Zirconium(IV) 4-sulphophenylethyliminobismethylphosphonate as an efficient and reusable catalyst for one-pot synthesis of 3,4-dihydropyrimidones under solvent-free conditions

Article abstract of DOI:10.2478/s11696-011-0091-5

Zirconium(IV) 4-sulphophenylethyliminobismethylphosphonate (ZSBEDP) was prepared and characterised by elemental analysis, IR, TG-DSC, and XRD. ZSBEDP was found to be an efficient catalyst for the Biginelli reaction of aromatic aldehyde, ethyl acetoacetate

Full text of DOI:10.2478/s11696-011-0091-5

Chemical Papers 65 (6) 829–834 (2011)
DOI: 10.2478/s11696-011-0091-5
ORIGINAL PAPER
Zirconium(IV) 4-sulphophenylethyliminobismethylphosphonate
as an efficient and reusable catalyst for one-pot synthesis
of 3,4-dihydropyrimidones under solvent-free conditions
b
c
a
aXin-Bin Yang*, Xiang-Kai Fu, Yu Huang, Ren-Quan Zeng
aDepartment of Chemistry, Rongchang Campus, Southwest University, Chongqing 402460, China
bSchool of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715, China
cPharmacy College, Ningxia Medical University, Yinchuan 750004, China
Received 1 April 2011; Revised 22 July 2011; Accepted 2 August 2011
Zirconium(IV) 4-sulphophenylethyliminobismethylphosphonate (ZSBEDP) was prepared and
characterised by elemental analysis, IR, TG-DSC, and XRD. ZSBEDP was found to be an efficient
catalyst for the Biginelli reaction of aromatic aldehyde, ethyl acetoacetate, and urea or thiourea
under solvent-free conditions so as to give 3,4-dihydropyrimidones in good to excellent yields. The
catalyst can be separated by simple filtration and reused without significant loss of its catalytic
activity.
c
ꢀ 2011 Institute of Chemistry, Slovak Academy of Sciences
Keywords: zirconium, phosphonate, acid catalyst, 3,4-dihydropyrimidones, solvent-free
Introduction
corrosion problems, and environmentally safe disposal
(Reddy et al., 2002, 2005; Peng & Deng, 2001; Ku-
mar & Maurya, 2008; Banik et al., 2007; Joseph et
al., 2006; Quan et al., 2009; Abdollahi-Alibeik & Za-
ghaghi, 2009)
Dihydropyrimidones and their derivatives have
attracted attention due to their pharmacological
properties, being reported to be potent calcium
channel-blockers, antihypertensive agents, and alpha-
1a-antagonists (Kappe, 1993, 2000; Rovnyak et al.,
1995). The biological activities of some isolated al-
kaloids have recently been attributed to the special
structure of dihydropyrimidone moiety (Patil et al.,
1995). In 1893, Biginelli first reported the synthesis
of 3,4-dihydropyrimidones by the one-pot condensa-
tion of aldehyde, β-ketoester, and urea under strongly
acidic conditions. However, the method suffered from
such drawbacks as low yields, long reaction time, and
strong corrosion of equipment. Among various im-
provements, there has been rapid growth in the devel-
opment of solid acid catalysts for the Biginelli reac-
tion due to several advantages such as their handling
requirements, simplicity and versatility of engineer-
ing process, catalyst regeneration, decreasing reactor
Zirconium phosphates and phosphonates are at-
tractive solid acid catalysts with high thermal stabil-
ity, high water tolerance ability, and easy sedimen-
tation (Clearfield & Thakur, 1986; Dines & DiGia-
como, 1981), which may be extensively applied to
many catalytic reactions such as esterification, de-
hydration of alcohols, aza-Diels–Alder reactions, and
Paal–Knorr reactions (Okuhara, 2002; Kamiya et al.,
2004; Patel et al., 2001; Costantino et al., 2009; Curini
et al., 2003). The catalytic activity of these materi-
als is attributed to the Brønsted acidity of OH, or
SO3H groups. To the best of our knowledge, zirco-
nium phosphates and phosphonates have received less
attention as solid acid catalysts for the Biginelli reac-
tion. In this paper, we have prepared zirconium(IV)
4-sulphophenylethyliminobismethylphosphonate (ZS-
*Corresponding author, e-mail: yangxbqq@126.com

830
X.-B. Yang et al./Chemical Papers 65 (6) 829–834 (2011)
O
Ar
O
I
X
O
O
EtO
NH
i
+
+
Ar
H
H2N
NH2
OEt
N
H
X
II
III
IVa–IVk
Fig. 1. Synthesis of 3,4-dihydropyrimidones in the presence of ZSBEDP. Reaction conditions: i) 8 mole % ZSBEDP, 100◦C, 1 h;
for Ar and X, see Table 1.
