Cobalt-containing mesoporous ZSM-5 zeolite catalyzed C=C bond cleavage of alkenes to form nitriles

Article abstract of DOI:10.1055/s-0035-1560662

Cobalt-containing mesoporous ZSM-5 zeolite (Co-ZSM-5-M) catalyst showed high catalytic activity, selectivity, and excellent reusability in C=C double-bond cleavage of alkenes to form aromatic nitriles. All reactions proceeded smoothly to afford the desired target products in moderate to high yields under the optimal conditions. The Co-ZSM-5-M catalyst was recycled up to at least seven consecutive cycles without significant loss of its catalytic performance.

Full text of DOI:10.1055/s-0035-1560662

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© Georg Thieme Verlag Stuttgart · New York
2016, 27, 221–224
letter
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S. Xu et al.
Letter
Synlett
Cobalt-Containing Mesoporous ZSM-5 Zeolite Catalyzed C=C
Bond Cleavage of Alkenes To Form Nitriles
Shuling Xua
Tianhao Caib
Zhi Yun*a
Co-ZSM-5-M
R1
R1
N
TMSN3
+
R2
NBS, K3PO4•3H2O
MeCN, 80 °C
12 examples
40–93% yield
R1, R2 = H, aryl, alkyl
a College of Chemistry and Chemical Engineering, Nanjing Tech University,
Nanjing, Jiangsu 210009, P. R. of China
yunzhi@njtech.edu.cn
b Department of Chemical & Biological Engineering, University of New Mexico,
Albuquerque, NM 87131, USA
Received: 05.08.2015
Accepted after revision: 13.09.2015
Published online: 09.10.2015
al-group compatibility, prefunctionalization of the starting
materials, and the difficulty of separation of homogeneous
catalysts from the reaction products. Therefore, the devel-
opment of a recyclable and practical catalyst with high ac-
tivity and recyclability under mild conditions to achieve
this transformation is a great challenge. Herein we first re-
port the direct nitrogenation reaction of alkenes to prepare
aromatic nitriles over Co-ZSM-5-M catalyst in high yield.
The highly dispersed cobalt species in the Co-ZSM-5-M
framework have high activity, and the mesoporosity in the
catalyst facilitates the mass transfer and therefore improves
its catalytic performance. In addition, the Co-ZSM-5-M cat-
alyst can recycle seven runs without any significant activity
loss.
DOI: 10.1055/s-0035-1560662; Art ID: st-2015-w0616-l
Abstract Cobalt-containing mesoporous ZSM-5 zeolite (Co-ZSM-5-M)
catalyst showed high catalytic activity, selectivity, and excellent reus-
ability in C=C double-bond cleavage of alkenes to form aromatic ni-
triles. All reactions proceeded smoothly to afford the desired target
products in moderate to high yields under the optimal conditions. The
Co-ZSM-5-M catalyst was recycled up to at least seven consecutive cy-
cles without significant loss of its catalytic performance.
Key words mesoporous zeolite, Co-ZSM-5-M, C=C bond cleavage,
alkene, nitrile
Nitriles are among the most prominent targets in syn-
thetic chemistry because of their biological and pharma-
ceutical activities.1 Moreover, the cyano group is a key pre-
cursor for multifunctional groups including aldehydes,
amines, amidines, amides, or carboxylic acids.2 Generally,
Sandmeyer or Rosenmund–von Braun reaction approaches
are traditional methods for the preparation of nitriles.3 In
the past decades, a metal-mediated approach has also been
investigated in the coupling of aryl (pseudo)halides or aryl
boric acid with metal cyano reagents such as MCN (M = K,
Na, Cu, or Zn), TMSCN, or K3Fe(CN)6.4 Recently, transition-
metal-catalyzed C–H functionalization reactions have been
widely developed as a powerful tool for the cyanation.5
More recently, the group of Guo,6 Denton,7 and Chow8 dis-
covered efficient nitrogenation reaction of alkenes through
C=C bond cleavage to produce diverse aromatic nitriles. Es-
pecially, Jiao and co-workers described novel N-bromosuc-
cinimide (NBS)-mediated nitrile synthesis through C=C
bond cleavage of aromatic styrenes.9 However, these meth-
ods suffered from harsh reaction conditions, bad function-
Figure 1 (a) The XRD pattern of Co-ZSM-5-M, (b) N2 adsorption iso-
therm of the Co-ZSM-5-M sample, (c) SEM and (d) TEM micrographs of
Co-ZSM-5-M.
