Magnetic nano-Fe3O4 supported ionic liquids: A recoverable phase transfer catalyst for c-n cross coupling reaction

Article abstract of DOI:10.14233/ajchem.2013.14336

Magnetic nanoparticles-supported quaternary ammonium salts were prepared and evaluated as phase transfer catalysts. Some of them exhibited good activities in CuCl-catalyzed N-arylation of aryl amines and N-heterocycles with aryl iodides in aqueous solution without any ligands. They could be readily separated from reaction solution using an external magnet and reused three times with a little loss in activity.

Full text of DOI:10.14233/ajchem.2013.14336

Asian Journal of Chemistry; Vol. 25, No. 11 (2013), 6240-6242
http://dx.doi.org/10.14233/ajchem.2013.14336
Magnetic Nano-Fe
O Supported Ionic Liquids: A Recoverable
3 4
Phase Transfer Catalyst for C-N Cross Coupling Reaction
*
LIN TANG , YU SUN, LINGYUN ZHOU and TAILI SHAO
Department of Pharmacology, Wannan Medical College, Wuhu 241002, P.R. China
Corresponding author: Tel: +86 553 2932492; E-mail: jerry19860506@163.com
Received: 19 July 2012; Accepted: 2 May 2013)
*
(
AJC-13445
Magnetic nanoparticles-supported quaternary ammonium salts were prepared and evaluated as phase transfer catalysts. Some of them
exhibited good activities in CuCl-catalyzed N-arylation of aryl amines and N-heterocycles with aryl iodides in aqueous solution without
any ligands. They could be readily separated from reaction solution using an external magnet and reused three times with a little loss in
activity.
Key Words: Copper catalyst, C-N coupling, Nanometre supported, Ionic liquid, Cyclic utilization.
3 4
nanoparticles were dispersed in ethanol. Magnetic nano-Fe O
INTRODUCTION
6
supported ionic liquids was prepared by reported method .
The catalyst loading was determined to be 0.452 mmol/g by
elemental analysis.
C-N bond formation is considered to be an important
1
strategy in organic synthesis , but many toxic organic solvents
2
and expensive ligands were used in this field , which resulted
To evaluate the catalytic activity of b3, the reaction of
PhI with imidazole was selected as a model reaction. The
results were summarized in Table-1. It was demonstrated that
in the high cost. Since more and more attentions have been
focused on green chemistry, it is necessary to develop more
friendly reaction conditions for C-N cross coupling reactions.
Ionic liquids could make organic reaction system simpler and
3 4
almost all nano-Fe O supported ionic liquids exhibited good
catalytic activities, b3 is the best one but b6 did not catalyze
the reaction (Table-1, Entries 2-7). The catalytic activities of
them changed with the length change of middle carbon chain.
3
milder as phase transfer catalysts , but they are also expensive.
Magnetic nano-Fe
3 4
O could be an excellent and recyclable
4
support for easy separation by an external magnet . The synthetic
7
It suggested that steric effect affect the catalytic activity .
approach of magnetic nano-Fe
3
O
4
supported quaternary
ammonium salts was shown in Fig. 1.
TABLE-1
COMPARISON OF THE ACTIVITY OF
a
MeO
MeO Si
MeO
MeO
NANO-Fe O SUPPORTED IONIC LIQUIDS
3
4
I
+
N R
3
MeO Si
Me O
NR3I
N
I
CuCl (5 mol% ), F e O -IL
3
4
+
N
a
N
H
K C O , H O,
N
2
3
2
Ar, 80 °C, 24 h
b 1: R =C H
2
5
7
Fe O
b
3
4
b 2: R =C H
b 3: R =C H
Entry
Fe O -IL
3
Yield (%)
3
4
O
O
O
4
b 4: R =C H
9
Fe3O4
Si
1
2
3
4
5
6
7
None
b1
Trace
35
NR3I
7
15
17
5
b 5: R =C H
b 6: R =C H
8
b
6
b2
89
Fig. 1. Synthetic approach of magnetic nano-Fe
3 4
O supported quaternary
b3
96
ammonium salts
b4
87
b5
41
EXPERIMENTAL
was prepared by co-precipitation method
b6
Trace
Nano-Fe
according to literature . The Fe
in the average size of about 20 nm. Then the collected magnetic
3
O
4
a
Reaction conditions: iodobenzene (1 mmol), imidazole (1.5 mmol),
CuCl (5 mol %), Fe O -ionic liquid (0.01 g), K CO (1.5 mmol), H O
5
3
4
O nanoparticles obtained were
3
4
2
3
2
b
1 mL), Ar, Isolated yield
(

