Simple, selective, and practical synthesis of 2-substituted 4(3H)-quinazolinones by Yb(OTf)3-catalyzed condensation of 2-aminobenzamide with carboxamides

Article abstract of DOI:10.3987/COM-14-S(K)79

A simple, selective, and practical synthetic method of 4(3H)-quinazolinones is realized by Yb(OTf)₃-catalyzed condensation of 2-aminobenzamide with carboxamides. As the reaction proceeds, NH₃ and H₂O were formed as byproducts; however, Yb(OTf)₃ can operate as an efficient Lewis acid catalyst without deactivation.

Full text of DOI:10.3987/COM-14-S(K)79

HETEROCYCLES, Vol. 90, No. 2, 2015
857
HETEROCYCLES, Vol. 90, No. 2, 2015, pp. 857 - 865. © 2015 The Japan Institute of Heterocyclic Chemistry
Received, 8th July, 2014, Accepted, 26th August, 2014, Published online, 3rd September, 2014
DOI: 10.3987/COM-14-S(K)79
SIMPLE,
-SUBSTITUTED 4(3H)-QUINAZOLINONES BY Yb(OTf)
CONDENSATION OF 2-AMINOBENZAMIDE WITH CARBOXAMIDES
SELECTIVE,
AND
PRACTICAL
SYNTHESIS
OF
2
3
-CATALYZED
1
1
1,2
1,3
Tsutomu Yoshimura, Di Yuanjun, Yu Kimura, Hisatsugu Yamada,
1
,4
1,3
Akio Toshimitsu, and Teruyuki Kondo *
1
Department of Energy and Hydrocarbon Chemistry, Graduate School of
2
Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan.
Research and Educational Unit of Leaders for Integrated Medical System, Center
for the Promotion of Interdisciplinary Education and Research, Kyoto University,
3
Katsura, Nishikyo-ku, Kyoto 615-8510, Japan.
Advanced Biomedical
Engineering Research Unit, Center for the Promotion of Interdisciplinary
Education and Research, Kyoto University, Katsura, Nishikyo-ku, Kyoto
4
6
15-8510, Japan.
Division of Multidisciplinary Chemistry, Institute for
Chemical Research, Kyoto University, Gokanosho, Uji, Kyoto 611-0011, Japan
Abstract – A simple, selective, and practical synthetic method of
4
2
(3H)-quinazolinones is realized by Yb(OTf)
3
-catalyzed condensation of
and H
3
can operate as an efficient Lewis
-aminobenzamide with carboxamides. As the reaction proceeds, NH
3
2
O
were formed as byproducts; however, Yb(OTf)
acid catalyst without deactivation.
4
(3H)-Quinazolinones belong to one of the most important classes of fused heterocyclic compounds with
1
2
3
a wide range of biological activities; e.g., protein tyrosine kinase inhibitor, cholecystokinin inhibitor,
4
5
6
7
8
9
10
antimalarial, antibacterial, antifungal, antiviral, anti-HIV, anticancer, antiinflammatory,
11
12
13
14
antiallergy, anticonvulsant, antihypertensive, and antidiabetic. In addition, the 4(3H)-quinazolinone
15
16
17
nucleus is also the key component of chromophoric, thermochromic, and fluorescent materials.
1
8
Typically, 4(3H)-quinazolinones were prepared on the basis of the Niementowski synthesis by
condensation of anthranilic acid with carbonyl compounds and amines, proceeding via an 2-amidobenz-
1
9
amide intermediate. Nevertheless, this method suffers from multi-step and tedious procedures, costly
-
------------------------------------------------------------------------------------------------------------------------------
th
Dedicated with respect to Professor Isao Kuwajima on the occasion of his 77 birthday

