Synthesis of 2,5-diarylpyrroles by ligand-free palladium-catalyzed ch activation of pyrroles in ionic liquids

Article abstract of DOI:10.1002/cctc.201300099

The palladium-catalyzed CH activation and arylation of N-methylpyrrole and N-phenylpyrrole allowed a convenient synthesis of diarylpyrroles. The reactions were performed by using tetrabutylammonium acetate as an ionic solvent, which allowed for the application of a ligand-free catalytic system by using simple palladium salts or polyvinylpyrrolidone-stabilized palladium nanoparticles as the catalyst.

Full text of DOI:10.1002/cctc.201300099

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DOI: 10.1002/cctc.201300099
Synthesis of 2,5-Diarylpyrroles by Ligand-Free Palladium-
Catalyzed CH Activation of Pyrroles in Ionic Liquids
Peter Ehlers,[a, b] Andranik Petrosyan,[a, b, c] Jens Baumgard,[a, b] Stefan Jopp,[a, b]
Norbert Steinfeld,[b] Tariel V. Ghochikyan,[c] Ashot S. Saghyan,[c, d] Christine Fischer,[b] and
Peter Langer*[a, b]
The palladium-catalyzed CH activation and arylation of N-
methylpyrrole and N-phenylpyrrole allowed a convenient syn-
thesis of diarylpyrroles. The reactions were performed by using
tetrabutylammonium acetate as an ionic solvent, which al-
lowed for the application of a ligand-free catalytic system by
using simple palladium salts or polyvinylpyrrolidone-stabilized
palladium nanoparticles as the catalyst.
Introduction
Arylated pyrroles are important compounds in chemi-
cal research with applications ranging from natural
product chemistry to materials science (Figure 1).[1]
Arylpyrroles have found many applications in phar-
maceutical chemistry as they can bind to a variety of
different receptors. For example, they have been re-
ported to act as lipoxygenase, myosin ATPase, and b-
secretase inhibitors.[2] Owing to the widespread appli-
cations of arylated pyrroles, the development of new
and more convenient synthetic methods is a topic of
ongoing interest.[3] In this context, palladium-cata-
lyzed cross-coupling reactions, such as Suzuki–
Miyaura, Stille, or Negishi coupling reactions, play an
important role.[4] In recent years, palladium-catalyzed
CH activations have been established as an interest-
ing alternative to common cross-coupling reactions.[5]
The application of this methodology avoids the draw-
backs of stoichiometrically employed organometallic
reagents (that have a relatively high price, toxicity,
and sensitivity to air and moisture). On the other
hand, activation of a comparatively inert CH bond
often requires high temperatures and toxic solvents,
Figure 1. Applications of different arylpyrroles. PLED=Polymer light-emitting diodes.
such as DMF, dimethylamine (DMA), or N-methylpyr-
[a] P. Ehlers, A. Petrosyan, J. Baumgard, S. Jopp, Prof. Dr. P. Langer
Institut fꢀr Chemie
rolidone (NMP).[6] The functionalization of electron-rich hetero-
cycles has become a major topic in the field of palladium-cata-
lyzed CH activation reactions based on a PdII/Pd0 catalytic
cycles.[7] Owing to the polarization of the molecule by the het-
eroatom, the catalyst generally attacks selectively on the posi-
tion with the lowest electron density. The potential of palladi-
um(0)-catalyzed CH arylation reactions has intensively been
studied by several research groups, especially by the groups of
Doucet,[8] Fagnou,[9] and Daugulis.[10]
Universitꢁt Rostock
Albert Einstein Str. 3a, 18059 Rostock (Germany)
[b] P. Ehlers, A. Petrosyan, J. Baumgard, S. Jopp, Dr. N. Steinfeld, Dr. C. Fischer,
Prof. Dr. P. Langer
Leibniz-Institut fꢀr Katalyse an der Universitꢁt Rostock e.V.
Albert Einstein Str. 29a, 18059 Rostock (Germany)
[c] A. Petrosyan, Prof. Dr. T. V. Ghochikyan, Prof. Dr. A. S. Saghyan
Faculty of Chemistry
Yerevan State University
Alex Manoogian 1, 0025 Yerevan (Armenia)
Most of the reported studies directed towards direct aryla-
tion reactions of heterocycles are related to monoaryla-
tions.[8–11] In contrast, multiple CH activation is rare.[12] For that
[d] Prof. Dr. A. S. Saghyan
Scientific and Production Center “Armbiotechnology” of NAS RA
Gyurjyan str. 14, 0056 Yerevan (Armenia)
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reason, we examined the possibility of double CH activation re-
actions of different N-substituted pyrroles. In 2009, Doucet re-
ported the monoarylation of different functionalized pyrroles
under phosphine-free conditions using KOAc or K2CO3 as the
base and DMA as the solvent.[13] During writing this manuscript
we became aware that Doucet et al. also very recently pub-
lished the synthesis of diarylpyrroles through palladium-cata-
lyzed CH activation.[14] Nevertheless, our target was to establish
a ligand-free method and to avoid the use of toxic solvents,
such as DMA or NMP (Figure 2). In this context, we studied the
use of ionic liquids and palladium nanoparticles as the solvent
the use of DMA gave diarylpyrrole 3a in a low yield along with
monoarylated pyrrole 2 as the major product, employment of
the biodegradable polymer poly(ethylene glycol) (PEG-400) as
the solvent resulted in the formation of 3a as the major prod-
uct, which was isolated in 41% yield. Recently, it was reported
that phase-transfer catalysts may have a positive impact on CH
activation reactions.[15] It is known that the acetate ion can act
as integral part of the reaction mechanism.[16] Therefore, we se-
lected tetrabutylammonium acetate (TBA-Ac) as the phase-
transfer catalyst and obtained product 3a in 34% yield
(entry 4). Subsequently, we used TBA-Ac as the solvent, which
resulted in a dramatic increase of the isolated yield of 3a
(75%). Analysis of the crude product revealed that 3a was pre-
dominantly formed (3a/2a=31:1, entry 5).
We next studied the use of other palladium catalysts and
bases. Employment of palladium pivaloate [Pd(OPiv)2] as a cata-
lyst precursor and cesium pivaloate as the base led to a further
slight increase of the yield of 3a, which was now exclusively
formed (79%, entry 8). Other ionic liquids derived from ammo-
nium or imidazolium salts were less efficient, which highlights
the importance of the employed ammonium cations and ace-
tate anions (entries 6, 7, 9, 12).
