Three-component one-pot synthesis of 2,3-dihydroquinazolin-4(1H)-one derivatives in 2,2,2-trifluoroethanol

Article abstract of DOI:10.1016/j.crci.2012.05.019

Trifluoroethanol (TFE) is found to be an efficient and recyclable medium in promoting one-pot, three-component coupling reactions of isatoic anhydride, aldehyde and ammonium acetate or primary amine to afford the corresponding 2,3-dihydroquinazolin-4(1H)-one derivatives in high yields. The solvent (TFE) can be readily separated from reaction products and recovered in excellent purity for direct reuse.

Full text of DOI:10.1016/j.crci.2012.05.019

C. R. Chimie 15 (2012) 779–783
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´
Full paper/Memoire
Three-component one-pot synthesis of 2,3-dihydroquinazolin-4(1H)-one
derivatives in 2,2,2-trifluoroethanol
*
Samad Khaksar , Saeed Mohammadzadeh Talesh
Department of Chemistry, Ayatollah Amoli Branch, Islamic Azad University, Amol, Iran
A B S T R A C T
A R T I C L E I N F O
Article history:
Trifluoroethanol (TFE) is found to be an efficient and recyclable medium in promoting one-
pot, three-component coupling reactions of isatoic anhydride, aldehyde and ammonium
acetate or primary amine to afford the corresponding 2,3-dihydroquinazolin-4(1H)-one
derivatives in high yields. The solvent (TFE) can be readily separated from reaction
products and recovered in excellent purity for direct reuse.
Received 9 April 2012
Accepted after revision 22 May 2012
Available online 6 July 2012
Keywords:
ß 2012 Published by Elsevier Masson SAS on behalf of Acade´mie des sciences.
Quinazolin-4(1H)-one
Fluorinated solvent
Isatoic anhydride
Reusable
1. Introduction
efficient synthesis of 2,3-dihydroquinazolin-4(1H)-one
derivatives under reflux conditions in 2,2,2-trifluoroethanol
Fluorinated solvents have recently received a great deal
ofattentionaspotentialnew mediafor organicsynthesis [1].
Owing to their unique physicochemical properties (high
hydrogen bonding donor ability, nonvolatility, nonflamm-
ability, polarity, high ionizing power, and low nucleophi-
licity), fluorinated alcohols modify the course of reactions
when they are used as solvents, allowing reactions which
usually require the use of added reagents or metal catalysts
to be carried out under neutral and mild conditions [2–16].
Therefore, today they have marched far beyond this border,
showing their significant role in controlling the reaction as
powerful reaction media. Reactions in fluorinated solvents
are generally selective and without effluents, allowing thus
a facile isolation of the product and a recovery of the solvent
bydistillation.Inordertotakeadvantageoftheseproperties,
we have studied bond cleavage and formation reactions
facilitated by the acidic character and strong hydrogen bond
donor ability of fluorinated alcohols. In a continuation of our
work on the application of fluorinated alcohols in several
organic transformations [17–22], we have developed an
without the use of a catalyst or any other additives. 2,3-
dihydroquinazolinones are very important compounds
partially because of their pharmacological properties which
include wide applications in medicinal chemistry; notable
among them are antifertility, antibacterial, antitumor,
antitremor, antifungle, and mono-amine oxidize inhibition
[23–26]. In addition, 2,3-dihydroquinazolinone derivatives
have recently been evaluated as antagonists of various
biological receptors, such as 5-HT5A related diseases [27],
calcitonin gene-related peptide [28], and vasopressin V3
receptors [29]. Despite 2,3-dihydroquinazolinone usage in
pharmaceutical and other industries, comparatively few
methods for their preparation have been reported. In
accordance with the significance of 2,3-dihydroquinazoli-
none, several synthetic methods have been developed for
the construction of this kind of fused heterocycles from
suitable precursors [30–45]. Very recently, Lee et al.
reported a one-pot synthesis of 2,3-dihydroquinazolin-
4(1H)-ones using ethylenediamine diacetate in aqueous
media under reflux condition [46]. However, some of these
procedures have certain limitations such as harsh reaction
conditions, use of expensive acid catalysts in organic
solvents, long reaction time, tedious work-up, and low
yields. Thus, the development of novel methods for the
* Corresponding author.
E-mail address: S.khaksar@iauamol.ac.ir (S. Khaksar).
1631-0748/$ – see front matter ß 2012 Published by Elsevier Masson SAS on behalf of Acade´mie des sciences.
http://dx.doi.org/10.1016/j.crci.2012.05.019

