Nanosilica-bonded N-(propylsulfonyl) piperazine-N-sulfamic acid as recyclable catalyst for synthesis of 1,1′-(arylmethylene) diureas and 1,3,5-triazinane-2,4-dithiones

Article abstract of DOI:10.1007/s11164-015-2376-8

Nanosilica-bonded N-(propylsulfonyl) piperazine-N-sulfamic acid was easily prepared by functionalizing silica nanoparticles and characterized by thermogravimetric analysis, scanning electron microscopy, infrared (IR) spectroscopy, elemental analyses, and

Full text of DOI:10.1007/s11164-015-2376-8

Res Chem Intermed
DOI 10.1007/s11164-015-2376-8
Nanosilica-bonded N-(propylsulfonyl) piperazine-
N-sulfamic acid as recyclable catalyst for synthesis
of 1,10-(arylmethylene) diureas and 1,3,5-triazinane-
2,4-dithiones
Parizad Rezaee1 Jamal Davarpanah2
•
Received: 26 September 2015 / Accepted: 24 November 2015
Ó Springer Science+Business Media Dordrecht 2016
Abstract Nanosilica-bonded N-(propylsulfonyl) piperazine-N-sulfamic acid was
easily prepared by functionalizing silica nanoparticles and characterized by ther-
mogravimetric analysis, scanning electron microscopy, infrared (IR) spectroscopy,
elemental analyses, and ion-exchange pH analysis. The catalytic activity of the
functionalized nanosilica for preparation of 1,10-(arylmethylene) diureas from
reaction of aldehydes with urea derivatives was examined. The efficient effect of
this catalyst led to preparation of 1,10-(arylmethylene) diureas in high yield. The
reaction of aldehydes with thiourea under the same reaction conditions afforded
high yield of 1,3,5-triazinane-2,4-dithiones. Catalyst reusability, simple workup
procedure, and short reaction time are other advantages of this protocol.
Keywords 1,10-(Arylmethylene) diureas Á 1,3,5-Triazinane-2,4-dithiones Á
Functionalized nanosilica Á Bisurides Á Interphase catalyst Á Aldehydes
Introduction
Compounds bearing amide and bisamide groups are important intermediates in
organic synthesis since these groups can be easily transformed into other
functionalities (such as gem-diaminoalkyl and aminoalkyl group) [1–4]. Several
geminal bisurea compounds have been synthesized from thermoreversible
organogelators with a number of organic solvents at very low concentration which
are stable to temperatures higher than 100 °C [5]. Also, Kappe et al. reported
preparation of bisurea, which Juaristi et al. used as an intermediate for a two-
&
Parizad Rezaee
p.rezaee@iauabadan.ac.ir
1
2
Department of Chemical Engineering, Abadan Branch, Islamic Azad University, Abadan, Iran
Chemistry Department, Production Technology Research Institute –ACECR, Ahvaz, Iran
123

P. Rezaee, J. Davarpanah
component variation of the Biginelli reaction in the presence of chiral ligands [6, 7].
Many compounds bearing bisurea groups have been investigated as fluorescent
chemosensors for anion recognition [8–10]. Interpolation of urea moieties in rigid
spacers, such as adamantane A and B, resulted in a new class of anion receptors with
two urea moieties as a binding site for study of binding ability and selectivity in
supramolecular anion chemistry [11].
Use of organocatalysts modified to include a (thio)urea component (catalyst C and
D) has emerged in recent years for a range of synthetically useful transformations [12].
Urea derivatives such as 3-haloacylamino benzoylurea (HBU) analogues E have been
proposed by Jiang et al., with the benzoylurea group being indicated to be a key
intermediate for good anticancer activity [13–15], while N-(2-chlorobenzoyl)-N0-[3-
chloro-4(5-trifluoromethyl-2-pyridyloxy)phenyl] urea F showed high antitumor
activity in vivo [16].
These reports prompted us to disclose our findings which have been developed
independently and successfully applied to synthesis of substituted ureas.
Some protocols have been reported in literature for preparation of 1,10-
(arylmethylene) diurea derivatives in acidic conditions, e.g., with molybdate and
silica sulfuric acids [17], Al(H2PO4)3 [18], and trimethylsilyl chloride [19].
However, these reactions were limited to a few bisurea derivatives [17] or by low
product yield [18, 19] or use of isocyanates and very toxic and ecologically
dangerous phosgene or its derivatives as substrate [20–24]. Therefore, the search for
new or reclaimed procedures continues unabated, driven by the need for higher
yield and ecological constraints. On the other hand, synthetic methodologies based
on green-chemistry processes are of increasing interest in organic chemistry. Hence,
there is a need for the design and preparation of new versions of catalysts to
circumvent these problems without considerable loss of catalytic power. One way to
reach this goal is to immobilize one or more components of the catalytic system
onto a large-surface-area solid carrier to create new organic–inorganic hybrid
(interphase) catalysts [25–30]. Based on this idea, several types of sulfonic-acid-
functionalized silica and mesoporous organosilica have been synthesized and
applied as alternatives to traditional resins for catalyzing chemical transformations
[31–50].
Recently, we prepared a polymer-supported catalyst to combine the advantages
of both homogeneous and heterogeneous catalysts in preparation of symmetrical
bisamides [51]. The purpose of the present article is to summarize the data on one-
O
O
O
R'
O
Catalyst
R
R
R
N
H
NH2
2
R'
H
N
H
N
H
N
H
N
H
Toluene, Reflux
R= H, Alkyl, Aryl
R'=H, Aryl
Scheme 1 Synthesis of 1,10-(arylmethylene) diureas in presence of nanosilica-bonded N-
(propylsulfonyl) piperazine-N-sulfamic acid
123

Nanosilica-bonded N-(propylsulfonyl) piperazine-N-…
pot preparation of 1,10-(arylmethylene) diurea derivatives in good yield by
condensation of aromatic aldehyde and urea derivatives in the presence of
sulfonic-acid-functionalized nanosilica as catalyst under thermal conditions
(Scheme 1). This method not only affords the products in high yield, but also
avoids the problems associated with catalyst cost, handling, safety, and pollution.
