An efficient solvent free multicomponent synthesis of functionalized 4H-chromenes by using reusable, heterogeneous Amberlite IRA-400 Cl resin as catalyst

Article abstract of DOI:10.1016/j.tetlet.2014.11.043

A simple and efficient Amberlite IRA-400 Cl resin catalyzed multicomponent reaction of 2-hydroxy-1-naphthaldehyde, 1,3-diketone, and nucleophile under solvent free condition to obtain the biological important 4H-chromene derivatives has been outlined. Significant features of this method are the simplicity of the procedure, the ready accessibility, and cost effectiveness of the catalyst, and higher yields in a relatively short reaction time. Structures of compounds 4j and 5c were confirmed from single crystal X-ray studies.

Full text of DOI:10.1016/j.tetlet.2014.11.043

Accepted Manuscript
An efficient solvent free multicomponent synthesis of functionalized 4H-chro-
menes by using reusable, heterogeneous Amberlite IRA-400 Cl resin as catalyst
Gurusamy Harichandran, Parkunan Parameswari, Madasamy Kanagaraj,
Ponnusamy Shanmugam
PII:
S0040-4039(14)01936-4
DOI:
http://dx.doi.org/10.1016/j.tetlet.2014.11.043
TETL 45427
Reference:
Tetrahedron Letters
To appear in:
Received Date:
Revised Date:
Accepted Date:
20 August 2014
5 November 2014
11 November 2014
Please cite this article as: Harichandran, G., Parameswari, P., Kanagaraj, M., Shanmugam, P., An efficient solvent
free multicomponent synthesis of functionalized 4H-chromenes by using reusable, heterogeneous Amberlite
IRA-400 Cl resin as catalyst, Tetrahedron Letters (2014), doi: http://dx.doi.org/10.1016/j.tetlet.2014.11.043
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers
we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and
review of the resulting proof before it is published in its final form. Please note that during the production process
errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Graphical Abstract
To create your abstract, type over the instructions in the template box below.
Fonts or abstract dimensions should not be changed or altered.
An efficient solvent free multicomponent synthesis of
functionalized 4H-chromenes by using reusable,
heterogeneous Amberlite IRA 400-Cl resin as catalyst
Leave this area blank for abstract info.
Gurusamy Harichandran*a, Parkunan Parameswaria, Madasamy Kanagaraja and Ponnusamy Shanmugamb
OH
O
O
NuH
O
Nu
CHO
OH
3(a-f)
IRA-400 Cl
Solvent free,
100 oC
OH
O
O
O
O
Nu
Nu
2(a-d)
1
5 (a-c)
6(a-c)
4(a-n)

1
Tetrahedron Letters
journal homepage: www.elsevier.com
An efficient solvent free multicomponent synthesis of functionalized 4H-chromenes
by using reusable, heterogeneous Amberlite IRA-400 Cl resin as catalyst
Gurusamy Harichandran*a, Parkunan Parameswaria, Madasamy Kanagaraja and Ponnusamy Shanmugamb
a Department of Polymer Science, University of Madras, Guindy Campus, Chennai-600 025, India; bOrganic Chemistry Division, CSIR-Central Leather
Research Institute(CLRI), Adyar, Chennai-600 020, India
ARTICLE INFO
ABSTRACT
Article history:
Received
Received in revised form
Accepted
A simple and efficient Amberlite IRA-400 Cl resin catalyzed multicomponent reaction of 2-
hydroxy-1-naphthaldehyde, 1,3-diketone and nucleophile under solvent free condition to obtain
the biological important 4H-chromene derivatives has been outlined. Significant feature of this
method are the simplicity of the procedure, the ready accessibility and cost effectiveness of the
catalyst, and higher yields in a relatively short reaction times. The structure of compounds 4j
and 5c were confirmed from single crystal X-ray studies.
