Convenient syntheses of 1,1,1,3,3,3-hexafluoro-2-organyl-propan-2-ols and the corresponding trimethylsilyl ethers

Article abstract of DOI:10.1016/j.tet.2004.12.023

A new convenient synthetic procedure to obtain various 1,1,1,3,3,3- hexafluoro-2-organyl-propan-2-ols and the corresponding trimethylsilyl ethers has been worked out starting from anhydrides or activated esters of carboxylic acids and trimethyl(trifluoromethyl)silane in the presence of tetramethylammonium fluoride. Conditions for the selective formation of 1,1,1,3,3,3-hexafluoro-2-organyl-propan-2-ols as well as the trimethylsilyl derivatives have been found.

Full text of DOI:10.1016/j.tet.2004.12.023

Tetrahedron 61 (2005) 1813–1819
Convenient syntheses of
1,1,1,3,3,3-hexafluoro-2-organyl-propan-2-ols and the
corresponding trimethylsilyl ethers
b
b
L. A. Babadzhanova,a N. V. Kirij,a Yu. L. Yagupolskii,a, W. Tyrra and D. Naumann
*
aInstitute of Organic Chemistry, National Academy of Sciences of Ukraine, 5 Murmanskaya St., UA-02094 Kiev 94, Ukraine
b
¨
¨
¨
¨
Institut fur Anorganische Chemie, Universitat zu Koln, Greinstrasse 6, D-50939 Koln, Germany
Received 26 August 2004; revised 9 December 2004; accepted 9 December 2004
Available online 12 January 2005
Abstract—A new convenient synthetic procedure to obtain various 1,1,1,3,3,3-hexafluoro-2-organyl-propan-2-ols and the corresponding
trimethylsilyl ethers has been worked out starting from anhydrides or activated esters of carboxylic acids and trimethyl(trifluoromethyl)silane
in the presence of tetramethylammonium fluoride. Conditions for the selective formation of 1,1,1,3,3,3-hexafluoro-2-organyl-propan-2-ols as
well as the trimethylsilyl derivatives have been found.
q 2004 Elsevier Ltd. All rights reserved.
1. Introduction
During the past 15 years, trimethyl(trifluoromethyl)silane
has been widely used for the introduction of trifluoromethyl
groups into organic compounds.9–11 Only few examples of
1,1,1,3,3,3-hexafluoro-2-organyl-propan-2-ols have been
prepared from trifluoromethylketones and trimethyl-
(trifluoromethyl)silane in the presence of fluoride-ion
sources.9–11
A series of 1,1,1,3,3,3-hexafluoro-2-organyl-propan-2-ols
was established in 1960.1 Benzene derivatives with
2-hydroxy-1,1,1,3,3,3-hexafluoropropyl groups have been
widely used as polymerisation sources for obtaining epoxy
resins and urethane coatings.2 Some years later it was found
that such derivatives can be used for the stabilisation of
hypervalent compounds.3,4 Increased interest in fluorinated
alcohols arose when they were used as intermediates for
producing biologically active substances. In particular,
compounds of different compositions, all containing the
hydroxy-hexafluoro-2-propyl group, exhibited regulatory
properties for plants growth, fungicidal, and also anti-
arhythmic and antithrombotic activities5 as liver X-receptor
(LXR) modulators.6 The lack of suitable and effective
synthetic procedures has prevented the development of this
field of organic chemistry so far.
To our knowledge, reactions of trimethyl(trifluoromethyl)-
silane in the presence of fluoride ions with carboxylic acids
anhydrides and activated esters have not been mentioned in
the literature. It should be noted that commercial accessi-
bility of a number of anhydrides of various carboxylic acids,
as well as simple preparation of activated esters make these
compounds considerably attractive for nucleophilic
trifluoromethylations.
In this paper, we report a new and convenient synthetic
method to prepare 1,1,1,3,3,3-hexafluoro-2-organyl-propan-
2-ols and the corresponding trimethylsilyl ethers, based on
the interaction of carboxylic acids anhydrides and activated
esters with trimethyl(trifluoromethyl)silane in the presence
of different amounts of fluoride ions.
The major number of aliphatic and aromatic 1,1,1,3,3,3-
hexafluoro-2-organyl-propan-2-ols have been prepared
from the appropriate organomagnesium compounds and
hexafluoroacetone.1,7 Electrophilic reactions of activated
aromatic or heterocyclic compounds with hexafluoro-
acetone offer an alternative access.5,8
2. Results and discussion
Keywords: Trifluoromethylation; Synthesis; Alcohols; Trimethylsilyl
ethers; 2-Hydroxy-1,1,1,3,3,3-hexafluoropropyl.
