Synthesis of 2,3-dihydroquinazolin-4(1H)-ones by three-component coupling of isatoic anhydride, amines, and aldehydes catalyzed by magnetic Fe 3O4 nanoparticles in water

Article abstract of DOI:10.1021/cc100047j

A simple and efficient protocol for one-pot three-component coupling of isatoic anhydride, amines, and aldehydes in water using magnetically recoverable Fe₃O₄ nanoparticles is reported. This methodology results in the synthesis of a variety of 2,3-dihydroquinazolin-4(1H)-ones in high yields. The catalyst can be recovered and recycled without a significant loss in the catalytic activity.

Full text of DOI:10.1021/cc100047j

J. Comb. Chem. 2010, 12, 643–646
643
Synthesis of 2,3-Dihydroquinazolin-4(1H)-ones by Three-Component
Coupling of Isatoic Anhydride, Amines, and Aldehydes Catalyzed by
Magnetic Fe3O4 Nanoparticles in Water
Zhan-Hui Zhang,* Hong-Yan Lu¨, Shu-Hong Yang, and Jian-Wu Gao
The College of Chemistry & Material Science, Hebei Normal UniVersity, Shijiazhuang 050016, China
ReceiVed March 20, 2010
A simple and efficient protocol for one-pot three-component coupling of isatoic anhydride, amines, and
aldehydes in water using magnetically recoverable Fe3O4 nanoparticles is reported. This methodology results
in the synthesis of a variety of 2,3-dihydroquinazolin-4(1H)-ones in high yields. The catalyst can be recovered
and recycled without a significant loss in the catalytic activity.
1. Introduction
and aldehydes. Multicomponent reactions (MCRs) have some
advantages over classic divergent reaction strategies, such as
lower costs, shorter reaction time, and less side products, as
well as environmentally friendlier aspects.12 Until now, only a
few strong acid catalysts such as montmorillonite K-10,13 silica
sulfuric acid,14 zinc(II) perfluorooctanoate [Zn(PFO)2],15
KAl(SO4)2 · 12H2O,16 Al(H2PO4)3,17 gallium(III) triflate,18 mo-
lecular iodine,19 MCM-41-SO3H,20 1-butyl-3-methylimidazo-
lium tetrafluoroborate ([bmim]BF4),21 and Amberlyst-1522 have
been employed to accomplish this three-component reaction.
However, most of those methods are associated with different
drawbacks such as long reaction time, low yields, strongly acidic
conditions, use of expensive reagents, and the requirement of
an additional microwave oven. Therefore, there is still a need
to develop a simple and convenient approach for the preparation
of 2,3-dihydroquinazolinones.
Because of increasing environmental concerns, the develop-
ment of a clean synthetic procedure has become crucial and
demanding research. In this sense, heterogeneous organic
reactions have many advantages, such as ease of handling,
separation, recycling, and environmentally safe disposal.1 Nano-
particles as heterogeneous catalysts have attracted a great deal
attention in recent years because of their interesting structure
and high catalytic activities.2 In this context, magnetic particles,
in particular, have emerged as one the most useful heteroge-
neous catalysts because of their numerous applications in
nanocatalysis, biotechnology, and medicine.3 Additionally, the
magnetic properties make possible the complete recovery of
the catalyst by means of an external magnetic field.4 On the
other hand, performing organic reactions in aqueous media has
several benefits because water would be considerably safe,
abundant, nontoxic, environmentally friendly, and economical
compared to organic solvents. Moreover, water exhibits unique
reactivity and selectivity, which is different from those in
conventional organic solvents.5 Therefore, the development of
a catalyst that is not only stable toward water but also simply
recyclable seems highly desirable.
In continuation of our efforts to develop new synthetic
methods for important organic compounds,23 herein we report
the synthesis of 2,3-dihydroquinazolin-4(1H)-ones via one-
pot three-component condensation of isatoic anhydride,
amines, and aldehydes in the presence of a catalytic amounts
of Fe3O4 nanoparticles24 in water (Scheme 1).
2,3-Dihydroquinazolinones are an important class of bioac-
tive compounds that are prescribed as plant growth regulators,
and as anticancer drugs.6 In addition, these compounds can
easily be oxidized to their quinazolin-4(3H)-one analogues,7
which are themselves important biologically active heterocyclic
compounds,8 and can also be found in some natural products.9
Particularly, the quinazolinone core scaffold has been exten-
sively utilized as a drug-like template in medicinal chemistry.10
In view of their significance, various procedures have been
developed for the construction of 2,3-dihydroquinazolin-4(1H)-
one frameworks.11 Unfortunately, those methods for the as-
sembly of these heterocycles involve muti-step and low-yielding
reaction sequences. A more attractive and atom-efficient strategy
for the preparation of 2,3-dihydroquinazolinones is through a
one-pot, three-component reaction of isatoic anhydride, amines,
2. Results and Discussion
Initially, the three-component reaction of isatoic anhydride,
benzaldehyde, and aniline as a simple model substrate was
investigated to establish the feasibility of the strategy and
optimize the reaction conditions. The catalytic activity of
various nano metal oxides was evaluated for this model
reaction, and the results are summarized in Table 1. From
Table 1, it was clear that these nanosized particles success-
fully promoted this A3-coupling reaction with high yields.
Scheme 1. Fe3O4 Catalyzed Synthesis of 2,3-
Dihydroquinazolin-4(1H)-ones
* To whom correspondence should be addressed. E-mail: zhanhui@
mail.nankai.edu.cn.
10.1021/cc100047j  2010 American Chemical Society
Published on Web 07/23/2010

