Iodine-catalyzed oxidative system for cyclization of primary alcohols with o-aminobenzamides to quinazolinones using DMSO as the oxidant in dimethyl carbonate

Article abstract of DOI:10.1039/c3ra40872h

The iodine catalyzed one-pot two-step oxidative system for cyclization of primary alcohols with o-aminobenzamides to quinazolinones using DMSO as the oxidant has been achieved, providing a convenient and efficient method for the synthesis of quinazolinones in good to excellent yields via in situ oxidation of primary alcohols to aldehydes. The reaction was carried out in the green solvent DMC, under atmospheric conditions. The procedure is suitable for aromatic or alkyl primary alcohols. The Royal Society of Chemistry 2013.

Full text of DOI:10.1039/c3ra40872h

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Iodine-catalyzed oxidative system for cyclization of
primary alcohols with o-aminobenzamides to
quinazolinones using DMSO as the oxidant in dimethyl
carbonate3
Cite this: DOI: 10.1039/c3ra40872h
Wenlei Ge,a Xun Zhuab and Yunyang Wei*a
The iodine catalyzed one-pot two-step oxidative system for cyclization of primary alcohols with
o-aminobenzamides to quinazolinones using DMSO as the oxidant has been achieved, providing a
convenient and efficient method for the synthesis of quinazolinones in good to excellent yields via in situ
oxidation of primary alcohols to aldehydes. The reaction was carried out in the green solvent DMC, under
atmospheric conditions. The procedure is suitable for aromatic or alkyl primary alcohols.
Received 20th February 2013,
Accepted 19th April 2013
DOI: 10.1039/c3ra40872h
www.rsc.org/advances
palladium-catalyzed carbonylation of aryl halides and C–H
bonds, which represented a straightforward approach to
carboxylic acids and their derivatives. Nitrogen-containing
heterocycles of quinazolinones were synthesized through a
palladium-catalyzed intramolecular or intermolecular carbox-
amidation procedure.11
Introduction
Quinazoline and its derivatives exist in a variety of natural
products and synthetic drugs1 and play a significant role in
medicinal chemistry for their biological activity, such as
hypolipidemic,2 anti-inflammatory,3 anti-convulsant,4 anti-
ulcer,5 and anti-cancer.6 Some quinazolinones are currently
attracting considerable attention due to their therapeutic value
in the treatment of tuberculosis.7
There has been a long-standing interest in the development
of new methods for the synthesis of quinazolinones due to
their important applications.8 A number of different strategies
have been devised for condensation between aldehydes and
o-aminobenzamides followed by oxidation of the aminal
intermediate.9 Stoichiometric or large excess amounts of
oxidants, such as KMnO4,9a CuCl2,9b I2,9c DDQ,9d and
MnO2,9e were required for this oxidation.
Due to copper-catalyzed Ullmann-type couplings making
great achievements in recent years,10 some quinazolinones
were synthesized through the couplings between 2-haloben-
zoic acid derivatives and ammonia sources, including amidi-
nes,10a benzylamines10b and a-amino acids.10c Catalytic
amounts of metal catalysts and stoichiometric amounts of
bases were necessary for the reaction.
In the past three years, noble metal catalyzed systems for
N-alkylation of amides or sulfonamides with various alcohols
based on catalytic hydrogen transfer reactions have been
developed rapidly,12 which provided a nice inspiration for
chemists to construct N-containing heterocycles. In 2011, J.
Zhou and Fang described a one-pot oxidative cyclization of
primary alcohols with o-aminobenzamides to quinazolinones
catalyzed by iridium under hydrogen transfer conditions.13
Very recently, A. J. A. Watson and co-workers reported
ruthenium-catalyzed hydrogen transfer for the conversion of
alcohols into either 2,3-dihydro-quinazolines or quinazo-
lines.14 Both reactions contained the transformation of
alcohols to aldehydes catalyzed by Ir or Ru complexes.
In view of the development of green chemistry, the
enhancement in people’s awareness of environmental protec-
tion in recent years and our continuous work on the C–S, C–N,
and C–O bond forming reactions,15 an efficient iodine
catalyzed one-pot two-step oxidative system for cyclization of
primary alcohols with o-aminobenzamides to quinazolinones
was developed. The reaction was carried out in an environ-
mentally benign solvent, dimethyl carbonate (DMC), in the
presence of a mild oxidant, DMSO, using 5 mol% of iodine as a
catalyst and without the need for oxygen and moisture-free
reaction conditions (Scheme 1).
