From carboxylic acids to the trifluoromethyl group using BrF3

Article abstract of DOI:10.1016/j.tet.2010.03.045

Organic trifluoromethyl derivatives were made from aromatic and aliphatic carboxylic acids by transforming them first into the corresponding dithioesters followed by reaction with bromine trifluoride under mild conditions (0 °C, 2 min).

Full text of DOI:10.1016/j.tet.2010.03.045

Tetrahedron 66 (2010) 3579–3582
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Tetrahedron
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From carboxylic acids to the trifluoromethyl group using BrF3
,
Or Cohen a, Eyal Mishani b, Shlomo Rozen a
*
a School of Chemistry, Tel-Aviv University, Tel-Aviv 69978, Israel
b Radiochemistry, Hadassah Hospital, Hebrew University, 91120 Jerusalem, Israel
a r t i c l e i n f o
a b s t r a c t
Article history:
Organic trifluoromethyl derivatives were made from aromatic and aliphatic carboxylic acids by trans-
forming them first into the corresponding dithioesters followed by reaction with bromine trifluoride
under mild conditions (0 ꢀC, 2 min).
Received 13 November 2009
Received in revised form 22 February 2010
Accepted 15 March 2010
Ó 2010 Elsevier Ltd. All rights reserved.
Available online 20 March 2010
1. Introduction
the potential reaction center resulting in an overall substitution of
the nitrogen or sulfur atom(s) with fluorine (Scheme 1). Such
Compounds with the trifluoromethyl group enjoy high lipo-
philicity and increased stability compared to those with the methyl
moiety and since, for many applications, the added steric distortion
is not prohibitive, it is not surprising that this moiety can be found
in various fields of organic chemistry especially in pharmaceuticals,
anesthetics, agrochemicals, and polymers. Because of the intensive
interest and high demand quite a few methods for the in-
corporation of the whole CF3 group into organic molecules have
been developed, such as using the popular Prakash–Rupert’s re-
agent (CF3SiMe3),1 fluoroform,2 trifluoromethyl halides,3 and elec-
trophilic trifluoromethylations4 to mention just a few. Sulfur
tetrafluoride has also been used for constructing this desirable
moiety.5
Bromine trifluoride is a commercial reagent, but because of its
exothermic reactions with oxygen-containing solvents (see
Experimental section) it has been rarely utilized by organic
chemists.6 Nevertheless, in the last years we have shown that when
handled properly, it could be used under mild conditions for fast
and selective reactions. We found that it can brominate aromatic
rings, including very deactivated ones,7 transfer carbonyls to the
CF2 group,8 alcohols to trifluoromethyl or difluoromethyl ethers,9,10
or under a different set of conditions to the corresponding acyl
fluorides,11 help in transforming RX to RCHF2 derivatives,12 and
much more.13
complexation also reduces the chances of indiscriminate radical
brominations and fluorinations for which this reagent was so
infamous.15
Soft acid
F
F
F
Br
Soft base
R
F
F Br
F
S
R'
S R'
R
X
F
R
C
Z
C
Z
C
Z
or N
X
X
or N
R
O R'
BrF3
C
Z
No Reaction
X
Hard base
Scheme 1. The complexation of BrF3 with soft heteroatoms.
We describe in this work a new general method for trans-
forming the aromatic and aliphatic carboxylic acid moiety into the
important CF3 group. This is accomplished by changing the hard
basic oxygen with the soft sulfur atoms providing the much needed
‘anchor’ for the reagent enabling a selective reaction between the
resulting dithioesters derivatives and BrF3 for the eventual forma-
tion of the CF3 products. Earlier results for fluorodesulforization
processes with other [BrF] reagents (combination of two reactants,
such as NBS and various forms of HF) were accomplished only with
aromatic substrates.16
The majority of the regiospecific reactions involving bromine
trifluoride use the fact that the reagent’s bromine atom is a soft
acid, which can complex itself most effectively with soft bases, such
as nitrogen or sulfur atoms, but not with hard ones, such as oxy-
gen.14 The complexation positions the nucleophilic fluorides near
2. Results and discussion
Aromatic carboxylic acids 1 were converted to their acyl chlo-
* Corresponding author. Fax: 972
3 6409293; e-mail address: rozens@
post.tau.ac.il.
