Terminally perfluorinated long-chain alkanethiols

Article abstract of DOI:10.1016/S0022-1139(98)00284-X

This paper describes the synthesis of a series of alkanethiols containing perfluorinated terminal segments: F(CF₂)_m(CH₂)_nSH, where m = 1, n = 9-15; m = 2, n = 11-14; m = 3, n = 10-13; and m = 4, n = 9-12. Fluorinated alkyl iodides of the general formula F(CF₂)_m(CH₂)_nI, where m = 1-4 and n = 0 or 1, were added to long-chain ω-olefins that were functionalized at the α-terminus with a thioacetate group. The reactions proceeded in good yields under free radical conditions. Reduction of the resulting secondary iodides gave long-chain alkanethioacetates with perfluoroalkyl terminal segments. These intermediates were readily transformed into the corresponding terminally perfluorinated alkanethiols by acidic deprotection. The product thiols should find use in the generation of well-defined fluorinated interfaces using the self-assembled monolayer (SAM) technique.

Full text of DOI:10.1016/S0022-1139(98)00284-X

Journal of Fluorine Chemistry 93 (1999) 107±115
Terminally per¯uorinated long-chain alkanethiols
Michael Graupe, Thomas Koini, Vincent Y. Wang, George M. Nassif, Ramon Colorado Jr,
Ramon J. Villazana, Henry Dong, Yasuhiro F. Miura, Olga E. Shmakova, T. Randall Lee*
Department of Chemistry, University of Houston, Houston, TX 77204-5641, USA
Received 2 June 1998; accepted 8 September 1998
Abstract
This paper describes the synthesis of a series of alkanethiols containing per¯uorinated terminal segments: F(CF2)m(CH2)nSH, where
m ˆ 1, n ˆ 9±15; m ˆ 2, n ˆ 11±14; m ˆ 3, n ˆ 10±13; and m ˆ 4, n ˆ 9±12. Fluorinated alkyl iodides of the general formula
F(CF2)m(CH2)nI, where m ˆ 1±4 and n ˆ 0 or 1, were added to long-chain w-ole®ns that were functionalized at the a-terminus with a
thioacetate group. The reactions proceeded in good yields under free radical conditions. Reduction of the resulting secondary iodides gave
long-chain alkanethioacetates with per¯uoroalkyl terminal segments. These intermediates were readily transformed into the corresponding
terminally per¯uorinated alkanethiols by acidic deprotection. The product thiols should ®nd use in the generation of well-de®ned
¯uorinated interfaces using the self-assembled monolayer (SAM) technique. # 1999 Elsevier Science S.A. All rights reserved.
1. Introduction
a per¯uoroalkyl radical, which attacks the terminal carbon
of the ole®nic group [5]. Reduction of the resultant ¯uori-
nated secondary iodide with zinc or lithium aluminum
hydride provided a variety of per¯uoroalkylated compounds
in excellent yields.
Cloux and Kovats modi®ed Brace's approach by explor-
ing the addition of 2,2,2-tri¯uoroethyl iodide to terminal
alkenes [25]. This approach is preferred for the synthesis of
per¯uoromethyl-terminated species because liquid 2,2,2-
tri¯uoroethyl iodide is much easier to handle than gaseous
tri¯uoromethyl iodide. Although formation of the 2,2,2-
tri¯uoroethyl radical is slower than that of the corresponding
per¯uorinated moieties, the coupling was observed to occur
upon the addition of successive portions of radical initiator.
Furthermore, the yields obtained by Cloux and Kovats were
satisfactory, but generally lower than those obtained by
Brace.
We have targeted the synthesis of terminally per¯uori-
nated alkanethiols for the generation of well de®ned ¯uori-
nated interfaces via self assembly on gold [26±31]. To this
end, we have developed a synthetic strategy that relies
heavily on the methods established by Brace and Cloux
and Kovats, but with a new twist: the radical addition of
¯uorinated alkyl iodides to w-ole®ns that are functionalized
at the a-terminus with a thioacetate group. Herein, we
describe this new approach and illustrate its ef®cacy by
synthesizing a wide range of terminally per¯uorinated alka-
nethiols that possess varying chain lengths and degrees of
¯uorination.
The synthesis of speci®cally ¯uorinated long-chain
a,w-functionalized hydrocarbons remains a challenging
problem for interfacial scientists. The generation of
organized thin ®lms from these molecules offers the oppor-
tunity to study fundamental properties of ¯uorinated inter-
faces, such as wetting, adhesion, and friction. The ability to
control the identities of the a and w functionalities using
organic synthesis permits atomic-level control over the
structure and composition of interfaces formed from these
molecules by either Langmuir±Blodgett or self-assembly
techniques [1,2]. Organic synthesis thus provides a conve-
nient tool for ®ne-tuning the interfacial properties of thin
®lms.
A variety of methods have been used to introduce per-
¯uorinated segments of different lengths into aliphatic
organic molecules [3±21]. Brace investigated the radical
addition of iodoper¯uoroalkanes to a variety of terminal
vinylic alkenes [3,4]. His approach was based on initial
studies by Haszeldine [22], Park et al. [23], and Moore [24],
who used ultraviolet light for initiation. These reactions
typically required several days for completion. By employ-
ing azo or peroxy radical initiators, however, Brace was able
to achieve high yields of coupling within hours. Brace
proposed that the coupling proceeds via the formation of
*Corresponding author.
0022-1139/99/$ ± see front matter # 1999 Elsevier Science S.A. All rights reserved.
P I I : S 0 0 2 2 - 1 1 3 9 ( 9 8 ) 0 0 2 8 4 - X

108
M. Graupe et al. / Journal of Fluorine Chemistry 93 (1999) 107±115
2. Experimental
(t, J ˆ 7.4 Hz, 2H), 2.33 (s, 3H), 2.03 (m, 2H), 1.55 (m, 2H),
1.38±1.25 (m, 14H).
2.1. General information
12-Tridecenyl-1-thioacetate. 1H NMR (300 MHz,
CDCl3): ꢀ ˆ 5.88±5.72 (m, 1H), 5.01±4.90 (m, 2H), 2.86
(t, J ˆ 7.4 Hz, 2H), 2.32 (s, 3H), 2.03 (m, 2H), 1.56 (m, 2H),
1.38±1.23 (m, 16H).
Partially ¯uorinated and per¯uorinated alkyl iodides were
purchased from Aldrich Chemical Co. and used as received.
Long-chain hydrocarbon starting materials, also purchased
from Aldrich, were either used as received or modi®ed
before use via known literature procedures. Organic sol-
vents were dried by passage through activated alumina and
degassed by the freeze-pump-thaw method immediately
before use. Reactions were monitored by thin-layer chro-
matography (TLC) using Whatman F254 precoated silica gel
plates (0.25 mm thickness). Silica gel (EM Sciences; 63±
200 mm or 35±70 mm) and reagent grade solvents were used
for column chromatography. Nuclear magnetic resonance
spectra (NMR) were recorded on a General Electric QE-300
spectrometer (1H: 300 MHz; 13C: 75.5 MHz). Elemental
analyses were performed by National Chemical Consulting.
