Synthesis of bis(indolyl)methanes under dry grinding conditions, promoted by a Lewis acid-surfactant-SiO2-combined nanocatalyst

Article abstract of DOI:10.1039/c9gc01073d

An in situ developed Lewis acid-surfactant-SiO₂-combined (LASSC) nanocatalyst was used, for the first time, as a green and effective promoting medium for the electrophilic activation of aldehydes under solvent-free and dry grinding conditions. The advantages of using the LASSC nanocatalyst include avoiding the generation of wastewater containing sodium dodecyl sulfate and the use of toxic reagents, excellent reusability of the catalyst, and obtaining a high yield of bis(indolyl)methanes.

Full text of DOI:10.1039/c9gc01073d

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Synthesis of bis(indolyl)methanes under dry grinding conditions,
promoted by a Lewis acid–surfactant–SiO2-combined nanocatalyst
a
a
a
a
a
a
a
Zhiqiang Wu, Gang Wang, Shuo Yuan, Dan Wu, Wanyi Liu ,* Baojun Ma,* Shuxian Bi,
Received 00th January 20xx,
Accepted 00th January 20xx
a
a
Haijuan Zhan, Xiaoyan Chen
DOI: 10.1039/x0xx00000x
An in situ developed Lewis acid–surfactant–SiO2-combined (LASSC) chemistry,5 we found that the use of solvent-free or water-free
nanocatalyst was used, for the first time, as a green and effective medium, use of photocatalysts or non-noble metal co-catalysts are
promoting medium for the electrophilic activation of aldehydes some of the methods to prevent waste and pollution.6
under solvent-free and dry grinding conditions. The advantages of
Lewis acid–surfactant-combined (LASC) catalysts have been used
7
using the LASSC nanocatalyst include avoiding the generation of in aqueous-phase organic synthesis for more than twenty years. The
wastewater containing sodium dodecyl sulfate and use of toxic catalysts act both as a Lewis acid to catalyze the reaction and as a
reagents, excellent reusability of the catalyst, and obtaining a high surfactant to solubilize the organic substrates in water. However, a
yield of bis(indolyl)methanes.
complete regeneration of the catalyst with all its original chemical
properties is difficult. Also, large amounts of organic waste liquid
containing toxic metals and surfactants produced as a result of de-
Introduction
Of late, mechanochemistry is being recognized as an environmentally emulsification and washed significantly limit the large-scale
1
friendly alternative to conventional methods. In the past decade, application of this method (The conventional catalyst preparation
mechanochemical reactions have rapidly developed in several areas methods for typical catalytic reactions and the amount of SDS and lost
2
8
of chemistry, such as organic synthesis. Reducing the use of toxic SDS used are shown in Table S1). Veisi and coworkers reported the
solvents, increasing the efficient recycling of catalysts, and low- synthesis of BIMs catalyzed by sodium dodecyl sulfate (SDS) and
energy consumption are some of the advantages of mechanochemical FeCl3·6H2O in water. The catalyst preparation and synthesis strategy
reactions. The mechanochemical approach is highly in line with the is very simple and straightforward. However, recycling of the catalyst
principles of green chemistry and is also considered to be a promising is particularly difficult. Also, thoroughly washing the solid products
3
option in solvent-free organic synthesis.
with water during post-treatment results in a large amount of
The development of bis(indolyl)methanes (BIMs) by the reaction wastewater containing SDS (the at least 350 ml of SDS toxic
of indoles with aldehydes or ketones has become very common due to wastewater was produced per 2.74 mmol of LASC catalyst), which is
4
their wide range of applications in biomedicine and agriculture.
harmful to the environment. SDS is also one of the most common
However, the synthetic methods generally have several limitations, compounds whose presence is tested for by the ASTM in the USA,
9
which include complex catalyst preparation, difficulty in recycling the using their toxicity tests. It is seen that water containing SDS is not
catalysts, use of organic solvents, generation of a large volume of only highly toxic to marine organisms but also causes periodontal
10
waste liquids, and difficulty in applying the methods on an industrial diseases in humans. Therefore, suppressing the eco-environmental
scale. Therefore, the goals of this study were to find an alternative to toxicity of SDS from the source is a chemical problem that the LASC
the existing polluting, toxic solvents and expensive reagents and to method must consider solving. Addressing the toxicity issue is one of
develop more environmentally friendly catalysts for the green the key determinants for the LASC method to achieve mass
synthesis of BIMs. Based on our previous research in the field of green production.
