A novel pyrrolidinium ionic liquid with 1,1,2,2-tetrafluoro-2-(1,1,2,2-tetrafluoroethoxy)ethanesulfonate anion as a recyclable reaction medium and efficient catalyst for Friedel-Crafts alkylations of indoles with nitroalkenes

Article abstract of DOI:10.1016/j.jfluchem.2009.01.004

A series of pyrrolidinium-based salts with new fluorine-containing anions were synthesized. Different melting points could be obtained by changing the length of the fluoroalkyl chain of the anions. The pyrrolidinium 1,1,2,2-tetrafluoro-2-(1,1,2,2-tetraflu

Full text of DOI:10.1016/j.jfluchem.2009.01.004

Journal of Fluorine Chemistry 130 (2009) 394–398
Contents lists available at ScienceDirect
Journal of Fluorine Chemistry
journal homepage: www.elsevier.com/locate/fluor
A novel pyrrolidinium ionic liquid with 1,1,2,2-tetrafluoro-2-(1,1,2,2-
tetrafluoroethoxy)ethanesulfonate anion as a recyclable reaction medium and
efficient catalyst for Friedel–Crafts alkylations of indoles with nitroalkenes
*
Jin-Hong Lin, Cheng-Pan Zhang, Zhi-Qiang Zhu, Qing-Yun Chen, Ji-Chang Xiao
Key Laboratory of Organofluorine Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, PR China
A R T I C L E I N F O
A B S T R A C T
Article history:
A series of pyrrolidinium-based salts with new fluorine-containing anions were synthesized. Different
melting points could be obtained by changing the length of the fluoroalkyl chain of the anions. The pyrroli-
dinium 1,1,2,2-tetrafluoro-2-(1,1,2,2-tetrafluoroethoxy)ethanesulfonate ([C4H8NH2][H(CF2)4O(CF2)2SO3])
is highly fluid even below room temperature. It can be used both as a recyclable solvent and as an efficient
catalyst for Friedel–Crafts alkylations of indoles with nitroalkenes.
Received 30 December 2008
Received in revised form 15 January 2009
Accepted 19 January 2009
Available online 30 January 2009
ß 2009 Elsevier B.V. All rights reserved.
Keywords:
Pyrrolidinium
Ionic liquid
Fluorine
Friedel–Crafts alkylation
1. Introduction
[22–25]. Thus, it occurred to us to explore low melting point
pyrrolidinium salts using polyfluoroalkanesulfonate as the anion.
Ionic liquids (ILs) have attracted growing academic and
industrial interest because of their special properties such as
excellent thermal and chemical stability, low vapor pressure and
good tunable solubility [1–6]. They have been widely used in
organic catalysis, electrochemistry and so on [7–15]. Much
attention has been paid on the exploration of new kinds of ILs.
Although thousands of ILs were synthesized in the past decades,
the most commonly used cations are N,N0-dialkylimidazolium and
N-alkylpyridinium. The pyrrolidinium-based ionic liquids have
been much less studied. Our experiences in the synthesis and
application of biimidazolium and bipyridinium ILs prompted us to
extend our investigation to pyrrolidinium ILs [16,17].
Pyrrolidinium salts can be easily obtained from the neutraliza-
tion of pyrrolidine with Brønsted acids [18–20]. Unfortunately, the
melting points of these salts are often higher than room
temperature. It is well known that many factors have been
identified with respect to lowering melting points of ILs, such as
ion asymmetry, large ion size, delocalization of ion charge and so
on [21]. And it has been reported that ILs containing highly
fluorinated anions such as [NTf2]ꢀ, [RfBF3]ꢀ and [B(Arf)4]ꢀ, often
exhibit lower melting points than those non-fluorine analogues
Herein, we report the synthesis and applications of pyrrolidinium
ionic liquids with polyfluoroalkanesulfonate anions.