644 Journal of Combinatorial Chemistry, 2010 Vol. 12, No. 5
Zhang et al.
Table 1. Effect of Different Catalysts on the Reaction of Isatoic
entry 13). The corresponding 2,3-dihydroquinazolin-4(1H)-
one could be obtained when higher catalyst loading was used
(50 mol %), probably because of the higher basicity of
aliphatic amine compared to aniline. Thus, the effective
catalyst loading was found to be 15 mol % for aniline and
50 mol % for aliphatic amine, respectively.
Anhydride, Benzaldehyde, and Anilinea
To explore the scope and limitation of this A3-coupling
reaction, particularly in regard to library construction, we
conducted the reactions of diverse amines and aldehydes under
the optimized conditions. Selected results are summarized in
Table 3. In general, aromatic aldehydes bearing electron-
donating or electron-withdrawing groups with isatoic anhydride
proceed smoothly when aniline was employed in this reaction
except 4-cyanobenzaldehyde gave lower yield (Table 3, entry
12). Subsequently, the substrate scope of amines was examined
for this three-component reaction. Aromatic amines were found
to be effective substrates and afforded the respective 2,3-
dihydroquinazolin-4(H)-one derivatives in high yields. Further,
this three-component reaction also proceeded very smoothly
when aliphatic amines (Table 3, entries 34-41) were used, and
the desired products were obtained in very good yields in the
presence of 50 mol % Fe3O4.
entry
catalyst
none
ZnO
TiO2
yield (%)b
1
2
3
4
5
6
7
8
9
trace
70
68
75
70
73
72
80
38
CuO
Al(OH)3
ZnFe2O4
γ-Fe2O3
Fe3O4
powdered Fe3O4
a Experimental conditions: isatoic anhydride (1 mmol), benzaldehyde
(1 mmol), aniline (1 mmol) and catalyst (0.15 mmol) in 5 mL of H2O
for 2 h under reflux. b Isolated yields.
Table 2. Investigation of the Amounts of Catalyst and Solvent
Effects on the Reaction of Isatoic Anhydride, Benzaldehyde, and
Anilinea
entry
catalyst loading (mol %)
solvent
time (h)
yield (%)b
The reusability is one of the important properties of this
catalyst. After the reaction was complete, ethyl acetate was
added, and the catalyst was absorbed onto the magnetic
stirring bar. The catalyst was then washed with ethyl acetate,
air-dried, and used directly with fresh substrates under
identical conditions without further purification. It was shown
that the catalyst could be used for five runs without noticeable
drop in the product yield and its catalytic activity (Table 4).
A transmission electron microscopy (TEM) image of Fe3O4
showed that the average size and distribution of the Fe3O4
were not significantly altered, in good agreement with
previously reported results3m,n that proved the unusual
properties and potential applications of this magnetic material.
To elucidate the reaction mechanism, 2-amino-N-phenyl-
benzamide was prepared from the reaction of isatoic
anhydride with aniline under same condition. Next, 2-amino-
