Facile three-component preparation of benzodiazepine derivatives catalyzed by zinc sulfide nanoparticles via grinding method

Article abstract of DOI:10.1007/s11164-015-2254-4

Abstract: In this research, ZnS nanoparticles were prepared and applied as heterogeneous reusable catalyst for synthesis of 1,5-benzodiazepines under grinding conditions at 70?°C. The multi-component reactions of aldehydes, dimedone and o-phenylenediamine

Full text of DOI:10.1007/s11164-015-2254-4

Res Chem Intermed
DOI 10.1007/s11164-015-2254-4
Facile three-component preparation of benzodiazepine
derivatives catalyzed by zinc sulfide nanoparticles
via grinding method
1
1
Hossein Naeimi
•
Hossein Foroughi
Received: 15 April 2015 / Accepted: 28 August 2015
Ó Springer Science+Business Media Dordrecht 2015
Abstract In this research, ZnS nanoparticles were prepared and applied as hetero-
geneous reusable catalyst for synthesis of 1,5-benzodiazepines under grinding conditions
at 70 °C. The multi-component reactions of aldehydes, dimedone and o-phenylenedi-
amine were carried out under grinding conditions to obtain some 3,3-dimethyl-
2
,3,4,5,10,11-hexahydro-11-[aryl]-1H-dibenzo[b,e][1,4] diazepine-1-one derivatives.
The present approach provides several advantages, including high yields, short reaction
times, little catalyst loading and purification of compounds by crystallization method.
The catalyst was characterized by using FT-IR, XRD, PL, EDX, SEM and TEM
techniques.
Graphical Abstract
Electronic supplementary material Theonlineversionofthisarticle(doi:10.1007/s11164-015-2254-4)
contains supplementary material, which is available to authorized users.
&
Hossein Naeimi
naeimi@kashanu.ac.ir
1
Department of Organic Chemistry, Faculty of Chemistry, University of Kashan, Kashan 87317,
Islamic Republic of Iran
123

H. Naeimi, H. Foroughi
Keywords 1,5-Benzodiazepines Á ZnS nanoparticles Á Dimedone Á
o-Phenylenediamine Á Aromatic aldehyde Á Grinding
Introduction
Multi-component reactions (MCRs) are those reactions whereby more than two
reactants combine in a sequential manner to give highly selective products that
retain a majority of atoms from the starting material [1–5]. MCRs are efficient, fast,
environmentally friendly, practical and atom economic. They introduce an effective
tool for providing different compounds with biological and pharmaceutical
properties [6, 7], including heterocyclic compounds [8, 9]. Benzodiazepines are
some of the applicable heterocyclic compounds that have gained extensive interest
because of their wide usage in biological activities [10, 11]. Benzodiazepine
compounds are extensively consumed psychoactive drugs worldwide due to their
anxiolytic and anticonvulsant activity [12].
Some methods for the synthesis of 1,5-benzodiazepine derivatives have been
reported in the literature via the condensation of one equivalent o-phenylenediamine
with various aldehydes or ketones in the presence of a wide variety of catalysts,
including SmI in the presence of molecular sieves at room temperature [13],
2
HBF –SiO under solvent-free conditions [14], Yb(OTf) [15], SiO [16], AcOH as
2
4
2
3
catalyst under microwave irradiation [17], SiO –H SO catalyst under grinding-
2
2
4
microwave method [18], C F COOH [19], Ga(OTf) in CH CN [20], amorphous
3
6
5
3
mesoporous iron alumino phosphate (FeAlP-550) as catalyst under solvent-free
condition [21], Fe O nanoparticles [22], Hg(OTf) [23] and CF COOH in the
3
4
2
3
presence of dehydroacetic acid (DHA) [24]. Furthermore, the synthesis of
-substituted-1,5-benzodiazepine derivatives have been carried out by three-
4
component condensation of o-phenylenediamine, dimedone and aldehydes by using
AcOH in ethanol [25], acetic acid [26], oxalic acid in water [27], AcOH in water
under microwave condition [28], acetic acid in toluene [29], H SO [30], HCl [31]
2
4
as Brønsted catalysts. Some of the other reported catalysts for this reaction are
Er(OTf)3 in CH CN [32, 33] and AcOH in the presence of 2,2-dihydroxy-1-
phenylethanone under microwave irradiation [34]. Also, the hetero-Cope
3
Fig. 1 Some examples of biologically 4-substituted-1,5-benzodiazepine derivatives
1
23

Facile three-component preparation of benzodiazepine…
rearrangement protocol reported the synthesis of these compounds via condensation
of 2-formyl benzoic acid with o-phenylenediamine and tetronic acid in water under
microwave irradiation [28]. A unique gold (I)-catalyzed synthesis of 1,5-benzodi-
azepines directly from o-phenylenediamines and alkynes was achieved for the first
time by Xu and co-workers [35], and was developed by Luo et al. [36]. Recently, the
synthesis of benzodiazepines was reported by catalytic three-component coupling
reaction of aromatic diamines, Meldrum’s acid, and isocyanides [37]. In addition,
acylchlorids were used for the synthesis of 4-substituted-1,5-benzodiazepine
derivatives with medicinal properties [38–40] (Fig. 1).
In conjunction with ongoing to preparation of heterocyclic compounds, we report
an efficient and novel method for the synthesis of 4-substituted-1,5-benzodiazepines
via one-pot MCRs of o-phenylenediamine, dimedone and aldehyde derivatives. In
this protocol, the aforesaid desired compounds were prepared in excellent yields and
with short reaction times by using of ZnS NPs with specific surface to volume,
crystalline size as a robust as well as effective and easily recoverable catalyst.
Experimental
Materials and techniques
All reagents were purchased from Merck, Aldrich, CDH and Fluka and were used
without further purification. Fourier transform infrared (FT-IR) spectra were
obtained as KBr pellets on a Perkin–Elmer 781 spectrophotometer. Ultraviolet
(
spectrophotometer. Nuclear magnetic resonance ( H NMR and C NMR) were
UV–Vis) spectra were obtained in CDCl solvents on a Perkin–Elmer 550 S
3
1
13
recorded in DMSO and CDCl solvents on a Bruker DRX-400 spectrometer with
3
tetramethylsilane (TMS) as internal reference. The elemental analyses (C, H, N)
were obtained from a Carlo ERBA Model EA 1108 analyzer. Electron Ionization
Mass (EI-MASS) spectra were recorded on Agilent Technology (HP) 5973
instrument at an ionization potential of 70 eV. Nanostructures were characterized
using a Holland Philips Xpert X-ray powder diffraction (XRD) diffractometer
(
CuK, radiation, k = 0.154056 nm), at a scanning speed of 2°/min from 10° to 100°
2Ø). Electron Dispersive X-Ray (EDX) of nanoparticles was performed on a Zeiss
l GMA vp. Photoluminescence (PL) spectra were obtained on the Avantes
(
P
Avaspec-2048 spectrophotometer. Scanning electron microscopy (SEM) of
nanoparticles was performed on a KYKY EM-3200. Transmission electron
microscopy (TEM) of nanoparticles was performed on a LEO AB-912. Melting
points (MP) were obtained with a Thermo Scientific 9300. The purity determination
of the substrates and reaction monitoring were accomplished by TLC on silica-gel
polygram SILG/UV 254 plates (from Merck Company).
Preparation of ZnS NPs
In a typical procedure for synthesis of ZnS NPs, 1 mmol of Zn(OAc) Á2H O and
2
2
1
mmol of thioacetamide (TAA) were added into 20 ml ethylene glycol in a 50-ml
123

