Heterogeneous copper-catalyzed hydroxylation of aryl iodides under air conditions

Article abstract of DOI:10.1039/c4cc02267j

In this work, the ligand-free heterogeneous copper Cu-g-C₃N ₄ was synthesized and used for the hydroxylation of aryl iodides to synthesize phenols using cheap bases. The catalyst was conveniently prepared, air-tolerant, reusable and scalable, and is very efficient for a wide range of substrates. The synthesis of substituted phenols can be carried out under air conditions and has great potential for practical applications. This journal is the Partner Organisations 2014.

Full text of DOI:10.1039/c4cc02267j

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Heterogeneous copper-catalyzed hydroxylation
of aryl iodides under air conditions†
Cite this: Chem. Commun., 2014,
0, 9072
5
Guodong Ding, Hongling Han, Tao Jiang,* Tianbin Wu and Buxing Han*
Received 27th March 2014,
Accepted 6th June 2014
DOI: 10.1039/c4cc02267j
www.rsc.org/chemcomm
In this work, the ligand-free heterogeneous copper Cu-g-C
N
3 4
Using cheap metals instead of noble metals is always the
was synthesized and used for the hydroxylation of aryl iodides pursuit of green catalysis. In 2009, the synthesis of phenols by direct
to synthesize phenols using cheap bases. The catalyst was con- cross-coupling of aryl iodides and hydroxide salts with CuI as the
8
veniently prepared, air-tolerant, reusable and scalable, and is very catalyst was reported simultaneously using either a 1,3-diketone or
9
efficient for a wide range of substrates. The synthesis of substituted a 1,10-phenanthroline ligand in an aqueous DMSO system under a
phenols can be carried out under air conditions and has great nitrogen atmosphere. More recently, several other ligands such as
1
2
13
14
potential for practical applications.
lithium pipecolinate, 8-hydroxyquinoline-N-oxide, D-glucose,
15
16
17
8
-hydroxyquinoline, pyridine-2-aldoxime, 8-hydroxyquinalidine
1
8
Serving as the structural constituents of pharmaceuticals, and glycolic acid were developed. These results indicate that
materials, and natural compounds, phenols are very important the transformation is highly dependent on the use of various
synthetic intermediates with numerous applications in manu- special ligands.
facturing of petrochemical, agrochemical polymers and other
Cu-based catalysts have been studied most extensively for this kind
1
chemicals. Effective synthesis methods for phenols are highly of reaction because they have some unique advantages. However,
2
required. Functionalized phenols can be synthesized through most reported studies were homogeneous, which need special
different routes, including coupling of hydroxide with aryl ligands and it is very difficult to recycle the catalysts. A sulfonic
3
4
5
19
halides, benzyne protocol, C–H activation/hydroxylation and acid resin (INDION-770) in combination with copper salts and
6
20
transformation of arene diazonium salts mediated by copper.
CuO supported on mesoporous silica were reported but expen-
Amongst these approaches the most attractive method is the sive CsOH is required. Tetra-n-butylammonium hydroxide was
conversion of aryl halides to phenols via the coupling with also employed as the base using CuI-nanoparticles as catalysts,
hydroxide using transition metal salts as the catalysts. Different the reactions were carried out under an inert atmosphere with a
21
types of catalysts have been developed, including homogeneous long reaction time. Copper-MOF was also found to be active in
3
Pd/ligand catalyst systems, semi-heterogeneous Pd/polyaniline the hydroxylation of aryl iodides, unfortunately, complete decom-
7
8–10
catalysts, homogeneous CuI/ligand catalyst systems,
and position of MOFs occurred after the reaction and the catalyst
0
11
22
Fe/N,N -dimethylethylenediamine catalysts.
