Amination of aryl halides by using an environmentally benign, recyclable copper catalyst

Article abstract of DOI:10.1002/ejoc.201200787

The combination of CuSO₄ with naturally occurring sucrose in a biodegradable aqueous solution of PEG-200 has been confirmed as a novel, recyclable, and environmentally benign homogeneous catalyst system for the direct amination of aryl halides with NH₃·H₂O. Electron-rich, electron-poor, and even ortho-substituted aryl bromides and iodides could be aminated to provide the desired primary arylamines in high yields at 90 °C without the need of an inert atmosphere. The combination of CuSO₄ with naturally occurring sucrose in a biodegradable, aqueous solution of PEG-200 has been confirmed to be a novel, recyclable, and environmentally benign homogeneous catalyst system for the direct amination of aryl halides with NH₃·H₂O. Copyright

Full text of DOI:10.1002/ejoc.201200787

Job/Unit: O20787
/KAP1
Date: 08-08-12 17:12:17
Pages: 6
SHORT COMMUNICATION
DOI: 10.1002/ejoc.201200787
Amination of Aryl Halides by Using an Environmentally Benign, Recyclable
Copper Catalyst
[a]
[a]
[a]
[b]
[b]
Manna Huang, Leilei Wang, Xinhai Zhu, Zuxing Mao, Daizhi Kuang, and
Yiqian Wan*[
a]
Keywords: Copper / Carbohydrates / Homogeneous catalysis / Amination / Sustainable chemistry
The combination of CuSO
4
with naturally occurring sucrose
3 2
of aryl halides with NH ·H O. Electron-rich, electron-poor,
in a biodegradable aqueous solution of PEG-200 has been
confirmed as a novel, recyclable, and environmentally be-
nign homogeneous catalyst system for the direct amination
and even ortho-substituted aryl bromides and iodides could
be aminated to provide the desired primary arylamines in
high yields at 90 °C without the need of an inert atmosphere.
Introduction
From then on, a variety of ligands (P- or P,N-containing)
have been successfully selected to perform the Pd-catalyzed
Aromatic amines and their derivatives are highly useful
and valuable starting materials and intermediates for or-
ganic synthesis and play an important role as intermediates
for agrochemicals, pharmaceuticals, conducting polymers,
[1a,3,5]
selective amination of aryl halides with ammonia.
[
3]
More recently, Beller and co-workers developed a stable,
versatile, and recyclable palladium/imidazolium–phosphane
system for the effective direct amination of aryl halides with
ammonia under an inert atmosphere. The active catalyst is
easily regenerated in situ from the air-/water-stable cationic
imidazolium after precipitation of the resulting amines by
the addition of hydrogen chloride.
and dyes in the chemical industry.[1] Given the significance
of anilines, great efforts have been made to directly produce
primary arylamines. Traditional methods for the prepara-
tion of primary amines by direct coupling of aryl halides
with ammonia or ammonia surrogates often suffer from one
[
2]
In particular, copper-catalyzed aminations by using
ammonia were also realized elegantly by Taillefer and other
or more shortages, including harsh reaction conditions,
low atom economy, the need for an additional cleavage step
to liberate the primary arylamine, the formation of waste,
[
1a,5d,6]
[7]
groups
since Lang and co-worker reported the first
and high costs when using ammonia surrogates.[
1a]
copper-catalyzed arylation of ammonia at low pressures
and low temperatures. However, despite of all these achieve-
ments, further advancements are still desired to improve the
efficiency of the corresponding catalysts. In this regard, the
development of a general amination protocol that involves
the use of less toxic and more easily separable solvents and
a recyclable homogeneous catalyst and that allows the ef-
ficient reaction of ortho-substituted halides is still desirable
There-
fore, NH ·H O, because of its great abundance and ex-
3
2
tremely low cost, is still by far the most interesting N-source
for the construction of primary amines as long as the for-
mation of catalytically inactive species resulting from the
displacement of ancillary ligands from the transition metal
by ammonia or the formation of diarylamines due to the
[
1a,3]
increased reactivity of the initially resulting anilines
[
3,5d]
have been obviated by cleverly designed ligands.[
4]
and challenging.