Figure 2. Target reaction: Palladium-catalyzed ligand-free synthesis of
2,5-diarylpyrroles.
and catalyst, respectively. Therefore, we believe that, despite
the report of Doucet, our work presented herein will be inter-
esting for a wide range of organic and medicinal chemists.
Having optimized conditions in our hands, we next studied
the scope of the reaction and prepared a variety of diarylpyr-
roles from various aryl bromides. The results are presented in
Table 2. Electron-poor aryl bromides gave good yields of the
diarylated products, whereas the electron-rich aryl bromides
were converted in moderate yields. Sterically hindered ortho-
substituted aryl bromides were less reactive in the reaction
(products 3d and 3k). The moderate yield of compound 3 f
can be explained by a second arylation through the chloro
substituent. The employment of 2-bromothiophene resulted in
the formation of a complex mixture, owing to additional CH
activation reactions of the thiophene moiety. The relatively low
yield of product 3i (in comparison to the yields of products
derived from other electron-poor substrates) can be explained
by the formation of reasonable amounts of triarylated pyrrole.
Aryl chlorides are often much cheaper than aryl bromides,
because they represent industrial products that are prepared
on a large scale. Therefore, we studied the applicability of our
methodology to aryl chlorides. The results are presented in
Table 3. Aryl chlorides containing electron-withdrawing groups
were successfully employed and gave the desired products in
moderate yields. In contrast, the use of electron-rich 4-chloroa-
nisole failed (no product was formed). However, addition of
XPhos allowed the isolation of the desired product 3h, albeit
in low yield.
Results and Discussion
For initial tests we chose the reaction of N-methylpyrrole with
bromobenzene under typical ligand-free conditions (Table 1).
First, palladium(II) acetate and potassium acetate were used as
the catalyst precursor and base, respectively. The yields and
the ratio between mono- and diarylated products were highly
influenced by the choice of the solvent (entries 1–3). Whereas
Table 1. Optimization of the synthesis of N-methyl-2,5-diphenylpyrrole
(3a).[a]
Entry PdX2
Base
Solvent
Additive Ratio Yield 3a [%][c]
2/3a[b]
1
2
3
4
5
6
7
8
Pd(OAc)2 KOAc NMP
Pd(OAc)2 KOAc DMA
–
–
–
2:1
3:1
1:2
21
7
Pd(OAc)2 KOAc PEG-400
Pd(OAc)2 KOAc PEG-400
Pd(OAc)2 KOAc TBA-Ac
Pd(OAc)2 KOAc TBA-Br
Pd(OAc)2 KOAc [C2MIM][BF4][d]
Pd(OPiv)2 CsOPiv TBA-Ac
Pd(OPiv)2 CsOPiv TBA-OPiv
41
34
75
28
0
79
63
43
0
TBA-Ac 1:1
–
–
–
–
–
–
–
–
1:37
1:1
0
0:1
0:1
0:1
–
Our next step was to elucidate the impact of the N-protect-
ing group of pyrrole to get insight into the scope and limita-
tions of the developed catalytic system. Thus, we tested N-tert-
butoxycarbonyl (N-Boc)-protected pyrrole and N-phenylpyrrole
under the established conditions. Whereas N-Boc protected
pyrrole gave no reasonable yields of diarylated products, N-
phenylpyrrole reacted smoothly to give the appropriate diary-
lated pyrroles in moderate yields (Table 4). As expected, elec-
tron-poor aryl bromides were more reactive than electron-rich
aryl bromides. Aryl chlorides gave lower yields than the corre-
9
10
11
12
Pd(OPiv)2
–
–
TBA-Ac
KOAc TBA-Ac
Pd(OPiv)2 CsOPiv [C2MIM][OAc]
–
0
[a] Reaction conditions: Pd(X)2 (1 mol%), base (3.0 equiv.), PhÀBr
(3.0 equiv.), solvent, additive, 1408C, 20 h. [b] Determined by 1H NMR-
spectroscopy of the crude product. [c] Yield of isolated products.
[d] [C2MIM][BF4]=(1-ethyl-3-methylimidazolium tetrafluoroborate.
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Table 2. Synthesis of diarylpyrroles 3a–m from aryl bromides.[a]
Table 4. Synthesis of N-phenyl-2,5-diarylpyrroles 6a–j from arylbromides
and arylchlorides.[a]
3
a
b
c
d
e
f
ArÀBr
Yield 3 [%][b]
6
a
b
c
ArÀX
Yield 6 [%][b]
79
82
67
71
54
44
62
36
38
0
52
40
37
33
15
63
d
e
f
g
h
i
g
31
h
i
22
j
35
j
5[c]
k
l
26
51
[a] Reaction conditions: Pd(OPiv)2 (1 mol%),
5
(1 mmol), CsOPiv
(2.4 equiv.), ArÀX (2.4 equiv.), TBA-Ac (1.5 g), 1408C, 20 h. [b] Yield of iso-
lated products. [c] Addition of 2 mol% of XPhos required.
m
30
sponding aryl bromides. Despite the addition of X-Phos, the re-
action of 5 with 4-chloroanisole afforded product 6j in only
5% yield. In agreement with the findings of Doucet et al.,[14]
the reactions of N-phenylpyrrole (5) proceeded with generally
lower yields than those of N-methylpyrrole (1). This can be ex-
plained by the steric demand of the phenyl group.
[a] Reaction conditions: Pd(OPiv)2 (1 mol%),
1
(1 mmol), CsOPiv
(3.0 equiv.), ArÀBr (3.0 equiv.), TBA-Ac (1.5 g), 1408C, 20 h. [b] Yield of iso-
lated products.
There are several reports related to the formation of palladi-
um nanoparticles (Pd-NP) in ligand-free palladium-catalyzed re-
actions using DMF, DMA, or PEG as solvents.[17] In particular,
this is observed in Heck reactions using ammonium salts as ad-
ditives (Jeffrey conditions).[18] Thus, we examined the mode of
action of our catalyst system. In a typical experiment, we
added an excess of mercury to the reaction after 2 h. The iso-
lated yield of product 3a, using mercury as an additive and
stirring of the reaction mixture for 20 h, reached the range of
yield as observed for the mercury-free reaction which was
quenched after 2 h. This result clearly indicated the participa-
tion of a palladium(0) species in the catalytic cycle.[19] However,
the analysis of the reaction mixture after 20 h, using small-
angle X-ray scattering (SAXS) spectroscopy under standard
conditions, provided no clear evidence of the presence of
nanoparticles. Therefore, we tested preformed Pd-NP as heter-
ogeneous catalysts. Surprisingly, polyvinylpyrrolidone (PVP)-sta-
bilized Pd-NP provided the desired products only if TBA-Ac
was used as the solvent, whereas in other solvents no product
could be detected (Table 5). This is in sharp contrast to the re-
Table 3. Synthesis of diarylpyrroles 3a,b,d,h,i from aryl chlorides.[a]
3
a
b
d
h
i
ArÀCl
Yield 3 [%][b]
46
53
45
18[c]
43
[a] Reaction conditions: Pd(OPiv)2 (1 mol%),
1
(1 mmol) Cs(OPiv)
(3.0 equiv.), ArÀCl (3.0 equiv.), TBA-Ac (1.5 g), 1408C, 20 h. [b] Yield of iso-
lated products. [c] Addition of 2 mol% of XPhos required.
