Selective Synthesis of New Tetracyclic Coumarin-fused Pyrazolo[3,4-b]pyridines and Pyrazolo[3,4-b]pyridin-6(7H)-ones

Article abstract of DOI:10.1002/jhet.2473

A three-component reaction for the synthesis of new coumarin-fused tetracyclic system from 4-hydroxycoumarin, aldehydes, and 5-aminopyrazoles/5-aminoisoxazole is described. In the presence of acetic acid, 4,7-dihydro-1H-pyrazolo[3,4-b]pyridines (4) and pyrazolo[3,4-b]pyridines (5) were obtained in acetonitrile and dimethylsulfoxide medium, respectively. The reaction gave rise to 4,5-dihydro-1H-pyrazolo[3,4-b]pyridin-6(7H)-ones (6) in acetic acid–ethanol combination system, which involved the C–O bond cleavage. 4-Hydroxy-6-methyl-2H-pyran-2-one and acenaphthylene-1,2-dione were also examined, affording the corresponding C–O bond cleavage products. Mechanism indicates that the reaction is reversible in acetic acid–ethanol combination system.

Full text of DOI:10.1002/jhet.2473

Month 2015
Selective Synthesis of New Tetracyclic Coumarin-fused Pyrazolo
[3,4-b]pyridines and Pyrazolo[3,4-b]pyridin-6(7H)-ones
*
Meilin Liu, Guodong Yin, Can Zhu, and Chaochao Yao
Hubei Collaborative Innovation Center for Rare Metal Chemistry, Hubei Key Laboratory of Pollutant Analysis and Reuse
Technology, Hubei Normal University, Huangshi 435002, China
*
E-mail: gdyin_hbnu@163.com
Additional Supporting Information may be found in the online version of this article.
Received February 3, 2015
DOI 10.1002/jhet.2473
Published online 00 Month 2015 in Wiley Online Library (wileyonlinelibrary.com).
A three-component reaction for the synthesis of new coumarin-fused tetracyclic system from 4-hydroxycoumarin,
aldehydes, and 5-aminopyrazoles/5-aminoisoxazole is described. In the presence of acetic acid, 4,7-dihydro-
1H-pyrazolo[3,4-b]pyridines (4) and pyrazolo[3,4-b]pyridines (5) were obtained in acetonitrile and
dimethylsulfoxide medium, respectively. The reaction gave rise to 4,5-dihydro-1H-pyrazolo[3,4-b]pyridin-
6(7H)-ones (6) in acetic acid–ethanol combination system, which involved the C–O bond cleavage.
4-Hydroxy-6-methyl-2H-pyran-2-one and acenaphthylene-1,2-dione were also examined, affording the
corresponding C–O bond cleavage products. Mechanism indicates that the reaction is reversible in acetic
acid–ethanol combination system.
J. Heterocyclic Chem., 00, 00 (2015).
INTRODUCTION
oxo-2H-chromene-4-carbaldehyde and 5-aminopyrazoles
under microwave irradiation [14]. Wang described the reac-
tion to prepare tetracyclic pyrazolo[3,4-b]pyridine-based
coumarin chromophores from 3-acetyl coumarin deriva-
tives and 5-aminopyrazoles. They also found that these
polycyclic compounds exhibited high fluorescence
quantum yields and good electrochemical, thermal, and
photochemical stabilities [15]. Ji and coworkers illustrated
an example for the synthesis of 8-carboxylnaphthyl-
functionalized pyrazolo[3,4-b]pyridine involving the C–C
bond cleavage reaction [16]. Recently, it was found
that iodine and n-tetrabutylammonium tribromide could
catalyze synthesis of dihydrochromeno[4,3-b]pyrazolo[4,3-e]
pyridin-6(7H)-ones involving three-component reaction of
aromatic aldehydes, 4-hydroxycoumarin, and 3-aminopyrazoles,
respectively [17,18]. However, the aliphatic aldehydes
show the poor yields of the expected products. In continua-
tion with our previous work [19] in minimizing the efforts
in construction of coumarin-fused heterocyclic frame-
works, we herein report a solvent-tunable selective synthe-
sis of new tetracyclic system by the three-component
reactions of 4-hydroxycoumarin (1), aldehydes (2), and
5-aminopyrazoles (3). Coumarin-fused 4,7-dihydro-1H-
pyrazolo[3,4-b]pyridines were obtained in refluxing
Ever-increasing attention has been paid in recent years
to the functionalized pyrazolo[3,4-b]pyridines [1], which
are widely present in numerous natural products and
biologically active molecules [2]. For example, anxio-
lytic drugs cartazolate, etazolate, and tracazolate are
pyrazolo[3,4-b]pyridine derivatives [3]. In addition,
coumarin chemistry has captured the continuous
attention of chemists and pharmacists for their biologi-
cal activities [4]. Many synthetic drugs, warfarin,
phenprocoumon, and brodifacoum, contain coumarin
fragment [5].