858
HETEROCYCLES, Vol. 90, No. 2, 2015
reagents, and often low yields. To overcome these problems, several new methods for synthesis of
2
0
4
(3H)-quinazolinones have recently been developed, using acids and/or oxidants such as PFPAT,
2
1
22
23
24
25
26
27
3 2 2
NaHSO , DDQ/DMF, I , TBAB, and using metal catalysts such as CuI, CuBr, PAPAT-CuCl ,
2
8
29
30
FeCl
3
·6H
2
O, and Ga(OTf)
3
[OTf = trifluoromethanesulfonate] as well as solid catalysts. Wang and
-catalyzed one-pot synthesis of
(3H)-quinazolinones by condensation of anthranilic acid, anilines, and orthoesters (or formic acid,
coworkers have reported a pioneering study on Yb(OTf)
3
4
2
HCO H) without solvents; however, only 3-substituted 4(3H)-quinazolinones were obtained by this
31
32a
32b
32c
reaction.
In addition, Liu,
Bakavoli,
and Wang
have independently developed the
microwave-assisted Niementowski reaction, and palladium-catalyzed carbonylative synthesis of
3
3
4
(3H)-quinazolinones has also been reported.
We have developed a novel method for synthesis of symmetrically substituted ureas by
3
4
ruthenium-catalyzed condensation reaction of 2 equivalents of aromatic amines with formamide.
We
3
5
have attempted to use this ruthenium-catalyzed reaction to construct N-heterocyclic compounds, and the
reaction of 2-aminobenzamide 1a with formamide 2a was examined, which has two possibilities to give
quinazoline-2,4(1H,3H)-dione (the upper reaction in Scheme 1) and to give 4(3H)-quinazolinone (3a, the
lower reaction in Scheme 1). After many trials, we have found that this reaction offers a simple,
selective, and practical method for catalytic synthesis of 4(3H)-quinazolinones.
O
NH
O
N
H
O
O
[Ru]
NH2
+
O
H
NH2
NH2
NH
1
a
2a
N
3a
Scheme 1. Reaction of 2-aminobenzamide 1a with formamide 2a in the presence of ruthenium catalysts
First, the reaction of 2-aminobenzamide 1a with formamide 2a was carried out in the presence of a
o
catalytic amount of RuCl
2
(PPh
3
)
3
in mesitylene under reflux (bath temp. 165 C) for 6 h to give
4
(3H)-quinazolinone 3a in 24% yield (Table 1). The catalytic activities of several zero- and divalent
6
6 6 2 2 3 2
ruthenium complexes were examined, and [(η -C H )RuCl ] and RuCl ·3H O bearing chloro-ligands
showed the high catalytic activity, while the concomitant use of basic phosphine ligands, such as
n
P(cyclo-C
6
H
11
)
3
and P Bu
3
, drastically decreased the catalytic activity of RuCl
3
·3H
2
O.
Accordingly, we consider that ruthenium chlorides may work as a Lewis acid catalyst in the present
reaction, and the catalytic activities of the representative Lewis acids were examined. As can be readily

HETEROCYCLES, Vol. 90, No. 2, 2015
859
seen from Table 2, anhydrous AlCl
3
, FeCl
3
, and Yb(OTf)
3
as well as NiBr
2
hydrate showed the excellent
catalytic activitiy to give 4(3H)-quinazolinone 3a in quantitative yield. However, YbCl
Yb(OAc) ·4H O showed the moderate catalytic activity to give 3a in 66% and 35% yield, respectively.
Naturally abundant FeCl
3 2
·6H O and
3
2
3
6
3
and water-stable Yb(OTf)
3
were the strong candidate of the catalyst for the
o
present reaction; however, the catalytic activity of FeCl
3
decreased, drastically, below 140 C, while
o
Yb(OTf)
3
showed high catalytic activity above 100 C.
Table 1. Catalytic activity of several ruthenium
complexes for the synthesis of 3a from 1a and 2a
Table 2. Catalytic activity of several Lewis
acids for the synthesis of 3a from 1a and 2a
a
a
a
1a (4.0 mmol), 2a (6.0 mmol), Ru catalyst (0.20
mmol as a Ru atom) in mesitylene (5.0 mL) at
o
1
65 C (bath temp.) for 6 h under an Ar
b
atmosphere. Dtermined by GLC.
a
1
a (4.0 mmol), 2a (6.0 mmol), Lewis acid
o
(0.20 mmol) in mesitylene (5.0 mL) at 165 C
bath temp.) for 6 h under an Ar atmosphere.
(
b
Dtermined by GLC.
Then, catalytic activities of several metal triflates were examined, and the results were summarized in
Table 3. Among metal triflates examined, Yb(OTf) showed the highest catalytic activity, and 0.050
mmol (1.25 mol%) Yb(OTf) was at least required for the success of the present reaction. Mesitylene is
the most suitable solvent for the present reaction, while the yield of 3a decreased, drastically, in diglyme
3a, 11%) and N-methylpiperidine (3a, 11%), due to their strong coordination ability through oxygen and
3
3
(
nitrogen atoms to coordinatively unsaturated and catalytically active cationic ytterbium center (vide
infra).

