Palladium C-N bond formation catalysed by air-stable robust polydentate ferrocenylphosphines: A comparative study for the efficient and selective coupling of aniline derivatives to dichloroarene

Article abstract of DOI:10.1039/c4cy00151f

The arylation of aniline derivatives with dichloroarenes under a low palladium content (below the currently used 5 to 10 mol%) was studied using nine different ferrocenylphosphine ligands, including the easily accessible 1,1′-bis(diphenylphosphino)ferrocene, DPPF. The electron-enriched air-stable tridentate ferrocenylpolyphosphine 1,2-bis(diphenylphosphino)- 1′-(diisopropylphosphino)-4-tert-butylferrocene, L5, employed in 2 mol% in combination with 1 mol% [PdCl(η³-C₃H ₅)]₂ allows an efficient and selective coupling, while such demanding substrates currently induce chloroarene homocoupling and/or dehalogenation processes. The scope and limitation of the optimized system are explored, with a focus on electron-poor fluoroanilines (deactivated nucleophiles) and electron-rich methylated and methoxylated dichlorobenzenes (deactivated electrophiles). The Royal Society of Chemistry 2014.

Full text of DOI:10.1039/c4cy00151f

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Palladium C–N bond formation catalysed by
air-stable robust polydentate ferrocenylphosphines:
a comparative study for the efficient and selective
coupling of aniline derivatives to dichloroarene†
Cite this: Catal. Sci. Technol., 2014,
4, 2072
a
a
a
ab
*
Mélanie Platon, Julien Roger, Sylviane Royer and Jean-Cyrille Hierso
The arylation of aniline derivatives with dichloroarenes under a low palladium content (below the
currently used 5 to 10 mol%) was studied using nine different ferrocenylphosphine ligands, including the
easily accessible 1,1′-bis(diphenylphosphino)ferrocene, DPPF. The electron-enriched air-stable tridentate
ferrocenylpolyphosphine
1,2-bis(diphenylphosphino)-1′-(diisopropylphosphino)-4-tert-butylferrocene,
L5, employed in 2 mol% in combination with 1 mol% [PdCl(η3-C3H5)]2 allows an efficient and selective
coupling, while such demanding substrates currently induce chloroarene homocoupling and/or
dehalogenation processes. The scope and limitation of the optimized system are explored, with a focus
on electron-poor fluoroanilines (deactivated nucleophiles) and electron-rich methylated and methoxy-
lated dichlorobenzenes (deactivated electrophiles).
Received 6th February 2014,
Accepted 19th March 2014
DOI: 10.1039/c4cy00151f
www.rsc.org/catalysis
minimizing the amount of palladium (for cost and environ-
mental reasons) and providing catalytic systems in which
Introduction
The palladium-catalysed coupling of aniline derivatives with
haloarenes is an attractive first step to intermolecularly form
carbazole derivatives from cheap and easily available
substrates (Scheme 1).1,2 Carbazoles are fused heterocyclic
aromatic molecules displaying powerful applications in medi-
cine3–6 and materials science.7–9 The current approaches
to this sp2 C–N bond formation, which is especially challeng-
ing when bromo- and chloroarenes are employed, are based
on the use of electron-rich and air-sensitive monodentate
phosphine oxide formation does not hamper the general
expediency on a large scale. The use of air-stable robust
ferrocenylphosphines as ligands in palladium-catalysed
C–C bond formation has led to highly efficient catalytic
systems in which the amount of palladium and ligands was
decreased by several orders of magnitude for cross-coupling
reactions using demanding organic halides.15–17 The effi-
ciency of ferrocenylpolyphosphines at low catalyst loading
was also been recently confirmed in the palladium-catalysed
C–O bond coupling for heteroarylether formation from
functionalized phenols and chloroheteroarenes.18 We envision
that ferrocenylphosphine ligands (Fig. 1) might be useful
in the coupling of aniline derivatives with bromo- and
chloroarenes at lower catalyst loading, especially concerning
polyfunctionalized substrates with functionality at the
ortho-position.17
10,11
12
phosphines such as P(t-Bu)3
and PCy3 in catalytic sys-
tems in which 5 to 10 mol% of palladium and ligands are
needed. The use of norbornene (25 mol%) in the Pd oxidative
coupling of protected bromoanilines and iodoarenes13 and
the employment of the biphenyl monophosphine X-Phos
(15 mol%) for the coupling of aryl triflates have also been
reported.14 In these studies, the C–N bond formation step
has not been studied by itself but in a cascade or in one-pot
processes. While acknowledging the valuable work in this
area, we believe that progress in catalysis science and tech-
nology, in order to reach industrial application, also lies in
We report herein the higher efficiency in the C–N coupling
of polyfunctionalized dichloroarenes with anilines of an
air-stable tridentate ferrocenylpolyphosphine suitable under
a Université de Bourgogne, CNRS, UMR 6302, ICMUB, Institut de Chimie
Moléculaire de l'Université de Bourgogne, 9 avenue Alain Savary, 21078 Dijon,
France. E-mail: jean-cyrille.hierso@u-bourgogne.fr; Fax: +33 380 393 682;
Tel: +33 380 396 107
b Institut Universitaire de France (IUF), France
† Electronic supplementary information (ESI) available. See DOI: 10.1039/
c4cy00151f
Scheme 1 General pathway to carbazoles via Pd-catalysed coupling
of anilines to haloarenes.
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15–20% yield, was observed upon addition of 2 mol% DPPF
to the palladium sources selected (entries 4 and 5).
Further screening of the catalytic conditions indicated that
using sodium carbonate as base was completely inefficient
(entries 6 and 7). The use of DMF while increasing the
conversion of 1a also favoured the dehalogenation of 3a to
diphenylamine (entry 8). Increasing the loading of palladium
and the ligand to 10 mol% only favoured the homocoupling
reaction, leading to 2,2′-dichlorobiphenyl followed by
dehalogenation to 1-chloro-2-phenylbenzene and biphenyl
(entry 9); these side reactions were also observed upon
increasing the temperature to toluene reflux (entry 10). Thus,
DPPF was found rather limited for efficient and selective
coupling of 1a with 2a.
On the basis of the most selective conditions identified
for DPPF (Table 1, entry 4) we compared the performance of
a set of bidentate, tridentate and tetradentate ferrocenyl-
phosphines L2–L9 (Fig. 1). The results of the screening exper-
iments are reported in Table 2.
Fig. 1 Polydentate ferrocenylphosphines probed as ligands in C–N
palladium coupling.
optimized conditions to be used with 1 mol% [PdCl(η3-C3H5)]2.
