An efficient synthesis of bis(indolyl) methanes and N,N′-alkylidene bisamides by Silzic under solvent free conditions

Article abstract of DOI:10.1016/j.cclet.2015.11.013

An operationally simple and green method for the synthesis of a wide range of bis(indolyl)methanes, and N,N′-alkylidene bisamides under mild conditions, with excellent yields using Silzic, has been developed. This improved method furnishes in good yields bis(indolyl)methanes derivatives starting from indole and aldehydes, or ketones, and N,N′-alkylidene bisamides derivatives starting from acetamide and aldehydes. The catalytic system was reused up to three times with the same efficiency.

Full text of DOI:10.1016/j.cclet.2015.11.013

Accepted Manuscript
Title: An efficient synthesis of bis(indolyl) methanes and N,
N’-alkylidene bisamides by Silzic under solvent free
conditions
Author: Hanan A. Soliman Ahmed Y. Mubarak Saad S.
Elmorsy
PII:
S1001-8417(15)00434-9
DOI:
Reference:
http://dx.doi.org/doi:10.1016/j.cclet.2015.11.013
CCLET 3490
To appear in:
Chinese Chemical Letters
Received date:
Revised date:
Accepted date:
17-8-2015
12-11-2015
16-11-2015
Please cite this article as: H.A. Soliman, A.Y. Mubarak, S.S. Elmorsy, An
efficient synthesis of bis(indolyl) methanes and N, N’-alkylidene bisamides
by Silzic under solvent free conditions, Chinese Chemical Letters (2015),
http://dx.doi.org/10.1016/j.cclet.2015.11.013
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Graphical Abstract
An efficient synthesis of bis(indolyl)methanes and N, N'-alkylidene bisamides by
Silzic under solvent free conditions
Hanan A. Soliman*a, Ahmed Y. Mubarak b, Saad S. Elmorsyb
a Photochemistry Department, National Research Centre, Dokki 12622, Cairo, Egypt
b Chemistry Department, Faculty of Science, Mansoura University, 35516-Mansoura, Egypt
An operationally simple and green method for the synthesis of a wide range of bis(indolyl)methanes, and N,N'-alkylidene
bisamides under mild conditions, with excellent yields using Silzic, has been developed. This improved method furnishes in
good yields bis(indolyl)methanes derivatives starting from indole and aldehydes, or ketones, and N,N'-alkylidene bisamides
derivatives starting from acetamide and aldehydes. The catalytic system was reused up to three times with the same efficiency.
Page 1 of 6

Original article
An efficient synthesis of bis(indolyl) methanes and N, N'-alkylidene
bisamides by Silzic under solvent free conditions
Hanan A. Solimana∗, Ahmed Y. Mubarak,b, Saad S. Elmorsyb
a Photochemistry Department, National Research Centre, Dokki 12622, Cairo, Egypt
b Chemistry Department, Faculty of Science, Mansoura University, 35516-Mansoura, Egypt
ARTICLE INFO
ABSTRACT
An operationally simple and green method for the synthesis of a wide range of bis(indolyl)methanes,
and N,N'-alkylidene bisamides under mild conditions, with excellent yields using Silzic, has been
developed. This improved method furnishes in good yields bis(indolyl)methanes derivatives starting
from indole and aldehydes, or ketones, and N,N'-alkylidene bisamides derivatives starting from
acetamide and aldehydes. The catalytic system was reused up to three times with the same efficiency.
Article history:
Received 17 August 2015
Received in revised form 12 November 2015
Accepted 16 November 2015
Available online
Keywords:
Bis(indolyl)methanes
N,N'-Alkylidenebisamides
Acetamide
Mild conditions
Silzic
1. Introduction
Bis(indolyl)alkanes have important biological, industrial, and synthetic applications. Thus, their preparation is of considerable
interest for the researchers in the development of new protocols. In recent years, syntheses of this class of molecules under mild
conditions have been reported, with promoters such as Montmorillonite clay K-10 [1] in solid state reactions [2], trichloro-1,3,5-
triazine [3], AlPW12O40 [4], sodium dodecyl sulfate (SDS) [5], ZrCl4 [6], I2 [7], In(OTf)3/ionic liquid [8], CuBr2 [9], MW/Lewis acids
(FeCl3, BiCl3, InCl3, ZnCl2, CoCl2) [10], NaHSO4 and Amberlyst-15 [11], silica sulfuric acid (SSA) [12], metal hydrogen sulfates [13],
NaHSO4/ionic liquid [14], CAN [15], NBS [16], and Ph3CCl [17].