Experimental
Materials and methods
Starting materials used in the reactions were supplied commercially by Aldrich or
Merck Chemical Co. Nanosilica with 12.6 nm average particle size was purchased
1
from Nissan Chemical (Tokyo, Japan). H and 13C nuclear magnetic resonance
(NMR) spectra were recorded on a Bruker DRX-400 AVANCE (400 and 100 MHz
for 1H and 13C, respectively) in dimethyl sulfoxide (DMSO)-d6 as solvent.
Thermogravimetric analysis (TGA) was carried out on a Stanton Redcraft STA-780
(London, UK). Scanning electron microscopy (SEM) images were observed using a
CAMScan-MV2300 instrument (England). X-ray powder diffraction (XRD)
patterns of the PIs were recorded using an X-ray diffractometer (XRD, GBC
MMA Instrument) with Be-filtered Cu Ka radiation. Melting points were determined
on a Thermo Scientific IA9200 and are uncorrected. Chemical shifts are reported on
the d scale relative to internal standard Me4Si. Mass spectra were obtained on an
Agilent Technologies instrument, and IR spectra were determined on a Bruker
instrument.
Preparation of 3-mercaptopropyl silica (MPS, 1)
Silica nanoparticles (12.6 nm average particle size) were activated by relaxing in
HCl (4 M) for 24 h, then washed with distilled water and dried completely [52].
Then, the activated silica gel (10 g) was refluxed with 3-mercaptopropy-
ltrimethoxysilane (MPTMS, 5 mL) in dry toluene for 18 h. The solid materials
were filtered off and washed with hot toluene for 12 h in a continuous extraction
apparatus (Soxhlet) and then dried in an oven at 110 °C overnight to obtain surface-
bonded thiol group [42].
Preparation of solid-based silica sulfonic acid (2)
For oxidation of thiol groups of the modified silica (MPS, 5 g), 30 % H2O2 solution
(50 mL) and 98 % H2SO4 (two drops) was added to a flask in methanol (15 mL) for
12 h at ambient temperature, and the solid was filtered off and washed with
deionized water. To ensure that all the sulfonic acid groups were protonated, the
solid was suspended in 10 wt% H2SO4 solution (30 mL) for 4 h. The solid was then
filtered off, washed thoroughly with deionized water, and dried at 120 °C overnight
[43].
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P. Rezaee, J. Davarpanah
Preparation of solid-based silica sulfonyl chloride (3)
The resulting mixture of sulfonic acids 2 was finally heated in excess thionyl
chloride at reflux for 10 h to give sulfonyl chloride 3 [53]. The suspension was
filtered and washed by diethyl ether, and dried under vacuum. The product is
denoted SiSO2Cl.
Preparation of 3-piperazine-N-(propylsulfonyl) silica (4)
A suspension of 4.0 g SiSO2Cl in 150 cm3 xylene was allowed to react with 1.5 g
piperazine at 70 °C, in the presence of triethylamine (1 mL) as proton abstractor,
under continuous stirring and nitrogen atmosphere for 48 h. The product was
filtered, washed with xylene and then hot ethanol for 12 h in a Soxhlet apparatus,
and then dried under vacuum [54].
Preparation of silica-bonded N-(propylsulfonyl) piperazine-N-sulfamic acid
(5)
To a magnetically stirred mixture of 4 (3 g) in CHCl3 (30 mL), chlorosulfonic acid
(2 mL) was added dropwise at 0 °C over 2 h. After completion of the addition, the
mixture was stirred for another 2 h, then the mixture was filtered, washed with
ethanol (30 mL) and sonicated with ethanol (30 mL), then filtered using a sintered
glass funnel and dried at room temperature to afford silica-bonded N-(propylsul-
fonyl) piperazine-N-sulfamic acid nanoparticles (5, SBNPSPSANPs) as cream
powder [44].
General procedure for synthesis of 1,10-(arylmethylene) diurea derivatives
A mixture of aldehyde (1 mmol), urea (2 mmol), and catalyst (0.07 g) in toluene
(10 mL) was heated under reflux, and the reaction was followed by thin-layer
chromatography (TLC) analysis. After vigorously stirring for the appropriate time, a
white solid was obtained. The mixture was filtered, the residue was diluted with hot
ethanol (30 mL) or dimethylformamide (DMF, 5 mL), and the catalyst was filtered
using a sintered glass funnel. The catalyst was washed with hot ethanol and the
combined solution concentrated under vacuum to afford the product, which was
purified by recrystallization. All yields refer to isolated products after purification.
All products were characterized by 1H and 13C NMR spectra and melting point. The
analytical data for these compounds are presented below.
1,10-((4-Nitrophenyl)methylene)diurea (Table 3, entry 1) White solid, m.p.
188–190 °C. IR (KBr, cm-1): 3458, 3314, 1655, 1510, 1351, 1275, 1191, 1014.
1H NMR (400 MHz, DMSO-d6): dH (ppm) 5.79 (s, 4H, 2NH2), 6.17 (t, J = 8.4 Hz,
1H, CH), 6.96 (d, J = 8.4 Hz, 2H, 2NH), 7.57 (d, J = 8.4 Hz, 2H, Ar–CH), 8.22 (d,
J = 8.8 Hz, 2H, Ar–CH). 13C NMR (100 MHz, DMSO-d6): dC (ppm) 59.1, 123.7,
127.7, 146.9, 151.1, 158.1. Anal. calc. for C9H11N5O4 (253.21): C, 42.69; H, 4.38;
N, 27.66; found: C, 42.61; H, 4.30; N, 27.59.
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Nanosilica-bonded N-(propylsulfonyl) piperazine-N-…
1,10-((4-Chlorophenyl)methylene)diurea (Table 3, entry 2) White solid, m.p.