860
HETEROCYCLES, Vol. 90, No. 2, 2015
Formamide 2a is the most effective C1 source in the Table 3. Catalytic activity of several metal
a
triflates for the synthesis of 3a from 1a and 2a
construction of 4(3H)-quinazolinone 3a, while methyl
2 n
formate 2b or paraformaldehyde, (CH O) 2c, instead
of formamide 2a, gave 3a in 39% and 12% yield,
respectively, even under reflux in mesitylene (bath
o
temp. 165 C). Besides formamide 2a, carboxamides,
such as acetamide 2d, 2-methylpropanamide 2e,
pivalamide 2f, and benzamide 2g, can be used in the
present reaction to give 2-methyl-, 2-isopropyl-,
2
-(tert-butyl)-, and 2-phenyl-4(3H)-quinozolinone (3b
3
7
-
e) in good to high yields (Scheme 2).
a
1
a (4.0 mmol), 2a (6.0 mmol), metal triflate
o
(0.20 mmol) in mesitylene (5.0 mL) at 120 C
b
for 6 h under an Ar atmosphere. Dtermined
by GLC.
3
Scheme 2. Yb(OTf) -Catalyzed synthesis of 4(3H)-quinazolinones 3 from
2-aminobenzamide 1a and carboxamides 2
Condensation of several 2-aminobenzamides (1b-e) with formamide (2a) proceeded, smoothly, by
Yb(OTf) catalyst to give the corresponding 4(3H)-quinazolinones (3f-i) in moderate to high isolated
3
4
0
yields (Table 4). In addition, the related 2-aminonicotinamide (1f) also reacted with 2a under the present
catalytic reaction conditions to give pyrido[2,3-d]pyrimidin-4(3H)-one (3j) in an isolated yield of 55%.

HETEROCYCLES, Vol. 90, No. 2, 2015
861
To investigate the mechanism, quinazoline-
,4(1H,3H)-dione was treated with a
Table 4. Synthesis of 4(3H)-quinazolinones 3f-j by
Yb(OTf) -catalyzed condensation of 2-aminobenzamides
b-e and the related 1f with formamide 2a
3
2
a
1
3
catalytic amount of Yb(OTf) in mesitylene
o
at 120 C for 6 h under an argon
atmosphere in the presence or absence of
formamide 2a. In both reactions, no 3a was
obtained at all (Scheme 3). Thus, the
mechanism through the reduction of a
carbonyl group in quinazolin-2,4(1H,3H)-
dione was ruled out, completely.
Considering the results obtained above, the
most plausible mechanism is illustrated in
Scheme 4. We believe that the dissociation
-
of a triflate anion (OTf ) from Yb(OTf)
3
first occurred to generate catalytically
+
active Yb(OTf)
2
, which immediately
coordinates to a carbonyl oxygen in
carboxamide. Subsequent nucleophilic
attack
of
an
amino
group
in
2
-aminobenzamide to the activated
carbonyl carbon in carboxamide proceeded
to give an amidine intermediate and
a
1
2 3
(4.0 mmol), HCONH 2a (6.0 mmol), Yb(OTf) (0.20
o
mmol) in mesitylene (5.0 mL) at 165 C (bath temp.) for 6 h
under an Ar atmosphere.
2
Yb(OTf) (OH), followed by dissociation of
-
+
+
OH to regenerate Yb(OTf)
2
. Yb(OTf)
2
again coordinates to a carbonyl oxygen in benzamide to
promote the intramolecular nucleophilic attack of an amino group to the activated carbonyl carbon.
3
Isomerization of the intermediate, followed by elimination of NH give 4(3H)-quinazolinone and
+
Yb(OTf)
2
.
3
Scheme 3. Reaction of quinazoline-2,4(1H,3H)-dione with formamide 2a in the presence of Yb(OTf) catalyst

862
HETEROCYCLES, Vol. 90, No. 2, 2015
Scheme 4. The most plausible mechanism
In conclusion, we developed one-pot and environmentally benign synthesis of 2-substituted
(3H)-quinazolinones by Yb(OTf) -catalyzed condensation of 2-aminobenzamides with carboxamides.
4
3
Surprisingly, Yb(OTf)
presence of byproducts, NH
valuable nitrogen-heterocycles is highly expected, and the study is in progress in our laboratory.
3
can operate as an efficient Lewis acid catalyst without deactivation even in the
3
and H O. Accordingly, application of Yb(OTf) catalyst to construct other
2
3