Comparison with eight other air-stable diphosphines,
triphosphines and tetraphosphines of the same class indi-
cates that the selectivity of the coupling of dichloroarene to
aniline derivatives by palladium catalysis is possible as long
as homocoupling and/or dehalogenation of chloroarenes is
avoided. Some limitations of the catalytic system in terms of
scope and selectivity are also established.
The selectivity of coupling to 3a was conserved for all of
the ligands used, except for the electron-poor diphosphine L3
Table 2 Performance of polydentate ferrocenylphosphines L1–L9 in
the palladium-catalysed arylation of aniline with 1,2-dichlorobenzenea
Results and discussion
In order to investigate our hypothesis we first explored the
performance of the air-stable and readily available
diphosphine 1,1′-bis(diphenylphosphino)ferrocene, DPPF
(L1), in the coupling of aniline with 1,2-dichlorobenzene
(Table 1).
In toluene in the presence of 1.4 equiv. t-BuOK, no cross-
coupling reaction occurred in the absence of palladium and
the phosphine ligand (entry 1). Under the same conditions
the use of 5 mol% Pd(OAc)2 or [PdCl(η3-C3H5)]2 in the
absence of auxiliary phosphine was also inefficient (entries 2
and 3). Satisfactorily, the formation of 3a, albeit in modest
Entry
Ligand
Conversion (%)
Yield in 3a (%)
1
2
3
4
5
6
7
8
9
L1
L2
L3
L4
L5
L6
L7
L8
L9
25
12
30
16
55
15
<5
<5
<5
20
10
15
13
52
13
—
—
—
a
Conditions: [Pd]/L (0.02 equiv.), aniline 1a (1 equiv.), 1,2-
dichlorobenzene 2a (1 equiv.), t-BuOK (1.4 equiv.), 100 °C, 17 h.
Table 1 Influence of reaction conditions on the palladium-catalysed arylation of aniline with 1,2-dichlorobenzene promoted by DPPF (L1)a
Entry
Pd source (mol%)
L1 (mol%)
Base/solvent
Conversion (%)
Yield in 3a (%)
1
2
3
4
5
6
7
8
9
10
—
—
—
—
2
2
2
2
2
10
2
t-BuOK/toluene
t-BuOK/toluene
t-BuOK/toluene
t-BuOK/toluene
t-BuOK/toluene
Na2CO3/toluene
Na2CO3/toluene
t-BuOK/DMF
0
0
0
25
20
0
0
0
0
20
16
0
Pd(OAc)2 (5)
[PdCl(η3-C3H5)]2 (5)
[PdCl(η3-C3H5)]2 (1)
Pd(OAc)2 (1)
Pd(OAc)2 (1)
[PdCl(η3-C3H5)]2 (1)
[PdCl(η3-C3H5)]2 (1)
[PdCl(η3-C3H5)]2 (5)
[PdCl(η3-C3H5)]2 (1)
0
0
40
29
40b
15
20
20
t-BuOK/toluene
t-BuOK/toluene
a
b
Conditions: [Pd]/L1 (0.01 to 0.1 equiv.), aniline 1a (1 equiv.), 1,2-dichlorobenzene 2a (1 equiv.), base (1.4 equiv.), 100 °C, 17 h. 115 °C.
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(entry 3). The sterically released L4 was inefficient (entry 4).19
We were glad to observe that the results unambiguously indi-
cated that the tridentate ferrocenylpolyphosphine L5 was by
far the most efficient and selective auxiliary for the coupling
we targeted, with a yield of 52% in 3a for a conversion of
55% of 2a (entry 5). The diphosphines L2 (which undergoes a
1,2-coordination to palladium with a smaller P-bite angle)
and L3 were found less efficient than DPPF (entries 2, 3
and 1, respectively). The conformationally constrained
triphosphine and tetraphosphine L7–L9 (which hold t-butyl
groups hampering the free rotation of the ferrocene back-
bone) were found completely inefficient under these condi-
tions. Conversely, the triphosphine L6, which is structurally
close to L5, selectively led to a modest yield in C–N coupling.
While we find triphosphine L5 a suitable auxiliary for
the selective arylation of aniline with 1,2-dichlorobenzene
at lower Pd-catalyst loading,20 we performed further optimi-
zation studies to improve the yield. These optimization pro-
cesses, which are summarized in Table 3, were focused on
the base and the reaction temperature since toluene solvent
allows conservation of excellent selectivity. The yield in 3a
was slightly improved by using the Pd/L5 system with t-BuOK
at higher temperature, 115 °C (see entries 1 and 2); this
dependence in temperature was confirmed by the reduced
yield obtained at 85 °C under identical conditions (entry 3).
At 100 °C the use of DBU and t-BuONa did not improve the
yields in 3a (entries 4 and 5, respectively). However, combin-
ing t-BuONa as the base and toluene at reflux significantly
improved the yield in 3a with a full conversion obtained
within 16 h (entry 6, isolated yield 90%). The highest reaction
rate which was achieved by using these conditions was
confirmed with 88% conversion in 8 h, and 68% conversion
in 4 h (entries 7 and 8). In comparison, when DPPF was
used under identical temperature and solvent conditions
with t-BuONa for 24 h, a conversion of only 77% of the
aniline was obtained with a yield of 69% in 3a and 8%
dehalogenation of 3a. This indicates a much slower kinetics,
which is detrimental to the selectivity regarding the
dehalogenation process.
product of 3a as evidenced by 1H NMR (δNH = 5.75 ppm
against 6.03 for 3a). In agreement, we observed that in the
presence of excess aniline (3 equiv.), bis(amination) takes
place over longer reaction times. Thus, it appears that the
coupling of the first equivalent of aniline is much faster than
the activation of the second chlorine atom for amination.21
This explains the better results of selectivity obtained in mono-
amination for L5.
With a satisfactory palladium-based system identified, a
performance survey of Pd/L5 in the coupling of 1,2-dichloro-
benzene with various aniline derivatives was conducted,
which is reported in Table 4.