The development of new multicomponent reactions has
become an active and challenging topic in modern
synthetic chemistry because it is a preferred approach to
design and discover biologically active compounds [6,7].
Literature survey a variety of functionalized polycyclic
pyrazolo[3,4-b]pyridine derivatives that have been
reported [8–12]. However, several routes have thus far
been reported for the construction of coumarin-fused
pyrazolo[3,4-b]pyridines [13]. Boruah and coworkers
reported the synthesis of coumarin-fused pyrazolo[3,4-b]
pyridines via a palladium-catalyzed reaction of 3-bromo-2-
© 2015 HeteroCorporation

M. Liu, G. Yin, C. Zhu, and C. Yao
Vol 000
acetonitrile in the presence of acetic acid. When acetonitrile
was replaced by dimethylsulfoxide, the reactions gave the
corresponding aromatization products tetracyclic pyrazolo
[3,4-b]pyridines. Moreover, C–O bond cleavage products
4,5-dihydro-1H-pyrazolo[3,4-b]pyridin-6(7H)-ones were ob-
tained when the reactions were carried out in acetic acid–
ethanol combination system.
and pyridine) also furnished 4j–4l in 78–82% yields.
Aliphatic aldehyde (R1¼Me) gave a slightly low yield with
isolation of 4m in 55% yield. Note that 3-methylisoxazol-
5-amine (3b) was also suitable for this transformation to
afford 4n in 76% yield.
Then, the acetic acid–dimethylsulfoxide combination
was employed for the synthesis of 5. As shown in
Scheme 2, it was found that the representative alde-
hydes in which R1 is a phenyl ring bearing methyl,
methoxy, and nitro substituents could smoothly react
with 1 and 3a to give the corresponding products
5b–5e in 80–87% yields. 2-Thienylaldehyde and acetal-
dehyde also furnished 5f and 5g in 90% and 78%
yields, respectively.
When the mixture of 1, 2a, and 3a was heated in acetic
acid–ethanol (1:20) for 30min, an unexpected insoluble
white solid was obtained in 74% yield, which was identi-
fied as the C–O bond cleavage product 6a and further
clarified by X-ray single-crystal diffraction analysis
(Fig. 1) [21]. We then extended the substrates to other
substituted aldehydes for the preparation of the structurally
diverse pyrazolo[3,4-b]pyridin-6(7H)-ones, and the corre-
sponding products 6b–6f were also isolated in 63–75%
yields (Scheme 3).
Moreover, 4-hydroxy-6-methyl-2H-pyran-2-one (7) was
employed to react with 2a and 3a in acetic acid–
acetonitrile at reflux for 4 h, and product 8 was isolated in
55% yield. It should be noted that 8 was also obtained in
64% yield in acetic acid–ethanol system (Scheme 4).
Acenaphthylene-1,2-dione (9) was reacted with 1 and 3a
in acetic acid–acetonitrile or acetic acid–ethanol medium,
resulting in 10 [22] in 56% and 85% yields (Scheme 5).
To our surprise, heating the ethanol solution of 6a at reflux
for 4h, the unexpected C–C bond cleavage product 11 was ob-
tained in 98% yield. However, in the presence of acetic acid,
11 was only obtained in 35% yield with the formation of
coumarin-fused products 4a (25%) and 5a (38%) (Scheme 6).
A plausible reaction mechanism is postulated in
Scheme 7. First, the Knoevenagel reaction of 1 and 2a
in the presence of acetic acid gives the intermediate
A, which is reacted with 3a through the Michael-type
RESULTS AND DISCUSSION
Our studies commenced with the reaction of 1, 2a, and
3a in refluxing acetonitrile without any catalyst, and the
desired 4a was isolated in 32% yield with the formation
of a small amount of aromatization product 5a. The
1
structures of 4a and 5a were confirmed by means of H
NMR, 13C NMR, HRMS, and IR spectra. The former
was further clarified by X-ray single-crystal diffraction
analysis (Fig. 1) [20]. When the reaction was carried out
in the presence of ZrCl4, InCl3, FeCl3, L-proline,
trifluoroacetic acid, iodine, and acetic acid within differ-
ent solvents, it was found that 4a was obtained in 95%
yield in acetic acid and acetonitrile combination system
(1:5). Next, we were expecting to obtain aromatization
product 5a as the major product. In consideration of the
oxidization and high boiling point of dimethylsulfoxide,
the reaction was heated in dimethylsulfoxide at 140°C in
the presence of acetic acid. We were pleased to find that
5a was isolated in 82% yield only with a trace amount
of 4a (Table 1).