Amides and bisamides are functionalized groups represent important biological and medicinal scaffolds, which play a major role in
the development and composition of biological and pharmacological systems [18,19]. In particular, symmetrical and unsymmetrical
N,N'-alkylidene bisamides and their derivatives are found as key structural subunits for the construction of peptidomimetic frameworks
[20, 21]. Recently, Perumal et al. [22] have reported an alternative approach to synthesize symmetrical N,N'-alkylidene bisamides by a
reaction of aldehydes with nitriles in the presence of sulfamic acid. However, the yields were moderate. Milenkovic et al. [23] have
synthesized activated imines and aminal derivatives as potential precursors for the synthesis of amino acid under Dean-Stark water
trapping conditions. Zhu et al. [24] have reported the synthesis of fluorine-containing N,N’-alkylidenebisamides in the presence of
fluoroalkanesulfonic acids. Bhatnagar et al. [25, 26] have reported the synthesis of benzylidene bisamides from the direct condensation
of benzaldehyde and different amide derivatives. However, most of these existing methods involve toxic metal ions and solvents, carry
high costs, use corrosive reagents and require cumbersome work-up procedures. Synthetic methodologies based on green chemistry
processes are of increasing interest in organic syntheses. Recently, silica supported zinc chloride (Silzic) has been used as a solid acid
catalyst in many organic transformations [27-29] and this is consistent with our interest in using silicon-based reagents in organic
syntheses [30]. Herein we wish to report the use of Silzic as a reusable solid acid catalyst for the synthesis of bis(indolyl)methanes and
N,N'-alkylidene bisamides.
2. Experimental
2.1 Typical procedure for the synthesis of bisindolylmenthanes
To a stirred mixture of aldehyde, or ketone (5 mmol), and indole (10 mmol), Silzic (0.2 g, 20 mol%) was added and the mixture was
allowed to stir at 100 °C for the total recorded time. After the completion (the reaction was monitored by TLC analysis) of the reaction,
EtOAc (20 mL) was added to the reaction mixture. Then, the solid was filtered off, the filtrate was concentrated, and the residue was
———
∗ Corresponding author.
E-mail address: tarek12_2@yahoo.com
Page 2 of 6

subjected to short column chromatography using pet.ether-EtOAc (8:2) to give pure 3a-m. The bisindolylmethane 3 are known
compounds and all spectroscopic data were in agreement with literature reports [31-33].
2.2 General procedure for synthesis of N,N'-alkylidene bisamides
To a stirred mixture of aldehyde (5 mmol), and acetamide (10 mmol), was added Silzic (0.2 g, 20 mol%) and the mixture was
o
allowed to stir at 100 C for the recorded time. After the completion of the reaction (the reaction was monitored by TLC analysis),
EtOH (20 mL) was added to the reaction mixture. Then, the solid was filtered off, the filtrate was concentrated, and the solid residue
was washed with diethyl ether to give the pure products (4a-j). Some of the N,N'-alkylidene bisamides 4 are known compounds and all
spectroscopic data were in agreement with literature reports.
Data for a representative example are showed:
N,N'-(4-Methoxyphenyl)methylene)diacetamide (4b): Mp 230 °C; IR (KBr, cm-1): ν 3276, 3030, 2933, 2838, 1671, 1567, 1513,
1
1367, 1249, 1183,1090, 820, 596; H NMR (300 MHz, DMSO-d6): δ 8.03 (d, 2H, J =7.3 Hz, 2NH), 7.33 (d, 1H, J = 8.1 Hz, Ar-H),
6.80 (d, 2H, J = 8.1Hz, Ar-H), 6.54 (t, 1H, J =7.5 Hz, CH), 3.81 (s, 3H, OCH3), 1.79 (s, 6H, 2CH3); 13C NMR (75 MHz, DMSO-d6): δ
170.25, 158.5, 141.3, 127.2, 114.2, 68, 55, 23.2; MS: m/z (%) 236.12 (M+, 100.0), 237.12 (M++1, 13.3); Anal. calcd. C, 61.00; H, 6.83;
N, 11.86, found: C, 60.86; H, 6.43; N, 11.56.