Buchwald and co-workers did the first work on the hydroxyla- cost, highly efficient, and recyclable catalysts for the reactions is
tion in 2006. They realized the preparation of phenols from aryl/ highly desirable, but is challenging.
cannot be recycled. Obviously, developing heterogeneous, low
3a
heteroaryl bromides and chlorides by applying monodentate
phosphine ligands with Pd dba as the catalyst under an inert found wide applications in catalysis due to its special structure
atmosphere. Subsequently, some efficient catalytic systems and properties. The mpg-C
based on palladium/phosphine ligands have been developed fabricating supported catalysts. In the present work, we synthe-
Mesoporous graphitic carbon nitride (mpg-C N ) has recently
3 4
2
3
23
3 4
N materials show great potential in
24
3
b
3c
3d,e
3f
by the groups of Willis, Kwong, Beller,
and Stradiotto.
sized a copper-doped graphitic carbon nitride catalyst (Cu-g-C
3 4
N )
by using cheap urea and Cu(NO as the precursors through a
3 2
)
facile and efficient method. The catalyst was successfully applied
in the synthesis of phenols from aryl iodides and hydroxide.
Good to excellent yields of phenols could be obtained under air
conditions with low Cu loading. The catalyst could be reused
at least 5 times without a decrease in yield. More importantly,
Institute of Chemistry, Chinese Academy of Sciences, Zhongguancun North First
Street 2, 100190 Beijing, PR China. E-mail: Jiangt@iccas.ac.cn, Hanbx@iccas.ac.cn;
Fax: +86 10 6255 9373; Tel: +86 10 6256 2821
†
Electronic supplementary information (ESI) available: Experimental details,
NMR spectra of products, and characterization of the catalyst. See DOI:
0.1039/c4cc02267j
1
the Cu-g-C
3
N
4
catalyzed hydroxylation of aryl iodides can be
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conducted on 10 g scales under experimental conditions, thus results indicate that 4 mol% Cu-g-C
3
N
4
was the reasonable
has great potential in application for synthesizing substituted amount of the catalyst. An excellent result was obtained when
phenols. the reaction was carried out with 4 mol% Cu-g-C N4 using
3
Initially, we selected iodobenzene as the model substrate to NaOH as the base in DMSO aqueous solution at 120 1C under
optimize the reaction conditions, and the results are summarized in air conditions (Table 1, entry 20). To verify the crucial role of
Table 1. In DMSO aqueous solution with a DMSO and water volume the Cu-g-C
ratio of 1 : 1, a yield of 98.6% was achieved at 120 1C when using was also conducted in the absence of the Cu-g-C
cesium hydroxide (6.0 eq.) as the nucleophile and Cu-g-C and the reaction did not occur (Table 1, entry 22). To ascertain
8 mol%) as catalyst (Table 1, entry 1). When KOH or NaOH was the role of air in the catalytic reaction, we conducted a control
3
N
4
catalyst for the reaction, a control experiment
3 4
N
catalyst,
3 4
N
(
used as the nucleophile, almost quantitative product phenol was experiment under an Ar atmosphere. The result is also listed in
formed and no by-product was detected by GC-MS (Table 1, Table 1. Under an Ar atmosphere, the reaction can also be
entries 2 and 3). Encouraged by these good results, the effects of carried out with excellent yield (Table 1, entry 23). The result
concentrations of bases, reaction temperature and reaction solvents indicated that air did not affect the catalytic reaction.
on the phenol synthesis were further investigated. It is worth noting
The catalytic performance of the catalytic system was further
that at lower concentrations of the bases or when the temperature investigated using a wide range of aryl iodides as the substrates
was below 120 1C, the yield of phenol was low (Table 1, entries 4–12). and NaOH as the base, and the results are listed in Table 2. The
Solvent composition has remarkable influence on the yield of the cross-coupling reactions of aryl iodides with NaOH proceeded
product (Table 1, entries 6 and 13–18). Only 14.6% yield of phenol very smoothly at 120 1C under an air atmosphere to afford the
was formed in pure DMSO (Table 1, entry 13), and no product was corresponding coupling products in good to excellent yields.
