Alkenes polyfluorinated

During the coverage period of this chapter, reviews have appeared on the following topics reactions of electrophiles with polyfluorinated alkenes, the mechanisms of intramolecular hydroacylation and hydrosilylation, Prins reaction (reviewed and redefined), synthesis of esters of /3-amino acids by Michael addition of amines and metal amides to esters of a,/3-unsaturated carboxylic acids," the 1,4-addition of benzotriazole-stabilized carbanions to Michael acceptors, control of asymmetry in Michael additions via the use of nucleophiles bearing chiral centres, a-unsaturated systems with the chirality at the y-position, and the presence of chiral ligands or other chiral mediators, syntheses of carbo- and hetero-cyclic compounds via Michael addition of enolates and activated phenols, respectively, to o ,jS-unsaturated nitriles, and transition metal catalysis of the Michael addition of 1,3-dicarbonyl compounds. ... 

A very interesting type of POM catalyst with polyfluorinated quaternary ammonium salts as counterions for the oxidation of alkenes, alkenols and alcohols was developed by Neumann and coworkers in 2003 . This catalyst with the general composition... 

It was mentioned previously that, unlike most arylnitrenes, polyfluorinated arylnitrenes have bountiful bimolecular chemistry. Banks and Sparkes found that pyrolysis of 4-azido-2,3,5,6-tetrafluoropyridine in cyclohexane produced the product of formal CH insertion in 45% yield. Tetrafluoropyridyinitrene was also captured by alkenes, dimethyl sulfoxide and even benzene. Pyrolysis of perfluorophenyl azide (15e) yields a product of formal insertion with a CH-bond of benzene and the formation of adducts with dimethyl sulfoxide.Abramovitch et demonstrated that... 

The combination of A/-halosuccinimides with polyfluorinated ammonium salts, in particular A/-halosuccinimide-triethylamine trisfhydrogen fluoride)42 (Method C), is convenient and effective for the halofluorination of alkenes. These easy-to-handle reagents allow work to be carried out at room temperature in conventional glass apparatus, while Olah s reagent requires polyethylene equipment. The reaction of various alkenes with A -halosuccinimide-triethylamine trisfhydrogen fluoride) in dichloromethane or diethyl ether at 0 C is complete within 3-5 hours giving the halogen fluoride addition products in 70-95% yield. 

Vanadium(V) fluoride converts polyfluoroaromatics into fluorinated cyclohexadienes and cyclohexenes, and reacts with polyfluorinated and polychlorinated alkenes,113 115 alkadienes, cycloalkenes and cyclodienes to give addition products of two fluorine atoms across C = C bonds.116117... 

The reactivity of polyfluorinated cycloalkenes towards vanadium(V) fluoride is similar to that of internal alkenes (Table 7). Perfluorocyclobutene (4) reacts with vanadium(V) fluoride at 20-22 C however, at 50-60 C the fluorination proceeds more efficiently. 

The reaction of polyfluorinated alkenes with silver fluoride and hydrogen fluoride is another hydrofluorination method. Under certain conditions, perfluoroalkylsilvcr compounds can be isolated. For example, 11 % silver fluoride in acetonitrile reacts with hexafiuoropropene at 25 °C under nitrogen to yield a clear light-yellow solution of [tetrafluoro-l-(trifluoromethyl)-ethyl]silver. The addition of hydrogen chloride in acetonitrile at 0"C yields 1,1.1,2,3,3,3-hepta-fluoropropane. ... 

Sultones such as 2 are formed in high yield from the cycloaddition reaction of sulfur trioxide and polyfluorinated alkenes. e.g. 

For reasons of symmetry the resulting acids are identical when a symmetrically substituted alkcne is oxidized. For the preparation of short-chain fluorinated acids, such as trifluoroacetic acid. this method is more economical than the oxidation of an alkene with a terminal C = C bond (see Table 1). Oxidation of polyfluorinated dienes and polyenes gives fluorinated dicar-boxylic acids. 

Linear and cyclic haloalkenes react with potassium permanganate to give acids or diacids. In contrast, polyfluorinated alkenes with a vinylidene group form ketones. ... 

Anions may be generated by reaction of fluoride ion with polyfluorinated aza-alkenes in a manner similar to that described earlier for fluoroalkenes (see Chapter 7, Section IIC, Subsection b) but, not being as readily available as fluoroalkenes, the chemistry is less well developed. Some examples of reactions induced by formation of aza-anions from aza-alkenes are shown in Figure 8.114. 

There are only few reports of [2 + 2] cycloadditions with ketenimines. " In most cases, reactions occur across the C=C bond. Only ynamines and polyfluorinated alkenes cycloadd to the C=N bond. 

Hydrogenolysis of vinylic fluorides is hardly ever done with the aim of removing fluorine finom a molecule. Rather, it occurs as a usually undesirable side reaction, accompanying reductions of other functions in fluorinated compounds. " It frequently takes place during catalytic hydrogenation of fluorinated alkenes. A clear-cut saturation of the double bonds in polyfluorinated alkenes is rare and usually requires mild reaction conditions,and hydrogenolysis of fluorine without reduction of the double bond in catalytic hydrogenation is unknown. Numerous examples are quoted in the review literature, " and a few samples are shown in Table 1. 

Addition of organomagnesiums is favored by strongly electron-withdrawing substituents on an aikene, even when the substituents are not capable of conjugating. Allylic reagents react readily with polyfluorinated alkenes, e.g. ... 

Fujita M, Hiyama T. Highly regio and stereocontrolled halo-genation of l,l-difluoro-2-halo-l-alken-3-ols as applied to polyfluorinated pyrethroid synthesis. Tetrahedron Lett. 1986 27 3659-3660. 

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