2. Results and discussion
Pyrrolidinium salts with perfluoroalkanesulfonate anions were
synthesized in quantitative yields by the neutralization of
pyrrolidine with the corresponding acids (Scheme 1). However,
this direct neutralization could not be applied for the syntheses of
pyrrolidinium
1,1,2,2-tetrafluoro-2-(1,1,2,2-tetrafluoroethox-
y)ethanesulfonate ([C4H8NH2][(H(CF2)4O(CF2)2SO3]) (1f). Fortu-
nately, quaternization of pyrrolidine with nitric acid could proceed
smoothly to give the corresponding pyrrolidinium nitrate as a
yellow solid. Subsequent metathetical reaction with 1,1,2,2-
tetrafluoro-2-(1,1,2,2-tetrafluoroethoxy)ethanesulfonate resulted
in the formation of 1f in 95% yield (Scheme 1). The thermal
properties of the pyrrolidinium salts were determined by
differential scanning calorimetry (DSC) and thermogravimetric
analysis (TGA) as summarized in Table 1.
The melting points of ILs depend largely on the anions.
Generally speaking, ILs containing bis(trifluoromethanesulfony-
l)imide ion ((CF3SO2)2Nꢀ) have lower melting points than others
[22,23]. Reviewing the literatures and combining with our result
on pyrrolidinium salts, we found that the triflimide (mp = 35 8C)
[19] showed a lower melting point than the corresponding
* Corresponding author. Fax: +86 21 6416 6128.
E-mail address: jchxiao@mail.sioc.ac.cn (J.-C. Xiao).
0022-1139/$ – see front matter ß 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.jfluchem.2009.01.004

J.-H. Lin et al. / Journal of Fluorine Chemistry 130 (2009) 394–398
395
Scheme 1. Preparation of pyrrolidinium salts.
hexafluorophosphate (mp = 282 8C) [18] and tetrafluoroborate
(Table 1, entry 1). Using perfluoroalkanesulfonates as the anions,
the pyrrolidinium salts are still solid at room temperature and melt
above 100 8C (entries 2–5). Much to our surprise, when
polarity of ionic liquids [25]. Therefore, the above mentioned
phenomenon might be interpreted as ‘like dissolves like’ [29].
[C4H8NH2][H(CF2)4O(CF2)2SO3] 1f can be regarded as a Brønsted
acidic ionic liquid. Brønsted acids are usually used as catalysts for
Friedel–Crafts alkylation [30–34]. Friedel–Crafts reaction of
indoles with nitroalkenes was always catalyzed by Brønsted acids
and Lewis acids [34–37]. But the issue of catalyst recycling and
reuse still remains to be addressed. To the best of our knowledge, it
has never been reported that ILs were used as both the solvent and
catalyst for Friedel–Crafts alkylation of indoles with nitroalkenes.
Hence, we explored the application of the Brønsted acidic IL
[C4H8NH2][H(CF2)4O(CF2)2SO3] as both the recyclable solvent and
catalyst for this reaction.
ꢀ
H(CF2)4O(CF2)2SO3 was employed as the anion, the salt 1f is
liquid and highly fluid even below room temperature (entry 6). The
reasons may be rationalized as follows: (a) the charge of the anion
is highly delocalized and shielded by the polyfluoroalkyl group
from Coulombic interactions with neighboring cations. So ion
mobility will be increased [21,26]; (b) long polyfluoroalkyl chain
means large anion size, which contributes to lower melting point
of ILs [21]; (c) because of repulsive stretching by the 1,3-
difluoromethylene groups, perfluorocarbons are rigid, rod-like
molecules [27]. However, introducing an oxygen atom into the
long fluoroalkyl group can increase ion flexibility. As a result, IL 1f
can be liquid even below room temperature.
Variable solubility of salts in organic solvents is another
interesting physicochemical property. The influence of anion on
the solubility was then investigated at room temperature (Table 2).
It can be seen that all of the salts are completely soluble in water
and polar organic solvents like ethanol and tetrahydrofuran
(entries 1–3). Unexpectedly, the solubility in water seems not to
be affected by the length of the fluoroalkyl chain on the anion
(entry 1) [28]. The good water solubility of salts with long
fluoroalkyl chain might result from the strong hydratability of
the cation. With elongation of the fluoroalkyl chain, most salts
are soluble in ethyl acetate, chloroform and dichloromethane
(entries 4–6). The salts with long fluoroalkyl chain, e.g.,
[C4H8NH2][nC8F17SO3] and [C4H8NH2][H(CF2)4O(CF2)2SO3] are
even soluble in diethyl ether (entry 7). It is well known that an
increase in the size of the anion is accompanied by a decrease in the
The reaction of indole with trans-b-nitrostyrene was firstly
chosen as the model reaction (Table 3). From a preliminary
screening, it was found that increasing the temperature led to the
significant improvement of the yield (entries 1 and 2). At 50 8C,
reducing the ratio of indole to nitrostyrene decreased the yield of
4a (entries 2–5). Thus, we determined that the ratio 2:1 of indole to
nitrostyrene and the temperature of 50 8C were adopted as the
optimal conditions for the reaction.