* Corresponding author. Tel.: C38 044 5590349; fax: C38 044 5436843;
e-mail: yurii@fluor-ukr.kiev.ua
As a model reactant, we chose benzoic acid anhydride 1a.
In the reaction of 1 equiv of 1a, 2 equiv of Me3SiCF3
and 1 equiv of [Me4N]F in dimethoxyethane,
0040–4020/$ - see front matter q 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2004.12.023

1814
L. A. Babadzhanova et al. / Tetrahedron 61 (2005) 1813–1819
trimethyl[2,2,2-trifluoro-1-phenyl-1-(trifluoromethyl)-
ethoxy]silane 2a was formed in 82% yield (Scheme 1).
From the anhydrides investigated, the reaction with
trifluoroacetic acid anhydride 1f gave a product mixture
by 19F NMR. Only after addition of a second equivalent of
[Me4N]F, the tetramethylammonium salt of 1,1,1,3,3,3-
hexafluoro-2-(trifluoromethyl)propan-2-ol was selectively
formed. This might be attributed to the low nucleophilicity
of the trifluoroacetate anion which unlike the others does not
initiate the consecutive reaction with the second equivalent
of Me3SiCF3. Finally, acidification gave the alcohol 3f in an
overall yield of 87% (Scheme 4).
Scheme 1.
[Me4N]F initiates the reaction of Me3SiCF3 with 1a. Later
on, trifluoromethylation is forwarded by the concomitant
product, tetramethylammonium benzoate. It must be noted
that the nucleophilicity of the benzoate ion as an initiator is
sufficiently high for the introduction of the second CF3-
group into the molecule (i.e. in the reaction with a,a,a-
trifluoroacetophenone formed in the first step), while
substitution of the benzoate moiety would require fluoride
ions as activators. In comparative experiments, 1a and
a,a,a-trifluoroacetophenone were reacted with Me3SiCF3
and [Me4N]OCOPh in separate entries. While no reaction
was observed with 1a, a,a,a-trifluoroacetophenone was
selectively transferred into 2a (Scheme 2).
Scheme 4.
This procedure opens a convenient alternative route to
1,1,1,3,3,3-hexafluoro-2-(trifluoromethyl)propan-2-ol start-
ing from relatively inexpensive trifluoroacetic acid
anhydride, in contrast to the previously developed method
requiring hexafluoroacetone.12
Procedures for obtaining 1,1,1,3,3,3-hexafluoro-2-organyl-
propan-2-ols are based on treatment of the trimethylsilyl
ethers or the tetramethylammonium salts with hydrochloric
acid in tetrahydrofuran solution13 which was exemplary
studied in reactions with 1a yielding the alcohol 3a
(Scheme 5, Table 1).
Scheme 2.
On the basis of the results obtained, we extended our
attempts onto the anhydrides of aromatic, aliphatic, and
heterocyclic acids, as well as tert-butyl carbonic anhydride,
and succeeded in obtaining the corresponding trimethylsilyl
ethers 2b–e in high yields (Scheme 3, Table 1) proving that,
again, the carboxylates formed during these reactions
initiate formal addition of Me3SiCF3 to the carbonyl
function of trifluoromethyl ketones.
Unfortunately, anhydrides of some carboxylic acids are
extremely difficult to synthesise, i.e. pyridine carboxylic
acids anhydrides. In these cases, we applied a method
nowadays frequently used in peptide synthesis.14–16 For our
purposes, we synthesised a series of highly reactive
pentafluorophenyl esters and 1-benzoyl imidazole. These
¨
may be regarded as ‘mixed’ anhydrides of two Bronsted
acids, a carboxylic acid and a phenol or imidazole,
respectively.
Pentafluorophenyl esters of benzoic 4a, pyridinecarboxylic
4g–i and 3-phenyl-acrylic 4j acids were prepared in high
yields by reacting the corresponding carboxylic acids and
pentafluorophenol in the presence of 1,3-dicyclohexyl-
carbodiimide (DCC) (Scheme 6).17
Scheme 3.