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Table 5. Application of PVP-stabilized Pd-NP for the syntheses of 2,5-di-
phenylpyrrole 3a using Pd-NP as the catalyst.[a]
NP radius [nm] Solvent
Ratio 2/3a[b] Yield 3a [%]
1
2
3
4
5
6
7
8
9
1.1 Æ0.1
1.1 Æ0.1
1.1 Æ0.1
1.1 Æ0.1
1.1 Æ0.1
1.1 Æ0.1
1.1 Æ0.1
3.1 Æ0.3
2.4 Æ0.5
DMA
–
–
–
–
–
–
0
0
0
0
0
propylene carbonate
PEG-400
NMP
dimethyl sulfoxide
xylene
TBA-Ac
0
0.0:1.0
1.0:0.8
1.0:1.1
49[c]
17[b]
23[b]
TBA-Ac
TBA-Ac
[a] Reaction conditions: Pd-NP (1 mol%), KOAc (3 equiv.), 1 (0.5 mmol),
PhÀBr (3 equiv.), solvent, 1408C, 20 h. [b] Determined by 1H NMR-spec-
troscopy of the crude product. [c] Yield of isolated products.
Scheme 1. Proposed reaction mechanism; species such as ArÀPdIIÀX are co-
ordinated by acetate anions and assumed to be negatively charged.[24]
sults obtained by using PdII salts as the catalyst precursors
(Table 1). Furthermore, the reaction involving preformed Pd-NP
proved to be dependent on the size of the nanoparticles.
Small nanoparticles showed higher activities than larger ones,
because of their larger surface. In general, PdII salts gave
higher yields than the employed nanoparticles.
electron-poor aryl chlorides were successfully employed in this
reaction. In addition, we examined the application of palladi-
um nanoparticles as heterogeneous catalysts in this reaction.
Supported by further experimental results, we proposed a pos-
sible mechanism and discussed the crucial role of tetrabuty-
lammonium acetate as a solvent.
In various publications, the groups of Trzeciak and Muzart
showed that Pd(OAc)2 forms anionic palladates in the presence
of ammonium salts.[20] In particular, Trzeciak et al. observed the
reduction of these palladates to palladium(0) in the presence
of acetate anions at elevated temperatures.[21] Moreover, it was
reported that PVP-stabilized Pd-NP are oxidized to related pal-
ladates in the presence of ammonium salts,[22] which explains
the activity of the nanoparticles in the presence of ammonium
acetate. As a consequence of our experimental data and the
results published by Trzeciak and others, we proposed a cata-
lytic cycle based on a Pd0/PdII mechanism (Scheme 1).
Experimental Section
General
All reactions were performed under argon atmosphere. TBA-Ac
was either purchased from Sigma Aldrich or synthesized according
to a known procedure.[25] Unless otherwise cited, all chemicals are
commercially available and were used without further purification.
Column chromatography was performed by using Merck Silicagel
60 (0.043–0.06 mm). NMR data were recorded on Bruker ARX 300
The reaction of the ammonium salt with the employed palla-
dium(II) salt or with the Pd-NP resulted in the formation of
anionic palladate complexes. At elevated temperatures, traces
of tributylamine were formed from the employed ammonium
salt by Hofmann elimination. Tributylamine subsequently re-
duced the palladate to the catalytically active palladium(0) spe-
cies.[23] On the one hand the ammonium salt stabilized the
active palladium(0) species by preventing the formation of
“palladium black”. On the other hand, it increased the solubility
of the organometallic complex. The formed ammonium palla-
date species represented a resting state of the catalytically
active palladium(0) complex.
1
and Bruker ARX 400 spectrometers. 13C and H NMR spectra were
referenced to signals of deuterated solvents and residual protonat-
ed solvents, respectively. IR spectra were recorded on a Nicolet 550
FT-IR spectrometer with ATR sampling technique for solids as well
as liquids. GC–MS was performed on an Agilent HP-5890 instru-
ment with an Agilent HP-5973 Mass Selective Detector (EI) and HP-
5 capillary column using helium carrier gas. ESI-HRMS measure-
ments were performed on an Agilent 1969A TOF mass spectrome-
ter. For High Resolution MS (HRMS) a Finnigan MAT 95 XP was
used. Only the measurements with an average deviation from the
theoretical mass of Æ2 mDa were accounted as correct. Elemental
analyses (EA) were performed with a Leco Mikroanalysator–TrueS-
pec CHNS Micro. Melting points were determined on a Micro-Hot-
Stage GalenTM III Cambridge Instruments. The melting points were
not corrected. SAXS measurements were performed with a Kratky-
type instrument (SAXSess, Anton Paar, Austria) operated at 40 kV
and 50 mA in slit collimation by using a 2D CCD detector (T=
À408C). The 2D scattering pattern was converted into a 1D scat-
tering curve as a function of the magnitude of the scattering
vector with SAXSQuant Software (Anton Paar). A Gçbel mirror was
used to convert the divergent polychromatic X-ray beam into a col-
Conclusions
We developed a catalytic system for the diarylation of N-
methyl- and N-phenylpyrrole. The reactions proceeded under
“ligand-free” conditions. The best yields were obtained if tetra-
butylammonium acetate, an environmentally friendly ionic
liquid, was used as the solvent. A variety of aryl bromides and
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limated line-shaped beam of CuKa radiation (l=0.154 nm). Slit col-
limation of the primary beam was applied in order to increase the
flux and to improve the signal quality. The liquid sample cell con-
sisted of a quartz capillary (internal diameter: 1 mm) stacked in
a metal body with two windows for the X-ray beam. Using this
sample cell, an identical volume of the solution was always irradiat-
ed. Scattering profiles of Pd-NP were obtained by subtraction of
the detector current and the scattering profile of the solvent from
the scattering profiles of the Pd-NP solutions. From the scattering
curves then both the Guinier radius and the volume-weighted size
distribution by indirect Fourier transformation were obtained.