H. Naeimi, H. Foroughi
round-bottomed flask at room temperature. The solution was heated to 110 °C by
microwave and the temperature was maintained for 5 min with stirring. After the
solution was allowed to cool to room temperature naturally, the white crystalline
ZnS nanoparticles were precipitated. The solid was separated, washed with absolute
ethanol three times and dried at 60 °C for 3 h [41–45].
General procedure for synthesis of 4-substituted-1,5-benzodiazepines catalyzed
by ZnS NPs
A mixture of o-phenylenediamine (1 mmol), dimedone (1 mmol) and selected
aromatic aldehydes (1 mmol) in the presence of ZnS nanoparticles 10 mol%
(
0.01 g) was stirred in a mortar-pestle at 70 °C for appropriate times. During the
procedure, the reaction was monitored by TLC (Thin Layer Chromatography).
Upon completion, the reaction mixture was cooled to room temperature and the
reaction mixture was dissolved in ethanol. The catalyst was insoluble in ethanol and
easily centrifuged to separate. The solvent was evaporated and the obtained oil was
crystallized from methanol and water (6:5) to afford the product. The residue was
purified by recrystallization from ethanol. They were characterized by comparison
of their physical and spectral data with those of authentic samples [30–40].
3
1
,3-Dimethyl-2,3,4,5,10,11-hexahydro-11-[phenyl]-1H-dibenzo[b,e][1,4] diazepin-
-one (3a)
Pale green solid, yield: 84 %; m.p. = 246–248 °C; R = 0.125 (1:1 Ethylacetate/n-
f
-
1
Hexane); UV–Vis: kmax = 360 nm; IR (KBr)/t (cm ): 3296, 3237, 3057, 2955,
1
1
ppm: 1.03 (s, 3H, CH –), 1.08 (s, 3H, CH –), 2.11 (A.B q, 2H, J = 16.0 Hz, CH ),
584, 1384, 1530, 1329, 1424, 1277; H NMR (DMSO ? CDCl , 400 MHz)/d
3
3
3
2
2
Ar–), 6.89 (d, 1H, J = 8.0 Hz, Ar–), 6.95 (t, 1H, J = 8.0 Hz Ar–), 7.0–7.1 (m, 3H,
.56 (s, 2H, –CH –C=O), 5.71 (s, 1H, N–H), 6.08 (s, 1H, C–H), 6.47–6.57 (m, 3H,
2
1
3
Ar–), 8.15 (d, 1H, J = 4.0 Hz, Ar–), 8.69 (s, 1H, N–H);
(
C NMR
DMSO ? CDCl , 100 MHz)/d (ppm): 27.95, 29.06, 32.21, 44.74, 50.05, 56.49,
3
1
1
10.68, 119.87, 120.44, 121.01, 122.98, 126.11, 127.7, 127.98, 131.49, 138.84,
?
45.1, 155.12, 192.52; EI-MASS (m/z, %): 318 (M , 26), 241 (100), 149 (52), 83
(
45), 77 (34), 57 (85), 55 (62); Anal. Calcd. For C H N O: C 79.21, H 6.96, N
21 22 2
8
.80, Found C 79.24, H 6.98, N 8.84.
3,3-Dimethyl-2,3,4,5,10,11-hexahydro-11-[(4-nitro)phenyl]-1H-dibenzo[b,e][1,4]
diazepin-1-one (3b)
Yellow solid, yield: 89 %; m.p. = 280–281 °C (decomp); R = 0.125 (1:1 Ethy-
f
-
1
lacetate/n-Hexane); UV–Vis: kmax = 348 nm; IR (KBr)/t (cm ): 3355, 3279,
1
181, 2955, 1591, 1381, 1511, 1339, 1425, 1275; H NMR (DMSO ? CDCl ,
3
3
4
J = 16.0 Hz, CH –), 2.53 (s, 2H, –CH –C=O), 5.64 (s, 1H, N–H), 5.87 (s, 1H,
00 MHz)/d (ppm): 0.99 (s, 3H, CH –), 1.06 (s, 3H, CH –), 2.14 (A.B q, 2H,
3
3
2
2
C–H), 6.43 (d, 1H, J = 6.4 Hz, Ar–), 6.55–6.61 (m, 2H, Ar–), 6.9 (d, 1H,
J = 6.4 Hz, Ar–), 7.21 (d, 2H, J = 8.8 Hz, Ar–), 7.84 (d, 2H, J = 8.8 Hz, Ar–),
1
23