HETEROCYCLES, Vol. 90, No. 2, 2015
863
ACKNOWLEDGEMENTS
T.K. acknowledges financial support from the Asahi Glass Foundation and the Yazaki Memorial
Foundation for Science and Technology. This research was conducted in part at Katsura-Int’tech Center,
Graduate School of Engineering, Kyoto University.
REFERENCES AND NOTES
1
.
For a review, see: (a) D. W. Fry, A. J. Kraker, A. McMichael, L. A. Ambroso, J. M. Nelson, W. R.
Leopold, R. W. Connors, and A. J. Bridges, Science, 1994, 265, 1093; (b) I. Hermecz, J. Kȍkȍsi, B.
Podányi, and G. Szástz, Heterocycles, 1994, 37, 903; (c) J. P. Michael, Nat. Prod. Rep., 2005, 22,
6
27; (d) S. B. Mhaske and P. Argade, Tetrahedron, 2006, 62, 9787.
2
.
.
G. Wagner and I. Wunderlich, Pharmazie, 1978, 33, 15.
3
(a) M. J. Yu, J. R. McCowan, N. R. Mason, J. B. Deeter, and L. G. Mendelsohn, J. Med. Chem.,
1
992, 35, 2534; (b) J. K. Padia, M. Field, J. Hinton, K. Meecham, J. Pablo, R. Pinnock, B. D. Roth,
L. Singh, N. Suman-Chauhan, B. K. Trivedi, and L. Webdale, J. Med. Chem., 1998, 41, 1042; (c) S.
S. Ibrahim, A. M. Abdel-Halim, Y. Gabr, S. El-Edfawy, and R. M. Abdel-Rahman, J. Chem. Res.
Synop., 1997, 154.
4.
5.
6.
Y. Takaya, H. Tasaka, T. Chiba, K. Uwai, M. A. Tanitsu, H. S. Kim, Y. Wataya, M. Miura, M.
Takeshita, and Y. Oshima, J. Med. Chem., 1999, 42, 3163.
P. P. Kung, M. D. Casper, K. L. Cook, L. Wilson-Lingard, L. M. Risen, A. Vickers, R. Ranken, L. B.
Blyn, R. Wyatt, P. D. Cook, and J. Ecker, J. Med. Chem., 1999, 42, 4705.
(a) H. Panwar, S. Singh, A. Kumar, S. Singh, N. Singh, and H. Singh, Der Pharma Chemica, 2011, 3,
3
2
99; (b) X. Wang, P. Li, Z. Li, J. Yin, M. He, W. Xue, Z. Chen, and B. Song, J. Agric. Food Chem.,
013, 61, 9575; (c) W. Pendergast, J. V. Johnson, S. H. Dickerson, I. K. Dey, D. S. Duch, R. Ferone,
W. R. Hall, J. Humphery, J. Kelly, and D. C. Wilson, J. Med. Chem., 1993, 36, 2279; (d) M. M.
Ghorab, M. A. Abdel-Gawad, and M. S. A. El-Gaby, Farmaco, 2000, 55, 249 (CA, 2000, 133,
2
37956).
7.
8.
9.
X. Gao, X. Cai, K. Yan, B. Song, L. Gao, and Z. Chen, Molecules, 2007, 12, 2621.
M. A. Khili, R. Soliman, A. M. Furghuli, and A. A. Bekhit, Arch. Pharm., 1994, 327, 27.
(a) H.-Z. Li, H.-Y. He, Y.-Y. Han, X. Gu, L. He, Q.-R. Qi, Y.-L. Zhao, and L. Yang, Molecules,
2
010, 15, 9473; (b) A. Boumendjel, H. Baubichon-Cortay, D. Trompier, T. Perrotton, and A. D.
Pietro, Med. Res. Rev., 2005, 25, 453.
1
0. (a) V. Alagarsamy, S. V. Raja, and K. Dhanabal, Bioorg. Med. Chem., 2007, 15, 235; (b) V.
Alagarsamy, K. Dhanabai, P. Parthiban, G. Anjana, G. Deepa, B. Murugesan, S. Rajkumar, and A. J.
Beevi, J. Pharm. Pharmacol., 2007, 59, 669.