Then a series of different substituted indoles and nitrostyrenes
were subjected to this optimal reaction conditions (Table 4). In most
cases,thedesiredFriedel–Craftsalkylatedproductswereobtainedin
good yields (entries 1–6, 8 and 9). The substituents on indoles had a
significant effect on the reactivity. Considerably longer time was
necessary for the reaction of indole with bromine on the phenyl ring
and the yield became relatively low, which might be resulted from
the low electron density of the aromatic ring (entry 7).
IL 1f could be easily recycled after extraction with toluene and
drying under vacuum. It is worth mentioning that the recycled IL
can be directly used in the next reaction till the last run without
significant decrease in catalytic performance (Table 4, entries 1–9).
Determined by 1H NMR and 19F NMR, the ionic liquid 1f was found
to be in its original state even if it turned brown after 3 runs.
Table 1
Thermal properties of the pyrrolidinium salts.
Table 2
Solubility of pyrrolidium salts in organic solventsa.
.
Entry
IL
1a
1b
1c
1d
1f
Entry
X
Tg (8C)a
mp (8C)b
Td (8C)c
1
2
3
4
5
6
7
8
9
H2O
m
m
m
m
m
d
1
2
3
4
5
6
BF4
ꢀ50
ꢀ68
ꢀ12
–
74
109
148
110
120
–
344
426
371
408
393
378
EtOH
m
m
m
m
m
CF3SO3
THF
m
m
m
m
m
CF3(CF2)3SO3
CF3(CF2)5SO3
CF3(CF2)7SO3
H(CF2)4O(CF2) 2SO3
EtOAc
CHCl3
CH2Cl2
Et2O
nm
nm
nm
nm
nm
nm
m
m
m
m
m
m
m
pm
m
–
m
m
m
ꢀ74
nm
nm
nm
nm
nm
nm
m
m
Toluene
Benzene
nm
nm
nm
nm
a
Glass transition temperature (Tg) determined by DSC.
Melting point (mp) determined by DSC.
Thermal degradation (Td) determined by TGA.
Synthesized according to Ref. [20].
b
c
a
Determined at room temperature; m: miscible; nm: non-miscible; pm:
partially miscible.
d

396
J.-H. Lin et al. / Journal of Fluorine Chemistry 130 (2009) 394–398
Table 3
IL 1f was used as the catalyst rather than the solvent for the
addition of indole to trans- -nitrostyrene. No reaction happened
Friedel–Crafts reaction of indole with trans-b
-nitrostyrenea.
b
in DMSO even if the reaction was performed for 2 days. When
CH2Cl2 was used as the solvent, the reaction proceeded quite well
to give the desired products 4a in 83% yield. The different catalytic
activity of ionic liquid 1f in DMSO and CH2Cl2 might be well
explained by the hydrogen bond formation. Hydrogen bonds are
easy to form between the nitrogen-protons of the cation and the
oxygens of DMSO. Thus, the nitroalkenes could not be activated by
ionic liquid 1f. While in CH2Cl2, there would not be such a
hydrogen bond interaction between ionic liquid 1f and CH2Cl2.
.
3. Conclusions
Entry
2a/3a
T (8C)
Yield (%)b
In summary,
a series of pyrrolidinium-based salts were
1
2
3
4
5
3/1
25
50
50
50
50
62
94
92
88
76
synthesized. The ionic liquid [C4H8NH2][(H(CF2)4O(CF2)2SO3] is
highly fluid even below room temperature. It can be used both as
the recyclable solvent and efficient catalyst for Friedel–Crafts
alkylations of indoles with nitroalkenes. To the best of our
knowledge, this is the first report that an ionic liquid was used as
both the solvent and catalyst for this reaction. On the basis of these
current efforts, it is likely that a number of acid catalyzed reactions
could be performed equally well or perhaps even more effectively
in this ionic liquid. Studies to determine applicability to these
reactions are currently underway.
3/1
2/1
1.5/1
1/1
a
Reaction condition: 2a and 3a in IL (2 ml) at indicated temperature.
b
Isolated yields.
