Benzene 1,2,3,5-tetrafluoro

Question. List the symmetry elements of each of the following molecules (a) 1,2,3-trifluorobenzene, (b) 1,2,4-trifluorobenzene, (c) 1,3,5-trifluorobenzene, (d) 1,2,4,5-tetrafluoro-benzene, (e) hexafluorobenzene, (f) l,4-dibromo-2,5-difluorobenzene. 

Packer et al. (1981) found that y-irradiation reduces arenediazonium tetrafluoro-borates to aryl radicals. Packer and Taylor (1985) investigated the y-irradiation of 4-chlorobenzenediazonium tetrafluoroborate by a 60Co source in the presence of 1 alone or I- +13 . The major product in the presence of iodide was 4,4 -dichloroazo-benzene. With I- + 1 ", however, it was 4-chloroiodobenzene. Two other investigations of the reactivity of aryl radicals with iodine-containing species are important for the understanding of the chain process of iodo-de-diazoniation that starts after formation of the aryl radical. Kryger et al. (1977) showed that, in the thermal decomposition of phenylazotriphenylmethane, the rate of iodine abstraction from I2 is extremely fast (see also Ando, 1978, p. 341). Furthermore, evidence for the formation of the radical anion V2 was reported by Beckwith and Meijs (1987) and by Abey-wickrema and Beckwith (1987) (see Sec. 10.11). 

There are some reactions in which an aryl radical reacts with an sp2-carbon atom of an aliphatic side chain. In such reactions a carbo- or heteroalicyclic ring fused with a benzene ring is formed (Scheme 10-80). They may be called intramolecular Meerwein reactions. Techniques for these syntheses were developed by Beckwith s group in the 1980s. The majority of Beckwith s investigations were made with 2-(2 -propenyloxy)- and 2[(2 -methyl-2 -propenyl)oxy]benzenediazonium tetrafluoro-... 

We have also attempted to study the reactions of the tetrafluoro-o-phenylene di-radical (32) with benzene, by carrying out the photolysis of 1,2-di-iodotetrafluorobenzene in the presence of benzene. It is known that 1,2-di-iodoarenes give arynes on photolysis 70-72>. The only product derived immediately from o-dehydrotetrafluorobenzene was the 1,4-cyclo-adduct (24) which was, as expected, partially photoisomerised to (27) and a trace of (26) 73>. The photolysis resulted in the appearance of (24) and (27) before (26) was detected and hence we conclude that (26) was not a primary product. 

It is unlikely that the compound (27) is derived directly from the reaction of an excited benzene with tetrafluorobenzyne even though the compound (27) is formally analogous to the photo-adducts formed by the irradiation of olefins in benzene 74,75) A number of other products derived from the o-iodotetrafluorophenyl radical were also obtained 73>. These results suggest either that the tetrafluoro-o-phenylene di-radical (32) is identical with tetrafluorobenzyne or that if it is produced at a higher energy level it returns rapidly to the groundstate before it reacts with benzene. An alternative and perhaps more likely explanation is that the tetrafluorobenzyne formed arises by the concerted loss of both iodine atoms. 

The ruthenium cluster [Ru4H4(//6-C6H6)4]2+ was also employed for the hydrogenation of arenes in a biphasic water/l-butyl-3-methylimidazolium tetrafluoro-borate biphasic system. At 90°C and 60 bar H2, benzene was reduced to cyclohexane with a TOF of 364. 

Attempts were made not only to find an alternative way to replace dimer and to deposit high-quality poly(tetrafluoro-p-xylylene) film, but also to eliminate the dibromide as the precursor because of the difficulty of synthesis. Therefore, the deposition of poly(tetrafluoro-p-xylylene) film by using hexafluoro-p-xylene as the precursor instead of dibromotetrafluoro-p-xylene was tried. However, no polymer film was deposited on the wafer. Effort was expanded and other metal reagents such as nickel or copper were used to react with l,4-bis(trifluoromethyl)-benzene to generate a,a,a, a -tetrafluoro-p-xylylene to deposit poly(tetrafluoro-p-xylylene) film. However, the result showed that no film was deposited, which was not unexpected, because a C—X bond that is weaker than C—F bonding might be necessary to initiate the formation of the desired intermediate. 

Accidently, using hexafluoro-p-xylene with the contaminated copper wire obtained from the precursor method experiments, a polymer film was deposited on the silicon substrates. Obviously, some dibromotetrafluoro-p-xylene from the precursor method that adhered to, or reacted with, the metal could somehow initiate this VDP process. However, a complete explanation of these results is not yet available. As an extension of this discovery, commercially available 1,4-bis(trifluoromethyl)benzene in conjunction with a catalyst/initiator has proved to be a potential alternative by which to deposit poly(tetrafluoro-p-xylylene) film successfully.23... 

The reaction was also reported to occur thermally 4,4-dimethyl-2,3-diazabicyclo[3.2.0]hept-2-ene underwent nitrogen elimination to give 5,5-dimethylbicyclo[2.1.0]pentane (24) in benzene at 140°C.182 184 The kinetics of the reaction were measured. The mechanism of the thermal reaction of 5,5,6,6-tetrafluoro-2,3-diazabicyclo[3.2.0]hept-2-ene was also studied.185... 

Thus, electrofluorination of benzene in neat Et3N-3HF yields a mixture of fluorobenzene, p-difluorobenzene, trifluorocyclohexadiene, and tetrafluoro-cyclohexadiene [13]. 