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S. Xu et al.
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Figure 1 (a) shows the XRD pattern of the Co-ZSM-5-M,
which exhibits typical peaks in the range of 5–50° associat-
ed with the MFI structure. The inductively coupled plasma
(ICP) analysis clearly points out the cobalt content of 2.4
wt% in the Co-ZSM-5-M, which suggests that the cobalt has
been successfully introduced into the zeolite. The nitrogen
sorption isotherm of the Co-ZSM-5-M exhibits a hysteresis
loop at a relative pressure of 0.5–0.95, which is typically as-
signed to the presence of a mesostructure (Figure 1, b). Cor-
respondingly, the mesopore size diameter is centered at 16
nm (insert, Figure 1, b). Sample textural parameters are
presented in the Supporting Information. The scanning
electron microscopy (SEM) image reveals the Co-ZSM-5-M
sample with a particle size in the range of 300–600 nm. It
seems that the particle is composed of the aggregation of
the nanoparticles with main size of 15–40 nm (Figure 1, c).
Transmission electron microscopy (TEM) imaging indicates
that the cobalt particles are dispersed in the Co-ZSM-5-M.
In order to explore this approach, 4-methoxystyrene
(1a) was chosen as a model substrate to react with TMSN3
(Table 1). First, the reactions were performed with different
transition-metal catalysts. It was found that Cu(OAc)2 and
Co(acac)2 afforded lower yields compared to Co(NO3)2·6H2O
(Table 1, entries 1–3). Much better results were provided by
50 mg Co-ZSM-5-M, which induced a complete nitrogena-
tion of the substrate and gave 2a in 93% yield (Table 1, entry
4). Further investigation revealed that the base played a
critical role in this transformation, and the K3PO4·3H2O was
superior to other bases, such as KOH, K2CO3, and KF (Table
1, entries 5–7). Screening a range of solvents displayed that
acetonitrile (MeCN) performed best among other solvents
including tetrahydrofuran (THF), N,N-dimethylformamide
(DMF), and toluene (Table 1, entries 8–10). In addition, the
use of ZSM-5 zeolite (no cobalt incorporation) as the cata-
lyst was less effective (Table 1, entry 11). This control ex-
periment indicated that the incorporation of cobalt is the
key for generating catalytic activity.
With the optimized conditions in hand (Table 1, entry
4), we next turned our attention to evaluate the scope of ni-
trogenation reaction of alkenes. As shown in Scheme 1, the
examined substrates provided moderate to excellent yields.
Generally, common substituents including electron-donat-
ing groups were all tolerated under the standard condi-
tions, giving the corresponding products 2a–f in good to ex-
cellent yields. Notably, styrene also proceeded smoothly to
provide the benzonitrile 2g in moderate yield. Moreover,
alkenes with 2-thienyl and the sterically hindered 1-naph-
thyl group afforded the corresponding nitriles 2h and 2i in
75% and 68% yields, respectively. It is noted that 1,2-disub-
stituted alkene could obtain the aromatic nitriles 2j and 2k
in 54% and 48% yields, which tremendously expand the
scope of this nitrogenation reaction. Furthermore, 1-
Table 1 Optimization of Reaction Conditions in the C=C Bond Cleav-
age of Alkene 1a to Prepare Nitrile 2aa
catalyst, NBS
TMSN3
+
O
O
N
base, solvent
80 °C, 24 h
1a
Catalyst
Cu(OAc)2
2a
Entry
Base
Solvent
Yield (%)a,b
1c
2c
3c
4
K3PO4·3H2O
K3PO4·3H2O
K3PO4·3H2O
K3PO4·3H2O
KOH
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
THF
79
85
40
93
80
50
78
<5
<5
67
48
Co(NO3)2·6H2O
Co(acac)2
Co-ZSM-5-M
Co-ZSM-5-M
Co-ZSM-5-M
Co-ZSM-5-M
Co-ZSM-5-M
Co-ZSM-5-M
Co-ZSM-5-M
ZSM-5-M
5
6
K2CO3
7
KF
8
K3PO4·3H2O
K3PO4·3H2O
K3PO4·3H2O
K3PO4·3H2O
9
toluene
DMF
10
11
MeCN
a Co-ZSM-5-M (50 mg), base (2.0 equiv), NBS (1.0 equiv), TMSN3 (2.5 equiv).