Table 4
Friedel–Crafts alkylation of indoles with nitroalkenes in ionic liquid 1fa.
4. Experimental
4.1. General information
1H NMR spectra were recorded with
a Bruker AM-300
(300 MHz), or Varian VXR (300 MHz) spectrometer. 19F NMR
spectra were recorded with a Bruker AM 300 (282 MHz) with CFCl3
as an external standard (negative for up field). 13C NMR spectra
were recorded with a Bruker AM 300 (75 MHz) spectrometer. MS
was recorded with a Hewlett-Packard HP-5989A spectrometer.
Elemental analyses were obtained with a PerkinElmer 2400 Series
II Elemental Analyzer. Infrared spectra were measured with a
PerkinElmer 983 spectrometer. Glass transition temperature and
melting points and were measured by DSC on PYRIS 1. Thermal
degradation was measured by TGA on Q500. Unless otherwise
noted, reagents were commercially available and used as received.
.
Entry
R1
R2
Ar
Time (h)
Product
Yield (%)b
1
2
3
4
5
6
7
8
9
H
H
Ph
12
12
12
11
24
24
60
12
12
4a
4b
4c
4d
4e
4f
92
91
97
96
96
99
55
99
99
H
H
4-MeO-Ph
4-Cl-Ph
4-NO2-Phc
2-thienyl
2-furyl
Ph
H
H
H
H
H
H
H
H
H
Br
H
4g
4h
4i
4.2. Typical procedure for the neutralization of pyrrolidine and
Me
H
Ph
OMe
Ph
perfluoroalkanesulfonic acid (1a–1d)
a
Reaction condition: 2 (1 mmol) and 3 (0.5 mmol) in IL (2 ml).
Isolated yields.
b
c
To a stirred solution of pyrrolidine (4.26 g, 60 mmol) in water
(10 ml), trifluoromethanesulfonic acid (7.5 g, 50 mmol) was added
slowly at room temperature. Then the reaction was warmed to
60 8C and stirred overnight. The reaction mixture was washed with
diethyl ether (50 ml ꢁ 3). Removing the solvent at reduced
pressure afforded a white solid. A pure product was obtained
after recrystallization from ethanol/diethyl ether.
The reaction proceeded at 60 8C.
Combined with the literature reports [38,39], we proposed that
the reaction might proceed via an ionic liquid–nitroalkene
complex involving an intermolecular double hydrogen bond
between the protons on the nitrogen of the cation and the
oxygens of the nitro group (Scheme 2). To support the hypothesis,
4.3. Procedure for the preparation of pyrrolidinium 1,1,2,2-
tetrafluoro-2-(1,1,2,2-tetrafluoroethoxy)ethanesulfonate (1f)
To a stirred solution of pyrrolidine (40.7 g, 0.55 mol) in water
(60 ml), nitric acid (47 g, 65–68%) was added slowly at room
temperature. Then the reaction mixture was warmed to 60 8C and
stirred overnight. The solution was washed by diethyl ether
(50 ml ꢁ 3). Removing the solvent at reduced pressure gave
pyrrolidinium nitrate as a yellow solid (67 g, 100%).
The solution of pyrrolidinium nitrate (26 g, 194 mmol) in
methanol (50 ml) was added slowly to the solution of sodium
1,1,2,2-tetrafluoro-2-(1,1,2,2-tetrafluoroethoxy)ethanesulfonate
Scheme 2. The proposed intermediate of the reaction.

J.-H. Lin et al. / Journal of Fluorine Chemistry 130 (2009) 394–398
397
(87.5 g, 208 mmol) in methanol (70 ml) and stirred for 12 h at
room temperature. After filtration, the filtrate was concentrated to
give a pale yellow liquid (90.5 g, 99% yield).
ꢀ139.87 to ꢀ140.11 (m, 2F); 13C NMR (CD3OD, 75 MHz)
d
44.80,
23.06; IR (film) (cmꢀ1): 3109, 1610, 1464, 1404, 1349, 1245, 1197,
1148, 1056, 975, 914, 811, 761, 641, 531; MS (ESI): 396.9 [anion]ꢀ;
Anal. Calcd. for C10H11F12NO4S: C, 25.60; H, 2.36; N, 2.98. Found: C,
25.73; H, 2.49; N, 3.10.