In addition, while evaluating the commercial potential of a catalyst,
not only the activity but also the stability of the catalyst is an essential
factor to be considered.11 One of the ideal green chemical processes
is to synthesize products without using solvents (including water) and
to recycle the catalyst efficiently. To our knowledge, there are no such
methods available for the synthesis of BIMs.
a. State Key Laboratory of High-efficiency Utilization of Coal and Green Chemical
Engineering, National Demonstration Center for Experimental Chemistry
Education, College of Chemistry and Chemical Engineering, Ningxia University,
Yinchuan 750021, P. R. China.
b. E-mail: liuwy@nxu.edu.cn ; bjma@nxu.edu.cn; Tel: 130 9951 9169.
† Electronic supplementary information (ESI) available: Segmental details of the
experimental procedures, the catalyst characterization results (HRTEM, IR, XRD, XPS,
TG, Elemental analysis), and the spectral data of the obtained compounds (IR, NMR,
and HRMS) are shown in this file. See DOI:
In this paper, a new green method for catalyzing the synthesis of
BIMs is proposed by combining Lewis acid, surfactant and SiO2
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Journal Name
components in situ to form LASSC nanometer catalyst system under (entry 3). There was no reaction when only SDS was used as the
View Article Online
DOI: 10.1039/C9GC01073D
solvent-free/solid phase grinding. We also discuss the characteristics catalyst (entry 2). The results of the SiO2-SDS-combined catalysts
of nanometer catalytic activity and the effective life cycle of the were consistent with those when SiO2 alone was used as the catalyst
LASSC nanocatalyst. In addition, the mechanism of the LASSC (entry 4). It is worth noting that the yield was 99 % in the presence of
catalytic system in indole methylation was accurately confirmed by AlCl3·6H2O–SDS–SiO2-combined catalyst (entry 10). In addition,
the capture and separation of 3-indolylalcohol.
increasing the amount of SiO2 in the LASSC catalysts is advantageous
because the yield increases (entries 8–10). Further, changing the
surfactant has little effect on the target product yield (entry 12).
Results and discussion
We started our study with the reaction between indole (1) and 4- Similarly, replacing SiO2 with Al2O3 resulted in a yield of only 42 %
nitrobenzaldehyde (2), which we considered as the model reaction, in (entry 11). As a comparison, the LASC catalytic results of different
the presence of different LASSC catalysts and under solvent-free Lewis acids in the aqueous phase show that there is a significant
grinding. After careful screening of a variety of catalysts, we difference with this method (Table S2).
established the optimum conditions for the synthesis of 3a; we found
that the combination of AlCl3·6H2O, SDS, and SiO2 (0.5 g) as the
LASSC catalyst with grinding for 20 min resulted in a 99 % yield of
the product (Table 1, entry 10).
R2
Lewis acid
SDS/SiO2
R1
R1
3a-3x
R.T, grinding
HN
NH
R2
CHO
R1
LASSC
4a-4h
+
N
microwave;
grinding
H
R2
HN
NH
R2
1
2
Fig. 1 Recycling of the LASSC catalyst for the synthesis of BIMs.
R1= -H; 2-methyl; 3-methyl.
R2= -NO2; -Br;-Cl;-CN, etc.
