Synthesis of tetrahydro-4H-indol-4-one derivatives catalyzed by carbonaceous material

Article abstract of DOI:10.1016/j.catcom.2014.12.026

An efficient, high yielding method has been developed for the synthesis of diversity tetrahydro-4H-indol-4-one derivatives via a three component, one pot domino reaction from cyclohexane-1,3-diones, amines and nitrostyrenes using carbon functionalized with sulfonic acid group carbonaceous material as catalyst for the first time. The reaction was carried out in water, affording good to excellent yields in short time. The advantages of atom and step economy, green, and scope make this reaction a powerful tool for assembling heterocyclic scaffolds of general chemical and biomedical interest.

Full text of DOI:10.1016/j.catcom.2014.12.026

Catalysis Communications 62 (2015) 6–9
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Catalysis Communications
journal homepage: www.elsevier.com/locate/catcom
Short communication
Synthesis of tetrahydro-4H-indol-4-one derivatives catalyzed by
carbonaceous material
⁎
⁎
Chunmei Li, Xuezheng Liang, Furen Zhang , Chenze Qi
Zhejiang Key Laboratory of Alternative Technologies for Fine Chemicals Process, Shaoxing University, Shaoxing, Zhejiang Province 312000, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 30 October 2014
Received in revised form 29 December 2014
Accepted 30 December 2014
Available online 2 January 2015
An efficient, high yielding method has been developed for the synthesis of diversity tetrahydro-4H-indol-4-one
derivatives via a three component, one pot domino reaction from cyclohexane-1,3-diones, amines and
nitrostyrenes using carbon functionalized with sulfonic acid group carbonaceous material as catalyst for the
first time. The reaction was carried out in water, affording good to excellent yields in short time. The advantages
of atom and step economy, green, and scope make this reaction a powerful tool for assembling heterocyclic scaf-
folds of general chemical and biomedical interest.
Keywords:
Synthesis
© 2014 Elsevier B.V. All rights reserved.
Water
Tetrahydro-4H-indol-4-one derivatives
Carbonaceous material
Multi-component reaction
1. Introduction
Recently, we developed an efficient and mild method for the synthe-
sis of tetrahydro-4H-indol-4-one derivatives with cyclohexane-1,3-
Since the pioneering work of Scharff who opened up the field of ‘new
forms of carbonaceous materials’ [1] e.g. fullerenes [2] and carbyne-like
one-dimensional structures [3], tremendous advances have been
achieved with wide variety of applications, which include adsorbents,
catalysts [4], electrode materials [5], stationary phases in liquid chroma-
tography [6], and so on. Recently, sulfonated carbonaceous materials
have received more and more attention for their potential substitute
for the traditional homogeneous acid catalysts [7–11]. Very recently, a
novel carbon functionalized with sulfonic acid group carbonaceous ma-
terial (C–SO3H) has been synthesized by our group using one-step hy-
drothermal carbonization of furaldehyde and hydroxyethylsulfonic
acid aqueous solution [12]. The sulfonic acid groups were introduced
to the carbonaceous material during the carbonization process (Fig. 1).
Furthermore, the carbonaceous material showed comparable catalytic
activities to Brønsted acid in esterification and oxathioketalization [12].
Organic synthesis in water is a rapidly growing area of research in
modern organic chemistry since it holds great promise for the future
in terms of the cheaper and less hazardous production of chemicals
[13–15]. It is clear that for the full potential of water as reaction solvent
to be realized aqueous metal catalysts are required that can at least
match the efficacy of traditional metal catalysts developed for non-
aqueous media [16–19]. Accordingly, we began an investigation aimed
at developing carbonaceous material catalysts for synthesis in water.
diones, amines and (E)-(2-nitroprop-1-en-1-yl)benzenes catalyzed by
L-proline [20]. Besides aryl-substituted amines, alkyl-substituted
amines also could be applied in this transformation, providing variation
on the C-1 position of tetrahydro-4H-indol-4-one derivatives. In addi-
tion, this reaction could proceed well and be applied to various available
(E)-(2-nitroprop-1-en-1-yl)benzenes, giving different choices of sub-
stituents on the C-3 position. However, under the similar conditions,
(E)-(2-nitrovinyl)benzenes, which could give different choices of sub-
stituents on the C-2 position, did not work well with cyclohexane-1,3-
diones and amines. Following our interest in the field, we decided to
investigate the possibility of synthesis of tetrahydro-4H-indol-4-one de-
rivatives under heterogeneous conditions with (E)-(2-nitrovinyl)
benzene.
2. Experimental
All reagents were commercial products without further purification,
unless otherwise stated. Analytical thin layer chromatography (TLC)
was performed using Merck silica gel GF254 plates. Flash column chro-
matography was performed on silica gel (200–300 mesh). Melting
points were measured on an X-4 melting point apparatus. 1H NMR spec-
tra were recorded on a 400 MHz instrument (Bruker Avance 400 Spec-
trometer). Chemical shifts (δ) are given in ppm relative to TMS as the
internal reference, with coupling constants (J) in Hz. 13C NMR spectra
were recorded at 100 MHz. Chemical shift were reported in ppm with
the internal chloroform signal at 77.0 ppm as a standard. Elemental
analysis was carried out on EuroEA elemental analyzer. ESI-MS was
⁎
Corresponding authors.
E-mail addresses: frzhang@usx.edu.cn (F. Zhang), qichenze@usx.edu.cn (C. Qi).
http://dx.doi.org/10.1016/j.catcom.2014.12.026
1566-7367/© 2014 Elsevier B.V. All rights reserved.

