Polyfluoroalkyl ethers

Lewis acid catalysis has been used to promote stepwise [2 + 2] cycloaddition of silyl enol ethers and unsaturated esters.178 The best catalyst is (C2H5)2A1C1 and polyfluoroalkyl esters give the highest stereoselectivity. The reactions give the more stable trans products. 

Reactions of polyfluoroalkylchromones with (perfluoroalkyl)trimethylsilanes proceed as a 1,4-nucleophilic per-fluoroalkylation to give 2,2-bis(polyfluoroalkyl)chroman-4-ones with high regioselectivity and good yield after acid hydrolysis of trimethylsilyl (TMS) ethers (e.g., see Scheme 52) <2003JOC7747>. 

The ylide PhI=C(S02CF3)2 was exceptionally stable, melting at 140°C without decomposition. On irradiation in methanol, it gave the ether Me0CH(S02CF3)2 [10] however, this as well as some other photolytic reactions of such ylides with polyfluoroalkyl sulphonyl groups were not confirmed [2],... 

In the same way, substituted vinyl alcohols 93 are readily converted into 2-methyl-l,3,6-trioxocan propynyl-<2003RJ01384> or polyfluoroalkyl- <2002KGS1419> ethers (Equation 12), difficultly accessible by other methods. The cyclization is promoted by trifluoroacetic acid in boiling dry diethyl ether and affords high yields of the products. 

Formation of perfluorinated ethers by cobalt trifluoride is generally a low-yielding process, because of fragmentation and partial fluorination. However, incorporation into the substrate of electron-withdrawing polyfluoroalkyl groups moderates the fluorination and allows high yields to be obtained [78]. 

Zeng et al. [88] prepared a new class of geminal dicationic ILs with a bridging moiety, such as a poly alkyl ether, polyfluoroalkyl, 1,4-bismethylenebenzene, or... 

We also need to remember that polar effects have a considerable effect on reactivity in free—radical processes and therefore, introduction of a polyfluoroalkyl group should be significant. The question is, what is the effect on reactivity of the resultant ether, of introducing one polyfluoroalkyl group, towards the chain—transfer step, i.e. the ability of an intermediate radical to abstract a hydrogen atom from the ether, to give RH plus an ether derived radical, to continue the chain ... 

NaH dissolved portionwise in a soln. of 50-80% excess heptafluorobutanol in ether, which is then distilled off and replaced by an equal volume of toluene, the fluoroalkoxide suspended by stirring and gentle heating, cooled to room temp., a soln. of trim eric phosphonitrilic chloride in toluene added dr op wise with stirring during 30 min., and refluxed 4 hrs. after the exothermic reaction has ceased trimeric bis-l,l-di-H-heptafluorobutyl phosphonitrilate. Y 84%. — Polyfluoroalkyl phosphonitrilates possess remarkable chemical and thermal stability. F. e., also tetramers, s. R. Ratz et al.. Am. Soc. 8A, 551 (1962). 

Fluoroalkyl-l -pyrazoles 58 were synthesized in excellent yields in one-pot procedure starting from polyfluoroalkyl iodides 56 [30]. The treatment of 56 wi(h ethylvinyl ether led to their corresponding fluoroalkyl aldehyde intermediates 57, which upon condensation with hydrazine acetic acid under mild conditions gave pyrazoles 58 (Scheme 17). 

The propensity of a-pyrones to undergo the Diels-Alder reaction makes them useful for syntheses of highly substituted aromatics and biphenyls. A practical method for the regioselective synthesis of the A-benzoyl-4-(polyfluoroalkyl)ani-lines 82 by thermal Diels-Alder cycloaddition of 71 with fluorostyrenes and acetylenes was described. Free 4-(polyfluoroalkyl)anilines were smoothly formed in good yields by DBU-assisted deprotection. In the case of the reactions of pyrone 71a with isobutyl vinyl ethers and cyclic vinyl ethers, compounds 83 and 84 were obtained, respectively [36] (Scheme 26). 

The reactions of polyfluoroalk-2-ynoic acids with a fivefold excess of ArOH and KOH in an aqueous solution are stereoselective and result in (Z)-p-(polyfluoroalkyl)-P-aryloxyacrylic acids 142. On treatment with concentrated H2SO4, these compounds are converted into 2-R -chromones 130 [64]. A similar approach to the synthesis of 2-R -chromones 130 has been described in a study [65], in which ethyl 2,2-dihy-dropolyfluorocarboxylates were used as the starting substrates. They were made to react with phenols in the presence of EtsN in MeCN at 60 °C, which gave ethers 143, most often, as mixtures of Z- and f -isomers. When heated with polyphosphoric acid (PPA) at 170 °C, they were converted into chromones 130 in high yields (Scheme 44). 

U.v. irradiation of trifluoromethyl hypochlorite gives bistrifluoromethyl peroxide in 91% yield, together with chlorine and carbonyl fluoride, but similar decomposition of the next higher homologue yields essentially an equimolar mixture of carbonyl fluoride and chlorotrifluoromethane. Carbon monoxide, - sulphur dioxide, - and olefins - insert readily into the O—Cl bonds of polyfluoroalkyl hypochlorites to yield chloroformates, chlorosulphates, and ethers, respectively treatment of... 

Polyfluoroalkyl iodide (1 eq.) is added to a solution of bis(Af,A -bistrimethylsilylamino)-stannane(II) (1 g) in anhydrous THF (10 mL) under an argon atmosphere at room temperature. The reaction mixture is stirred at room temperature until the reaction mixture turned pale yellow. The solution is then concentrated in vacuo to furnish the corresponding Sn(IV) reagent. TBAF (5.9 mL, 3 eq., 1 M in THF) is then added in situ at room temperature. The reaction mixture is concentrated in vacuo before addition of anhydrous dioxane (8 mL), the catalyst (1 mol%) and iodobenzene (1.23 mmol. 0.6 eq.). The reaction mixture is heated at 101 °C for 105 min before cooling to room temperature. Removal of solvent in vacuo yields an oily residue, which is chromatographed on silica gel (petroleum ether) to give the cross-coupled product in 89% yield. ... 

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