N-Methyl-2,5-di(p-tolyl)pyrrole (3c): According to the general pro-
cedure, 3c was isolated as a light yellow solid by using ArÀBr
(3.0 mmol, 177 mg, 67%) with CsOPiv (3.0 mmol) as the base, m.p.
1
1618C. H NMR (300 MHz, CDCl3): d=2.30 (s, 6H, CH3), 3.49 (s, 3H,
3
CH3), 6.19 (s, 2H, CH), 7.13 (d, 4H, J=7.9 Hz, CH), 7.25–7.29 ppm
(m, 4H, CH). 13C NMR (75 MHz, CDCl3): d=21.2 (CH3), 34.2 (CH3),
108.2, 128.6, 129.1 (CH), 130.7, 136.5, 136.6 ppm (C). IR (ATR): n˜ =
3018 (w), 2915 (w), 2853 (w), 1914 (w), 1446 (m), 1326 (m), 1113
(m), 820 (s), 766 (s), 510 (s), 487 cmÀ1 (m). MS (EI, 70 eV): m/z (%)=
261 (M+, 100), 260 (14), 246 (10), 130 (5), 128 (5). HRMS (EI, 70 eV):
calcd. for C19H19N: 261.15120; found: 261.15120. Elemental analysis
calcd. for C19H19N (261.35): C, 87.31; H, 7.33; N, 5.36; found: C,
87.41; H, 7.30; N, 5.08.
Preparation of Pd/PVP nanoparticles
N-Methyl-2,5-di(4-nitrophenyl)pyrrole (3d): According to the gener-
al procedure, 3d was isolated as an orange-red solid using ArÀBr
or ArÀCl (3.0 mmol) with CsOPiv (3.0 mmol) as the base (ArÀBr:
The following values are for a 20 mL approach with a Pd concen-
tration of 20 mm. Na2PdCl4 (117.7 mg, 0.4 mmol) and PVP K-30
(133.4 mg, 1.2 mmol of repeating unit) were dissolved in ethylene
glycol (18 mL). The solution was stirred at 1008C under argon at-
mosphere. Subsequently, an ethylene glycol solution of sodium hy-
droxide (2 mL, 0.5m) was rapidly added. The color changed within
seconds from orange over yellow to dark brown. After stirring for
3 h at 1008C, the mixture was cooled to RT.
1
232 mg, 71%; ArÀCl: 144 mg, 45%), m.p. 1938C. H NMR (300 MHz,
CDCl3): d=3.70 (s, 3H, CH3), 6.52 (s, 2H, CH), 7.59–7.63 (m, 4H, CH),
8.26–8.31 ppm (m, 4H, CH). 13C NMR (75 MHz, CDCl3): d=35.1
(CH3), 112.0 (CH), 124.1, 128.5, (CH), 137.0, 138.9, 146.4 ppm (C). IR
(ATR): n˜ =3096 (w), 2929 (w), 1936 (w), 1589 (s), 1509 (s), 1332 (s),
1104 (m), 850 (s), 752 (s), 695 (m), 496 cmÀ1 (m). MS (EI, 70 eV): m/z
(%)=323 (M+, 100), 293 (10), 277 (9), 247 (10), 231 (22), 230 (17).
HRMS (EI, 70 eV): calcd. for C17H13N3O4: 323.09006; found:
323.09005.
Syntheses of 2,5-diarylpyrroles
Pd(OPiv)2 (0.01 mmol, 1.0 mol%), N-methyl- or N-phenylpyrrole (1
or 5, 1.0 mmol), the appropriate amount of aryl bromide or aryl
chloride, and CsOPiv were placed in an argon-flushed glass pres-
sure tube, followed by tetrabutylammonium acetate (1.5 g). The
pressure tube was closed with a Teflon cap and the reaction mix-
ture was stirred at 1408C for 20 h. Afterwards, the mixture was
cooled to RT and diluted with distilled water and ethyl acetate. The
water layer was extracted 2 times with ethyl acetate and the com-
bined organic layers were washed with brine. The combined or-
ganic layers were dried with sodium sulfate and filtered. The sol-
vent of the filtrate was evaporated and the product was purified
by column chromatography.
N-Methyl-2,5-di(4-(N,N-dimethylamino)phenyl)pyrrole (3e): Accord-
ing to the general procedure, 3e was isolated as a yellow solid
using ArÀBr (3.0 mmol, 174 mg, 54%) with CsOPiv (3.0 mmol) as
the base, m.p. 189–1908C. 1H NMR (300 MHz, CDCl3): d=2.97 (s,
12H, NMe2), 3.54 (s, 3H, CH3), 6.18 (s, 2H, CH), 6.74–6.79 (m, 4H,
CH), 7.30–7.35 ppm (m, 4H, CH). 13C NMR (75 MHz, CDCl3): d=33.9
(CH3), 40.6 (NMe2), 107.1, 112.3 (CH), 122.2 (C), 129.7 (CH), 136.2,
149.4 ppm (C). IR (ATR): n˜ =2954 (m), 2927 (m), 2870 (m), 2792 (m),
1903 (w), 1610 (s), 1506 (s), 1442 (s), 1341 (s), 1226 (m), 1163 (s),
1060 (m), 945 (m), 820 (s), 756 (s), 532 cmÀ1 (m). MS (EI, 70 eV): m/z
(%)=319 (M+, 100), 304 (33), 303 (10), 288 (10), 160 (12), 152 (11).
HRMS (EI, 70 eV): calcd. for C21H25N3: 319.20430; found: 319.20429.
N-Methyl-2,5-diphenylpyrrole (3a): According to the general proce-
dure, 3a was isolated as a light yellow solid by using ArÀBr or ArÀ
Cl (3.0 mmol) with CsOPiv (3.0 mmol) as the base (ArÀBr: 185 mg,
79%; ArÀCl: 107 mg, 46%), m.p. 165–1678C. 1H NMR (300 MHz,
CDCl3): d=3.61 (s, 3H, CH3), 6.32 (s, 2H, CH), 7.27–7.47 ppm (m,
10H, CH). 13C NMR (75 MHz, CDCl3): d=34.3 (CH3), 108.7, 126.8,
128.4, 128.7 (CH), 133.5, 136.9 ppm (C). IR (ATR): n˜ =3058 (w), 2918
(w), 2850 (w), 1597 (w), 1464 (m), 1331 (w), 1076 (m), 918 (w), 750
(s), 697 (s), 506 cmÀ1 (m). MS (EI, 70 eV): m/z (%)=233 (M+, 100),
232 (19), 219 (11), 217 (14), 115 (9). HRMS (EI, 70 eV): calcd. for
C17H15N: 233.11990; found: 233.11997.