C. Li et al. / Catalysis Communications 62 (2015) 6–9
7
Table 1
Optimization of the reaction conditions.a
Fig. 1. The synthesis of the carbon functionalized material with sulfonic acid groups.
Entry
Solvent
Catalyst (mg)
T (°C)
Time (h)
Yield (%)b
1
2
3
4
5
6
7
8
MeOH
EtOH
THF
C7H8
DMF
C–SO3H (10)
C–SO3H (10)
C–SO3H (10)
C–SO3H (10)
C–SO3H (10)
C–SO3H (10)
C–SO3H (10)
C–SO3H (10)
C–SO3H (10)
C–SO3H (10)
C–SO3H (10)
HOAc (10)
TFA (10)
p-TsOH (10)
H2SO4 (10)
Amberlyst-15 (10)
Zeolite (10)
C–SO3H (20)
C–SO3H (5)
C–SO3H (3)
50
50
50
50
50
50
30
40
60
70
80
50
50
50
50
50
50
50
50
50
6
6
6
6
6
85
75
79
67
56
89
42
73
89
85
84
37
21
45
35
50
13
90
71
33
determined by using the LCQ Fleet HPLC/MS instrument (Thermo
Finnigan). HRMS (ESI) was measured with a Bruker Daltonics APEXII
instrument.
Water
Water
Water
Water
Water
Water
Water
Water
Water
Water
Water
Water
Water
Water
Water
6
2.1. Synthesis and property of the carbonaceous material
24
24
6
6
6
6
6
6
6
6
6
6
12
12
9
According to literature method [12], the mixture of the 10 g
furaldehyde, 5 g hydroxyethylsulfonic acid and 80 mL deionized water
was placed in 100 mL Teflon-lined stainless steel autoclaves, which
were heated in an oven at 200 °C for 5 h. The resulting products were
filtered, washed with water and methanol, and dried in a vacuum
oven at 110 °C for 5 h. The acidity of the carbonaceous material was
2.4 mmol/g, which was determined through the neutralization titration.
This carbonaceous material owned much higher acidity than that of the
sulfonated carbonaceous materials, which were obtained via the sulfo-
nation of the inactive carbon. The acid strength of the catalyst was de-
termined by thermodesorption of chemisorbed ammonia (NH3-TPD).
The result showed that the catalyst had great acid strength in which am-
monia was desorbed at 400 to 600 °C.
10
11
12
13
14
15
16
17
18
19
20
a
Reaction conditions: 1a (0.50 mmol), 2a (0.50 mmol), 3a (0.50 mmol), catalyst (X mg),
and solvent (3.0 mL).
b
Isolated yields.
2.2. The preparation of tetrahydro-4H-indol-4-one derivatives 4
carbonaceous material. Next, the effect of catalyst loading on the reac-
tion was evaluated in water. Similar reactions were attempted in the
presence of 3, 5 and 20 mg of carbonaceous material. The results from
Table 1 (entries 18–20) showed that carbonaceous material (10 mg)
was sufficient to push the reaction forward in water. Higher loading of
the catalyst (20 mg) did not improve the reaction to a great extent.
In a 10-mL reaction vial, nitroolefin (0.5 mmol), cyclohexane-1,3-
dione (0.5 mmol), amine (0.5 mmol), carbonaceous material (10 mg)
and water (3.0 mL) were mixed and then capped. The mixture was
stirred for a given time (Table 2) at 50 °C. Upon completion as shown
by TLC monitoring, the reaction mixture was cooled at room tempera-
ture and exacted with ethyl acetate (5 mL × 3). The resulting residue
was purified by column chromatography on silica gel with the eluent
(ethyl acetate/petroleum ether = 1:20–1:5) to give the pure product.
3.2. Reaction scope of substrates
With the optimal reaction conditions established, we next investi-