Table 1. Conversion of anhydrides 1a–f into 1,1,1,3,3,3-hexafluoro-2-
organyl-propan-2-ols 3 and the corresponding trimethylsilyl ethers 2
Substrate
R
[Me4N]F
(equiv)
Product
Yield (%)
In subsequent reactions, the pentafluorophenyl esters 4a,g–j
were treated with Me3SiCF3 in the presence of [Me4N]F
under comparable conditions as used for the anhydrides.
After adding 2 equiv of trimethyl(trifluoromethyl)silane and
1 equiv of tetramethylammonium fluoride to solutions of the
pentafluorophenyl esters, the corresponding trimethylsilyl
ethers 2a,g–j were obtained in high yields (Scheme 7,
Table 2).
1a
1a
1b
1c
1d
1e
1f
Ph
Ph
1
2
1
1
1
1
2
2a
3a
2b
2c
2d
2e
3f
82
81
88
62
75
50
87
1-Naphthyl
Me
2-Furyl
t-BuO
CF3

L. A. Babadzhanova et al. / Tetrahedron 61 (2005) 1813–1819
1815
Scheme 5.
substituent. As expected, 1-benzoyl imidazole 5 was
converted into the trimethylsilyl ether 2a or the alcohol 3a
under respective conditions in comparable high yields
(Scheme 8, Table 2).
Despite of the fact that numerous papers deal with reactions
of Me3SiCF3 in the presence of nucleophilic initiators with
carbonyl group-containing compounds,9–11 the formation of
trimethyl[2,2,2-trifluoro-1-phenyl-1-(trifluoromethyl)-
ethoxy]silane 2a starting with benzoyl chloride has only
been mentioned once.18 Bis(trifluoromethyl)cadmium com-
plexes react with aromatic acid chlorides in the presence of
strong bases to form both trifluoromethylaryl ketones and
1,1,1,3,3,3-hexafluoro-2-aryl-propan-2-ols.19
Scheme 6.
To compare the reaction behaviour of Cd(CF3)2
complexes and the Me3SiCF3/[Me4N]F system, we studied
Scheme 7.
Table 2. Conversion of pentafluorophenyl esters 4 and 1-benzoyl imidazole 5 into 1,1,1,3,3,3-hexafluoro-2-organyl-propan-2-ols 3 and the corresponding
trimethylsilyl ethers 2
Substrate
R
Me4NF (equiv)
Product
Yield (%)
4a
4a
4g
4h
4i
4j
5
Ph
Ph
1
2
1
1
1
1
1
2
2a
3a
2g
2h
2i
2j
2a
3a
92
81
52
72
60
81
94
87
2-C5H4N
3-C5H4N
4-C5H4N
trans-PhCHZCH
Ph
5
Ph
Both 1a (see above) and 4a in reactions with 2 equiv of
Me3SiCF3 and 2 equiv of [Me4N]F after acidification gave
3a in very good yield.
the reactions with the aroyl chlorides, benzoyl chloride 6
and terephthaloyl chloride 7. Benzoyl chloride 6, 2 equiv of
Me3SiCF3 and 2 equiv of [Me4N]F in DME selectively gave
the tetramethylammonium salt of 1,1,1,3,3,3-hexafluoro-2-
phenylpropan-2-ol which was converted into 3a by
acidification in 77% yield.
Effects on the activation of the carbonyl function are
comparable for both the OC6F5 group and the imidazole
Scheme 8.

1816
L. A. Babadzhanova et al. / Tetrahedron 61 (2005) 1813–1819
Scheme 9.
In a similar manner, terephthaloyl chloride 7 reacts with
4 equiv of trimethyl (trifluoromethyl)silane and 4 equiv of
tetramethylammonium fluoride with formation of the
bis(tetramethylammonium) salt of 1,1,1,3,3,3-hexafluoro-
2-[4-(2,2,2-trifluoro-1-hydroxy-1-(trifluoromethyl)ethyl)-
phenyl]propan-2-ol which upon treatment with hydrochloric
acid was transferred into the corresponding alcohol 8 (82%
yield) (Scheme 9).
Melting points were measured in one-end open glass
capillaries and are uncorrected.
4.2. Pentafluorophenyl esters (4a,g–j); general
procedure
To a mixture of the appropriate acid (10 mmol) and
pentafluorophenol (2.00 g, 11 mmol) in dioxane (30 mL),
1,3-dicyclohexylcarbodiimide (DCC) (2.27 g, 11 mmol)
was added. The mixture was stirred for 1 h at room
temperature. Dicyclohexylurea formed was filtered off, the
solvent was evaporated under reduced pressure and the
residue was purified by crystallisation from hexane.
