2,2,2-Trifluoroethyl carbonate

Fluorinated carbonates were also used by Smart et al. as low-temperature cosolvents (Table 12), in the hope that better low-temperature performances could be imparted by their lower melting points and favorable effects on SEI chemistry. Cycling tests with anode half-cells showed that, compared with the ternary composition with nonfluorinated carbonates, these fluorinated solvents showed comparable and slightly better capacity utilizations at room temperature or —20 °C, if the cells were charged at room temperature however, pronounced differences in discharge (delithiation) capacity could be observed if the cells were charged (lithiated) at —20 °C, where one of these solvents, ethyl-2,2,2-trifluoroethyl carbonate (ETFEC), allowed the cell to deliver far superior capacity, as Figure 63 shows. Only 50% of the capacity deliverable at room temperature was... 

A similar technology for diphenyl carbonate with di(2,2,2-trifluoroethyl) carbonate and phenol in refluxing heptane containing sodium methoxide has been patented (ref. 16). 

As partially fluorinated EMC and DEC derivatives, 2-fluoroethyl methyl carbonate (FEMC), 2,2-difluoroethylmethyl carbonate (DFEMC), methyl 2,2,2-trifluoroethyl carbonate (TFEMC), ethyl 2-fluoroethyl carbonate (FDEC), ethyl 2,2-difluoroethyl carbonate (DFDEC), and ethyl 2,2,2-trifluoroethyl carbonate (TFDEC) in Scheme 2.7 were examined [4, 5, 39, 40]. These fluorinated EMC and DEC derivatives were synthesized by use of the corresponding three kinds of fluoroethanols and methyl chlorocarbonate or ethyl chlorocarbonate in the presence of pyridine. 

Symmetrical carbonates derived from phosgene and pyridine 1-oxide, di(l-pyridyl) carbonate 879 [640], or 2,2,2-trifluoroethanol, bis(2,2,2-trifluoroethyl) carbonate 880 [641], have been described. 

Fluorine-substituted carbonates have lower melting points than unsubstituted carbonates, and they have improved oxidation stability, which favors formation of a dense passivation SEl film on carbon negative electrode material. Some linear fluorine-containing carbonates are methyl 2,2,2-tri-fluoroethyl carbonate, ethyl 2,2,2-trifluoroethyl carbonate, propyl 2,2,2-tri-fluoroethyl carbonate, methyl 2,2,2-2, 2, 2 -hexafluoroisopropyl carbonate, ethyl 2,2,2-2, 2, 2 -hexafluoroisopropyl carbonate, and di-2,2,2-trifluoroethyl carbonate. Some cyclic fluorine-containing carbonates include fluoro-methyl ethylene carbonate (CH2F-EC), difluoromethyl ethylene carbonate (CHF2-EC), and trifluoromethyl ethylene carbonate (CF3-EC). They are miscible with EC, PC, and other organic solvents. The fluorinated cyclic... 

A simple approach for the resolution of chiral alcohols through a lipase-catalyzed transesterification of one enantiomer of the corresponding trifluoroethyl carbonate has been described [658]. (RS)-sec-Phenethyl alcohol is converted to its 2,2,2-trifiuoroethyl carbonate with CDI in 83% yield. 

DKR of esters bearing an electron-withdrawing group at the ot-carbon can be performed easily under mild reaction conditions due to the low pKa of the oc-proton. Tsai et al. have reported an efficient DKR of rac-2,2,2-trifluoroethyl ot-chorophenyl acetate in water-saturated isooctane [40]. They used lipase MY from C. rugosa for the KR and trioctylamine as the base for racemization. (R)-chlorophenylacetic acid was obtained in 93% yield and 89.5% ee (Figure 4.15). 

Characteristic proton and carbon data for compounds containing the trifluoroethyl group are given in Scheme 5.21. 

The proton and carbon NMR spectra of both of these trifluoroethyl systems are marked by the usual large two-bond F—H coupling constants, with the 1,2,2-trifluoro system exhibiting individual coupling constants from the A and B fluorines to the CHF2 carbon. Data for the proton and carbon spectra of both types of trifluoroethyl compounds are provided in Scheme 6.3. 

Since these methoxylated and acetoxylated sulfides have an acetal structure, it is expected that Lewis acid catalyzed demethoxylation should generate a carbocation intermediate which is stabilized by the neighboring sulfur atom. In fact, nucleophilic substitution with arenes has been successfully achieved as shown in Scheme 6.7 [43], This procedure is useful for the preparation of trifluoroethyl aromatics. As already mentioned, generation of carbocations bearing an a-trifluoromethyl group is difficult due to the strong electron-withdrawing effect. Therefore, this carbon-carbon bond formation reaction is remarkable from both mechanistic and synthetic aspects. 

In the thermal cyclization of 3-alkoxyphenyl A -(l-aryl-2,2,2-trifluoroethylidene)carbamates 287, obtained from 3-alkoxyphenols 285 and l-aryl-l-chloro-2,2,2-trifluoroethyl isocyanates 286, 2-aryl-2-trifluoromethyl-2,3-dihydro-477-l,3-benzoxazin-4-ones 290 were formed instead of the regioisomeric l,3-benzoxazin-2-ones 288 (Scheme 53). The formation of 290 was explained by a thermal isomerization of 287 involving a skeletal 1,3-rearrangement of the electron-rich aryloxy group to the azomethine carbon, which is electron deficient due to the electron-withdrawing CF3 group <2002JFC(116)97>. 

Sulfur also reacts with fluoroalkyl mercurials and fluoroalkyl iodides to give fluorothioacyl halides. In the case of the reaction with mercurials, the halide formed is determined by substitution on the carbon attached to mercury. For example, bis(perfluoroethyl)mercury gives trifluorothioacetyl fluoride and bis-(l,l-dichloro-2,2,2-trifluoroethyl)mereury gives trifluorothioacetyl chloride. 

The influence of various buffers on the solvolysis of 5-(trifluoromethanesulfonyloxy)pent-2-yne in anhydrous 2,2,2-trifluoroethanol at 25 C for 24 hours has been studied.24 Sodium and calcium carbonate, 2,6-dimethylpyridine, pyridine and quinoline all favored the formation of four-membered rings, whereas potassium carbonate, triethylamine and sodium 2,2,2-trifluo-roethoxide suppressed formation of the rearranged products. One of the solvolysis products is 2,2,2-trifluoroethyl-2-methylcyclobutenyl ether (see Section 8.A.2.I.). 

Characteristic proton and carbon data for compounds containing the trifluoroethyl group are given in Scheme 5.23. The series of 2-, 3-, and 4-butanamines provides insight regarding trends in proton chemical shifts. 

An example of CF3 bound to boron in a boronic ester is provided in Scheme 5.27, as is an example of a boronic ester with the CF3 group one carbon away. The fluorines of this trifluoroethyl group are perhaps the most deshielded of any CF3 group bound to a saturated carbon. 

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). 

The CHF carbon is chiral in 1,2,2-trifluoroethyl compounds. Thus, the fluorines of the CF2H group are diastereotopic and appear as an AB system, and each of the fluorines can potentially couple with... 

The good yield obtained in the last experiment of table 3-15 is notable, because the 2,2,2-trifluoroethyl vinyl carbonate has been proposed as useful monomer in optical fibers applications (Ref. 132). 

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