Available online
Keywords:
2014 Elsevier Ltd. All rights reserved.
Amberlite IRA-400 Cl resin
Multicomponent reactions
Solvent free condition
4H-Chromene
Michael reaction
Amberlite IRA-400 Cl is an heterogeneous anionic base catalyst
used for a number of synthetic organic transformations.1,2 Main
advantage of the Amberlite IRA-400 Cl anionic base catalyst is
that it does not lead to any side reactions. Xanthene and its
derivatives are important classes of heterocyclic compounds
widely distributed in many natural occurring compounds, used as
Leuco dyes in laser technology3 and pH sensitive fluorescent
materials for visualization of biomolecules.4 Moreover, xanthene
derivatives also exhibit a wide spectrum of bioactivities such as
OH
O
O
NuH
3(a-f)
IRA-400 Cl
O
Nu
CHO
OH
OH
Nu
O
O
O
O
Solvent free,
Nu
6(a-c)
100 o
C
2(a-d)
1
4(a-n)
5 (a-c)
Scheme 1
antiviral, antiallergic5 anti-inflammatory, spasmolytic, diuretic,
9
anticoagulant, antibacterial,6-8 antifungal
and anticancer10
Initially, to synthesizes compound 4a via Knoevenagel-
Michael addition-cyclization cascade process, a reaction of 2-
hydroxy-1-naphthaldehyde 1 (1.0 mmol), dimedone 2a (1.0
mmol) and indole 3a (1.0 mmol) at 100 °C under solvent- and
catalyst-free condition was carried out and the reaction afforded a
major product of 4a in 55% yield along with a minor product 5a
in 35% yield (Table 1, entry 1). Repeating the above experiment
with Amberlite IR-120 resin (0.5 g, 20-30 mesh size, 1.5 mmol of
H+ resin), the yield of the product 4a substantially improved to
72% (Table 1, entry 2) and compound 5a in 18% yields.
However, when Amberlite IRA-400 Cl resin (0.5 g, 16-50 mesh
size, 1.5 mmol of chloride resin) was added to the above mixture,
an excellent improvement in the product yield of 4a in 86%
accompanied by the formation of compound 5a only in 5% yield
(Table 1, entry 3), at the same instant, duration of the reaction
was reduced to 1.5 h. On the other hand, the reaction was
monitored with different equivalents of Amberlite IRA-400 Cl
catalyst- under solvent-free conditions at 100 °C provided the
desired compound 4a in varied yields and the results are
summarized in Table 1. (Entries 3-8) It has been found that 0.2 g
of Amberlite IRA-400 Cl is the optimum amount of catalyst
required for the completion of the reaction. (Table 1, entry 6)
Decreasing the amount of catalyst from 0.5 to 0.1 g lowered the
substrate conversion rate (Table 1, entries 3 and 7). However,
agents. Extensive studies has been devoted for the synthesis of 3-
substituted indoles and chromenes since they are widely
distributed in many natural products,11 as pharmacophores12 and
significant biological applications particularly, 5-HT1B/1D
receptor agonist activities used in the treatment of migraine13,
aromatase inhibitor for breast cancer,14 and HIV-1 integrase
inhibitors.15 Only a few multi-component reactions (MCR’s)
have been developed for the synthesis of 3-substituted indoles16
and chromenes.17-19Although chromenes have been synthesized
by distinct methods, they suffers from many drawbacks like use
of harmful chemicals and solvents, extended reaction time, lower
yields and complex workup procedure. To the best of our
knowledge, the synthesis of 4H-chromenes from 2-hydroxy-1-
naphthaldehyde, carbon or nitrogen nucleophile and active
methylenes under solvent-free condition has not previously been
reported. Therefore, there is a need for efficient solid supported
and eco-friendly protocol to obtain these valuable compounds.
Thus, herein we report the preliminary results obtained on a
facile and efficient one-pot synthesis of functionalized 4H-
chromene
derivatives
involving
a
three-component
Knoevenagel–Michael-reaction catalyzed by Amberlite IRA-400
Cl resin under neat MCR (Scheme 1).

2
when the reaction temperature was increased to 120 ºC, the yield
of compound 4a lowered to 82% (Table 1, entry 8) Therefore, the
reaction -performed with the 0.2 g of Amberlite IRA-400 Cl
resin, at 100 °C under solvent- free was found as the optimum
condition (Table 1, entry 6).