gated the substrate scope of the reaction by employing a variety of
nitroolefins and amines. The results are summarized in Table 2. As re-
vealed in Table 2, a range of invaluable tetrahydro-4H-indol-4-one de-
rivatives can be synthesized in good to excellent yields. Firstly, the
different aromatic amines and aliphatic amines were employed to
react with 5,5-dimethylcyclohexane-1,3-dione (1a) and (E)-(2-
nitrovinyl)benzene (3a). To our delight, these reactions proceeded
smoothly to give tetrahydro-4H-indol-4-one derivatives in good
to excellent yields (Table 2, entries 1–9). Then, we employed
dimethylcyclohexane-1,3-dione (1a) and aniline (2a) as model sub-
strates and examined various different nitroolefins. The results indicate
that a wide range of substituted groups of nitroolefins all gave the de-
sired products in good to excellent yields, which include fluoro, chloro,
bromo, methyl, or methoxy groups (Table 2, entries 10–16). It is worth
noting that less reactive heterocyclic nitroolefin such as (E)-2-(2-
nitrovinyl)thiophene (Table 2, entry 17) still displayed high reactivity
and led to tetrahydro-4H-indol-4-one derivative with excellent yield
(90%). Finally, with a broad scope of nitroolefins and amines examined,
our attention turned to using other ketones, such as cyclohexane-1,3-
dione (1b). When cyclohexane-1,3-dione (1b) was used under the op-
timized conditions with different amines and nitroolefins, the reactions
also could be carried out smoothly to give the desired products with
high yields (Table 2, entries 18–21). In addition, the substrate scope of
this transformation was further investigated and a variety of (E)-(2-
3. Results and discussion
3.1. Optimization of the reaction conditions
In order to find an efficient and sustainable method to synthesize
tetrahydro-4H-indol-4-one derivatives, various reaction conditions
were investigated, including solvent, temperature and catalysts. To
choose the optimum solvent, the reaction of 5,5-dimethylcyclohexane-
1,3-dione (1a), 4-chloroaniline (2a) and (E)-(2-nitrovinyl)benzene
(3a) was examined in the presence of carbonaceous material (10 mg)
at 50 °C in different solvents, such as MeOH, EtOH, THF, toluene and
DMF. The results of the screening of solvents are presented in Table 1
(entries 1–6). As shown in Table 1, the reaction in water gave the best re-
sults (Table 1, entry 6). Moreover, to further optimize the reaction tem-
perature, the reaction was carried out in water at the temperature
ranging from 30 °C to 80 °C with an increment of 10 °C. As shown in
Table 1, when the temperature was increased from 30 °C to 50 °C, the
yield of product 4 improved from 42% to 89% (entries 6–11). However,
no significant increase in the yield of product 4 was observed as the reac-
tion temperature was raised from 60 °C to 80 °C. Therefore, the temper-
ature of 50 °C was chosen for all further reactions.
For further screening of the reaction conditions, several catalysts
were evaluated for their catalytic efficiency in the reaction (Table 1, en-
tries 12–17). However, none of the tested catalysts proved better than

