Powdered diethylaminoethyl cellulose as biomass-derived support for phosphotungstic acid: New solid acidic catalyst for the synthesis of 2,3-dihydroquinazolin-4(1H)-ones

Article abstract of DOI:10.1007/s00706-015-1475-y

Finely powdered diethylaminoethyl cellulose is prepared through a bottom-up synthetic method using NaOH/urea aqueous solution as solvent. Phosphotungstic acid anchored on the powdered diethylaminoethyl cellulose can be used as a biopolymer-supported solid acidic catalyst for the synthesis of 2,3-dihydroquinazolin-4(1H)-ones from isatoic anhydride, amines, and aldehydes. The catalyst could be easily recovered by simple filtration and reused several times with minor decreases in the reaction yields.

Full text of DOI:10.1007/s00706-015-1475-y

Monatsh Chem
DOI 10.1007/s00706-015-1475-y
ORIGINAL PAPER
Powdered diethylaminoethyl cellulose as biomass-derived support
for phosphotungstic acid: new solid acidic catalyst
for the synthesis of 2,3-dihydroquinazolin-4(1H)-ones
Shaokang Li1 Qianqian Zhang1 Yanqing Peng1
•
•
Received: 9 December 2014 / Accepted: 6 April 2015
Ó Springer-Verlag Wien 2015
Abstract Finely powdered diethylaminoethyl cellulose is
prepared through a bottom–up synthetic method using
NaOH/urea aqueous solution as solvent. Phosphotungstic
acid anchored on the powdered diethylaminoethyl cellulose
can be used as a biopolymer-supported solid acidic catalyst
for the synthesis of 2,3-dihydroquinazolin-4(1H)-ones from
isatoic anhydride, amines, and aldehydes. The catalyst
could be easily recovered by simple filtration and reused
several times with minor decreases in the reaction yields.
Graphical abstract
Introduction
Nowadays, nearly all polymeric materials still depend on
petroleum-derived monomers. Within both the scientific
and industrial communities, one of the main challenges in
polymer manufacture is the replacement of fossil resources
as raw material by renewable resources such as biomass [1,
2]. Cellulose is the most extensively distributed renewable,
biodegradable, nontoxic, non-edible, and low cost natural
polymer, an almost inexhaustible raw material which has
been exploited for thousands of years in the manufacture of
a wide spectrum of products and materials in daily life [3].
Utilization of cellulose as new source for polymer industry
is certainly benefited for environmental protection and
sustainable development [4].
The use of functionalized cellulose as biomass-derived
polymeric supports provides new opportunities for the
design of more eco-friendly catalysts serve in greener
catalysis. For example, carboxymethyl cellulose has been
used as a functional support for cinchonine which acted as
a recyclable catalyst for asymmetric Michael reaction [5].
Shaabani group reported the synthesis and characterization
of ethylenediamine-functionalized cellulose as a novel bio-
support for palladium nanoparticles, which was found to be
a highly efficient heterogeneous catalyst for the Heck and
Sonogashira couplings in aqueous media [6].
Keywords Biopolymer Á Diethylaminoethyl cellulose Á
Phosphotungstic acid Á Catalysis Á Cyclization
Diethylaminoethyl cellulose (DEAEC) is a kind of
functionalized cellulose routinely used in ion exchange
chromatography. As a kind of anion exchange fiber,
DEAEC is widely used in the separation and purification of
polysaccharides, peptides, nucleotides, and viruses [7–9],
etc. However, its application as a support for the catalytic
applications has not been explored.
Electronic supplementary material The online version of this
article (doi:10.1007/s00706-015-1475-y) contains supplementary
material, which is available to authorized users.
& Yanqing Peng
yqpeng@ecust.edu.cn
1
Shanghai Key Laboratory of Chemical Biology, School of
Pharmacy, East China University of Science and Technology,
Shanghai 200237, People’s Republic of China
Theoretically, DEAEC can be applied as a support for
polyprotic acids due to its basic nature. In the design of
123