Facile three-component preparation of benzodiazepine…
1
3
8
3
1
2
.58 (s, 1H, N–H); C NMR (DMSO ? CDCl , 100 MHz)/d (ppm): 28.09, 28.80,
3
2.20, 44.82, 49.93, 56.63, 109.44, 120.52, 120.75, 121.09, 123.08, 123.43, 128.57,
?
31.39, 138.03, 146.05, 153.05, 155.05, 192.85; EI-MASS (m/z, %): 397 (M , 29),
41 (100), 149 (66), 83 (51), 77 (32), 57 (39), 55 (47); Anal. Calcd. For
C H N O : C 69.41, H 5.82, N 11.56, Found C 69.45, H 5.85, N 11.59.
21 21 3 3
3,3-Dimethyl-2,3,4,5,10,11-hexahydro-11-[(2-nitro)phenyl]-1H-dibenzo[b,e][1,4]
diazepi-1-one (3c)
Orange solid, yield: 88 %; m.p. = 230–232 °C (decomp); R = 0.281 (1:1 Ethy-
f
-
1
lacetate/n-Hexane); UV–Vis: kmax = 346 nm; IR (KBr)/t (cm ): 3378, 3303,
1
069, 2957, 1591, 1381, 1528, 1332, 1473, 1279; H NMR (DMSO ? CDCl ,
3
3
4
J = 16.0 Hz, CH –), 2.58 (s, 2H, –CH –C=O), 5.04 (s, 1H, N–H), 6.01 (s, 1H,
00 MHz)/d (ppm): 0.95 (s, 3H, CH –), 1.05 (s, 3H, CH –), 2.01 (A.Bq, 2H,
3
3
2
2
C–H), 6.32 (d, 1H, J = 8.0 Hz, Ar–), 6.58 (t, 1H, J = 8.0 Hz, Ar–), 6.67 (t, 1H,
J = 8.0 Hz, Ar–), 6.79 (d, 1H, J = 8.0 Hz, Ar–), 7.04 (d, 1H, J = 8.0 Hz, Ar–),
1
3
.14–7.2 (m, 2H, Ar–), 7.74 (d, 1H, J = 8.0 Hz, Ar–), 8.91 (s, 1H, N–H); C NMR
7
(
DMSO ? CDCl , 100 MHz)/d (ppm): 28.11, 28.82, 32.22, 44.87, 49.91, 56.62,
3
1
1
09.46, 120.53, 120.78, 121.07, 123.1, 123.46, 126.14, 128.56, 128.59, 131.38,
?
38.06, 146.03, 153.08, 155.08, 192.89; EI-MASS (m/z, %): 363 (M , 26), 241
(
100), 149 (55), 83 (36), 77 (42), 57 (49), 55 (62); Anal. Calcd. For C H N O : C
21 21 3 3
6
9.41, H 5.82, N 11.56, Found C 69.46, H 5.85, N 11.60.
3,3-Dimethyl-2,3,4,5,10,11-hexahydro-11-[(3-nitro)phenyl]-1H-dibenzo[b,e][1,4]
diazepin-1-one (3d)
Pale yellow solid, yield: 88 %; m.p. = 195–197 °C; R = 0.125 (1:1 Ethylacetate/
f
-
1
n-Hexane); UV–Vis: kmax = 348 nm; IR (KBr)/t (cm ): 3375, 3328, 3049, 2959,
1
1
589, 1383, 1529, 1345, 1431, 1277; H NMR (DMSO ? CDCl , 400 MHz)/d
3
(
CH –), 2.58 (s, 2H, –CH –C=O), 5.81 (s, 1H, N–H), 6.20 (s, 1H, C–H), 6.50 (d, 1H,
ppm): 1.05 (s, 3H, CH –), 1.09 (s, 3H, CH –), 2.14 (A.Bq, 2H, J = 16.0 Hz,
3 3
2
2
J = 5.2 Hz, Ar–), 6.51–6.6 (m, 2H, Ar–), 6.9 (d, 1H, J = 7.2 Hz, Ar–), 7.29 (t, 1H,
J = 8.0 Hz, Ar–), 7.45 (d, 1H, J = 8.0 Hz, Ar–), 7.81 (d, 1H, J = 9.2 Hz, Ar–),
1
3
7
.98 (s, 1H, Ar–), 8.79 (s, 1H, N–H); C NMR (DMSO ? CDCl , 100 MHz)/d
3
(
ppm): 28.1, 28.81, 32.24, 44.86, 49.93, 56.64, 109.47, 120.56, 120.76, 121.06,
1
1
23.11, 123.47, 126.16, 128.49, 128.56, 131.39, 138.09, 146.05, 153.1, 155.09,
?
92.86; EI-MASS (m/z, %): 363 (M , 30), 241 (100), 149 (38), 83 (40), 77 (41), 57
(39), 55 (58); Anal. Calcd. For C H N O : C 69.41, H 5.82, N 11.56, Found
21 21 3 3
C 69.45, H 5.86, N 11.57.
3,3-Dimethyl-2,3,4,5,10,11-hexahydro-11-[(4-chloro)phenyl]-1H-dibenzo[b,e][1,4]
diazepin-1-one (3e)
Pale green solid, yield: 85 %; m.p. = 235–237 °C; R = 0.125 (1:1 Ethylacetate/n-
f
-
1
Hexane); UV–Vis: kmax = 344 nm; IR (KBr)/t (cm ): 3301, 3238, 3054, 2956,
1
1
587, 1381, 1532, 1329, 1426, 1278; H NMR (DMSO ? CDCl , 400 MHz)/d
3
123

H. Naeimi, H. Foroughi
(
ppm): 1.0 (s, 3H, CH –), 1.06 (s, 3H, CH –), 2.11 (A.Bq, 2H, J = 16.0 Hz, CH –),
3
3
2
2
J = 8.2 Hz, Ar–), 6.55 (m, 2H, Ar–), 6.88 (d, 1H, J = 8.2 Hz, Ar–), 6.98 (d, 2H,
.52 (s, 2H, –CH –C=O), 5.73 (s, 1H, N–H), 5.78 (s, 1H, C–H), 6.45 (d, 1H,
2
1
J = 8.4 Hz, Ar–), 7.01 (d, 1H, J = 8.4 Hz, Ar–), 8.61 (s, 1H, N–H); C NMR
3
(
DMSO ? CDCl , 100 MHz)/d (ppm): 28.17, 28.69, 32.24, 44.84, 49.90, 56.43,
3
1
1
09.38, 120.62, 120.72, 121.05, 123.11, 123.28, 128.36, 131.45, 138.06, 146.08,
?
50.02, 152.06, 192.81; EI-MASS (m/z, %): 362 (M , 33), 354 (M?2 , 11), 241
?
(100), 149 (57), 83 (35), 77 (28), 57 (68), 55 (53); Anal. Calcd. For C H ClN O:
21 21 2
C 71.48, H 6.0, N 7.94, Found C 71.53, H 6.5, N 7.98.
3,3-Dimethyl-2,3,4,5,10,11-hexahydro-11-[(2-chloro)phenyl]-1H-dibenzo[b,e][1,4]
diazepin-1-one (3f)
White solid, yield: 86 %; m.p. = 239–240 °C (decomp); R = 0.281 (1:1 Ethylac-
f
-
1
etate/n-Hexane); UV–Vis: kmax = 348 nm; IR (KBr)/t (cm ): 3292, 3235, 3062,
1
2
959, 1589, 1382, 1515, 1314, 1422, 1278; H NMR (DMSO ? CDCl , 400 MHz)/
3
d (ppm): 1.02 (s, 3H, CH –), 1.07 (s, 3H, CH –), 2.09 (A.Bq, 2H, J = 16.0 Hz,
3
3
CH –), 2.57 (s, 2H, –CH –C=O), 5.07 (s, 1H, N–H), 6.01 (s, 1H, C–H), 6.33 (d, 1H,
J = 7.2 Hz, Ar–), 6.44–6.62 (m, 2H, Ar–), 6.7 (d, 1H, J = 7.6 Hz, Ar–), 6.82 (d,
H, J = 7.6 Hz, Ar–), 6.85–7.0 (m, 2H, Ar–), 7.20 (d, J = 7.6 Hz, 1H, Ar–), 8.77
2
2
1
1
3
(
s, 1H, N–H); C NMR (DMSO ? CDCl , 100 MHz)/d (ppm): 28.17, 28.72,
3
3
1
3
2.26, 44.84, 49.88, 56.42, 109.32, 120.61, 120.66, 121.12, 123.13, 123.42, 126.11,
28.53, 128.62, 131.42, 138.04, 146.06, 149.55, 151.06, 192.82; EI-MASS (m/z, %):
?
52 (M , 36), 354 (M?2 , 12), 241 (100), 149 (52), 83 (49), 77 (33), 57 (42), 55
?
(51); Anal. Calcd. For C H ClN O: C 71.48, H 6.0, N 7.94, Found C 71.54, H 6.6,
21 21 2
N 7.99.
3,3-Dimethyl-2,3,4,5,10,11-hexahydro-11-[(2,3-dichloro)phenyl]-1H-dibenzo[b,e][1,4]
diazepin-1-one (3g)
Pale green solid, yield: 89 %; m.p. = 256–358 °C (decomp); R = 0.281 (1:1
f
-
1
Ethylacetate/n-Hexane); UV–Vis: kmax = 348 nm; IR (KBr)/t (cm ): 3379, 3301,
1
060, 2958, 1589, 1380, 1532, 1332, 1423, 1289; H NMR (DMSO ? CDCl ,
3
3
4
J = 16.0 Hz, CH –), 2.56 (s, 2H, -CH –C=O), 4.96 (s, 1H, N–H), 6.07 (s, 1H,
00 MHz)/d (ppm): 1.01 (s, 3H, CH –), 1.07 (s, 3H, CH –), 2.12 (A.Bq, 2H,
3
3
2
2
C–H), 6.30 (d,, 1H, J = 7.6 Hz, Ar–), 6.53–6.60 (m, 2H, Ar–), 6.62 (d, 1H,
J = 7.2 Hz, Ar–), 6.75 (t, 1H, J = 8.0 Hz, Ar–), 6.91 (d, 1H, J = 7.6 Hz, Ar–),
1
3
7
1
1
1
.08 (d, 1H, J = 7.6 Hz, Ar–), 8.64 (s, 1H, N–H); C NMR (DMSO ? CDCl3,
00 MHz)/d (ppm): 28.14, 28.67, 32.23, 44.81, 49.92, 56.29, 109.10, 120.68,
21.08, 121.35, 123.65, 126.13, 126.84, 128.83, 131.71, 132.05, 132.57, 137.33,
?
?
43.52, 156.12, 192.90; EI-MASS (m/z, %): 386 (M , 24), 388 (M?2 , 14), 390
?
M?4 , 4), 351 (52), 241 (100), 149 (25), 83 (34), 77 (24), 69 (52), 57 (43), 55 (54);
(
Anal. Calcd. For C H Cl N O: C 65.12, H 5.20, N 7.23 Found C 65.15, H 5.24, N
21
20
2 2
7
.26.
1
23