High resolution mass spectra were obtained at Rice Uni-
versity on a Finniganmat MAT 95 mass spectrometer oper-
ating in the EI mode.
2.3. Terminally perfluorinated alkyl thioacetates 3
(general procedure)
The w-alkenyl thioacetate (65.0 mmol) and ¯uorinated
iodide RFI (71.5 mmol) were placed in a 50 ml Schlenk
¯ask, and the radical initiator AIBN (2 mol%) was added
under a ¯ow of argon. The ¯ask was closed, evacuated until
the reaction mixture started to effervesce, and re®lled with
argon; this process was repeated at least two additional
times. The ¯ask was sealed under vacuum, and the stirred
reaction mixture was heated to 908C. After 3 h, the ¯ask was
cooled to room temperature, and another portion of AIBN
(2 mol%) was added under a ¯ow of argon as described
above. The stirred solution was again heated to 908C, and
the entire process was repeated at least two additional times;
3 h passed between the additions of AIBN. The progress of
1
2.2. w-Alkenyl-1-thioacetates 1 (general procedure)
the reaction was monitored by H NMR spectroscopy of
small aliquots collected between the additions. The ¯ask
was cooled to room temperature, and the crude iodothioa-
cetate 2 was used in the next step without further puri®ca-
tion.
Potassium thioacetate (86.0 mmol) was dissolved in
100 ml of absolute ethanol (previously degassed) under
argon. To the stirred solution, the w-alkenyl bromide
(43.0 mmol) was added dropwise over 10 min. Stirring
was continued, and the mixture was heated to re¯ux for
6 h under argon. After cooling, 150 ml of water was added,
and the mixture was extracted with hexane (3 Â 100 ml).
The combined organic layers were washed with brine
(1 Â 100 ml) and dried over MgSO4. The solvent was
removed by rotary evaporation. The crude product was
puri®ed by column chromatography on silica gel (hex-
ane / diethyl ether ˆ 9 / 1) affording the w-alkenyl-1 thioa-
cetate in ca. 95% yield.
2.4. Reduction method A1
NaBH4 (200 mmol) was dissolved in 200 ml of dimethyl
formamide (DMF, previously degassed) and cooled to 08C.
The crude iodothioacetate 2, dissolved in 50 ml of DMF,
was added slowly to the stirred solution. After stirring for
15 min, the solution was allowed to warm to room tem-
perature. After stirring for 3 h, 100 ml of ice-water was
added, and the mixture was stirred until effervescence
ceased. The solution was carefully neutralized with conc.
HCl and extracted with hexane (3 Â 100 ml). The combined
organic phases were washed with water (2 Â 100 ml), dried
over MgSO4, and evaporated to dryness. The residue was
dissolved in 50 ml of CH2Cl2 and cooled to ca. 108C (ice /
salt bath). Ozone was bubbled through the solution for 10±
20 min; the duration varied directly with the amount of
ole®nic starting material remaining in the crude reaction
mixture. After bubbling argon through the solution for
10 min, the solvent was evaporated at room temperature
under vacuum. A portion of DMF (100 ml) was added to the
¯ask, and a solution of NaBH4 (2 molar excess) in 50 ml of
DMF was added dropwise to the stirred solution at 08C. The
mixture was allowed to warm to room temperature and
stirred for 3 h under argon. Ice-water (100 ml) was added.
The mixture was neutralized with conc. HCl and extracted
with hexane (3 Â 100 ml). The combined organic layers
were washed with water (1 Â 100 ml) and dried over
7-Octenyl-1-thioacetate. 1H NMR (300 MHz, CDCl3):
ꢀ ˆ 5.90±5.73 (m, 1H), 5.03±4.91 (m, 2H), 2.86 (t,
J ˆ 7.4 Hz, 2H), 2.33 (s, 3H), 2.02 (m, 2H), 1.55 (m,
2H), 1.40±1.29 (m, 6H).
1
8-Nonenyl-1-thioacetate. H NMR (300 MHz, CDCl3):
ꢀˆ5.89±5.71 (m, 1H), 5.01±4.89 (m, 2H), 2.87 (t,
J ˆ 7.4 Hz, 2H), 2.33 (s, 3H), 2.03 (m, 2H), 1.52 (m,
2H), 1.39±1.27 (m, 8H).
1
9-Decenyl-1-thioacetate. H NMR (300 MHz, CDCl3):
ꢀ ˆ 5.88±5.71 (m, 1H), 5.01±4.90 (m, 2H), 2.85 (t,
J ˆ 7.4 Hz, 2H), 2.32 (s, 3H), 2.03 (m, 2H), 1.53 (m,
2H), 1.39±1.28 (m, 10H).
10-Undecenyl-1-thioacetate. 1H NMR (300 MHz,
CDCl3): ꢀ ˆ 5.88±5.71 (m, 1H), 5.02±4.89 (m, 2H), 2.85
(t, J ˆ 7.4 Hz, 2H), 2.35 (s, 3H), 2.05 (m, 2H), 1.56 (m, 2H),
1.39±1.28 (m, 12H).
11-Dodecenyl-1-thioacetate. 1H NMR (300 MHz,
CDCl3): ꢀ ˆ 5.88±5.71 (m, 1H), 5.03±4.89 (m, 2H), 2.86

M. Graupe et al. / Journal of Fluorine Chemistry 93 (1999) 107±115
109
MgSO4. The solvent was removed by rotary evaporation.
The crude product was puri®ed by column chromatography
on silica gel (hexane / diethyl ether ˆ 50 / 1). Typical over-
all yields for the radical addition, dehalogenation, and
puri®cation were 20±30%.
J ˆ 7.3 Hz, 2H), 2.31 (s, 3H), 2.15±1.91 (m, 2H), 1.63±
1.50 (m, 4H), 1.41±1.22 (m, 10H).
14,14,14-Tri¯uorotetradecyl thioacetate. 1H NMR
(300 MHz, CDCl3): ꢀ ˆ 2.85 (t, J ˆ 7.4 Hz, 2H), 2.31 (s,
3H), 2.13±1.96 (m, 2H), 1.60±1.48 (m, 4H), 1.38±1.23 (m,
18H).
2.5. Reduction method A2
13,13,14,14,14-Penta¯uorotetradecyl thioacetate. 1H
NMR (300 MHz, CDCl3): ꢀ ˆ 2.86 (t, J ˆ 7.4 Hz, 2H),
2.35 (s, 3H) 2.11±1.91 (m, 2H), 1.59±1.49 (m, 4H),
1.39±1.25 (m, 16H).
12,12,13,13,14,14,14-Hepta¯uorotetradecyl thioacetate.
1H NMR (300 MHz, CDCl3): ꢀ ˆ 2.85 (t, J ˆ 7.4 Hz, 2H),
2.35 (s, 3H), 2.13±1.93 (m, 2H), 1.59±1.49 (m, 4H), 1.39±
1.26 (m, 14H).