The introduction of fluorine atoms into medicinal
compounds generally improves membrane transport, general
bioavailability, solubility, and metabolic stability compared
to non-fluorinated analogues. Therefore, fluorinated arenes
are present not only in a number of important pharma-
ceuticals, but also in agrochemicals, and are of general
interest in PET molecular imaging.22 We focused our
attention to the arylation of fluorinated anilines, which can
be, as electron-poor nucleophiles, deactivated substrates for
such C–N bond formation. Gratifyingly, the catalytic system
tolerated the introduction of a fluoro group in ortho, meta or
Table 4 Scope of the catalytic system Pd/L5 for the arylation of
aniline derivatives with 1,2-dichlorobenzenea
Entry
1
Amine
Dichloride
Product
Yieldb (%)
90
2
3
98
96
Using L5 a careful tuning of the reaction time is important
to optimize the yields since after 24 h of reaction the yield
in 3a dropped to 60% with about 35% dehalogenation
4
5
6
7
8
9
99
(62)
25 (90)c
0c
Table 3 Influence of the base and temperature on 3a synthesis using
the system Pd/L5a
Entry Base
Temp. (°C) Time (h) Conversion (%) Yield in 3a (%)
1
2
3
4
5
6
7
8
t-BuOK 100
t-BuOK 115
17
17
17
17
17
16
8
55
68
25
—
55
98
88
68
52
57
25
—
52
90
78
58
0c
t-BuOK
85
DBU
100
24 (44)c
t-BuONa 100
t-BuONa 115
t-BuONa 115
t-BuONa 115
4
a
Conditions: [Pd]/L (0.02 equiv.), amine 1a (1 equiv.), dichloride 2a
a
b
Conditions: [Pd]/L (0.02 equiv.), aniline 1a (1 equiv.), 1,2-
(1 equiv.), toluene, t-BuONa (1.4 equiv.), 115 °C, 16 h. Isolated
dichlorobenzene 2a (1 equiv.), toluene, base (1.4 equiv.).
2074 | Catal. Sci. Technol., 2014, 4, 2072–2080
yields of two or more runs (GC/1H NMR yields). c 22 h.
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Table 5 Coupling of polyfunctionalized substrates using 2 mol% Pd/L5a
para position since products 3b–3d were obtained in high
yields (Table 4, entries 2–4). The conversion of electron-
donating p-toluidine was also achieved in 88% yield within
16 h with a fairly good 62% yield (entry 5) in 3d′; however,
the dehalogenation product of 3d′ (26%) lowered the yield.
We also tested other amines having aromatic heterocycles
such as 2-aminopyridine 4 and 2-aminothiazole 8. Compound
4 was satisfactorily converted into 5, but due to purification
problems was isolated in only 25% yield (Table 4, entry 6).
Aminopyrimidine 6 and aminothiazole 8 did not react (entries
7–8). Tertiary amine 11 was isolated in only 24% yield (entry 9)
due to a partial conversion of the reagents into unidentified
products and its partial dehalogenation. Additionally, we
checked that the coupling of 1,2-dibromobenzene was also
possible with our system, and predictably 3a was obtained in
excellent 96% yield within only 2 h.21 Clearly, the system is
efficient for iodo- and bromoarenes; however, for cost reasons
the coupling of dichlorobenzenes is more valuable, even if
more difficult. Interestingly, the catalytic system we found did
not lead to any trace of carbazole cyclization, and thus is com-
plementary to a few domino-reactions previously reported.10–14
With the view of further exploring the limitations of this
catalytic system we examined the coupling of structurally
more challenging substrates mainly not explored in the inves-
tigations which have been described to date. In particular,
the coupling of functionalized dichloroarenes is of interest
due to the regioselectivity issues which may occur. Electron-
rich dichloroarenes were chosen because of their deactivation
effect on C–Cl oxidative addition on palladium. As shown in
Table 5 many various structures are thus accessible following
this method with, in some cases, a fairly good to high regio-
selectivity (up to 1 : 10). We unfortunately often ended with
mixtures in which the purification of the compounds by stan-
dard chromatographic methods was very difficult. Clearly,
besides the efficiency and regioselectivity of the system, we
expect further progress in the separation process of these
valuable isomers.
The coupling of aniline with 4-methyl-1,2-dichlorobenzene
and 3-methyl-dichlorobenzene give a 3 : 1 mixture of products
3e and 3e′, and 3f and 3f′, respectively, in about 70% isolated
yield after workup (Table 5, entries 1 and 2: 51% 3e, 17% 3e′,
49% 3f, 17% 3f′). Comparatively, the effect on the regio-
selectivity of the arylation reaction of a methoxy group
positioned on arenes is much stronger. Indeed, while the
arylation of aniline with 4-methoxy-1,2-dichlorobenzene gives a
1 : 1 mixture of 3g and 3g′ in 59% yield (entry 3: 31% 3g, 28%
3g′), the use of 3-methoxy-1,2-dichlorobenzene leads to 3h′
with high selectivity (60% yield, entry 4). The coupling of
4-methyl-1,2-dichlorobenzene with anilines methoxylated in
various positions is also possible, albeit the selectivity is fairly
low (1 : 2 in favour of 3i′–3k′, entries 5–7). In addition the
separation from unconverted materials is very difficult. Finally,
the coupling of 4-methylated aniline with 3-methoxy-1,2-
dichlorobenzene and 4-methoxy-1,2-dichlorobenzene proceeds
satisfactorily with a good selectivity (entries 8 and 9). When the
chlorine atom is at the ortho position to the methoxy group, the
Yield (%) /
Entry Amine
1
Dichloride Product(s)
(selectivity)
68 (3 : 1)
2
3
4
66 (3 : 1)
59 (1 : 1)
60 (1 : 10)
5
85 (1 : 2)b
6
7
79 (1 : 2)b
71 (1 : 2)b
8
9
55 (1 : 6)b
80 (1 : 5)
a
Conditions: [Pd]/L (0.02 equiv.), amine 1a (1 equiv.), dichloride 2a
b
(1 equiv.), toluene, t-BuONa (1.4 equiv.), 115 °C, 20 h. Yields and
selectivity were determined by consistent GC and 1H NMR analyses.
regioselectivity is up to 1 : 6 in favour of 3m′ (vs. 3m), in agree-
ment with what was observed for the formation of 3h′ (vs. 3h).
A relevant question is the underlying reasons for the better
efficiency of L5 over the other ferrocenyl di-, tri- and
tetraphosphines in the arylation of aniline with dichloroben-
zene. Based on our previous DFT18 and kinetic investiga-
tions,23 which were respectively focused on the activity of
ferrocenylpolyphosphines in the reductive elimination (RE)
and oxidative addition (OA) to palladium, we propose the
catalytic cycle shown in Fig. 2.