190–192 °C. IR (KBr, cm-1): 3402, 2923, 2856, 1738, 1698, 1498, 1234, 1091. 1H
NMR (400 MHz, DMSO-d6): dH (ppm) 5.71 (s, 4H, 2NH2), 6.08 (t, J = 8.4 Hz, 1H,
CH), 6.78 (d, J = 8.4 Hz, 2H, 2NH), 7.32 (d, J = 8.8 Hz, 2H, Ar–CH), 7.40 (d,
J = 8.8 Hz, 2H, Ar–CH). 13C NMR (100 MHz, DMSO-d6): dC (ppm) 59.0, 128.3,
128.4, 128.4, 131.9, 158.0. Anal. calc. for C9H11ClN4O2 (242.66): C, 44.55; H,
4.57; N, 23.09; found: C, 44.48; H, 4.47; N, 23.14.
1,10-((3-Bromophenyl)methylene)diurea (Table 3, entry 3) White solid, m.p.
210–212 °C. IR (KBr, cm-1): 3436, 3303, 2923, 1665, 1613, 1525, 1375, 1197,
1
1133. H NMR (400 MHz, DMSO-d6): dH (ppm) 5.71 (s, 4H, 2NH2), 6.08 (t,
J = 8.4 Hz, 1H, CH), 6.81 (d, J = 8.4 Hz, 2H, 2NH), 7.31 (d, J = 5.2 Hz, 2H, Ar–
CH), 7.44–7.47 (m, 1H, Ar–CH), 7.48 (s, 1H, Ar–CH). 13C NMR (100 MHz,
DMSO-d6): dC (ppm) 59.0, 121.8, 125.7, 129.1, 130.2, 130.7, 146.1, 158.0. Anal.
calc. for C9H11BrN4O2 (287.11): C, 37.65; H, 3.86; N, 19.51; found: C, 37.59; H,
3.80; N, 19.42.
1,10-((4-Cyanophenyl)methylene)diurea (Table 3, entry 4) White solid, m.p.
221–223 °C. IR (KBr, cm-1): 3462, 3300, 2923, 2232, 1655, 1560, 1369, 1205,
1
1019. H NMR (400 MHz, DMSO-d6): dH (ppm) 5.76 (s, 4H, 2NH2), 6.12 (t,
J = 8.0 Hz, 1H, CH), 6.89 (d, J = 8.0 Hz, 2H, 2NH), 7.49 (d, J = 8.0 Hz, 2H, Ar–
CH), 7.82 (d, J = 6.4 Hz, 2H, Ar–CH). 13C NMR (100 MHz, DMSO-d6): dC (ppm)
59.2, 110.0, 119.3, 127.5, 132.5, 158.0. Anal. calc. for C10H11N5O2 (233.23): C,
51.50; H, 4.75; N, 30.03; found: C, 51.42; H, 4.65; N, 30.13.
1,10-(Naphthalen-2-ylmethylene)diurea (Table 3, entry 5) White solid, m.p.
208–210 °C. IR (KBr, cm-1): 3439, 3303, 3059, 2924, 1663, 1611, 1589, 1508,
1
1381, 1287, 1178, 1132. H NMR (400 MHz, DMSO-d6): dH (ppm) 5.41 (s, 4H,
2NH2), 6.28 (t, J = 8.4 Hz, 1H, CH), 6.83 (d, J = 8.4 Hz, 2H, 2NH), 7.47–7.52 (m,
4H, Ar–CH), 7.81 (s, 1H, Ar–CH), 7.89 (d, J = 8.4 Hz, 2H, Ar–CH). 13C NMR
(100 MHz, DMSO-d6): dC (ppm) 59.6, 124.4, 125.3, 126.2, 126.6, 127.9, 128.2,
128.2, 132.6, 133.0, 153.1, 158.1. Anal. calc. for C13H14N4O2 (258.28): C, 60.45; H,
5.46; N, 21.69; found: C, 60.39; H, 5.37; N, 21.60.
1,10-((4-Nitrophenyl)methylene)bis(3-methylurea) (Table 3, entry 6) White
solid, m.p. 226–227 °C. IR (KBr, cm-1): 3365, 3313, 3073, 2949, 1636, 1584,
1
1517, 1419, 1384, 1274, 1210. H NMR (400 MHz, DMSO-d6): dH (ppm) 2.55 (d,
J = 4.4 Hz, 6H, 2CH3), 6.11 (brs quartet, J = 4.8 Hz, 2H, 2NH), 6.20 (t,
J = 8.0 Hz, 1H, CH), 6.90 (d, J = 8.0 Hz, 2H, 2NH), 7.56 (d, J = 8.4 Hz, 2H,
Ar–CH), 8.21 (d, J = 8.8 Hz, 2H, Ar–CH). 13C NMR (100 MHz, DMSO-d6): dC
(ppm) 26.6, 59.4, 123.7, 127.7, 146.8, 151.3, 157.9. Anal. calc. for C11H15N5O4
(281.27): C, 46.97; H, 5.38; N, 24.90; found: C, 46.89; H, 5.31; N, 24.84.
1,10-((4-Cyanophenyl)methylene)bis(3-methylurea) (Table 3, entry 7) White
solid, m.p. 242–243 °C. IR (KBr, cm-1): 3350, 3317, 2945, 2229, 1641, 1581,
1
1424, 1274, 1173, 1076, 1022. H NMR (400 MHz, DMSO-d6): dH (ppm) 2.55 (d,
J = 4.4 Hz, 6H, 2CH3), 6.09 (brs quartet, J = 4.4 Hz, 2H, 2NH), 6.17 (t,
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P. Rezaee, J. Davarpanah
J = 8.0 Hz, 1H, CH), 6.85 (d, J = 8.0 Hz, 2H, 2NH), 7.48 (d, J = 8.4 Hz, 2H, Ar–
CH), 7.80 (d, J = 8.4 Hz, 2H, Ar–CH). 13C NMR (100 MHz, DMSO-d6): dC (ppm)
26.6, 59.5, 110.0, 119.4, 127.5, 132.5, 149.1, 158.0. Anal. calc. for C12H15N5O2
(261.28): C, 55.16; H, 5.79; N, 26.80; found: C, 55.12; H, 5.69; N, 26.73.