S. Li et al.
heterogeneous supported catalysts, powdered supports
were recognized to be superior to their bulk counterparts
(e.g., fibrous ones) [10, 11]. Unfortunately, finely pow-
dered DEAEC is commercially unavailable. Moreover, no
literature was found in the preparation of powdered
DEAEC from commercially available fibrous products.
Powdered cellulose could be obtained from two routes:
top–down process and bottom–up process. Top–down
process routinely needs the aid of mechanical force. Me-
chanical treatment of cellulose is a simple and cheap
method [12, 13], but the micronization efficiency is
relatively low. Therefore, we decided to develop a bottom–
up process (namely dissolution–regeneration method) to
prepare powdered DEAEC.
Scheme 1
Cellulose is difficult to dissolve in conventional solvents
because of the strong hydrogen bonding and partially
crystalline structure. Only a few solvents are suitable for
cellulose dissolution. The most important solvents NaOH-
CS2 (viscose process) and N-methylmorpholine N-oxide
monohydrate (Lyocell process) have serious drawbacks
such as hazardous byproducts. Some binary mixtures (e.g.,
LiCl/DMA) and ionic liquids could directly dissolve cel-
lulose [14, 15], but they always meet inevitable problems
such as environmental impact, high costs, and difficulty in
solvent recovery [16, 17]. Compared with above-men-
tioned solvent system, NaOH/urea aqueous solution is a
kind of more economical and environmental-friendly sol-
vent for rapid cellulose dissolution accompanied with
essentially nontoxic byproducts [18–22]. In continuation of
our research on catalysts from biorenewable resources [23],
we explored a bottom–up synthetic method to obtain finely
powdered DEAEC using NaOH/urea aqueous solution as
cellulose solvent.
synthesis of desired products in good to excellent yields. In
addition, the catalyst can be easily recovered by simple
filtration and reused at least 5 times without significant loss
of its catalytic activity.
Results and discussion
In our investigation, NaOH/urea aqueous solution was
chosen due to its inexpensive and green features. Our
method involves the dissolution of DEAEC in NaOH/urea
aqueous solution followed by treating in an acidic co-
agulation bath under vigorous stirring. It was found that the
agitation intensity appears to be of a particular importance
for the formation of powdered product in regeneration step.
In the cases under less vigorous stirring, fibrous products
were regenerated rather than powdered ones. Moreover, the
use of inner baffles is also in favor of the formation of
powdered products. When the viscous solution of DEAEC
was dropped into a stirred acidic coagulation bath under
laminar flow condition, it tends to afford fibrous products
due to the regular streamline. The inner baffles block the
liquid flow, changing laminar flow into turbulent flow by
which the streamline was disorganized, while the mass
transfer was improved remarkably.
In the family of heterocyclic compounds, 2,3-dihydro-
quinazolin-4(1H)-ones have attracted much attention as
they exhibit wide range of pharmacological and biological
activities [24–26]. The most convenient route to 2,3-dihy-
droquinazolin-4(1H)-ones includes condensation of isatoic
anhydride, aldehydes, and primary amines in the presence
of appropriate catalyst. A number of catalysts have been
reported including amberlyst-15 [27], silica sulfuric acid
[28], p-TSA [29], acetic acid [30], Ga(OTf)3 [31],
KAl(SO4)2 [32], etc. However, some of these catalysts are
associated with certain drawbacks such as poor recover-
ability and biodegrability, toxicity, and corrosivity.
With powdered DEAEC in hand, we readily prepared a
novel solid supported Brønsted acid through the acid–base
interaction between DEAEC and phosphotungstic acid
(PTA). This material (PTA supported on DEAEC,
PTA@DEAEC) was found to be an efficient catalyst for
the synthesis of 2,3-dihydroquinazolin-4(1H)-ones
(Scheme 1). Results show that the green and recyclable
catalyst possessed excellent catalytic performance in the
The morphologies of DEAEC before and after dissolu-
tion–regeneration process were observed by FE-SEM (field
emission scanning electron microscopy). From the images
(Fig. 1a, b), it can be found that unprocessed DEAEC
keeps the original morphology of fibrous raw feedstock.
Large-scale and enlarged FE-SEM images of regenerated
DEAEC powder reveal that the morphology of as-prepared
powder was granular as well as the particles have an
123