rides using oxalyl chloride, followed by a reaction with ethanethiol
0040-4020/$ – see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2010.03.045

3580
O. Cohen et al. / Tetrahedron 66 (2010) 3579–3582
to form the appropriate thioesters 2.17 These thiocarbonyl con-
taining derivatives were reacted with Lawesson reagent producing
the corresponding dithioesters 3, which were ready for the reaction
with BrF3. Thus, the dithioester of 4-cyanobenzoic acid 3a was
treated with 3 mole-equiv of bromine trifluoride for 2 min at 0 ꢀC to
give 4-(trifluoromethyl)benzonitrile (4a)18 in 75% yield.19 While
BrF3 is capable of transforming the nitriles themselves to CF3
moieties,20 the resulting 4a suggests that the reaction with the
dithioester group is more readily executed, since the soft–soft in-
teraction between bromine and sulfur is better than bromine and
nitrogen, so the cyano moiety was not affected (Table 1).
Table 2
Preparation of the trifluoromethyl moiety from aliphatic carboxylic acids
BrF
3
RCSSEt
RCF
3
RCOOH
7
8
9
Me
C8H17
a
70%
80
R
R
=
C6H13
Me
b
=
90%
70%
C10H21
Me
Me
Table 1
c
90%
95%
80%
65%
C
Preparation of the trifluoromethyl moiety from benzoic acid derivatives
R
=
1. (COCl)
2. EtSH
BrF
Lawesson
reagent
2
3
ArCSSEt
ArCF
4
ArCOOH
1
ArCOSEt
2
3
R =
C8H17
d
3
a
b
c
d
e
f
Ar¼4-CNC6H4
Ar¼4-ClC6H4
95%
95%
95%
95%
95%
95%
90%
75%
R
=
CH
e
f
85%
80%
45%
40%
90%
90%
90%
90%
90%
70%
70%
75%
75%
65%
C6H13
Ar¼2-ClC6H4
Ar¼3-BrC6H4
Ar¼4-BrC6H4
Ar¼4-CF3C6H4
Ar¼4-HOOCC6H4
Ar¼4-EtSSCC6H4
CH
R =
2
g
g0
95%
80%
30%
R =
R¼C11H23
g
80%
90%
35%
h
–
Traces
It is worth mentioning that BrF3 also possesses the ability to
exchange fluorine with other halogens.21 As with the previous case,
however, the halogen atom in the dithioesters of 4-chlorobenzoic
acid (1b), 2-chlorobenzoic acid (1c), 3-bromobenzoic acid (1d), and
4-bromobenzoic acid (1e), remained intact during the reaction with
bromine trifluoride, and the products 4b–e18 were obtained in 70–
75% yields.
In general the best results in the aromatic field were obtained
with compounds having a deactivated ringda feature, which
guards against aromatic electrophilic bromination. The deacti-
vated 4-(trifluoromethyl)benzoic acid (1f), satisfies this re-
quirement and eventually forms 1,4-bis(trifluoromethyl)benzene
(4f)18 in 65% yield. Alternatively this compound could be gener-
ated also from the terephtalic acid (1g), by converting it to its
tetrathio diester 3g0 followed by a reaction with 6 mole-equiv of
BrF3 to form the expected 4f. This result shows that the reaction is
applicable also for cases where more than a single carboxylic acid
group is present.
The reaction is not limited to aromatic carboxylic acids. Many
aliphatic ones can serve as substrates as well. The dithioesters 8a
and 8b, made from 2-hexyl-2-methyldecanoic acid (7a) and 2,2-
dimethyldodecanoic acid (7b), were reacted with BrF3 under the
same mild conditions outlined above resulting in the previously
unknown 7-methyl-7-(trifluoromethyl)pentadecane (9a) and 1,1,1-
trifluoro-2,2-dimethyldodecane (9b) in 80 and 70% yield, re-
spectively (Table 2). Cyclic carboxylic acids also work fine as can be
demonstrated by 1-methyl-1-cyclohexanecarboxylic acid (7c),
which was converted via its dithioester derivative (8c) to 1-methyl-
1-trifluoromethylcyclohexane (9c)22 in 80% yield.