N,N'-(4-Methylphenyl)methylene)diacetamide (4d): Mp 236 °C; IR (KBr, cm-1): ν 3275, 3031, 2951, 2854, 1670, 1566,1541,1394,
1
1280, 1092, 859,809, 630; H NMR (300 MHz, DMSO-d6): δ 8.28 (d, 2H, J =7.6 Hz, 2NH), 7.14 (d, 2H, J = 8.2 Hz, Ar-H), 7.11 (d,
2H, J = 8.6 Hz, Ar-H), 6.53 (t, 1H, J =7.7Hz, CH), 2.43 (s, 3H, CH3) 1.84 (s, 6H, 2CH3); 13C NMR (75 MHz, DMSO-d6): δ 170.25,
140.3, 136.5, 128.2, 124.2, 68, 23.2, 21.2; MS: m/z (%) = 220.12 (M+, 100.0), 221.12 (M++1, 13.7); Anal. calcd. C, 65.43; H, 7.32; N,
12.72, found: C, 65.43; H, 7.22; N, 12.52.
3. Results and discussion
The synthesis of bis (indolyl)methanes (3a-m) in high yields, was achieved through a reaction of indole (1) and aldehydes or
ketones (2) using Silzic as depicted in Scheme 1. As a part of an ongoing study to investigate the optimum conditions for these
reactions, we studied the effect of the catalyst loading at different temperatures using indole (10 mmol) and benzaldehyde (5 mmol) as
a model reaction. The obtained results are summarized in Table 1.
Table 1.
Optimization of the reaction conditions.
Entry
Amount of Silzic
0
0.1 mg
0.2 mg
0.2 mg
0.3 mg
Temp (oC)
r.t.
r.t.
50
80
100
Time
5 h
5 h
4 h
35 min
35 min
Yield (%)
0
20
45
93
93
1
2
3
4
5
o
It is found that the use of 0.2 g, 20 mol℅ of Silzic at 80 C resulted in the highest yield, and the increase of the catalyst or
temperature does not lead to increased output.
R
R'
O
ZnCl2/SiO2
slovent-free
+
R
R'
2a-m
N
N
H
N
H
80 0
C
H
1
3a-m
a: R=Ph,
R'= H
R'= H
R'= H
R'=H
R'=H
R'=H
b: R=4-OMePh,
c: R=4-ClPh,
d: R=4-MePh,
e: R=4-NO2Ph,
f: R=4-BrPh,
g: R=2,4-diOMePh, R'=H
h: R=3,5-diOMePh, R'=H
i: R=3,4-diClPh,
R'=H
j: R,R'=cyclohexane
k: R,R'=cyclopentane
l: R,R'=cyclheptane
m: R=Ph,
R'=Me
Scheme 1. Synthesis of bis(indolyl)methane.
To investigate the scope and the generality of this new protocol, the reaction was extended to a variety of aldehydes as well as
ketones with indole and the results are summarized in Table 2. Though the reactions of indole with various aldehydes were fast, the
Page 3 of 6

reaction with ketones took longer time (Table 2, entries 10-13). The electron deficiency and nature of the substituent on the aromatic
ring affect the conversion rate, As expected the aldehydes having electron-withdrawing groups on the aromatic ring (Table 2, entries
3,5,6) react faster than aldehydes having electron-donating groups (Table 2, entries 2,4,7,8).
Table 2
Synthesis of bis(indolyl)methanes using Silzic.