Powdered diethylaminoethyl cellulose as biomass-derived support…
Fig. 1 Large-scale and enlarged FE-SEM images: morphology of unprocessed DEAEC (a, b) and regenerated DEAEC powder (c, d)
average diameter of 5 lm (Fig. 1c, d). It clearly demon-
strates the effect in particle size reduction (micronization)
by the present method.
The regenerated DEAEC powder was then treated with
PTA to afford PTA@DEAEC, which was characterized
with FT-IR, energy-dispersive X-ray spectroscopy
(EDXS), inductively coupled plasma atomic emission
spectrometry (ICP-AES), and acid–base titration. The
chemical structures and functionalities of DEAEC, pow-
dered DEAEC, and PTA@DEAEC were characterized by
FT-IR spectra. In the FT-IR spectra of DEAEC and pow-
dered DEAEC (Fig. 2a, b), the absorbance at
3100–3500 cm-1 is assigned the O–H stretching vibration,
broad band at 2910 cm-1 is assigned to aliphatic C-H
stretching vibration, broad band at around 1380 cm-1 is
assigned to aliphatic C-N stretching vibration, and the
absorption at 1115 cm-1 originates from C–O–C con-
tributes to glycosidic linkages. The characteristic peak
centered at around 1635 cm-1 is attributed to uronic acid
as a consequence of mild degradation [33]. The parent PTA
Keggin structure shows characteristic P-Oa of tetrahedral
Fig. 2 FT-IR spectra of three materials: a untreated DEAEC,
b regenerated DEAEC powder, c PTA@DEAEC
3-
properties, while PW12O40 Keggin units has grafted on
PO4 stretching at 1081 cm-1
, W=Od stretching at
the matrix of DEAEC.
988 cm-1, stretching of W-Oc-W inter bridges between
corner-sharing WO6 octahedra at 895 cm-1, stretching of
W-Ob-W intrabridges between edge-sharing WO6 octahe-
dra at 812 cm-1, and P-O bending about 596 cm-1 [34],
hence these peaks indicated the existence of Keggin
heteropolyacid (Fig. 2c). These results clearly show that
the regenerated DEAEC powder still keeps the intrinsical
The loading of PTA on DEAEC was further confirmed
by EDXS analysis (Fig. 3). The characteristic peaks of
tungsten and phosphorus were observed from EDXS
spectra of PTA@DEAEC. ICP-AES analysis was carried
out to determine the loading capacity of PTA supported on
DEAEC. The content of tungsten was calculated as
1.59 mmol g-1. The number of H? sites of PTA@DEAEC
123

S. Li et al.
recoverability and reusability. Blank experiment was carried
out in the presence of support DEAEC and gave negative
result in the test (Table 1 entry 10).
Next, we applied the optimal protocol to a range of
primary amines (or ammonium carbonate as ammonia
source) and aldehydes to explore the scope of this reaction
for preparation of various 2,3-dihydroquinazolin-4(1H)-
one derivatives. As shown in Table 2, the three-component
reactions worked well using aldehydes and amines with
either electron-withdrawing or electron-donating groups,
while the desired compounds were obtained in satisfactory
to excellent yields. The experimental results showed the
electronic effects of phenyl ring substituents had only a
slight influence on the yields. It could be found that the
reaction is sensitive to steric hindrance. Isolated yields of
ortho-substituted and meta-substituted aldehydes or aro-
matic amines were always little lower than non-substituted
or para-substituted, especially for aldehydes (Table 2 en-
tries c and q).
Fig. 3 EDXS pattern of PTA@DEAEC
Table 1 Optimization of the reaction condition
To check the reusability of the catalyst, after initial
experimentation PTA@DEAEC was collected by filtration,
washed with hot ethanol and subjected to a second run by
charging with the same substrates (Table 3). The results of
this experiment and four subsequent experiments were al-
most consistent in yields (75, 76, 78, 75, 74 %). Although
slightly more time was required to complete the reaction in
the fifth run, the yields are comparable to those seen earlier.
In conclusion, we have developed a dissolution–regen-
eration method for the preparation of powdered DEAEC
from commercially available fibrous feedstock. A novel
solid Brønsted acid was obtained through the acid–base
interaction between DEAEC and PTA, which could be
employed as an efficient catalyst for the synthesis of 2,3-
dihydroquinazolin-4(1H)-ones. This celluloses-derived re-
cyclable catalyst possessed excellent catalytic performance
to afford desired products in satisfactory to excellent
yields. In addition, the catalyst can be easily recovered by
simple filtration and reused at least 5 times without sig-
nificant loss of its catalytic activity.
Entry
Catalyst (mol % of H?)
Temp/°C
Yield/%a
1
2
3
4
5
6
7
8
9
10
a
–
Reflux
Reflux
Reflux
Reflux
Reflux
Reflux
50
0
PTA@DEAEC (1)
PTA@DEAEC (3)
PTA@DEAEC (5)
PTA@DEAEC (8)
PTA@DEAEC (10)
PTA@DEAEC (8)
PTA@DEAEC (8)
PTA (8)
25
42
66
79
75
35
–
25
Reflux
Reflux
82b
DEAEC
–
Isolated yields. Reaction time: 6 h
b
Reaction time: 1.5 h
was also determined to be 0.94 mmol g-1 by acid–base
titration. This result also matched the value estimated
based on tungsten elemental analysis.
The catalytic activity of PTA@DEAEC was demon-
strated by the synthesis of 2,3-dihydroquinazolin-4(1H)-
ones from isatoic anhydride, aldehydes, and primary amines
(or ammonium carbonate). To optimize the reaction condi-
tion, initially, the reaction of isatoic anhydride (1.0 mmol),
benzaldehyde (1.0 mmol), and aniline (1.2 mmol) in 5 cm3
of ethanol was chosen as a model. The effects of catalyst
amount (molar ratio) and temperature were investigated. The
results of this study are summarized in Table 1. It can be seen
that the best result was determined by using 8 mol % (H?) of
the catalyst in reflux ethanol (Table 1 entry 5). The model
reaction using PTA as a homogeneous catalyst was also
conducted (Table 1 entry 9). Homogeneous PTA shown
higher catalytic activity then supported PTA, however,
PTA@DEAEC is superior to PTA due to its satisfactory
Experimental
All chemicals were purchased from commercial suppliers
(Aldrich or Shanghai Chemical Company, China) and used
without further purification. Phosphotungstic acid (99 %)
was purchased from Shanghai Han Si Chemical Co. Ltd
(Shanghai, China). Diethylaminoethyl cellulose (CAS:
9013-34-7; FCP, nitrogen content 14 mg/g) was purchased
from Sinopharm Chemical Reagent Co., Ltd. (Shanghai,
China) and dried under vacuum at 80 °C for 12 h. Isatoic
anhydride (97 %) was supplied by Sinopharm Chemical
Reagent Co., Ltd. (Shanghai, China). Melting points were
123