Facile three-component preparation of benzodiazepine…
3,3-Dimethyl-2,3,4,5,10,11-hexahydro-11-[(2,4-dichloro)phenyl]-1H-dibenzo[b,e][1,4]
diazepin-1-one (3h)
Pale green solid, yield: 90 %; m.p. = 230–232 °C (decomp); R = 0.281 (1:1
f
-
1
Ethylacetate/n-Hexane); UV–Vis: kmax = 347 nm; IR (KBr)/t (cm ): 3303, 3241,
1
055, 2957, 1590, 1382, 1533, 1330, 1468, 1278; H NMR (DMSO ? CDCl ,
3
3
4
J = 16.0 Hz, CH –), 2.57 (s, 2H, –CH –C=O), 4.99 (s, 1H, N–H), 5.99 (s, 1H,
00 MHz)/d (ppm): 1.02 (s, 3H, CH –), 1.07 (s, 3H, CH –), 2.11 (A.Bq, 2H,
3
3
2
2
C–H), 6.34 (d, 1H, J = 7.6 Hz, Ar–), 6.56–6.63 (m, 2H, Ar–), 6.65 (d, 1H,
J = 8.4 Hz, Ar–), 6.79 (d, 1H, J = 8.0 Hz, Ar–), 6.92 (d, 1H, J = 7.2 Hz, Ar–),
1
3
7
.22 (s, 1H, Ar–), 8.74 (s, 1H, N–H); C NMR (DMSO ? CDCl , 100 MHz)/d
3
(
ppm): 28.16, 28.69, 32.26, 44.78, 49.93, 56.31, 109.12, 120.72, 121.06, 121.37,
1
1
23.68, 126.15, 126.88, 128.87, 131.68, 132.04, 132.59, 137.38, 149.57, 156.18,
?
92.92; EI-MASS (m/z, %): 386 (M , 26), 388 (M?2 , 16), 390 (M?4 , 6), 241
?
?
(100), 149 (66), 83 (57), 77 (30), 57 (65), 55 (45); Anal. Calcd. For C H Cl N O:
21 20 2 2
C 65.12, H 5.20, N 7.23, Found C 65.16, H 5.25, N 7.28.
3
,3-Dimethyl-2,3,4,5,10,11-hexahydro-11-[(4-chloro-3-nitro)phenyl]-1H-dibenzo
b,e][1,4] diazepin-1-one (3i)
[
Pale yellow solid, yield: 87 %; m.p. = 196–197 °C; R = 0.125 (1:1 Ethylacetate/
f
-
1
n-Hexane); UV–Vis: kmax = 348 nm; IR (KBr)/t (cm ): 3305, 3240, 3039, 2958,
1
1
600, 1381, 1532, 1339, 1426, 1276; H NMR (DMSO ? CDCl , 400 MHz)/d
3
(
CH –), 2.54 (s, 2H, –CH –C=O), 5.77 (s, 1H, N–H), 6.08 (s, 1H, C–H), 6.50 (d, 1H,
ppm): 1.02 (s, 3H, CH –), 1.07 (s, 3H, CH –), 2.13 (A.Bq, 2H, J = 16.0 Hz,
3 3
2
2
J = 8.0 Hz, Ar–), 6.59 (m, 2H, Ar–), 6.91 (d, 1H, J = 8.0 Hz, Ar–), 7.24–7.29
(
1
m, 2H, Ar–), 7.68 (s, 1H, Ar–), 8.74 (s, 1H, N–H); C NMR (DMSO ? CDCl3,
3
1
1
1
00 MHz)/d (ppm): 28.04, 28.75, 32.19, 44.69, 49.84, 56.02, 109.07, 120.75,
20.85, 121.18, 123.36, 123.63, 124.85, 131.21, 131.44, 132.66, 138.04, 146.18,
?
47.33, 155.94, 192.9; EI-MASS (m/z, %): 397 (M , 21), 399 (M?2 , 4), 241
?
(100), 149 (47), 83 (47), 77 (27), 69 (81), 57 (91), 55 (67); Anal. Calcd. For
C H ClN O : C 63.40, H 5.07, N 10.56, Found C 63.46, H 5.13, N 10.64.
2
1
20
3 3
3,3-Dimethyl-2,3,4,5,10,11-hexahydro-11-[(4-methyl)phenyl]-1H-dibenzo[b,e][1,4]
diazepin-1-one (3j)
Pale green solid, yield: 85 %; m.p. = 224–226 °C; R = 0.125 (1:1 Ethylacetate/n-
f
-
1
Hexane); UV–Vis: kmax = 361 nm; IR (KBr)/t (cm ): 3307, 3245, 3050, 2959,
1
1
595, 1380, 1538, 1327, 1471, 1276; H NMR (DMSO ? CDCl , 400 MHz)/d
3
(
CH –), 2.01 (s, 3H, Me–), 2.52 (s, 2H, -CH –C=O), 5.69 (s, 1H, N–H), 5.69 (s, 1H,
ppm): 1.01 (s, 3H, CH –), 1.07 (s, 3H, CH –), 2.01 (A.Bq, 2H, J = 16.0 Hz,
3 3
2
2
C–H), 6.45 (d, 1H, J = 7.6 Hz, Ar–), 6.5–6.6 (m, 2H, Ar–), 6.81 (d, 2H,
J = 7.6 Hz, Ar–), 6.86 (d, 1H, J = 8.0 Hz, Ar–), 6.92 (d, J = 7.6 Hz, 2H, Ar–),
1
3
8
3
1
.53 (s, 1H, N–H); C NMR (DMSO ? CDCl , 100 MHz)/d (ppm): 27.85, 29.16,
3
2.23, 44.71, 50.09, 55.07, 56.51, 110.69, 119.86, 120.47, 121.07, 122.96, 126.35,
27.58, 127.94, 131.53, 138.87, 145.11, 155.14, 192.56; EI-MASS (m/z, %): 332
123