This cycle includes the two crucial intermediates I1 and
I2. Indeed, the tridentate phosphine stabilizes the Pd0 spe-
cies I1,18,23 while the small bite angle due to 1,2-P phosphine
coordination favours the OA of chloride substrates. Inversely,
this type of small bite angle coordination strongly disfavours
the RE step (see the poor performance of ligand L2). The
isomerization to palladium complex I2, which is embedded
into a 1,1′-P coordination with a much larger bite angle, may
be the preferred pathway for an efficient RE of the arylated
amine. This kind of isomerization (or Pd centre shuttling)
from 1,2-P to 1,1′-P coordination for Pd(II) complexes has
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chromatography or on an HP-5 capillary column (30 m) for
GC-MS. All of the ferrocenylphosphine ligands were synthesized
using the reported literature methods. The ferrocenyl-
polyphosphine ligands are commercially available from STREM
Chemicals under the name HiersoPHOS. All ferrocenyl-
phosphines were stored and weighed under air without special
precautions.
Synthesis of triphosphine L5
A solution of (Ph2P)2Cp(t-Bu)Li (1.85 g, 3.7 mmol) in 20 mL
of THF was added at −40 °C to a stirred suspension of anhy-
drous FeCl2 (0.45 g, 3.55 mmol) in 20 mL of THF. After 2 h,
20 mL of THF solution of (i-Pr2P)2CpLi (0.67 g, 3.55 mmol)
was added to the mixture. The THF solvent was evaporated
in vacuo and the residue was refluxed in 40 mL of toluene for
3 h. From the cooled reaction mixture, the crude product was
filtered off and purified by chromatography to provide 1.80 g
(70% yield) of L5. Spectroscopic data were in agreement with
those reported in the literature.15b
Fig. 2 Catalytic cycle of C–N coupling with Pd/L5 favouring both
chloroarene OA and biarylamine RE.
been previously calculated as not only possible but also
energetically favoured,18 and experimentally documented by
NMR spectroscopy24 and X-ray crystallography.18 Finally, the
donating effect of the phosphino group (i-Pr)2P– also clearly
helps the reaction to smoothly proceed (see for comparison
the performance of L6, Table 2, entry 6). This general
behaviour is obviously not possible for any of the other
ferrocenylphosphines tested in the present study.
1H NMR (400.13 MHz, CDCl3): δ = 7.73 (m, 4H, Ph), 7.40
(m, 6H, Ph), 7.12–6.95 (m, 10H, Ph), 4.21 (t, 2H, JHP = 1.2 Hz,
3
3,5HCp), 4.17 (t, 2H, JHH = 2.0 Hz, 3′,4′(or 2′,5′)HCp), 3.96
3
(m, 2H, JHP < 2.0 Hz, JHH = 2.0 Hz, 2′,5′(or 3′,4′)HCp), 1.53
2
3
(hept(d), 1H, JHP = 2.6 Hz, JHH = 7.0 Hz, CHiPr), 1.38
t
3
3
Conclusions
(s, 9H, Bu), 0.93 (dd, 6H, JHP = 12.8 Hz, JHH = 6.8 Hz,
i
3
3
i
CH3 Pr), 0.67 (dd, 6H, JHP = 13.0 Hz, JHH = 7.0 Hz, CH3 Pr).
31P NMR (161.98 MHz, CDCl3): δ = −0.93 (s, 1P, Pi-Pr2),
−22.01 (s, 2P, PPh2). Elemental analysis: calcd. (%) for
C44H49P3Fe (726.64): C 72.73, H 6.80; found C 72.65, H 6.77.
The
air-stable
tridentate
ferrocenylpolyphosphine
1,2-bis(diphenylphosphino)-1′-(diisopropylphosphino)-4-tert-
butylferrocene, L5, employed in 2 mol% in combination with
1 mol% [PdCl(η3-C3H5)]2 in toluene with t-BuONa as base
constitutes an efficient and selective system for the coupling
of aniline derivatives with dichlorobenzene. This amount of
palladium/ligand is the lowest reported to date for such
demanding coupling. This catalytic system is several times
faster when dibromoarenes are employed for the C–N
coupling. This cross-coupling of demanding chlorobenzene
substrates generally induces homocoupling or dehalogenation
processes when other ferrocenylphosphines, solvents or bases
are used. The scope and limitation of the optimized system
were reported, showing good efficiency for the coupling of
electron-poor fluoroanilines (deactivated nucleophiles) and
electron-rich methylated and methoxylated dichlorobenzenes
(deactivated electrophiles).
General procedure for the catalytic reactions
In a Schlenk tube equipped with a stirring bar were introduced
the aniline derivative (2 mmol, 1 equiv.), 1,2-dichloroarene
(2 mmol, 1 equiv.), the complex [PdCl(η3-C3H5)]2 (0.02 mmol),
L5 (0.04 mmol), and t-BuONa (2.8 mmol, 1.4 equiv.). The tube
was purged several times with argon. Toluene (9 mL) was
added to the mixture. The Schlenk tube was placed in an oil
bath at 115 °C and the reactants were allowed to stir under
reflux for 16 to 20 h. Then, the reaction mixture was analysed
by GC-MS to determine the conversion of the reagents. At room
temperature, 5 mL of diethyl ether was added and filtration
using a pad of Celite® was done. The solvent was removed
from the filtrate by heating the reaction vessel under vacuum
and the residue was charged directly onto a silica gel column
for flash chromatography.
Experimental
General remarks
2-Chlorodiphenylamine (3a)
The reactions were carried out in oven-dried (115 °C) glass-
ware under an argon atmosphere using Schlenk and vacuum-
line techniques. The solvents were distilled over appropriate
drying and deoxygenating agents prior to use. Commercial
aryl halides and aniline derivatives were used without further
purification. 1H, 19F and 13C NMR spectra were recorded in
CDCl3 using a 300 MHz Bruker Avance, unless otherwise
stated. GC and GC-MS analyses were achieved on a Supelco
equity-5 capillary column using a Shimadzu GC-2014 for gas
From aniline (190 μL, 2 mmol) and 1,2-dichlorobenzene
(230 μL, 2 mmol), 3a was obtained in 90% (366 mg) yield
(pale yellow oil).
1H NMR (300 MHz, CDCl3): δ (ppm) = 7.29–7.24 (m, 2H),
7.22–7.18 (m, 1H), 7.09 (dt, J = 9.0 Hz, J = 3.0 Hz, 3H), 7.03
(dd, J = 9 Hz, J = 3.0 Hz, 1H), 6.96 (tt, J = 9.0 Hz, J = 3.0 Hz,
1H), 6.72 (qd, J = 9.0 Hz, J = 3.0 Hz, 1H), 6.03 (s, broad 1H).
13C NMR (75 MHz, CDCl3): δ (ppm) = 141.5, 140.3, 129.7,
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129.4(2C), 127.4, 122.7, 121.5, 120.4, 120.2(2C), 115.6.
Elemental analysis: calcd (%) for C12H10ClN (203.67):
C 70.77, H 4.95; found C 71.04, H 4.82.