Recyclability and reusability of catalysts are other attributes
pertaining to their industrial applicability. Therefore, the reusability
LASSC
12
5a
microwave;
grinding
NH HN
of the catalyst in the model reaction, under optimized reaction
conditions, was evaluated (Fig. 1). It is worth noting that the recovered
catalyst could be utilized at least 10 times in subsequent reactions
without a significant loss of product yield (Fig. 1). The results show
that the LASSC catalyst has a high catalytic activity and excellent
stability, which can be attributed to the microscopic structure of the
catalyst. It is observed that the basic structure of the catalyst did not
change significantly even after 11 usages, which could be seen by
comparing the structures of the fresh and used catalysts. The tight,
cross-linked structure was still retained (HRTEM, Fig. S1), and it is
presumed that the catalytically active center remains intact. By
analyzing the infrared spectrum (Fig. S2), we observed the main
characteristic peaks of the three components in the LASSC catalyst
system did not disappear significantly even after its repeated use for
10 times (3400-3350cm-1 attributed to the absorption peak of -OH;
2850-2980cm-1 and 543-620cm-1 are attributed to the stretching
Scheme 1
Table 1. Optimization of reaction conditions
Entry a
Carrier (g) b
Yield (%) c
10
Lewis acid
Surfactant
Time (min)
1
SiO2
45
30
30
45
30
30
20
20
20
20
30
20
20
35
50
2
SDS
N.R
Trace
11
3
AlCl3· 6H2O
4
SiO2
SDS
SDS
AlCl3· 6H2O
AlCl3· 6H2O
AlCl3
5
34
6
SiO2
SiO2
SiO2
SiO2
SiO2
Al2O3
SiO2
SiO2
SiO2
SiO2
81
7
70
SDS
SDS
SDS
SDS
SDS
SDBS
SDS
SDS
SDS
8d
9e
10f
11
12
13
14
15
AlCl3· 6H2O
AlCl3· 6H2O
AlCl3· 6H2O
AlCl3· 6H2O
AlCl3· 6H2O
FeCl3· 6H2O
ZnCl2· 6H2O
MgCl2· 6H2O
75
87
99
-
vibration of -CH2 and the bending vibration of C-SO3 in the SDS,
42
respectively). The above conclusions were further verified by TGA
testing (Fig. S3). The TGA shows that the catalyst after multiple
cycles can still be stable at around 300℃ with only a small heat loss.
Compared to the fresh catalyst, the heat loss of the catalyst after 10
cycles of recycling is smaller, which also indicates that the catalyst
after multiple cycles still maintains good stability.
With the optimized conditions in hand, we investigated the
substrate scope for the synthesis of 3 by employing a variety of
aldehydes and indoles, as summarized in Table S4. To our delight,
compounds (Scheme 1, 3a–3x) containing a broad range of
substituents were formed with good to excellent yields (S4, entries 1–
14). We studied the reaction between 4-nitrobenzaldehyde and
different 6-substituted indoles to extend the universality of the
91
98
82
73
a Reaction conditions: Indole 1 (2.0 mmol); 4-nitrobenzaldehyde 2 (1.0 mmol); SDS:
sodium dodecyl sulfate (0.3 mmol); SDBS: Sodium dodecyl benzene sulphonate;
Al2O3 (Column chromatography neutralalumina); b SiO2(Column chromatography
silica gel, 300-400 mesh); c Isolated yields. R.T; Solvent-free; The ratio of lewis
acid as AlCl3· 6H2O to SDS was 1:3 ie 0.4 mmol. d,e,fThe amount of SiO2 was 0.1
g; 0.3 g; 0.5 g, respectively.
In the solvent-free grinding reaction, the yield was approximately
10 % in the presence of only SiO2 (entry 1). Similarly, a trace amount
of 3a was detected when only AlCl3·6H2O was used as the catalyst
2 | J. Name., 2012, 00, 1-3
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substrate (entries 15–24). It is apparent that the electron withdrawing
Compared with the traditional LASC catalytic sysVteiemw,Artthicele Omnalinine
DOI: 10.1039/C9GC01073D
groups of the indole compounds achieved better yields in a shorter components of the LASSC catalytic system have not changed greatly.
time (entries 15–21) when compared with their electron donating However, since the LASSC system employs silica as a cocatalyst, the
groups (entries 22–24).
catalyst system formed in situ by solid phase milling exhibits a stable
In view of the excellent data obtained above, we studied the "dry state". At the same time, the free water produced by the reaction
synthesis of indolylmethane derivatives using microwave-assisted is also one of the raw materials for the catalytic process. Firstly，this
solid-phase method (Scheme 1, 4a-4h) to further explain the is attributed to the small amount of release of the crystal water (the
versatility of the catalytic system. The results are shown in Table S3. inmobilized water) in the catalyst system by the coordination of the
It was found that the functional groups on the phenyl ring, such as – metal ions and the SDS. At the same time, free water dissolves the
NO2, –CN, –Me, –C6H5, were very well compatible with 2-methyl- SDS in the system, forming a small amount of vesicle micelle reactor,
indole and 3-methyl-indole. Even in a short period, the LASSC It has been proven to provide a good catalytic environment.7 Secondly,
catalyst obtained good yields with the microwave-assisted solid-phase with the occurrence of the reaction, a small amount of fresh free water
method (Table S3, entries 1–5 and 7). Acid-labile substrates,13 such is continuously generated until the reaction is completely completed.