In order to explore a direct and convenient synthetic
strategy for quinazolinones, chemists paid much attention to
aSchool of Chemical Engineering, Nanjing University of Science and Technology,
Nanjing 210094, P. R. China. E-mail: ywei@mail.njust.edu.cn;
Fax: +86(25)84317078
bDepartment of Chemical Engineering, Yancheng Textile Vocational Technology
College, Yancheng, P. R. China.
Electronic supplementary information (ESI) available. See DOI: 10.1039/
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Table 1 Optimization of reaction conditions for the synthesis of quinazolinones
in one pota
Scheme 1 Molecular iodine catalyzed cyclization of primary alcohols with
o-aminobenzamides to quinazolinones using DMSO as an oxidant.
Entry Catalyst (mmol) Solvent Oxidant (equiv.) T (uC) Yieldb (%)
1
2
3
4
5
6
7
8
I2
I2
I2
I2
I2
I2
I2
I2
I2
I2
I2
I2
I2
I2
I2
I2
DMSO
DMF
DCE
Toluene
DMC
DMC
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
80
100
100
100
100
100
100
100
91
0
0
0
0
Results and discussion
In recent years, molecular iodine has drawn considerable
attention as an inexpensive, nontoxic, nonmetallic, and readily
available catalyst for effecting various organic transforma-
tions.16 However, to the best of our knowledge, there are no
reports on the cyclization of primary alcohols with o-amino-
benzamides to quinazolinones using an iodine–DMSO oxida-
tive system under green and atmospheric conditions.
We initiated our study by examining the reaction of benzyl
alcohol (1a) with o-aminobenzamide (2a) in a one-pot two-step
manner. Benzyl alcohol was heated in DMSO at 100 uC for 10 h
in the presence of 10 mol% of iodine. Then o-aminobenza-
mide was added to the reaction mixture. We were delighted to
find that product 3a was obtained with a 91% yield after
column chromatography (Table 1, entry 1). Encouraged by this
result, the cyclization of o-aminobenzamide and benzyl
alcohol was optimized and the results are summarized in
Table 1.
DMSO (3)
76
78
Trace
42
46
60
84
93
93
81
85
90
83
0
Toluene DMSO (3)
DMC
DMC
DMC
DMC
DMC
DMC
DMC
DMC
DMC
DMC
DMC
DMC
DMC
DMC
DMC
DMC
O2
9
H2O2 (3)
Oxone (3)
TBHP (3)
DMSO (4)
DMSO (5)
DMSO (5)
DMSO (5)
DMSO (5)
DMSO (5)
DMSO (5)
DMSO (5)
DMSO (5)
DMSO (5)
DMSO (5)
—
10
11
12
13
14c
15d
16c
17c
18
19
20
21
22
23
NIS
NBS
TBAI
I2O5
DIB
0
0
0
83
I2 (2)
a
Reaction conditions: 2a (1 mmol), 1a (1.2 mmol), catalyst (10
mol%), solvent (1 ml), in a sealed tube under an air atmosphere.
b
Yield of isolated product after column chromatography based on
At first, several kinds of solvents were tested under an air
atmosphere, a product was not detected without the addition
of DMSO (Table 1, entries 2–5). Then 3 equivalents of DMSO
were used as an oxidant for the cyclization in DMC and
toluene, and yields of 76% and 78% for 3a were obtained,
respectively (Table 1, entries 6 and 7). To avoid the use of
environmentally harmful solvents, the green solvent DMC was
chosen for subsequent exploitation of optimal experimental
conditions. Several oxidants such as O2, H2O2, Oxone and
TBHP were then tested for the reaction (Table 1, entries 8–11).
It was found that in the presence of oxidants tested except for
DMSO, the yield of the product decreased due to the
peroxidation of benzyl alcohol to benzoic acid. The dosages
of iodine and DMSO were also tested and it was found that 5
mol% iodine gave the highest yield of 93% in the presence of 5
equivalents of DMSO at 100 uC (Table 1, entries 12–16).
Based on this result, other iodine-containing non-metal
catalysts such as NIS, TBAI, I2O5, and iodobenzene diacetate
(DIB), were screened for the reaction. Only NIS showed the
same catalytic activity as iodine (Table 1, entries 17 and 19–
21). Furthermore, NBS was tested for the reaction, which can
also form an oxidative system with DMSO and gave a slightly
lower yield of 83% (Table 1, entry 18). The product and
intermediate M1 benzyl aldehyde were not formed without the
presence of any catalyst under normal conditions (Table 1,
entry 22). It was found that the desired product could also be
obtained in a good yield by using 2 equivalents of iodine as an
oxidant, which may prove that the aldehyde was formed via in
c
d
2a. Iodine (5 mol%) was used. Iodine (3 mol%) was used.
situ oxidation of the primary alcohol by iodine (Table 1, entry
23).