(2-Chlorophenyl)pyridin-2-ylamine (5)
From 2-aminopyridine (189 mg, 2 mmol) and 1,2-dichloro-
benzene (230 μL, 2 mmol), 5 was obtained in 25% (102 mg)
yield (yellow oil).
1H NMR (300 MHz, CDCl3): δ (ppm) = 8.26 (dd, J = 6.0 Hz,
J = 1.2 Hz, 1H), 8.07 (dd, J = 8.1 Hz, J = 1.2 Hz, 1H), 7.55
(td, J = 7.8 Hz, J = 2.1 Hz, 1H), 7.40 (dd, J = 7.8 Hz, J = 1.5 Hz,
1H), 7.25 (td, J = 8.7 Hz, J = 1.4 Hz, 1H), 6.94 (td, J = 7.8 Hz,
J = 1.5 Hz, 1H), 6.86 (d, J = 8.4 Hz, 1H), 6.81 (dd, J = 7.2 Hz,
J = 2.1 Hz, 1H), NH obscured. 13C NMR (75 MHz, CDCl3):
δ (ppm) = 154.9, 148.2, 137.8, 137.3, 129.5, 127.5, 123.2,
122.4, 119.7, 116.0, 110.1. Elemental analysis: calcd (%) for
C11H9ClN2 (204.67): C 64.56, H 4.43; found C 64.14, H 4.43.
HR-mass (electrospray): found [M + H]+ = 205.0537; calcd =
205.0527, δ = −4.8 ppm.
2-Chloro-2′-fluorodiphenylamine (3b)
From 2-fluoroaniline (200 μL, 2 mmol) and 1,2-dichlorobenzene
(230 μL, 2 mmol), 3b was obtained in 98% (432 mg) yield
(brown oil).
1H NMR (300 MHz, CDCl3): δ (ppm) = 7.41–7.37 (td, J =
7.8 Hz, J = 1.2 Hz, 2H), 7.23 (t, 1H, J = 1.5 Hz, 1H), 7.17
(m, 1H), 7.14 (m, 1H), 7.10–6.95 (m, 2H), 6.90–6.84 (qd, J =
7.2 Hz, J = 1.8 Hz, 1H), 6.13 (broad s, 1H). 13C NMR (75 MHz,
CDCl3): δ (ppm) = 153.2 (d, JCF = 242.0 Hz), 138.3, 128.8,
128.25 (d, JCF = 187.0 Hz), 126.4, 123.3 (d, JCF = 3.0 Hz), 121.6
(d, JCF = 12.8 Hz), 120.19(2C), 120.2 (d, JCF = 188.0 Hz), 115.2,
114.9 (d, JCF = 19.5 Hz). 19F NMR (282 MHz, CDCl3): δ (ppm) =
−129.38. Elemental analysis: calcd (%) for C12H9ClFN
(221.66): C 65.02, H 4.09; found C 65.04, H 4.02.
N-Methyl-2-chlorodiphenylamine (11)
From N-methylaniline (220 μL, 2 mmol) and 1,2-dichlorobenzene
(230 μL, 2 mmol), 11 was obtained in 24% (134 mg) yield
(yellow oil).
2-Chloro-3′-fluorodiphenylamine (3c)
1H NMR (300 MHz, CDCl3): δ (ppm) = 7.47 (d, J = 6.0 Hz,
1H), 7.18 (t, J = 9.0 Hz, 2H), 6.94 (t, J = 9.0 Hz, 3H), 6.75
(t, J = 6.0 Hz, 1H), 6.59 (d, J = 6.0 Hz, 2H), 3.23 (s, 3H).
13C NMR (75 MHz, CDCl3): δ (ppm) = 148.6, 145.4, 130.9,
129.2(2C), 128.8, 128.2, 121.3(2C), 117.8(2C), 113.5, 39.0.
Spectroscopic data were in agreement with those reported in
the literature;25 however, the elemental analysis was unsatis-
factory hypothetically due to some dehalogenation.
From 3-fluoroaniline (200 μL, 2 mmol) and 1,2-dichlorobenzene
(230 μL, 2 mmol), 3c was obtained in 96% (437 mg) yield
(brown oil).
1H NMR (300 MHz, CDCl3): δ (ppm) = 7.39 (dd, J = 8.1 Hz,
J = 1.5 Hz, 1H). 7.34 (dd, J = 8.1 Hz, J = 1.5 Hz, 1H), 7.25–7.19
(m, 1H), 6.91–6.84 (m, 3H), 6.74–6.67 (tdd, J = 8.4 Hz, J =
2.4 Hz, J = 0.9 Hz, 1H), 6.45–6.36 (m, 1H), 6.13 (broad s, 1H).
13C NMR (75 MHz, CDCl3): δ (ppm) = 162.6 (d, JCF = 244 Hz),
142.6 (d, JCF = 10.5 Hz), 138.1, 129.5 (d, JCF = 8.25 Hz), 128.9,
(2-Chloro-4-methyl)diphenylamine (3e)
126.5, 121.5 (d, JCF = 12.8 Hz), 120.5, 115.9, 113.6 (d, JCF
=
3.0 Hz), 107.7 (d, JCF = 21.0 Hz), 104.8 (d, JCF = 25.0 Hz).
19F NMR (282 MHz, CDCl3): δ (ppm) = −111.87. Elemental
analysis: calcd (%) for C12H9ClFN (221.66): C 65.02, H 4.09;
found C 65.36, H 3.99. Best analysis obtained to date.
From aniline (190 μL,
2 mmol) and 1,2-dichloro-4-
methylbenzene (260 μL, 2 mmol), 3e was obtained in 51% yield.
1H NMR (300 MHz, CDCl3): δ (ppm) = 7.25 (d, J = 6.0 Hz,
2H), 7.22 (d, J = 1 Hz, 1H), 7.15 (d, J = 6.0 Hz, 1H), 7.09 (t, J =
9 Hz, 2H), 7.02 (d, J = 9 Hz, 1H), 6.55 (dd, J = 6.0 Hz, J = 1 Hz,
1H), 6.04 (broad s, 1H), 2.26 (s, 3H). 13C NMR (75 MHz, CDCl3):
δ (ppm) = 141.7, 139.9, 130.9(2C), 129.5(2C), 129.0, 128.0,
121.4, 120.2(2C), 119.1.
2-Chloro-4′-fluorodiphenylamine (3d)
From 4-fluoroaniline (200 μL, 2 mmol) and 1,2-dichlorobenzene
(230 μL, 2 mmol) 3d was obtained in 99% (437 mg) yield
(brown oil).