H. Naeimi, H. Foroughi
?
M , 43), 241 (100), 149 (55), 83 (39), 77 (41), 57 (77), 55 (46); Anal. Calcd. For
(
C H N O: C 79.48, H 7.28, N 8.43, Found C 79.53, H 7.35, N 8.49.
2
2 24 2
3,3-Dimethyl-2,3,4,5,10,11-hexahydro-11-[(4-methoxy)phenyl]-1H-dibenzo[b,e][1,4]
diazepin-1-one (3k)
Pale cream solid, yield: 82 %; m.p. = 229–231 °C; R = 0.125 (1:1 Ethylacetate/n-
f
-
1
Hexane); UV–Vis: kmax = 364 nm; IR (KBr)/t (cm ): 3301, 3238, 3015, 2956,
1
1
587, 1382, 1535, 1327, 1426, 1279; H NMR (DMSO ? CDCl , 400 MHz)/d
3
(
ppm): 1.01 (s, 3H, CH –), 1.06 (s, 3H, CH –), 2.10 (s, 3H, Me–), 2.10 (s, 1H, C–H),
3 3
2
.11 (A.Bq, 2H, J = 16.0 Hz, CH –), 2.52 (s, 2H, –CH –C=O), 5.7 (s, 1H, N–H),
2 2
6
.45 (d, 1H, J = 7.6 Hz, Ar–), 6.5–6.58 (m, 2H, Ar–), 6.81 (d, 2H, J = 8.0 Hz,
Ar–), 6.87 (d, 1H, J = 8.4 Hz, Ar–), 6.91 (d, J = 8.0 Hz, 2H, Ar–), 8.55 (s, 1H,
1
3
N–H); C NMR (DMSO ? CDCl , 100 MHz)/d (ppm): 27.82, 29.19, 32.23, 44.75,
3
5
1
2
0.04, 54.11, 56.42, 110.67, 111.46, 113.56, 119.93, 120.41, 121.05, 123.06,
?
28.89, 131.46, 138.89, 146.66, 155.21, 192.08; EI-MASS (m/z, %): 348 (M , 67),
41 (100), 149 (36), 83 (35), 77 (42), 57 (43), 55 (52); Anal. Calcd. For
C H N O : C 75.83, H 6.94, N 8.04, Found C 75.86, H 6.97, N 8.07.
22 24 2 2
3,3-Dimethyl-2,3,4,5,10,11-hexahydro-11-[(2-methoxy)phenyl]-1H-dibenzo[b,e][1,4]
diazepin-1-one (3l)
Pale cream solid, yield: 83 %; m.p. = 217–218 °C (decomp); R = 0.125 (1:1
f
1
-
Ethylacetate/n-Hexane); UV–Vis: kmax = 361 nm; IR (KBr)/t (cm ): 3369, 3306,
1
063, 2955, 1599, 1384, 1534, 1327, 1425, 1236; H NMR (DMSO ? CDCl ,
3
3
4
J = 16.0 Hz, CH –), 2.57 (s, 2H, –CH –C=O), 3.89 (s, 3H, Me–), 5.0 (s, 1H, N–H),
00 MHz)/d (ppm): 1.07 (s, 3H, CH –), 1.08 (s, 3H, CH –), 2.12 (A.Bq, 2H,
3
3
2
2
5
.95 (s, 1H, C–H), 6.28 (d, 1H, J = 7.6 Hz, Ar–), 6.45–6.55 (m, 3H, Ar–), 6.58
d, 1H, J = 7.6 Hz, Ar–), 6.75 (d, 1H, J = 8.4 Hz, Ar–), 6.86 (d, J = 7.6 Hz, 1H,
(
Ar–), 6.94 (t, 1H, J = 8.0 Hz, Ar–), 8.59 (s, 1H, N–H);
1
3
C NMR
(
DMSO ? CDCl , 100 MHz)/d (ppm): 27.95, 29.08, 32.32, 44.77, 50.05, 54.79,
3
5
1
2
6.43, 110.75, 111.47, 113.56, 119.89, 120.06, 120.40, 121.05, 123.06, 128.85,
?
31.47, 138.86, 146.65, 155.26, 159.24, 192.65; EI-MASS (m/z, %): 348 (M , 42),
41 (100), 149 (52), 83 (61), 77 (27), 57 (85), 55 (72); Anal. Calcd. For
C H N O : C 75.83, H 6.94, N 8.04, Found C 75.9, H 6.98, N 8.10.
22 24 2 2
3,3-Dimethyl-2,3,4,5,10,11-hexahydro-11-[(3-methoxy)phenyl]-1H-dibenzo[b,e][1,4]
diazepin-1-one (3m)
Pale green solid, yield: 84 %; m.p. = 225–227 °C; R = 0.125 (1:1 Ethylacetate/n-
f
-
1
Hexane); UV–Vis: kmax = 364 nm; IR (KBr)/t (cm ): 3326, 3278, 3050, 2954,
1
1
586, 1382, 1538, 1332, 1497, 1274; H NMR (DMSO ? CDCl , 400 MHz)/d
3
(
ppm): 1.01 (s, 3H, CH –), 1.06 (s, 3H, CH –), 2.12 (A.Bq, 2H, J = 16.0 Hz,
3 3
CH –), 2.52 (s, 2H, –CH –C=O), 3.55 (s, 3H, Me–), 5.64 (s, 1H, N–H), 5.72 (s, 1H,
2
2
C–H), 6.44–6.48 (m, 2H, Ar–), 6.53–6.57 (m, 2H, Ar–), 6.60 (s, 1H, Ar–), 6.62 (d,
H, J = 8.0 Hz, Ar–), 6.86 (d, 1H, J = 7.6 Hz, Ar–), 6.91 (t, 1H, J = 8.0 Hz, Ar–),
1
1
23