In certain cases BrF3 can be engaged in electrophilic fluorina-
tions especially in the presence of tertiary hydrogen atoms.23 Yet,
when 1-adamantane carboxylic acid (8d) was reacted 1-(tri-
fluoromethyl)adamantane (9d)24 was formed without much elec-
trophilic substitution of the tertiary hydrogens. This may point out
to the substantial difference in the reactivity between centers that
provide a strong anchor for the reagent (in our case sulfur atoms)
and ones with much weaker complexation power.25 The fast re-
action completed under the mild conditions also ensures the in-
tegrity of the adamantane skeleton, which under harsh conditions,
or strong oxidants, can undergo various rearrangements.26
With secondary carboxylic acids the yields of transforming the
COOH group to the CF3 one are usually lower. This is evident from
several results among them the cases of 7-pentadecanoic acid (7e),
2,2-dicyclohexylethanoic acid (7f), and 2-adamantanecarboxylic
acid (7g), which were converted via their dithioesters 8e–g, to the
previously unknown, 7-trifluromethylpentadecane (9e), 1,1-dicy-
clohexyl-2,2,2-trifluoroethane (9f), and 2-(trifluoromethyl)adaman-
tane (9g)27 all in about 40% yield. This trend is even more profound
with primary acids, where dodecanoic acid 7h can serve as a typical
example. The reaction of its dithioester 8h28 with BrF3 resulted in
a mixture containing only traces of the 1,1,1-trifluoroundecane (9h).
We believe the reason for the different behavior of tertiary (and
aromatic), secondary and primary acids, is rooted in the fact that
the secondary, and even more so primary, dithioesters are prompt
to some degree toward tautomerism, which shifts the equilibrium
slightly more toward the enthiol structure. Obviously such process
cannot take place in the tertiary or aromatic derivatives. As we have
shown in the past, bromine trifluoride reacts very fast with any
type of double bond,29 which in this case leads mainly to non-
specific reactions (Scheme 2).
R'
R' SH
R C C SEt
R' S
R C C SEt
H
R C COOH
H
H
BrF3
BrF3
R'
R C CF3
H
tars
Scheme 2. The reaction with secondary and primary acid.
In conclusion, this work offers a new route for the formation of
the important trifluoromethyl group derived from carboxylic acid
derivatives using a simple sequence of reactions with the eventual
use of BrF3 as the source of the fluorine atoms. We hope that along
with the new synthetic pathway, this work will contribute to re-
duce the recoil of many chemists from the thought of using

O. Cohen et al. / Tetrahedron 66 (2010) 3579–3582
3581
bromine trifluoride and that more people will start considering it
when it comes to fluorination processes.
3.4.1. Ethyl 2-hexyl-2-methyl-decanedithionate (8a). Compound 8a
was prepared from ethyl 2-hexyl-2-methyl-decanethionate as de-
scribedabovein70%yield.1H NMR
1.31(3H, t, J¼7.4 Hz),1.28–1.12(24H, brs), 0.92–0.82 ppm(6H, m);MS
calcd: 330. Found: (using supersonic molecular beam) (m/z) 330 (M)þ
with isotope abundance analysis matching factor of 996 out of 999.