1H NMR (300 MHz, CDCl3): δ (ppm) = 7.25–7.22 (dd, J =
7.8 Hz, J = 1.2 Hz, 1H), 7.04–6.99 (m, 2H), 6.97 (m, 1H),
6.94–6.89 (m, 3H), 6.66 (qd, J = 6.3 Hz, J = 2.4 Hz, 1H), 5.89
(broad s, 1H). 13C NMR (75 MHz, CDCl3): δ (ppm) = 156.9
(d, JCF = 240.0 Hz), 140.0, 136.2 (d, JCF = 3.0 Hz), 128.6, 126.5,
(2-Chloro-5-methyl)diphenylamine (3e′)
From aniline (190 μL,
2 mmol) and 1,2-dichloro-4-
methylbenzene (260 μL, 2 mmol), 3e′ was obtained in 17% yield.
1H NMR (300 MHz, CDCl3): δ (ppm) = 7.25 (d, J = 6.0 Hz,
2H), 7.09 (t, J = 9.0 Hz, 2H), 7.02 (d, J = 9 Hz, 1H), 6.98 (d, J =
9.0 Hz, 1H), 6.92 (d, J = 9.0 Hz, 1H), 6.87 (d, J = 9.0 Hz, 1H),
5.96 (broad s, 1H), 2.28 (s, 3H). 13C NMR (75 MHz, CDCl3):
δ (ppm) = 142.3(2), 137.5, 130.1, 129.5(2C), 122.5, 121.9,
120.2(2C), 118.6, 116.7.
122.2 (d, JCF = 7.5 Hz, 2C), 119.8, 118.95, 115.1 (d, JCF
=
21.2 Hz, 2C), 113.5. 19F NMR (282 MHz, CDCl3): δ (ppm) =
−119.54. Elemental analysis: calcd (%) for C12H9ClFN (221.66):
C 65.02, H 4.09; found C 65.08, H 4.01.
2-Chloro-4′-methyldiphenylamine (3d′)
(2-Chloro-3-methyl)diphenylamine (3f)
From p-toluidine (214 mg, 2 mmol) and 1,2-dichlorobenzene
(230 μL, 2 mmol), 3d was formed in 62% yield (NMR).
Spectroscopic data were identical to the ones previously
reported.12a
From aniline (190 μL, 2 mmol) and 1,2-dichloro-3-
methylbenzene (260 μL, 2 mmol), 3f was obtained in 49% yield.
1H NMR (300 MHz, CDCl3): δ (ppm) = 7.34–7.29 (m, 2H),
7.17–7.12 (m, 3H), 7.08–6.98 (m, 2H), 6.78–6.73 (m, 3H), 2.42
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(s, 3H). 13C NMR (75 MHz, CDCl3): δ (ppm) = 141.85, 140.3,
137.1, 129.4, 127.9, 125.5, 121.9, 120.2, 115.2, 113.2, 20.7.
3.89 (s, 3H), 2.27 (s, 3H). 13C NMR (75 MHz, CDCl3): δ (ppm) =
149.0, 137.2, 131.0, 130.2, 130.1, 127.9, 120.8, 117.6, 117.0,
115.8, 110.7, 55.7, 20.4. The purification of this compound
from its starting material (15%) and isomer was troublesome.
(2-Chloro-6-methyl)diphenylamine (3f′)
From aniline (190 μL,
2 mmol) and 1,2-dichloro-3-
methylbenzene (260 μL, 2 mmol), 3f′ was obtained in 17% yield.
1H NMR (300 MHz, CDCl3): δ (ppm) = 7.34–7.29 (m, 2H),
7.17–7.12 (m, 2H), 7.08–6.98 (m, 2H), 6.78–6.73 (m, 3H), 2.20
(s, 3H). 13C NMR (75 MHz, CDCl3): δ (ppm) = 141.9, 140.3,
129.4, 128.9, 127.5, 126.9, 126.5, 122.5, 120.2, 113.2, 20.7.
(2-Chloro-5-methylphenyl)(2-methoxyphenyl)amine (3i′)
From 2-methoxyaniline (230 μL, 2 mmol) and 1,2-dichloro-
4-methylbenzene (260 μL, 2 mmol), 3i′ was obtained in
28% yield
1H NMR (300 MHz, CDCl3): δ (ppm) = 7.34–7.18 (m, 3H),
7.01–6.89 (m, 3H), 6.63 (d, J = 8.1 Hz, 1H), NH obscured,
3.89 (s, 3H), 2.27 (s, 3H). 13C NMR (75 MHz, CDCl3): δ (ppm) =
149.5, 139.4, 137.3, 129.4, 128.6, 121.6, 121.5, 120.7, 119.8,
110.9, 55.7, 21.3. The purification of this compound from its
starting material (15%) and isomer was troublesome.
(2-Chloro-4-methoxy)diphenylamine (3g)
From aniline (190 μL,
2 mmol) and 1,2-dichloro-4-
methoxybenzene (270 μL, 2 mmol), 3g was obtained in 31% yield.
1H NMR (300 MHz, CDCl3): δ (ppm) = 7.33 (d, J = 9.0 Hz,
2H), 7.18 (m, 2H), 7.05 (m, 1H), 6.82 (d, J = 1.0 Hz, 1H), 6.76
(dd, J = 9.0 Hz, J = 1.0 Hz, 1H), 6.37 (dd, J = 9.0 Hz, J =
1.0 Hz), 6.09 (broad s, 1H), 3.79 (s, 3H). 13C NMR (75 MHz,
CDCl3): δ (ppm) = 159.7, 141.2, 132.9, 130.6, 129.5, 123.9,
122.9, 120.6, 117.5, 113.6, 55.5.
(2-Chloro-4-methylphenyl)(3-methoxyphenyl)amine (3j)
From 3-methoxyaniline (230 μL, 2 mmol) and 1,2-dichloro-
4-methylbenzene (260 μL, 2 mmol), 3j was obtained in
24% yield.
1H NMR (300 MHz, CDCl3): δ (ppm) = 7.31 (d, J = 8.1 Hz,
1H), 7.25–7.22 (m, 3H), 7.02–6.64 (m, 2H), 6.53 (dd, J = 8.1 Hz,
(2-Chloro-5-methoxy)diphenylamine (3g′)
From aniline (190 μL,
2 mmol) and 1,2-dichloro-4-
methoxybenzene (270 μL, 2 mmol), 3g′ was obtained in 28% yield.