as p-dimethylaminobenzaldehyde (Table S5, entry 6), also produced This part of the free water is adsorbed and dispersed into the catalyst
a good yield of the desired product. However, limitations were found system by hydrogen bonding with the silica gel. However, in the
in the reactions involving ketones, such as p-nitroacetophenone, macroscopic state, catalyst system still appears as a stable "dry state"
which are generally less reactive in the model reaction when system, which does not destroy the stability of the grinding reaction
compared with aldehydes (S5, entry 8). Besides, the reaction between catalyst system under the solid phase conditions.
N-methylindole with 4-nitro-benzaldehyde did not yield any product
In addition, when the recovered catalyst is reused, the free water
(Table S5, entry 10). It is worth noting that the interaction of 3- generated by the reaction is partially removed during the post-
methylindole with p-nitrobenzaldehyde can produce the target treatment due to the treatment by extracting or washing with ethyl
product 5a (S5, entry 9). It also embodies the advantage that the acetate and drying of the catalyst(the loss quality is 0.617 mg per time,
LASSC catalytic system is not affected by substituents other than that accounting for 2.57% of the total SDS feed ， Table S3). But, the
in the 1- position of the heterocycle.
amount of SDS and lost SDS used in the general literature report and
Further, in order to evaluate the effectiveness of the method we the amount of wastewater generated is very large (See Table S1). The
used in this study, we extended the catalytic system to another above conclusions were further verified by TGA testing (Fig. S3). By
important reaction. The synthesis of Schiff base is also applicable to elemental analysis before and after the catalyst is recycled (Table S1
the LASSC system (Scheme S3). To shorten the reaction time, the and S3), the results show that the loss of the catalyst in multiple cycles
Schiff base was synthesized using solvent-free, microwave-assisted of use is very small, and almost no toxic waste water of SDS is
solid-phase grinding of o-phenylene-diamine and p-nitrobenzal- produced.
dehyde. It is worth noting that the 1- and 2-substituted products were
In brief, the "dry state" LASSC catalytic system not only has a
obtained simultaneously in the reaction system, and the conversion of similar microreactor function in the microenvironment as in the
the raw materials was almost complete.
traditional water-phase catalyst system,but also acts as a more
In contrast, Singh et al.14 reported that ZnO nanoparticles catalysts efficient catalytic activity, stability and excellent recyclability，and
have high efficiency and selectivity in the synthesis of 1,2- effective reduction of SDS toxic wastewater generationcon.
disubstituted benzimidazoles. However, the LASSC catalytic system
The structural characteristics of the LASSC catalyst can reveal its
is simpler, easier to handle, cost-effective, and ecofriendly. Also, by unique catalytic properties. As indicated by HRTEM (Fig. 2), the
amplifying the model reaction, it was possible to obtain a gram-level morphology of the LASSC catalyst has a cross-linked fibrous
mass production using a ball mill, and the conversion rate of the raw structure and forms a composite catalytic system. And a significant
materials and the yield of the final product were almost perfect.
shaded area appears in the catalyst portion area, which is about 3-4
In summary, the LASSC catalytic system could be easily prepared nm in diameter because of the presence of surfactant microcapsules in
by in situ grinding using inexpensive AlCl3·6H2O or FeCl3·6H2O, the LASSC catalyst system formed by in situ milling (Fig. 2A and B).
SDS, and SiO2. The catalyst is more effective than other acidic In addition, the surface of the catalyst has lattice fringes with a lattice
catalysts, such as SDS and FeCl3·6H2O, in water (Table S2).8 Its spacing of approximately 0.211 nm (Fig. 2C), which is probably
unique properties make it an attractive alternative to conventional caused by the self-assembled micelle aggregates of the SDS surfactant.
organic catalysts.
So, the LASSC catalyst was primarily a micron particle with a nano
structure, which is further confirmed by the appearance of a new
crystal phase in the XRD spectra (Fig. S5). Besides, the energy-
dispersive X-ray spectroscopy (EDS) mapping indicates the presence
of related Si, Al, and Na elements in the LASSC catalytic nano-scale
microreactor (Fig. 2D). The FT-IR spectra of the LASSC catalytic
system confirmed that the catalytic reaction is carried out in the form
-
of a group in which –Si–O–Al–, –Si–OH, –Al–OH, and C-SO3
coexist, as shown in Fig. S4. The three components of the LASSC
catalytic system form a limited range of microreactors with
catalytically active center play a mutually assisted catalytic role as
described above.