d
3.16 (2H, q, J¼7.4 Hz),1.40(3H, s),
3. Experimental section
3.1. General
1H NMR spectra were recorded using a 200 MHz spectrometer
with CDCl3 as a solvent and Me4Si as an internal standard. The 19F
NMR spectra were measured at 188.1 MHz using CFCl3 as an in-
ternal standard. The proton broadband decoupled 13C NMR spectra
were recorded at 100.5 MHz. Here too, CDCl3 served as a solvent
and Me4Si as an internal standard. Mass spectra were measured
under CI conditions. When EI conditions were needed we used Aviv
Analytical 5975-SMB-supersonic GC–MS. The main feature of this
method is to provide electron ionization while the sample is
vibrationally cooled in a supersonic molecular beam. This consid-
erably enhances the relative abundance of molecular ions.30,31 All
dithioesters were thus characterized using isotope abundance
analysis to confirm the structure. This analysis confirmed the pro-
posed elemental formulas as it ranked them all at the first place and
hence, as the best choice with very good matching factors of better
then 980 out of 999 (minimum match allowed 800).32
3.4.2. Ethyl 2,2-dimethyl-dodecanedithionate (8b). Compound 8b
was prepared from ethyl 2,2-dimethyl-dodecanethionate as de-
scribed above in 90% yield. 1H NMR
d
3.17 (2H, q, J¼7.5 Hz), 1.41 (6H,
s), 1.32 (3H, t, J¼7.5 Hz), 1.28–1.14 (18H, br s), 0.88 ppm (3H, t,
J¼6.9 Hz); MS calcd: 288. Found: (using supersonic molecular
beam) (m/z) 288 (M)þ with isotope abundance analysis matching
factor of 992 out of 999.
3.4.3. Ethyl 1-methyl-cyclohexanecarbodithionate (8c). Compound
8c was prepared from ethyl 1-methyl-cyclohexanecarbothionate as
described above in 90% yield. 1H NMR
d
3.19 (2H, q, J¼7.3 Hz), 2.80–
1.40 (13H, m), 1.31 ppm (3H, t, J¼7.3 Hz); MSCI (m/z) 203 (MþH)þ.
3.4.4. Ethyl 1-adamantanecarbodithionate (8d). Compound 8d was
prepared from ethyl 1-adamantanecarbothionate as described
above in 90% yield. 1H NMR
1.72 (6H, m), 1.30 ppm (3H, t, J¼7.4 Hz); MS calcd: 240. Found:
(using supersonic molecular beam) (m/z) 240 (M)þ with isotope
abundance analysis matching factor of 980 out of 999.
d
3.16 (2H, q, J¼7.4 Hz), 2.15 (9H, m),
3.2. Preparation and handling of BrF3
Although commercially available, we usually prepare BrF3 by
passing 0.6 mol fluorine through 0.2 mol of bromine placed in
a copper reactor and held at temperatures between 0 and þ10 ꢀC.
Under these conditions pure bromine trifluoride is obtained (can be
checked either by its melting point of þ9 ꢀC, or boiling point of
126 ꢀC) while the higher oxidation state of bromine, BrF5, will not
be formed in any appreciable amount.33 The reagent can be stored
in TeflonÒ containers indefinitely. BrF3 is a strong oxidizer and
tends to react very exothermically with water and oxygenated or-
ganic solvents, such as acetone or THF. Alkanes, like petrol ether,
cannot serve as solvents either since they also react quickly with
BrF3. Solvents, such as CHCl3, CH2Cl2, CFCl3 or, if solubility is not an
issue, any perfluoroalkane or perfluoroether can be used. Any work
using BrF3 should be conducted in a well ventilated area and cau-
tion and common sense should be exercised.
3.4.5. Ethyl 2-hexyl-decanedithionate (8e). Compound 8e was pre-
pared from ethyl 2-hexyl-decanethionate as described above in 85%
yield.1HNMR
d
3.23 (2H, q, J¼7.5 Hz), 3.12 (1H, quin, J¼5.0 Hz),1.41 (6H,
s),1.31 (3H, t, J¼7.5 Hz),1.27–1.18 (24H, br s), 0.91–0.82 ppm (6H, m);MS
calcd: 316. Found: (using supersonic molecular beam) (m/z) 316 (M)þ
with isotope abundance analysis matching factor of 993 out of 999.