detected in pure water (Table 1, entry 18). To further optimize the For the substrates with various electron-donating and electron-
reaction conditions, the effect of the amount of Cu-g-C N catalyst withdrawing groups such as –Cl, –CH , –CH CH CH CH , –OCH ,
3
4
3
2
2
2
3
3
on the reaction was studied. It can be known from Table 1 that –Ph, –F and –NO
reducing the amount of Cu from 8 mol% to 4 mol% did not reduce obtained (Table 2, entries 1–9 and 15). Even when using the
the yield, and the reaction could finish with excellent yields in 12 h substrates bearing strong donating groups, such as two –OCH
Table 1, entries 3, 19 and 20). However, when the amount of groups, the reaction also proceeded efficiently to afford the
Cu-g-C catalyst was further decreased to 2 mol%, the yield of corresponding coupling product in 85% isolated yields (Table 2,
phenol was only 50.9% after 24 h (Table 1, entry 21). The above entry 10). The reactions of 2,4-dimethoxy-1-iodobenzene,
,4-dimethyl-1-iodobenzene, and 3-ethyl-2-iodotoluene with NaOH,
2
, satisfactory yields of the desired phenols were
3
(
3 4
N
2
which are sterically hindered, provided high yields of the desired
coupling products (Table 2, entries 10–12).
Table 1 Optimization of hydroxylation of iodobenzene catalyzed by
a
Cu-g-C
3
N
4
in DMSO aqueous solution
Besides, bulky 1-iodonaphthalene and 2-iodonaphthalene were
also successfully converted into their corresponding phenols in
excellent isolated yields (Table 2, entries 13 and 14). The results
demonstrated that the steric effect did not affect the catalytic
reactions significantly. We also carried out the reactions using
1-chloro-4-iodobenzene and 4-fluoroiodobenzene as the reactants,
and the –Cl and –F groups were untouched in the reactions (Table 2,
entries 1 and 9). To examine the scope of the title reaction, we
investigated the reactions using bromobenzene, chlorobenzene and
b
c
Entry Base/eq. Temp./1C Solvents Catalyst/mol% Time/h Yields /%
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
CsOH/6 120
KOH/6 120
NaOH/6 120
KOH/6 100
KOH/4 120
NaOH/4 120
KOH/3 120
NaOH/3 120
NaOH/3 120
NaOH/4 110
NaOH/4 100
NaOH/4 90
NaOH/4 120
NaOH/4 120
NaOH/4 120
NaOH/4 120
NaOH/4 120
NaOH/4 120
NaOH/4 120
NaOH/4 120
NaOH/4 120
NaOH/4 120
NaOH/4 120
1.5/1.5
1.5/1.5
1.5/1.5
1.5/1.5
1.5/1.5
1.5/1.5
1.0/1.0
1.0/1.0
1.5/1.5
1.5/1.5
1.5/1.5
1.5/1.5
3.0/0
2.5/0.5
2.0/1.0
1.0/2.0
0.5/2.5
0/3.0
1.5/1.5
1.5/1.5
1.5/1.5
1.5/1.5
1.5/1.5
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
6
4
2
0
4
12
12
12
12
12
12
12
12
12
12
12
12
12
12
12
12
12
12
12
12
98.6
98.7
97.1
8.3
85.8
94.0
15.2
50.1
42.8
24.4
6.5
N.D.
14.6
20.0
58.5
42.2
18.3
N.D.
96.2
95.0
2-iodine thiophene as the substrates under the optimized reaction
conditions. The results are listed in Table 2 (entries 16–19). As
shown in Table 2, in our catalytic system, aryl bromides and
chlorides were inert under the experimental conditions giving no
cross-coupling products (Table 2, entries 16 and 17). However,
when 2 eq. of KI was added, bromobenzene can be converted to
the product in moderate yield (Table 2, entry 18). Heteroaryl
iodides, such as 2-iodine thiophene, also cannot work (Table 2,
entry 19). Thus our catalytic system provides a highly selective
coupling reaction of aryl iodides with NaOH under practical air
conditions, while the –F and –Cl groups are tolerated.