Table-2 Synthesis of 4H-chromene derivatives catalyzed by
Amberlite IRA-400 Cl resin.22
O
O
O
OH
NH
O
O
N
H
O
N
O
O
O
2a
2b
2d
2c
Table-1 Optimization conditions for the synthesis of 4a/5aa
O
O
Br
OH
N
N
N
N
H
N
N
H
H
H
3a
3b
3c
3e
3d
3f
O
O
O
HN
N
O
HN
HN
Br
O
O
O
O
4d
4c
Entry
1
Amberlite IRA-
400 Cl resin
(mg)
Temp
(0 C)
Time
(hr)
Yield
of 4a
(%)c
Yield
of 5a
(%)c
4b
mmol
of
resin
-
4a
O
OH
O
O
O
O
O
O
N
N
N
HN
HO
O
O
O
O
O
-
100
4
55
35
2
3
4
5
500b
500
400
300
1.5b
1.5
1.2
0.9
100
100
100
100
2
72
86
86
86
18
5
4h
4g
4e
4f
H
1.5
1.5
1.5
O
O
O
O
N
O
O
HN
O
N
HN
5
NH
Br
HO
O
5
O
O
O
6
200
0.6
100
1.5
86
5
4i
4j
4l
HO
4k
H
H
N
7
8
100
200
0.3
0.6
100
120
1.5
1.5
78
82
15
15
HO
O
N
O
O
HN
N
O
O
NH
NH
O
O
O
O
O
O
a
4m
4n
1.0 mmol of each reactants and reaction was performed under solvent free
5a
5b
condition at 100 ºC; Amberlite IR 120 resin was used, mmol of H+ resin,
cIsolated yield
b
OH
OH
OH
O
O
OH
O
O
N
N
N
Encouraged by the preliminary results and in order to
demonstrate the method as general, a number of nucleophiles
3(a-f) (1.0 mmol) were reacted with 2-hydroxy-1-naphthaldehyde
1 (1.0 mmol) and 1,3-dicarbonyl compounds 2(a-d). Under
optimized condition, all the reactions underwent smoothly and
provided the desired compounds (4a-4n) in excellent yields (55-
93%) with less amount of 5a-b (~5-17%), and the results are
summarized in Table 2.
H
H
N
N
N
O
H
6a
H
6b
6c
5c
Entry
1,3 diones
NuH
Time (hr)
Product(s),
yield (%)
1
2a
2a
2a
2a
2a
2a
2a
2a
2b
2b
2b
2b
2b
2c
2d
2d
2d
3a
3b
3c
3d
3e
2c
3g
2a
2b
3a
3b
3d
2c
2c
3a
3c
3d
1.5
1.5
1.5
1.5
1.5
2.0
2.0
1.5
1.5
2.0
2.0
2.0
2.0
1.5
2.5
2.5
2.5
4a (86)
4b (83)
4c (88)
4d (85)
4e (93)
4f (80)
4g (80)
-
5a (11)
2
5a(14)
5a (10)
5a (12)
5a (5)
3
From the experimental results, it has been observed that both
electron withdrawing and donating substituents in indole
nucleophiles such as 5-bromo-indole 3b, 2-methyl-indole 3c and
1-methylindole 3d did not alter the yields significantly. Best
yield (93%) was obtained while using benzotriazole 3e as a
nucleophile (Table 2, entry 5). However, while using
nucleophiles like 2-hydroxy-1,4-naphthaquinone 3f and 4-
hydroxycoumarin 2c afforded excellent yield of compound 4g,
4f, and 4k (Table 2, entries 6, 7 and 13). Similarly, reaction with
4
5
6
5a (16)
5a (17)
5a (96)
5b (95)
5b (13)
5b (16)
5b (15)
5b (17)
5c (85)
6a (34)
6b (27)
6c (40)
7
8
9
-
10
11
12
13
14
15
16
17
4h (84)
4i (81)
4j (81)
4k (80)
-
1
and dimedone 2a or 1,3-cyclohexanedione 2b or 4-
hydroxycoumarin 2c [1:2 ratio (one equivalent to act as
nucleophile)] afforded 5a (96%), 5b (95%) and 5c (85%) in
excellent yields (Table 2 entries 8, 9 and 14, Scheme 2).
Significantly, the reaction of 1, barbituric acid 2d and indole
derivatives (3a, c-d), the expected 4H-chromene derivatives (4l-
n) was obtained in moderate to good yields (Table 2, entries 15-
17) and bis (indolyl) methane (6a-c) (28-40%) as a minor
products. All the new compounds were characterized by
4l (63)
4m (70)
4n (55)
1
spectroscopic data (IR, H NMR, 13C NMR and HRMS). Final
structure proof of compounds 4j and 5c was obtained from single
crystal X-ray studies (See SI). 20,21
To explore the versatility of the reaction, experiments with
other active methylene compounds 2(a,b), 2-hydroxy-1-
naphthaldehyde 1 and various nucleophile such as α-naphthol 3g,
β-naphthol 3h, N,N’-dimethylaniline 3i, N-tosyl-indole 3j and
3-methyl-1H-pyrazole-5(4H)-one 3k in 1:1:1 ratio at 100˚C have
been carried out (Scheme 2, Table 3). The reaction afforded only

3
compounds 5a and 5b as major products with quantitative
amount of unreacted nucleophiles 3g-k. The reasons were due to
(i) α- and β- naphthols are less reactive compared to enolic
hydroxyl group of diketones and (ii) both electron withdrawing
(tosyl) and electron donating (N,N’-dimethyl) substituents
obstruct the reactivity of nucleophiles.