Powdered diethylaminoethyl cellulose as biomass-derived support…
Table 2 Synthesis of 2,3-dihydroquinazolin-4(1H)-one derivatives under optimized conditions
Entry
Ar
R
Time/h
Yield/%
M.p./°C
Lit. m.p./°C
4a
4b
4c
4d
4e
4f
C6H5
C6H5
6
6
7
7
7
7
7
7
7
7
7
7
5
5
5
5
6
79
78
60
73
87
85
76
69
71
73
83
91
87
81
89
85
30
204–206
210–213
174–176
218–220
256–258
201–203
255–258
201–203
248–250
242–245
189–191
257–260
157–160
218–221
177–180
202–203
174–176
209–211 [28]
214–217 [28]
175–176 [35]
215–216 [35]
250 [36]
C6H5
4-ClC6H4
2-CH3C6H4
C6H5
C6H5
4-CH3C6H4
4-ClC6H4
4-NO2C6H4
4-ClC6H4
C6H5
4-ClC6H4
C6H5
194–196 [35]
250–252 [37]
197–198 [35]
243–247 [38]
241–243 [35]
186–188 [39]
259–260 [39]
150–151 [39]
219–222 [40]
179–180 [40]
203–205 [40]
–
4g
4h
4i
4-CH3C6H4
4-CH3C6H4
4-CH3C6H4
4-CH3C6H4
4-NO2C6H4
4-FC6H4
n-C4H7
4-CH3C6H4
4-FC6H4
4j
4k
4l
C6H5
4-CH3OC6H4
4-ClC6H4
C6H5
4m
4n
4o
4p
4q
H
4-CH3OC6H4
4-ClC6H4
4-CH3-1,2,3-thiadizolyl
H
H
4-CH3C6H4
General conditions: isatoic anhydride (1.0 mmol), benzaldehyde (1.0 mmol), primary amines (1.2 mmol) or (NH4)2CO3 (0.7 mmol), PTA@-
DEAEC (0.085 g), 5.0 cm3 ethanol, reflux, monitored by TLC (ethyl acetate: petroleum ether, 1:2, v/v)
cooled to below -12 °C for 3 h, 3.5 g DEAEC was then
Table 3 Reusability of PTA@DEAEC in model reaction
added at ambient temperature under vigorous stirring. The
Run
Time/h
Yield/%
solids completely dissolved within 30 min to afford a
transparent cellulose dope. The spinning dope was spun
into a coagulation bath composed of 8 wt% H2SO4/10 wt%
Na2SO4 aqueous solution at about 10 °C under vigorous
stirring (3000 rpm). The suspension was subjected to
centrifugation (4000 rpm, 20 min), while resulted powder
was washed with water (30 cm3 9 6) and dried at 80 °C
for 2 h.
1
2
3
4
5
6
6
6
6
7
75
76
78
75
74
Reaction conditions: isatoic anhydride (1.0 mmol), benzaldehyde
(1.0 mmol), 4-chlorobenzaldehyde (1.2 mmol), PTA@DEAEC
(0.085 g), 5.0 cm3 ethanol, reflux
Preparation of powdered PTA@DEAEC
recorded on a Bu¨chi B-540 apparatus. FT-IR spectra of
composite were taken on a Thermo Nicolet 6700 FT-IR
spectrophotometer using KBr pellets. NMR spectra were
measured on a Bruker AC 400 instrument in CDCl3 using
TMS as an internal standard. Mass spectra were recorded
on a Shimadzu QP 1100 EX mass spectrometer with 70 eV
ionization potential. The morphology of the composite was
observed using a JSM-6360LV scanning electron micro-
scope. The loading of phosphotungstic acid was
determined on an Agilent 725ES inductively coupled
plasma atomic emission spectrophotometer and a JSM-
6360LV energy-dispersive X-ray spectrophotometer.
In 25 cm3 round-bottom flask with inner baffles, a mixture
of 2.00 g DEAEC powder, 5.9 g PTA (2 mmol), and
15 cm3 absolute methanol was magnetically stirred for 6 h
at room temperature. The supported catalyst was collected
by filtration, washed with hot methanol (10 cm3 9 6), and
dried at 100 °C for 2 h.
General experimental procedure for the synthesis
of 2,3-dihydroquinazolin-4(1H)-one derivatives
in the presence of PTA@ DEAEC
To a 25 cm3 round-bottom flask charged with isatoic an-
hydride (1.0 mmol), aldehyde (1.0 mmol), primary amine
(1.2 mmol) or (NH4)2CO3 (0.7 mmol), and 5 cm3 ethanol
was added catalytic amount of PTA@DEAEC (0.085 g
equal to 0.080 mmol of H?). The mixture was refluxed for
Preparation of powdered DEAEC
In a typical procedure, 100 g aqueous solution containing
NaOH/urea/H2O of a 7:12:81 by weight ratio was pre-
123