In 2006, the first selective direct amination of aryl halides
Recently, the direct amination of aryl halides with am-
employing a bulky Josiphos-type phosphane ligand with monia in water has attracted much attention. In 2010, Zhou
[
4]
[8]
5.5 bar of ammonia was reported by Hartwig and Shen.
and co-workers reported a sulfonato–Cu(salen) complex
catalyst for the reaction of a wide range of aryl bromides
[
a] School of Chemistry and Chemical Engineering,
Sun Yat-sen University,
and iodides with aqueous NH to afford good to excellent
3
yields at 120 °C within 12 h with KOH as the base. Also at
Guangzhou 510275, P. R. China
Fax: +86-20-8411-3610
2
2
that time, we realized the CuO/N ,N Ј-diisopropyloxalo-
E-mail: ceswyq@mail.sysu.edu.cn
hydrazide-catalyzed direct amination of aryl bromides and
Homepage:
07.html
http://ce.sysu.edu.cn/ChemTeacher/Incumbent/
[9]
iodides with aqueous NH at 60 °C; shortly thereafter, in
3
2
[b] Department of Chemistry & Materials Science,
Hengyang Normal University,
2011, the previously reported three-component catalyst
CuO/oxalyldihydrazide/hexane-2,5-dione was identified to
be effective for the direct amination of aryl chlorides with
Hengyang 421008, P. R. China
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201200787.
[
10]
aqueous NH3.
Eur. J. Org. Chem. 0000, 0–0
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1

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M. Huang, L. Wang, X. Zhu, Z. Mao, D. Kuang, Y. Wan
SHORT COMMUNICATION
Notably, Xu, Feng et al.[11] reported that CuI nanopar- glucose/fructose) together with the ratios of the main 2p3/
[
14]
ticles, as a recyclable catalyst, could be used for the amin- 2 peak to the shake-up peak in the XPS spectrum (Fig-
II
I
ation of aryl iodides and bromides with NH ·H O in an ure 2b) indicated that Cu was partially converted into Cu
3
2
aqueous solution of nBu NOH without an assisting ligand in the glucose/fructose system.
4
under relatively mild conditions (not higher than 80 °C) un-
der a nitrogen atmosphere. Another, more attractive proto-
col was reported by Chen[ in 2011, in which a range of
aryl halides could be aminated with aqueous ammonia with
a CuI/PEG catalyst system. However, the mechanism for
the unique promotion by Na PO is unclear and the pos-
12]
3
4
sibility for reuse of this system was not mentioned.
Development of a recyclable homogeneous copper-based
catalyst system for the direct amination of aryl halides with
ammonia is still challenging compared with the well-estab-
lished Pd-based methodology.[ Herein, we report copper/
sucrose as a recyclable, completely green catalyst for the ef-
fective and direct amination of aryl halides with NH ·H O
3]
3
2
at 90 °C in an aqueous solution of PEG-200 without the
protection of an inert atmosphere.
Results and Discussion
Inspired by Sekar[6e] who used d-glucosamine as a green
ligand for the copper-catalyzed synthesis of primary aryl- Figure 1. Optimization of ligands: 4-bromoanisole (1.0 mmol), 25–
amines from aryl halides and ammonia and considering 28% NH ·H O (750 µL), CuO (0.2 mmol), ligand (0.6 mmol),
O (1.0 mmol), PEG-300 (1.0 g), H O (1.0 mL), 90 °C,
5 h. A: sucrose; B: fructose; C: glucose; D: cellulose microcrystal-
3
2
K
3
PO
4
·7H
2
2
that carbohydrates (sucrose, glucose, and fructose) affect
1
II
the mobility of Cu and its thermodynamic behavior in
line; E: maltose; F: starch; G: glucosamine; H: glycerol; I: no li-
gand.