Acknowledgments
GH thanks University of Madras for providing infrastructure
facilities. Thanks are due to Director, CSIR-CLRI, SAIF-IITM
for NMR and single crystal measurements, respectively.
Supplementary Material
Detailed experimental procedure, characterization of the
products and copies of spectra are provided.
References and notes
1. Akelah, A.; Sherrington, D. C. Chem. Rev. 1981, 81, 557; (b)
Kunian, R. In Ion Exchange Resins, 2nd ed. John Wiley &
Sons: New York, 1958.
Scheme 2
Table-3 Synthesis of tetrahydro-1H-xanthen-1-ones 5 catalyzed
2. Khodaei, M. M.; Bahrami, K.; Farrokhi, A. Synth. Commun.
2010, 40, 1492; (b) Chaturvedi, D.; Mishra, N.; Mishra, V. J.
Sulfur Chem. 2007, 28, 607; (C) Harichandran, G.; David
Amalraj, S.; Shanmugam, P. J. Heterocycl. Chem. 2013, 50,
539.
3. Menchen, S. M.; Benson, S. C.; Lam, J. Y. L.; Zhen, W.; Sun,
D.; Rosenblum, B. B.; Khan, S. H.; Taing, M. Chem. Abstr.
2003, 139, 54287f.
4. Sarma, R. J.; Baruah, J. B. Dyes Pigments. 2005, 64, 91.
5. Zonouzia, A.; Mirzazadeha, R.; Safavi, M.; Ardestanic, S. K.;
Emamid, S. A.; Foroumadi. Iran. J. Pharm. Res. 2013, 12, 679.
6. Hideo, T. Chem. Abstr. 1981, 95, 80922b, Jpn. Tokkyo Koho J.
P. 56005480, 1981.
7. Kumar, R. R.; Perumal, S.; Senthilkumar, P.; Yogeswari, P.;
Sriram, D. Bioorg. Med. Chem. Lett. 2007, 17, 6459.
8. Kidwai, M.; Saxena, S.; Khanb, M. K. R.; Thukral, S. S.
Bioorg. Med. Chem. Lett. 2005, 15, 4295.
9. Wen, L.; Zhang, H.; Lin, H.; Shen, Q.; Lu, L. J. Fluorine Chem.
2012, 133, 171.
10. Mahmoodi, M.; Aliabadi, A.; Emami, S.; Safavi, M.;
Rajabalian, S.; Mohagheghi, M. A.; Khoshzaban, A.; Kermani,
A. S.; Lamei, N.; Shafiee, A.; Foroumadi, A. Arch. Pharm.
Chem. Life Sci. 2010, 343, 411.
11. (a) Jiang, B.; Yang, C.-G; Wang, J. J. Org. Chem. 2001, 66,
4865; (b) Zhang, H.; Larock, R. C. Org. Lett. 2001, 3, 3083; (c)
Sakagami, M.; Muratake, H.; Natsume, M. Chem. Pharm. Bull.
1994, 42, 1393; (d) Fukuyama, T.; Chen, X. J. Am. Chem. Soc.
1994, 116, 3125.
12. (a) Sundberg, R. J. Indoles; Academic Press: San Diego, 1996;
(b) Sundberg, R. J. The Chemistry of Indoles; Academic Press:
New York, 1970.
by Amberlite IRA-400 Cl resin.
Entry
1,3-diones
NuH
Product
Yield a, b (%)
42
1
2a
5a
3g
3h
2
3
2a
2a
5a
5a
44
41
40
3i
3j
4
5
6
2a
2a
5a
5a
40
3k
3h
2b
2b
5b
5b
42
43
7
3i
a
1.0 mmol of each reactants and reaction was performed under solvent free
condition at 100 ºC; b All the reaction were carried out for 0.5h
A plausible mechanism for the formation of compound 4 is
outlined in Scheme 3. Initially, Amberlite resin catalyzes the
Knoevenagel-condensation reaction between 2-hydroxy-1-
naphthaldehyde 1 and active methylene compound 2 to afford
Knoevenagel type intermediate I. In the second step, Michael
addition of indole 3a to Knoevenagel adduct I followed by
dehydration paving the way for its ring closure to afford the 4H-
chromene product 4. On the other hand, there is possibility of
reaction of diketone 2 with Knoevenagel adduct I followed by
dehydration to afforded the tetrahydro-1H-xanthen-1-one product
5.