N-Methyl-2,5-di(4-chlorophenyl)pyrrole (3 f): According to the gen-
eral procedure, 3 f was isolated as a yellow solid by using ArÀBr
(3.0 mmol, 135 mg, 44%) with CsOPiv (3.0 mmol) as the base, m.p.
1
1748C. H NMR (300 MHz, CDCl3): d=3.56 (s, 3H, CH3), 6.30 (s, 2H,
CH), 7.38 ppm (s, 8H, CH). 13C NMR (75 MHz, CDCl3): d=34.2 (CH3),
109.1, 128.7, 129.8 (CH), 131.7, 132.9, 136.0 ppm (C). IR (ATR): n˜ =
3915 (w), 1909 (w), 1672 (w), 1448 (m), 1405 (w), 1336 (w), 1092
(m), 1007 (m), 834 (s), 758 (s), 714 (m), 513 (s), 480 cmÀ1 (m). MS
(EI, 70 eV): m/z (%)=301 (M+, 100), 303 (64), 304 (13), 305 (11), 300
(9), 286 (11), 251 (7), 151 (9). HRMS (EI, 70 eV): calcd. for C17H13Cl2N:
301.04196; found: 301.04203. Elemental analysis calcd. for
C17H13Cl2N (302.18): C, 67.57; H, 4.34; N, 4.63; found: C, 67.50; H,
4.45; N, 4.34.
N-Methyl-2,5-di(4-trifluoromethylphenyl)pyrrole (3b): According to
the general procedure, 3b was isolated as a white solid by using
ArÀBr or ArÀCl (3.0 mmol) with CsOPiv (3.0 mmol) as the base (ArÀ
Br: 306 mg, 82%; ArÀCl: 195 mg, 53%), m.p. 1558C. 1H NMR
(300 MHz, CDCl3): d=3.66 (s, 3H, CH3), 6.45 (s, 2H, CH), 7.61 (d, 4H,
N-Methyl-2,5-di(4-fluorophenyl)pyrrole (3g): According to the gen-
eral procedure, 3g was isolated as a white solid by using ArÀBr
(3 mmol, 167 mg, 62%) with CsOPiv (3 mmol) as the base, m.p.
3
3J=8.2 Hz, CH), 7.72 ppm (d, 4H, J=8.2 Hz, CH). 13C NMR (75 MHz,
1
194–1968C. H NMR (300 MHz, CDCl3): d=3.53 (s, 3H, CH3), 6.25 (s,
1
CDCl3): d=34.5 (CH3), 110.3 (CH), 124.3 (q, J=272.3 Hz, CF3), 125.5
2H, CH), 7.06–7.14 (m, 4H, CH), 7.37–7.43 ppm (m, 4H, CH).
13C NMR (75 MHz, CDCl3): d=34.0 (CH3), 108.6 (CH), 115.4 (d, 2J=
21.4 Hz, CH), 129.6 (d, 4J=3.3 Hz, C), 130.4 (d, 3J=8.4 Hz, CH),
135.7 (C), 162.0 ppm (d, 2J=246.6 Hz, CF). IR (ATR): n˜ =2950 (w),
1902 (w), 1665 (w), 1600 (w), 1548 (w), 1493 (s), 1329 (w), 1222 (s),
1156 (m), 1098 (m), 837 (s), 812 (s), 765 (s), 636 (m), 523 (s),
429 cmÀ1 (w). MS (EI, 70 eV): m/z (%)=269 (M+, 100), 268 (17), 254
(q, 3J=3.9 Hz, CH), 128.6 (CH), 128.9 (q, 2J=32.2 Hz, C), 136.5,
136.6 ppm (C). IR (ATR): n˜ =1930 (w), 1609 (m), 1455 (w), 1320 (s),
1107 (s), 1067 (s), 750 (s), 1013 (m), 845 (s), 764 (m), 598 (m),
505 cmÀ1 (m). MS (EI, 70 eV): m/z (%)=369 (M+, 100), 368 (15), 350
(9), 285 (4), 259 (2), 185 (3). HRMS (EI, 70 eV): calcd. for C19H13F6N:
369.09467; found: 369.09442. EA: calcd. for C19H13F6N (369.29): C,
61.79; H, 3.55; N, 3.79; found: C, 61.94; H, 3.57; N, 3.64.
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(19), 253 (13), 227 (6), 133 (8). HRMS (EI, 70 eV): calcd. for
C17H13F2N: 269.10106; found: 269.10098.
766 (s), 699 cmÀ1 (s). MS (EI, 70 eV): m/z (%)=369 (M+, 100), 350
(8), 285 (3), 259 (3), 202 (2), 185 (5). HRMS (ESI): calcd for C19H14F6N
([M+H]+): 370.1025; found: 370.10242. EA: calcd. for C19H13F6N
(369.30): C, 61.79; H, 3.55; N, 3.79; found C, 61.48; H, 3.641; N,
3.671.
N-Methyl-2,5-di(4-methoxyphenyl)pyrrole (3h): According to the
general procedure, 3h was isolated as a yellow solid using ArÀBr
or ArÀCl (3.0 mmol) with CsOPiv (3.0 mmol) as the base and the
XPhos ligand (2 mol%) (ArÀBr: 107 mg, 36%; ArÀCl: 52 mg, 18%),
1,2,5-Triphenyl-1H-pyrrole (6a): According to the general proce-
dure, 6a was isolated as a light yellow solid by using ArÀBr
(2.4 mmol, 154 mg, 52%) with CsOPiv (2.4 mmol) as the base, m.p.
231–2328C. 1H NMR (300 MHz, CDCl3): d=6.47 (s, 2H, CH), 7.00–
7.06 (m, 6H, CH), 7.11–7.17 (m, 6H, CH), 7.20–7.23 ppm (m, 3H,
CH). 13C NMR (75 MHz, CDCl3): d=109.9 (CH), 126.2 (CH), 127.2
(CH), 127.8 (CH), 128.7 (2 x CH), 128.8 (CH), 133.2 (C), 135.8 (C),
138.9 ppm (C). IR (ATR): n˜ =3052 (w), 2916 (w), 1596 (m), 1494 (m),
1481 (m), 1395 (w), 1334 (w), 774 (s), 692 (s), 595 cmÀ1 (m). MS (EI,
70 eV): m/z (%)=295 (M+, 100), 217 (10), 191 (25), 165 (11), 139 (7),
115 (8), 77 (19), 51 (13). HRMS (EI, 70 eV): calcd. for C22H17N:
295.13555; found: 295.13543.