1,10-((4-Chlorophenyl)methylene)bis(3-methylurea) (Table 3, entry 8) White
solid, m.p. 198–201 °C. IR (KBr, cm-1): 3345, 3325, 2944, 2814, 1639, 1588,
1
1487, 1421, 1273, 1176, 1087. H NMR (400 MHz, DMSO-d6): dH (ppm) 2.54 (s,
6H, 2CH3), 6.02 (brs quartet, J = 4.4 Hz, 2H, 2NH), 6.12 (t, J = 8.0 Hz, 1H, CH),
6.72 (d, J = 8.0 Hz, 2H, 2NH), 7.31 (d, J = 8.4 Hz, 2H, Ar–CH), 7.38 (d,
J = 8.8 Hz, 2H, Ar–CH). 13C NMR (100 MHz, DMSO-d6): dC (ppm) 26.6, 59.2,
128.3, 131.8, 142.4, 157.9. Anal. calc. for C11H15ClN4O2 (270.72): C, 48.80; H,
5.58; N, 20.70; found: C, 48.74; H, 5.51; N, 20.65.
1,10-(p-Tolylmethylene)bis(3-methylurea) (Table 3, entry 9) White solid, m.p.
154–156 °C. IR (KBr, cm-1): 3344, 2950, 2813, 1640, 1587, 1419, 1383, 1274,
1
1178, 1021. H NMR (400 MHz, DMSO-d6): dH (ppm) 2.54 (d, J = 4.4 Hz, 6H,
2CH3), 5.97 (brs quartet, J = 4.4 Hz, 2H, 2NH), 6.12 (t, J = 8.4 Hz, 1H, CH), 6.60
(d, J = 8.4 Hz, 2H, 2NH), 7.12 (d, J = 8.0 Hz, 2H, Ar–CH), 7.19 (d, J = 8.0 Hz,
2H, Ar–CH). 13C NMR (100 MHz, DMSO-d6): dC (ppm) 21.0, 26.6, 59.5, 126.3,
128.9, 136.4, 140.3, 158.0. Anal. calc. for C12H18N4O2 (250.30): C, 57.58; H, 7.25;
N, 22.38; found: C, 57.52; H, 7.16; N, 22.29.
1,10-((2-Chloro-5-nitrophenyl)methylene)bis(3-methylurea) (Table 3, entry 10)
White solid, m.p. 219–220 °C. IR (KBr, cm-1): 3392, 3280, 3087, 2971, 2812,
2236, 1669, 1416, 1347, 1242, 1167, 1073, 1040. H NMR (400 MHz, DMSO-d6):
1
dH (ppm) 2.53 (d, J = 4.4 Hz, 6H, 2CH3), 5.96 (brs quartet, J = 4.4 Hz, 2H, 2NH),
6.41 (t, J = 8.0 Hz, 1H, CH), 6.95 (d, J = 7.6 Hz, 2H, 2NH), 7.73 (d, J = 8.8 Hz,
1H, Ar–CH), 8.14 (dd, J = 2.8, 8.8 Hz, 1H, Ar–CH), 8.39 (d, J = 2.8 Hz, 1H, Ar–
CH). 13C NMR (100 MHz, DMSO-d6): dC (ppm) 26.6, 57.8, 123.4, 124.1, 131.3,
139.2, 142.3, 146.5, 157.6. Anal. calc. for C11H14ClN5O4 (315.71): C, 41.85; H,
4.47; N, 22.18; found: C, 41.78; H, 4.39; N, 22.22.
1,10-Methylenebis(3-methylurea) (Table 3, entry 11) White solid, m.p.
164–165 °C. IR (KBr, cm-1): 3347, 3038, 2952, 2901, 2810, 2207, 1665, 1414,
1
1382, 1267, 1169, 1125, 1042. H NMR (400 MHz, DMSO-d6): dH (ppm) 2.53 (d,
J = 4.4 Hz, 6H, 2CH3), 4.22 (t, J = 6.4 Hz, 2H, CH2), 5.95 (brs, 2H, 2NH), 6.44
(brs triplet, J = 6.4 Hz, 2H, NH. 13C NMR (100 MHz, DMSO-d6): dC (ppm) 26.6,
46.2, 159.0. Anal. calc. for C5H12N4O2 (160.17): C, 37.49; H, 7.55; N, 34.98; found:
C, 37.40; H, 7.48; N, 34.90.
1,10-((4-Nitrophenyl)methylene)bis(3-phenylurea) (Table 3, entry 12) White
solid, m.p. 205–207 °C. IR (KBr, cm-1): 3307, 3156, 2925, 2853, 1650, 1597,
1
1522, 1443, 1348, 1229, 1108. H NMR (400 MHz, DMSO-d6): dH (ppm) 6.41 (t,
J = 8.0 Hz, 1H, CH), 6.92 (t, J = 7.2 Hz, 2H, Ar–CH), 7.23 (t, J = 7.6 Hz, 4H,
Ar–CH), 7.35 (d, J = 8.4 Hz, 2H, 2NH), 7.40 (d, J = 7.6 Hz, 4H, Ar–CH), 7.69 (d,
J = 8.4 Hz, 2H, Ar–CH), 8.26 (d, J = 8.8 Hz, 2H, Ar–CH), 8.88 (s, 2H, 2NH). 13
C
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Nanosilica-bonded N-(propylsulfonyl) piperazine-N-…
NMR (100 MHz, DMSO-d6): dC (ppm) 59.1, 118.3, 122.0, 123.9, 127.8, 129.1,
140.4, 147.1, 150.1, 154.7. Anal. calc. for C21H19N5O4 (405.41): C, 62.22; H, 4.72;
N, 17.27; found: C, 62.17; H, 4.65; N, 17.17.