Vol. 25, No. 11 (2013)
3 4
Magnetic Nano-Fe O Supported Ionic Liquids 6241
Easy and rapid separation of nano-Fe
3
O
4
supported ionic
As shown in Tables 4 and 5, when substituted iodobenzene
was used in this system, yield decreased rapidly, substituent
group's position and electronic property nearly had no influence.
liquids by an external magnetic field is the most advantageous
feature of them. After the reaction, they were concentrated on
the bottom of the reaction vessel, the aqueous or organic phases
were separated by magnetic decantation. Moreover, the residual
catalyst in the reaction vessel could be washed and dried and
then subjected to the next run directly. We examined the lifetime
of b3 in the N-arylation of imidazole and iodobenzene. As
shown in Table-2, b3 could be recycled three times with a
little loss in activity.
TABLE-4
N-ARYLATION OF IODOBENZENE AND AMINES
OR N-HETEROCYCLES IN WATER
a
CuCl (5 mol%), b3 (0.01 g)
I
+
NuH
Nu
K
Ar, 80 °C, 24 h
2
CO
3 2
, H O,
b
Entry
1
NuH
N
Product
Yield (%)
N
96
TABLE-2
LIFETIME OF b3 FOR THE N-ARYLATION OFa
IODOBENZENE AND IMIDAZOLE IN WATER
N
N
H
H
3
C
N
N
2
3
4
N
N
90
51
35
N
N
N
I
N
N
CuCl (5 mol%), b3 (0.01 g)
+
N
CH
3
2
N
H
K CO , H O ,
N
N
H
2
3
2
Ar, 80 °C, 24 h
O
2
b
Entry
Cycle
Yield (%)
NO
N
1
2
3
1
2
3
96
94
92
N
H
H
3
C
a
CH3
N
H
Reaction conditions: iodobenzene (1 mmol), imidazole (1.5 mmol),
CuCl (5 mol %), b3 (0.01 g), K CO (1.5 mmol), H O (1 mL), Ar, 80
N
2
3
2
b
ºC, 24 h. Isolated yield
NH
2
H
N
5
6
95
60
After obtaining successful result, a brief research on
optimal reaction conditions was carried out (Table-3). A series
of copper catalysts and inorganic bases were screened exten-
sively. Finally, the best results were obtained when iodobenzene
NH
H
N
2
NO
2
O
N
2
7
8
N H
80
99
2
N H
N
(
1.0 mmol) and imidazole (1.5 mmol) were allowed to react
2 3
with 5 mol % of CuCl, 0.01 g b3 and 1.5 equiv K CO stirred
in 1 mL water at 80 ºC under argon for 24 h.
N
H
With this optimized conditions, we explored the general
scope of substrates, a variety of aryl iodides, amines and N-
heterocycles were introduced to this system. In all reactions,
we found that each reaction only had one product without any
H
N
9
92
N
a
Reaction conditions: iodobenzene (1 mmol), NuH (1.5 mmol), CuCl
3 4
by-products. It indicated that the nano-Fe O supported ionic
(
5 mol %), b3 (0.01 g), K CO (1.5 mmol), H O (1 mL), Ar, 24 h.
2
3
2
b
liquids could not only accelerate coupling reaction, but also
enhance selectivity of reaction.
Isolated yield
TABLE-3
OPTIMIZED REACTION CONDITIONS OF THE
N-ARYLATION REACTION IN WATER
TABLE-5
N-ARYLATION OF ARYL IODIDES WITH BENZYLAMINE
a
a
AND N-HETEROCYCLES IN WATER
N
I
Nu
I
b3
CuCl (5 mol%),
CO , H
Ar, 80 °C, 24 h
(0.01 g)
Cat. (5 mol%), b3
+
NuH
R
R
+
N
K
2
3
2
O,
N
H
Base, H O, 24 h
N
2
b
Yield
b
Entry
T (ºC)
60
Gas
Catalyst
CuCl
Base
Yield (%)
Entry
1
R
NuH
Product
(%)
1
2
3
4
5
6
7
8
9
Ar
Ar
Ar
Air
Ar
Ar
Ar
Ar
Ar
Ar
Ar
Ar
K CO
86
25
96
-
2
3
NH
NH
NH
NH
NH
2
2
2
2
30
CuCl
K CO
4-Cl
4-Br
4-F
13
2
3
Cl
Br
F
NH
NH
NH
80
CuCl
K CO
2
3
80
CuCl
K CO
2
3
2
3
4
5
10
9
80
nano Cul
Cul
K CO
96
86
93
40
92
21
-
2
3
80
K CO
2
3
80
CuBr
K CO
2
3
80
Cu(acac)2
CuO
K CO
2
3
4-
80
K CO
11
2
3
HO C
NH
COOH
2
10
11
12
80
CuCl
NaHCO3
Cl
80
CuCl
Cs CO
2
2
2
3
2-Cl
Trace
Trace
NH
80
CuCl
Na CO
45
2
3
a
CH
3
Reaction conditions: iodobenzene (1 mmol), imidazole (1.5 mmol),
CuCl (5 mol %), b3 (0.01 g), base (1.5 equiv), H O (1 mL), 24 h.
Isolated yield
NH
6
2-CH3
2
b
NH