Having optimized the reaction conditions, a variety of
primary alcohols were tested to determine the scope and
limitations of the method. Results listed in Table 2 demon-
strate that most of the primary alcohols 1 tested underwent
smooth transformation to afford the corresponding quinazo-
linone 3 in high yields. In general, benzylic alcohols bearing
electron-donating groups on the benzene ring were more
reactive than those with electron-withdrawing groups (Table 2,
entries 1–11). Heteroaryl primary alcohols proceeded well for
the present procedure (Table 2, entries 12 and 13). We are
delighted to disclose that satisfactory yields were also obtained
from cyclization of o-aminobenzamide with cinnamic alcohol
and phenethyl alcohol (Table 2, entries 11 and 14). The alkyl
primary alcohol, butyl alcohol, could also be transformed to
the desired product with 10 mol% PTSA as an additive
(Table 2, entry 15).
To explore the catalytic mechanism, a series of blank and
parallel experiments were tested for the cyclization of
o-aminobenzamide and benzyl aldehyde M1, and the results
are listed in Table 3. It was found that without the presence of
DMSO, the use of 10 mol% of iodine as a catalyst leads to the
cyclization product in a low yield (16%) (Table 3, entry 1). In
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Table 2 Iodine catalyzed cyclization of primary alcohols with o-aminobenzamides to quinazolinones under the optimum conditionsa
Entry
1
RCH2OH
t1 (h)
t2 (h)
Yieldb (%)
10
5
93
93
95
2
3
10
7
5
5
4
8
5
94
5
6
7
10
10
14
5
6
5
90
87
90
8
14
18
5
4
89
57
9c
10c
11e
18
15
4
6
55
76
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Table 2 (Continued)
Entry
12
RCH2OH
t1 (h)
t2 (h)
Yieldb (%)
83
12
6
13
18
15
8
8
77
51
14ce
15d
15
10
41
a
b
Reaction conditions: 2 (1 mmol), 1 (1.2 mmol), iodine (0.05 mmol, 5 mol%), DMSO (5 mmol) and DMC (1 ml), at 100 uC. Isolated yield
c
d
e
based on substrate 2. Iodine (10 mol%) was used. PTSA (10 mol%) was added as an additive. Under a nitrogen atmosphere.
the presence of 10 mol% of HCl, KI can catalyze the reaction
with DMSO as an oxidant (Table 3, entry 4). In the absence of
HCl or DMSO, no product was detected with KI as a catalyst
(Table 3, entries 2 and 3). The reaction also proceeded well in
the presence of HI and DMSO without I2 or KI (Table 3, entry
5). In a recent article, we have demonstrated that DMSO could
convert HI to I2.15d These results suggest the essential role of
iodine and DMSO for the cyclization step of the present
procedure.
Therefore, a plausible reaction mechanism for the iodine
catalyzed one-pot two-step oxidative system using DMSO as an
oxidant is depicted in Scheme 2. In the first step, the alcohol
was oxidized to the corresponding aldehyde with iodine as the
oxidant (Scheme 2a). The in situ generated aldehyde then
reacted with o-aminobenzamide to form an imine intermedi-
ate. In the presence of iodine, the imine intermediate cyclized
to form a N-iodinated species. Elimination of HI produced the
final product (Scheme 2b). Iodine can be regenerated in both
of the two steps via the oxidation of HI with DMSO as the
oxidant (Scheme 2c).
Table 3 Cyclization of o-aminobenzamide with benzyl aldehyde (step 2)a
Conclusions
In conclusion, a convenient and efficient iodine catalyzed one-
pot two-step oxidative system for the synthesis of quinazoli-
nones from the cyclization of primary alcohols with o-amino-
benzamides using DMSO as the oxidant has been achieved.
The present procedure is not moisture sensitive and is carried
out in a green solvent, DMC, with high product yields.
Moreover, the procedure is suitable for aromatic or alkyl
primary alcohols.
Entry
Catalyst
Acid
Oxidant
DMSO
Yieldb (%)
1
2
3
4
5
I2
16
0
0
93
95
KI
KI
KI
HCl
HCl
HI
DMSO
DMSO
a
Reaction conditions: catalyst (10 mol%), acid (20%, 10 mol%),
b
DMSO (3 equiv.), DMC (2 ml). Yield of isolated product after
column chromatography.
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sources and were used without further purification. Petroleum
ether (PE) refers to the fraction boiling in the 60–90 uC range.
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Polygram SILG/UV 254 plates). Column chromatography was
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Acknowledgements
We are grateful to Nanjing University of Science and
Technology for financial support.
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