15,15,15-Tri¯uoropentadecyl thioacetate. 1H NMR
(300 MHz, CDCl3): ꢀ ˆ 2.81 (t, J ˆ 7.2 Hz, 2H), 2.27 (s,
3H), 2.09±1.94 (m, 2H), 1.56±1.49 (m, 4H), 1.33±1.20 (m,
20H).
14,14,15,15,16,16,16-Hepta¯uorohexadecyl thioacetate.
1H NMR (300 MHz, CDCl3): ꢀ ˆ 2.83 (t, J ˆ 7.2 Hz, 2H),
2.29 (s, 3H), 2.09±1.91 (m, 2H), 1.61±1.48 (m, 4H), 1.38±
1.22 (m, 18H).
The crude iodothioacetate 2 was dissolved in 130 ml of
glacial acetic acid (HOAc). Zinc dust (195 mmol) was
added at room temperature under argon. Compounds that
were insoluble in glacial acetic acid were dissolved in a
minimum amount of dry THF and then added to the
Zn / HOAc slurry. The mixture was stirred for 16 h and
then ®ltered through Celite. The ®ltrate was evaporated
to dryness and redissolved in hexane (ca. 100 ml). The
solution was washed with water (2 Â 100 ml), saturated
aqueous NaHCO3 solution (1 Â 100 ml), and brine
(1 Â 100 ml), and then dried over MgSO4. Removal of
the solvent afforded the crude thioacetate 3, which was
often contaminated with a small amount of ole®nic starting
material 1. Crude thioacetate 3 was dissolved in 50 ml of
toluene, and N-methyl-a-phenyl nitrone (30.0 mmol) was
added. After re¯uxing for 48 h, the reaction mixture was
diluted with diethyl ether (100 ml) and washed with water
(3 Â 100 ml). The organic phase was dried with MgSO4,
and evaporated to dryness by rotary evaporation. The resi-
due was puri®ed by chromatography on silica gel (hexane /
diethyl ether ˆ 50 / 1). Typical overall yields for the radical
addition, dehalogenation, and puri®cation ranged from
56±66%.
15,15,16,16,16-Penta¯uorohexadecyl thioacetate. 1H
NMR (300 MHz, CDCl3): ꢀ ˆ 2.83 (t, J ˆ 7.2 Hz, 2H),
2.29 (s, 3H), 2.06±1.88 (m, 2H), 1.60±1.48 (m, 4H),
1.37±1.22 (m, 20H).
13,13,14,14,15,15,15-Hepta¯uoropentadecyl
thioace-
tate. 1H NMR (300 MHz, CDCl3): ꢀ ˆ 2.84 (t,
J ˆ 7.3 Hz, 2H), 2.30 (s, 3H), 2.13±1.90 (m, 2H), 1.66±
1.50 (m, 4H), 1.42±1.19 (m, 16H).
10,10,10-Tri¯uorodecyl thioacetate. 1H NMR (300 MHz,
CDCl3): ꢀ ˆ 2.85 (t, J ˆ 7.4 Hz, 2H), 2.34 (s, 3H), 2.17±
1.99 (m, 2H), 1.58±1.47 (m, 4H), 1.39±1.27 (m, 10H).
11,11,11-Tri¯uoroundecyl thioacetate. 1H NMR
(300 MHz, CDCl3): ꢀ ˆ 2.86 (t, J ˆ 7.4 Hz, 2H), 2.33 (s,
3 H), 2.17±1.99 (m, 2H), 1.60±1.50 (m, 4H), 1.39±1.25 (m,
12H).
12,12,12-Tri¯uorododecyl thioacetate. 1H NMR
(300 MHz, CDCl3): ꢀ ˆ 2.85 (t, J ˆ 7.4 Hz, 2H), 2.34 (s,
3H), 2.18±1.99 (m, 2H), 1.61±1.50 (m, 4H), 1.39±1.28 (m,
14H).
13,13,13-Tri¯uorotridecyl thioacetate. 1H NMR
(300 MHz, CDCl3): ꢀ ˆ 2.85 (t, J ˆ 7.4 Hz, 2H), 2.35 (s,
3H), 2.16±1.98 (m, 2H), 1.59±1.49 (m, 4H), 1.39±1.26 (m,
16H).
12,12,13,13,13-Penta¯uorotridecyl thioacetate. 1H NMR
(300 MHz, CDCl3): ꢀ ˆ 2.85 (t, J ˆ 7.4 Hz, 2H), 2.35 (s,
3H), 2.12±1.91 (m, 2H), 1.59±1.50 (m, 4H), 1.39±1.26 (m,
14H).
2.6. Terminally perfluorinated alkanethiols 4 (general
procedure)
The terminally per¯uorinated alkyl thioacetates 3 or 9
(15.0 mmol) was dissolved in 100 ml of absolute ethanol
(previously degassed) under argon. To the solution, 40 ml
conc. HCl were added, and the stirred mixture was heated
under re¯ux at 908C for 13 h. The reaction mixture was
diluted with 30 ml of water and extracted with hexane
(3 Â 100 ml). The combined organic layers were washed
with water (2 Â 100 ml), dried over MgSO4, and evaporated
to dryness by rotary evaporation. The crude product was
puri®ed by chromatography on silica gel (hexane) to give
the terminally per¯uorinated alkanethiol in ca. 95% yield.
10,10,10-Tri¯uorodecanethiol. 1H NMR (300 MHz,
CDCl3): ꢀ ˆ 2.52 (q, J ˆ 7.2 Hz, 2H), 2.13±1.96 (m, 2H),
1.67±1.47 (m, 4H), 1.36±1.25 (m, 11H). 13C NMR
1
(75.5 MHz, CDCl3): ꢀ ˆ 127.25 (q, JCF ˆ 276 Hz),
2
34.03, 33.50 (q, JCF ˆ 28 Hz), 29.11 (3C), 28.95, 28.25,
11,11,12,12,13,13,13-Hepta¯uorotridecyl thioacetate.
1H NMR (300 MHz, CDCl3): ꢀ ˆ 2.84 (t, J ˆ 7.4 Hz,
2H), 2.30 (s, 3H), 2.10±1.92 (m, 2H), 1.59±1.49 (m, 4H),
1.40±1.24 (m, 12H).
10,10,11,11,12,12,13,13,13-Nona¯uorotridecyl thioace-
tate. 1H NMR (300 MHz, CDCl3): ꢀ ˆ 2.85 (t,
24.61, 21.81. Anal. Calc. for C10H19F3S: C, 52.61; H, 8.39.
Found: C, 52.80; H, 7.98.
11,11,11-Tri¯uoroundecanethiol. 1H NMR (300 MHz,
CDCl3): ꢀ ˆ 2.52 (q, J ˆ 7.2 Hz, 2H), 2.13±1.95 (m, 2H),
1.67±1.48 (m, 4H), 1.36±1.25 (m, 13H). 13C NMR
1
(75.5 MHz, CDCl3): ꢀ ˆ 127.18 (q, JCF ˆ 276 Hz),

110
M. Graupe et al. / Journal of Fluorine Chemistry 93 (1999) 107±115
2
34.02, 33.50 (q, JCF ˆ 28 Hz), 29.36 (2C), 29.25, 29.13,
28.63, 28.30, 24.48, 21.78. Anal. Calc. for C11H21F3S: C,
54.52 H; 8.73. Found: C, 54.73; H, 8.35.
28.91, 28.20, 24.29, 20.03. Anal. Calc. for C14H25F5S: C,
52.48; H, 7.86. Found: C, 52.40; H, 7.77.