Fig.
2
HRTEM (A, B, and C) and EDS mapping (D) of the LASSC.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
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H
H
O
H
H
O
H
O
H
O
H
O
H
O
H
O
H
N
H
carbonyl group by hydrogen bonding to form a carbocation and an
DOI: 10.1039/C9GC01073D
electron. This step is key for the reaction to proceed. Second, the
O
O
Cl
H
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H
H
H
H
H
+
H
O
O
H
+
H
O
H
O
H
NH
Si Si Si Si Si Si
O
Cl Cl
H
H
O
Al
O
H
R
Cl
deprotonation of the coordinated indole results in a negative electron
center at its C-3 position, followed by the formation of a tertiary
alcohol intermediate (Marked as A, Fig. S7). In the third step, the
catalytic cycle is accomplished by exchange with additional indole
protons and releases the target product, water, and the catalyst.
O
Cl
O
Cl
Si Si
Si Si
Si Si
G
L
A
S
S
C
r
i
n
NH
d
i
n
g
H
H
N
O
IV
R
I
H
NH
O
R
H
-
HN
SO
=
=
3
Step. 3
Conclusions
C12H25ONa+
R
R
H
NH
H
In conclusion, the LASSC catalytic system has proven to be cheap,
green, and effective in promoting the electrophilic activation of
aldehydes. Its unique properties make it an attractive alternative
to conventional organic catalysts. When compared with the
reported acid catalytic systems, the LASSC catalyst not only makes
product separation easier but also shows higher catalytic activity,
stability, and ecofriendliness, because of the following main factors:
(i) avoidance of the use of solvent and the cumbersome processing of
the catalyst post-treatment; (ii) the presence of a cross-linked
nanofibrous structure as a result of in situ grinding; (iii) the solventless
grinding and multiple lifecycles reduce the production of wastewater
containing SDS, which, to some extent, solves environmental
problems. We anticipate that the method presented here will soon find
great utility in the field of synthetic chemistry, enabling the green
synthesis of other heterocyclic compounds.
O
H
L
A
R
H
O
S
S
C
N
N
H
N
L
Step. 2
A
S
H
H
H
H
A
S
C
H
R
O
N
O
H
O
H
H
H
O
O
H
H
H
O
O
H
O
Cl
Cl
H
O
Cl
O
Al
O
Si Si
Si Si
Si Si
Cl
Cl
O
O
Cl
R
H
Si Si
Si Si
Si
Si
NH
H
HO
N
H
H
H
H
III
O
II
H
O
H
O
Al
O
Cl
Cl
O
O
Cl
Si Si
Si Si
Si Si
Scheme 2 Schematic of the three-component relationship among the
components of the LASSC catalytic system and the catalytic reaction mechanism.
To further prove the interrelationship between the three
components of the LASSC catalytic system, Scheme 2 is proposed
through experimental data, which also reveal an accurate reaction
mechanism with the capturing of the 3-indolylalcohol moiety. First,
only silica is involved in the reaction at room temperature (Table 1,
entry 1). We obtained the intermediate of 3-indolylalcohol, indicating
that SiO2 not only plays a role in dispersion but more importantly in
Conflicts of interest
There are no conflicts to declare.
Acknowledgments
15
the catalysis. This is the first time the reaction rate has been delayed
This work was financially supported by the Major Innovation Projects
for Building First-class Universities in China’s Western Region (No.
ZKZD2017003), the National First-rate Discipline Construction
Project of Ningxia (No. NXYLXK2017A04) and the National Natural
Science Foundation of China (No. 21862013, No. 21768003 and No.