With these results in hand, a variety of substituted
aldehydes were subsequently investigated under the
aforementioned optimal conditions, and the results are
summarized in Scheme 1. It was observed that 2a
substrates bearing 4-substituted or 2-substituted electron-
donating groups (–Me, –OMe, –t-Bu, and –NMe2) gave
the corresponding products 4b–4f in 65–86% yields.
Hydroxyl group substrate was well tolerated in the
reaction, leading to the final product 4g in 89% yield.
Substrates bearing withdrawing groups (–Br and –NO2)
also delivered 4h and 4i in good to excellent yield. To
our delight, heteroaromatic substrates (furan, thiophene,
Figure 1. X-ray structures of 4a and 6a.
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Month 2015
Selective Synthesis of Pyrazolo[3,4-b]pyridines and
Pyrazolo[3,4-b]pyridin-6(7H)-ones
Table 1
Optimization of the reaction conditions for the synthesis of 4a/5aa.
Yield (%)c
Entry
Catalyst/solventb
Temperature (°C)
Time (h)
4a
5a
1
2
3
4
5
6
7
8
None/MeCN
ZrCl4/MeCN
InCl3/MeCN
FeCl3/MeCN
L-proline/MeCN
TFA/MeCN (1:10)
I2/MeCN
Reflux
Reflux
Reflux
Reflux
Reflux
Reflux
Reflux
120
Reflux
Reflux
Reflux
50
10
10
10
10
10
6
6
10
6
32
75
80
46
47
85
40
89
82
71
95
54
32
75
49
4
—
—
15
8
—
d
—
AcOH
5
d
d
9
AcOH/MeCN (1:10)
AcOH/MeCN (1:20)
AcOH/MeCN (1:5)
AcOH/MeCN (1:5)
AcOH/MeCN (1:5)
AcOH/DCM (1:5)
AcOH/toluene (1:5)
AcOH/DMSO (1:5)
AcOH/DMSO (1:5)
AcOH/DMSO (1:2)
AcOH/DMSO (1:1)
—
—
10
11e
12e
13
14
15
16
17
18
19
6
6
—
—
—
12
21
82
75
55
48
12
12
10
10
10
10
10
10
25
Reflux
Reflux
Reflux
Reflux
Reflux
Reflux
d
—
—
d
20
15
aAll reactions were performed with 1 (0.5 mmole), 2a (0.5 mmole), and 3a (0.5 mmole) in an appropriate solvent (6 mL).
b20 mol% of catalyst was employed in these reactions unless mentioned; values in parentheses were the volume ratio of catalyst/solvent.
cIsolated yield.
dTrace amount of product.
eUnexpected insoluble white solid was formed.
Scheme 1. Synthesis of coumarin-fused 4,7-dihydro-1H-pyrazolo-[3,4-b]
pyridines (4).
Scheme 2. Synthesis of coumarin-fused pyrazolo[3,4-b]pyridines (5).
intermediate C after loss of water, followed by proton
transfer to give 4a [11]. Aromatization product 5a was
obtained from 4a at high temperature in the presence
of dimethylsulfoxide and air. The other pathway is that
the amino group attacks the ester carbonyl group in
addition reaction to deliver the intermediate B [23]. One
pathway is that the amino group attacks the ketone car-
bonyl group, furnishing the intramolecular cyclization
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M. Liu, G. Yin, C. Zhu, and C. Yao
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Scheme 3. Synthesis of pyrazolo[3,4-b]pyridin-6(7H)-ones (6).
aldehydes, and 5-aminopyrazoles/5-aminoisoxazole. The
possible reaction mechanism was postulated. All these
reported compounds were characterized by means of H
1
NMR, 13C NMR, HRMS, and IR spectra. The structures
of 4a and 6a were further clarified by X-ray single-crystal
diffraction analysis. The prominent advantages of this
approach are easily available starting materials, wide scope
of substrates, and excellent yields.