12,12,13,13,14,14,14-Hepta¯uorotetradecanethiol. 1H
NMR (300 MHz, CDCl3): ꢀ ˆ 2.52 (q, J ˆ 7.2 Hz, 2H),
2.17±1.94 (m, 2H), 1.66±1.44 (m, 4H), 1.37±1.21 (m, 15H).
13C NMR (75.5 MHz, CDCl3): ꢀ ˆ 117.86 (qt,
12,12,12-Tri¯uorododecanethiol. 1H NMR (300 MHz,
CDCl3): ꢀ ˆ 2.52 (q, J ˆ 7.2 Hz, 2H), 2.13±1.96 (m, 2H),
1.67±1.47 (m, 4H), 1.36±1.25 (m, 15H). 13C NMR
1
2
1
(75.5 MHz, CDCl3): ꢀ ˆ 127.25 (q, JCF ˆ 277 Hz),
1JCF ˆ 287 Hz, JCF ˆ 37 Hz), 117.67 (tt, JCF ˆ 252 Hz,
2
1
2
33.98±33.60 (q, JCF ˆ 28 Hz), 29.39 (2C), 29.26, 29.10,
2JCF ˆ 31 Hz), 108.85 (ttq, JCF ˆ 263 Hz, JCF ˆ 37 Hz),
2
28.98, 28.60, 28.28, 24.48, 21.75. Anal. Calc. for
C12H23F3S: C, 56.22; H, 9.04. Found: C, 56.37; H, 9.01.
13,13,13-Tri¯uorotridecanethiol. 1H NMR (300 MHz,
CDCl3): ꢀ ˆ 2.52 (q, J ˆ 7.2 Hz, 2 H), 2.11±1.96 (m,
2H), 1.62±1.47 (m, 4H), 1.35±1.23 (m, 17H), 13C NMR
(75.5 MHz, CDCl3): ꢀ ˆ 127.11 (q, 1JCF ˆ 276 Hz), 34.00,
34.01, 30.47 (t, JCF ˆ 22 Hz), 29.39 (3C), 29.28, 29.13,
28.99, 28.28, 24.42, 19.93. Anal. Calc. for C14H23F7S: C,
47.18; H, 6.50. Found: 47.36; H, 6.39.
11,11,12,12,13,13,14,14,14-Nona¯uorotetradecanethiol.
1H NMR (300 MHz, CDCl3): ꢀ ˆ 2.50 (q, J ˆ 7.2 Hz, 2H),
2.14±1.91 (m, 2H), 1.66±1.50 (m, 4H), 1.43±1.21 (m, 13H).
13C NMR (75.5 MHz, CDCl3): ꢀ ˆ 118.32 (tt,
2
33.55 (q, JCF ˆ 28 Hz), 29.42 (3C), 29.26, 29.07, 28.98,
2
1
28.58, 28.25, 24.31, 21.71. Anal. Calc. for C13H25F3S: C,
57.75; H, 9.32. Found: C, 57.45; H, 9.34.
1JCF ˆ 254 Hz, JCF ˆ 32 Hz), 117.46 (qt, JCF ˆ 288 Hz,
2JCF ˆ 34 Hz), 113.61±100.67 (ttq; ttt, 2C), 34.05, 30.78 (t,
2JCF ˆ 23 Hz), 29.41, 29.30, 29.20, 29.09, 29.04, 28.36,
24.62, 20.07. HRMS Calc. for C14H21F9S: 392.1220.
Found; 392.1219(4).
12,12,13,13,13-Penta¯uorotridecanethiol. 1H NMR
(300 MHz, CDCl3): ꢀ ˆ 2.52 (q, J ˆ 7.2 Hz, 2H), 2.08±
1.92 (m, 2H), 1.63±1.41 (m, 4H), 1.35±1.23 (m, 15H). 13C
1
NMR (75.5 MHz, CDCl3): ꢀ ˆ 119.02 (tq, JCF ˆ 249 Hz,
15,15,15-Tri¯uoropentadecanethiol.
1H
NMR
2JCF ˆ 37 Hz), 115.79 (qt, JCF ˆ 249 Hz, JCF ˆ 37 Hz),
(300 MHz, CDCl3): ꢀ ˆ 2.50 (q, J ˆ 7.2 Hz, 2H), 2.12±
1
2
2
34.09, 30.62 (t, JCF ˆ 22 Hz), 29.46 (3C), 29.34, 29.18,
1.96 (m, 2H), 1.64±1.48 (m, 4H), 1.38±1.22 (m, 21H). 13C
1
29.07, 28.35, 24.47, 20.19. Anal. Calc. for C13H23F5S: C,
50.96; H, 7.57. Found: C, 51.15; H, 7.62.
NMR (75.5 MHz, CDCl3): ꢀ ˆ 127.27 (q, JCF ˆ 276 Hz),
2
34.05, 33.71 (q, JCF ˆ 28 Hz), 29.58 (4C), 29.53, 29.35,
11,11,12,12,13,13,13-Hepta¯uorotridecanethiol.
1H
29.17, 29.07, 28.69, 28.37, 24.63, 21.82. Anal. Calc. for
C15H29F3S: C, 60.37; H, 9.79. Found: C, 59.90; H, 9.89.
14,14,15,15,15-Penta¯uoropentadecanethiol. 1H NMR
(300 MHz, CDCl3): ꢀ ˆ 2.51 (q, J ˆ 7.2 Hz, 2H), 2.08±
NMR (300 MHz, CDCl3): ꢀ ˆ 2.51 (q, J ˆ 7.2 Hz, 2H),
2.11±1.93 (m, 2H), 1.66±1.53 (m, 4H), 1.40±1.22 (m, 13H).
13C NMR (75.5 MHz, CDCl3): ꢀ ˆ 117.87 (qt,
1JCF ˆ 287 Hz, JCF ˆ 34 Hz), 117.72 (tt, JCF ˆ 252 Hz,
1.90 (m, 2H), 1.65±1.52 (m, 4H), 1.35±1.23 (m, 19H). 13
C
2
1
2JCF ˆ 31 Hz), 108.86 (ttq, JCF ˆ 267 Hz, JCF ˆ 37 Hz),
NMR (75.5 MHz, CDCl3): ꢀ ˆ 119.20 (tq, JCF ˆ 285 Hz,
1
2
1
2
1
2
33.97, 30.54 (t, JCF ˆ 22 Hz), 29.34 (2C), 29.24, 29.13,
2JCF ˆ 37 Hz), 115.53 (qt, JCF ˆ 252 Hz, JCF ˆ 37 Hz),
2
29.02, 28.29, 24.57, 19.98. Anal. Calc. for C13H21F7S: C,
45.61; H, 6.18. Found: C, 45.73; H, 6.10.