21862014). Thanks to the National Chemical Experiment Teaching
Demonstration Center of Ningxia University. We thank LetPub for its
linguistic assistance during the preparation of this manuscript.
to obtain a tertiary alcohol-type indole intermediate. A similar method
shows that SDS does not have any catalytic effect, while crystalline
aluminum chloride has weak catalytic properties (Table 1, entries 2
and 3). That is, while both SiO2 and AlCl3·6H2O contain hydroxyl
groups and exhibit catalytic properties, SDS does not. Second, the Al
atom in the AlCl3·6H2O crystal is located at the center of the regular
octahedron, which makes it easy to form coordinate bonds, thus
enabling the compound to exhibit catalytic properties. Next, this study
indicates that an increase in the number of hydroxyl groups can
significantly increase the catalytic activity (Table 1, entries 4–6). By
grinding the three components, first, the hydroxyl groups on the
surface of silica and AlCl3·6H2O are dehydrated by hydrogen bonding
to form –Si–O–Al– groups, which play a major catalytic role. Second,
AlCl3·6H2O and SDS form a complex, merging into molecular
aggregates, which aids in auxiliary catalysis. Whether aluminum
chloride contains water is important for catalyzing this reaction. The
presence or absence of the -Si-O-Al active site is also critical to an
efficient reaction (Table 1, entries 7 and 11). However, the change in
the surfactant did not significantly change the exposure and increase
the number of catalytically active sites (Table 1, entry 12). Thus, we
confirmed that the LASSC catalytic system coexists as a composite
with –Si–O–Al–, –Si–OH, –Al–OH groups and the (SDS)3Al
component, which is also confirmed by XPS characterization (Fig.
S6).
References
1
(a) R. B. N. Baig, R. S.Varma, Chem. Soc. Rev, 2012, 41,1559. (b) T. K.
Achar, A. Bose, P. Mal, Beilstein. Jorg. Chem, 2017, 13,1907. (c) D. Tan, T.
Friščić, Eur. J. Org. Chem, 2018, 2018, 18. (d) V. Štrukil, Synlett, 2018,
29,1281.
2
(a) T. Raj, H. Sharma, A. Singh, T. Aree, N. Kaur, N. Singh, D. O. Jang, ACS.
Sustain. Chem. Eng, 2017, 5, 1468. (b) G. W. Wang, Chem. Soc. Rev, 2013, 42,
7668. (c) G. N. Hermann, C. L. Jung, C. Bolm, Green. Chem, 2017, 19, 2520.
(d) C. Bolm, R. Mocci, C. Schumacher, M. Turberg, F. Puccetti, J. G. J. G.
Hernández, Angew. Chem. Int. Edit, 2018, 130, 2447.
3
4
(a) H. Sharma, N. Singh, D. O. Jang, Green. Chem, 2014, 16, 4922. (b) A. D.
Kreuder, T. H. Knight, J. Whitford, E. Ponnusamy, P. Miller, N. Jesse, R.
Rodenborn, S. Sayag, M. Gebel, I. Aped, I. Sharfstein, E. Manaster, I. Ergaz, A.
Harris, L. N. Grice, ACS. Sustain. Chem. Eng. 2017, 5, 2927. (c) M.
Tobiszewski, A. Mechlińska, J. Namieśnik, Chem. Soc. Rev. 2010, 39, 2869.
(a) S. R. Mendes, S. Thurow, F. Penteado, M. S. D. Silva, R. A. Gariani, G.
Perin, E. J. Lenardão, Green. Chem, 2015, 17,4334. (b) S. Imran, M. Taha, N.
H. Ismail, S. Fayyaz, K. M. Khan, M. I. Choudhary, Bioorg. Chem, 2016, 68,
90. (c) C. Grosso, A. L. Cardoso, A. Lemos, J. Varela, M. J. Rodrigues, L.
In short, a concise and reasonable reaction mechanism is proposed
for the reaction catalyzed by the LASSC catalyst (Scheme 2). When a
catalytic reaction occurs, first, the catalytically active site activates the
4 | J. Name., 2012, 00, 1-3
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Custódio, L. Barreira, T. M. V. D. P. Melo, Eur. J. Med. Chem, 2015, 93, 9. (d)
T. Abe, S. Nakamura, R. Yanada, T. Choshi, S. Hibino, M. Ishikura, Org. Lett,
2013, 15, 3622. (e) R. Tayebee, M. M. Amini, F. Nehzat, O. Sadeghi, M.
Aramaghan, J. Mol Catal A-Chem, 2013, 366, 140.
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DOI: 10.1039/C9GC01073D
5
6
7
(a) B. J. Ma, X. Y. Wang, K. Y. Lin, J. Li, H. J. Zhan, W. Y. Liu, Int. J.