8
C. Li et al. / Catalysis Communications 62 (2015) 6–9
Table 2
activities were investigated through the model reaction of 5,5-
Reaction scope of substrates.a
dimethylcyclohexane-1,3-dione (1a), 4-chloroaniline (2a) and (E)-(2-
nitrovinyl)benzene (3a) carefully. The yields remained almost un-
changed even after the catalyst had been recycled for six times (Fig. 2).
3.4. Mechanism for the domino reaction
Entry
4
R1
R2
R3
R4
Time Yield Mp (°C)
(h)
(%)b
The carbonaceous material (C–SO3H) has been successfully used as
acidic catalyst for the esterification of acetic and butanol and the
oxathioketalization of cyclohexanone and mercaptoethanol [12]. The
domino reaction of cyclohexane-1,3-diones, amines and nitrostyrenes
follows the regular mechanism of acid-catalyzed condensations [22,
23]. We assumed that the mechanism of the domino reaction probably
involves the reaction of C–SO3H with the cyclohexanone by acting as an
acid and playing a complex role in promoting the imine-enamine
tautomerization to give radical intermediate [20] as shown in
Scheme 2. It is conceivable that, the initial event is the formation of
enaminones B from an activated A and an amine 2. The intermediate
B further undergoes a conjugate addition of the nitroolefin 3 to
1
2
3
4
5
6
7
8
4a
4b
4c
Me 4-ClC6H4
Me 2-MeC6H4
Me 2-OMeC6H4 C6H5
C6H5
Me 1-Naphthyl C6H5
Me 2-Naphthyl C6H5
Me Bn
C6H5
C6H5
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
Me
6
6
6
8
8
8
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
89
86
86
77
89
81
90
88
87
86
88
81
81
90
91
83
90
88
91
84
83
85
77
80
81
82
Oil
Oil
Oil
Oil
Oil
Oil
Oil [21]
Oil
75–76
106–108
Oil
Oil
Oil
Oil
Oil
Oil
98–100
Oil
Oil
Oil
Oil
138–140 [20]
110–112 [20]
116–118 [20]
128–130 [20]
124–126 [20]
4d Me 2-OHC6H4
4e
4f
4g
C6H5
C6H5
C6H5
4h Me (CH2)4Me
4i
4j
4k Me C6H5
4l Me C6H5
4m Me C6H5
4n Me C6H5
9
Me Cy
Me C6H5
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
4-FC6H4
4-BrC6H4
4-MeC6H4
4-OMeC6H4
2-ClC6H4
2,4-ClC6H3
2,6-ClC6H3
2-Thienyl
C6H5
give intermediate C. Intermediate
C undergoes imine-enamine
4o
Me C6H5
tautomerization to give radical intermediate D and C–SO3H. Finally, in-
tramolecular cyclization followed by elimination of H2O and HNO from
the intermediate E afford the desired product 4.
4p Me C6H5
4q
4r
4s
4t
4u
4v
Me C6H5
H
H
H
H
C6H5
2-MeC6H4
2-OMeC6H4 C6H5
Cy
C6H5
4. Conclusions
C6H5
C6H5
4-NO2C6H4 Me
Me C6H5
4w Me C6H5
In conclusion, a novel, mild, and environmentally-friendly, one pot
4x
4y
4z
Me 4-ClC6H4
C6H5
1-Naphthyl C6H5
2,4-MeC6H3 C6H5
Me
Me
Me
synthetic protocol was developed for obtaining
a variety of
H
H
tetrahydro-4H-indol-4-one derivatives directly from cyclohexane-1,3-
diones, anilines and nitroolefins in aqueous medium in the presence
of carbonaceous material. This system could be applied to various avail-
able substrate synthetic procedures in good to excellent yields. There-
fore, this work not only provides plenty of novel tetrahydro-4H-indol-
4-one compounds with structural diversity for further bioassay, but
also enriches the research contents of carbonaceous material fields.
a
Reaction conditions: 1 (0.50 mmol), 2 (0.50 mmol), 3 (0.50 mmol), carbonaceous ma-
terial (10 mg) and water (3.0 mL).
b
Isolated yields.
nitroprop-1-en-1-yl)benzenes was also found to be suitable for this
multicomponent reaction (Table 2, entries 22–26).
In addition, our attention focused on finding further application of
this catalytic system. Inspired by the structural similarity between
the nitrostyrene derivatives and bromonitrostyrene derivatives,
we envisaged that the reaction between bromonitrostyrenes, 5,5-
dimethylcyclohexane-1,3-dione and amines to give tetrahydro-4H-
indol-4-one derivatives could take place using the same catalytic sys-
tem. To our delight, the tetrahydro-4H-indol-4-one derivatives also
could be given with bromonitrostyrenes instead of nitrostyrenes
under the similar cascade process but with different yields (Scheme 1).
Acknowledgments
We are grateful for the financial support from the Research Funds of
Shaoxing University (no. 2013LG1005) and the Natural Science Founda-
tion of Zhejiang Province (no. LQ13B020002). We are also grateful to
Wenzhou University for the help of HRMS analysis.
Appendix A. Supplementary data
3.3. The recycle of carbonaceous material
Supplementary data to this article can be found online at http://dx.
doi.org/10.1016/j.catcom.2014.12.026.
One property of carbonaceous material is the reusability. The recov-
ery of the catalyst was very convenient. After reactions, the reaction
mixture was filtered with MeOH and water and the solid, dried in vacu-
um oven at 120 °C for 4 h, could be reused easily. The recovered
Scheme 1. Synthesis of compounds 4 with (Z)-bromonitrostyrenes.
Fig. 2. The recycle of the carbonaceous material.

C. Li et al. / Catalysis Communications 62 (2015) 6–9
9
Scheme 2. Proposed mechanism for the domino reaction catalyzed by carbonaceous material.
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