864
HETEROCYCLES, Vol. 90, No. 2, 2015
1
1. R. A. LeMahieu, M. Carson, W. C. Nason, D. R. Parrish, A. F. Weton, H. W. Baruth, and B.
Yaremko, J. Med. Chem., 1983, 26, 420.
1
2. V. Jatav, P. Mishra, S. Kashaw, and J. P. Stables, Eur. J. Med. Chem., 2008, 43, 135.
3. (a) V. Alagarsamy, Pathak, and S. Urvishbhai, Bioorg. Med. Chem., 2007, 15, 3457; (b) J.-W.
Cherns P.-L. Tao, K.-C. Wang, A, A. Gutcait, S.-W. Liu, M.-H. Yen, S.-L. Chien, and J.-K. Rong, J.
Med. Chem., 1998, 41, 3128.
1
1
1
1
1
1
1
4. M. S. Malamas and J. Millen, J. Med. Chem., 1991, 34, 1492.
5. H. A. Bhatti and S. Seshadri, Color. Technol., 2004, 120, 101.
6. R. G. Patel, M. P. Patel, and R. G. Patel, Dyes and Pigments, 2005, 66, 7.
7. S. P. Anthony, Chem. Asian J., 2012, 7, 374.
8. S. Niementowski, Ber., 1894, 27, 1394.
9. For a review, see: (a) D. J. Connolly, D. Cusack, T. P. O'Sullivan, and P. J. Guiry, Tetrahedron,
2
005, 61, 10153; (b) L. He, H. Li, J. Chen, and X.-F. Wu, RSC Adv., 2014, 4, 12065.
2
2
2
2
2
2
0. J. J. Naleway, C. M. J. Fox, D. Robinhold, E. Terpetsching, N. A. Olsen, and R. P. Haugland,
Tetrahedron Lett., 1994, 35, 8569.
1. S. E. Lopez, M. E. Rosales, N. Urdaneta, M. V. Godoy, and J. E. Charris, J. Chem. Res. Synop.,
2
000, 6, 258.
2. (a) B. A. Bhat and D. P. Sahu, Synth. Commun., 2004, 34, 2169; (b) M. Dabiri, P. Salehi, M.
Bahramnejad, and M. Alizadeh, Monatsh. Chem., 2010, 141, 877.
3. (a) M. Bakavoli, A. Shiri, Z. Ebrahimpour, and M. Rahimizadeh, Chin. Chem. Lett., 2008, 19, 1403;
(
b) S.-L. Wang, K. Yang, C.-S. Yao, and X.-S. Wang, Synth. Commun., 2012, 42, 341.
4. A. Davoodnia, S. Allameh, A. R. Fakhari, and N. Tavakoli-Hoseini, Chin. Chem. Lett., 2010, 21,
50.
5
5. (a) J. Zhou, L. Fu, M. Lv, J. Liu, D. Pei, and K. Ding, Synthesis, 2008, 3974; (b) X. Huang, H. Yang,
H. Fu, R. Qiao, and Y. Zhao, Synthesis, 2009, 2679.
2
2
2
2
3
6. W. Xu and H. Fu, J. Org. Chem., 2011, 76, 3846.
7. N. Montazeri, K. Pourshamsian, S. Yosefiyan, and S. S. Momeni, J. Chem. Sci., 2012, 124, 883.
8. G.-W. Wang, C.-B. Miao, and H. Kang, Bull. Chem. Soc. Jpn., 2006, 79, 1426.
9. J. Chen, D. Wu, F. He, M. Liu, H. Wu, J. Ding, and W. Su, Tetrahedron Lett., 2008, 49, 3814.
0. (a) M. Dabiri, P. Salehi, A. A. Mohammadi, M. Baghbanzadeh, and G. Kozehgiry, J. Chem. Res.,
2
004, 570; (b) M. M. Heravi, S. Sadjadi, S. Sadjadi, H. A. Oskooie, and F. F. Bamoharram, Ultrason.
Sonochem., 2009, 16, 708; (c) T.-H. Niloofar and D. Abolghasem, Chin. J. Chem., 2011, 29, 1685.
1. L. Wang, J. Xia, F. Qin, C. Qian, and J. Sun, Synthesis, 2003, 1241.
3
3
2. (a) J.-F. Liu, J. Lee, A. M. Dalton, G. Bi, L. Yu, C. M. Baldino, E. McElory, and M. Brown,