1
m.p. 1568C. H NMR (300 MHz, CDCl3): d=3.54 (s, 3H, CH3), 3.84 (s,
6H, OCH3), 6.22 (s, 2H, CH), 6.93–6.97 (m, 4H, CH), 7.35–7.40 ppm
(m, 4H, CH). 13C NMR (75 MHz, CDCl3): d=33.9 (CH3), 55.3 (OCH3),
107.7, 113.8 (CH), 126.4 (C), 130.0 (CH), 136.1, 158.7 ppm (C). IR
(ATR): n˜ =3013 (w), 2954 (w), 2932 (w), 2836 (w), 1904 (w), 1677
(w), 1606 (m), 1572 (m), 1463 (m), 1242 (s), 1174 (s), 1112 (m), 1026
(s), 833 (s), 757 (s), 632 (m), 531 cmÀ1 (m). MS (EI, 70 eV): m/z (%)=
293 (M+, 100), 279 (15), 278 (75), 147 (11). HRMS (EI, 70 eV): calcd.
for C19H19NO2: 293.14103; found: 293.14116.
N-Methyl-2,5-di(4-cyanophenyl)pyrrole (3i): According to the gener-
al procedure, 3i was isolated as a yellow solid by using ArÀBr or
ArÀCl (3.0 mmol) with CsOPiv (3.0 mmol) as the base (ArÀBr:
109 mg, 38%; ArÀCl: 121 mg, 43%), m.p. 195–1978C. 1H NMR
(300 MHz, CDCl3): d=3.63 (s, 3H, CH3), 6.43 (s, 2H, CH), 7.52–7.56
(m, 4H, CH) 7.67–7.71 ppm (m, 4H, CH). 13C NMR (75 MHz, CDCl3):
d=34.9 (CH3), 110.2 (CH), 111.3, 118.8 (C), 128.6, 132.4 (CH), 136.9,
137.1 ppm (C). IR (ATR): n˜ =2960 (w), 2873 (w), 2224 (m), 1689 (w),
1603 (m), 1445 (m), 1246 (m), 840 (s), 768 (s), 730 (m), 546 cmÀ1 (s).
MS (EI, 70 eV): m/z (%)=283 (M+, 100), 282 (16), 268 (7), 267 (9).
HRMS (EI, 70 eV): calcd. for C19H13N3: 283.11040; found: 283.11005.
N-Phenyl-2,5-bis(4-(trifluoromethyl)phenyl)-1H-pyrrole (6b): Accord-
ing to the general procedure, 6b as a light yellow solid by using
ArÀBr or ArÀCl (2.4 mmol) with CsOPiv (2.4 mmol) as the base (ArÀ
Br: 223 mg, 52%; ArÀCl: 95 mg, 22%). m.p. 187–1898C. 1H NMR
(300 MHz, CDCl3): d=6.56 (s, 2H, CH), 7.01–7.04 (m, 2H, CH), 7.11–
7.14 (m, 4H, CH), 7.29–7.32 (m, 3H, CH), 7.39–7.42 ppm (m, 4H,
1
CH). 13C NMR (75 MHz, CDCl3): d=111.4 (CH), 124.1 (q, JCÀF
=
3
2
271.9 Hz, CF3), 124.9 (q, JCÀF =3.9 Hz, CH), 128.0 (CH), 128.2 (q, JCÀ
F =32.2 Hz, C), 128.4 (CH), 128.7 (CH), 129.3 (CH), 135.1 (C), 136.3
(C), 138.2 ppm (C). IR (ATR): n˜ =1610 (w), 1497 (w), 1421 (m), 1347
(s), 1323 (s), 1162 (s), 1115 (s), 901 (m), 774 (s), 697 cmÀ1 (s). MS (EI,
70 eV): m/z (%)=431 (M+, 100), 412 (9), 259 (8), 191 (10), 146 (9),
77 (10). HRMS (EI, 70 eV): calcd. for C24H15F6N: 431.11032; found:
431.10984.
N-Methyl-2,5-bis(2-nitrophenyl)pyrrole (3k): According to the gen-
eral procedure, 3k was isolated as a highly viscous oil by using
ArÀBr (3.0 mmol, 85 mg, 26%) with CsOPiv (3.0 mmol) as the base.
1H NMR (300 MHz, CDCl3): d=3.20 (s, 3H, CH3), 6.21 (s, 2H, CH),
7.53–7.56 (m, 4H, CH) 7.63–7.66 (m, 2H, CH), 7.95–7.98 ppm (m,
2H, CH). 13C NMR (75 MHz, CDCl3): d=32.4 (CH3), 109.4 (CH), 124.2
(CH), 127.8 (C), 129.0 (CH), 129.2, 130.3 (C), 132.5, 133.7 ppm (CH).
IR (ATR): n˜ =2923 (w), 1607 (m), 1519 (s), 1341 (s), 1238 (m), 1085
(w), 852 (m), 750 (s), 511 cmÀ1 (m). MS (EI, 70 eV): m/z (%)=323
(M+, 62), 234 (21), 218 (40), 202 (22), 189 (19), 163 (32), 147 (31).
HRMS (ESI): calcd for C17H14N3O4 ([M+H]+): 324.09788; found:
324.09778.
N-Phenyl-2,5-di(p-tolyl)-1H-pyrrole (6c): According to the general
procedure, 6c was isolated as a light yellow solid by using ArÀBr
(2.4 mmol, 119 mg, 37%) with CsOPiv (2.4 mmol) as a base, m.p.
1
215–2178C. H NMR (300 MHz, CDCl3): d=2.27 (s, 6H, CH3), 6.43 (s,
2H, CH), 6.93–6.98 (m, 8H, CH), 7.02–7.04 (m, 2H, CH), 7.22–
7.24 ppm (m, 3H, CH). 13C NMR (75 MHz, CDCl3): d=21.0 (CH3),
109.4 (CH), 127.0 (CH), 128.5 (2ꢁCH), 128.6 (CH), 128.9 (CH), 130.4
(C), 135.6 (C), 135.7 (C), 139.1 ppm (C). IR (ATR): n˜ =2917 (w), 1494
(s), 1332 (m), 814 (s), 768 (s), 693 (s), 579 (s), 521 (s), 401 cmÀ1 (s).
MS (EI, 70 eV): m/z (%)=323 (M+, 100), 205 (8), 191 (9), 77 (13), 51
(6). HRMS (EI, 70 eV): calcd. for C24H21N: 323.16685; found:
323.16660.