Tetrafluoro-l-(trifluoromethyl)ethyl]benzenes 2 General Procedure 51... 

In contrast to linear unsaturated acids and anhydrides vide supra), 3,4,5,6-tetrahydrophthalic anhydride reacts with sulfur tetrafluoride to give mainly bicyclo products, lactone 31 and tetrafluoro ether 32, with the trifluoromethyl derivatives 33 and 34 as minor products. The ratio of products strongly depends on the reaction conditions at elevated temperature (> 150°C) cleavage of the C —O —C bond and dehydrogenation occur resulting in l,2-bis(tri-fluoromethyl)benzene (35) in high yield.252... 

When tetrafluoro(phenyI)-25-stibane is used, all the chlorine atoms in (pentachloroethyl)ben-zene (8) and (l,l-dichlorotrifluoroethyl)benzene (10) are substituted by fluorine to give (pen-tafluoroethyljbenzene (9) in 48-50% yield.104... 

To a solution of l,l,2,2-tetrafluoro-3-(tosyloxy)propane (0.86 g, 3 mmol) in THF was added dropwise 1.6M BuLi in hexane (4.1 mL, 6.6 mmol) at — 78°C over 20 min under argon. After lOmin at — 78 "C, the reaction was quenched with cold 10% aq HC1. Extraction, drying, concentration, and column chromatography (benzene) give a pale-yellow syrup yield (70%) (E/Z) 14 86. The procedure can also be applied to a 15-mmol scale. 

Perfluorobenzene and ethylene glycol can react to give, according to the conditions used, 2-(pentafluorophenoxy)ethanol (12),89 l,2,4,5-tetrafluoro-3,6-bis(2-hydroxyethoxy)benzene (14),90 and 5,6,7,8-tetrafluoro-2,3-dihydro-l,4-benzodioxin (13).89... 

Perfluoro(ethylbenzene) reacts with sodium methoxide to afford 1,2,4,5-tetrafluoro-3-methoxy-6-(pentafluoroethyl)benzene (21).95... 

The reaction of sodium methoxide with pentafluoro(methyl)benzene occurs mainly in the para position relative to the methyl group to give tetrafluoro-3-methoxy-6-methylbenzene (23).97... 

Tetrafluoro-3,6-bis[2,3,5,6-tetrafluoro-4-(trifluoromethyl)phenoxy]benzene by a similar method gives l,2,4,5-tetrafluoro-3,6-bis(4-carboxy-2,3,5,6-tetrafluorophenoxy)benzene (5).165... 

Perfluorobenzene and excess potassium 2,3,5,6-tetrafluorobenzencthiolate, refluxed in pyridine for six hours, gives tetrafluoro-1,4-bis(2.3,5,6-tetrafluorophenylsulfanyl)benzene in 79% yield an analogous product is formed using potassium benzenethiolate (1 2 ratio) after refluxing for only 10 minutes, but a 1 4 ratio of reactants refluxed for 25 minutes affords 1,4-difluorotetrakis(phenylsulfanyl)benzene.66... 

Multiple replacement of fluorine atoms in polyfluorobenzenes by phenylsulfanyl groups is accomplished most successfully by using heavy metal salts of benzenethiol, especially by the nickel(II) salt,54 using the same reaction conditions as described above for the synthesis of l,2,4,5-tetrafluoro-3-(phcnylsulfanyl)benzene derivatives from pentafluorobenzenes and the lead(II) salt of benzenethiol, but with an increased amount of thiolate (Table 5). 

Cl —benzene (- CoF,) 6-Chloro-3,3.6-trifluaro- ElOa. 311 (Cl-benzene + HF e j) 1-Cyano-3,3,6,6-tetrafluoro- ElOa. 675 (NC-aren + CoF3)... 

Tetrafluoro- EI0b2, 71 (Educt) Benzene-1,x-disulfonic Dilluoride... 

The compound (dppe)PtMe(OMe),256 which is prepared by a metathesis reaction involving NaOMe and (dppe)PtMe(Cl) in a mixed benzene/methanol solvent system (dppe = bis(l,2-di-phenylphosphino)ethane), does not react with ethylene or pentene but does react with activated alkenes such as acrylonitrile, methylacrylate and fluoroalkenes. The reaction involving tetrafluoro-ethylene has been shown to give (dppe)PtMe(CF2CF2OMe), providing the first example of an alkene insertion into an M—OR bond.256 Interestingly, no insertion into the Pt—Me bond was observed. 

Cyclohexene reacts with tetrafluoroethylene and sulfur to give 4,5 -tetramethylene- 2,2,3,3-tetrafluorothiolane (2,2,3,3-tetrafluoro-octahydrobenzo[6]thiophene) (32).249 Tetrafluoroethylene and sulfur also react with benzene to give mainly perfluorothiolane, together with some 2,2,3,3-tetrafluoro-2,3,3a,7a-tetrahydrobenzo[i>]thiophene (33) and the dihydro derivative (34)250 in the presence of iodine more complex products are obtained.251... 

N-Methyl-2-pyrrolidone Ferric chloride hexahydrate Glycol monomethyl ether Lithium aluminum hydride Ruthenium on charcoal Magnesium ethoxide 4-Toluenesulfonic acid Sodium bicarbonate 1,2,3,4-Tetrafluoro benzene Palladium on charcoal Cyclopropylamine N-benzylimide... 

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