Perfluorinated derivatives

In a series of studies, perfluorinated derivatives containing thienothio-phene substituents were prepared. Thus, the synthesis of 76 (Scheme 24) was documented in 05KGS360. The synthesis of its isomeric analogs 77 and 78 (Scheme 25) was described in OlRCBllO. 

Alkyl(aryl)halonium ions (other than perfluorinated derivatives) were first prepared by Olah and Melby.368 When a S02 solution of iodobenzene was added to a S02 solution of the CH3F-SbF5 complex (methyl fluoroantimonate) at —78°C, a clear,... 

The Hiickel anti-aromaticity versus Mobius aromaticity effects for the seven-membered systems 1 and 2 have been studied computationally using Gaussian98 at the closed shell B3LYP/6-31G(d) level <20030BC182>. It was shown that Mobius aromaticity was preferred for the respective perfluorinated derivatives 3 and 4. 

To date, electrochemical fluorination has permitted only perfluorination on an industrial scale, and the selectivities (in some cases less than 50%) are frequently still unsatisfactory. In general, it has turned out that the perfluorinated derivatives are formed in better yields starting from already partially fluorinated compounds than starting from nonfluorinated ones. Up to the present, no electrochemical processes for controlled monofluorination do exist, although the scientific literature 7fi 77) contains some interesting suggestions (use of R3N xHF as electrolytes). 

For larger saturated rings only perfluorinated derivatives have been studied in the gas phase. No data have been reported for perfluorocyclopentane, and five-membered rings containing S(II), S(IV) and S(VI) are considered instead (Table 15). Within their experimental error limits, the C—F bond distances in these perfluorinated cyclic compounds are... 

Compound Boiling point (°C) [54] Boiling point of perfluorinated derivative (° C) Ref... 

Enormous reactivity increases along the series of perfluorinated derivatives of benzene, pyridine, pyrimidine, and vym-triazine, illustrating the dominat-... 

The successful generation of azetes from perfluorinated derivatives of 1,2,3-triazines has recently been described. Irradiation of the perfluorodi-isopropyl-l,2,3-triazine (40) gave a dimer (41) of the intermediate azete (42) which was also... 

An early report described the preparation in low yield of two isomeric meso-monofluorinated derivatives of porphyrins using the Schiemann reaction. Electrophilic fluorinating agents have been a more effective way to carry out direct fluorination of the porphyrin system. For example, reaction of octaethylporphyrin with A-fluoropyridinium salts such as A-fluoro-2,3,4,5,6-pentachloropyridinium triflate gave a mixture of mono, di, tri, and tetrafluoro derivatives 88 (Fig. 3.41). The perfluorinated derivative was formed in 20% yield. mew-Fluorination of octaethylporphyrin had minimal effects on oxidation potential and spectral properties. 

The synthesis of oxide 2 is quite complex and involves six steps.Two other perfluorinated derivatives of F-oxepine, compounds 5 and 6, were made by thermal isomerization of bicyclic compounds endo-3 and endo- and exo-A isomers of, prepared by reaction of Dewar-F-benzene with CF2(OF)2 under UV irradiation in 2% and 6% yield, respectively. At elevated temperature, both 3 and 4 undergo irreversible isomerization affording 5 and 6, respectively (Fig. 10.2). " ... 

Cyclic ethers such as tetrahydrofurans, 1,4-dioxane, and oxalanes subjected to ECF in anhydrous HF are converted into perfluorinated derivatives (Tables 19 and 20) (85JES2424, 67ZOB1229, 74ZPK590) (Scheme 53). 

ECF of A -methyl- and M-ethylcarbazole (current density 2.5-9.2 mA/dm, voltage 5.0-6.2V, temperature from —2 to 5°C, substrate concentration in anhydrous HF 5%) afforded perfluorinated derivatives with 10% and 17% yields, respectively (89DDRP2943133, 89JFC(45)93). The process occurs with cleavage of the benzene rings to form perfluorinated derivatives of tetrahydropyrrole (Scheme 65). 

Bicyehe nitrogen-containing heterocyclic compounds were also fluorinated by ECF. ECF of AT-methyl-decahydroquinoline forms a mixture of cis- and tra/j5-isomerie perfluorinated derivatives. Ring contraction and formation of per-fluorocyclohexanes are side processes. Trows-quinolizidine gives perfluoro-tra/w-quinolizidine (yield 16-23%) and a large amount of other compounds with unknown... 

ECF of azabicycloalkanes in anhydrous HF forms perfluorinated derivatives, which are also potential components of blood substitutes. Thus perfluoro-A -me-thylazatricyclodecane was obtained in 8.6% yield (69ZAAC62) (Scheme 78). Perfluorinated cyclic amines are formed from 2-azatricyclo-[4.2.2.1 ]undecane... 

Chambers RD, Findley AA, Philpot PD, Fielding HC, Hutchinson J, Whittaker G (1978) Perfluorinated derivatives of furan via novel cyclisation reactions of perfluoro-olefins. J Chem Soc Chem Commun 431 32... 

The first synthesis of a fluorinated corrole was of the perfluorinated derivative [34], The synthesis of selectively fluorinated corroles was published later in the same year [35], The alumina (in the case of the fluorinated corroles) most likely serves a dual role in the condensation, acting as both a catalyst and as a heterogeneous adsorbent to reduce the volatility of 3,4-difluoropyrrole. 

In natural product investigations, the most crucial decisions usually involve the choice of (i) derivative and (ii) ionization technique. The factors governing the choice of ionization method are the requirements for an abundant molecular ion (particularly in quantitative studies) and for diagnostic fragment ions. The derivative is chosen to fit in with the ionization method e.g. aromatic substituents to confer molecular stability in positive-ionization if necessary and perfluorinated derivatives to confer electron capture properties in negative ionization) and also, of course, to give suitable GC properties. Further discussion can be found in the sections on individual natural product classes below. 

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