Entry
Aldehyde/ketone
Time (min)
Product
Yield
(%)
93
92
93
91
95
94
90
91
89
70
65
55
35
1
2
3
4
5
6
7
8
Benzaldehyde
35
33
27
35
25
25
30
28
30
40
42
44
53
3a
3b
3c
3d
3e
3f
3g
3h
3i
4-Methoxybenzaldehyde
4-Chlorobenzaldehyde
4-Methylbenzaldehyde
4-Nitrobenzalde hyde
4-Bromobenzaldehyde
2,4Dimethoxybenzaldehyde
3,5-Dimethoxybenzaldehyde
3,4-Dichlorobenzaldehyde
Cyclohexanone
9
10
11
12
13
3j
3k
3l
Cyclopentanone
Cycloheptanone
Acetophenone
3m
The structural elucidation of bis(indolyl)methane derivatives was assigned on the basis of melting point and spectral analyses. First,
in the IR spectra of these compounds, the absorption at 3400-3460 cm-1 attributed for the NH group, and 1335 for C-N. The 1H-NMR
spectrum of 3 showed a singlet at 5.83-5.91 ppm for the proton of C-H, another singlet for two N-H protons appeared at 7.85-7.94
1
ppm, and the aromatic protons appeared at 6.36-7.45 ppm. For example, the H NMR of 3d displayed a singlet at 5.87 ppm for C-H
proton, and a singlet at 7.89 ppm for two N-H protons, which disappeared with D2O exchange, in addition to the signal of a methyl
group at 2.34 ppm. In addition, 1H NMR of 3j showed one doublet at 2.58 and one multiplet at 1.69 ppm. These were assigned to the
cyclohexane protons. The mechanism of to the Silzic-catalyzed synthesis of bisindolylmenthane is proposed as shown in Scheme 2.
First, an aldehyde or ketone was activated by the Silzic and underwent an electrophilic substitution reaction at the 3-position of the
indole. After dehydration, intermediate (A) was formed and was further activated by Silzic to become an electrophile, which was
attacked by a second molecule of indole, to form bisindolylmenthane (3a-m).
Scheme 2. A plausible mechanism for the formation of bis(indolyl)methane.
The present study has established a new, mild and convenient protocol for the synthesis of symmetrical bisamides by condensing
aryl aldehydes and acetamide using Silzic as catalyst (Scheme 3, Table3).
Scheme 3. Synthesis of N,N'-alkylidene bisamides.
The experimental results illustrate the efficiency of the present method. The reactions preceded well with various aldehydes and
acetamide to provide symmetrical N,N'-alkylidene bisamides. Aromatic aldehydes containing electron-withdrawing groups (such as
Page 4 of 6

nitro-) required shorter time and higher yield than those with electron- donating groups (such as a methoxy group). In addition, the
present procedure worked well with sterically hindered aldehydes, e.g., 2,4-Dimethoxy benzaldehyde, benzo[d][1,3]dioxole-5-
carbaldehyde, and 1-naphthaldehyde and gave good yields (Table 3, entries 7,9,10).
Table 3
Synthesis of N,N'-alkylidene bisamides using Silzic under solvent –free conditions
Entry Aldehyde
Time
(min)
35
33
27
35
25
25
Product
Yield
(%)
83
75
82
77
85
81
1
2
3
4
Benzaldehyde
4-Methoxybenzaldehyde
4-Chlorobenzaldehyde
4a
4b
4c
4d
4e
4f
4-Methylbenzaldehyde
5
4-Nitrobenzaldehyde
6
4-Bromobenzaldehyde
7
8
9
10
2,4-Dimethoxybenzaldehyde
4-(Dimethylamino)benzaldehyde
Benzo[d][1,3]dioxole-5-carbaldehyde
1-Naphthaldehyde
30
28
30
40
73
82
89
70
4g
4h
4i
4j
1
The structures of the products were assigned based on the analysis of spectroscopic data such as IR, and H NMR, which were
found to be in agreement with the literature values [22, 34-36]. The IR spectra showed characteristic absorption bands at 3319 -
3265and 1671-1654cm-1 for the NH group, and the carbonyl group, respectively. The 1H-NMR showed a triplet at 6.52-6.59 ppm with
a coupling constant of 7.8 Hz for the CH proton (which converted to a singlet with D2O exchange), a multiplet at 6.78-7.65 ppm for the
aromatic protons, and a doublet at 8.19-8.72 ppm with J = 7.8 Hz was observed for the NH proton (which disappeared with D2O
exchange). The NH proton was coupled with the CH proton with a coupling constant of 7.8 Hz.