0
1
2
3
4
5
6
7
8
9
0
1
2
3
d
d
12(24) 43.1(50.9)
12
12
The stability and reusability of the Cu-g-C N catalyst were
3
4
N.D.e
investigated using the coupling reaction of iodobenzene with NaOH.
The results showed that the catalyst could be reused at least 5 times
without a decrease in catalytic activity and selectivity (Fig. 1). More
importantly, we successfully carried out a 10 g scale reaction here.
Iodobenzene (10.2 g, 50 mmol), NaOH (8.0 g, 200 mmol, 4 eq.)
95.5
a
b
All reactions were performed using 1.0 mmol of iodobenzene.
c
DMSO/mL:H O/mL. GC yield based on the added iodobenzene,
2
d
using 1,4-dioxane as internal standard. Data in parentheses indicate
2
e
4 h and its corresponding yield. Under an Ar atmosphere.
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Table 2 Hydroxylation of aryl iodides catalyzed by Cu-g-C
aqueous solution
3
N
4
in DMSO
Table 2 (continued)
a
b
Entry Aryl halides
Time/h Products
Yields /%
b
Entry Aryl halides
1
Time/h Products
12
Yields /%
c
1
8
12
12
47
0
83
1
9
2
3
12
16
83
78
a
Reactions were carried out with 1.0 mmol of aryl iodides, 4 mol% of
, 4 eq. of NaOH, 1.5 mL DMSO and 1.5 mL H O at 120 1C
under air conditions. Isolated yields based on the added aryl iodides.
Cu-g-C
3
N
4
2
b
c
2
eq. of KI was added.
4
5
6
16
16
16
84
89
83
7
16
80
Fig. 1 The reusability of the Cu-g-C
with 1.0 mmol of iodobenzene, 4 mol% of Cu-g-C
O at 120 1C under air conditions. Phenol yields were determined by GC.
3
N
4
catalyst. Reactions were carried out
3 4
N , 1.5 mL DMSO and 1.5 mL
8
9
12
12
89
82
H
2
and Cu-g-C
3 4
N (0.55 g, 2.9 mol%) were stirred in 60 mL of
DMSO/H O (1 : 1 in volume) at 120 1C under air conditions.
2
Complete conversion of iodobenzene was achieved after 20 h
and the phenol was confirmed as the sole product by GC with
1
1
1
0
1
2
16
16
16
85
89
80
9
8.8% yield, demonstrating the suitability of this protocol in
large-scale application.
The Cu-g-C catalyst was characterized systematically
Fig. S1–S5, ESI†). XRD patterns in Fig. S1 (ESI†) showed that
3 4
N
(
2
5
the Cu-g-C
3
N
4
catalyst exhibited the structure of g-C
3
N
4
.
No
diffraction peaks of copper species were observed in the
pattern. The presence of the copper species in Cu-g-C was
3 4
N
confirmed by XPS analysis. The high resolution Cu2p XPS
spectrum of the sample in Fig. S2b (ESI†) showed two main
peaks located at about 952.5 eV and 932.3 eV corresponding
2
6
to Cu2p1/2 and Cu2p3/2, respectively, which indicate the
existence of Cu species in the catalyst. The characteristic mode
1
1
3
4
16
16
79
82
+
ꢀ
1
of the triazine units (C
observed in the FT-IR spectra in Fig. S3 (ESI†), indicating the
presence of a typical structure of g-C . Thermogravimetric
analysis of Cu-g-C in Fig. S5 (ESI†) illustrated that the
Cu-g-C N catalyst can bear high temperature up to 600 1C.