It should be mentioned that benzene derivatives substituted
with two hydroxy-hexafluoro-2-propyl groups are of interest
as building blocks e.g. in polysiloxane chains.20 Therefore,
the search for selective and efficient synthetic methods for 8
and related compounds can be regarded as one of
considerable interest.
4.2.1. Benzoic acid pentafluorophenyl ester (4a). Yield:
2.45 g (86%); colourless solid; mp 75–76 8C (lit.26 mp 74–
75 8C); dH (299.95 MHz, acetone-d6) 8.26 (2H, dd, JZ8.6,
1.6 Hz), 7.87 (1H, tt, JZ7.5, 1.4 Hz), 7.70 (2H, td, JZ7.9,
1.6 Hz); dF (282.20 MHz, acetone-d6) K154.1 (2F, d, JZ
18.4 Hz), K159.3 (1F, t, JZ21 Hz), K163.8 (2F, t, JZ
20.5 Hz).
3. Conclusion
A new, convenient and efficient synthesis for 1,1,1,3,3,3-
hexafluoro-2-organyl-propan-2-ols has been developed
starting from carboxylic anhydrides, activated esters,
carboxylic acid chlorides and trimethyl(trifluoromethyl)-
silane in the presence of tetramethylammonium fluoride. In
a two-step reaction-substitution followed by addition to the
carbonyl double bond-the title compounds are formed
highly selectively in excellent yields.
4.2.2. Pyridine-2-carboxylic acid pentafluorophenyl
ester (4g). Yield: 2.20 g (76%); colourless solid; mp 64–
65 8C (lit.17 mp 62–64 8C; lit.27 mp 61–63 8C); dH
(299.95 MHz, CDCl3) 8.87 (1H, dq, JZ4.8, 0.9 Hz), 8.34
(1H, d, JZ7.8 Hz), 8.01 (1H, td, JZ7.8, 1.8 Hz), 7.68 (1H,
ddd, JZ7.8, 4.8, 1.0 Hz); dF (282.20 MHz, CDCl3) K152.6
(2F, d, JZ21 Hz), K157.9 (1F, t, JZ21.5 Hz), K162.0 (2F,
t, JZ20 Hz).
4. Experimental
4.2.3. Pyridine-3-carboxylic acid pentafluorophenyl
ester (4h). Yield: 1.94 g (67%); colourless solid; mp 62–
63 8C; [Found: C, 49.7; H, 1.5; F, 33.1; N, 4.9. C12H4F5NO2
requires C, 49.84; H, 1.39; F, 32.85; N, 4.84%]; dH
(299.95 MHz, CDCl3) 9.41 (1H, dd, JZ1.8, 0.8 Hz), 8.93
(1H, dd, JZ5.0, 1.6 Hz), 8.48 (1H, dt, JZ8.1, 1.8 Hz), 7.54
(1H, ddd, JZ8.1, 5.0, 0.8 Hz); dF (282.20 MHz, CDCl3)
K152.7 (2F, d, JZ20 Hz), K157.3 (1F, t, JZ21.5 Hz),
K162 (2F, t, JZ21.3 Hz).
4.1. Materials and methods
All reactions were carried out in a dry argon (or nitrogen)
atmosphere using Schlenk techniques.
Me3SiCF3 was purchased from ABCR, di-tert-butyldicar-
bonate from Fluka, 1,3-dicyclohexyl-carbodiimide (DCC),
C6F5OH, all anhydrides and carboxylic acids from Aldrich.
The following products were synthesised according to
literature procedures: [Me4N]F,21 2-furan carboxylic acid
anhydride,22 1-naphthalene carboxylic acid anhydride,23
1-benzoyl imidazole.24 All solvents were purified according
to literature procedures.25
4.2.4. Pyridine-4-carboxylic acid pentafluorophenyl
ester (4i). Yield: 2.08 g (72%); colourless solid; mp 53–
54 8C (lit.27 mp 52–54 8C); dH (299.95 MHz, CDCl3) 8.91
(2H, dd, JZ4.5, 1.6 Hz), 8.00 (2H, dd, JZ4.5, 1.6 Hz); dF
(282.20 MHz, CDCl3): K152.7 (2F, d, JZ18.5 Hz),
K156.9 (1F, t, JZ21.7 Hz), K161.8 (2F, t, JZ19.5 Hz).