BEDP) and its catalytic activity was explored in one-
pot synthesis of 3,4-dihydropyrimidones via the Big-
inelli reaction without a solvent (Fig. 1).
Experimental
Phenylethyliminobismethylphosphonate and zirco-
nium(IV)
phenylethyliminobismethylphosphonate
(ZBEDP) were prepared in accordance with the pub-
lished methods (Moedritzer & Irani, 1966; Zou et al.,
2009). All other materials were of analytical grade and
used without further purification.
Fig. 2. IR spectra of ZBEDP (a) and ZSBEDP (b).
Powder X-ray diffraction data were obtained with
X’Pert PRO MPD (PANalytical B.V., the Nether-
lands) with Ni-filtered Cu Kα radiation (λ = 0.15406
nm) at 40 kV and 40 mA, in the angular range
of 3–40◦ (2θ). Thermogravimetric analysis (TG) was
carried out on a SDT Q600 instrument (TA Instru-
ments, USA) under argon, using α-alumina as a ref-
erence compound, in a temperature range of 25–
1000◦C at heating rate of 15◦C min−1. FT-IR spec-
tra were recorded using KBr pellets on a Nicolet
6700 spectrometer (Thermo Scientific, USA). Elemen-
tal analyses were carried out using a Carlo Erba 1106
analyser (Carlo Erba, Italy) (for C, H, N, S) and
a TPS-7000 ICP instrument (Beijing Purkinje Gen-
eral Instrument Co., China). 1H NMR spectra (400
MHz) were obtained with a Bruker-400 spectrome-
ter (Bruker BioSpin, Switzerland) using tetramethyl-
silane (TMS) as internal standard. Mass spectra were
recorded using a Finnigan LCQ mass spectrometer
(Finnigan, USA).
Table 1. Biginelli reaction of various aldehydes catalysed by
ZSBEDP
Compound
Ar
X
Yielda/(%)
IVa
IVb
IVc
IVd
IVe
IVf
IVg
IVh
IVi
IVj
IVk
C6H5
3-NO2C6H5
4-ClC6H5
2-ClC6H5
4-HOC6H5
4-CH3OC6H5
C6H5
4-ClC6H5
2-ClC6H5
4-HOC6H5
4-CH3OC6H5
O
O
O
O
O
O
S
S
S
S
S
87
78
85
81
84
81
82
80
75
93
92
a) Isolated yield; see reaction scheme in Fig. 1.
2.51; S, 5.75 %; found: Zr, 16.41; C, 21.57; H, 3.91; N,
2.44; S, 5.80 %.
Zirconium(IV) 4-sulphophenylethyliminobis-
methylphosphonate (ZSBEDP)
General procedure for the synthesis of 3,4-
Following a procedure analogous to the sulphona-
tion reaction (Yang et al., 2010), ZBEDP (1.32 g)
was added to fuming sulphuric acid (10 mL), heated
to 60◦C and stirred vigorously for 30 min. An ap-
parent gel solution was obtained. The gel solution
was then cooled in an ice bath and water was slowly
added until precipitation occurred. The solid was fil-
tered, washed with 2 M HCl, and dried at 60◦C
for 12 h. For Zr[(O3PCH2)2NCH2CH2C6H4SO3H]
· 4.5H2O (C10H22NO13.5P2SZr, Mr = 557.52) wi/
mass % calculated: Zr, 16.33; C, 21.54; H, 3.94; N,
dihydropyrimidones
A mixture of an aromatic aldehyde (1 mmol), ethyl
acetoacetate (1 mmol), urea or thiourea (1.5 mmol),
and ZSBEDP (47.6 mg, 0.08 mmol) was heated at
100◦C for 1 h. The solid mixture was washed with cold
water to remove the excess of urea or thiourea, and
then filtered. The remaining solid was dissolved in hot
ethanol and filtered to recycle the catalyst. The filtrate
was pre-concentrated and the solid product was re-
crystallised from ethanol.

X.-B. Yang et al./Chemical Papers 65 (6) 829–834 (2011)
831
Fig. 3. TG (curve 1) and DSC (curve 2) diagrams of ZBEDP (a) and ZSBEDP (b).