1H NMR (300 MHz, CDCl3): δ (ppm) = 7.33 (d, J = 9.0 Hz,
2H), 7.25 (m, 2H), 7.18 (m, 2H), 7.05 (m, 1H), 7.00 (d, J = 1.0 Hz,
1H), 6.09 (broad s, 1H), 3.73 (s, 3H). 13C NMR (75 MHz, CDCl3):
δ (ppm) = 158.6, 141.2, 129.95, 129.5, 122.9, 120.6, 113.1, 105.6,
101.3, 55.7.
J = 2.4 Hz, 1H), NH obscured, 3.79 (s, OCH3), 2.28 (s, CH3). 13
C
NMR (75 MHz, CDCl3): δ (ppm) = 160.7, 143.7, 137.1, 131.0,
130.1, 129.3, 128.0, 118.9, 117.4, 111.3, 107.1, 104.5, 55.3, 20.4.
The purification of this compound from its starting material
(21%) and isomer was troublesome.
(2-Chloro-5-methylphenyl)(3-methoxyphenyl)amine (3j′)
(2-Chloro-3-methoxy)diphenylamine (3h)
From 3-methoxyaniline (230 μL, 2 mmol) and 1,2-dichloro-
4-methylbenzene (260 μL, 2 mmol), 3j′ was obtained in
55% yield.
From aniline (190 μL,
2 mmol) and 1,2-dichloro-3-
methoxybenzene (356 mg, 2 mmol), 3h was obtained in less
than 5% yield (1H NMR).
1H NMR (300 MHz, CDCl3): δ (ppm) = 7.21–7.19 (d, J =
1.5 Hz, 1H), 7.14 (d, J = 1.2 Hz, 1H), 6.75 (dd, J = 8.1 Hz, J =
1.8 Hz, 2H), 6.71 (t, J = 2.4 Hz, 2H), 6.68–6.60 (m, 1H), NH
obscured, 3.81 (s, OCH3), 2.26 (s, CH3). 13C NMR (75 MHz,
CDCl3): δ (ppm) = 160.7, 143.1, 139.6, 137.5, 130.1, 129.3,
121.6, 118.9, 116.9, 112.3, 107.7, 105.6, 55.3, 21.3. The purifi-
cation of this compound from its starting material (21%) and
isomer was troublesome.
(2-Chloro-6-methoxy)diphenylamine (3h′)
From aniline (190 μL,
methoxybenzene (356 μL, 2 mmol), 3h′ was obtained in 60%
(281 mg) yield (orange solid).
2 mmol) and 1,2-dichloro-3-
1H NMR (300 MHz, CDCl3): δ (ppm) = 7.32 (t, J = 7.5 Hz,
2H), 7.17 (d, J = 7.5 Hz, 2H), 7.1–7.03 (m, 2H), 6.90 (dd, J =
8.4 Hz, J = 1.2 Hz, 1H), 6.47 (dd, J = 8.1 Hz, J = 1.2 Hz, 1H),
6.19 (broad s, 1H), 3.92 (s, 3H). 13C NMR (75 MHz, CDCl3):
δ (ppm) = 154.8, 140.6, 140.5, 128.4(2C), 126.05, 121.7,
119.6(2C), 108.4, 106.9, 101.9, 55.2. C13H12ClNO (233.69). HR-
mass (electrospray): found [M + Na]+ = 256.0499; calcd =
256.0500, δ = 0.3 ppm. Elemental analysis: calcd (%) for
C13H12ClNO: C 66.81, H 5.18; found C 67.01, H 5.13.
(2-Chloro-4-methylphenyl)(4-methoxyphenyl)amine (3k)
From 4-methoxyaniline (230 μL, 2 mmol) and 1,2-dichloro-
4-methylbenzene (260 μL, 2 mmol), 3k was obtained in
25% yield.
1H NMR (300 MHz, CDCl3): δ (ppm) = 7.20 (d, J = 8.4 Hz,
1H), 7.16 (m, 1H), 7.07–6.97 (m, 2H), 6.89 (dd, J = 8.1 Hz, J =
1.5 Hz, 1H), 6.84–6.75 (m, 2H), 5.80 (broad s, NH), 3.71
(s, 3H), 2.15 (s, 3H). 13C NMR (75 MHz, CDCl3): δ (ppm) =
154.9, 138.4, 133.8, 128.8, 129.0, 127.0, 123.5, 119.2, 113.7,
113.3, 54.5, 20.3. The purification of this compound from its
starting material (29%) and isomer was troublesome.
(2-Chloro-4-methylphenyl)(2-methoxyphenyl)amine (3i)
From 2-methoxyaniline (230 μL, 2 mmol) and 1,2-dichloro-4-
methylbenzene (260 μL, 2 mmol), 3i was obtained in 57%
yield. 1H NMR (300 MHz, CDCl3): δ (ppm) = 7.34–7.18 (m, 3H),
7.01–6.89 (m, 3H), 6.63 (d, J = 8.1 Hz, 1H), NH obscured,
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(2-Chloro-5-methylphenyl)(4-methoxyphenyl)amine (3k′)
and the “Région Bourgogne” (PARI-SMT8) is gratefully
acknowledged. Thanks are due to Johnson-Matthey for a kind
palladium gift.
From 4-methoxyaniline (230 μL, 2 mmol) and 1,2-dichloro-
4-methylbenzene (260 μL, 2 mmol), 3k′ was obtained in
46% yield.
1H NMR (300 MHz, CDCl3): δ (ppm) = 7.09 (d, J = 8.1 Hz, Notes and references
1H), 7.07–6.97 (m, 2H), 6.84–6.75 (m, 2H), 6.69 (s, 1H), 6.43
1 M. Platon, R. Amardeil, L. Djakovitch and J.-C. Hierso,
(d, J = 8.1 Hz, 1H), 5.70 (broad s, NH), 3.72 (s, 3H), 2.11
(s, 3H). 13C NMR (75 MHz, CDCl3): δ (ppm) = 115.2, 140.7,
136.5, 133.1, 128.1, 123.5, 122.6, 118.9, 116.1, 113.7, 54.5,
19.2. The purification of this compound from its starting
material (29%) and isomer was troublesome.
Chem. Soc. Rev., 2012, 41, 3929.
2 S. Cacchi, G. Fabrizi and G. Zeni, Chem. Rev., 2005, 105,
2873; and the update in S. Cacchi and G. Fabrizi,
Chem. Rev., 2011, 111, PR215.