3.4.6. Ethyl dicyclohexyl-dithioacetate (8f). Compound 8f was pre-
pared from ethyl dicyclohexyl–thioacetate as described above in
80% yield. 1H NMR
2.22–0.82 ppm (25H, m); MS calcd: 284. Found: (using supersonic
molecular beam) (m/z) 284 (M)þ with isotope abundance analysis
matching factor of 981 out of 999.
d
3.19 (2H, q, J¼7.5 Hz), 2.94 (1H, t, J¼7.5 Hz),
3.4.7. Ethyl 2-adamantanecarbodithionate (8g). Compound 8g was
prepared from ethyl 2-adamantanecarbothionate as described
above in 75% yield. 1H NMR
d
3.24 (2H, q, J¼7.5 Hz), 2.84 (1H, m),
3.3. General procedure for the formation of S-ethyl ester
2.20–1.45 (14H, m), 1.32 ppm (3H, t, J¼7.5 Hz); MS calcd: 240.
Found: (using supersonic molecular beam) (m/z) 240 (M)þ with
isotope abundance analysis matching factor of 980 out of 999.
An acyl chloride (40 mmol) was added to a solution of Et3N
(1.3 mole-equiv) and ethanethiol (2.1 mole-equiv) in dry THF
(100 mL). The reaction mixture was stirred under nitrogen over-
night. The white precipitate was filtered and the organic layer
concentrated to give the desired product in about 95% yield and
was used without further purification. Typical 1H NMR value for the
3.4.8. Ethyl dodecanedithionate (8h)28. Compound 8h was pre-
pared from ethyl dodecanethionate as described above in 90% yield.
SCH2 group is
d
2.85 ppm (2H, q, J¼7.5 Hz).
3.5. General procedure for reacting dithioesters with BrF3
3.4. General procedure for the formation of dithioesters
Dithioester (1–10 mmol) was dissolved in 10–20 mL of CFCl3
and cooled to 0 ꢀC. About 3 mole-equiv of BrF3 was dissolved in the
same solvent, cooled to 0 ꢀC and added dropwise to the reaction
mixture during 2 min. After the addition was completed, the re-
action was washed with aqueous Na2S2O3 solution until colorless.
The aqueous layer was extracted with CH2Cl2 and the organic layer
was dried over MgSO4. Evaporation of the solvent followed by flash
chromatography (using petroleum ether as eluent) gave the desired
trifluoromethyl derivative. Products 4a through 4f are commercial
and their spectroscopic data were identical to the corresponding
authentic samples. The reactions leading to those compounds were
performed on scale of 1.3–1.5 mmol of the corresponding
dithioesters 3 with yields of 70–75% (see Table 1).
Thioester (20 mmol) was dissolved in 20 mL of dry toluene. To
this solution, Lawesson reagent (0.6 mole-equiv) was added and
the suspension was refluxed under nitrogen for 16–20 h. The re-
action progress was monitored by GC and after completion the
suspension was cooled to room temperature and filtered. The fil-
trate was concentrated and flash chromatographed to give the
desired dithioester. The aromatic dithioesters and 8h are known
and referenced. It should be noted, however, that while the purity
of the thio and dithioesters achieved by this procedure was higher
than 90%, no efforts to obtain analytical purity were made since the
crude products were successfully used ‘as is’ for the next step.

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O. Cohen et al. / Tetrahedron 66 (2010) 3579–3582
3.5.1. 1,4-Bis(trifluoromethyl)benzene (4f). Compound 4f was pre-
pared from 3f (376 mg,1.5 mmol) as described above in 65% yield. It
was also prepared from 6 (430 mg, 1.5 mmol) and 6 mole-equiv of
BrF3 as described above in 30% yield.
Acknowledgements
This work was supported by the USA-Israel Binational Science
Foundation (BSF), Jerusalem, Israel.