Hydrogen. Energ, 2017, 42, 18977. (b) B. J. Ma, H. J. Xu, K. Lin, J. Li, H. J.
Zhan, W. Y. Liu, C. Li, ChemSusChem, 2016, 9, 820. (c) B. J. Ma, H. Xie, J. Li,
H. J. Zhan, K. Y. Lin, W. Y. Liu, J. Mol. Catal. A- Chem, 2016, 420 , 290.
(a) G. Paggiola, A. J. Hunt, C. R. McElroy, J. Sherwood, J. H. Clark, Green.
Chem, 2014, 16, 2107. (b) C. J. Li, L. Chen, Chem. Soc. Rev, 2006, 35, 68. (c)
N. Azizi, L. Torkian, M. R. Saidi. J. Mol. Catal. A-Chem, 2007, 275, 109. (d)
H. Hikawa, H. Suzuki, Y. Yokoyama, I. Azumaya, Catalysts, 2013, 3, 486.
(a) S. Kobayashi, T. akabayashi. Tetrahedron. Lett, 1998, 39, 5389. (b) K.
Manabe, Y. Mori, T. Wakabayashi, S. Nagayama, S. Kobayashi, J. Am. Chem.
Soc, 2000, 122, 7202. (c) K. Manabe, S. Kobayashi. Chem. Commun, 2000, 8,
669. (d) G. F.Ghesti, J. L. D.Macedo, V. C. I. Parente, J. A. Dias, S. C. L. Dias.
Appl. Catal. A-Gen, 2009, 355, 139. (e) I. V. Vasilenko, H. Y. Yeong, M.
Delgado, S. Ouardad, F. Peruch, B. Voit, F. Ganachaud, S. V. Kostjuk. Angew.
Chem. Int. Edit, 2015, 54, 12728. (f) I. V. Vasilenko, F. Ganachaud, S. V.
Kostjuk. Macromolecules, 2016, 49, 3264.
8
9
H. Veisi, B. Maleki, F. H. Eshbala, H. Veisi, R. Masti, S. S. Ashrafi, M.
Baghayeri, RSC. Adv, 2014, 4, 30683.
L. Mariani, D. D. Pascale, O. Faraponova, A. Tornambè, A. Sarni, S.
Giuliani, G. Ruggiero, F. Onorati, E. Magaletti. Environ. Toxicol, 2006, 21,
373.
10 (a) N. Liu, Z. H. Wu, Ecotox. Environ. Safe, 2018, 163, 188. (b) L. Feng, J.
T. Liu, J. H. Wang, B. G. Wang, S. J. Song, J. Inorg. Mater, 2006, 21, 972.
11 C. Hammond. Green. Chem, 2017, 19, 2711.
12 V. P. Jejurkar, C. K. Khatri, G. U. Chaturbhuj, S. Saha, ChemistrySelect, 2017,
2, 11693.
13 F. He, P. Li, Y. L. Gu, G. X. Li, Green. Chem, 2009, 11, 1767.
14 H. Sharma, N. Kaur, N. Singh N, D. O. Jang, Green. Chem, 2015, 17, 4263.
15 (a) N. Li, G. W. Huber. J. Catal, 2010, 270, 48. (b) J. F. Yang, S. S. Li, L. L.
Zhang, X. Y. Liu, J. H. Wang, X. L. Pan, N. Li, A. Q. Wang, Y. Cong, X. D.
Wang, T. Zhang, Appl Catal B-Environ, 2017, 201, 266. (c) M. X. Li, G. Y.
Li, N. Li, A. Q. Wang, W. j. Dong, X. D. Wang, Y. Cong, Chem. Commun,
2014, 50, 1414.
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Green Chemistry
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DOI: 10.1039/C9GC01073D
Graphic Abstract
Synthesis of bis(indolyl)methanes under dry grinding conditions, promoted by a
Lewis acid–surfactant–SiO2-combined nanocatalyst
Zhiqiang Wu,a Gang Wang,a Shuo Yuan,a Dan Wu,a Wanyi Liu ,*a Baojun Ma,*a
Shuxian Bi,a Haijuan Zhan,a Xiaoyan Chena
The Lewis acid-surfactant-SiO2- combined (LASSC) nanocatalyst synthesize BIMs, which has the advantages of
being non-toxic, multi-cycle, high-stability and efficient.