13C{1H} NMR spectra (50.32 MHz) were recorded on a
Bruker AC-200 spectrometer, 1H (299.95 MHz) and 19F
(282.20 MHz) NMR spectra on a Varian VXR-300
spectrometer. Chemical shifts are given in ppm relative to
Me4Si and CCl3F as external standards. EI mass spectra
were run on a Finnigan MAT 95 spectrometer (20 eV).
4.2.5. 3-Phenyl acrylic acid pentafluorophenyl ester
(4j).14 Yield: 2.86 g (91%); colourless solid; mp 87–
88 8C; [Found: C, 57.6; H, 2.3; F, 30.1. C15H7F5O2 requires
C, 57.33; H, 2.25; F, 30.23%]; dH (299.95 MHz, CDCl3)

L. A. Babadzhanova et al. / Tetrahedron 61 (2005) 1813–1819
1817
7.95 (1H, d, JZ16 Hz), 7.60 (2H, d, JZ5.7 Hz), 7.46 (2H,
s), 7.44 (1H, t, JZ5.7 Hz), 6.64 (1H, d, JZ16 Hz); dF
(282.20 MHz, CDCl3) K153.1 (2F, d, JZ18.5 Hz),
K158.7 (1F, t, JZ21 Hz), K163.0 (2F, t, JZ20.2 Hz).
Me3SiF-F]), 167 (26, [MKCF3H–CF3]), 145 (6), 117 (10),
95 (28, [MKMe3SiCF3–CF3]), 77 (8), 73 (7, [Me3Si]), 18
(100, [H2O]).
4.3.5. Trimethyl[1-tert-butoxy-2,2,2-trifluoro-1-(tri-
fluoromethyl)ethoxy]silane (2e). Yield: 0.78 g (50%);
colourless liquid; bp 63 8C/15 Torr; [Found: C, 38.6; H,
6.0; F, 36.3. C10H18F6O2Si requires C, 38.45; H, 5.81; F,
36.50%]; dH (299.95 MHz, C6D6) 1.29 (9H, s, C(CH3)3),
0.16 (9H, s, Si(CH3)3); dF (282.0 MHz, C6D6) K79.8; dC
4.3. Trimethyl[2,2,2-trifluoro-1-organyl-1-(trifluoro-
methyl)ethoxy]silane (2a–j); general procedure
To a solution of the appropriate substrate (5 mmol) in
dimethoxyethane (DME) (8 mL) at K50 8C trimethyl(tri-
fluoromethyl)silane (Me3SiCF3) (1.50 g, 10.5 mmol) and
tetramethylammonium fluoride ([Me4N]F) (0.47 g,
5.0 mmol) were added. The mixture was stirred for 1 h at
K30 8C and then overnight at room temperature. H2O
(25 mL) was added and the product was extracted with Et2O
(2!10 mL). The extract was washed with H2O (5 mL),
dried (MgSO4) and purified by vacuum distillation.
1
(50.32 MHz, C6D6) 121.3 (q, JCFZ291.7 Hz, CF3), 94.5
2
(sept, JCFZ33 Hz, C(CF3)2), 80.7 (C(CH3)3), 30.0 (3C,
C(CH3)3), 0.8 [Si(CH3)3]; MS: m/z (%)Z297 (4, [MK
CH3]), 291 (16, [MKHF-H]), 243 (4, [MKCF3]), 237 (8,
[MKHSiMe3-H]), 195 (52, [(CF3)2COSiH]), 131 (18,
[(CF3)CZCF2]), 73 (18, [Me3Si]), 57 (100, [C(CH3)3]),
18 (100, [H2O]).
4.3.1. Trimethyl[2,2,2-trifluoro-1-phenyl-1-(trifluoro-
methyl)ethoxy]silane (2a). Yield: 1.30 g (82%) (from
1a); 1.45 g (92%) (from 4a); 1.49 g (94%) (from 5);
colourless liquid; bp 80 8C/10 Torr. (lit.28 bp 29 8C/
0.03 Torr); dH (299.95 MHz, CDCl3): 7.58–7.73 (2H, m);
7.44 (m, 3H), 0.23 (s, 9H, Si(CH3)3); dF (282.20 MHz,
CDCl3) K73.6.