[
13]
aqueous solutions,
we envisioned that O-containing li-
gands could be used instead of N,O-containing ligands to
carry out the copper-catalyzed direct amination of aryl hal-
ides with NH ·H O in water. Hence, we used the amination
Encouraged by this result and the fact that sucrose was
3
2
of 4-bromoanisole with NH ·H O as a model reaction to the most effective ligand in the Cu catalyst system, we opti-
3
2
screen some O-containing ligands including sucrose, fruc- mized the reaction conditions by exploring the copper
tose, glucose, cellulose microcrystalline, maltose, starch, sources, bases, and PEGs, as well as different ratios of sub-
glucosamine, and glycerol (Figure 1). In addition, polyethyl- strates, catalysts, and ligands. As illustrated in Table 1, the
ene glycols (PEGs) are well known to be nontoxic, recycla- solubility of the copper salt and the valence of copper had
ble, thermally stable, and inexpensive media for the use as a significant influence on the reaction outcome (Table 1,
phase-transfer catalysts (PTCs), and they may even be ap- Entries 2–10), and CuSO was the most efficient among the
4
plicable in biomedical protocols. Because of the concerns copper sources screened (80% normalized GC yield;
associated with green chemistry, we used PEG instead of Table 1, Entry 4). The weaker base K PO (Table 1, En-
3
4
the even more efficient PTC tetrabutylammonium bromide try 4) was the optimal base for avoiding corrosion of the
TBAB), which we often used in our previously reported glassware, although the stronger base KOH (Table 1, En-
(
amination protocols in water. To our delight, sucrose was try 13) provided a similar conversion and yield. Moreover,
significantly more effective than other mono- and polysac- PEG-200 was the most efficient among the PEGs with dif-
charides (Figure 1). The model reaction provided 4-meth- ferent chain lengths investigated as both cosolvents and
oxyaniline in 62% isolated yield (71% normalized GC PTCs (Table 1, Entry 20). It should be noted that the quan-
yield) when using sucrose as a ligand at 90 °C for 15 h in tity of sucrose (50 mol-%; Table 1, Entry 32) is very crucial
a preheated oil bath. As expected, either copper (Table 1, for the conversion, as both lower and higher concentrations
Entry 1) or sucrose (Figure 1, column I) is necessary for a of sucrose in the reaction decreased the conversion. Further
good outcome of the model reaction. To confirm the sta- investigation revealed that
a sufficient quantity of
bility of sucrose under the experimental conditions, a mix- NH ·H O was needed for complete conversion of 4-bromo-
3
2
ture of equivalent glucose/fructose, usually occurring from anisole; for example, when we increased the volume of
the hydrolysis of sucrose, was used instead in the model NH ·H O from 750 to 950 µL, the conversion increased to
3
2
reaction, but little acceleration was observed (Table 1, En- 99% (Table 1, Entry 42). It must be noted that a higher
try 45). Moreover, the different appearance of the reaction temperature (120 °C) decreased the reaction rate and led
mixtures (Figure 2a, homogeneous blue-yellow solution to a lower yield, possibly because of the decomposition of
when using sucrose and heterogeneous slurry when using sucrose, although the exact mechanism remains unclear.
2
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Pages: 6
Copper-Catalyzed Aminations of Aryl Halides
Table 1. Optimization of the reaction conditions for the amination
[a]
3
of 4-bromoanisole with aqueous NH .
