Amdduri B,Boutevin (1997) Telomerisation Reactions of Fluorinated Alkenes. 192 165-233 Anwander R (1996) Lanthanide Amides. 179 33-112... 

Chambers RD, Vaughan JFS (1995) Nucleophilic Reactions of Fluorinated Alkenes. 192 1-38 Chambron J-C, Dietrich-Buchecker Ch, Sauvage J-P (1993) From Classical Chirality to Topologically Chiral Catenands and Knots. 165 131-162. 

The thermal reaction between two molecules of olefin to give cyclobutane derivatives (a 2 + 2 cycloaddition) can be carried out where the olefins are the same or different, but the reaction is not a general one for olefins.921 Dimerization of like olefins occurs with the following compounds F2C=CX2 (X = F or Cl) and certain other fluorinated alkenes (though not F2C=CH2), allenes (to give derivatives of 97),922 benzynes (to give biphenylene deriv-... 

Fluorinated alkenes tend to be pulmonary irritants, but most of the commercially important alkenes, such as tetrafluoroethene (TFE) and hexafluoropropene (FIFP), are only slightly toxic (Table 5). 

Prescreening results for fluorinated alkenes are summarized in Table 6. 

Af,Ar,AOV -Tetramethylnaphthalene-l,8-diamine described as Proton Sponge 38 (see Section 1.2) has the ability to act as a fluoride ion donor when its hydrofluoridc is used. Furthermore, it may be used to promote oligomerization reactions of fluorinated alkenes, e.g. 3, and poly-fluoroalkylation reactions with activated perfluoroaromatic compounds, e.g. 4.38... 

Tetrabutylammonium dihydrogen trifluoride also performs oxidative desulfurization fluorina-tion of 2-substituted l,l,l-txis(methylsulfanyl)ethanes in the presence of DBH leading to a new route to partially fluorinated alkenes. l,l,l-tris(methylsulfanyl)-5-phenylpentane (22) reacts with TBADTF in the presence of DBH to give the fluoro derivative 23, which is converted to the fluoroalkene 25 via the sulfoxide 24 followed by pyrolysis.217... 

Fluorination of partially fluorinated alkenes affords a route to linear perfluoroalkanes which excludes all rearrangements. For example, reaction of (fs)-8/f,9//-triacontafluorohexa-dec-8-ene and cobalt(III) fluoride at 200°C gives perfluorohexadecane in over 90% yield.55... 

Dihydroxylation, the addition of two hydroxy groups across a C = C bond, converts fluorinated alkenes into different products depending on the presence or absence of a fluorine atom at the hydroxylated carbon. Partially fluorinated alkenes with vicinal hydrogen atoms attached to the C = C bond can be hydroxylated to vicinal diols. When the reaction is performed with a sufficiently strong oxidizing agent, the initially formed diols are oxidized to vicinal diketones as the end products. 

Fluorinated alkenes with one fluorine atom attached to the C = C bond are converted into a-hydroxy ketones by potassium permanganate.92 In this case, the geminal fluorohydrin grouping in 52 eliminates hydrogen fluoride to give the end product 53.92... 

Dehydrofluorination of the fluorinated alkene 18 gives a mixture of diene 19 and allene 20. 

Fluorination has a particularly profound effect on the additions of nucleophiles to per-fluorinated alkenes where the intermediate is anionic. Such processes are dramatically assisted by the strongly stabilizing influence of perfluoroalkyl groups substituted at the incipient anionic site.66 Similar to carbocations (see Section 1.4.), the effect of fluorination in such systems is often ambiguous when monofluorination is involved. a-Halogens generally stabilize anions in the order bromine > chlorine > fluorine, which is the exact opposite to the inductive electron-withdrawing order of the substituents. This effect reflects the importance of l7t-repulsion.67... 

Organofluorine Chemistry Fluorinated Alkenes and Reactive Intermediates (Topics in Current Chemistry, Vol. 192) Chambers, R. D.. Ed. Springer Berlin. 1997. 

Reactions of fluorinated dipolarophiles. Electron-deficient unsaturated species generally make better dipolarophiles, therefore, fluorinated alkenes become better dipolarophiles when vinylic fluorines are replaced by perfluoroalkyl groups For example, perfluoro-2-butene is unreactive with diazomethane, but more highly substituted perfluoroalkenes, such as perfluoro-2-methyl-2-pentene, undergo cycloadditions in high yields [5] (equation 2) Note the regiospecificity that is observed in this reaction... 

Finally it should be noted that formation of the perfluorobicyclo[3.3.0]-octa-2,7-diene-4,6-diyl ligand allows pyramidalization of four fluorinated carbons and may reflect a thermodynamic preference for sp2-hybridized carbon atoms in coordinated OFCOT to undergo rehybridization to sp3, provided that the ancillary ligands present on the metal can support an increase in the formal oxidation state and that the constraints of the 18-electron rule are obeyed. The origins of this thermodynamic effect for uncoordinated fluorinated alkenes have been discussed in detail (2). Extensions to nickel, palladium, and platinum systems are described in Section IX. 

Vinylsilanes react with boron trichloride to give the corresponding borodesilylation products in good yield which, in turn, can be transformed into boronic esters 124 by alcoholysis (equation 102). The initial dichloroorganoborane products can be used directly in the Suzuki-Miyaura cross-coupling reaction192. Replacement of a carbon-silicon bond by a carbon-tin bond in fluorinated alkenes (e.g. 125) can be achieved by the reaction of silanes with Bu3SnCl and KF in DMF under mild conditions (equation 103)193. It is... 

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