3.5.2. 7-Methyl-7-trifluoromethylpentadecane (9a). Compound 9a
was prepared from 8a (496 mg, 1.5 mmol) as described above in
References and notes
80% yield as colorless oil. 1H NMR
d
1.52–1.35 (4H, m), 1.27 (20H, br
s), 1.04 (3H, s), 0.92–0.85 ppm (6H, m); 13C NMR
130.6 (q,
J¼284 Hz), 43.4 (q, J¼23 Hz), 34.5, 32.6, 32.4, 31.1, 30.8, 30.2, 30.0,
1. Prakash, G. K. S.; Krishnamurti, R.; Olah, G. A. J. Am. Chem. Soc. 1989, 111, 393.
2. Langlois, B. R.; Billard, T. Synth. 2003, 185.
3. (a) Ait-Mohand, S.; Takechi, N.; Medebielle, M.; Dolbier, W. R., Jr. Org. Lett. 2001,
26, 4271; (b) Shono, T.; Kise, N.; Oka, H. Tetrahedron Lett. 1991, 32, 6567.
4. Umemoto, T.; Ishihara, S. J. Fluorine Chem. 1998, 92, 181.
5. Wang, C.-L. J. Org. React. 1985, 34, 319.
6. For earlier works with BrF3 see: Michalak, R. S.; Wilson, S. R.; Martin, J. C. J. Am.
Chem. Soc. 1984, 106, 7529; Soelch, R. R.; Mauer, G. W.; Lemal, D. M. J. Org. Chem.
1985, 50, 5845.
7. Rozen, S.; Lerman, O. J. Org. Chem. 1993, 58, 239.
8. (a) Rozen, S.; Mishani, E.; Bar-Haim, A. J. Org. Chem. 1994, 59, 2918; (b) Cohen,
O.; Rozen, S. Tetrahedron 2008, 64, 5362.
9. Hagooly, Y.; Cohen, O.; Rozen, S. Tetrahedron Lett. 2009, 50, 392.
10. Ben-David, I.; Rechavi, D.; Mishani, E.; Rozen, S. J. Fluorine Chem. 1999, 97, 75.
11. (a) Rozen, S.; Ben-David, I. J. Fluorine Chem. 1996, 76, 145; (b) Cohen, O.; Sasson,
R.; Rozen, S. J. Fluorine Chem. 2006, 127, 433.
12. Sasson, R.; Hagooly, A.; Rozen, S. Org. Lett. 2003, 5, 769.
13. Rozen, S. Acc. Chem. Res. 2005, 38, 803.
14. Sasson, R.; Hagooly, A.; Rozen, S. Org. Lett. 2003, 5, 769.
15. In certain cases radical reactions with BrF3 could be useful as in the pyruvic acid
derivatives which were turned into compounds possessing a terminal CF3
group with one carbon less than the starting material: Sasson, R.; Rozen, S.
Tetrahedron 2005, 60, 1083.
16. Kuroboshi, M.; Hiyama, T. Chem. Lett. 1992, 5, 827.
17. Savarin, C.; Srogl, J.; Liebeskind, S. L. Org. Lett. 2000, 2, 3229.
18. This material is commercially available.
19. For a preliminary communication see: Rozen, S.; Mishani, E. J. Chem. Soc., Chem.
Commun. 1994, 2081.
20. Rozen, S.; Rechavi, D.; Hagooly, A. J. Fluorine Chem. 2001, 111, 161.
21. Rozov, L. A.; Huang, C. G.; Halpern, D. F.; Vernice, G. G.; Ramig, K. Tetrahedron:
Asymmetry 1997, 8, 3023.
22. Wolniewicz, A.; Dmowski, W. J. Fluorine Chem. 2001, 109, 95.
23. Boguslavskaya, L. S.; Kartashov, A. V.; Chuvatkin, N. N. Zh. Org. Khim. (Eng.
Transln.) 1989, 25, 1835.
24. Duddeck, H.; Spitzer, M.; Bolte, G. Liebigs Ann. Chem. 1985, 3, 545.
25. Rozen, S.; Gal, C. J. Org. Chem. 1987, 52, 4928.
d
24.2, 23.4, 20.1, 14.8, 14.7 ppm; 19F NMR
d
ꢁ75.1 ppm (s); HRMS (CI)
(m/z) calcd for C17H33F3¼293.2456 (MꢁH)þ, found 293.2455.