1,10-((4-Cyanophenyl)methylene)bis(3-phenylurea) (Table 3, entry 13) White
solid, m.p. 218–220 °C. IR (KBr, cm-1): 3312, 3037, 2944, 2230, 1651, 1595, 1546,
1443, 1314, 1225, 1106. 1H NMR (400 MHz, DMSO-d6): dH (ppm) 6.36 (t,
J = 8.0 Hz, 1H, CH), 6.92 (t, J = 7.6 Hz, 2H, Ar–CH), 7.23 (t, J = 8.4 Hz, 4H,
Ar–CH), 7.29 (d, J = 8.0 Hz, 2H, 2NH), 7.39 (d, J = 7.6 Hz, 4H, Ar–CH), 7.61 (d,
J = 8.4 Hz, 2H, Ar–CH), 7.86 (d, J = 8.4 Hz, 2H, Ar–CH), 8.84 (s, 2H, 2NH). 13
C
NMR (100 MHz, DMSO-d6): dC (ppm) 59.2, 110.3, 118.2, 119.3, 121.9, 127.5,
129.1, 132.7, 140.4, 148.0, 154.7. Anal. calc. for C22H19N5O2 (385.42): C, 68.56; H,
4.97; N, 18.17; found: C, 68.49; H, 4.91; N, 18.11.
1,10-((4-Chlorophenyl)methylene)bis(3-phenylurea) (Table 3, entry 14) White
solid, m.p. 213–215 °C. IR (KBr, cm-1): 3308, 3154, 2925, 2853, 1650, 1598, 1545,
1444, 1315, 1238, 1094, 1015. 1H NMR (400 MHz, DMSO-d6): dH (ppm)
6.30–6.32 (m, 1H, CH), 6.89–6.93 (m, 3H, Ar–CH), 7.20–7.25 (m, 5H, Ar–CH),
7.37–7.44 (m, 8H, 2NH and Ar–CH), 8.78 (s, 2H, 2NH). 13C NMR (100 MHz,
DMSO-d6): dC (ppm) 59.0, 118.1, 118.2, 121.8, 128.4, 128.6, 129.1, 132.2, 140.5,
154.7. Anal. calc. for C21H19ClN4O2 (394.85): C, 63.88; H, 4.85; N, 14.19; found:
C, 63.80; H, 4.77; N, 14.12.
1,10-((2-Chloro-5-nitrophenyl)methylene)bis(3-phenylurea) (Table 3, entry 15)
White solid, m.p. 230–232 °C. IR (KBr, cm-1): 3384, 3281, 3143, 3104, 1657, 1530,
1
1443, 1347, 1310, 1221, 1113. H NMR (400 MHz, DMSO-d6): dH (ppm) 6.61 (t,
J = 7.6 Hz, 1H, CH), 6.92 (t, J = 7.2 Hz, 2H, Ar–CH), 7.23 (t, J = 7.2 Hz, 4H, Ar–
CH), 7.38 (t, J = 7.6 Hz, 6H, NH and Ar–CH), 7.81 (d, J = 8.8 Hz, 1H, Ar–CH), 8.21
(dd, 8H, J = 2.8, 8.4 Hz, 1H, Ar–CH), 8.52 (d, 8H, J = 2.8 Hz, 1H, Ar–CH), 8.70 (s,
2H, 2NH). 13C NMR (100 MHz, DMSO-d6): dC (ppm) 57.5, 118.3, 122.0, 123.5,
124.6, 129.1, 131.5, 139.3, 140.2, 141.1, 146.6, 154.3. Anal. calc. for C21H18ClN5O4
(439.85): C, 57.34; H, 4.12; N, 15.92; found: C, 57.27; H, 4.05; N, 15.82.
1,10-(Phenylmethylene)bis(3-phenylurea) (Table 3, entry 16) White solid, m.p.
202–204 °C. IR (KBr, cm-1): 3305, 3151, 3034, 2925, 2854, 1641, 1595, 1443, 1314,
1233, 1124, 1029. 1H NMR (400 MHz, DMSO-d6): dH (ppm) 6.33–6.37 (m, 1H, CH),
6.88–6.93 (m, 2H, Ar–CH), 7.12 (d, J = 8.0 Hz, 2H, 2NH), 7.23 (t, J = 8.4 Hz, 4H,
Ar–CH), 7.30 (t, J = 7.2 Hz, 1H, Ar–CH), 7.37–7.46 (m, 8H, 2NH and Ar–CH), 8.69
(s, 2H, 2NH). 13C NMR (100 MHz, DMSO-d6): dC (ppm) 59.3, 118.0, 118.1, 121.8,
126.4, 127.8, 128.7, 129.1, 140.6, 154.6. Anal. calc. for C21H20N4O2 (360.41): C,
69.98; H, 5.59; N, 15.55; found: C, 69.92; H, 5.50; N, 15.47.
1,10-((4-Methoxyphenyl)methylene)bis(3-phenylurea)
(Table 3,
entry 17)
White solid, m.p. 204–205 °C. IR (KBr, cm-1): 3303, 3152, 3034, 2930, 2837,
1648, 1596, 1442, 1311, 1245, 1176, 1104, 1030. H NMR (400 MHz, DMSO-d6):
1
dH (ppm) 3.75 (s, 3H, OCH3), 6.29 (t, J = 8.0 Hz, 1H, CH), 6.88–6.96 (m, 4H, Ar–
CH), 7.03 (d, J = 8.0 Hz, 2H, 2NH), 7.23 (t, J = 7.6 Hz, 4H, Ar–CH), 7.35 (d
123

P. Rezaee, J. Davarpanah
J = 8.4 Hz, 2H, Ar–CH), 7.37–7.41 (m, 4H, Ar–CH), 8.64 (s, 2H, 2NH). 13C NMR
(100 MHz, DMSO-d6): dC (ppm) 55.6, 59.1, 114.0, 118.1, 121.7, 127.6, 129.1,
134.2, 140.6, 154.6, 159.0. Anal. calc. for C22H22N4O3 (390.44): C, 67.68; H, 5.68;
N, 14.35; found: C, 67.60; H, 5.62; N, 14.27.
1,10-Methylenebis(3-phenylurea) (Table 3, entry 18) White solid, m.p.