4.3.6. Trimethyl[2,2,2-trifluoro-1-(2-pyridyl)-1-(tri-
fluoromethyl)ethoxy]silane (2g). Yield: 0.82 g (52%);
colourless liquid; bp 34 8C/0.07 Torr; [Found: C, 41.7; H,
4.2; F, 36.1; N, 4.5. C11H13F6NOSi requires C, 41.64; H,
4.13; F, 35.93; N, 4.41%]; dH (299.95 MHz, CDCl3) 8.65
(1H, d, JZ5.0 Hz), 7.80 (1H, td, JZ8.0, 1.9 Hz), 7.69 (1H,
d, JZ8.0 Hz), 7.40 (1H, ddd, JZ8.0, 4.9, 1.0 Hz), 0.24 (9H,
s, Si(CH3)3); dF (282.20 MHz, CDCl3) K75.1; dC
(50.32 MHz, CD2Cl2) 150.3, 148.2, 137.5, 126.4, 123.6
4.3.2. Trimethyl[2,2,2-trifluoro-1-(1-naphtyl)-1-(tri-
fluoromethyl)ethoxy]silane (2b). Yield: 1.61 g (88%);
colourless oil; bp 75 8C/0.02 Torr; [Found: C, 52.7; H,
4.5; F, 31.3. C16H16F6OSi requires C, 52.45; H, 4.40; F,
31.12%]; dH (299.95 MHz, CD2Cl2) 8.68 (1H, d, JZ
8.0 Hz), 7.93 (1H, d, JZ8.4 Hz), 7.77 (1H, d, JZ7.6 Hz),
7.60–7.42 (4H, m, ArH), 0.01 (9H, s, Si(CH3)3); dF
(282.20 MHz, CD2Cl2) K71.2; dC (50.32 MHz, CD2Cl2):
135.1, 133.3, 132.1, 129.6, 127.7, 127.2, 126.8, 126.2, 124.6
1
2
(Ar), 122.8 (q, JCFZ288.6 Hz, CF3) 81.0 (sept, JCF
Z
29.1 Hz, C(CF3)2), 2.3 [Si(CH3)3]; MS: m/z (%) Z317 (5,
[MC]), 302 (100, [MKCH3]), 206 (10, [MKMe3SiF-F]),
178 (15, [MKCF3H-F]), 128 (10), 106 (4, [MKMe3SiCF3-
CF3]), 77 (4, [MKHC(CF3)2OSiMe3]), 18 (10, H2O).
4.3.7. Trimethyl[2,2,2-trifluoro-1-(3-pyridyl)-1-(tri-
fluoromethyl)ethoxy]silane (2h). Yield: 1.14 g (72%);
colourless liquid; bp 80 8C/10 Torr; [Found: C, 41.8; H,
4.2; F, 36.1; N, 4.5. C11H13F6NOSi requires C, 41.64; H,
4.13; F, 35.93; N, 4.41%]; dH (299.95 MHz, CDCl3) 8.89
(1H, br s), 8.69 (1H, dd, JZ4.9, 1.5 Hz), 7.93 (1H dd, JZ
8.3, 0.7 Hz), 7.37 (1H, ddd, JZ8.3, 4.9, 0.7 Hz), 0.26 (9H, s,
Si(CH3)3); dF (282.20 MHz, CDCl3) K75.9.
1
2
(Ar), 123.8 (q, JCFZ291.7 Hz, CF3), 83.6 (sept, JCF
Z
29.8 Hz, C(CF3)2), 0.77 (s, CH3); MS: m/z (%)Z366 (100,
[MC]), 351 (10, [MKCH3]), 331 (6, [MKCH3-HF]), 302
(28, [MK3CH3-F]), 297 (42, [MKCF3]), 293 (28, [MK
SiMe3]), 277 (6, [MKOSiMe3]), 257 (35), 255 (18, [MK
Me3SiF-F]), 235 (30), 225 (18, [MK2CF3H-H]), 207 (15),
177 (14), 155 (86, [MKMe3SiCF3-CF3]), 128 (8, [MK
C(CF3)2OSiMe2–CH2]), 77 (4), 73 (8, [Me3Si]), 18 (38,
H2O).