3.5.3. 1,1,1-Trifluoro-2,2-dimethyldodecane (9b). Compound 9b was
prepared from 8b (433 mg, 1.5 mmol) as described above in 70%
yield as colorless oil. 1H NMR
d 1.48–1.39 (2H, m), 1.27 (16H, br s),
1.07 (6H, q, J¼1 Hz), 0.88 ppm (3H, t, J¼7 Hz); 13C NMR
d 130.5 (q,
J¼283 Hz), 40.8 (q, J¼24 Hz), 36.4, 32.6, 31.0, 30.4, 30.3, 30.2, 30.0,
24.2, 23.4, 21.2, 14.8 ppm; 19F NMR
d
ꢁ78.9 ppm (s); HRMS (CI)
(m/z) calcd for C14H27F3¼251.1987 (MꢁH)þ, found 251.1981.
3.5.4. 1-Methyl-1-trifluoromethylcyclohexane (9c)22. Compound 9c
was prepared from 8c (2.02 g,10 mmol) as described above in 80% yield.
3.5.5. 1-Trifluoromethyladamantane (9d)24. Compound 9d was pre-
pared from 8d (313 mg, 1.3 mmol) as described above in 65% yield.
3.5.6. 7-Trifluoromethylpentadecane (9e). Compound 9e was pre-
pared from 8e (950 mg, 3 mmol) as described above in 45% yield as
colorless oil. 1H NMR
d
2.08–1.95 (1H, m), 1.65–152 (2H, m), 1.48–
1.24 (22H, m), 0.95–0.87 ppm (6H, m); 13C NMR
129.5 (q,
J¼280 Hz), 43.3 (q, J¼25 Hz), 32.6, 32.3, 30.4, 30.1, 30.0, 28.6, 27.6,
d
23.4, 23.3,14.8,14.7 ppm; 19F NMR
d
ꢁ70.6 ppm (d, J¼10 Hz); HRMS
(CI) (m/z) calcd for C16H31F3¼279.2300 (MꢁH)þ, found 279.2298.
26. Mlinaric-Majerski, K.; Veljkovic, J.; Kaselj, M.; Marchand, A. P. Eur. J. Org. Chem.
2004, 2923.
27. Alexandrov, A. M.; Sorochinskii, A. E.; Krasnoshchek, A. P. Zh. Org. Khim. (Eng.
Transln.) 1979, 15, 336.
28. Levesque, G.; Gressier, J. C.; Proust, M. Synth. 1981, 963.
29. Sasson, R.; Hagooly, A.; Rozen, S. J. Fluorine Chem. 2006, 127, 962.
30. Dagan, S.; Amirav, A. J. Am. Mass. Spectrom. 1995, 6, 120.
31. Amirav, A.; Gordin, A.; Tzanani, N. Rapid Commun. Mass Spectrom. 2001, 15, 811.
32. (a) Alon, T.; Amirav, A. Rapid Commun. Mass Spectrom. 2006, 20, 2579; (b)
Amirav, A.; Gordin, A.; Poliak, M.; Fialkov, A. B. J. Mass. Spectrom. 2008,
43, 141.
3.5.7. 1,1-Dicyclohexyl-2,2,2-trifluoroethane (9f). Compound 9f was
prepared from 8f (428 mg, 1.5 mmol) as described above in 40%
yield as colorless oil. dH 1.87–1.44 (13H, m), 1.39–1.00 ppm (10H,
m); dC 129.6 (q, J¼283 Hz), 54.7 (q, J¼22 Hz), 37.9, 33.1, 31.3, 27.8,
27.7, 26.9 ppm; dF ꢁ61.6 ppm (d, J¼12 Hz); HRMS (CI) (m/z) calcd
for C14H23F3¼247.1674 (MꢁH)þ, found 247.1670.
3.5.8. 2-Trifluoromethyladamantane (9g)27. Compound 9g was
prepared from 8g (962 mg, 4 mmol) as described above in 35% yield.
33. Lehmann, E.; Naumann, D.; Schmeisser, M. Z. Anorg. Allg. Chem. 1972, 388, 1.