6
N
7
) at 810 cm
(ref. 24c) is also
3 4
N
3 4
N
15
16
17
12
12
12
93
0
3
4
The reasons for the high activity and recyclability of the
Cu-g-C catalyst might partially originate from the special
structure and properties of the support. Schnick and Arne
3 4
N
2
7
2
8
Thomas reported that primary and secondary amines were
present at the surface of g-C . Here in our catalytic system,
0
3 4
N
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the secondary amines at the surface of the catalyst probably act
6 T. Cohen, A. G. Dietz and J. R. Miser, J. Org. Chem., 1977, 42,
+
2053–2058.
as a ligand of Cu species to promote the reaction. Besides as
7
B. J. Gallon, R. W. Kojima, R. B. Kaner and P. L. Diaconescu, Angew.
Chem., Int. Ed., 2007, 46, 7251–7254.
+
the support and the stabilizer for the Cu species, g-C N also
3
4
2
9
acted as the reducing agent during the catalyst preparation
process, leading to the formation of Cu species from the
8 A. Tlili, N. Xia, F. Monnier and M. Taillefer, Angew. Chem., Int. Ed.,
2009, 48, 8725–8728.
+
9
D. B. Zhao, N. J. Wu, S. Zhang, P. H. Xi, X. Y. Su, J. B. Lan and
J. S. You, Angew. Chem., Int. Ed., 2009, 48, 8729–8732.
3 2
Cu(NO ) precursor. Further exploration of the catalytic mecha-
nism is currently under investigation in our laboratory.
In summary, we have carried out the synthesis of hetero-
geneous copper-catalyzed phenols without additional ligands
10 J. M. Chen, T. J. Yuan, W. Y. Hao and M. Z. Cai, Catal. Commun.,
011, 12, 1463–1465.
2
1
1 Y. L. Ren, L. Cheng, X. Z. Tian, S. Zhao, J. J. Wang and C. D. Hou,
Tetrahedron Lett., 2010, 51, 43–45.
under air conditions. The cross-coupling reactions of various aryl 12 L. H. Jing, J. T. Wei, L. Zhou, Z. Y. Huang, Z. K. Li and X. G. Zhou,
Chem. Commun., 2010, 46, 4767–4769.
3 K. Yang, Z. Li, Z. Y. Wang, Z. Y. Yao and S. Jiang, Org. Lett., 2011, 13,
iodides with NaOH proceeded very smoothly with a low Cu amount
1
(4 mol%) at 120 1C in air to afford the corresponding coupled
4340–4343.
products in good to excellent yields. The Cu-g-C N catalyst can be 14 K. G. Thakur and G. Sekar, Chem. Commun., 2011, 47, 6692–6694.
3
4
1
5 S. Maurer, W. Liu, X. Zhang, Y. W. Jiang and D. W. Ma, Synlett, 2010,
76–978.
6 D. Yang and H. Fu, Chem. – Eur. J., 2010, 16, 2366–2370.
reused at least 5 times without a decrease in catalytic efficiency.
Phenol can be successfully produced with 98.8% yield under the
9
1
experimental conditions of the 10 g scale. The catalyst is easily 17 R. Paul, M. A. Ali and T. Punniyamurthy, Synthesis, 2010, 4268–4272.
1
1
2
2
2
2
2
8 Y. Xiao, Y. N. Xu, H. S. Cheon and J. Chae, J. Org. Chem., 2013, 78,
804–5809.
9 P. J. Amal Joseph, S. Priyadarshini, M. Lakshmi Kantam and
H. Maheswaran, Catal. Sci. Technol., 2011, 1, 582–585.
0 C. C. Chan, Y. W. Chen, C. S. Su, H. P. Lin and C. F. Lee, Eur. J. Org.
Chem., 2011, 7288–7293.
1 H. J. Xu, Y. F. Liang, Z. Y. Cai, H. X. Qi, C. Y. Yang and Y. S. Feng,
J. Org. Chem., 2011, 76, 2296–2300.
2 S. Priyadarshini, P. J. Amal Joseph, M. Lakshmi Kantam and
B. Sreedhar, Tetrahedron, 2013, 69, 6409–6414.
prepared using cheap raw materials, and is air and moisture-
tolerant, stable and recyclable. Thus, the Cu-g-C catalyzed
hydroxylation of aryl iodides shows great potential in applica-
tion for synthesizing substituted phenols.