Results and discussion
The IR spectra of ZBEDP and ZSBEDP are shown
in Fig. 2. The stretching and bending vibration bands
belonging to the O—H bond in water and S—OH
bond in ZSBEDP were observed at 3420 cm−1 and
1646 cm−1, respectively. The characteristic bands at
1227 cm−1 and 1124 cm−1 were assigned to S
O
—
—
stretching vibrations of SO3H group (Clearfield et al.,
1995). The band at 679 cm−1 was attributed to prob-
able vibration of the C—SO3H bond (Zima et al.,
2010). Therefore, it could be assumed that ZBEDP
was sulphonated.
Fig. 4. X-ray powder diffraction patterns of ZBEDP (a) and
ZSBEDP (b).
The data obtained by TG/DSC curves had an im-
portant role in determination of the thermal stability
and approximate composition of ZSBEDP. The TG
curve of ZBEDP showed two-step mass losses at tem-
peratures of up to 1000◦C (Fig. 3a). However, the TG
curve of ZSBEDP shown in Fig. 3b was different from
that of ZBEDP. The first mass loss, starting at 45◦C,
could be assigned to the dehydration of ZSBEDP. Its
proportion (14.69 %) corresponds to 4.5 molecules
of water per formula unit (theoretical mass loss of
14.54 %). The second mass loss was ascribed to the loss
of SO3 or SO2 and decomposition of organic moiety
in the range of 250–600◦C; the endothermic peaks at
about 291◦C and 375◦C clearly confirmed mass losses
of the second step. The third step, above 600◦C, was
primarily due to decomposition of the residual organic
moiety and formation of ZrP2O7. These indicated that
ZSBEDP was thermally stable up to about 250◦C.
The X-ray powder diffraction pattern of ZBEDP
shows the typical features of a layered compound. A
characteristic diffraction peak with the interlayer dis-
tance of 1.54 nm of ZBEDP appeared at 2θ = 5.73◦
(Fig. 4, curve a). However, the XRD pattern of ZS-
BEDP exhibited a broad peak in 2θ range of 3–40◦,
indicating its amorphous nature (Fig. 4, curve a).
To examine the catalytic ability of amorphous
ZSBEDP, we also prepared amorphous Zr(HPO4)2
· H2O (ZrP) and Zr[(O3PCH2)2NCH2COOH]· 2H2O
(ZGDMP), by the method described (Ma & Fu, 2004).
All catalysts were screened in the condensation re-
Table 2. Effect of catalyst and temperature in Biginelli reac-
tion of benzldehyde, ethyl acetoacetate, and urea
Entry
Catalyst
Temperature/◦C
Yielda/%
1
2
3
4
5
6
7
ZrP
100
100
100
20
40
60
20
23
87
0
60
76
84
ZGDMP
ZSBEDP
ZSBEDP
ZSBEDP
ZSBEDP
ZSBEDP
80
a) Isolated yields based on IVa.
action of benzaldehyde, ethyl acetoacetate, and urea,
in the presence of catalyst (8 mole %) at 100◦C for
1 h under solvent-free conditions. Interestingly, we
found that ZSBEDP gave the desired product IVa in
the highest yield. By contrast, ZrP and ZGDMP dis-
played poor catalytic activity (Table 2, entries 1–3).
It could be considered that the SO3H group played
an important role in the catalytic process. Then,
the conditions of the reaction catalysed by ZSBEDP
were optimised and the results are listed in Table 2.
When the temperature of the reaction decreased to
20◦C, no product was obtained (entry 4). The reac-
tion proceeded with the highest yield at 100◦C (en-
try 3).