34.01, 30.60 (t, JCF ˆ 22 Hz), 29.48 (5 C), 29.31, 29.14,
29.03, 28.33, 24.59, 20.16. A satisfactory analysis was not
obtained. HRMS Calc for C15H27F5S; 334.1754. Found:
334.1750(3).
10,10,11,11,12,12,13,13,13-Nona¯uorotridecanethiol.
1H NMR (300 MHz, CDCl3): ꢀ ˆ 2.50 (q, J ˆ 7.2 Hz, 2H),
2.13±1.92 (m, 2 H), 1.65±1.52 (m, 4H), 1.42±1.19 (m, 11H).
13C NMR (75.5 MHz, CDCl3): ꢀ ˆ 118.30 (tt,
13,13,14,14,15,15,15-Hepta¯uoropentadecanethiol. 1H
NMR (300 MHz, CDCl3): ꢀ ˆ 2.51 (q, J ˆ 7.2 Hz, 2H),
2.13±1.92 (m, 2H), 1.69±1.53 (m, 4H), 1.45±1.20 (m, 17H).
13C NMR (75.5 MHz, CDCl3): ꢀ ˆ 117.91 (qt,
1JCF ˆ 255 Hz, JCF ˆ 32 Hz), 117.42 (qt, JCF ˆ 286 Hz,
2JCF ˆ 34 Hz), 113.65±100.74 (ttq; ttt, 2C), 33.98, 30.76 (t,
2JCF ˆ 22 Hz), 29.22, 29.13, 29.05, 28.94, 28.29, 24.60,
20.04. Anal. Calc. for C13H19F9S: C, 41.27; H, 5.06. Found:
C, 41.38; H, 4.96.
2
1
2
1
1JCF ˆ 288 Hz, JCF ˆ 33 Hz), 117.77 (tt, JCF ˆ 252 Hz,
2JCF ˆ 29 Hz), 108.67 (ttq, JCF ˆ 264 Hz, JCF ˆ 37 Hz),
1
2
2
34.05, 30.59 (t, JCF ˆ 22 Hz), 29.49 (4C), 29.35, 29.19,
14,14,14-Tri¯uorotetradecanethiol. 1H NMR (300 MHz,
CDCl3): ꢀ ˆ 2.48 (q, J ˆ 7.2 Hz, 2H), 2.11±1.95 (m, 2H),
1.62±1.46 (m, 4H), 1.34±1.23 (m, 19H). 13C NMR
29.07, 28.34, 24.62, 20.03. Anal. Calc. for C15H25F7S: C,
48.64; H, 6.80. Found: C, 48.94; H, 6.67.
12,12,13,13,14,14,15,15,15-Nona¯uoropentadecanethiol.
1H NMR (300 MHz, CDCl3): ꢀ ˆ 2.50 (q, J ˆ 7.2 Hz, 2H),
1
(75.5 MHz, CDCl3): ꢀ ˆ 127.15 (q, JCF ˆ 276 Hz),
2
34.03, 33.46 (q, JCF ˆ 29 Hz), 29.50 (4C), 29.31, 29.13,
2.16±1.93 (m, 2H), 1.66±1.50 (m, 4H), 1.42±1.20 (m, 15 H).
1
29.03, 28.65, 28.32, 24.49, 21.77. Anal. Calc. for
C14H27F3S: C, 59.12; H, 9.57. Found: C, 59.50; H, 9.90.
13,13,14,14,14-Penta¯uorotetradecanethiol. 1H NMR
(300 MHz, CDCl3): ꢀ ˆ 2.52 (q, J ˆ 7.2 Hz, 2H), 2.08±
1.92 (m, 2H), 1.63±1.41 (m, 4H), 1.35±1.23 (m, 17H). 13C
13C NMR (75.5 MHz, CDCl3): ꢀ ˆ 118.33 (tt, JCF
ˆ
2
1
253 Hz, JCF ˆ 30 Hz), 117.41 (qt, JCF ˆ 293 Hz,
2JCF ˆ 32 Hz), 113.06±100.77) (ttq; ttt, 2C), 34.02, 30.77
2
(t, JCF ˆ 22 Hz), 29.45 (3C), 29.34, 29.20, 29.06, 28.36,
24.63, 20.05. Anal. Calc. for C15H23F9S: C, 44.33; H, 5.70.
Found: C, 43.93; H, 5.85.
1
NMR (75.5 MHz, CDCl3): ꢀ ˆ 119.09 (tq, JCF ˆ 285 Hz,
2JCF ˆ 37 Hz), 115.62 (qt, JCF ˆ 252 Hz, JCF ˆ 37 Hz),
16,16,16-Tri¯uorohexadecanethiol. 1H NMR (300 MHz,
1
2
2
33.95, 30.41 (t, JCF ˆ 22 Hz), 29.37 (4C), 29.22, 29.04,
CDCl3): ꢀ ˆ 2.50 (q, J ˆ 7.2 Hz, 2H), 2.11±1.95 (m, 2H),

M. Graupe et al. / Journal of Fluorine Chemistry 93 (1999) 107±115
111
1.63±1.47 (m, 4H), 1.36±1.22 (m, 23H). 13C NMR
(ice / salt bath). Ozone was bubbled through the solution for
20 min. After bubbling argon through the solution for
10 min, the solvent was evaporated at room temperature
under vacuum. The residues were dissolved in 50 ml of THF
and added over 5 min to a slurry of LiAlH4 in THF at 08C
under argon. The mixture was re¯uxed under argon for 2 h.
After cooling to 08C, water was added dropwise until the
evolution of hydrogen ceased. The mixture was acidi®ed
with 2N HCl and extracted with diethyl ether (3 Â 100 ml).
The solution was washed with water (2 Â 100 ml), saturated
aqueous NaHCO3 solution (1 Â 100 ml), and brine
(1 Â 100 ml), and then dried over MgSO4. Removal of
the solvent by rotary evaporation afforded the crude alcohol
6, which was puri®ed by chromatography on silica gel
(hexane / diethyl ether ˆ 2 / 1. Typical overall yields for
the radical addition, dehalogenation, and puri®cation were
60±85%.
13,13,13-Tri¯uoro-1-tridecanol. 1H NMR (300 MHz,
CDCl3): ꢀ ˆ 3.61 (t, J ˆ 6.6 Hz, 2H), 2.12±1.95 (m, 2H),
1.65 (br s, OH), 1.58±1.47 (m, 4H), 1.36±1.22 (m, 16H).
14,14,15,15,15-Penta¯uoro-1-pentadecanol. 1H NMR
(300 MHz, CDCl3): ꢀ ˆ 3.62 (t, J ˆ 6.6 Hz, 2H), 2.07±
1.88 (m, 2H), 1.60±1.51 (m, 5H), 1.36±1.22 (m, 18H).
11,11,12,12,13,13,14,14,14-Nona¯uoro-1-tetradecanol.