4.4. Typical procedure for Friedel–Crafts reaction in ionic liquid
Indole (1 mmol, 117 mg) and trans-
b
-nitrostyrene (0.5 mmol,
4.5.7. 3-(2-Nitro-1-phenylethyl)-1H-indole (4a) [37]
75 mg) were added to ionic liquid 1f and stirred at 50 8C. After the
reaction is complete monitored by TLC, the mixture was extracted
by toluene (3 ml ꢁ 3). The upper-layer was concentrated and then
purified by flash chromatography to afford the Friedel–Crafts
alkylated product. The ionic liquid was used directly for the next
run after removing the solvent.
Yellow oil: 92% yield; 1H NMR (CDCl3, 300 MHz)
d 8.11 (br s,
1H), 7.47–7.04 (m, 10H), 5.20 (t, J = 8.1 Hz, 1H), 5.07 (dd, J = 12.7,
7.2 Hz, 1H), 4.95 (dd, J = 12.7, 8.1 Hz, 1H).
4.5.8. 3-[1-(4-Methoxyphenyl)-2-nitroethyl]-1H-indole (4b) [37]
White powder: 91% yield; 1H NMR (CDCl3, 300 MHz)
d 8.07 (s,
1H), 7.43 (d, J = 8.0 Hz, 1H), 7.36 (d, J = 8.1 Hz, 1H), 7.29–7.16 (m,
3H), 7.07 (t, J = 7.6 Hz, 1H), 7.02 (d, J = 2.5 Hz, 1H), 6.89–6.82 (m,
2H), 5.14 (t, J = 8.0 Hz, 1H), 5.05 (dd, J = 12.2, 8.0 Hz, 1H), 4.89 (dd,
J = 12.2, 8.0 Hz, 1H), 3.77 (s, 3H).
4.5. Characterization data
4.5.1. Pyrrolidinium trifluoromethylsulfonate (1a)
White solid: 90% yield; 1H NMR (D2O, 300 MHz)
d 3.03 (t,
J = 6.9 Hz, 4H), 1.75 (t, J = 6.9 Hz, 4H); 19F NMR (D2O, 282 MHz)
d
4.5.9. 3-[1-(4-Chlorophenyl)-2-nitroethyl]-1H-indole (4c) [37]
ꢀ79.5 (s, 3F); 13C NMR (D2O, 75 MHz)
d
122.36 (q, J = 236 Hz),
Yellow oil: 97 yield; 1H NMR (CDCl3, 300 MHz)
d 8.11 (s, 1H),
48.23, 26.24; IR (film) (cmꢀ1): 3192, 3001, 1595, 1464, 1401, 1282,
1228, 1160, 1029, 909, 884, 760, 628, 574, 516; MS (ESI): 149.0
[anion]ꢀ; Anal. Calcd. for C5H10F3NO3S: C, 27.15; H, 4.56; N, 6.33.
Found: C, 27.30; H, 4.62; N, 6.38.
7.39 (t, J = 7.4 Hz, 2H), 7.33–7.18 (m, 5H), 7.08 (t, J = 7.7 Hz, 1H),
7.04 (d, J = 2.3 Hz, 1H), 5.18 (t, J = 7.7 Hz, 1H), 5.06 (dd, J = 12.3,
7.7 Hz, 1H), 4.91 (dd, J = 7.7, 12.3 Hz, 1H).
4.5.10. 3-[2-Nitro-1-(4-nitrophenyl)ethyl]-1H-indole (4d) [37]
4.5.2. Pyrrolidinium perfluro-n-butylsulfonate (1b)
Yellow solid: 96%yield; 1H NMR (CDCl3, 300 MHz)
d 8.23–8.17
(m, 3H), 7.53 (d, J = 8.1 Hz, 2H), 7.39 (t, J = 8.6 Hz, 2H), 7.26–7.20
(m, 1H), 7.13–7.06 (m, 2H), 5.31 (t, J = 7.5 Hz, 1H), 5.12 (dd, J = 12.8,
7.5 Hz, 1H), 4.99 (dd, J = 12.8, 7.5 Hz, 1H).
White solid:92% yield; 1H NMR (D2O, 300 MHz)
d
3.17–3.12 (m,
4H), 1.89–1.83 (m, 4H); 19F NMR (D2O, 282 MHz)
d
ꢀ80.88 to
ꢀ80.99 (m, 3F), ꢀ114.64 to ꢀ114.80 (m, 2F), ꢀ121.86 to ꢀ122.05
(m, 2F), ꢀ125.97 to ꢀ126.27 (m, 2F); 13C NMR (D2O, 75 MHz)
d
44.94, 22.97; IR (film) (cmꢀ1): 3204, 1600, 1397, 1358, 1243, 1136,
1062, 1051, 1021, 1006, 848, 806, 739, 657, 533; MS (ESI): 298.9
[anion]ꢀ; Anal. Calcd. for C8H10F9NO3S: C, 25.88; H, 2.72; N, 3.77.