Facile three-component preparation of benzodiazepine…
1
3
8
3
1
.53 (s, 1H, N–H); C NMR (DMSO ? CDCl , 100 MHz)/d (ppm): 27.81, 29.18,
3
2.21, 44.72, 50.02, 54.99, 56.41, 110.64, 111.44, 113.54, 119.91, 120.08, 120.43,
21.03, 123.03, 128.87, 131.44, 138.87, 146.63, 155.24, 159.25, 192.60; EI-MASS
?
m/z, %): 348 (M , 72), 241 (100), 149 (45), 83 (31), 77 (37), 69 (34), 57 (35), 55
(
(
42); Anal. Calcd. For C H N O : C 75.83, H 6.94, N 8.04, Found C 75.86, H
2
2 24 2 2
6
.97, N 8.07.
3,3-Dimethyl-2,3,4,5,10,11-hexahydro-11-[(2-hydroxy)phenyl]-1H-dibenzo[b,e][1,4]
diazepin-1-one (3n)
Pale cream solid, yield: 84 %; m.p. = 201–202 °C; R = 0.125 (1:1 Ethylacetate/n-
f
-
1
Hexane); UV–Vis: kmax = 360 nm; IR (KBr)/t (cm ): 3622, 3302, 3238, 3100,
1
2
957, 1599, 1384, 1528, 1328,1424,1276; H NMR (DMSO ? CDCl , 400 MHz)/d
3
(
CH –), 2.56 (s, 2H, –CH –C=O), 5.18 (s, 1H, N–H), 5.93 (s, 1H, C–H), 6.35 (t, 2H,
ppm): 1.06 (s, 3H, CH –), 1.08 (s, 3H, CH –), 2.13 (A.Bq, 2H, J = 16.0 Hz,
3 3
2
2
J = 7.2 Hz, Ar), 6.38 (d, 1H, J = 6.8 Hz, Ar–), 6.50–6.55 (m, 3H, Ar–), 6.66 (d,
1
H, J = 8.0 Hz, Ar–), 6.76 (t, 1H, J = 7.2 Hz, Ar–), 6.86 (d, J = 7.2 Hz, 1H, Ar–),
3
1
8
.53 (s, 1H, N-H), 9.35 (s, 1H, O–H); C NMR (DMSO ? CDCl , 100 MHz)/d
3
(
ppm): 28.04, 29.05, 32.22, 44.71, 50.11, 56.39, 110.89, 113.22, 115.08, 118.65,
1
1
19.77, 120.43, 120.96, 122.97, 128.71, 131.47, 138.95, 146.62, 155.07, 157.26,
?
92.55; EI-MASS (m/z, %): 348 (M , 23), 241 (100), 149 (47), 83 (35), 77 (46), 57
(
40), 55 (48); Anal. Calcd. For C H N O : C 75.42, H 6.63, N 8.38, Found C
21 22 2 2
7
5.47, H 6.68, N 8.43.
3,3-Dimethyl-2,3,4,5,10,11-hexahydro-11-[(3-hydroxy)phenyl]-1H-dibenzo[b,e][1,4]
diazepin-1-one (3o)
Pale green solid, yield: 81 %; m.p. = 287–289 °C (decomp); R = 0.125 (1:1
f
-
1
Ethylacetate/n-Hexane); UV–Vis: kmax = 348 nm; IR (KBr)/t (cm ): 3447, 3307,
1
048, 2927, 1585, 1386, 1519, 1332, 1425, 1275; H NMR (DMSO ? CDCl ,
3
3
4
J = 16.0 Hz, CH –), 2.54 (s, 2H, –CH –C=O), 5.60 (s, 1H, N–H), 5.94 (s, 1H,
00 MHz)/d (ppm): 1.03 (s, 3H, CH –), 1.08 (s, 3H, CH –), 2.11 (A.Bq, 2H,
3
3
2
2
C–H), 6.37 (d, 1H, J = 7.6 Hz, Ar–), 6.48–6.57 (m, 5H, Ar–), 6.82
(
t, 1H, J = 7.6 Hz, Ar–), 6.89 (d, 1H, J = 7.6 Hz, Ar–), 8.64 (s, 1H, N–H), 8.90
1
3
(
s, 1H, O–H); C NMR (DMSO ? CDCl , 100 MHz)/d (ppm): 28.02, 29.09,
3
32.20, 44.74, 50.07, 56.36, 110.86, 113.19, 115.05, 118.60, 119.75, 120.39, 120.98,
122.94, 128.74, 131.43, 138.93, 146.59, 155.04, 157.21, 192.50; EI-MASS (m/z, %):
?
334 (M , 34), 241 (100), 149 (61), 83 (57), 77 (25), 69 (84), 57 (90), 55 (72); Anal.
Calcd. For C H N O : C 75.42, H 6.63, N 8.38, Found C 75.46, H 6.66, N 8.42.
21 22 2 2
11-(4-Chlorophenyl)-3,3,9-trimethyl-2,3,4,5,10,11-hexahydro-1H-dibenzo[b,e][1,4]
diazepin-1-one
Yellowish solid, yield: 80 %; m.p. = 230–234 °C; R = 0.105 (1:1 Ethylacetate/n-
f
-
1
Hexane); UV–Vis: kmax = 332 nm; IR (KBr)/t (cm ): 3507, 3108, 3084, 2895,
1
1
562, 1542, 1521, 1362, 1408, 1265; H NMR (DMSO ? CDCl , 400 MHz)/d
3
123

H. Naeimi, H. Foroughi
(ppm): 1.11 (s, 3H, CH –), 1.20 (s, 3H, CH –), 2.07 (m, 2H, CH –), 2.24 (s, 3H,
CH –Ar), 2.63 (s, 2H, –CH –C=O), 5.81 (s, 1H, C–H), 6.62 (d, 1H, J = 7.7 Hz,
3
3
2
3
2
Ar–), 6.79 (s, 1H, Ar–), 6.95 (d, 1H, J = 7.7 Hz, Ar–), 7.06 (d, 2H, J = 8.1 Hz,
3
1
Ar–), 7.24 (d, 1H, J = 8.1 Hz, Ar–), 8.62 (br, 2H, N–H);
(
C NMR
DMSO ? CDCl , 100 MHz)/d (ppm): 20.15, 26.15, 26.19, 34.19, 45.01, 50.35,
3
5
5.08, 110.01, 121.35, 122.04, 122.38, 124.20, 124.87, 129.45, 132.81, 133.74,
47.25, 152.67, 153.42, 195.47; Anal. Calcd. For C H ClN O: C 72.02, H 6.32,
Cl 9.66, N 7.64, Found C 71.84, H 6.01, N 7.40.
1
2
2
23
2
Results and discussion
ZnS nanoparticles were prepared according to the procedure of previously reported
works [41–44, 46] from the reaction of Zn(OAc) . 2H O and thioacetamide (TAA)
2
2
with ethylene glycol under microwave irradiation and were used as heterogeneous
catalyst in the organic reaction (Scheme 1).
Catalyst characterization
FT-IR studies
The FT-IR spectra (Fig. 2) of ZnS NPs samples showed very low absorption bands
-
1
at 478, 1050 and 1415 cm , which were assigned to the fundamental stretching and
bending vibrations of related to Zn–S bond. A broad intense absorption between
-
1
000 and 3700 cm is observed due to O–H vibration of water molecules, as
3
characterized by its bending vibration at 1627 cm [41–44, 46].
-
1
PL studies
Photo-luminescent (PL) spectrum is an important tool to evaluate the defects and
optical properties of ZnS NPs as a photonic material [45]. Furthermore,
photoluminescence spectrum is sensitive to synthetic conditions, size, and shape
of NPs.
Figure 3 shows the PL spectra of ZnS NPs recorded with an absorbance
wavelength of 300 nm at room temperature. Broadening of the absorption peak
could be attributed to both size distribution and increase in the surface states, owing
to the increase in surface to volume ratio for ZnS NPs. Also, the results of PL
Scheme 1 Synthesis of 4-substituted-1,5-benzodiazepine under grinding conditions
1
23