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X.-B. Yang et al./Chemical Papers 65 (6) 829–834 (2011)
Table 3. Spectral data of prepared compounds
Compound 1H NMR and EIMS data
IVa
IVb
1H NMR (DMSO-d6), δ: 9.19 (s, 1H, NH), 7.74 (s, 1H, NH), 7.34–7.23 (m, 5H, Haryl), 5.14 (d, 1H, J = 3.2 Hz,
CH), 3.95 (q, 2H, J = 7.2 Hz, CH2O), 2.25 (s, 3H, CH3), 1.08 (t, 3H, J = 7.2 Hz, CH3)
MS, m/z (Ir/%): 260 (16) (M+), 231 (67), 183 (100), 155 (25), 137 (20)
1H NMR (DMSO-d6), δ: 9.38 (s, 1H, NH), 8.13 (d, 1H, J = 7.2 Hz, Haryl), 8.07 (s, 1H, Haryl), 7.91 (s, 1H, NH),
7.71–7.64 (m, 2H, Haryl), 5.30 (d, 1H, J = 3.2 Hz, CH), 3.98 (q, 2H, J = 7.2 Hz, CH2O), 2.27 (s, 3H, CH3), 1.08 (t,
3H, J = 7.2 Hz, CH3)
MS, m/z (Ir/%): 305 (10) (M+), 288 (60), 232 (24), 183 (100), 155 (22), 137 (12)
IVc
1H NMR (DMSO-d6), δ: 9.25 (s, 1H, NH), 7.77 (s, 1H, NH), 7.38 (d, 2H, J = 8.4 Hz, Haryl), 7.23 (d, 2H, J = 8.4
Hz, Haryl), 5.13 (d, 1H, J = 3.2 Hz, CH), 3.96 (q, 2H, J = 7.2 Hz, CH2O), 2.25 (s, 3H, CH3 ), 1.08 (t, 3H, J = 7.2
Hz, CH3)
MS, m/z (Ir/%): 294 (10) (M+), 265 (100), 221 (40), 183 (90), 155 (32), 137 (15)
IVd
IVe
1H NMR (DMSO-d6), δ: 9.27 (s, 1H, NH), 7.70 (s, 1H, NH), 7.41–7.27 (m, 4H, Haryl), 5.62 (d, 1H, J = 2.8 Hz,
CH), 3.86 (q, 2H, J = 7.2 Hz, CH2O), 2.30 (s, 3H, CH3), 0.97 (t, 3H, J = 7.2 Hz, CH3)
MS, m/z (Ir/%): 294 (10) (M+), 265 (50), 221 (40), 183 (100), 155 (30), 137 (15)
1H NMR (DMSO-d6), δ: 9.32 (s, 1H, OH), 9.11 (s, 1H, NH), 7.61 (s, 1H, NH), 7.01 (d, 2H, J = 8.0 Hz, Haryl), 6.67
(d, 2H, J = 8.4 Hz, Haryl), 5.03 (d, 1H, J = 3.2 Hz, CH), 3.95 (q, 2H, J = 7.2 Hz, CH2O), 2.23 (s, 3H, CH3), 1.08
(t, 3H, J = 7.2 Hz, CH3)
MS, m/z (Ir/%): 276 (32) (M+), 247 (100), 203 (70), 183 (60), 155 (40), 137 (32)
IVf
1H NMR (DMSO-d6), δ: 9.15 (s, 1H, NH), 7.67 (s, 1H, NH), 7.13 (d, 2H, J = 8.8 Hz, Haryl), 6.86 (d, 2H, J = 8.4
Hz, Haryl), 5.08 (d, 1H, J = 3.2 Hz, CH), 3.95 (q, 2H, J = 7.2 Hz, CH2O), 3.72 (s, 3H, CH3O), 2.24 (s, 3H, CH3),
1.08 (t, 3H, J = 7.2 Hz, CH3)
MS, m/z (Ir/%): 290 (32) (M+), 261 (100), 217 (50), 183 (28), 155 (12), 137 (10)
IVg
IVh
1H NMR (DMSO-d6), δ: 10.34 (s, 1H, NH), 9.66 (s, 1H, NH), 7.37–7.21 (m, 5H, Haryl), 5.14 (d, 1H, J = 3.6 Hz,
CH), 3.98 (q, 2H, J = 7.2 Hz, CH2O), 2.29 (s, 3H, CH3), 1.08 (t, 3H, J = 7.2 Hz, CH3)
MS, m/z (Ir/%): 276 (88) (M+), 247 (55), 199 (100), 171 (25) ), 153 (12)
1H NMR (DMSO-d6), δ: 10.39 (s, 1H, NH), 9.68 (s, 1H, NH), 7.42 (d, 2H, J = 8.4 Hz, Haryl), 7.22 (d, 2H, J = 8.4
Hz, Haryl), 5.16 (d, 1H, J = 3.6 Hz, CH), 3.98 (q, 2H, J = 7.2 Hz, CH2O), 2.29 (s, 3H, CH3), 1.08 (t, 3H, J = 7.2
Hz, CH3)
MS, m/z (Ir/%): 310 (80) (M+), 281 (100), 247 (65), 199 (70), 171 (25), 137 (35)
IVi
IVj
1H NMR (DMSO-d6), δ: 10.37 (s, 1H, NH), 9.61 (s, 1H, NH), 7.43–7.29 (m, 4H, Haryl), 5.64 (d, 1H, J = 3.2 Hz,
CH), 3.89 (q, 2H, J = 7.2 Hz, CH2O), 2.33 (s, 3H, CH3), 0.99 (t, 3H, J = 7.2 Hz, CH3)
MS, m/z (Ir/%): 310 (80) (M+), 281 (60), 237 (38), 199 (100), 171 (22), 153 (10)
1H NMR (DMSO-d6), δ: 10.25 (s, 1H, OH), 9.56 (s, 1H, NH), 9.42 (s, 1H, NH), 6.99 (d, 2H, J = 8.4 Hz, Haryl),
6.70 (d, 2H, J = 8.0 Hz, Haryl), 5.05 (d, 1H, J = 3.2 Hz, CH), 3.97 (q, 2H, J = 7.2 Hz, CH2O), 2.27 (s, 3H, CH3),
1.08 (t, 3H, J = 7.2 Hz, CH3)
