A Domino Process for the Sustainable Synthesis of Quinazolin-4(3 H)-ones with Direct Chemo- and Regioselective Bromination

Article abstract of DOI:10.1055/s-0037-1610226

An efficient approach is reported for the direct and sustainable construction of quinazolin-4(3 H)-ones through a three-component reaction of isatoic anhydride, primary amines, and bromoacetyl bromide or chloroacetyl chloride in the presence of K ₂ CO ₃ in DMSO. With bromoacetyl bromide, mono- or dibrominated quinazolinone scaffolds were obtainable in a chemo- and regioselective manner.

Full text of DOI:10.1055/s-0037-1610226

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© Georg Thieme Verlag Stuttgart · New York
2018, 29, A–E
letter
A
en
E. Sheikhi et al.
Letter
Synlett
A Domino Process for the Sustainable Synthesis of Quinazolin-
4(3H)-ones with Direct Chemo- and Regioselective Bromination
Ehsan Sheikhi*a
Mehdi Adib*a
Rozita Yazzafa
Mehdi Jahania
0
0
0
0
0-
0
0
3
1-
3
9
5
4-
8
9
3
8 examples
76–95%
R = Bn, CH2-2-ClC6H4, CH2-4-FC6H4,
4-Tol, 4-EtC6H4, Bu, Pr, (CH2)4Me
O
N
O
Br
R
BrCH2COBr, DMSO, K2CO3
90 °C, 3 h
N
i) Novel protocol for the synthesis
of 4(3H)-quinazolinones
ii) Chemo- and regioselective
bromination by bromoacetyl
bromide
iii) Selective synthesis of mono- or
dibrominate by use of different
amounts of bromoacetyl bromide
and solvent
Br
Mehdi Ghavidelb
O
5 examples
75–92%
R = Bn, CH2-2-ClC6H4, 4-Tol,
Pr, (CH2)4Me
R
R
O
ClCH2COCl, DMSO, K2CO3
90 °C, 3 h
N
N
RNH2
+
a School of Chemistry, College of Science, University of
Tehran, PO Box 14155-6455, Tehran, Iran
ehsan.sheikhi@gmail.com
madib@khayam.ut.ac.ir
b Department of Chemistry, Urmia University, 57154 Urmia,
Iran
N
H
O
N
O
iv) One-pot method with simple
workup
v) Good to excellent yields
12 examples
85–95%
R = Bn, CH2-2-ClC6H4, CH2-4-FC6H4,
CH2-4-ClC6H4, CH2-4-Tol,
CH2-4-MeOC6H4, 4-Tol, 4-EtC6H4,
i-Bu, Bu, Pr, (CH2)4Me
Br
2 BrCH2COBr, DMSO, K2CO3
90 °C, 3 h
N
Received: 03.05.2018
Accepted after revision: 08.07.2018
Published online: 24.08.2018
Table 1 Optimization of the Reaction of Isatoic Anhydride, Benzyl-
amine, and Bromoacetyl Bromide in an Equimolar Ratioa
DOI: 10.1055/s-0037-1610226; Art ID: st-2018-k0380-l
O
N
O
O
Abstract An efficient approach is reported for the direct and sustain-
able construction of quinazolin-4(3H)-ones through a three-compo-
nent reaction of isatoic anhydride, primary amines, and bromoacetyl
bromide or chloroacetyl chloride in the presence of K2CO3 in DMSO.
With bromoacetyl bromide, mono- or dibrominated quinazolinone
scaffolds were obtainable in a chemo- and regioselective manner.
Br
N
Ph
O
Br
+
+
NH2
Ph
Br
N
H
O
Br
1
2a
3a
4aa
Entry
Solvent
Base (equiv)
Temp (°C)
Yieldb (%)
Key words multicomponent reactions, quinazolinones, bromoacetyl
bromide, regioselectivity, bromoquinazolines
1
2
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMF
–
r.t.
r.t.
r.t.