N-Methyl-2,5-di(o-tolyl)pyrrole (3l): According to the general proce-
dure, 3l was isolated as a viscous oil by using ArÀBr (3.0 mmol,
133 mg, 51%) with CsOPiv (3.0 mmol) as the base. 1H NMR
(300 MHz, CDCl3): d=2.34 (s, 6H, CH3), 3.17 (s, 3H, CH3), 6.23 (s,
2H, CH), 7.28–7.42 ppm (m, 8H, CH). 13C NMR (75 MHz, CDCl3): d=
20.0 (CH3), 31.8 (CH3), 107.7, 125.5, 127.9, 129.9, 131.3 (CH), 133.5,
133.7, 138.1 ppm (C). IR (ATR): n˜ =2920 (w), 1602 (w), 1438 (m),
1379 (m), 1315 (m), 1116 (w), 1032 (m), 944 (w), 754 (s), 729 (s),
451 cmÀ1 (m). MS (EI, 70 eV): m/z (%)=261 (M+, 100), 246 (18), 230
(6), 215 (6), 202 (6), 170 (7). HRMS (ESI): calcd for C19H20N ([M+H]+):
262.15903; found: 262.15892. Elemental analysis calcd. for C19H19N
(261.36): C, 87.31; H, 7.33; N, 5.36; found: C, 87.43; H, 7.70; N,
5.136.
N-Phenyl-2,5-bis(4-nitrophenyl)-1H-pyrrole (6d): According to the
general procedure, 6d was isolated as an orange solid by using
ArÀBr or ArÀCl (2.4 mmol) with CsOPiv (2.4 mmol) as the base (ArÀ
Br: 180 mg, 47%; ArÀCl: 135 mg, 35%), m.p. 253–2558C. 1H NMR
(300 MHz, CDCl3): d=6.67 (s, 2H, CH), 7.04–7.07 (m, 2H, CH), 7.12–
7.17 (m, 4H, CH), 7.30–7.40 (m, 3H, CH), 7.99–8.04 ppm (m, 4H,
CH). 13C NMR (75 MHz, CDCl3): d=112.9 (CH), 123.4 (CH), 128.4
(CH), 128.5 (CH), 128.7 (CH), 129.7 (CH), 135.2 (C), 137.7 (C), 138.8
(C), 145.9 ppm (C). IR (ATR): n˜ =1585 (s), 1501 (s), 1320 (s), 1105 (s),
850 (s), 772 (s), 747 (s), 697 (s), 521 cmÀ1 (m). MS (EI, 70 eV): m/z
(%)=385 (M+, 100), 339 (7), 291 (24), 278 (8), 265 (6), 189 (7), 146
(10), 30 (6). HRMS (EI, 70 eV): calcd. for C22H15N3O4: 385.10571;
found: 385.10543. EA: calcd. for C22H15N3O4 (385.37): C, 68.57; H,
3.92; N, 10.90; found: C, 68.37; H, 3.80; N, 11.03.
N-Methyl-2,5-bis(3-(trifluoromethyl)phenyl)pyrrole (3m): According
to the general procedure, 3m was isolated as a light yellow oil
using ArÀBr (3.0 mmol, 109 mg, 30%) with CsOPiv (3.0 mmol) as
the base. 1H NMR (300 MHz, CDCl3): d=3.64 (s, 3H, CH3), 6.41 (s,
2H, CH), 7.54–7.63 (m, 4H, CH), 7.66–7.69 (m, 2H, CH), 7.75–
7.75 ppm (m, 2H, CH). 13C NMR (75 MHz, CDCl3): d=34.3 (CH3),
109.9 (CH), 123.6 (q, 3J=3.6 Hz, CH), 124.1 (q, 1J=273.4 Hz, CF3),
N-Phenyl-2,5-bis(4-methoxyphenyl)-1H-pyrrole (6e): According to
the general procedure, 6e was isolated as a yellow solid by using
ArÀBr or ArÀCl (2.4 mmol) with CsOPiv (2.4 mmol) as the base (ArÀ
Br: 53 mg, 15%; ArÀCl: 18 mg, 5%), m.p. 149–1518C. 1H NMR
3
2
125.3 (q, J=3.8 Hz, CH), 129.0 (CH), 131.0 (q, J=32.2 Hz, C), 131.7
(CH), 133.9, 136.1 ppm (C). IR (ATR): n˜ =2924 (w), 1588 (w), 1459
(m), 1325 (s), 1238 (m), 1160 (s), 1116 (s), 1047 (s), 902 (m), 801 (m),
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son, M. J. Turner, E. Wagner, J. Wu, P. Zhou, J. Bard, J. Med. Chem. 2006,
49, 6158–6161; e) G. Xiao, A. Kumar, K. Li, C. T. Rigl, M. Bajic, T. M. Davis,
D. W. Boykin, W. D. Wilson, Bioorg. Med. Chem. 2001, 9, 1097–1113;
f) B. A. Thaher, P. Koch, V. Schattel, S. Laufer, J. Med. Chem. 2009, 52,
2613–2617; g) S. Hibi, K. Tagami, K. Kikuchi, H. Yoshimura, K. Tai, T. Hida,
N. Tokuhara, T. Yamauchi, M. Nagai, Bioorg. Med. Chem. Lett. Bioorg.
Med. 2000, 10, 623–625; h) B. Portevin, C. Tordjman, P. Pastoureau, J.
Bonnet, G. De Nanteuil, J. Med. Chem. 2000, 43, 4582–4593.
(300 MHz, CDCl3): d=3.73 (s, 6H, OCH3), 6.37 (s, 2H, CH), 6.67–6.72
(m, 4H, CH), 6.94–7.02 (m, 6H, CH), 7.20–7.23 ppm (m, 3H, CH).
13C NMR (75 MHz, CDCl3): d=55.1 (OCH3), 108.9 (CH), 113.3 (CH),
125.9 (C), 127.0 (CH), 128.6 (CH), 128.9 (CH), 129.9 (CH), 135.1 (C),
139.0 (C), 158.0 ppm (C). IR (ATR): n˜ =2927 (w), 2831 (w), 1496 (s),
1382 (m), 1281 (m), 1239 (s), 1173 (s), 1025 (s), 824 (s), 751 (s), 695
(s), 583 (s), 523 cmÀ1 (s). MS (EI, 70 eV): m/z (%)=355 (M+, 100),
340 (56), 296 (6), 268 (10), 178 (9), 77 (10). HRMS (EI, 70 eV): calcd.
for C24H21NO2: 355.15668; found: 355.15638.