Found: C, 25.83; H, 2.74; N, 3.79.
4.5.11. 3-(2-Nitro-1-thiophene-2-ylethyl)-1H-indole (4e) [37]
Yellow oil: 96% yield; 1H NMR (CDCl3, 300 MHz)
d 8.13 (br, 1H),
7.52 (d, J = 8.5 Hz, 1H), 7.39 (d, J = 8.5 Hz, 1H), 7.25–7.19 (m, 2H),
7.15–7.09 (m, 2H), 7.01–6.92 (m, 2H), 5.47 (t, J = 7.7 Hz, 1H), 4.95–
5.10 (m, 2H).
4.5.3. Pyrrolidinium perfluro-n-hexylsulfonate (1c)
White solid:93% yield; 1H NMR (D2O, 300 MHz)
d
3.15 (t,
4.5.12. 3-(1-Furan-2-yl-2-nitroethyl)-1H-indole (4f) [37]
J = 7.2 Hz, 4H), 1.89–1.83 (m, 4H); 19F NMR (D2O, 282 MHz)
d
Yellow oil: 99% yield; 1H NMR (CDCl3, 300 MHz)
d 8.12 (br, 1H),
ꢀ80.92 (t, J = 8.5 Hz, 3F), ꢀ114.54 (t, J = 14.5 Hz, 2F), ꢀ120.91 to
7.56 (d, J = 8.0 Hz, 1H), 7.40–7.35 (m, 2H), 7.25–7.19 (m, 1H), 7.17–
7.10 (m, 2H), 6.33–6.29 (m, 1H), 6.16 (d, J = 3.3 Hz, 1H), 5.25 (t,
J = 7.3 Hz, 1H), 5.06 (dd, J = 12.8, 7.3 Hz, 1H), 4.92 (dd, J = 12.8,
7.3 Hz, 1H).
ꢀ121.17 (m, 2F), ꢀ121.83 to ꢀ122.15 (m, 2F), ꢀ122.75 to ꢀ123.03
(m, 2F), ꢀ126.09 to ꢀ126.34 (m, 2F); 13C NMR (D2O, 75 MHz)
d
45.23, 23.07; IR (film) (cmꢀ1): 3208, 1600, 1398, 1367, 1241, 1200,
1149, 1068, 1033, 892, 703, 644, 623, 567, 525; MS (ESI): 398.9
[anion]ꢀ; Anal. Calcd. for C10H10F13NO3S: C, 25.49; H, 2.14; N, 2.97.
Found: C, 25.54; H, 2.24; N, 3.12.
4.5.13. 4-Bromo-3-(2-Nitro-1-phenylethyl)-1H-indole (4g)
Yellow solid: 55% yield; 1H NMR (CDCl3, 300 MHz)
d 8.21 (br,
1H), 7.38–7.26 (m, 7H), 7.04 (t, J = 8.3 Hz, 1H), 6.97 (d, J = 2.6 Hz,
1H), 5.97 (dd, J = 7.0 Hz, 9.3 Hz, 1H), 5.17 (dd, J = 13.0, 7.0 Hz, 1H),
4.5.4. Pyrrolidinium perfluro-n-octylsulfonate (1d)
White solid:93% yield; 1H NMR (CD3OD, 300 MHz)
d
3.24 (t,
4.91 (dd, J = 13.0, 9.3 Hz, 1H); 13C NMR (CDCl3, 75 MHz)
d 139.35,
J = 7.9 Hz, 4H), 2.04–1.97 (m, 4H); 19F NMR (CD3OD, 282 MHz)