4.3.8. Trimethyl[2,2,2-trifluoro-1-(4-pyridyl)-1-(tri-
fluoromethyl)ethoxy]silane (2i). Yield: 0.95 g (60%);
colourless liquid; bp 94–95 8C/20 Torr; [Found: C, 41.6;
H, 4.1; F, 35.8; N, 4.3. C11H13F6NOSi requires C, 41.64; H,
4.13; F, 35.93; N, 4.41%]; dH (299.95 MHz, CDCl3) 8.71
(1H, dd, JZ4.7, 1.6 Hz), 7.53 (d, 1H, JZ4.9 Hz), 0.26 (9H,
4.3.3. Trimethyl[2,2,2-trifluoro-1-methyl-1-(trifluoro-
methyl)ethoxy]silane (2c). Yield: 0.79 g (62%); colourless
liquid; bp 98–99 8C. (lit.28 bp 99 8C); dH (299.95 MHz,
CDCl3) 1.57 (3H, m, CH3), 0.20 (s, 9H, Si(CH3)3); dF
(282.20 MHz, CDCl3): K79.8.
s, Si(CH3)3); dF (282.20 MHz, CDCl3) K74.1; dC
Z
1
(50.32 MHz, CD2Cl2): 150.1, 141.5 (Ar), 122.6 (q, JCF
2
288.4 Hz, CF3), 122.2 (Ar), 79.6 (sept, JCFZ30.5 Hz,
C(CF3)2), 1.2 [Si(CH3)3]; MS: m/z (%)Z317 (10, [MC]),
302 (60, [MKCH3]), 256 (9), 206 (100, [MKMe3SiF-F]),
178 (15, [MKCF3H-F]), 147 (18), 128 (16), 106 (3, [MK
Me3SiCF3-CF3]), 77 (13, [MKHC(CF3)2OSiMe3]), 73 (5,
[Me3Si]), 18 (10, H2O).
4.3.4. Trimethyl[2,2,2-trifluoro-1-(2-furyl)-1-(trifluoro-
methyl)ethoxy]silane (2d). Yield: 1.15 g (75%); colourless
liquid; bp 50 8C/12 Torr; [Found: C, 39.4; H, 4.1; F, 37.3.
C10H12F6O2Si requires C, 39.21; H, 3.95; F, 37.22%]; dH
(299.95 MHz, CDCl3) 7.52 (1H, dd, JZ1.8, 0.6 Hz) 6.63
(1H, dd, JZ3.3, 0.6 Hz), 6.46 (1H, dd, JZ3.3, 1.8 Hz), 0.05
(9H, s, Si(CH3)3); dF (282.20 MHz, CDCl3) K76.1; dC
4.3.9.
Trimethyl{[(2E)-3-phenyl-1,1-bis(trifluoro-
1
(50.32 MHz, C6D6) 143.6 (Ar), 122.6 (q, JCFZ291.0 Hz,
methyl)prop-2-enyl]oxy}silane (2j).13 Yield: 1.39 g
(81%); colourless liquid; bp 49–50 8C/0.02 Torr; dH
(299.95 MHz, CDCl3) 7.53–7.29 (m, 5H), 7.00 (d, 1H,
JZ16.2 Hz), 6.21 (d, 1H, JZ16.2 Hz), 0.27 (s, 9H,
Si(CH3)3); dF (282.20 MHz, CDCl3) K76.3.
3
CF3), 112.9 (sept, JCFZ2.1 Hz, CC(CF3)2), 111.2 (Ar),
2
76.5 (sept, JCFZ31.2 Hz, C(CF3)2), 0.21 [Si(CH3)3]; MS:
m/z (%)Z306 (4, [MC]), 291 (42, [MKCH3]), 237 (17,
[MKCF3]), 217 (4, [MKOSiMe3]), 195 (100, [MK

1818
L. A. Babadzhanova et al. / Tetrahedron 61 (2005) 1813–1819
4.3.10. 1,1,1,3,3,3-Hexafluoro-2-phenylpropan-2-ol (3a).
Method A. To a solution of appropriate substrate (1a, 4a, 5,
6) (5 mmol) in DME (8 mL) at K50 8C Me3SiCF3 (1.50 g,
10.5 mmol) and [Me4N]F (0.94 g, 10 mmol) were added.
The mixture was stirred for 1 h at K30 8C and overnight at
room temperature. The precipitate formed was filtered off, a
2 M aqueous solution of HCl (20 mL) was added and the
product was extracted with Et2O (2!10 mL). The extract
was washed with H2O (5 mL), dried (MgSO4) and purified
by vacuum distillation.
References and notes
1. Knunyants, I. L.; Chen, T.-Y.; Gambaryan, N. P. Isvest. Akad.
Nauk S.S.S.R., Otdel. Khim. Nauk 1960, 686–692. Chem.
Abstr. 1960, 54, 22484h.
2. (a) O’Rear, J. G.; Griffith, J. R. Am. Chem. Soc., Div. Org.