To explain the formation of bisamides via the one-pot multi-component reaction, we have proposed a plausible reaction mechanism,
which is illustrated in Scheme 4. Firstly, the activation of aldehyde by π empty orbital of Lewis acid occurred to form a cationic
intermediate B). The second molecule of amide is added to B to produce the product.
Scheme 4. A plausible mechanism for the formation of bisamide.
To check the reusability of catalyst, the catalyst was filtered off and washed with chloroform repeatedly, dried and reused. It was
found that catalyst can be recycled at least three cycles without any change in activity.
4. Conclusions
In conclusion, Silzic has been successfully used as an effective catalyst for the synthesis of symmetrical N,N’- alkylidene bisamides
for the first time. This procedure has advantages in comparison with the previously reported methods, in terms of yield, green catalyst,
mild reaction conditions, simple procedures, lack of toxicity, low cost, and the use of a commercially available catalyst and simplicity
of workup.
Acknowledgments
Financial support by National Research Center (Cairo, Egypt) is gratefully appreciated.
References
[1]
a) A.K. Maiti, P. Bhattacharyya, Montmorillonite clay-catalysed synthesis of bis(indol-3-yl)-methanes and 1,2-bis(indol-3-yl)ethanes, J. Chem. Res.
(1997) 424-425;
(b) M. Chakrabarty, N. Ghosh, R. Basak, Y. Harigaya, A facile and efficient synthesis of 2,2‐bis(3′/2′‐indolyl)ethylamines and three bisindolic natural
products, Synth. Commun. 34 (2004) 421-434.
[2]
[3]
(a) J.B. Meng, D.M. Du, G.X. Xiong, et al., A dual pathway in the solid-state photoreaction of nitrobenzaldehydes with indole, J. Heterocyclic Chem. 31
(1994) 121–124;
(b) X. Li, Y. Wang, D. Du, et al., Solid state reactions of indole with carbonyl compounds, Sci. China Ser. B 40 (1997) 270-277.
G.V.M. Sharma, J.J. Reddy, P.S. Lakshmi, P.R. Krishna, A versatile and practical synthesis of bis(indolyl)methanes/bis(indolyl)glycoconjugates
catalyzed by trichloro-1,3,5-triazine, Tetrahedron Lett. 45 (2004) 7729-7732.
Page 5 of 6

[4]
[5]
[6]
[7]
H. Firouzabadi, N. Iranpoor A.A. Jafari, Aluminumdodecatungstophosphate (AlPW12O40), a versatile and a highly water tolerant green Lewis acid
catalyzes efficient preparation of indole derivatives, J. Mol. Catal. A: Chem. 244 (2005) 168-172.
M.L. Deb, P.J. Bhuyan, An efficient and clean synthesis of bis(indolyl)methanes in a protic solvent at room temperature, Tetrahedron Lett. 47 (2006)
1441-1443.
Z.H. Zhang, L. Yin, Y.M. Wang, An efficient and practical process for the synthesis of bis(indolyl)methanes catalyzed by zirconium tetrachloride,
Synthesis (2005) 1949-1954.
S.J. Ji, S.Y. Wang, Y. Zhang, T.P. Loh, Facile synthesis of bis(indolyl)methanes using catalytic amount of iodine at room temperature under solvent-free
conditions, Tetrahedron 60 (2004) 2051-2055.
[8]
[9]
S.J. Ji, M.F. Zhou, D.G. Gu, et al., Efficient synthesis of bis(indolyl)methanes catalyzed by lewis acids in ionic liquids, Synlett (2003) 2077-2079.
L.P. Mo, Z.C. Ma, Z.H. Zhang, CuBr2-catalyzed synthesis of bis(indolyl)methanes, Synth. Commun. 35 (2005) 1997-204.
[10]
M. Xia, S.H. Wang, W.B. Yuan, Lewis acid catalyzed electrophilic substitution of indole with aldehydes and schiff's bases under microwave solvent‐
free irradiation, Synth. Commun. 34 (2004) 3175-3182.