The authors thank the National Natural Science Foundation
of China (21273253, 21021003) and the Chinese Academy of
Sciences (KJCX2.YW.H30) for financial support.
5
3 4
N
3 Y. Wang, X. C. Wang and M. Antonietti, Angew. Chem., Int. Ed., 2011,
50, 2–24.
Notes and references
4 (a) X. F. Chen, J. S. Zhang, X. Z. Fu, M. Antonietti and X. C. Wang,
J. Am. Chem. Soc., 2009, 131, 11658–11659; (b) Y. Wang, J. Yao,
H. R. Li, D. S. Su and M. Antonietti, J. Am. Chem. Soc., 2011, 133,
2362–2365; (c) G. D. Ding, W. T. Wang, T. Jiang, B. X. Han, H. L. Fan
and G. Y. Yang, ChemCatChem, 2013, 5, 192–200; (d) P. F. Zhang,
Y. T. Gong, H. R. Li, Z. R. Chen and Y. Wang, Nat. Commun., 2013,
4, 1593.
1
2
J. H. P. Tyman, Synthetic and Natural Phenols, Elsevier, New York, 1996.
D. A. Alonso, C. N ´a jera, I. M. Pastor and M. Yus, Chem. – Eur. J.,
2
010, 16(18), 5274–5284.
3
(a) K. W. Anderson, T. Ikawa, R. E. Tundel and S. L. Buchwald, J. Am.
Chem. Soc., 2006, 128, 10694–10695; (b) M. C. Willis, Angew. Chem., Int.
Ed., 2007, 46, 3402–3404; (c) G. Chen, A. S. C. Chan and F. Y. Kwong,
Tetrahedron Lett., 2007, 48, 473–476; (d) T. Schulz, C. Torborg, 25 F. Dong, L. W. Wu, Y. J. Sun, M. Fu, Z. B. Wu and S. C. Lee, J. Mater.
B. Sch ¨a ffner, J. Huang, A. Zapf, R. Kadyrov, A. B ¨o rner and M. Beller,
Chem., 2011, 21, 15171–15174.
Angew. Chem., Int. Ed., 2009, 48, 918–921; (e) A. G. Sergeev, T. Schulz, 26 (a) J. G. Jolley, G. G. Geesey, M. R. Haukins, R. B. Write and P. L.
C. Torborg, A. Spannenberg, H. Neumann and M. Beller, Angew. Chem.,
Int. Ed., 2009, 48, 7595–7599; ( f ) C. B. Lavery, N. L. Rotta-Loria,
R. McDonald and M. Stradiotto, Adv. Synth. Catal., 2013, 355, 981–987.
T. George, R. Mabon, G. Sweeney, J. B. Sweeney and A. Tavassoli, 27 B. V. Lotsch and W. Schnick, Chem. Mater., 2006, 18, 1891–1900.
J. Chem. Soc., Perkin Trans. 1, 2000, 2529–2574.
Wichlacz, Appl. Surf. Sci., 1989, 37, 469; (b) S. W. Gaarenstroom and
N. J. Winograd, Chem. Phys., 1977, 67, 3500; (c) J. C. Klein, A. Proctor,
D. M. Hercules and J. F. Black, Anal. Chem., 1983, 55, 2055–2059.
4
5
28 F. Goettmann, A. Fischer, M. Antonietti and A. Thomas, Chem.
Commun., 2006, 4530–4532.
(a) Y. H. Zhang and J. Q. Yu, J. Am. Chem. Soc., 2009, 131, 14654–14655;
(
b) R. E. Maleczka, F. Shi, D. Holmes and M. R. Smith III, J. Am. Chem. 29 A. Liljestrand, P. Bremberg and D. Arvidsson, US Pat., 20130133310,
Soc., 2003, 125, 7792–7793.
2011.
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