13. (a) Faulkner, D. J. Nat. Prod. Rep. 1999, 16, 155; (b)
Lounasmaa, M.; Tolvanen, A. Nat. Prod. Rep. 2000, 17, 175.
14. (a) Leze, M. P.; Le Borgne, M.; Marchand, P.; Loquet, D.;
Kogler, M.; Le Baut, G.; Palusczak, A.; Hartmann, R.W. J.
Enzyme Inhib. Med. Chem. 2004, 19, 549; (b) Le Borgne, M.;
Marchand, P.; Delevoye-Seiller, B.; Robert, J. M.; Le Baut, G.;
Hartmann, R.W.; Palzer, M. Bioorg. Med. Chem. Lett. 1999, 9,
333.
15. (a) Deng, J.; Sanchez, T.; Neamati, N.; Briggs, J. M. J. Med.
Chem. 2006, 49, 1684; (b) Contractor, R.; Samudio, I. J.;
Estrov, Z.; Harris, D.; McCubrey, J. A.; Safe, S. H.; Andreeff,
M.; Konopleva, M. Cancer Res. 2005, 65, 2890.
In summary, we have demonstrated a facile and efficient
Knoevenagel condensation and Michael addition reaction for the
synthesis of 4H-chromenes. The advantages of this protocol are
resuced reaction time, isolation of final products by simple
filtration due to different solubility of products and starting
materials. Further work using Amberlite IRA-400 Cl catalyst in
organic synthesis is under investigation in this laboratory.

4
PS
H
O
O
O
O
O
O
H
O
-H2O
O
IRA-400Cl
CH
PS
O
OH
OH
O
2
1
PS
HN
HN
HN
O
N
O
O
O
H
-H2O
3a
H
O
H
OH
O
4
O
OH OH
I
O
O
O
O
HO
HO
O
O
HO
O
O
PS
= Polymer supported
H
O
-H2O
O
OH
PS
OH OH
5
Scheme 3. A plausible mechanism for the formation of compounds 4 and 5
126.79, 128.14, 128.34, 128.58, 131.49, 131.81, 136.98, 147.67,
165.45, 197.44; HRMS m/z (ESI) calcd for C26H21NO2
[M+Na]+ 402.4401; found 402.1466. 5a: White crystalline solid;
m.p = 228-230 °C; FT-IR (KBr) νmax: 470, 583, 812, 1011,
1233, 1260, 1371, 1592, 1643, 2944, 3176 cm−1; 1H NMR (400
MHz, DMSO-d6) δH: 0.78 (s, 6H, (CH3)2), 0.98 (s, 3H, CH3),
1.08 (s, 3H, CH3), 2.04-2.08 (m, 4H), 2.29-2.42 (m, 3H), 2.64
(d, 1H, J = 17.2 Hz), 5.56 (s, 1H, CH), 7.22 (d, 1H, J = 8.8 Hz,
ArH), 7.37-7.45 (m, 2H, ArH), 7.79 (dd, 2H, J = 8.8 Hz, J = 7.6
Hz, ArH), 8.20 (d, 1H, J = 6.8 Hz, ArH), 10.47 (br, 1H, OH);
13C NMR (100 MHz, DMSO-d6) δC: 26.30, 29.80, 31.90, 32.18,
40.93, 51.04, 111.11, 117.16, 117.79, 124.82, 126.82, 128.15,
128.67, 130,98, 132.02, 148.46, 196.50; HRMS m/z (ESI)
calcd for C27H28O4 [M+Na]+ 439.4985; found 439.1886. 5c:
16. Ravindran, A.; Kore, R.; Srivastava, R. Indian J. Chem. Sec.
B. 2013, 52, 129-135.
17. Li, M.; Zhanga, B.; Gu, Y. Green Chem. 2012, 14, 2421.
18. Ganguly, N. C.; Roy, S.; Mondal, P.; Saha, R. Tetrahedron Lett.
2012, 53, 7067.