50
90
50
90
100
120
90
90
90
90
90
90
90
90
NRc
NR
10
11
13
70
95
94
80
13
13
NR
NR
48
33
51
50
K2CO3 (0.5)
K2CO3 (1.0)
K2CO3 (1.0)
K2CO3 (1.0)
K2CO3 (1.0)
K2CO3 (1.0)
K2CO3 (1.0)
K2CO3 (1.0)
K2CO3 (1.0)
K2CO3 (1.0)
K2CO3 (1.0)
K2CO3 (1.0)
Et3N (1.0)
t-BuOK (1.0)
DBU (1.0)
3
Quinazolin-4(3H)-ones (QZs), as a significant series of
benzo-fused N-containing heterocyclic compounds, are of
interest because of their wide range of useful pharmacolog-
ical and therapeutic activities, including anticancer,1 anti-
convulsant,2 antioxidant,3 antiinflammatory,4 antitubercu-
lar,5 antiulcer,6 antiviral,7 anti-HIV,8 and antibiotic activi-
ties.9 Febrifugine10 and isofebrifugine11 are two bioactive
natural products that contain a quinazolinone moiety and
possess antimalarial activity. Due to this wide range of
applications, numerous synthetic routes have been devel-
oped for the preparation of these heterocycles.12
As part of our continuing effort to develop efficient
methods for the preparation of biologically active organic
compounds, we recently reported an oxidative process for
the synthesis of 2,3-dihydroquinazoline-4-ones.13 Here, we
present a new route for the synthesis of QZs through a
DMSO-based oxidative reaction. To achieve this goal, we
studied the reaction between isatoic anhydride, primary
amines, and bromoacetyl bromide or chloroacetyl chloride
under various reaction conditions. These substrates are
selectively linked through C–N bond-formation and C–C
bond-cleavage steps, along with direct chemo- and regiose-
lective bromination in the case of bromoacetyl bromide.
4
5
6
7
8
9
10
11
12
13
14
15
16
17
toluene
1,4-dioxane
H2O
DMSO
DMSO
DMSO
DMSO
piperidine (1.0)
a Reaction conditions: (entries 1–5) 1 (1 mmol), 2a (1 mmol), 3a (1 mmol),
base, DMSO (3 mL), 3 h. (entries 6–17): 1 (1 mmol) and 2a (1 mmol),
solvent (3 mL), 1 h; then 3a (1 mmol), base (1 mmol), stirring, 2 h.
b Isolated yield.
c NR = No reaction.
© Georg Thieme Verlag Stuttgart · New York — Synlett 2018, 29, A–E

B
E. Sheikhi et al.
Letter
Synlett
Initially, we chose the reaction between isatoic an-
hydride (1), benzylamine (2a), and bromoacetyl bromide
(3a) as a model reaction, and we tested several reaction
conditions (Table 1). To our delight, the doubly brominated
QZ 4aa was detected in 95% yield when 1 and 2a were treat-
ed in DMSO at 90 °C for one hour, followed by subsequent
addition of 3a and K2CO3 and stirring the mixture under the
same conditions for a further two hours (entry 7).
Having pinpointed the optimal conditions, we then
investigated the scope of the reaction by using various pri-
mary amines 2 with bromoacetyl bromide (3a) or chloro-
acetyl chloride (3b) for this three-component reaction in
the presence of K2CO3 in DMSO at 90 °C (Table 2). We found
that when one equivalent of 3a was used, the dibrominated
products 4aa–ah were obtained; whereas when one equiv-
alent of 3b was used, chlorination did not occur (4ba–be).
All the QZs 4aa–be were obtained in good to excellent
yields.14
Table 3 Optimization of the Reaction Between Isatoic Anhydride,
Benzylamine, and Excess Bromoacetyl Bromidea
O
O
O
Br
N
Ph
O
n
+
+
NH2
Br
Ph
Br
N
N
H
O
1
2a
3a
4ca
Entry
3a (equiv)
DMSO (mL)
Yieldb (%)
1
2
3
4
5
6
7
8
2
3
NCc
31
48
53
65
87
89
94
2.5
3
3
3
3
2.5
2
3
3
1.5
1.5
1.5
2.5
2
a Reaction conditions: 1 (1 mmol), 2a (1 mmol), DMSO, 90 °C, 1 h; then, 3a,
K2CO3 (1 mmol), stirring, 2 h.
Table 2 Synthesis of QZs 4aa–ah and 4ba–be by the use of 3a or 3ba
b Isolated yield.
O
O
c NC = Nonclean reaction.