b Yields were determined by GC.
c Conditions: 10 mol% catalyst were used.
ethynyl-4-methoxybenzene (1l) also gave the desired prod-
uct 2l in 40% yield.
The recyclability of the Co-ZSM-5-M catalyst was tested
in the C=C bond cleavage of 4-methoxystyrene with TMSN3.
Table 2 shows the recyclable results under the adopted re-
action conditions. After each run, the Co-ZSM-5-M catalyst
was separated from the product by centrifugation and was
immediately reused (with the addition of fresh reactants)
without any treatment. The Co-ZSM-5-M catalyst can recy-
cle seven runs without significant reduction in activity. This
result indicates that the Co-ZSM-5-M zeolite possesses a
good reusability, which is one of the key features in the
practical application in industry.
Table 2 Catalyst Recyclability Experimenta
Entry
Co-ZSM-5-Mb
Yield (%)
1
2
3
4
5
6
7
1st cycle
2nd cycle
3rd cycle
4th cycle
5th cycle
6th cycle
7th cycle
93
93
92
90
90
89
89
a GC yield, 1a was used as the substrate.
b Fresh Co-ZSM-5-M was used in the first cycle, and then the catalyst was
directly used in the following cycles after being recovered.
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Co-ZSM-5-M, NBS
TMSN3
+
R
N
R
K3PO4•3H2O, MeCN
1
2
80 °C, 24 h
O
N
O
N
2g, 73%
1g
1a
1b
2a, 93%
O
N
O
O
N
N
S
S
2h, 75%
1h
2b, 90%
2c, 87%
O
N
n-Pr
n-Pr
1c
2i, 68%
2j, 54%
1i
O
O
N
O
N
O
1j
1d
1e
1f
2d, 80%
2e, 50%
2f, 88%
H2N
H2N
N
N
Ph
2k, 48%
2l, 40%
1k
O
N
O
N
1l
Scheme 1 The scope of reaction and yields were determined by GC
N3
Br+
+
Br
TMSN3
NBS
On the basis of these results and related precedents,9,10
a
Br
R
R
R
R
plausible reaction mechanism for this Co-ZSM-5-M-cata-
lyzed C=C bond cleavage of alkenes to form nitriles is thus
proposed (Scheme 2). First, alkene 1 reacts with NBS pro-
ducing a bromonium ion I, which could undergo isomeriza-
tion to intermediate II, which is subsequently attacked by
azide ions to generate species III. In this case, the interme-
diate III undergoes elimination assisted by K3PO4 to form
the alkenylazide intermediate IV. The following oxidization
of IV affords intermediate V by the cobalt catalyst. Subse-
quently, the intermediate V gives imidoyl cobalt intermedi-
ate VI by the Co-ZSM-5-M catalyst via the denitrogenative
process. Finally, the following carbon–carbon bond cleavage
and rearrangement of VI generates the desired products 2
and complex VII.
1
II
I
III
O
N
K3PO4
HBr
Co-ZSM-5-M
[Co]
Co-ZSM-5-M
O
R
N
[Co]
O2
VII
R
R
N3
R
N3
2
N2, H+
O
VI
Scheme 2 Proposed reaction pathway
V
IV
and selectivity in this transformation. This reaction pro-
vides a series of aromatic nitriles synthesized with this
method in moderate to excellent yields. Further investiga-
tion is being conducted to explain the reaction mechanism
on mesoporous Co-ZSM-5 zeolites.