1H NMR (300 MHz, CDCl3): ꢀ ˆ 3.62 (t, J ˆ 6.6 Hz, 2 H),
2.14±1.93 (m, 2H), 1.63±1.51 (m, 5H), 1.41±1.21 (m, 12H).
12,12,13,13,14,14,15,15,15-Nona¯uoro-1-pentadecanol.
1H NMR (300 MHz, CDCl3): ꢀ ˆ 3.62 (t, J ˆ 6.6 Hz, 2H),
2.15±1.94 (m, 2H), 1.64±1.51 (m, 5H), 1.41±1.20 (m, 14H).
13,13,14,14,15,15,16,16,16-Nona¯uoro-1-hexadecanol.
1H NMR (300 MHz, CDCl3): ꢀ ˆ 3.61 (t, J ˆ 6.6 Hz, 2H),
2.06±1.87 (m, 2H), 1.62±1.51 (m, 5H), 1.35±1.22 (m, 16H).
1
(75.5 MHz, CDCl3): ꢀ ˆ 127.26 (q, JCF ˆ 276 Hz),
2
34.05, 33.70 (q, JCF ˆ 28 Hz), 29.70 (5C), 29.54, 29.35,
29.17, 29.07, 28.68, 28.37, 24.63, 21.82. Anal. Calc. for
C16H31F3S: C, 61.50; H, 10.00. Found C, 61.86; H, 9.81.
15,15,16,16,16-Penta¯uorohexadecanethiol. 1H NMR
(300 MHz, CDCl3): ꢀ ˆ 2.50 (q, J ˆ 7.2 Hz, 2H), 2.07±
1.90 (m, 2H), 1.64±1.51 (m, 4H), 1.36±1.21 (m, 21H). 13C
1
NMR (75.5 MHz, CDCl3): ꢀ ˆ 119.24 (tq, JCF ˆ 285 Hz,
1
2
2JCF ˆ 36 Hz), 115.82 (qt, JCF ˆ 251 Hz, JCF ˆ 37 Hz),
2
34.05, 30.27 (t, JCF ˆ 22 Hz), 29.58 (5C), 29.53, 29.36,
29.18, 29.07, 28.37, 24.62, 20.20. Anal. Calc. for
C16H29F5S: C, 55.15; H, 8.39. Found: C, 55.55; H, 8.30.
14,14,15,15,16,16,16-Hepta¯uorohexadecanethiol. 1H
NMR (300 MHz, CDCl3): ꢀ ˆ 2.51 (q, J ˆ 7.2 Hz, 2H),
2.11±1.93 (m, 2H), 1.64±1.53 (m, 4H), 1.38±1.22 (m, 19H).
13C NMR (75.5 MHz, CDCl3): ꢀ ˆ 117.90 (qt,
1JCF ˆ 287 Hz, JCF ˆ 34 Hz), 117.77 (tt, JCF ˆ 252 Hz,
2
1
1
2
2JCF ˆ 31 Hz), 108.90 (ttq, JCF ˆ 263 Hz, JCF ˆ 37 Hz),
2
34.05, 30.59 (t, JCF ˆ 22 Hz), 29.55 (4C), 29.51, 29.36,
29.20, 29.07, 28.37, 24.65, 20.02. Anal. Calc. for
C16H27F7S: C, 49.99; H, 7.08. Found: C, 49.61; H, 6.89.
13,13,14,14,15,15,16,16,16-Nona¯uorohexadecanethiol.
1H NMR (300 MHz, CDCl3): ꢀ ˆ 2.50 (q, J ˆ 7.2 Hz, 2H),
2.14±1.92 (m, 2H), 1.64±1.51 (m, 4H), 1.42±1.22 (m, 17H).
13C NMR (75.5 MHz, CDCl3): ꢀ ˆ 118.31 (tt,
1JCF ˆ 253 Hz, JCF ˆ 31 Hz), 117.42 (qt, JCF ˆ 288 Hz,
2JCF ˆ 31 Hz), 113.24±100.77 (ttq; ttt, 2C), 34.04, 30.77 (t,
2JCF ˆ 22 Hz), 29.49 (4C), 29.34, 29.20, 29.07, 28.36,
24.63, 20.04. Anal. Calc. for C16H25F9S: C, 45.71; H,
5.99. Found: C, 45.82; H, 5.72.
2
1
2.7. Terminally perfluorinated alcohols 6 (general
procedure)
2.8. Terminally perfluorinated alkyl thioacetates 3 from
fluorinated alcohols 6 (general procedure)
The radical addition of RFI (55.0 mmol) to the w-alkenol
acetate, w-alkenoic methyl ester, or w-alkenol (50.0 mmol)
in the presence of AIBN was performed as described
above for coupling with the w-alkyl thioacetate. The
crude secondary iodide 5 was dissolved in 100 ml of glacial
acetic acid. Zinc dust (150 mmol) was added at room
temperature under argon. Compounds that were insoluble
in glacial acetic acid were dissolved in a minimum
amount of dry THF and then added to the Zn / HOAc slurry.
The mixture was stirred for 16 h and then ®ltered through
Celite. The ®ltrate was evaporated to dryness and redis-
solved in diethyl ether (ca. 100 ml). The solution was
washed with water (2 Â 100 ml), saturated aqueous
NaHCO3 solution (1 Â 100 ml), and brine (1 Â 100 ml),
and then dried over MgSO4. Removal of the solvent
afforded the crude terminally ¯uorinated acetate, ester, or
To a stirred solution of alcohol 6 (2.83 mmol) in 50 ml of
hexane at room temperature were added triethylamine
(8.49 mmol) and methanesulfonyl chloride (5.66 mmol).
After stirring for 2 h, 50 ml of water was added. The phases
were separated, the organic layer was washed with water
(1 Â 100 ml) and brine (1 Â 100 ml), dried with MgSO4,
and evaporated to dryness. The crude mesylate was dis-
solved in 50 ml of absolute ethanol. Under argon, potassium
thioacetate (5.66 mmol) was added. The mixture was
warmed to 608C for 2 h under argon. After cooling to room
temperature, 150 ml of water was added, and the mixture
was extracted with hexane (3 Â 100 ml). The combined
organic layers were washed with brine (1 Â 100 ml) and
dried over MgSO4. The solvent was removed by rotary
evaporation. The crude product was puri®ed by column
chromatography on silica gel (hexane / diethyl ether ˆ 9 /
1) affording the terminally per¯uorinated thioacetate 3 in ca.
90% yield.
1
alcohol. If analysis by H NMR showed contamination by
the ole®nic starting material, the ¯uorinated alcohol was
treated with N-methyl-a-phenyl nitrone as described above.
Contaminated acetate and ester products, however, were
dissolved in 100 ml of CH2Cl2 and cooled to ca. 108C
14,14,15,15,15-Penta¯uoropentadecyl thioacetate. 1H
NMR (300 MHz, CDCl3): ꢀ ˆ 2.85 (t, J ˆ 7.2 Hz, 2H),

112
M. Graupe et al. / Journal of Fluorine Chemistry 93 (1999) 107±115
2.31 (s, 3H), 2.08±190 (m, 2H), 1.61±1.50 (m, 4H), 1.40±
1.22 (m, 18H).