O
Y
R
O
DMSO, K2CO3
90 °C, 3 h
N
X
RNH2
+
+
X
By use of 1, 2, and two equivalents of 3a, the monobro-
minated QZs 4ca–cl were obtained in high yields (Table 4).
In addition, the reaction between 1, benzylamine (2a), and
3b (2 equiv) gave 4ba.
N
H
O
N
Y
1
2
3a, X = Br
3b, X = Cl
4a, Y = Br
4b, Y = H
O
X = Br (3a); Y = Br
4aa: R = Bn, 95%
Table 4 Synthesis of Monobrominated QZs 4ca–cla,b
Br
R
N
O
O
N
4ab: R = CH2-2-ClC6H4, 85%
4ac: R = CH2-4-FC6H4, 78%
4ad: R = 4-Tol, 91%
N
O
Br
R
Br
DMSO, K2CO3
90 °C, 3 h
O
N
Br
RNH2
+
+
2
4a
Br
N
H
1
O
4ae: R = 4-EtC6H4, 84%
4af: R = Bu, 78%
4c, yield%b
2
3a
4ca: R = Bn, 94%
4cc: R = CH2-4-FC6H4, 85%
4cb: R = CH2-2-ClC6H4, 90%
4cd: R = CH2-4-Tol, 95%
4cf: R = 4-Tol, 89%
4ag: R = Pr, 80%
4ah: R = (CH2)4Me, 76%
X = Cl (3b); Y = H
4ce: R = CH2-4-ClC6H4, 91%
4cg: R = 4-EtC6H4, 85%
4ci: R = i-Bu, 90%
O
4ch: R = 4-MeOC6H4, 87%
4cj: R = Bu, 93%
R
4ba: R = Bn, 88%
N
4bb: R = CH2-2-ClC6H4, 83%
4bc: R = Pr, 81%
N
4ck: R = Pr, 95%
4cl: R = (CH2)4Me, 90%
4b
a Reaction conditions: 1 (1 mmol), 2 (1 mmol), DMSO (1.5 mL), 90 °C, 1 h;
then 3a (2 mmol), K2CO3 (1 mmol), stirring, 90 °C, 2 h.
b Isolated yields are reported.
4bd: R = (CH2)4Me, 75%
4be: R = 4-Tol, 92%
a Reaction conditions: 1 (1 mmol), 2 (1 mmol), DMSO (3 mL), 90 °C, 1 h;
then 3 (1 mmol), K2CO3 (1 mmol), stirring (90 °C), 2 h.
b Isolated yield.
The bromination occurred chemoselectively in the
benzo ring of the QZ, and regioselectively at the C6 and C8
positions for dibromination and at the C6 position for
monobromination.
In the monobrominated adducts 4c, para-selective bro-
mination was confirmed on the basis of chemical shifts and
coupling patterns for the three hydrogen atoms on the
phenylene ring in the 1H NMR spectra of these compounds.
For example, in the 1H NMR spectrum of 4cc, the most
Next, the three-component reaction was carried out
with an excess of 3a (for optimization of the reaction condi-
tions, see Table 3). Surprisingly, we found that the reaction
of 3a (2 equiv) in the presence of K2CO3 in DMSO (1.5 mL)
afforded the monobrominated QZ 4ca in 94% yield (Table 3,
entry 8).
© Georg Thieme Verlag Stuttgart · New York — Synlett 2018, 29, A–E

C
E. Sheikhi et al.
Letter
Synlett
O
O
O
O
Br
NH2
N
Tol
Br
DMSO
H
Br
+
+
N
O
NH
90 °C, 1 h
H
1
2b
3a
5, 93%
Scheme 1 The reaction between 1, 2b and 3a in the absence of K2CO3
O
O
O
Br
Br
Br
N
Tol
N
Tol
N
Tol
H
H
H
NH2
NH
– HBr
– CO2
NH
OH
OH
6
7
5
Br
O
O
Scheme 2 Proposed mechanism for the formation of 5 in the absence of K2CO3
deshielded hydrogen (H5, ortho to the carbonyl group)
resonated at δ = 8.45 ppm as a doublet with Jmeta = 2.3 Hz.
4a via 23 and 24. In a control experiment, dibrominated
anthranilamide 15 (R = Bn) was prepared according to the
reported procedure17 and treated with glyoxylic acid (19)
under the reaction conditions to give QZ 4a in 96% yield.