19. Ghosh, P. P.; Das, A. R. J. Org. Chem. 2013, 78, 6170.
20. CCDC 976014 [4j] contains the supplementary crystallographic
data. These data can be obtained free of charge from The
Cambridge
Crystallographic
Data
Centre
via
www.ccdc.cam.ac.uk/data_request/cif.
21. CCDC 976013 [5c] contains the supplementary crystallographic
data. These data can be obtained free of charge from The
Cambridge
Crystallographic
Data
Centre
via
www.ccdc.cam.ac.uk/data_request/cif.
Brown crystalline solid; m.p = 200-202 °C; FT-IR (KBr) νmax
:
22. General procedure: A mixture of 2-hydroxy-1-naphthaldehyde
1 (1.0 mmol), 1,3-dione 2 (a-d) (1.0 mmol), nucleophile 3 (a-f)
(1.0 mmol) and anion exchange resin (Cl in form) (0.2 g) under
solvent- free condition at 100 °C for the time shown in Table 2
was performed. After completion of the reaction (as indicated
by TLC), the reaction mixture was cooled and dissolved in 10
mL of ethyl acetate followed by filtration of the catalyst. The
solvent was evaporated under vacuum and the crude mixture
was purified by column chromatography on silica gel (ethyl
acetate/petroleum ether 1:4) as eluent to afford pure products 4.
Spectroscopy data for selected compounds: 4j White crystalline
solid; m.p = 230-232 °C; FT-IR (KBr) νmax: 465, 741, 817,
1185, 1222, 1370, 1594, 1640, 2930 cm−1; 1H NMR (400 MHz,
DMSO-d6) δH: 1.87-1.98 (m, 2H), 2.27-2.39 (m, 2H), 2.25-2.73
(m, 2H), 3.56 (s, 3H, CH3), 5.99 (s, 1H, CH), 6.94-6.98 (m, 2H,
ArH), 7.04-7.11 (m, 2H, ArH), 7.26-7.36 (m, 3H, ArH), 7.55 (d,
1H, J = 8.0 Hz, ArH), 7.70 (d, 2H, J = 8.4 Hz, ArH), 8.09 (d,
1H, J = 8.0 Hz, ArH); 13C NMR (100 MHz, DMSO-d6) δC:
20.33, 26.26, 27.69, 32.66, 37.13, 109.13, 115.13, 116.93,
117.85, 118.16, 118.94, 119.61, 121.06, 123.77, 124.77, 126.51,
515, 744, 742, 811, 1214, 1456, 1595, 1645, 1704, 2925 cm−1;
1H NMR (400 MHz, DMSO-d6) δH: 6.59 (s, 1H, CH), 6.73 (d,
2H, J = 10.0 Hz, ArH), 6.84 (t, 3H, J = 6.2 Hz, ArH), 7.10-7.18
(m, 5H, ArH), 7.66 (d, 1H, J = 6.8 Hz, ArH) 7.72 (d, 1H, J = 6
Hz, ArH), 7.99 (d, 1H, J = 6.8 Hz, ArH), 9.09 (br, 1H, OH),
10.62 (s, 2H, NH); 13C NMR (100 MHz, DMSO-d6) δC: 31.73,
110.17, 111.46, 117.84, 118.29, 118.56, 119.44, 120.55, 121.91,
124.05, 125.41, 127.97, 128.40, 128.4, 128.74, 132.14, 134.02,
134.85, 152.93. 6a: Brown crystalline solid; m.p = 200-202 °C;
FT-IR (KBr) νmax: 515, 744, 742, 811, 1214, 1456, 1595, 1645,
1
1704, 2925 cm−1; H NMR (400 MHz, DMSO-d6) δH: 6.59 (s,
1H, CH), 6.73 (d, 2H, J = 10.0 Hz, ArH), 6.84 (t, 3H, J = 6.2
Hz, ArH), 7.10-7.18 (m, 5H, ArH), 7.66 (d, 1H, J = 6.8 Hz,
ArH) 7.72 (d, 1H, J = 6 Hz, ArH), 7.99 (d, 1H, J = 6.8 Hz,
ArH), 9.09 (br, 1H, OH), 10.62 (s, 2H, NH); 13C NMR (100
MHz, DMSO-d6) δC: 31.73, 110.17, 111.46, 117.84, 118.29,
118.56, 119.44, 120.55, 121.91, 124.05, 125.41, 127.97, 128.40,
128.4, 128.74, 132.14, 134.02, 134.85, 152.93.