Coat. Plast. Chem., Pap. 1973, 33, 657–662. Chem. Abstr.
1975, 82, 58626t.O’Rear, J. G.; Griffith, J. R. U.S. Patent
3,879,430, 1975; Chem. Abstr. 1975, 83, 58638
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1981, 46, 1049–1053.
Method B. To a solution of trimethyl[2,2,2-trifluoro-1-
phenyl-1-(trifluoromethyl)ethoxy]silane 2a (0.95 g,
3 mmol) in THF (5 mL), 6 M HCl (5 mL) was added. The
mixture was stirred overnight at room temperature. H2O
(25 mL) was added and the product was extracted with Et2O
(2!10 mL). The combined organic phases were washed
with H2O (5 mL), dried (MgSO4) and purified by vacuum
distillation.
4. Nguyen, T. T.; Amey, R. L.; Martin, J. C. J. Org. Chem. 1982,
47, 1024–1027.
5. (a) Zelenin, A. E.; Chkanikov, N. D.; Ivanchenko, Yu. N.;
Tkachev, V. D.; Rusakova, V. A.; Kolomiets, A. F.; Fokin,
A. V. Khim. Geterotsikl. Soedin. 1987, 9, 1200–1201. Chem.
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Yield: [Method A] 0.84 g (81%) (from 1a); 0.84 g (81%)
(from 4a); 0.91 g (87%) (from 5); 0.8 g (77%) (from 6);
[Method B] 0.81 g (81%) (from 2a); colourless liquid; bp
53 8C/12 Torr. (lit.29 bp 50 8C/10 Torr); dH (299.95 MHz,
CDCl3) 7.79 (2H, m) 7.29–7.00 (3H, m, overlapping), 4.58
(s, OH); dF (282.20 MHz, CDCl3) K75.3.
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Miyashiro, J. M.; Van Camp, J. A.; Collins, J. T. U.S. Patent
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2003; Chem. Abstr. 2004, 140, 16556f.
4.3.11. 1,1,1,3,3,3-Hexafluoro-2-(trifluoromethyl)pro-
pan-2-ol (3f). To a solution of trifluoroacetic acid anhydride
(3.50 g, 16.7 mmol) in DME (15 mL) at K50 8C Me3SiCF3
(5.00 g, 35.0 mmol) and [Me4N]F (3.10 g, 33.4 mmol) were
added. The mixture was stirred for 1 h at K30 8C and
overnight at rt. The solvent and other volatile materials were
condened under high vacuum over a period of 1 h leaving a
white powder. Concentrated H2SO4 (5 mL) was injected
into the reaction vessel cooled with an ice bath, and after
0.5 h the resulting volatile products were collected in a trap
(K196 8C) by pumping from the reactor at 20 8C for 2 h.
Fractional distillation using a 10 cm Vigreux distilling
column afforded 3.35 g (87%) of 3f. Bp 45 8C (lit.30 bp
48 8C); dF (282.20 MHz, Et2O) K74.7.
7. Knunyants, I. L.; Gambaryan, N. P.; Ch’en, C.-Y.; Roklin,
E. M. Isv. Akad. Nauk SSSR, Otd. Khim. Nauk 1962, 684–692.
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4.3.12. 1,1,1,3,3,3-Hexafluoro-2-[4-(2,2,2-trifluoro-1-
hydroxy-1-(trifluoromethyl)ethyl)-phenyl]-propan-2-ol
(8). To a solution of terephthaloyl chloride (1.00 g,
5.0 mmol) in DME (12 mL) at K50 8C Me3SiCF3 (3 g,
21 mmol) and [Me4N]F (1.88 g, 20 mmol) were added. The
mixture was stirred for 1 h at K30 8C and overnight at rt. A
2 M aq solution of HCl (25 mL) was added and the product
was extracted with Et2O (2!15 mL). The extract was
washed with H2O (10 mL), dried (MgSO4), the solvent
evaporated and the residue purified by crystallisation from
Et2O. Yield: 1.68 g (82%); colourless solid; mp 85–86 8C
(lit.31 mp 86 8C; lit.8a mp 85 8C); dH (299.95 MHz, CDCl3)
7.80 (4H, s), 3.99 (2H, s, OH); dF (282.20 MHz, CDCl3)
K76.1.
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The generous financial support of this work by the DFG
(grant 436 UKR 113) is gratefully acknowledged.

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1819
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