A reasonable mechanism for the formation of mono-
brominated QZs 4c is provided in Scheme 4. First, in the
presence of an excess of the acylation reagent 3a in a smaller
quantity of DMSO, the anthranilamide 11 might be acylated
to yield amide intermediate 25. Due to both acylation and
steric factors, amide 25 has a lower reactivity toward aro-
matic electrophilic bromination than does the correspond-
ing amine 11 and might therefore undergo monobromina-
tion by bromodimethylsulfonium 9 to give 26. Intramolecu-
lar cyclization and dehydration might then give 2-
bromomethylquinazolin-4(3H)-one 27; this might undergo
Kornblum oxidation in the presence of K2CO3 to give 4(3H)-
oxoquinazolin-2-carboxaldehyde 29 via 28. Oxidation con-
verts 29 into 4(3H)-oxoquinazolin-2-carboxylic acid 30,
which undergoes thermal decarboxylation to afford QZ 4c.
In the case of 3b, the formation of a QZ with no chlori-
nation might result from the lower activity of the chloride
anion in comparison with that of the bromide anion for the
formation of the corresponding halodimethylsulfonium
species.
In conclusion, we have devised an efficient one-pot syn-
thesis of QZs with direct chemo- and regioselective bromi-
nation. This can be regarded as a new and direct approach
for the preparation of synthetically and pharmaceutically
relevant QZ scaffolds. Advantages of the method include its
simple starting materials, short reaction times, simple pro-
cedures and workup, and good to excellent yields of prod-
ucts, along with chemo- and regioselectivity and a control-
lable degree of bromination. We hope that this protocol
might be of value to others seeking novel synthetic scaffolds
with unique properties for pharmaceutical chemistry pro-
grams.
4
The hydrogen atom H7 was observed as a doublet of
3
4
doublets at δ = 7.84 with Jortho = 8.7 Hz and Jmeta = 2.3 Hz.
The hydrogen atom H8 appeared as a doublet at δ = 7.59
3
with Jortho = 8.7 Hz (Figure S1 in the Supporting Informa-
tion).
We also examined the reaction of isatoic anhydride (1),
4-methylbenzylamine (2b), and one or two equivalents of
bromoacetyl bromide (3a) in DMSO in the absence of K2CO3;
this gave the N-methylated anthranilamide 5 exclusively
(Scheme 1).
The formation of 5 can be explained by alkylation of the
monobrominated QZ 6 by bromoacetic acid generated in
situ to give the N-arylated glycine intermediate 7, which
undergoes decarboxylation under the reaction conditions
to afford 5 (Scheme 2)
These transformations and the formation of the
quinazolin-4(3H)-one scaffold probably involve a complex
multistep sequence of events. On the basis of our results, a
possible mechanism for the formation of the dibrominated
QZ 4a is shown in Scheme 3. It is reasonable to assume that
the reaction of 3a with two DMSO molecules forms inter-
mediate 8, which undergoes nucleophilic addition by the
bromide anions to generate two molecules of the electro-
philic bromodimethylsulfonium species 9 and the glycolic
acid dianion 10. Then, anthranilamide 11, generated by nu-
cleophilic addition of amine 2 to isatoic anhydride 1, under-
goes two electrophilic substitutions by the two BDMS mol-
ecules 9 to give the dibrominated anthranilamide 15 via in-
termediates 12–14. Next, the glycolic acid 16 generated in
situ might undergo a Kornblum-type oxidation15 by DMSO
under the reaction conditions to produce glyoxylic acid (19)
via 17 and 18. Glyoxylic acid (19) might be attacked by
anthranilamide 15 to give oxotetrahydroquinazoline-2-
carboxylic acid 21, which, in turn, might be oxidized to the
oxodihydroquinazolin-2-carboxylic acid 22. Carboxylic acid
22 might undergo thermal decarboxylation16 to afford QZ
© Georg Thieme Verlag Stuttgart · New York — Synlett 2018, 29, A–E