3 For general reviews on metal-mediated carbazoles and
indoles formation, see: (a) H.-J. Knölker and K. R. Reddy,
Chem. Rev., 2002, 102, 4303; (b) I. Nakamura and
Y. Yamamoto, Chem. Rev., 2004, 104, 2127; (c) F. Alonso,
I. P. Beletskaya and M. Yus, Chem. Rev., 2004, 104, 3079; (d)
G. Zeni and R. C. Larock, Chem. Rev., 2004, 104, 2285; (e)
G. Zeni and R. C. Larock, Chem. Rev., 2006, 106, 4644; ( f )
G. Kirsch, S. Hesse and A. Comel, Curr. Org. Chem., 2004,
1, 47; (g) G. R. Humphrey and J. T. Kuethe, Chem. Rev.,
2006, 106, 2875; (h) L. Ackermann, Synlett, 2007, 507; (i)
K. Krüger, A. Tillack and M. Beller, Adv. Synth. Catal., 2008,
350, 2153; ( j) R. Vicente, Org. Biomol. Chem., 2011, 9, 6469.
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D. M. Ketcha, J. Org. Chem., 1992, 57, 5891; (b)
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6 K. Hirata, C. Ito, H. Furukawa, M. Itoigawa, L. M. Cosentino
and K. Lee, Bioorg. Med. Chem. Lett., 1999, 9, 119.
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Photobiol., A, 2008, 194, 351.
(2-Chloro-4-methoxyphenyl)(4-methylphenyl)amine (3l)
From 4-methylaniline (215 mg, 2 mmol) and 1,2-dichloro-
4-methoxybenzene (270 μL, 2 mmol), 3l was obtained in less
than 10% yield (1H NMR).
(2-Chloro-5-methoxyphenyl)(4-methylphenyl)amine (3l′)
From 4-methylaniline (215 mg, 2 mmol) and 1,2-dichloro-
4-methoxybenzene (270 μL, 2 mmol), 3l′ was obtained in
50% yield in a mixture with 45% of the starting dichloride.
Purification was troublesome.
1H NMR (300 MHz, CDCl3): δ (ppm) = 7.11 (q, J = 8.4 Hz,
4H), 6.76 (dd, J = 8.7 Hz, J = 2.7 Hz, 1H), 6.72 (d, J = 2.7 Hz,
1H), 6. 32 (d, J = 8.7 Hz, J = 2.7 Hz, 1H), NH obscured, 3.79
(s, OCH3), 2.38 (s, CH3). 13C NMR (75 MHz, CDCl3): δ (ppm) =
158.1, 140.7, 137.4. 131.8, 129.6, 128.9, 120.5, 114.6, 103.9,
99.5, 54.8, 19.7.
(2-Chloro-3-methoxyphenyl)(4-methylphenyl)amine (3m)
From 4-methylaniline (217 mg, 2 mmol) and 1,2-dichloro-
3-methoxybenzene (355 mg, 2 mmol), 3m was obtained in
67% yield.
8 J. Li and A. C. Grimsdale, Chem. Soc. Rev., 2010, 39, 2399.
9 J. V. Grazulevicius, P. Strohriegl, J. Pielichowski and
K. Pielichowski, Prog. Polym. Sci., 2003, 28, 1297.
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71, 9403; (c) B. R. Bedford, M. Betham, P. H. J. Charmant
and L. A. Weeks, Tetrahedron, 2008, 64, 6038.
1H NMR (300 MHz, CDCl3): δ (ppm) = 7.20–7.00 (m, 2H),
6.83 (dd, J = 8.1 Hz, J = 1.44 Hz, 2H), 6.79 (dd, J = 8.3 Hz, J =
1.3 Hz, 1H), 6.63 (d, J = 8.5 Hz, 1H), 6.43 (dd, J = 8.2 Hz, J =
1.2 Hz, 1H). 5.29 (s, NH), 3.91 (s, OCH3), 2.33 (s, CH3). 13C
NMR (75 MHz, CDCl3): δ (ppm) = 156.4, 142.4, 138.7, 132.8,
129.9, 122.3, 122.2, 110.0, 107.3, 102.4, 56.5, 20.8.
11 T. Wenderski, K. M. Light, D. Ogrin, S. G. Bott and
C. J. Harlan, Tetrahedron Lett., 2004, 45, 6851.
(2-Chloro-6-methoxyphenyl)(4-methylphenyl)amine (3m′)
12 (a) L. Ackermann and A. Althammer, Angew. Chem., Int. Ed.,
2007, 46, 1627; (b) L. Ackermann, A. Althammer and
P. Mayer, Synthesis, 2009, 20, 3493.
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2008, 350, 2179; (b) M. Catellani, E. Motti and N. Della Ca',
Top. Catal., 2010, 53, 991.
14 (a) T. Watanabe, S. Ueda, S. Inuki, N. Fujii and
H. Ohno, Chem. Commun., 2007, 4516; (b) T. Watanabe,
S. Oishi, N. Fujii and H. Ohno, J. Org. Chem., 2009,
74, 4720.
From 4-methylaniline (217 mg, 2 mmol) and 1,2-dichloro-
3-methoxybenzene (355 mg, 2 mmol), 3m′ was obtained in
13% yield.
1H NMR (300 MHz, CDCl3): δ (ppm) = 7.20–7.00 (m, 9.2H),
6.83 (dd, J = 8.1 Hz, J = 1.44 Hz, 2H), 6.79 (dd, J = 8.3 Hz, J =
1.3 Hz, 1H), 6.63 (m, J = 8.5 Hz, 1H), 6.43 (dd, J = 8.2 Hz, J =
1.2 Hz, 1H), 5.29 (s, NH), 3.80 (s, OCH3), 2.27 (s, CH3). 13C
NMR (75 MHz, CDCl3): δ (ppm) = 155.8, 138.7, 133.9, 129.3,
127.4, 127.1, 124.4, 121.7, 116.2, 56.2, 20.8.
15 (a) J.-C. Hierso, A. Fihri, R. Amardeil, P. Meunier, H. Doucet,
M. Santelli and B. Donnadieu, Organometallics, 2003, 22,
4490; (b) J.-C. Hierso, A. Fihri, R. Amardeil, P. Meunier,
H. Doucet, M. Santelli and V. V. Ivanov, Org. Lett., 2004, 6,
Acknowledgements
Support provided by the “Université de Bourgogne” and
CNRS (PhD grant awarded to M. P. in the 3MIM program)
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3473; (c) J.-C. Hierso, A. Fihri, R. Amardeil, P. Meunier,
Catalysis Science & Technology
21 For further details concerning coupling of anilines with
1,2-dibromobenzene using the same system based on L5,
see: S. Mom, M. Platon, H. Cattey, H. J. Spencer, P. J. Low
and J.-C. Hierso, Catal. Commun., 2014, 51, 10.
22 (a) P. Anbarasan, H. Neumann and M. Beller, Chem. – Asian
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2080 | Catal. Sci. Technol., 2014, 4, 2072–2080
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