242–243 °C. IR (KBr, cm-1): 3374, 3319, 3047, 2952, 1648, 1562, 1440, 1392,
1
1304, 1235, 1126. H NMR (400 MHz, DMSO-d6): dH (ppm) 4.44 (t, J = 6.0 Hz,
2H, CH2), 6.83 (t, J = 6.0 Hz, 2H, 2NH), 6.91 (t, J = 7.6 Hz, 2H, Ar–CH), 7.23 (t,
J = 6.4 Hz, 4H, Ar–CH), 7.39 (d, J = 8.6 Hz, 4H, Ar–CH), 8.62 (s, 2H, 2NH). 13
C
NMR (100 MHz, DMSO-d6): dC (ppm) 45.7, 118.1, 121.8, 129.1, 140.5, 155.7.
Anal. calc. for C15H16N4O2 (284.31): C, 63.37; H, 5.67; N, 19.71; found: C, 63.31;
H, 5.59; N, 19.75.
6-Phenyl-1,3,5-triazinane-2,4-dithione (9a) White solid, m.p. 242–244 °C. IR
1
(KBr, cm-1): 3381, 3275, 3172, 2948, 1613, 1460, 1415, 1172, 1083. H NMR
(400 MHz, DMSO-d6): dH (ppm) 5.61 (s, 1H, CH), 7.30–7.47 (m, 5H, Ar–CH),
10.49 (broad, 2H, 2NH), 11.36 (broad, 1H, NH). 13C NMR (100 MHz, DMSO-d6):
dC (ppm) 65.1, 126.2, 129.3, 129.4, 140.0, 173.7. MS (m/z): Calcd. for C9H9N3S2:
223.3 [M?], found 223.3. Anal. calc. for C9H9N3S2 (223.32): C, 48.40; H, 4.06; N,
18.82; found: C, 48.27; H, 3.95; N, 18.63.
6-(4-Chlorophenyl)-1,3,5-triazinane-2,4-dithione (9b) Yellowish solid, m.p.
246–247 °C. IR (KBr, cm-1): 3421, 3159, 3094, 2949, 1582, 1450, 1173, 1093.
1H NMR (400 MHz, DMSO-d6): dH (ppm) 5.65 (s, 1H, CH), 7.32 (d, J = 8.4 Hz,
2H, Ar–CH), 7.54 (d, J = 8.4 Hz, 2H, Ar–CH), 10.48 (broad, 2 H, 2NH), 11.52
(broad, 1H, NH). 13C NMR (100 MHz, DMSO-d6): dC (ppm) 64.4, 128.3, 129.3,
134.0, 138.8, 173.8. MS (m/z): Calcd. for C9H8ClN3S2: 257.7, 259.7 [M, M? 2]?,
found 257.7, 259.9. Anal. calc. for C9H8ClN3S2 (257.76): C, 41.94; H, 3.13; N,
16.30; found: C, 41.74; H, 2.97; N, 16.17.
4-(4,6-Dithioxo-1,3,5-triazinan-2-yl)benzonitrile (9c) Yellowish solid, m.p.
246–247 °C. IR (KBr, cm-1): 3325, 3141, 3066, 2923, 2229, 1575, 1527, 1430,
1173, 1084, 835. 1H NMR (400 MHz, DMSO-d6): dH (ppm) 6.07 (s, 1H, CH), 7.72
(d, J = 8.4 Hz, 2H, Ar–CH), 7.92 (d, J = 8.4 Hz, 2H, Ar–CH), 9.54 (broad, 2H,
2NH), 10.50 (broad, 1H, 1NH). 13C NMR (100 MHz, DMSO-d6): dC (ppm) 65.4,
113.0, 117.9, 127.4, 132.9, 143.9, 174.3. MS (m/z): Calcd. for C10H8N4S2: 248.3
[M?], found 248.3. Anal. calc. for C10H8N4S2 (248.33): C, 48.37; H, 3.25; N, 22.56;
found: C, 48.25; H, 3.08; N, 22.37.
Results and discussion
The catalyst was prepared according to the typical heterogeneous process, as
outlined in Scheme 2, and characterized by thermogravimetric analysis (TGA),
scanning electron microscopy (SEM), IR spectroscopy, elemental analyses, and ion-
exchange pH analysis.
123

Nanosilica-bonded N-(propylsulfonyl) piperazine-N-…
S
OH
OH
OH
O
O
O
S
i
i
O
(MeO)3Si
SH
O
Si
SH
2
2
Toluene, reflux, 18h
1
Nano-silica
1) 30%H2O2/MeOH
2) 10%Wt H2SO4
S
O
i
O
O
O
Si
SO3H
2
3) Deionized water
2
SOCl2
NH
HN
O
O
S
S
O
S
i
i
O
O
O
O
O
O
Si
Si
SO2Cl
Si
N
NH
2
2
Et3N
O
3
5
4
O
O
O
O
S
i
O
1) ClSO3H/ CHCl3/ 4h
2) Washing with MeOH
S
N
NSO3H
2
O
Scheme 2 Preparation of silica-bonded N-(propylsulfonyl) piperazine-N-sulfamic acid nanoparticles
Scanning electron microscopy was used to study the structure of the catalyst.
Comparing the primary particle size with the size of the final nanoparticles, the
SEM morphologies showed that the particles were approximately 38–58 nm in size,
with some degree of aggregation (Fig. 1).
The catalyst showed characteristic IR peaks at around 3200–3500, 2821,
1040–1250, 800, and 580 cm-1 due to O–H of silanols, C–H stretching vibrations,
overlapping of peaks corresponding to Si–O–Si, C–N stretching, symmetric SO2
vibrations, and –SO3H groups, respectively [51] (Fig. 2).
Fig. 1 SEM image of silica-
bonded N-(propylsulfonyl)
piperazine-N-sulfamic acid
nanoparticles
123

P. Rezaee, J. Davarpanah
Fig. 2 IR spectrum of silica-bonded N-(propylsulfonyl) piperazine-N-sulfamic acid nanoparticles
Quantitative determination of the organic functional group covalently anchored
onto the surface in compound 5 was performed by thermogravimetric analysis
(TGA). Typically, a loading of ca. 0.74 mmol/g for surface-bound –SO3H group
was obtained (Fig. 3).