In summary, we have described Co-ZSM-5-M zeolites as
a useful catalyst for aromatic nitriles synthesis from alkenes
through C=C bond cleavage.11 The experiments demonstrat-
ed that the Co-ZSM-5-M exhibited good catalytic activity
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Acknowledgment
2008, 130, 10496. (i) Dohi, T.; Morimoto, K.; Takenaga, N.; Goto,
A.; Maruyama, A.; Kiyono, Y.; Tohma, H.; Kita, Y. J. Org. Chem.
2007, 72, 109.
We thank the support of this work by the National Natural Science
Foundation of China (PI, 21373034), the Natural Science Foundation
of Jiangsu Province of China (PI, 13KJA530001), and ‘A Project Funded
by the Priority Academic Program Development of Jiangsu Higher Ed-
ucation Institutions (PAPD)’.
(5) Reviews: (a) Colby, D. A.; Bergman, R. G.; Ellman, J. A. Chem. Rev.
2010, 110, 624. (b) Lyons, T. W.; Sanford, M. S. Chem. Rev. 2010,
110, 1147. (c) Yeung, C. S.; Dong, V. M. Chem. Rev. 2011, 111,
1215. (d) Sun, C.-L.; Li, B.-J.; Shi, Z.-J. Chem. Rev. 2011, 111, 1293.
(e) Ackermann, L. Chem. Rev. 2011, 111, 1315. (f) McMurray, L.;
O’Hara, F.; Gaunt, M. J. Chem. Soc. Rev. 2011, 40, 1885. (g) Cho, S.
H.; Kim, J. Y.; Kwak, J.; Chang, S. Chem. Soc. Rev. 2011, 40, 5068.
(h) Engle, K. M.; Mei, T.-S.; Wasa, M.; Yu, J.-Q. Acc. Chem. Res.
2012, 45, 788. (i) Shi, Z.-Z.; Zhang, C.; Tang, C.-H.; Jiao, N. Chem.
Soc. Rev. 2012, 41, 3381. (j) Yamaguchi, J.; Yamaguchi, A. D.;
Itami, K. Angew. Chem. Int. Ed. 2012, 51, 8960. (k) Wencel-
Delord, J.; Glorius, F. Nat. Chem. 2013, 5, 369.
Supporting Information
Supporting information for this article is available online at
http://dx.doi.org/10.1055/s-0035-1560662.
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References and Notes
(6) Xu, J.-H.; Jiang, Q.; Guo, C.-C. J. Org. Chem. 2013, 78, 11881.
(7) Denton, W. I.; Bishop, R. B.; Caldwell, H. P.; Chapman, H. D. Ind.
Eng. Chem. 1950, 42, 796.
(1) (a) Kleemann, A.; Engel, J.; Kutscher, B.; Reichert, D. Pharmaceu-
tical Substances: Syntheses, Patents, Applications; Thieme: Stutt-
gart, 2001, 4th ed.. (b) Sundermeier, M.; Zapf, A.; Beller, M.;
Sans, S. Tetrahedron Lett. 2001, 42, 6707. (c) Miller, J. S.;
Manson, J. L. Acc. Chem. Res. 2001, 34, 563. (d) Smith, M. B.;
March, J. Advanced Organic Chemistry: Reactions, Mechanisms,
and Structure; Wiley: Hoboken, 2007, 6th ed.. (e) Fleming, F. F.;
Yao, L.; Ravikumar, P. C.; Funk, L.; Shook, B. C. J. Med. Chem.
2010, 53, 7902.
(2) (a) The Chemistry of the Cyano Group; Rappoport, Z., Ed.; Wiley:
London, 1970. (b) Larock, R. C. Comprehensive Organic Transfor-
mations; Wiley-VCH: New York, 1989, 819. (c) Ju, Y.; Liu, F.; Li,
C. Org. Lett. 2009, 11, 3582. (d) Qiao, J. X.; Cheng, X.; Modi, D. P.;
Rossi, K. A.; Luettgen, J. M.; Knabb, R. M.; Jadhav, P. K.; Wexler,
R. R. Bioorg. Med. Chem. Lett. 2005, 15, 29.
(8) Chow, Y. L. J. Am. Chem. Soc. 1965, 87, 4642.