Facile three-component preparation of benzodiazepine…
Fig. 2 The IR spectrum of ZnS NPs catalyst
Fig. 3 The PL spectrum of ZnS NPs catalyst
spectra are consistent with those of XRD, which indicate particles with better
crystalline and apposite size.
Powder X-ray diffraction technique (XRD)
The X-ray diffraction patterns of ZnS nanoparticles are shown in Fig. 4. The
position and relative intensities of all peaks confirm well with the standard XRD
pattern of ZnS nanoparticles, indicating retention of the crystalline cubic spinel
structure during of NPs. The average NPs core diameter was calculated to be 6 nm
123

H. Naeimi, H. Foroughi
Fig. 4 The XRD patterns of ZnS NPs catalyst
Fig. 5 The EDX spectum of ZnS NPs catalyst
from the XRD results by Scherrer’s equation, D = kk/bcosh, where k is a constant
˚
(
generally considered as 0.94), k is the wavelength of Cu Ka (1.54 A), b is the
corrected diffraction line full-width at half-maximum (FWHM), and h is Bragg’s
angle. Average size of the prepared ZnS NPs has been found to be 6 nm. X-ray
powder diffraction (XRPD)-spectra showed the Bragg reflections for ZnS NPs
centered at 2H: The broad hump 28.8° (1 1 1), 48.2° (2 2 0) and 57.2° (3 1 0).
1
23

Facile three-component preparation of benzodiazepine…
Electron diffraction X-ray (EDX) analysis
The chemical composition of the product was further examined with energy
dispersive X-ray spectrometry (EDX). Purity was shown in the spectrum (Fig. 5),
the strong peaks of Zn and S, indicating that the products were pure ZnS NPs. A
relatively weak O peak in the spectrum probably originates from unavoidable
surface-adsorption of oxygen onto the spheres from exposure to air during the
sample processing [41–46].
Scanning electron microscopy (SEM) analysis
Typical SEM images depicted that the nanoparticles were randomly oriented with
an average 50 nm and were produced at high density. They uniformly covered the
entire substrate. The ZnS NPs are disperses of nanometers size and less 50 nm in
diameter. Also, SEM images (Fig. 6) of these NPs show clear lattice balls, which
confirm their spherical nature [41–46]. The corresponding XRD pattern demon-
strates that these NPs all grow along in three dimensions, and EDX spectra indicate
that Zn and S are major elements.
Transmission electron microscopy (TEM) analysis
TEM images of ZnS NPs catalyst are shown in Fig. 7. The TEM images of
amorphous ZnS NPs showed the particle sizes to be between 20 and 30 nm,
respectively, which is also in good agreement with particle size estimated from
XRD spectra by applying the Scherrer equation [41–46]. The techniques, XRD and
TEM showed similar trend in continuous increment in particle size (20–30 nm).
TEM images ZnS NPs showed the narrow range of particle size distribution, except
for ZnS NPs, where smaller particles in the range of 5–6 nm and larger particles of
5
0–60 nm can be seen. There is good correlation between average particle size
calculated by XRD) and average pore-size distribution (TEM) for synthesized
(
materials, but this is possibly a result of aggregation of nano-sized particles, as
explained in earlier sections.
Fig. 6 The SEM of ZnS NPs catalyst
123

H. Naeimi, H. Foroughi
Fig. 7 The TEM image of ZnS NPs catalyst
Table 1 Diverse used catalyst in a model reaction
a
Yield (%)
Entry
Catalyst
Time (min)
1
2
3
4
5
6
7
8
9
MeSO
CF COOH
CuI
Fe
3
H
60
70
55
50
40
35
30
28
35
35
200
19
40
45
50
50
31
30
37
20
42
45
30
85
3
3
O
4
MgO
ZnO
ZnS
Zn(CH
ZnCl
ZnBr
None
ZnS NPs
3
COO)
2
2
Á2H O
2
1
1
1
0
1
2
2
b
All the reactions were carried out using 10 % mol of catalyst, 1 mmol of o-phenylenediamine, 1 mmol of
dimedone and 1 mmol of p-Cl-benzealdehyde at 70 °C
a
Isolated yields
b
ZnS NPs (10 % mol)
1
23

Facile three-component preparation of benzodiazepine…
Catalytic studies
The reaction was used in various catalysts such as CF COOH, MeSO H, Fe O ,
3
3
3 4
CuI, MgO, ZnO and ZnS; but none of the above catalysts was found to be more
effective than ZnS NPs in this reaction (Table 1). Nevertheless, the reaction at
2
5 °C did not give the desired product and the starting material was recovered,
whereas at 55 °C, only trace of the desired product was identified by TLC. Also, the
reaction was checked in the presence of zinc chloride and zinc bromide salts as
catalyst, and the results were added to Table 1, as entries 9, 10. It is clearly shown
that the ZnBr and ZnCl are not good catalysts for this reaction, because significant
2
2
amounts of side products were formed and the main product was very low in yield.
It was found that ZnS NPs catalyst was selected for the reaction and the desired
product was obtained at 70 °C under grinding condition in excellent yield (Table 1,
entry 12).
Also, optimization of the temperature and amounts of catalyst in the reaction of
dimedone, o-phenylenediamine and aromatic aldehydes was selected as the model
reaction for one-pot synthesis of the corresponding 1,5-benzodiazepine derivatives.
In follow-up research, the model reaction was carried out by using various amounts
of ZnS NPs. The optimum amount of ZnS NPs was 10 mol%, as shown in Table 2.
So far, we examined a range variety of aldehydes with various substituents to
establish the catalytic importance of ZnS nanoparticles for this reaction. A wide
range of 1, 2 and 3-substituted benzaldehydes undergo this one-pot multicomponent
synthesis with dimedone and o-phenylenediamine toward 4-substituted-1,5-benzo-
diazepine in high yields (Table 3). In all cases, we observed the almost same
performance towards this cyclo condensation to give the desired product (Table 3).
Table 2 Optimization of catalyst amount in the reaction
a
Yield (%)
Entry
Catalyst loading (g)
Time (min)
1
2
3
4
5
0.005
0.008
0.01
17
16
19
19
18
35
55
85
85
84
0.013
0.015
All the reactions were carried out using 1 mmol of o-phenylenediamine, 1 mmol of dimedone and
1
mmol of benzealdehyde at 70 °C
Isolated yields
a
123

H. Naeimi, H. Foroughi
Table 3 Synthesis of 4-substituted-1,5-benzodiazepine (3a-o) catalyzed by ZnS nanoparticles under
grinding condition
a
Time Yield Lit.
Entry Aldehyde
Product
Found
TON/
(
min) (%)
[30–40]
Mp.(°C)
M.p. (°C) TOF-
(min )
1
1
C
6
H
5
18
84
250–252 246–248 13,520/
.075
0
3
a
b
2
p-NO
2
ÁC
6
H
4
17
89
274–275 280–281 12,020/
.092
0
3
b
b
b
3
o-NO
2
ÁC
6
H
4
17
88
115–117 230–232 13,480/
.096
0
3
c
4
m-NO
2
ÁC
6
H
4
16
88
161–168 195–197 16,550/
.101
1
3
d
5
p-ClÁC
6
H
4
19
85
235–237 235–237 14,560/
.975
0
3
e
1
23