N-phenylbenzamide reacted with benzaldehyde to give the
corresponding product 4a in the presence of Fe3O4. In
addition, the reactions of isatoic anhydride with benzaldehyde
and benzaldehyde with aniline did not proceed under same
conditions. On the basis of the above results and by referring
to the literature,15,17 we propose a plausible mechanism for
the formation of 2,3-dihydroquinazolin-4(1H)-ones (Scheme
2). First, the isatoic anhydride is activated by Fe3O4 followed
by the N-nucleophilic amine attacks on the carbonyl to form
intermediate I. Then decarboxylation occurs resulting in
generation of 2-amino-N-substitued-benzamide (II). Iron
cations act as Lewis acid and play a significant role in
increasing the electrophilic character of the aldehydes.
Subsequently, the reaction of activated aldehyde with II
proceeds to afford intermediate III that is converted to
product 4 via an intramolecular cyclization.
1
2
3
4
5
6
7
8
15
15
15
15
15
1
MeCN
CH2Cl2
EtOH
THF
EtOAc
H2O
H2O
H2O
H2O
H2O
2
2
2
2
2
2
2
2
3
2
3
2
2
1.5
20
5
78
10
25
50
57
70
72
80
81
80
80d
84
5
10
10
15
15
20
15
50
9
10
11
12
13c
14c
H2O
H2O
H2O
H2O
a Experimental conditions: isatoic anhydride (1 mmol), benzaldehyde
(1 mmol), aniline (1 mmol), and Fe3O4 in 5 mL of solvent under reflux.
b Isolated yields. c Methylamine was used instead of aniline. d Yield of
2-amino-N-methylbenzamide.
Among the catalysts evaluated, nano Fe3O4 was superior to
others and produced the best yield of the target 2,3-diphenyl-
2,3-dihydro-1H-quinazolin-4-one (4a). However, powdered
Fe3O4 displayed low activity (Table 1, entry 9). Only a trace
amount of the product was formed in the absence of catalyst
(Table 1, entry 1).
We next made a study on the effect of solvents and the
catalyst loading in model reaction. In general, nonpolar
solvents such as dichloromethane and ethyl acetate led to
low yields. The best conversion was observed when the
reaction was performed in water. Moreover, we found that
the yields were obviously affected by the amount of Fe3O4
loaded. It was found that 15 mol % of Fe3O4 was sufficient
enough to afford 4a with 80% isolated yield (Table 2, entry
10). The yield remained unaffected when the catalyst loading
was increased to 20 mol % (Table 2, entry 12). However,
the yield was decreased when the catalyst loading was
reduced to 10 mol % (Table 2, entry 8). Prolonging the
reaction time did not enhance the yield (Table 2, entry 9).
Unexpectedly, only 2-amino-N-substituted-benzamide was
obtained when aliphatic amine such as methylamine was
employed in the presence of 15 mol % of Fe3O4 (Table 2,
In conclusion, we have developed an efficient one-pot
procedure for the synthesis structurally diverse libraries of
2,3-dihydroquinazolin-4(1H)-ones by a three-component
condensation of isatoic anhydride, amines, and aldehydes in
water in the presence of Fe3O4. The procedure is applicable