Entry Copper
mol-%]
Base
[mol-%]
PEG/H
[g/g]
2
O
Conv./Yield
(%)[
b]
[
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
none
Cu [20]
CuO [20]
K
K
K
K
K
K
K
K
K
K
3
3
3
3
3
3
3
3
3
3
PO
PO
PO
PO
PO
PO
PO
PO
PO
PO
4
4
4
4
4
4
4
4
4
4
[100]
[100]
[100]
[100]
[100]
[100]
[100]
[100]
[100]
[100]
300 [1:1]
300 [1:1]
300 [1:1]
300 [1:1]
300 [1:1]
300 [1:1]
300 [1:1]
300 [1:1]
300 [1:1]
300 [1:1]
300 [1:1]
300 [1:1]
300 [1:1]
300 [1:1]
0/0
15/15
76/71
86/80
82/73
83/76
69/63
3/3
72/67
72/66
14/13
77/68
87/79
14/12
74/56
75/65
67/55
6/6
CuSO
Cu(OAc)
CuCl [20]
Cu(NO
Cu O [20]
4
[20]
2
[20]
2
3 2
)
[20]
2
CuCl [20]
CuI [20]
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
CuSO
CuSO
CuSO
CuSO
CuSO
CuSO
CuSO
CuSO
CuSO
CuSO
CuSO
CuSO
CuSO
CuSO
CuSO
CuSO
CuSO
CuSO
CuSO
CuSO
CuSO
CuSO
CuSO
CuSO
CuSO
CuSO
CuSO
CuSO
CuSO
CuSO
CuSO
CuSO
CuSO
CuSO
CuSO
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
[20]
none
CO
[20]
[20]
[20]
[20]
[20]
[20]
[20]
[20]
[20]
[20]
[20]
[20]
[20]
[20]
[10]
[15]
[25]
[30]
[20]
[20]
[20]
[20]
[20]
[20]
[20]
[20]
[20]
[20]
[20]
[20]
[20]
[20]
[20]
[20]
K
2
3
[100]
KOH [100]
KF [100]
Na
Na
Cs
CsF [100]
2
CO
PO
3
[100] 300 [1:1]
[100] 300 [1:1]
[100] 300 [1:1]
3
4
2
CO
3
300 [1:1]
0:2
200 [1:1]
400 [1:1]
600 [1:1]
200 [2:0]
K
3
K
3
K
3
K
3
K
3
K
3
K
3
K
3
K
3
K
3
K
3
K
3
K
3
K
3
K
3
K
3
K
3
K
3
K
3
K
3
K
3
K
3
K
3
K
3
K
3
K
3
K
3
PO
PO
PO
PO
PO
PO
PO
PO
PO
PO
PO
PO
PO
PO
PO
PO
PO
PO
PO
PO
PO
PO
PO
PO
PO
PO
PO
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
[100]
[100]
[100]
[100]
[100]
[100]
[100]
[100]
[100]
[100]
[100]
[100]
[100]
[100]
[100]
[100]
[100]
[50]
73/69
91/82
86/82
46/43
40/30
200 [1.5:0.5] 80/67
200 [0.5:1.5] 48/38
200 [1:1]
200 [1:1]
200 [1:1]
200 [1:1]
200 [1:1]
200 [1:1]
200 [1:1]
200 [1:1]
200 [1:1]
200 [1:1]
200 [1:1]
200 [1:1]
200 [1:1]
200 [1:1]
200 [1:1]
200 [1:1]
200 [1:1]
200 [1:1]
200 [1:1]
200 [1:1]
42/35
57/46
96/83
Figure 2. (a) A visual demonstration of the outcome of the reac-
tions after cooling to room temperature. Left: Sucrose as the li-
gand; the color of the solution indicates the presence of Cu .
95/82
II
78/68[
c]
d]
e]
f]
92/81[
Right: A mixture of equivalent fructose/glucose as the ligand; a
I
[
heterogeneous slurry indicating the presence of Cu . (b) XPS analy-
95/84
I
93/81[
sis indicating Cu in reaction mixture using a CuSO /fructose/glu-
4
[
g]
h]
e]
e]
e]
e]
i]
cose system.
86/76
78/67[
75/67[
[
[75]
90/81
96/85[
NH
·H O in water consist of CuSO /sucrose (20/50 mol-%)
3 2 4
[125]
[150]
[100]
[100]
[100]
[100]
[100]
[100]
[
and K PO (100 mol-%) with aqueous NH ·H O (950 µL)
89/79
3
4
3
2
89/77[
in PEG-200 (1 g) and water (1 g) at 90 °C for 15 h (Table 1,
Entry 42).