780
S. Khaksar, S.M. Talesh / C. R. Chimie 15 (2012) 779–783
Table 1
Synthesis of 2,3-dihydroquinazolin-4(1H)-ones in TFE.
Entry
1
Aldehyde
Amine
Product
Yield %
95
NH4OAc
4a
CHO
2
3
4
NH4OAc
NH4OAc
NH4OAc
4b
4c
4d
97
80
85
CHO
Cl
Cl
CHO
Cl
CHO
Cl
CHO
5
NH4OAc
4e
92
O2N
O2N
6
7
NH4OAc
NH4OAc
4f
90
90
CHO
CHO
4g
Br
F
8
9
NH4OAc
NH4OAc
NH4OAc
4h
4i
95
90
85
CHO
CHO
CHO
Me
10
4j
MeO
O
11
12
NH4OAc
NH4OAc
4k
4l
92
85
CHO
CHO
N
H
CHO
13
14
4m
4n
85
90
NH2
NH2
CHO
CHO
CHO
CHO
Cl
15
16
17
4o
4p
4p
85
85
90
NH2
Cl
Me
NH2
NH2
2. Results and discussion
Me
synthesis of dihydroquinazolin-4(1H)-ones is of great
importance because of their potential biological and
pharmaceutical activities. The present investigation
describes a facile preparation of 2,3-dihydroquinazolinone
derivatives via one-pot condensation of isatoic anhydride
and aldehydes with NH4OAc or primary amine in Trifluor-
oethanol (TFE) (Scheme 1).
In an initial endeavor, the reaction was carried out by
simply mixing isatoic anhydride, benzaldehyde and
NH4OAc (Table 1, entry 1) in trifluoroethanol and
refluxing the resulting mixture for 3 hours. The corre-
sponding 2,3-dihydroquinazolin-4(1H)-one 4a was
O
O
O
R1
NH4OAc
or
O
TFE
Reflux, 3 h
N
+
+
H
R
R1
N
H
O
NH2
N
H
4a-q
R
2
1
3
Scheme 1. One-pot three-component condensation of isatoic anhydride, aldehydes and NH4OAc or primary amine in TFE.

