Trifluoroethyl benzene

When the aryl group is one carbon farther from the CF3 group, as in (2,2,2-trifluoroethyl)benzene, it has virtually no influence upon the chemical shift of the CF3 group (Scheme 5.49). 

Okano and coworkers accomplished ATRA of very deactivated (l-bromo-2,2,2-trifluoroethyl)benzenes 224 with 1-octene 223 in the presence of 10 mol% CuCI and 20 mol% bipy 26 and obtained 18-81% of the atom transfer addition products 225 as a 2 1 syn/anti mixture (Fig. 56) [293],... 

At 320 °C, cesium tetrafluorocobaltate converts benzotrifluoride to m-fluo-robenzotrifluoride, 2H-heptafluorotoluene, octafluorotoluene, pertluoro-l-meth-ylcyclohexene, and perfluoromethylcyclohexane [29] l,3-Bis(trifluoromethyl)-benzene is convened at 420 °C to 4,5,6-trifluoro-1,3-bis(trifluoroethyl)benzene, perfluoro-l,3-dimethylbenzene, and perfluoro-l,3-dimethylcyclohexane [29]. p-Xylene gives at 350 °C l,4-bis(difluoromethyl)tetrafluorobenzene, 1-di-fluoroinethyl-3-trifluoromethyltetrafluorobenzene, perfluoro-l,3-dimethyl-benzene, and perfluoro-l,3-dimethylcyclohexane... 

Reaction of 2-cyanomethylpyridine with iV-(l-aryl-l-chloro-2,2,2-trifluoroethyl)-iV -(4-methylphenyl)carbodiimides, and with (1,1,2,2,2-pentachloro- and l,l-dichloro-2,2,2-trifluoroethyl)isocyanates or A-methoxycarbonyl-l,2,2,2-tetrachloro-, — l-chloro-2,2-trifluoroacetaldehyde imines afforded 3-aryl-4-cyano-l-(4-methylphenyl)imino-3-trifluoromethyl-2,3-dihydro-17/-pyrido[l,2-f]pyrimidines and 4-cyano-3-trichloro-, 4-cyano-3-trifluoro-17/-pyrido[l,2-4pyrimidin-l-ones, respectively <2004CHE47>. Refluxing 2-cyanomethylpyridine and iV-(l-aryl-l-chloro-2,2,2-trifluoroethyl)isocyanates in benzene furnished l-aryl-4-cyano-l-trifluoromethyl-l,2-dihydro-3//-pyrido[l,2-4pyrimidin-3-ones. However, when the solution of the isocyanate was added dropwise to the solution of 2-cyanomethylpyridine, and the reaction mixture was then treated with NEt at room temperature, the isomeric 3-aryl-4-cyano-3-trifluoromethyl-2,3-dihydro-l//-pyr-ido[l,2-dpyrimidin-l-ones were obtained. Reaction of l-(acetyl- and benzoylmethylene)-6,7-dimethoxy-l,2,3,4-tetra-hydroisoquinolines with PhCONCS yielded 1-acetyl-, 1 -benzoyl-9,10-dime thoxy-3-pheny 1-6,7-dihydro-2//-pyrimido[6,l- ]isoquinoline-2-thiones <2003SL2369>. 

Fig. 2.1.2. Mass chromatograms in the SIM mode using protonated molecular ions of LAS trifluoroethyl esters, (a) LAS standard mixture and (b) LAS found in a sediment. Peak labels indicate the position of the benzene sulfonate moiety on the linear alkyl chain. Reproduced with permission from Ref. [18]. 1997 by American Chemical...

A number of steroids have been regioselectively acylated in a similar manner (99,104). Chromobacterium viscosum lipase esterifies 5a-androstane-3p,17p-diol [571-20-0] (75) with 2,2,2-trifluoroethyl butyrate in acetone with high selectivity. The lipase acylates exclusively the hydroxy group in the 3-position giving the 3p-(monobutyryl ester) of (75) in 83% yield. In contrast, bacillus subtilis protease (subtilisin) displays a marked preference for the C-17 hydroxyl. Candida cylindracea lipase (CCL) suspended in anhydrous benzene regioselectively acylates the 3a-hydroxyl group of several bile acid derivatives (104). 

This fluorination methodology was extended to various para-svb-stituted phenyl 2,2,2-trifluoroethyl sulfides, 37b-d. These substances undergo efficient fluorination regardless of the benzene ring substituent. Fluorine is exclusively introduced at the position a to the trifluoromethyl group. Neither aromatic fluorination nor benzylic fluorination was observed (run 5, Table 13). The results are noteworthy... 

DesMarteau and coworkers reported the preparation, X-ray crystal structure and chemistry of trifluo-roethyliodonium salts 391 by the reaction of fluoroalkyliodo-bis(trifluoroacetates) 389 with benzene and triflimide acid (390) (Scheme 2.113) [68,531,532], The structure of trifluoroethyl(phenyl)iodonium salt 391 (n = 1) was established by a single-crystal X-ray analysis [68], In contrast to fluoroalkyliodonium triflates 383, compounds 391 are stable to water and can be used as reagents for fluoroalkylation reactions in aqueous media. 

A series on substituent effects on the solvolysis of l,l-diphenyl-2,2,2-trifluoroethyl systems has continued in a study of the effects of electron-donating substituents in the fixed aryl moiety. " The fixed substituent in one benzene ring was p-MeO, p-PhO, or p-Me, and the substituent in the other ring was varied. The substrates were chlorides and bromides, and the reactions were carried out in 80% aqueous ethanol at 25.0 °C. The substituent effects were complex and required detailed analysis through Hammett-Brown and Yukawa-Tsuno treatments. The complexities arise largely from the twisting of the aryl groups out of coplanarity. 

The chlorine atoms on the backbone of the polymer may be replaced by organic groups such as alkoxy, aryloxy, or amino groups. Most of these derivative polymers do not exhibit the hydrolytic instability of the parent polymer. In order to carry out the substitution, the chlorine-bearing polymer is added dropwise to a solution containing sodium alkoxide or aryloxide in a solvent snch as tetra-hydrofuran or benzene. A commercial rubber (PNF, Firestone Tire and Rubber Company) is based on alkoxides of trifluoroethyl alcohol or heptafluoroisobutyl alcohol [18]. 

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