[11]
C. Ramesh, J. Banerjee, R. Pal, B. Das, Silica supported sodium hydrogen sulfate and amberlyst-15: two efficient heterogeneous catalysts for facile
synthesis of bis-and tris(1h-indol-3-yl)methanes from indoles and carbonyl compounds[1], Adv. Synth. and Catal. 345 (2003) 557-559.
[12]
[13]
[14]
[15]
[16]
[17]
D.M. Pore, U.V. Desai, T.S. Thopate, P.P. Wadgaonkar, A mild, expedient, solventless synthesis of bis(indolyl)alkanes using silica sulfuric acid as a
reusable catalyst, Arkivoc 12 (2006) 75-80.
K. Niknam, M.A. Zolfigol, T. Sadabadi, A. Nejati, Preparation of indolylmethanes catalyzed by metal hydrogen sulfates, J. Iran. Chem. Soc. 3 (2006)
318-322.
L.P. Zhang, Y.Q. Li, M.Y. Zhou, Efficient and eco-friendly process for the synthesis of bi (indolyl)-methanes catalyzed by sodium hydrogensulfate
monohydrate in ionic liquid n-butylpyridinium tetrafluoroborate, Chin. Chem. Lett. 17 (2006) 723-726.
C. Ramesh, N. Ravindranath, B. Das, Electrophilic substitution reactions of indoles with carbonyl compounds using ceric ammonium nitrate: A novel and
efficient method for the synthesis of di- and tri-indolylmethanes, J Chem. Res. Synop. (2003) 72-74.
H. Koshima, W. Matsuaka, N-Bromosuccinimide catalyzed condensations of indoles with carbonyl compounds under solvent-free conditions, J.
Heterocycl. Chem. (2002) 1089-1091.
A. Khalafi-Nezhad, A. Parhami, A. Zare, et al., Trityl chloride as a novel and efficient organic catalyst for room temperature preparation of
bis(indolyl)methanes under solvent-free conditions in neutral media, Synthesis (2008) 617-621.
[18]
[19]
J.W. Bode, Emerging methods in amide- and peptide-bond formation, Curr. Opin. Drug Discovery Dev 9 (2006) 765-775.
H.R. Shaterian, M. Ghashang, M. Feyzi Silica sulfuric acid as an efficient catalyst for the preparation of 2H-indazolo[2,1-b]phthalazine-triones, Appl.
Catal. A 345 (2008) 128-133.
[20]
T. Yamazaki, K.I. Nunami, M. Goodman, Cyclic retro-inverso dipeptides with two aromatic side chains. II. Conformational analysis, Biopolymers 31
(1991) 1513-1528.
[21]
[22]
M. Goodman, H. Shao, Peptidomimetic building blocks for drug discovery: an overview, Pure. Appl. Chem. 68 (1996) 1303-1308.
N.P. Selvam, S. Saranye, P.T. Perumal, A convenient and efficient protocol for the synthesis of symmetrical N,N′-alkylidine bisamides by sulfamic acid
under solvent-free conditions, Can. J. Chem. 85 (2008) 32-38.
[23]
A. Milenkovic, F. Fache, R. Faure, M. Lemaire, Activated imines and aminal derivatives: Potential precursors of beta-amino acids, Synth. Commun. 29
(1999) 1535-1546.
[24]
[25]
[26]
[27]
S. Zhu, G. Xu, Q. Chu, Y. Xu, C. Qui, Synthesis of Fluorine-Containing Symmetrical N,. N-Alkylidene Bisamides, J. Fluorine Chem. 93 (1999) 69-71.
G.S. Bhatnagar, K.C. Pandya, Condensation of aldehydes with amides, Proceedings-Indian Academy of Sciences, Section A 24 (1946) 487-495.
R.K. Mehra, K.C. Pandya, The condensation of aldehydes with amides, Proceedings-Indian Academy of Sciences, Section A 10 (1939) 285-288.
D.J. Upadhya, S.D. Samant, A facile and efficient pinacol–pinacolone rearrangement of vicinal diols using ZnCl2 supported on silica as a recyclable
catalyst, Applied Catalysis A: General 340 (2008) 42-51.