d
137.78, 128.83, 128.07, 127.41, 124.80, 124.20, 123.57, 115.15,
113.83, 110.76, 79.54, 40.43; IR (film) (cmꢀ1): 3404, 3060, 3027,
1613, 1542, 1492, 1481, 1452, 1421, 1378, 1336, 1185, 910, 809,
781, 750, 738, 702, 606; MS (EI): 344, 346, 297, 298, 299, 300, 284,
286, 218, 204; Anal. Calcd. for C16H13BrN2O2: C, 55.67; H, 3.80; N,
8.12. Found: C, 55.64; H, 3.91; N, 8.04.
ꢀ81.76 (t, J = 9.9 Hz, 3F), ꢀ115.11 (t, J = 16.0 Hz, 2F), ꢀ121.09 (s,
2F), ꢀ121.88 to ꢀ122.53 (m, 6F), ꢀ123.13 (s, 2F), ꢀ126.69 (s, 2F);
13C NMR (CD3OD, 75 MHz)
d
45.23, 23.49; IR (film) (cmꢀ1): 3203,
1245, 1202, 1152, 1072, 1039, 941, 645, 624, 558, 524; MS (ESI):
498.9 [anion]ꢀ; Anal. Calcd. for C12H10F17NO3S: C, 25.23; H, 1.76;
N, 2.45. Found: C, 25.12; H, 1.79; N, 2.42.
4.5.14. 2-Methyl-3-(2-nitro-1-phenylethyl)-1H-indole (4h) [37]
4.5.5. Pyrrolidinium nitric (1e) [40]
Yellow solid: 99% yield; 1H NMR (CDCl3, 300 MHz)
d 7.89 (br s,
1H), 7.22–7.39 (m, 7H), 6.99–7.13 (m, 2H), 5.06–5.27 (m, 3H), 2.42
(s, 3H).
1H NMR (CDCl3, 300 MHz)
1.90–2.03 (m, 4H).
d
8.39 (br, 2H), 3.23–3.38 (m, 4H),
4.5.6. Pyrrolidinium 1,1,2,2-tetrafluoro-2-(1,1,2,2-
4.5.15. 4-Methoxy-3-(2-nitro-1-phenylethyl)-4-1H-indole (4i)
tetrafluoroethoxy)ethanesulfonate (1f)
White solid: 99% yield; 1H NMR (CDCl3, 300 MHz)
d 7.99 (br,
1H NMR (CD3OD, 300 MHz)
d
6.70 (tt, J = 51.1, 6.0 Hz, 1H), 3.16–
1H), 7.40–7.26 (m, 5H), 7.12 (t, J = 8.1 Hz, 1H), 6.96 (d, J = 8.1 Hz,
1H), 6.64 (d, J = 2.5 Hz, 1H), 6.52 (d, J = 7.8 Hz, 1H), 5.51 (dd,
J = 10.1, 6.1 Hz, 1H), 5.26 (dd, J = 12.6, 6.1 Hz, 1H), 4.92 (dd, J = 12.6,
3.28 (m, 4H), 1.90–2.03 (m, 4H); 19F NMR (CD3OD, 282 MHz)
d
ꢀ83.47 to ꢀ83.59 (m, 2F), ꢀ84.94 to ꢀ85.15 (m, 2F), ꢀ119.56 (s,
2F), ꢀ128.88 to ꢀ128.98 (m, 2F), ꢀ131.84 to ꢀ131.99 (m, 2F),
10.1 Hz, 1H), 3.91 (s, 3H); 13C NMR (CDCl3, 75 MHz)
d 154.20,

398
J.-H. Lin et al. / Journal of Fluorine Chemistry 130 (2009) 394–398
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139.71, 138.16, 128.63, 127.97, 127.18, 123.55, 121.50, 116.26,
115.41, 104.58, 99.99, 79.81, 55.13, 42.27; IR (film) (cmꢀ1): 3419,
3002, 2970, 2939, 2910, 2839, 1618, 1589, 1540, 1507, 1465, 1453,
1435, 1416, 1377, 1363, 1316, 1259, 1230, 1200, 1120, 1083, 1053,
999, 799, 780, 750, 738, 730, 705, 690, 622, 547; MS (EI): 296, 250,
249, 236, 220; Anal. Calcd. for C17H16N2O3: C, 68.91; H, 5.44; N,
9.45. Found: C, 68.67; H, 5.37; N, 9.41.
Acknowledgements
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We thank the Chinese Academy of Sciences (Hundreds of
Talents Program) and the National Natural Science Foundation
(20772147) for financial support.
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