Facile three-component preparation of benzodiazepine…
Table 3 continued
a
Time Yield Lit.
Entry Aldehyde
Product
Found
TON/
(
min) (%)
[30–40]
Mp.(°C)
M.p. (°C) TOF-
(min )
1
b
233–235 239–240 15,280/
b
6
7
o-ClÁC
6
H
4
22
86
0
.955
3
f
b
2,3-ClÁC
6
H
3
19
89
–
256–258 14,820/
.058
1
3
g
b
8
2,4-ClÁC
6
H
3
21
90
252
230–232 12,880/
.920
0
3
h
9
4-Cl-3-
NO
17
87
–
196–197 14,550/
0.970
2
ÁC
6 3
H
3
i
b
10
p-MeÁC
6
H
4
19
85
157–158 224–226 16,200/
.012
1
3
j
123

H. Naeimi, H. Foroughi
Table 3 continued
a
Time Yield Lit.
Entry Aldehyde
Product
Found
TON/
(
min) (%)
[30–40]
Mp.(°C)
M.p. (°C) TOF-
(min )
1
11
p-OMeÁC
6
H
4
18
82
203–205 229–231 15,800/
.877
0
3
k
b
b
1
2
3
o-OMeÁC
6
H
4
23
25
83
84
213–215 217–218 16,700/
.982
0
3
l
1
m-OMeÁC
6
H
4
–
225–227 16,510/
.971
0
3
m
1
1
4
5
o-OHÁC
6
H
4
22
23
84
81
164–166 201–202 16,580/
.921
0
3
n
b
m-OHÁC
6
H
4
–
287–289 14,230/
.748
0
3
o
1
23

Facile three-component preparation of benzodiazepine…
Table 3 continued
a
Time Yield Lit.
Entry Aldehyde
Product
Found
TON/
(
min) (%)
[30–40]
Mp.(°C)
M.p. (°C) TOF-
(min )
1
c
6
1
p-ClÁC
6
H
4
26
80
–
230–234 14,028/
.884
0
3
p
All the reactions were carried out using 10 mol% of catalyst, 1 mmol of o-phenylenediamine, 1 mmol of
dimedone and 1 mmol of p-Cl-benzaldehyde at 70 °C
a
Isolated yields
b
Decomposition point
c
The amine substrate for this reaction was 2,3-diaminotoluene
Aliphatic aldehydes gave the corresponding 4-substituted-1,5-benzodiazepine in
lower yield (15–20 %) than aromatic aldehydes (81–90 %). Moreover, the 2,3-
diaminotoluene was used as diamine substrate in this protocol (Table 3, entry 16),
and the results showed high yield of the related product in this reaction. All the
synthesized 4-substituted-1,5-benzodiazepines have been characterized on the basis
of elemental and spectral studies.
1
13
The structure of the obtained products was confirmed by FT-IR, H NMR,
NMR and EI-MASS spectroscopic data. The FT-IR spectrum of the 3i as an
C
-
example exhibited a broad band at 3305 and 3240 cm that is related to amine
1
-
protons (2 NH groups), bands at 3039 and 2958 cm related to CH, CH , and CH
1
2
3
-
groups, and strong bands at 1600 and 1381 cm , representing the presence of
1
-
general carbonyl groups (C=O stretching). Strong bands at 1532 and 1339 cm in
1
-
1
FT-IR spectrum confirm the presence of C–N stretching, a band at 1426 cm is
-
related to C=C stretching band, and a strong band at 1276 cm confirms the
1
1
presence of C–O bond stretching. In addition, the H NMR spectrum of compound
3
i exhibited two singlet bands for two methyl groups at d = 1.02 ppm and
d = 1.07 ppm, a AB quartet signal at d = 2.13 ppm with J = 16.0 Hz was shown
for CH protons. Also, a signal at d = 2.54 ppm for CH –C=O protons and a signal
2
2
at d = 5.77 ppm for NH proton are observable. The CH proton was shown at
d = 6.08 ppm, aromatic protons at d = 6.50–7.68 ppm, and NH proton at
1
3
d = 8.74 ppm. Also, the C NMR spectrum of compound 3i was shown to have
distinct 21 carbons, in agreement with proposed structure. Finally, the mass spectra
of product 3i displayed a molecular ion peak at the appropriate m/z value [11, 26].
123

H. Naeimi, H. Foroughi
One heterogeneous catalyst that has obtained attention is ZnS NPs. This excellent
particle shows remarkable activity and selectivity for the coupling of aldehydes with
dimedone and o-phenylenediamine by increasing the surface area and decreasing
size. The lower stability of the ZnS-H bond and a special effect between the acid–
base properties of ZnS sites found in the reaction are still essential for high yields.
Grinding condition was even required and the addition of Lewis acid ZnS NPs was
necessary to facilitate the reaction.
The formation of 4-substituted-1,5-benzodiazepine from o-phenylenediamine,
dimedone and aldehyde in the presence of ZnS NPs as catalyst can be explained by a
tentative mechanism that is presented in Scheme 2. One molecule of dimedone(1) was
firstly condensed with an activated o-phenylenediamine (2) to provide intermediate
A and water, which can be regarded as a fast Knoevenagel addition. Then, the active
molecule of aromatic aldehyde (3) reacted with intermediate A via conjugate Michael
addition to produce the intermediate B and water, which undergoes intramolecular
cyclodehydration to give the 4-substituted-1,5-benzodiazepine (5, 6).
Scheme 2 Proposed reaction mechanism
1
23

Facile three-component preparation of benzodiazepine…
Fig. 8 Reusability of ZnS NPs
Finally, we surveyed catalyst reusability in the MCRs of benzaldehyde with
dimedone and o-phenylenediamine as a model reaction under the optimized reaction
condition. After completion of the reaction, the reaction mixture was dissolved in
ethanol and the catalyst was insoluble in ethanol and centrifuged to separate. The
ZnS nanoparticles were washed three to four times with ethylacetate and dried at
60 °C for 1 h. The recycled catalyst could be reused five times without any decrease
in catalytic activity so that the yields were ranged from 85 to 74 % (Fig. 8).
Conclusion
In the present work, ZnS nanoparticles were prepared and well characterized. The
obtained ZnS nanoparticles play a role in the reaction mechanism for three-
component coupling of o-phenylenediamine, dimedone and aldehydes in order to
synthesize some heterocyclic compounds. The pure products were obtained in high
yields and short reaction times. The Lewis acidity of the catalyst plays significant
role in catalysis, and on the basis of our knowledge, enhancing the rate and yield of
the reaction by providing the interfacial bonds between the heterogeneous catalyst
and substrates could be performed.
Acknowledgments The authors are grateful to University of Kashan for supporting this work by Grant
No.: 159148/49.
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