S. Li et al.
12. Prusov AN, Zheleznov KN, Alekseeva OV, Padokhin VA,
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appropriate time as listed in Table 1 (monitored by TLC,
ethyl acetate: petroleum ether = 1:2, v/v). After comple-
tion of the reaction, the solid catalyst was separated by
filtration and washed with hot ethanol (3 cm3 9 2). The
combined ethanol solution was added 2 cm3 of water and
the precipitate was collected by filtration. The crude pro-
duct could be purified by further recrystallization from
ethanol.
´
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2-(4-Methyl-1,2,3-thiadiazol-5-yl)-3-(4-methylphenyl)-
2,3-dihydroquinazolin-4(1H)-one (4q, C18H16N4OS)
Light yellow solid; m.p.: 174–176 °C; Rf = 0.33 (ethyl
acetate/petroleum ether 1:2, v/v); 1H NMR (400 MHz,
CDCl3): d = 7.85 (d, J = 4.0 Hz, 1H, Ar–H), 7.25-7.29
(m, 1H, Ar–H), 7.01–7.03 (d, J = 8.0 Hz, 2H, Ar–H),
6.85–6.89 (m, 3H, Ar–H), 6.50 (d, J = 8.0 Hz, 1H, Ar–H),
6.22 (s, 1H, CH), 4.85 (s, 1H, NH), 2.22 (s, 3H, CH3), 2.14
(s, 3H, CH3) ppm; 13C NMR (100 MHz, CDCl3):
d = 161.89, 156.42, 149.07, 144.30, 138.02, 136.77,
134.55, 130.20, 129.08, 126.94, 120.92, 116.57, 116.04,
67.94, 21.08, 12.24 ppm; MS (EI, 70 eV): m/z
(%) = 336.1 (M?, 10), 275.1 (18), 237.1 (100), 221.1
(12), 207.1 (15), 170.1 (17), 130 (13), 120.0 (34), 91.1 (21),
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