(9) Zong, X.; Zheng, Q.-Z.; Jiao, N. Org. Biomol. Chem. 2014, 12, 1198.
(10) Chiba, S.; Zhang, L.; Ang, G. Y.; Hui, B. E.-Q. Org. Lett. 2010, 12,
2052.
(11) General Procedure for the Preparation of Aromatic Nitriles –
Typical Procedure for Compound 2a
To the mixture of 1a (190 mg, 1.0 mmol), TMSN3 (222 mg, 2.5
mmol), NBS, K3PO4·3H2O (251 mg, 2.0 mmol) in MeCN (2.0 mL)
was added Co-ZSM-5-M (50 mg) in one portion at r.t. The reac-
tion mixture was heated to 80 °C and stirred for 2 h, until the
substrate 1a was consumed as indicated by TLC. The solvent
was removed under reduced pressure, and the residue was puri-
fied by flash column chromatography (eluent: PE–EtOAc, 30:1)
to afford product 2a (99 mg, 86% yield).
(3) (a) Fatiadi, A. J. Preparation and Synthetic Applications of Cyano
Compounds; Wiley: New York, 1983. (b) Larock, R. C. Compre-
hensive Organic Transformations; VCH: New York, 1989.
4-Methoxybenzonitrile (2a)
1H NMR (500 MHz, CDCl3): δ = 7.59 (d, J = 9.0 Hz, 2 H), 6.96 (d,
J = 9.0 Hz, 2 H), 3.86 (s, 3 H). 13C NMR (125 MHz, CDCl3):
δ = 162.8, 133.9, 119.1, 114.7, 103.9, 55.5.
(4) (a) Chen, X.; Hao, X.-S.; Goodhue, C. E.; Yu, J.-Q. J. Am. Chem. Soc.
2006, 128, 6790. (b) Jia, X.; Yang, D.; Zhang, S.; Cheng, J. Org.
Lett. 2009, 11, 4716. (c) Yeung, P.; So, C.; Lau, C.; Kwong, F.
Angew. Chem. Int. Ed. 2010, 49, 8918. (d) Reddy, B.; Begum, Z.;
Reddy, Y.; Yadav, J. Tetrahedron Lett. 2010, 51, 3334. (e) Liskey,
C.; Liao, X.; Hartwig, J. J. Am. Chem. Soc. 2010, 132, 11389.
(f) Ren, Y.; Liu, Z.; He, S.; Zhao, S.; Wang, J.; Niu, R.; Yin, W. Org.
Process Res. Dev. 2009, 13, 764. (g) Do, H.; Daugulis, O. Org. Lett.
2010, 12, 2517. (h) Tajima, T.; Nakajima, A. J. Am. Chem. Soc.
4-Propoxybenzonitrile (2c)
1H NMR (500 MHz, CDCl3): δ = 7.56 (d, J = 9.0 Hz, 2 H), 6.94 (d,
J = 9.0 Hz, 2 H), 3.96 (t, J = 6.5 Hz, 2 H), 1.89–1.76 (m, 2 H), 1.04
(t, J = 7.5 Hz, 3 H). 13C NMR (125 MHz, CDCl3): δ = 162.4, 133.9,
119.2, 115.1, 103.6, 69.8, 22.3, 10.3.
4-(Cyclopentyloxy)benzonitrile (2d)
1H NMR (500 MHz, CDCl3): δ = 7.56 (d, J = 9.0 Hz, 2 H), 6.91 (d,
J = 9.0 Hz, 2 H), 4.84–4.73 (m, 1 H), 1.98–1.88 (m, 2 H), 1.88–
1.74 (m, 4 H), 1.70–1.57 (m, 2 H). 13C NMR (125 MHz, CDCl3): δ
= 150.5, 149.9, 146.9, 124.0, 121.6, 64.1, 55.6, 51.2, 34.5.
© Georg Thieme Verlag Stuttgart · New York — Synlett 2016, 27, 221–224