[3] a) X. Wang, B. S. Lane, D. Sames, J. Am. Chem. Soc. 2005, 127, 4996–
4997; b) T. T. Dang, R. Ahmad, T. T. Dang, H. Reinke, P. Langer, Tetrahe-
dron Lett. 2008, 49, 1698; c) S.-M. T. Toguem, O. Fatunsin, A. Villinger, P.
Langer, Tetrahedron Lett. 2011, 52, 3732; d) J. Wen, S. Qin, L.-F. Ma, L.
Dong, J. Zhang, S.-S. Liu, Y.-S. Duan, S.-Y. Chen, C.-W. Hu, Y.-Q. Yu, Org.
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eilhavoup, G. Betrand, Angew. Chem. 2008, 120, 5302–5306; Angew.
Chem. Int. Ed. 2008, 47, 5224–5228; f) O. Vakuliuk, B. Koszarna, D. T.
Gryko, Adv. Synth. Catal. 2011, 353, 925–930; g) R. D. Rieth, N. P.
Mankad, E. Calimano, J. P. Sadighi, Org. Lett. 2004, 6, 3981–3983.
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Chem. Int. Ed. 2002, 41, 4176–4211; b) R. J. Lundgren, M. Stradiotto,
Chem. Eur. J. 2012, 18, 9758–9769; A. Suzuki, J. Organomet. Chem.
1999, 576, 147–168; T. N. Mitchell, Synthesis 1992, 803–815.
[5] a) N. Nakamura, Y. Tajima, K. Sakai, Heterocycles 1982, 17, 235–245;
b) D. E. Ames, D. Bull, Tetrahedron 1982, 38, 383; c) B. J. Stokes, T. G.
Driver, Eur. J. Org. Chem. 2011, 4071–4088; d) R. Jazzar, J. Hitce, A. Re-
naudat, J. Sofack-Kreutzer, O. Baudoin, Chem. Eur. J. 2010, 16, 2654–
2672; e) T. W. Lyons, M. S. Sanford, Chem. Rev. 2010, 110, 1147–1169;
f) J. A. Labinger, J. E. Bercaw, Nature 2002, 417, 507–514; g) S. H. Cho,
J. Y. Kim, J. Kwak, S. Chang, Chem. Soc. Rev. 2011, 40, 5068–5083; h) J.
Yamaguchi, A. D. Yamaguchi, K. Itami, Angew. Chem. 2012, 124, 9092–
9142; Angew. Chem. Int. Ed. 2012, 51, 8960–9009.
N-Phenyl-2,5-bis(4-cyanophenyl)-1H-pyrrole (6 f): According to the
general procedure, 6 f was isolated as a white solid using ArÀBr
(2.4 mmol, 217 mg, 63%) with CsOPiv (2.4 mmol) as the base, m.p.
289–2918C. 1H NMR (300 MHz, CDCl3): d=6.59 (s, 2H, CH), 7.00–
7.03 (m, 2H, CH), 7.06–7.10 (m, 4H, CH), 7.28–7.37 (m, 3H, CH),
7.40–7.44 ppm (m, 4H, CH). 13C NMR (75 MHz, CDCl3): d=109.7 (C),
112.2 (CH), 118.8 (C), 128.4 (CH), 128.5 (2ꢁCH), 129.5, 131.8 (CH),
135.1, 136.9, 137.8 ppm (C). IR (ATR): n˜ =2221 (s), 1598 (s), 1532 (s),
1490 (s), 1428 (m), 1344 (s), 1178 (m), 840 (s), 778 (s), 697 (s),
560 cmÀ1 (s). MS (EI, 70 eV): m/z (%)=345 (M+, 100), 242 (6), 216
(13), 190 (8), 77 (16), 51 (12). HRMS (EI, 70 eV): calcd. for C24H15N3:
345.12605; found: 345.12565.
N-Phenyl-2,5-bis(3-(trifluoromethyl)phenyl)-1H-pyrrole (6g): Accord-
ing to the general procedure, 6g was isolated as a white solid by
using ArÀBr (2.4 mmol, 185 mg, 43%) with CsOPiv (2.4 mmol) as
the base, m.p. 201–2038C. 1H NMR (300 MHz, CDCl3): d=6.55 (s,
2H, CH), 7.00–7.03 (m, 2H, CH), 7.18–7.21 (m, 2H, CH), 7.26–7.30
(m, 7H, CH), 7.36–7.39 ppm (m, 2H, CH). 13C NMR (75 MHz, CDCl3):
3
d=110.8 (CH), 122.9 (q, JCÀF =3.8 Hz, CH), 123.8 (q,1JCÀF =272.3 Hz,
[6] C. Fischmeister, H. Doucet, Green Chem. 2011, 13, 741–753.
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5196–5217; Angew. Chem. Int. Ed. 2009, 48, 5094–5115; b) I. V. Seregin,
V. Gevorgyan, Chem. Soc. Rev. 2007, 36, 1173–1193.
3
CF3), 125.2 (q, JCÀF =3.8 Hz, CH), 128.0 (CH), 128.3 (CH), 128.7 (CH),
2
129.2 (CH), 130.3 (q, JCÀF =32.2 Hz, C), 131.5 (CH), 133.5 (C), 134.8
(C), 138.0 ppm (C). IR (ATR): n˜ =1611 (m), 1498 (m), 1433 (m), 1318
(s), 1168 (s), 1104 (s), 1061 (s), 1013 (s), 837 (s), 778 (s), 703 (s), 597
(s), 493 cmÀ1 (m). MS (EI, 70 eV): m/z (%)=431 (M+, 100), 412 (7),
259 (10), 191 (9), 77 (12), 51 (6). HRMS (EI, 70 eV): calcd. for
C24H15F6N: 431.11032; found: 431.10999. Elemental analysis calcd.
for C24H15F6N (431.37): C, 66.82; H, 3.50; N, 3.25; found: C, 67.01; H,
3.46; N, 3.28.
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Pozgan, J. Roger, H. Doucet, ChemSusChem 2008, 1, 404–407; c) J.
Roger, F. Pozgan, H. Doucet, Green Chem. 2009, 11, 425–432; d) J. J.
Dong, H. Doucet, Eur. J. Org. Chem. 2010, 611–615; e) L. Chen, C. Bru-
neau, P. H. Dixneuf, H. Doucet, Green Chem. 2012, 14, 1111–1124.
[9] a) B. Liꢂgault, I. Petrov, S. I. Gorelsky, K. Fagnou, J. Org. Chem. 2010, 75,
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Acknowledgements
Financial support by the Volkswagenstiftung (Az86223) and by
the BMBF (REMEDIS project, Grant No. 03IS2081A) is gratefully
acknowledged.
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