Elemental analysis showed content of 4.48 % S, 6.09 % C, 1.85 % H, and
1.92 % N. On the other hand, when the sulfonated product 5 was placed in aqueous
NaCl solution, the solution pH dropped virtually instantaneously to pH *2.11, as
ion exchange occurred between proton and sodium ions (proton exchange capacity:
0.78 mmol/g of sulfonic acid, 5), in good agreement with the TGA and elemental
analysis results.
Characterization of the catalytic performance of this organocatalyst for rapid and
efficient preparation of 1,10-(arylmethylene) diurea derivatives in good yield was
studied systematically. Initially, the reaction of 4-nitrobenzaldehyde (1 mmol) with
urea (2 mmol) with different amounts of catalysts was carried out in toluene at
reflux temperature. After completion of the reaction as monitored by TLC, followed
by standard workup and purification, corresponding 1,10-(arylmethylene) diurea was
obtained; the results are listed in Table 1.
As is clear from Table 1, reaction in the absence of any catalyst gave very low
product yield after 10 h (Table 1, entry 1). Moderate product yields were obtained
when silica nanoparticles (SiO2 NPs) and sulfamic acid were applied in the reaction
(Table 1, entries 2 and 3). Silica-bonded S-sulfonic acid nanoparticles (SBSSANPs),
silica-bonded N-propylsulfamic acid (SBNPSA), and silica-bonded propylpiperazine
N-sulfamic acid (SBPPSA) gave higher product yields under the same reaction
conditions (Table 1, entries 5–7). When silica-bonded N-(propylsulfonyl) piper-
azine-N-sulfamic acid nanoparticles (SBNPSPSANPs) were used as catalyst, much
higher yield was obtained (Table 1, entries 8–11). The highest yield (94 %) was
achieved with 0.07 g catalyst loading (Table 1, entry 10), but higher amount of the
catalyst decreased the reaction yield (Table 1, entry 11).
123

Nanosilica-bonded N-(propylsulfonyl) piperazine-N-…
100
95
90
85
80
75
70
Fig. 3 TGA curve of silica-
bonded N-(propylsulfonyl)
piperazine-N-sulfamic acid
nanoparticles
0
100 200 300 400 500 600 700 800
Temperature / C
Table 1 One-pot condensation reaction between 4-nitrobenzaldehyde and urea in presence of different
catalysts
Entry
Catalyst
Catalyst loading (g) (mmol of –SO3H)
Time (h)
Yield (%)a
1
None
SiO2 NPsb
–
10
12
5
15
42
48
71
87
77
80
75
85
94
91
2
0.1
3
Sulfamic acid
Silica sulfuric acid NPsc
SBSSANPsd
SBNPSAe
0.01 (0.10 mmol)
0.07 (0.055 mmol)
0.07 (0.084 mmol)
0.25 (0.085 mmol)
0.07 (0.086 mmol)
0.03 (0.023 mmol)
0.05 (0.039 mmol)
0.07 (0.054 mmol)
0.1 (0.078 mmol)
4
3
5
3
6
3
7
SBPPSAf
3
8
SBNPSPSANPs
SBNPSPSANPs
SBNPSPSANPs
SBNPSPSANPs
3
9
3
10
11
a
3
3
Isolated yield
b
c
d
e
f
SiO2 with 12.6 nm average particle size
Compound 2 in Scheme 2
Silica-bonded S-sulfonic acid nanoparticles [51]
Silica-bonded N-propylsulfamic acid [44]
Silica-bonded propylpiperazine N-sulfamic acid [45]
These observations clearly show that the synthesized SBNPSPSANPs are an
efficient catalyst in this reaction. It has been supposed that higher lengths of organic
chain result in a remarkable increase of the active centers of acid sites due to
enhancement of mobility and hydrophobicity effects [55].
This reaction was also tested in various solvents (Table 2). The results indicated
that different solvents affected the efficiency of the reaction. Acetone and ethanol
afforded low yields (Table 2, entries 1, 5). CH2Cl2, CH3CN, and dioxane afforded
123

P. Rezaee, J. Davarpanah
Table 2 Solvent effect on
reaction between
Entry
Solventa
Time (h)
Yield (%)b
4-nitrobenzaldehyde (1 mmol)
and urea (2 mmol) catalyzed by
SBNPSPSANPs (0.07 g)
1
2
3
4
5
6
7
8
Acetone
CH2Cl2
CH3CN
Dioxane
Ethanol
H2O
4
3
3
3
4
5
3
4
15
65
71
63
35
a
Reaction carried out in 10 mL
solvent at reflux
Trace
94
Toluene
Neatc
b
Isolated yield
20
c
Reaction carried out at 100 °C
moderate yields (Table 2, entries 2–4). No product was obtained in H2O (Table 2,
entry 6), whereas excellent product yield was achieved when toluene was used as
solvent (Table 2, entry 7). In addition, when the reaction was carried out under
solvent-free conditions, low product yield was found (Table 2, entry 8). The
reaction did not proceed when low-boiling solvents were used (Table 2,
entries 1–5). This might indicate a significant effect of temperature on the reaction.
However, the best result was achieved when the reaction was carried out under
reflux in toluene.
To study the scope of the reaction, a series of aldehydes and urea derivatives
were reacted in the presence of SBNPSPSANPs in toluene at reflux temperature
(Table 3). In all cases, aromatic aldehydes substituted with either electron-donating
or electron-withdrawing groups underwent the reaction moderately and gave
products in good to excellent yields. The reaction is also compatible with
formaldehyde, N-methylurea, and N-phenylurea, affording the related bisureas in
good yields (Table 3, entries 11, 18).
Our interest in bisurea compounds led us to use thiourea instead of urea. The
reaction of thiourea (2 mmol) with substituted aldehydes (1 mmol) in the presence
of SBNPSPSANPs (0.07 g) in toluene at reflux conditions for 12 h gave good
product yields (Scheme 3).