To explore the scope of this catalyst system, a wide range
of aryl iodides and bromides were aminated with aqueous
[j]
94/81
99/88[
99/87[
k]
l]
[
m]
99/87
trace/0[
n]
NH ·H O under the optimized conditions. As shown in
3 2
Table 2, the direct amination of activated and unactivated
aryl bromides and iodides readily provided the desired
H O, 90 °C, 15 h. [b] Normalized GC yield. [c] Sucrose (0.3 mmol). products in high yields (Table 2, Entries 1–3, 5–16, 18).
[
a] Reaction conditions: 4-bromoanisole (1.0 mmol), 25–28% aque-
ous NH ·H O (750 µL), copper, sucrose (0.6 mmol), base, PEG,
3
2
2
[
d] Sucrose (0.4 mmol). [e] Sucrose (0.5 mmol). [f] Sucrose
0.7 mmol). [g] Sucrose (0.8 mmol). [h] Sucrose (0.9 mmol). [i] Su-
More interesting, the system tolerated ortho-substituted
halides, which afforded the corresponding products in
about 80% isolated yield (Table 2, Entries 4, 17). In ad-
(
crose (0.5 mmol) and aqueous NH
3
·H
3 2
2
O (650 µL). [j] Sucrose
·H O (850 µL). [k] Sucrose
(
0.5 mmol) and aqueous NH
0.5 mmol) and aqueous NH ·H
·H O (1050 µL). [m] Sucrose (0.5 mmol) aqueous but unfortunately only trace amounts of the target com-
O (1150 µL). [n] Fructose (0.5 mmol), glucose (0.5 mmol),
and aqueous NH ·H O (950 µL).
(
3
2
O (950 µL). [l] Sucrose (0.5 mmol) dition, the amination of aryl chlorides was also explored,
and aqueous NH
NH ·H
3
2
3
2
pounds were obtained under the experimental conditions
3
2
(Table 2, Entries 20, 21).
Finally, the homogeneous characteristic of the CuSO4/
In summary, after a brief survey of conditions, the opti- sucrose catalyst system encouraged us further to explore the
mal conditions for the direct amination of aryl halides with possibility of reuse. The reaction mixture was simply ex-
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M. Huang, L. Wang, X. Zhu, Z. Mao, D. Kuang, Y. Wan
Table 2. (continued)
SHORT COMMUNICATION
Table 2. Copper-catalyzed amination of aryl halides with aqueous
[
a]
3
NH .
[
a] Reaction conditions: aryl halide (1.0 mmol), 25–28% aqueous
NH (950 µL), CuSO ·5H O (0.2 mmol), sucrose (0.5 mmol),
PO ·7H O (1.0 mmol), PEG-200 (1.0 g), H O (1.0 mL), 90 °C,
5 h. [b] Isolated yield. [c] Detected by TLC.
3
4
2
K
1
3
4
2
2
to the residue, the reaction was run for a second time. In
the same way, the third cycle was run also to afford the
desired product in high yield (Figure 3).
tracted with diethyl ether to remove 4-methoxyaniline and
then bubbled with compressed air for 30 min to remove re-
sidual ammonia and diethyl ether thoroughly. After ad-
Figure 3. Reuse of the catalyst system. [a] 4-Bromoanisole
(
1.0 mmol), 25–28% aqueous NH
0.2 mmol), sucrose (0.5 mmol), K
3
·H
2
PO
O (950 µL), CuSO
·7H O (1.0 mmol), PEG-
4 2
·5H O
(
3
4
2
dition of K PO , 4-bromoanisole, and aqueous NH ·H O
3
4
3
2
2
200 (1.0 g), H O (1.0 mL). [b] Add 4-bromoanisole (1.0 mmol),
aqueous NH
3
·H
2
O (950 µL), K
3
PO
4
·7H
2
O (4.0 mmol).
4
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Copper-Catalyzed Aminations of Aryl Halides
ard, M. Toumi, Chem. Rev. 2008, 108, 3054–3131; c) S. A. Law-
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In conclusion, a recyclable, environmentally benign,
homogeneous catalyst system has been developed. The
combination of CuSO with naturally occurring sucrose as
well as biodegradable PEG-200 in water allows the direct
amination of a wide range of aryl halides with aqueous
4
[
2] R. C. Larock, Comprehensive Organic Transformations: A
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3
2
Chem. Eur. J. 2011, 17, 9599–9604.