2.11. 16,16,16-Trifluorohexadecyl thioacetate (9)
11,11,12,12,13,13,14,14,14-Nona¯uorotetradecyl thioa-
cetate. 1H NMR (300 MHz, CDCl3): ꢀ ˆ 2.84 (t,
J ˆ 7.4 Hz, 2H), 2.30 (s, 3H), 2.15±1.90 (m, 2H), 1.61±
1.48 (m, 4H), 1.40±1.20 (m, 12H).
12,12,13,13,14,14,15,15,15-Nona¯uoropentadecyl thioa-
cetate. 1H NMR (300 MHz, CDCl3): ꢀ ˆ 2.83 (t,
J ˆ 7.4 Hz, 2H), 2.29 (s, 3H), 2.13±1.93 (m, 2H), 1.64±
1.49 (m, 4H), 1.42±1.20 (m, 14H).
13,13,14,14,15,15,16,16,16-Nona¯uorohexadecyl thioa-
cetate. 1H NMR (300 MHz, CDCl3): ꢀ ˆ 2.84 (t,
J ˆ 7.4 Hz, 2H), 2.30 (s, 3H), 2.10±1.89 (m, 2H), 1.62±
1.48 (m, 4H), 1.41±1.22 (m, 16H).
A mixture of alkene 8 (2.50 g; 8.98 mmol), thioacetic
acid (2.67 g; 35.1 mmol) and AIBN (0.06 g; 0.4 mmol)
were combined in a small quartz tube under argon. The
reaction mixture was irradiated for 1 h with a 450 W
mercury high pressure lamp at a distance of 2 in. The
resulting solution was poured into 100 ml of diethyl ether.
Water (50 ml) was added; solid NaHCO3 was then added in
portions until the evolution of CO2 ceased. The mixture was
then extracted with diethyl ether (2 Â 100 ml). The organic
layers were washed with brine (1 Â 100 ml), dried with
MgSO4, and evaporated to dryness by rotary evaporation.
The crude product was chromatographed on silica gel using
hexane as eluent to give 1.50 g (4.23 mmol; 47% yield) of
1
2.9. 13,13,13-Trifluorotridecyl iodide (7)
thioacetate 9. H NMR (300 MHz, CDCl3): ꢀ ˆ 2.84 (t,
J ˆ 7.2 Hz, 2H), 2.30 (s, 3H), 2.12±1.95 (m, 2H), 1.59±1.47
To a stirred solution of 8.10 g (32.0 mmol) of alcohol 6 in
100 ml of hexane at room temperature were added 13.3 ml
(96.0 mmol) of triethylamine and 4.93 ml (64.0 mmol)
methanesulfonyl chloride. After stirring for 2 h, 200 ml
of water was added. The phases were separated, the organic
layer was washed with water (1 Â 100 ml) and brine
(1 Â 100 ml), dried with MgSO4, and evaporated to dryness.
The crude mesylate was then dissolved in 500 ml of acetone.
Potassium iodide (16.6 g; 100 mmol) was added, and
the mixture was re¯uxed for 12 h. After cooling, 200 ml
of water was added, and the mixture was extracted with
hexane (2 Â 250 ml). The combined organic layers were
washed with brine (1 Â 250 ml), dried with MgSO4, and
evaporated to dryness by rotary evaporation. Kugelrohr
distillation of the crude product gave 10.5 g (29.0 mmol;
90% yield) of iodide 7. 1H NMR (300 MHz, CDCl3):
ꢀ ˆ 3.18 (t, J ˆ 7.2 Hz, 2H), 2.12±1.96 (m, 2H), 1.85±
1.76 (quint, J ˆ 7.2 Hz, 2H), 1.58±1.48 (m, 2H), 1.39±
1.22 (m, 16H).
(m, 4H), 1.35±1.22 (m, 22H).
3. Results and discussion
The key step in our synthetic approach involves the
radical addition of ¯uorinated alkyl iodides to terminally
unsaturated alkyl thioacetates (Scheme 1). To obtain the
tri¯uoromethyl- and penta¯uoroethyl-terminated thiols, we
used 2,2,2-tri¯uoroethyl iodide and 2,2,3,3,3-penta¯uoro-
propyl iodide, respectively, instead of tri¯uoromethyl iodide
and per¯uoroethyl iodide, respectively, because the latter
two are gases and are thus more dif®cult to handle. For the
synthesis of more highly ¯uorinated thiols, however, we
used the corresponding per¯uorinated alkyl iodides because
they are liquids at room temperature. As shown in Scheme 1,
we prepared the w-unsaturated alkyl thioacetates 1 in
excellent yields from w-unsaturated bromides by nucleo-
philic displacement with potassium thioacetate.
Secondary iodides 2 were generated by the reaction of w-
alkenylthioacetates 1 with ¯uorinated alkyl iodides (RFI,
Table 1) in the presence of the radical initiator 2,20-azobi-
sisobutyronitrile (AIBN) under oxygen-free conditions.
Dehalogenation of the crude iodides 2 with NaBH4 in
DMF according to the method of Val'pin et al. [32] yielded
the terminally ¯uorinated alkyl thioacetates 3. Small
amounts of ole®nic starting material and variable amounts
of ¯uorinated ole®ns, which apparently formed as elimina-
tion by-products during the dehalogenation reaction, could
not be readily separated from the desired products by
distillation or chromatography. We therefore treated the
product mixture with ozone followed by a reductive workup
with NaBH4 to convert the ole®ns to more polar alcohols,
which could be readily separated by chromatography on
silica gel. Unfortunately, partial oxidation of the thioacetate
group by exposure to excess ozone often led to low yields of
the pure thioacetates (Table 1; Method A1). When, how-
ever, we performed the dehalogenation reaction using zinc
dust in acetic acid, we circumvented the formation of
2.10. 16,16,16-Trifluoro-1-hexadecene (8)
To a solution of 4.13 g (11.0 mmol) of iodide 7 in 150 ml
anhydrous THF were added 11.0 ml of a 0.100 M solution
(1.10 mmol) of LiCuCl4 in THF. The mixture was cooled to
308C under argon. A 1 M solution of allylmagnesium
bromide in diethyl ether (33 ml; 33.0 mmol) was added
slowly over 5 min, during which a color change from orange
to dark brown was observed. The reaction mixture was
warmed to room temperature and stirred for 14 h. After
the addition of 50 ml of a saturated aqueous solution of
NH4Cl and 50 ml of water, the mixture was extracted with
diethyl ether (3 Â 100 ml). The combined organic layers
were washed with brine (1 Â 100 ml), dried with MgSO4,
and evaporated to dryness by rotary evaporation. Kugelrohr
distillation of the crude product gave 2.56 g (9.19 mmol;
81% yield) of alkene 8. 1H NMR (300 MHz, CDCl3):
ꢀ ˆ 5.87±5.74 (m, 1H), 5.01±4.90 (m, 2H), 2.12±1.96 (m,
4H), 1.58±1.49 (m, 2H), 1.36±1.22 (m, 20H).