The structures of compounds 8a–c were assigned based on their elemental
analysis and spectral (FT-IR, 1H and 13C-NMR, and mass) data. The IR spectrum of
8a showed bands at 3381, 3275, 1613, 1460, 1415, 1172, 1083, 1061, 862, 769, and
1
730 cm-1. The absence of IR bands at 3400–3500 cm-1 and H-NMR signals at
d=4–5 ppm corresponding to NH2 group indicated that compound 8a was not
produced, with further nucleophilic attack of the NH2 group on the carbonyl group
to give corresponding products 9a–c. This was further confirmed on the basis of the
13C-NMR spectra of 9a–c, showing a signal at d=173–174 ppm (C=S), as well as
the disappearance of doublet NH peak and triplet CH peak from bisthiourea of 8a–
c and the appearance of a singlet between d=5.61 and 6.07 ppm for the methine
carbon in 9a–c. Furthermore, the mass spectra of 9a–c should show molecular ion
peaks at 240, 275, and 265 corresponding to the molecular weights ofcompounds
9a–c, respectively, but values within m/e 17 less than their molecular weight were
observed for all compounds. Therefore, it seems likely that the intermediates 8a–
c were not isolated and ring closure occurred, giving products 9a–c. Recently, Li
123

Nanosilica-bonded N-(propylsulfonyl) piperazine-N-…
Table 3 Synthesis of symmetrical bisamides using SBNPSPSANPs under optimized conditionsa
Entry
R
R0
Time (h)
Yield (%)b
M.p. (°C)
1
H
4-O2N C6H4
4-Cl C6H4
3-Br C6H4
4-CN C6H4
2-Naphthyl
4-O2N C6H4
4-CN C6H4
4-Cl C6H4
4-CH3 C6H4
2-Cl, 5-O2N C6H3
H
3
94
90
91
92
83
93
93
88
85
93
75
89
87
84
88
78
79
74
188–190
190–192
210–212
221–223
208–210
226–227
242–243
198–201
164–166
219–220
164–165
205–207
218–220
213–215
230–232
202–204
204–205
242–243
2
H
3
3
H
3
4
H
3
5
H
3
6
Me
Me
Me
Me
Me
Me
Ph
Ph
Ph
Ph
Ph
Ph
Ph
2.5
2.5
2.5
3
7
8
9
10
11
12
13
14
15
16
17
18
a
2.5
3
4-O2N C6H4
4-CN C6H4
4-Cl C6H4
2-Cl, 5-O2N C6H3
C6H5
2.5
2.5
2.5
2.5
2.5
3
4-CH3O C6H4
H
3
Optimized conditions: aldehyde (1 mmol), urea derivatives (2 mmol), SBNPSPSANPs (0.07 g),
toluene, reflux
b
Isolated yield
S
R
S
H2N
N
H
N
H
NH2
S
O
8a: C6H5-
8b: 4-Cl-C6H4-
8c: 4CN-C6H4-
SBNPSPSANPs
Toluene, Reflux
H2N
NH2
R
H
H
S
N
S
6
7
-NH3
HN
NH
R
9a: C6H5-(70%)
9b: 4-Cl-C6H4-(73%)
9c: 4CN-C6H4-(74%)
Scheme 3 Reaction between thiourea and substituted aldehydes for synthesis of 1,3,5-triazinane-2,4-
dithiones
et al. [56] synthesized 1,3,5-triazinane-2,4-dithiones via condensation of 1-arylth-
ioureas with aliphatic carboxylic acids using ferric chloride hexahydrate as catalyst.
Elemental analysis and spectral (FT-IR, 1H and 13C-NMR, and mass) data
confirmed formation of compounds 9a–c.
123

P. Rezaee, J. Davarpanah
HO3S-N
HO3S-N
R1
O
O
O
O
N-SO3H
H2N NHR2
OH
H
R2HN
N
H
R1
H
R1
H
H2N
O
- H2O
R2HN
O
R1
O
R2
R2
N
N
N
H
N
H
N-SO3H
H
H
Scheme 4 Plausible mechanism for synthesis of symmetrical bisamides
100
90
80
70
60
50
40
30
20
10
0
Fig. 4 Reusability of
SBNPSPSANPs in reaction of
4-nitrobenzaldehyde with urea
under optimized conditions
1
2
3
4
5
No of Run
Scheme 4 shows a plausible mechanism indicating the role of the catalyst in the
formation of the final product.
The reusability of SBNPSPSANPs was investigated in this system. Under
optimized conditions after completion of the reaction, the mass was cooled and
filtered, then the residue was dissolved in DMF (5 mL) and filtered off to remove
the catalyst. The catalyst was washed with ethanol (20 mL). The recovered catalyst
was dried and reused directly for five subsequent runs in the reaction of
4-nitrobenzaldehyde with urea (Table 3, entry 1). As shown in Fig. 4, the product
yield decreased slightly.
Conclusions
Inorganic–organic hybrid Brønsted solid acid catalyst, nanosilica-bonded N-
(propylsulfonyl) piperazine-N-sulfamic acid, was successfully prepared and then
characterized by IR, TGA, SEM, and elemental analysis. The catalytic activity of
this solid acid composite in synthesis of 1,10-(arylmethylene) diurea and 1,3,5-
123

Nanosilica-bonded N-(propylsulfonyl) piperazine-N-…
triazinane-2,4-dithione derivatives from aldehydes and urea or thiourea derivatives
under simple reaction conditions was probed. The advantages of the reported
method are mild, efficient, and reusable catalyst, inexpensive and easily available
starting materials, high to excellent product yields, short reaction times, lack of
toxicity, and simple workup procedure for synthesis of symmetrical bisamides,
making it a useful and attractive process from the environmental and economical
points of view.
Acknowledgments The authors are grateful for the facilities provided to carry out research in Chemistry
Research Laboratory at Abadan Branch, Islamic Azad University.
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