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mary arylamines in high yields at 90 °C without the protec-
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synthetic chemistry in the laboratory and in industry.
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Experimental Section
Representative Procedure:
CuSO ·5H O (50 mg, 0.2 mmol), sucrose (171 mg, 0.5 mmol), 4-
bromoanisole (187 mg, 1.0 mmol), 28% aqueous NH ·H
O (338 mg, 1.0 mmol), PEG-200
O (1.0 mL), and a magnetic stir bar. The reaction mix-
A 10-mL vial was loaded with
4
2
3
2
O
(950 µL, 12.0 mmol), K
3 4 2
PO ·7H
(1.0 g), H
2
ture was stirred for 15 h in an oil bath preheated to 90 °C. After
allowing the mixture to cool to room temperature, the reaction
mixture was extracted with ethyl acetate (3ϫ 15 mL). The com-
bined organic phase was washed with water and brine, dried with
anhydrous Na SO , and concentrated in vacuo. The residue was
2 4
purified by flash column chromatograph on silica gel (ethyl acetate/
petroleum ether, 1:4) to afford 2a (104 mg, 85%) as a white solid.
+
1
MS (ESI+): m/z = 124 [M + H] . H NMR (300 MHz, CDCl
6.80–6.72 (m, 2 H, Ar-H), 6.69–6.61 (m, 2 H, Ar-H), 3.76 (s, 3 H,
OCH ), 3.43 (br. s, 2 H, NH ): δ
) ppm. 13C NMR (75 MHz, CDCl
152.9, 140.2, 116.6, 115.0, 56.0 ppm.
3
): δ
[
8] Z. Wu, Z. Jiang, D. Wu, H. Xiang, X. Zhou, Eur. J. Org. Chem.
2010, 1854–1857.
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Org. Chem. 2011, 4523–4527.
=
3
2
3
[
=
Supporting Information (see footnote on the first page of this arti-
cle): Experimental procedures, characterization data, and copies of
1
13
[11] H.-J. Xu, Y.-F. Liang, Z.-Y. Cai, H.-X. Qi, C.-Y. Yang, Y.-S.
Feng, J. Org. Chem. 2011, 76, 2296–2300.
the H NMR and C NMR spectra of all compounds.
[
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Acknowledgments
3710–3713.
[
13] A. C. F. Ribeiro, M. A. Esteso, V. M. M. Lobo, A. J. M. Va-
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This work was supported financially by grants from the National
Natural Science Foundation of China (20872182, 20802095).
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[1] a) Y. Aubin, C. Fischmeister, C. M. Thomas, J. L. Renaud,
Received: June 13, 2012
Chem. Soc. Rev. 2010, 39, 4130–4145; b) G. Evano, N. Blanch-
Published Online: ᭿
Eur. J. Org. Chem. 0000, 0–0
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
5

Job/Unit: O20787
/KAP1
Date: 08-08-12 17:12:17
Pages: 6
M. Huang, L. Wang, X. Zhu, Z. Mao, D. Kuang, Y. Wan
SHORT COMMUNICATION
Aminations
The combination of CuSO
4
with naturally
M. Huang, L. Wang, X. Zhu, Z. Mao,
occurring sucrose in a biodegradable, aque-
ous solution of PEG-200 has been con-
firmed to be a novel, recyclable, and en-
vironmentally benign homogeneous cata-
lyst system for the direct amination of aryl
D. Kuang, Y. Wan* ........................... 1–6
Amination of Aryl Halides by Using an
Environmentally Benign, Recyclable Cop-
per Catalyst
3 2
halides with NH ·H O.
Keywords: Copper
Homogeneous catalysis
Sustainable chemistry
/
Carbohydrates
Amination
/
/
/
6
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Eur. J. Org. Chem. 0000, 0–0