6
242 Tang et al.
Asian J. Chem.
N
N
It can be seen in the research that the magnetite nano-
particles restricted reactions to only one product when high
efficiency catalyses reactions. It also showed good cycling
effect. The narrow substrate scope is disadvantage of the
magnetite nanoparticles which lies in steric effect of magnetite
nanoparticles in the reaction.
N
N
7
8
4-Cl
4-Br
Cl
Br
N
N
12
9
N
H
N
H
N
N
9
4-Cl
4-Br
11
9
N
H
Cl
REFERENCES
1. L.W. Greene, Am. J. Pharm., 120, 39 (1948).
2. (a) L. Zhu, L. Cheng, Y. Zhang, R. Xie and J. You, J. Org. Chem., 72,
2737 (2007); (b) R.K. Gujadhur, C.G. Bates and D. Venkatamman,
Org. Lett., 3, 4315 (2001).
10
N
H
Br
a
Reaction conditions: aryl iodides (1 mmol), NuH (1.5 mmol), CuCl (5
mol %), b3 (0.01 g), K CO (1.5 mmol), H O (1 mL), Ar, 24 h.
3. (a) M. Makosza, Pure Appl. Chem., 72, 1399 (2000); (b) M.J. O'Donnell,
Aldrichim. Acta, 24, 3 (2001).
2
3
2
b
Isolated yield
4
5
.
.
D. Guin, B. Baruwati and S.V. Manorama, Org. Lett., 9, 1419 (2007).
(a) R.J. He, P.H. Toy and Y.L. Lam, Adv. Synth. Catal., 350, 54 (2008);
(b) D. Georges, T. Patrick, T. Thierry, C. Jacques, L. Denis, B. Jean and
Q. Guy, New J. Chem., 13, 255 (1989); (c) B. Jean, T. Patrick, T. Thierry,
L. Denis, D. Georges and G.Q. Bull, Soc. Chim. Fr., 264 (1989).
RESULTS AND DISCUSSION
Magnetic nano-Fe supported ionic liquids was
3
O
4
prepared and used in phase transfer catalysts. b3 exhibited the
best activities in CuCl-catalyzed N-arylation of aryl amines
and N-heterocycles with aryl iodides in aqueous solution
without any ligands. And it could be recycled three times with
a little loss in activity.
6. I. Ahmed and R.V. Parish, J. Org. Chem., 452, 23 (1993).
K. Masato and S. Kazuhiko, Chem. Commun., 4718 (2006).
7
.