[28]
H.A. Soliman, A.Y. Mubarak, A. El-Mekabati, S.S. Elmorsy, SiO2/ZnCl2-catalyzed heterocyclic synthesis: green, rapid and efficient one-pot synthesis of
14-H-dibenzo[a, j]xanthenes, 1,8-dioxo-octahydroxanthenes and 1,8-dioxo-decahydroacridines under solvent-free conditions, Chem. Sci. Trans. 3 (2014)
819-825.
[29]
[30]
H.A. Soliman, A.Y. Mubarak, A. El-Mekabati, H.M. Awad, S.S. Elmorsy, Ecofriendly synthesis of amidochloroalkyl naphthols, cyclization of the
product to oxazepinones for biological evaluation, Monatsh Chem. (2015) DOI :10.1007/s00706-015-1536-2.
a) H.A. Soliman, F.M.E. Abdel-Megeid, S.S. Elmorsy, Silicon tetrachloride-induced regioselective reaction of N-bromosuccinimide with arylidene
malononitrile and with α, β-unsat-urated ketones, Org. Chem. An Indian J. 11 ( 2015) 223-228.
(b) H.A. Soliman, T.K. Khatap, Efficient heterogeneous catalytic one-pot, three component synthesis of γ-hydroxy-β-ketoamide, Egypt. J. of chem. 57
(2014) 129-142.
(c) H.A. Soliman, T.A. Salama, Silicon tetrachloride-induced green and efficient MCR protocol for the synthesis of 1,8-dioxo-decahydroacridines and
their transformation to novel functionalized pyrido-tetrazolo[1,5-a]azepine derivatives, Org. Chem. An Indian J. 10 ( 2014) 63-68.
(d) T.K. Khatab, K.A.M. El-Bayouki, W.M. Basyouni, A new and facile tetrachlorosilane-promoted one-pot condensation for the synthesis of a novel
series of tetracyclic 1,5-thiazepines, Tetrahedron Lett. 55 (2014) 6039-6041;
(e) H.A. Soliman, T.A. Salama, Silicon-mediated highly efficient synthesis of 1,8-dioxo-octahydroxanthenes and their transformation to novel
functionalized pyrano-tetrazolo[1,5-a] azepine derivatives, Chin. Chem. Lett. 24 (2013) 404-406.
(f) T.K. Khatab, K.A.M. El-Bayouki, W.M. Basyouni, An efficient synthesis of β-acylureas via a three-component, one-pot synthesis using TCS/ZnCl2,
Tetrahedron Lett. 52 (2011) 1448-51
[31]
[32]
[33]
[34]
[35]
[36]
V.T. Kamble, B.P. Bandgar, S.N. Bavikar, Highly efficient synthesis of bis(indolyl)methanes catalyzed by sodium tetrafluoroborate, Chin. J. Chem. 25
(2007)13-17.
S. Sheng, Q. Wang, Y. Ding, X. Liu, M. Cai, Synthesis of bis(indolyl)methanes using recyclable PEG-supported sulfonic acid as catalyst, Catal. Lett. 128
(2009) 418-422.
R. Ghorbani-Vaghei, H. Veisi, H. Keypour, A.A. Dehghani-Firouzabadi, A practical and efficient synthesis of bis(indolyl)methanes in water, and
synthesis of di-, tri-, and tetra(bis-indolyl)methanes under thermal conditions catalyzed by oxalic acid dehydrate, Mol. Divers 14 (2010) 87-96.
M.R.M. Shafiee Silica-supported barium chloride (SiO2–BaCl2)—Efficient and heterogeneous catalyst for the environmentally friendly preparation of
N,N′-alkylidene bisamides under solvent-free conditions, Can. J. Chem. 89 (2011) 555-561
M.R.M. Shafiee, One-pot preparation of N,N′-alkylidene bisamide derivatives catalyzed by silica supported polyphosphoric acid (SiO2-PPA), J. Saudi
Chem. Soc. 18 (2014)115-119.
B.F. Mirjalili, M.A. Mirhoseini, Tandem synthesis of N,N-alkylidenebisamides promoted by nano-SnCl4.SiO2, J. Chem. Sci. 125 (2013)1481-1486.
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