Reaction with perfluoroalkenes

An alternative route to aziridines by [2+1] cycloaddition could be the use of nitreiies however, reported examples are mostly limited to reactions with perfluoroalkenes. ... 

Carbonyl difluoride is a particularly versatile fluorinating agent, and an important material for the synthesis of organofluorine compounds [1079], Its reactions with perfluoroalkenes gives perfluoroacyl fluorides in the presence of a fluoride ion source, and its facile reaction with amines or alcohols results in the formation of carbamoyl fluorides or fluoroformates, respectively. The fluorination of carbonyl compounds, such as aldehydes and ketones, with COF can give gem-difluorides by replacement of the carbonyl oxygen atom with two atoms of fluorine e.g.-. 

Acylation of alkenes can also be similarly effected with SbFs. Reaction of acetyl fluoride with trifluoroethylene produces 1,1,1,2-tetrafluorohexane-3,5-dione in 40% yield. When antimony pentafluoride is used in excess (more than 6 molar equivalents), 1,1,1,2-tetrafluorobutan-3-one is formed as a side product. Benzoyl fluoride reacts with dilluoroethy lene to form the expected ketone in 39% yield. a, 3-Unsaturated carboxylic acid fluorides have also been used in reactions with perfluoroalkenes. In these cases, a,p-unsaturated ketones are obtained (eq 17). Enol acetates of perfluoroisopropyl methyl ketone and perfluoro-f-butyl methyl ketone react with acetyl fluoride to provide the corresponding p-diketones (eq IS). ... 

The reaction of perfluoroalkenes with alkaline hydrogen peroxide is a good general method for the preparation of the corresponding epoxides with the exception of the most reactive of the series, TFEO (eq. 6). 

Knunyants showed that such perfluoroalkenes, under forcing conditions, undergo Diels-Alder reactions with cyclic dienes such as cyclohexadiene [72] (equation 65) or furan [7J] (equation 66). 

The uncatalyzed hydroboration-oxidation of an alkene usually affords the //-Markovnikov product while the catalyzed version can be induced to produce either Markovnikov or /z/z-Markovnikov products. The regioselectivity obtained with a catalyst has been shown to depend on the ligands attached to the metal and also on the steric and electronic properties of the reacting alkene.69 In the case of monosubstituted alkenes (except for vinylarenes), the anti-Markovnikov alcohol is obtained as the major product in either the presence or absence of a metal catalyst. However, the difference is that the metal-catalyzed reaction with catecholborane proceeds to completion within minutes at room temperature, while extended heating at 90 °C is required for the uncatalyzed transformation.60 It should be noted that there is a reversal of regioselectivity from Markovnikov B-H addition in unfunctionalized terminal olefins to the anti-Markovnikov manner in monosubstituted perfluoroalkenes, both in the achiral and chiral versions.70,71... 

On the other hand, variable yields of fluorinated 2-alkoxy-2//-pyrans 64 were found108,109 in mixtures formed in the reaction of perfluoroalkenes with dialkyl malonates. 

The reaction of perfluoroalkenes with antimony(V) fluoride has been extensively studied by German and others from his group.3 Perfluoroalk-1-enes 1 react under mild conditions with antimony(V) fluoride to give ( )-perfluoroalk-2-enes 2.818... 

Preparation of nitronitroso dimers from a variety of straight chain alkenes has been patented. " The reactions of nitric oxide with alkenes are extremely complex (e.g. isobutylene) and are rarely usefiil. Perfluoroalkenes add nitric oxide at room temperature in the da tetraflucMoethylene gives ONCF2CF2NO (68%) the reaction with perfluoropropene is more complex. ... 

It should be noted that under some conditions reaction of internal perfluoroalkenes and -cycloalkenes with tributylphosphane and triphenylphosphane results in dimerization, preceded by defluorination and formation of a 1,3-diene and an appropriate difluoro-A -phosphane. For example, reaction of perfluoroalkenes containing three perfluoroalkyl groups at the double bond w ith a phosphane[tributylphosphane, triphenylphosphane, tris(diethylamino)phosphane] results in reductive dimerization of these alkenes, to give 1,3-dienes and difluoro-A -phosphanes. 

Perlluoroalkanesulfonic acids (c.g., 24) are obtained as their sodium salts from the reaction of sodium hydrogcnsulfite with perfluoroalkenes such as 23 in the presence of sodium tetraborate. The yields are quite good." ... 

It was noted that for the perfluorobutanoic acid salts of the alkaline earth metals the yield of perfluoroalkene increased with increasing weight of the metal cation (vide supra). Decomposition of the barium salt gave hexafluoropropene in 78% yield while the reaction with the magnesium salt gave > 5 % of the same product. An exception was ammonium per-fluorobutanoate (4) which formed no alkene, but instead gave an almost quantitative yield of... 

Problems of orientation of attack and reactivities of fluorinated alkenes arise in a way that is analogous but entirely complementary to the classical problems of electrophilic attack on alkenes. For example, typical of the results that we must be able to account for is the reaction of methoxide in methanol which occurs specifically at the Cp2= site in perfluoropropene (Figure 7.15). Also, there is a very wide range of reactivity with perfluoroalkenes for example, reactions of tetrafluoroethene usually require base catalysis, whereas perfluoroisobutene reacts with neutral methanol. 

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