MS, m/z (Ir/%): 292 (85) (M+), 263 (100), 219 (60), 199 (35), 171 (12)
IVk
1H NMR (DMSO-d6), δ: 10.29 (s, 1H, NH), 9.60 (s, 1H, NH), 7.11 (d, 2H, J = 8.4 Hz, Haryl), 6.89 (d, 2H, J = 8.4
Hz, Haryl), 5.10 (d, 1H, J = 3.6 Hz, CH), 3.98 (q, 2H, J = 7.2 Hz, CH2O), 3.72 (s, 3H, CH3O), 2.28 (s, 3H, CH3),
1.09 (t, 3H, J = 7.2 Hz, CH3)
MS, m/z (Ir/%): 306 (80) (M+), 277 (100), 233 (70), 199 (40), 171 (10)
The catalyst recovered after washing with ace-
tone followed by drying at 60◦C was used in the
next cycle without any additional ZSBEDP. A min-
imal decrease in activity was observed, as shown in
Fig. 5. The acidity study was performed for fur-
ther insight into the reason for the decrease in ac-
tivity. The pH values of ZSBEDP and ZSBEDP re-
covered after five cycles were monitored under the
same conditions. The pH value of the recovered ZS-
BEDP is higher than that of ZSBEDP. On the basis
of this result, this decrease in activity of the recov-
ered ZSBEDP may be due to the decrease in acid-
ity.
Inspired by the previous results, we expanded the
Biginelli reaction catalysed by ZSBEDP under opti-
mised conditions to other types of aromatic aldehy-
100
90
80
70
60
0
1
2
3
4
5
6
Number of cycles
Fig. 5. Reusability study of ZSBEDP in the condensation reac-
tion of benzaldehyde, ethyl acetoacetate, and urea. All
cycles proceeded under the same reaction conditions.

X.-B. Yang et al./Chemical Papers 65 (6) 829–834 (2011)
833
des. All results are listed in Table 1. Good to excel-
lent yields were obtained for almost all of the alde-
hydes tested. 1H NMR and EIMS data of prepared
compounds are listed in Table 3.
Kamiya, Y., Sakata, S., Yoshinaga, Y., Ohnishi, R., & Okuhara,
T. (2004). Zirconium phosphate with a high surface area as a
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Conclusions
In summary, ZSBEDP was prepared and displayed
good catalytic activity in a one-pot synthesis of di-
hydropyrimidones under solvent-free conditions. Com-
pared with the catalytic effect of amorphous ZrP and
ZGDMP, the SO3H group of ZSBEDP was critical for
enhancement of the catalytic activity. In addition, the
catalyst was reusable without significant loss of its cat-
alytic activity.
Kappe, C. O. (1993). 100 years of the Biginelli dihydropyrim-
idine synthesis. Tetrahedron, 49, 6937–6963. DOI: 10.1016/
S0040-4020(01)87971-0.
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component domino synthesis of 1,4-dihydropyridines under
solvent free conditions. Tetrahedron, 64, 3477–3482. DOI:
10.1016/j.tet.2008.02.022.
Ma, X. B.,
layered amorphous and crystalline zirconium phosphate–
phosphonates
& Fu, X., K. (2004). Synthesis of the novel
Zr(HPO4)[O3PCH2N(CH2CH2)2O]·nH2O,
Zr(HPO4)[O3PCH2N(CH2CO2H)2]·nH2O, zirconium phos-
phonates Zr[(O3PCH2)NCH2CO2H]·nH2O and the catalytic
activities of their palladium complexes in hydrogenation.
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Acknowledgements. This work was financially supported
by the Natural Science Foundation Project CQ CSTC (No.
2009BB5300), the Fundamental Research Funds for the Central
Universities (XDJK2010C004) and the doctoral programme of
Southwest University.
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