Perfluorocyclopentene, reaction with

Only perfluorocyclopentene has been synthesised directly by this route it can be seen that, here, allylic rearrangements can occur to make all positions potentially vinylic and therefore reactive [64]. An analogous situation applies to hexachlorobutadiene. These reactions may also be carried out with potassium fluoride that has been exposed to Sulpholan or 18-crown-6, but then suspended in a fluorocarbon. Under these conditions, a significant proportion of hexafluoro-2-butyne is formed, presumably because the latter is extracted into the fluorocarbon, pre-empting further reaction with fluoride [65] (Figure 2.14). 

The reaction with the Grignard reagents led to the monosubstitnted perfluorocyclopentenes A, which were subjected to the further nucleophilic substitution reaction using another Grignard or aryllilhium reagents to obtain unsymmetrical disubstituted perfluorocyclopentenes C in high yields [41]. 

In addition to thiophenes, the above reactions of perfluorocyclopentene, as well as of fluorinated derivatives of cyclobutene and cyclohexene, can be carried out with fused thienyl derivatives and various heterocycles forming relatively stable anions. 

The synthesis of a novel compound l,2-bis(2-methylbenzo[/ ]furan-3-yl)-perfluorocyclopentene 92 was realized by reaction of octafluorocyclopentene with 3-lithiated 2-methylbenzo[3]furan, which was generated by the treatment of 2-methyl-3-bromobenzo[ ]furan with -BuLi at —78°C in THE, as can be seen in Equation (86) <2005JOC10323>. 

Perfluorocyclopentene is exceptional in being obtained from non-fluorinated materials by a simple one-step procedure, i.e. displacement of chlorine in perchlorocyclopentene by fluoride ion [51], although some polyfluorochloro- and polyfluorohydro-alkenes can be made by analogous processes [51, 52]. If a perfluorocarbon is used as the reaction medium with potassium fluoride/18-crown-6 complex, then a variety of products may be obtained, including hexafluoro-2-butyne [53]. 

Certain reactions of Li-amalgam with gaseous perfluorinated precursors do not follow Eq. 4.4 [4,5]. An example is the reaction of perfluorocyclopentene... 

With the aim of synthesizing new photochromic dihetarylethenes, viz., 5-substituted l,2-bis(thieno[3,2-Z)]thiophen-3-yl)perfluorocyclopentenes 181a-c, 2-(ben-zothiazol-2-yl)-6-bromo-5-methylthieno[3,2-fc]thiophene (182) was subjeeted to metallation. A mixture of lithium derivatives produced by this reaction was treated with octafluorocyclopentene (CsFg) (2000MI1, 2001IZV107). 

Reactions of perfluorocarbanions, from fluoro-olefins and alkali-metal fluorides, have been extensively studied during the period of this Report. During the course of a study of the reactions perfluorocycloalkyl anions with pentafluoropyridine and tetrafluoropyridazine it was found that caesium fluoride in tetramethylenesulphone at 125 °C caused the dimerization of perfluorocyclopentene to the dimer (76), per-fluorocyclohexene at 170 °C yielded dimer (77) (19, and, unexpectedly, the diene (78) (57%), which was, however, a minor product at 150 C, and perfluoroQrclo-butene at 125 °C yielded trimer (79). Reaction of CzFs", from tetrafluoro-... 

Abstract The review considers the synthesis and structures of photochromic products, in which hetaryl substituents are separated by the centtal 1,2-perfluorocyclopentene moiety. It was also briefly presented main methods for synthesis of octafluorocyclopentene and its reactivity. Among methods used for the synthesis of the photochromes, the reactions of hthium derivatives of thiophene, benzothiophene, and other heterocyclic compounds with octafluorocyclopentene, 1,2-dichlorohexafluorocyclopentene, and their analogues are described. Another general method for the synthesis of dihetarylethenes, considered in the review, is based on the McMurry reaction involving the initial... 

The reactions of OFCP with methylamine and ethylamine include both the addition-elimination reactions at the double bond and the simultaneous formation of products 12 with the imine fiagmoits (100 % yield for Alk=Me and 72 % for Alk=Et) [38], The formation of azochromophores 13 with the perfluorocyclopentene bridge, including the reaction of substance 4 with thiols as the first stage, was described in [39],... 

This direction is reasonably continued by the studies that described the reactions of OFCP with difunctional nucleophiles 14-17. Under mild conditions, these reactions were found to give a range of heterocycles with the perfluorocyclopentene fragment 18-22, respectively, generally in good yields [40]. 

Naturally, the reactions of OFCP accompanied by the formation of C-C bonds are most similar to the methods of preparation of photochromes described in Sect. 3. The treatment of 1 with organolithium reagents gave the corresponding symmetrical disubstituted perfluorocyclopentenes B (Scheme 4) in good to high yields. 

The main method for the preparation of perfluorocyclopentene DHE used in the majority of studies is the reaction of the lithium derivatives of thiophene with octafluorocyclopentene [43 5, 41]. The photochromic products are thus assembled from the components indifferent to butyllithium or the molecule backbone is formed for further functionalization. This approach allows one to synthesize both symmetrical and unsymmetrical photochromes. 

The reaction of the lithium derivatives of thiophene with 1 can be accompanied by the formation of the products of substitution of only one fluorine atom at the double bond of cyclene. For example, photochrome 37 was synthesized (Scheme 10) either in one stage with a twofold excess of the lithium derivative 35 over perfluorocyclopentene or in two stages with the preliminary isolation of monofluoride 36 [46]. 

A novel and efficient palladium-catalyzed direct diheteroarylation of 1,2-dichlorop erfluorocyclopentene with a variety of heteroarenes has recently been reported, giving rise to l,2-di(hetaryl)perfluorocyclopentene photochromic compounds 102. The reaction occurs with thiazoles, thiophenes, or furan derivatives and tolerates varions substituents [112] (Scheme 37). 

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