D
E. Sheikhi et al.
Letter
Synlett
_
O
O
O
+
+
+
Br
+
S
+
S
O
+
O
+
S
O
S
–O
Br
O–
–O
S
S
Br
+
_
O
Br
O–
R
Br
base
R
Br
Br
H
N
N
Br
H
H
12
– Me2S
3a
8
9
10
9
Base
NH2
NH2
base
– CO2
O
O
13
– Me2S
O
R
O
Br
Br
N
O
H
–O
OH
+
RNH2
S
+
S
+
–O
O–
NH2
N
H
O
10
7
1
2
11
O
+
S
OH
O
+
O
–O
O–
O
O
O
Br
R
Br
R
base
OH
base
+
S
N
H
N
H
OH
O
O
H
OH
HO
HO
S
HO
O
– Me2S
– H2O
base
OH
NH2
NH2
H
O
–O
Br
15
Br
14
H
O–
HO
O
16
17
18
19
O
O
O
O
O
[O]
Br
Br
R
O
Br
R
Br
R
N
Br
R
O
NHR
O
N
N
N
HO
H
O–
+
N
– H2O
OH
OH
OH
H
N
N
H
N
NH2
Br
Br
Br
O
Br
H
O
Br
15
19
20
21
22
23
O
O
Br
R
Br
R
N
N
_
+
N
– CO2
N
Br
4a
Br
H
24
Scheme 3 Proposed mechanism for the formation of dibrominated QZs 4a
Br
O
N
O
O
O
–O
S
9
S
O
Br
R
Br
N
NHR
NHR
NHR
Br
+
Br
– H2O
NH2
11
NH
NH
Br
Br
Br
3a
25
26
27
O
O
O
N
O
O
O
N
Br
R
Br
R
H
[O]
Br
R
Br
R
N
N
N
N
Br
O
O
O
– CO2
S
N
N
H
OH
28
29
30
4c
base
Scheme 4 Proposed mechanism for the formation of monobrominated QZs 4c
Funding Information
References and Notes
This research was supported by the Research Council of the University
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Supporting Information
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S
u
p
p
ortioInfgrmoaitn
S
u
p
p
ortiInfogrmoaitn
© Georg Thieme Verlag Stuttgart · New York — Synlett 2018, 29, A–E

E
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Letter
Synlett
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A mixture of isatoic anhydride (1; 1 mmol) and the appropriate
primary amine 2 (1 mmol) in DMSO (3 mL) was stirred at 90 °C
for 1 h. BrCH2COBr (3a; 1 mmol) and K2CO3 (1 mmol) were
added, and the mixture was stirred at 90 °C for a further 2 h.
When the reaction was complete (TLC), the mixture was cooled
to r.t. and the reaction was quenched with H2O (3 mL). The
mixture was then stirred for 10 min at r.t., and the resulting
precipitate was collected by filtration, washed with H2O, dried,
and crystallized from EtOH.
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3-Benzyl-6,8-dibromoquinazolin-4(3H)-one (4aa)
White solid; yield: 0.374 g (95%); mp 173–175 °C (Lit.1 176.5–
178.5 °C). IR (KBr): 1679 (C=O), 1596 (C=N), 1540, 1492, 1443,
1360, 1306, 1254, 1170, 1142, 1076, 1029, 996, 958, 875, 811,
723, 693, 670, 627 cm–1 1H NMR (300.1 MHz, CDCl3): δ = 5.21
.
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(s, 2 H, CH2), 7.37–7.41 (m, 5 H, 5CH), 8.16 (d, J = 2.1 Hz, 1 H,
CH), 8.24 (s, 1 H, NCHN), 8.44 (d, J = 2.1, 1 H, CH). 13C NMR (75.5
MHz, CDCl3): δ = 50.1 (CH2), 120.8, 123.4 and 124.4 (3 C), 128.2
(2CH), 128.7 (CH), 129.2 (2CH and CH), 134.9 (C), 140.4 (CH),
144.7 (C), 147.3 (NCHN), 159.4 (C=O). EI-MS, m/z (%): 396 [M+,
81Br2] (17), 394 [M+, 81Br79Br] (35), 392 [M+, 79Br2] (19), 315 (4),
288 (4), 234 (4), 116 (1), 104 (1), 91 (100), 74 (3), 65 (14), 51 (3).
Anal. Calcd for C15H10Br2N2O (394.06): C, 45.72; H, 2.56; N, 7.11.
Found: C, 45.66; H, 2.43; N, 7.02.
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