Synthesis of 2,3-Dihydroquinazolin-4(1H)-ones
Journal of Combinatorial Chemistry, 2010 Vol. 12, No. 5 645
Table 3. Synthesis of 2,3-Dihydroquinazolin-4(1H)-ones in the Presence of Fe3O4
Mp (°C)
entry
R
R1
product
time (h)
yield (%)a
found
reported
1
2
3
4
5
6
7
8
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
4a
2
5
5
5
5
5
5
5
5
5
5
5
6
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
2
2
2
1.5
1.5
2
2
3
80
84
85
80
75
87
86
73
74
80
78
51
76
80
83
78
82
85
76
85
72
70
73
69
70
73
68
85
87
86
87
88
80
82
85
86
84
85
85
88
83
205-206
205-207
215-216
203-204
170-173
244-246
177-179
194-196
188-190
223-225
194-196
203-205
175-176
197-198
247-248
191-192
213-214
196-198
215-216
217-219
228-229
186-188
247-249
241-243
196-198
244-246
229-230
212-213
252-254
190-192
193-195
244-246
229-231
220-221
234-135
180-182
161-162
146-147
135-137
125-126
133-135
203-20515
194-19615
21425
3-Me-C6H4
4-Me-C6H4
4-MeO-C6H4
2,3-(MeO)2-C6H3
3,4-(MeO)2-C6H3
2,3,4-(MeO)3-C6H2
3,4,5-(MeO)3-C6H2
3-Br-C6H4
4-Br-C6H4
4-NO2-C6H4
4-CN-C6H4
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
4b
4c
4d
204-20515
4e
4f
4g
4h
9
4i
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34b
35b
36b
37b
38b
39b
40b
41b
4j
222-22515
195-19615
4k
4l
2-MeC6H4
4-MeC6H4
4-Me3CC6H4
2-OMeC6H4
4-OMeC6H4
4-OEtC6H4
2-ClC6H4
4-ClC6H4
4-BrC6H4
4-NO2C6H4
4-MeC6H4
4-MeC6H4
4-Me3CC6H4
4-Me3CC6H4
4-Me3CC6H4
4-OMeC6H4
4-OMeC6H4
4-OMeC6H4
4-OEtC6H4
4-OEtC6H4
4-ClC6H4
H
4m
4o
173-17526
196-19815
4p
4q
19027
4r
215-21617
4s
4t
215-21728
216-21815
224-22615
185-18715
4u
4v
Ph
4w
4x
4-MeO-C6H4
4-F-C6H4
4-MeO-C6H4
4-F-C6H4
4-Br-C6H4
3-Me-C6H4
3,4-(MeO)2-C6H3
2,3,4-(MeO)3-C6H2
2,3,4-(MeO)3-C6H2
4-Br-C6H4
3,4-Me2-C6H3
Ph
4-Me-C6H4
4-MeO-C6H4
Ph
4-MeO-C6H4
Ph
4y
4z
4aa
4ab
4ac
4ad
4ae
4af
4ag
4ah
4ai
4aj
4ak
4al
4am
4an
4ao
4ap
219-22214b
233-23414b
180-18114b
160-16314b
145-14614b
134-13714b
124-12614b
132-13514b
H
H
Me
Me
Et
Et
Et
4-MeO-C6H4
4-Cl-C6H4
a Isolated yield. b 50 mol % Fe3O4 was used.
Table 4. Recovery and Reuse of Fe3O4 Nanoparticles for the
Synthesis of 4a
were mixed in H2O (5 mL). The mixture was stirred under
reflux in an air atmosphere for an appropriate time
indicated in Table 3. Then ethyl acetate (5 mL) was added.
The Fe3O4 nanoparticles were absorbed on to the magnetic
stirring bar. The organic and aqueous layers were sepa-
rated. The organic phase was dried over MgSO4, and the
solvent was evaporated under vacuum. The residue
was purified by short column chromatography on silica
gel.
cycle
1
2
3
4
5
yield (%)
80
78
76
76
75
Scheme 2. Proposed Mechanism for the Synthesis of
2,3-Dihydroquinazolin-4(1H)-ones
Acknowledgment. We thank the National Natural Science
Foundation of China (20872025), the Nature Science Foun-
dation of Hebei Province (B2008000149), and the Science
Foundation of Hebei Normal University (L20061314) for
financial support.
Note Added after ASAP Publication. There were errors
in Table 3 in the version of this paper published ASAP July
23, 2010. The correct version published on August 4,
2010.
to a wide range of aromatic aldehydes and amines, and the
products are obtained in high yields. The catalyst can be
readily recovered by magnetic separation and reused.
General Procedure for Synthesis of 2,3-Dihydroquinazo-
lin-4(1H)-ones (4). Isatoic anhydride (1 mmol), amine (1
mmol), aldehyde (1 mmol), and Fe3O4 (0.15 or 0.50 mmol)
Supporting Information Available. Experimental pro-
cedure, characterization data for compound 4 and catalyst.
This material is available free of charge via the Internet at
http://pubs.acs.org.

646 Journal of Combinatorial Chemistry, 2010 Vol. 12, No. 5
Zhang et al.
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