S. Khaksar, S.M. Talesh / C. R. Chimie 15 (2012) 779–783
781
O
O
CF3CH2
H
H
R1
+
O
O
N
R1
H2N
H
H
N
O
O
TFE
O
N
H
O
N
H
O
-
I
O
H
O
H
CF3CH2
O
O
CF3CH2
O
R1
R1
O
TFE
H2O
CO2
TFE
N
H
N
H
4
O
CH2CF3
H
N
NH2
III
II
R
H
R
Scheme 2. Proposed mechanism for the synthesis of 2,3-dihydroquinazolin-4(1H)-ones.
obtained in high yield (95%). The application of this
procedure to a variety of substrates (aldehydes and
amines) was investigated and the results are summarized
in Table 1. Various aldehydes, such as aromatic
and heteroaromatic (2a to 2q), could also participate in
the reaction with isatoic anhydride (1) and NH4OAc or
primary amine to give the corresponding 2,3-dihydro-
quinazolin-4(1H)-one products 4a to 4q in good yields. As
shown in Table 1, the effect of electronic nature of the
substituents on the aromatic ring did not show strong
influence on reaction yields. However, ortho-substituted
aromatic aldehydes turned out to be reluctant to undergo
smooth reaction probably because of steric hindrance
(Table 1, entries 3,4). Furthermore, acid sensitive alde-
hydes worked well without any decomposition or
polymerization under these reaction conditions (entry
11). To expand the scope of amine substrates, ammonium
acetate and primary aromatic amines including aniline,
p-toluidine, and 4-chloroaniline were applied to this
protocol. In all cases, the desired reactions took place
successfully to afford a series of 2,3-dihydroquinazolin-
4(1H)-one (4m–4q) in good yields. The experimental
procedure is very efficient, convenient, rapid and has the
ability to tolerate a variety of other functional groups,
such as alkyl, methoxyl, nitro, and halides under these
reaction conditions. One of the major advantages of this
protocol is the isolation and purification of the products,
which have been achieved by simple filtration and
crystallization of the crude products. The results illustrate
the high ability of this method for the synthesis of
substituted 2,3-dihydroquinazolinones with different
groups. Interestingly, the reaction did not proceed to
completion when either ethanol or water alone was used
as solvent, even at reflux conditions. After the reaction,
TFE can be easily separated (by distillation) and reused
without decrease in its activity. For example, the reaction
of isatoic anhydride, benzaldehyde and NH4OAc (Table 1,
entry 1) afforded the corresponding 2,3-dihydroquinazo-
lin-4(1H)-one derivative in 95%, 95%, 92%, 90% and 90%
isolated yield over five cycles. When we carried out the
reaction in TFE at room temperature, the reaction
proceeded very slowly to give very poor yields.
A tentative mechanism for the formation of 2,3-
dihydroquinazolin-4(1H)-ones was proposed (Scheme
2). In this process, the TFE acts as Brønsted acid [47]
and plays a significant role in increasing the electrophilic
character of the electrophiles. The hydrogen bond donor
ability might not be important in this case. Actually, the
hydrogen bond donating ability of these solvents drops as
temperature rises owing to the fact that hydrogen bond
formation is exothermic [48,49]. The polar transition state
of the reaction could be stabilized well by the high
ionizing solvent TFE. First, the isatoic anhydride is
activated by TFE 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). Subsequently,
the reaction of activated aldehyde with II proceeds to
afford intermediate III that is converted to product 4 via an
intramolecular cyclization.
3. Conclusions
In summary, we have developed efficient synthesis of
2,3-dihydroquinazolin-4(1H)-one derivatives via one-pot
condensation of isatoic anhydride, aldehydes and NH4OAc
in TFE without using any catalyst or additives. In contrast
to the existing methods using potentially hazardous
catalysts/additives, this new method offers the following
competitive advantages:
ꢀ
ꢀ
ꢀ
avoiding the use of any base, metal or Lewis acid catalyst;
short reaction time;
ease of product isolation/purification by non-aqueous
work-up;
ꢀ
ꢀ
ꢀ
high chemoselectivity;
no side reaction;
low costs and simplicity in process and handling. The
recovered TFE can be reusable. Further studies and