HETEROCYCLES, Vol. 90, No. 2, 2015
865
Tetrahedron Lett., 2005, 46, 1241; (b) M. Bakavoli, O. Sabzevari, and M. Rahimizadeh, Chin. Chem.
Lett., 2007, 18, 1466; (c) F. Li, Y. Feng, Q. Meng, W. Li, Z. Li, Q. Wang, and F. Tao, ARKIVOC,
2
007, i, 40.
3
3. (a) C. Larksarp and H. Alper, J. Org. Chem., 2000, 65, 2773; (b) L. He, H. Li, H. Neumann, M.
Beller, and X.-F. Wu, Angew. Chem. Int. Ed., 2014, 53, 1420; (c) X. Jiang, T. Tang, J.-M. Wang, Z.
Chen, Y.-M. Zhu, and S.-J. Ji, J. Org. Chem., 2014, 79, 5082.
3
4. T. Kondo, S. Kotachi, Y. Tsuji, Y. Watanabe, and T. Mitsudo, Organometallics, 1997, 16, 2562.
5. (a) M. Akazome, T. Kondo, and Y. Watanabe, J. Org. Chem., 1993, 58, 310; (b) T. Kondo, T. Kanda,
D. Takagi, K. Wada, Y. Kimura, and A. Toshimitsu, Heterocycles, 2012, 86, 1015.
6. For a review, see: (a) S. Kobayashi, Synlett, 1994, 689; (b) T. Kitanosonoa and S. Kobayashi, Adv.
Synth. Catal., 2013, 355, 3095.
3
3
3
7. A mixture of 2-aminobenzamide (1, 4.0 mmol), carboxamide (2, 6.0 mmol), Yb(OTf)
3
(0.20 mmol,
5
.0 mol%), and mesitylene (5.0 mL) was placed in a 20-mL Pyrex flask equipped with a magnetic
o
stirring bar and a reflux condenser under a flow of argon. The reaction was carried out at 120-165 C
bath temp.) for 6 h with stirring. Then, the reaction mixture was cooled to room temperature, and
(
analyzed by GLC, GC-MS (EI), and LC-MS (ESI). After evaporation of mesitylene under vacuum,
the products (3) were isolated by recrystallization from MeOH/hexane and/or medium pressure
column chromatography on silica gel (eluent: EtOAc/hexane = 50/50 ~ EtOAc 100%. For 3j, eluent:
1
13
MeOH/CHCl
3
= 50/50). H NMR spectra were recorded at 400 MHz, and C NMR spectra were
3
8
39
40
41
recorded at 100 MHz in DMSO-d
6
. The analytical and spectral data of 3a-e, 3f, 3g, 3h, and
4
2
43
3
j, were consistent with those reported previously. The product, 3i, was characterized below.
3
3
4
4
8. D. J. Connolly, P. M. Lacey, M. McCarthy, C. P. Saunders, A.-M. Carroll, R. Goddard, and P. J.
Guiry, J. Org. Chem., 2004, 69, 6572.
9. S. K. Kundu, M. P. D. Mahindaratne, M. V. Quintero, A. Bao, and G. R. Negrete, ARKIVOC, 2008,
ii, 33.
0. A. A. Layeva, E. V. Nosova, G. N. Lipunova, T. V. Trashakhova, and V. N. Charushin, Russ. Chem.
Bull., Int. Ed., 2007, 56, 1821.
1. L. Ȍrfi, F. Wáczek, J. Pató, I. Varga, B. Hegymegi-Barakonyi, R. A. Houghten, and G. Kéri, Curr.
Med. Chem., 2004, 11, 2549.
4
2. A. Srinivasan, P. E. Fagerness, and A. D. Broom, J. Org. Chem., 1978, 43, 828.
-1
1
4
3. 3i: a white solid. IR (KBr) cm : 3127, 1698; H NMR (DMSO-d
6
, 400 MHz) δ: 12.16 (1H, br s),
8
.00 (1H, s), 7.61 (1H, d, J = 8.98 Hz), 7.49 (1H, d, J = 2.86 Hz), 7.42 (1H, dd, J = 8.98 and 2.86
13
Hz), 3.86 (3H, s); C NMR (DMSO-d
6
, 100 MHz) δ: 160.4, 157.7, 143.2, 142.8, 128.7, 123.7, 123.4,
+
1
05.8, 55.6; MS (ESI): 177.0726 (M+H) .