M. Graupe et al. / Journal of Fluorine Chemistry 93 (1999) 107±115
113
Scheme 1. Synthesis of terminally perfluorinated alkanethiols via radical addition of RFI to w-alkenyl thioacetates (method A).
Table 1
Summary of the syntheses of fluorinated thiol 4
20
Entry
Thiol 4
RFI
Method
Overall
% yield
nD
of 4
1
2
F(CF2)1(CH2)9SH
F(CF2)1(CH2)10SH
F(CF2)1(CH2)11SH
F(CF2)1(CH2)12SH
F(CF2)1(CH2)13SH
F(CF2)1(CH2)14SH
F(CF2)1(CH2)15SH
F(CF2)2(CH2)11SH
F(CF2)2(CH2)12SH
F(CF2)2(CH2)13SH
F(CF2)2(CH2)14SH
F(CF2)3(CH2)10SH
F(CF2)3(CH2)11SH
F(CF2)3(CH2)12SH
F(CF2)3(CH2)13SH
F(CF2)4(CH2)9SH
F(CF2)4(CH2)10SH
F(CF2)4(CH2)11SH
F(CF2)4(CH2)12SH
5
6
7
8
9
F(CF2)1CH2I
F(CF2)1CH2I
F(CF2)1CH2I
F(CF2)1CH2I
F(CF2)1CH2I
F(CF2)1CH2I
F(CF2)1CH2I
F(CF2)2CH2I
F(CF2)2CH2I
F(CF2)2CH2I
F(CF2)2CH2I
F(CF2)3I
A1
A1
A1
A1
A1
A2
C
18
18
18
18
16
60
21
26
21
39
51
24
24
60
58
63
59
57
58
1.4220
1.4246
1.4355
1.4327
1.4340
1.4360
1.4373
1.4180
1.4205
3
4
5
6
10
a
7
8
7
8
A1
A1
B
9
10
11
12
13
14
15
16
17
18
19
1.4246
b
10
7
A2
A1
A1
A2
A2
A2
B
1.4023
1.4077
1.4083
1.4113
1.3880
1.3942
1.3972
1.4011
8
F(CF2)3I
9
F(CF2)3I
F(CF2)3I
10
6
F(CF2)4I
F(CF2)4I
F(CF2)4I
F(CF2)4I
B
B
aAvailability of starting fragments dictated an entirely different strategy (Method C; see text).
bAt 20 8C, the product thiol is a solid (m.p.: 278C).
unsaturated by-products. Furthermore, we could readily
remove any excess ole®nic starting material by reaction
with N-methyl-a-phenyl nitrone [33] in re¯uxing toluene
followed by distillation or chromatography (Table 1:
Method A2).
Acidic deprotection of the thioacetates 3 afforded the
terminally ¯uorinated alkanethiols 4. Deprotection under
acidic conditions generally gave better yields than depro-
tection under basic conditions, which typically led to the
formation of disul®des as by-products.
involving the radical coupling of ¯uorinated alkyl iodides to
w-unsaturated acetates, alcohols, and esters (Scheme 2;
Table 1; Method B). Using the latter [34], the crude sec-
ondary iodides 5 were dehalogenated with zinc dust in
acetic acid. Ozonolysis of the crude product was used to
destroy any ole®nic starting material, and the appropriate
reductive workup afforded the terminally ¯uorinated alco-
hols 6. These alcohols were then transformed into the
thioacetates 3 via mesylation and subsequent treatment with
potassium thioacetate. Acidic deprotection gave the ¯uori-
nated thiols 4.
We brie¯y compared our new approach involving the
radical coupling of ¯uorinated alkyl iodides with w-unsa-
turated thioacetates (Scheme 1; Table 1: Methods A1 and
A2) to that of an analogous `Brace-based' approach [4,6]
The synthesis of F(CF2)4(CH2)9SH (entry 16 in Table 1)
utilized our Method A2 to generate the target compound in
63% overall yield. The synthesis of F(CF2)4(CH2)10SH,

114
M. Graupe et al. / Journal of Fluorine Chemistry 93 (1999) 107±115
Scheme 2. Synthesis of terminally perfluorinated alkanethiols via method B.
F(CF2)4(CH2)11SH, and F(CF2)4(CH2)12SH (entries 17±19,
respectively) utilized `Brace-based' Method B to generate
the targeted compounds in ca. 58% yield. This brief com-
parison thus suggests that the overall yields obtained using
our approach are comparable to those obtained using an
approach based on Brace's methods.
Due to the poor availability of a suitable terminally
unsaturated 14-carbon starting material, the synthesis of
F(CF2)1(CH2)15SH required a strategy different from those
outlined above (see Scheme 3, Table 1: Method C). In this
example, we utilized Brace's method of radical addition to
provide the primary alcohol 6 with n ˆ 8. This intermediate
was converted to the primary iodide 7 via mesylation and
nucleophilic displacement of the mesylate with potassium
iodide. Treatment of iodide 7 with allylmagnesium bromide
in the presence of lithium tetrachlorocuprate [35] gave
ole®n 8 in good yield. Photochemical addition of thioacetic
acid [36,37] to the terminal double bond yielded thioacetate
9, which was hydrolyzed under acidic conditions to yield the
targeted thiol.
¯uorinated terminal segments: F(CF2)m(CH2)nSH, where
m ˆ 1, n ˆ 9±15; m ˆ 2, n ˆ 11±14; m ˆ 3, n ˆ 10±13;
and m ˆ 4, n ˆ 9±12. Radical addition of F(CF2)1CH2I,
F(CF2)2CH2I, F(CF2)3I and F(CF2)4I to w-alkenylthioace-
tates provided a short and convenient synthetic route to this
important class of compounds. Due to the inherently poor
solubility of long-chain per¯uorocarbons, the present strat-
egy offers a distinct advantage over analogous `Brace-
based' synthetic strategies that necessarily require extensive
post-functionalization of the ¯uorocarbon intermediates.
Furthermore, the demonstrated ability of performing radical
additions of ¯uorinated iodides to alkenes in the presence of
thioacetate moieties should prove to be a useful tool in other
areas of ¯uorocarbon chemistry.
Acknowledgements
We thank the University of Houston Energy Laboratory
for providing seed funding and the National Science Foun-
dation (DMR-9700662) for current support of this research.
Acknowledgement is made to the donors of The Petroleum
Research Fund, administered by the ACS, for partial support
of this research (ACS-PRF#30614-G5). T.K. gratefully
4. Summary
È
acknowledges support from the `Fonds zur Forderung der
wissenschaftlichen Forschung' (FWF) in the form of an
We synthesized 19 new terminally ¯uorinated alka-
nethiols having the following chain lengths and speci®cally
Scheme 3. Synthesis of F(CF2)1(CH2)15SH via method C.

M. Graupe et al. / Journal of Fluorine Chemistry 93 (1999) 107±115
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