782
S. Khaksar, S.M. Talesh / C. R. Chimie 15 (2012) 779–783
efforts to extend the scope of this method for other useful
13C NMR (DMSO-d6, 100 MHz):
d = 20.7, 66.4, 114.9, 117.1,
reactions are currently underway.
126.7, 127.3,128.7, 133.2, 137.2, 137.7, 138.7, 147.9, 163.6.
2-(4-Methoxyphenyl)-2,3-dihydroquinazolin-4(1H)-
one (4j); white solid, m.p 179–180 8C (Lit.[43] 178–
180 8C); IR (KBr): 3296, 3174, 2832, 1650, 1608,
4. Experimental
4.1. General procedure
1503,1482, 1386, 1301, 1240 cmÀ1
.
1H NMR (DMSO-d6,
= 3.83 (s, 3H), 5.79 (s, 1H), 6.76 (t, J = 7.4 Hz,
400 MHz):
d
Isatoic anhydride (1 mmol), aldehydes (1 mmol) and
NH4OAc (1 mmol) were dissolved in TFE (2 mL) and was
refluxed for the stipulated time. The progress of the
reaction is monitored by TLC. After completion of the
reaction, the corresponding solid product 4 was obtained
through simple filtering, and recrystallized from ethanol to
yield the highly pure 2,3-dihydroquinazolin-4(1H)-one
derivatives. The physical data (mp, IR, NMR) of known
compounds were found to be identical with those reported
in the literature. Spectroscopic data for selected examples
are shown below.
1H), 6.83(d, J = 7.6 Hz, 1H), 7.04 (dt, J1 = 8.6 Hz, J2 = 2.0 Hz,
2H), 7.10 (br s, 1H, NH), 7.30–7.35 (m, 1H), 7.51–771 (m,
3H), 8.28 (br s, 1H, NH); 13C NMR (DMSO-d6, 100 MHz):
d
= 55.2, 66.3, 113.6, 114.4, 115.1, 117.07, 127.3,128.2,
133.2, 133.4, 148.0, 159.5, 163.6.
2,3-Dihydro-3-phenyl-2-(4-chlorophenyl)quinazo-
lin-4(1H)-one (4n); white solid, m.p 216–218 8C (Lit.[45]
216-217 8C); IR (KBr): 3294, 3025, 1631, 1613, 1506, 1486,
1414, 1385, 1312, 1161, 1088, 1014 cmÀ1. 1H NMR (DMSO-
d6, 400 MHz):
d = 6.33 (d, J = 2.7 Hz, 1H), 6.74 (t, J = 7.4 Hz,
1H),6.77 (d, J = 7.8 Hz, 1H), 7.18–7.22 (m, 1H), 7.25–7.29
(m, 3H), 7.31–7.42 (m, 6H), 7.67–7.73 (m, 2H); 13C NMR
2,3-Dihydro-2-phenylquinazolin-4(1H)-one
(4a);
white solid, mp 225–227 8C (Lit.[44] mp 218–220 8C); IR
(DMSO-d6, 100 MHz): d = 72.1, 114.8, 115.3, 117.7, 126.1,
126.2, 128.1, 128.4, 128.5, 128.6, 132.9, 133.8, 139.6, 140.5,
146.4, 162.1.
(KBr): 3302, 3176, 3062, 1653, 1610, 1508, 1482; 1H NMR
(500 MHz, DMSO-d6):
d = 5.76 (s, 1H), 6.68 (t, J = 7.4 Hz,
1H), 6.76 (d, J = 8.09 Hz, 1H), 7.10 (br s, 1H, NH), 7.25 (t,
J = 7.3 Hz, 1H), 7.33–7.41 (m, 3H), 7.50 (d, J = 7.44 Hz,, 2H),
7.62 (d, J = 7.7 Hz,, 1H), 8.28 (br s, 1H, NH); 13C NMR
2,3-Dihydro-3-phenyl-2-(4-methylphenyl)quinazo-
lin-4(1H)-one (4o); white solid, m.p 222–224 8C (Lit.[43]
223–226 8C); IR (KBr): 3296, 3015, 1633, 1611, 1586, 1505,
(DMSO-d6, 100 MHz):
d
= 67.4, 115.2, 115.8, 117.9, 127.7,
1486 cmÀ1. 1H NMR (DMSO-d6, 400 MHz):
d = 2.22 (s, 3H),
128.2, 129.1, 129.3, 134.1, 142.5, 148.7, 164.4.
6.24 (d, J = 2.5 Hz, 1H), 6.71 (t, J = 7.6 Hz, 1H), 6.76 (d,
J = 8.1 Hz, 1H), 7.10 (d, J = 7.8 Hz, 2H), 7.16–7.21 (m, 1H),
7.25–7.35 (m, 7H), 7.61–7.74 (m, 2H); 13C NMR (DMSO-d6,
100 MHz): d = 20.6, 72.4, 114.8, 115.4, 117.4, 126.1, 126.1,
126.4, 127.9, 128.5,128.9, 133.7, 137.5, 137.8, 141.1, 146.5,
162.2.
2-(4-Chlorophenyl)-2,3-dihydroquinazolin-4(1H)-
one (4b); white solid, m.p 201–203 8C (Lit.[43] 198–
200 8C); IR (KBr): 3307, 3186, 3025, 1667, 1651, 1607,
1504, 1483, 1383, 1292, 1133 cmÀ1
400 MHz):
.
1HNMR (DMSO-d6,
d
= 5.77 (s, 1H), 6.70(t, J = 8.1 Hz, 1H), 6.95(d,
J = 6.4 Hz, 1H), 7.15 (br s, 1H, NH), 7.22–7.47 (m, 3H), 7.51
(d, J = 8.8 Hz, 2H), 7.61 (dd, J1 = 7.8 Hz, J2 = 1.3 Hz, 1H), 8.34
Acknowledgement
(br s, 1H, NH); 13C NMR (DMSO-d6, 100 MHz):
d= 65.8,
114.4, 115.1, 117.27, 127.3, 128.3, 128.7, 132.9, 133.3,
140.7, 147.7, 163.4.
2,4-Dichloro-2,3-dihydroquinazolin-4(1H)-one (4d);
white solid, m.p 182–184 8C (Lit.[44] 181-185 8C); IR (KBr):
3337, 3179, 3025, 1661 cmÀ1. 1HNMR (DMSO-d6, 400 MHz):
This research is supported by the Islamic Azad
University, Ayatollah Amoli Branch.
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