EXPERIMENTAL
Scheme 4
All the chemicals were commercially available and used
without further purification. All the organic solvents were
1
dried and freshly distilled before use. H and 13C NMR
were recorded in CDCl3 or DMSO-d6 using Bruker AV
300-MHz spectrometers at 300 and 75MHz (Bruker,
Germany), respectively. Chemical shifts are reported
relative to tetramethylsilane (TMS) (internal standard).
High-resolution mass spectra were recorded using a Bruker
ultrafleXtreme MALDI-TOF/TOF (HCCA matrix) (Bruker).
IR spectra were obtained as KBr pellet samples using a
Nicolet 5700 FTIR spectrometer (Thermo, USA). Flash
column chromatography was performed on silica gel
(200–300meshes). Melting points were determined using
an uncorrected X-4 apparatus (Shanghai Precision & Scien-
tific Instrument Co., Ltd., China). The X-ray crystal structure
determination was performed using a Bruker SMART
APEX CCD system (Bruker).
Scheme 5
General one-pot procedure for the synthesis of 4.
A
mixture of
1
(0.5 mmole),
2
(0.5 mmole), and
3
(0.5 mmole) was heated in AcOH/MeCN (1:5, 6 mL)
under reflux. After the reaction was completed (6 h,
monitored by thin layer chromatography (TLC)), the
mixture was slowly cooled at room temperature and
purified by column chromatography using petroleum
ether–ethyl acetate as the eluent to deliver the desired
acetic acid–ethanol medium to give 6a [24], which
could be converted to the C–C bond cleavage product
11 in refluxing ethanol [25]. The experimental results
in Scheme 7 indicate that the formation of 6a from
intermediate B is reversible in acetic acid–ethanol
combination system.
products 4.
8-Methyl-7,10-diphenyl-10,11-dihydrochromeno[4,3-b]pyrazolo
[4,3-e]pyridin-6(7H)-one (4a). White solid, mp 223–224°C; IR
1
(KBr) 750, 1028, 1204, 1447, 1537, 1699, 3406cmꢀ1; H
NMR (CDCl3): δ 2.06 (s, 3H), 5.32 (s, 1H), 7.14–7.61
(m, 14H); 13C NMR (CDCl3): δ 12.3, 37.9, 102.8, 103.4,
113.3, 117.8, 119.8, 122.7, 123.9, 126.7, 127.7, 128.26,
128.29, 130.2, 131.7, 135.1, 138.0, 141.6, 144.9, 147.5,
152.7, 161.2; HRMS: m/z calcd for C26H20N3O2: 406.1550,
found: 406.1562 [M +H]+.
CONCLUSION
In summary, we have described a solvent-tunable three-
component reaction for the selective synthesis of new
coumarin-fused tetracyclic system from 4-hydroxycoumarin,
Scheme 6
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Month 2015
Selective Synthesis of Pyrazolo[3,4-b]pyridines and
Pyrazolo[3,4-b]pyridin-6(7H)-ones
Scheme 7. The proposed reaction mechanism.
8-Methyl-10-phenyl-7-(p-tolyl)-10,11-dihydro-chro-meno[4,3-b]
pyrazolo[4,3-e]pyri-din-6(7H)-one (4b).
m/z calcd for C27H22N3O3: 436.1656, found: 436.1647
[M + H]+.
White solid, mp
227–228°C; IR (KBr) 844, 1033, 1211, 1453, 1539,
1711, 3431cmꢀ1 1H NMR (CDCl3): δ 2.07 (s, 3H),
7-(4-(tert-Butyl)phenyl)-8-methyl-10-phenyl-10,11-dihydro-
;
chromeno[4,3-b]pyrazolo[4,3-e]pyridin-6(7H)-one (4e).
Yellow
solid, mp 247–248°C; IR (KBr) 758, 1034, 1211, 1534,
1626, 1712, 3441 cmꢀ1 1H NMR (CDCl3): δ 1.24
2.28 (s, 3H), 5.26 (s, 1H), 7.06 (d, J= 7.9 Hz, 2H), 7.20–
7.23 (m, 2H), 7.29–7.60 (m, 9H); 13C NMR (CDCl3): δ
12.3, 21.0, 37.4, 102.9, 103.5, 113.3, 117.7, 119.9,
122.6, 123.8, 127.6, 128.1, 128.9, 130.2, 131.6, 135.1,
136.2, 138.0, 141.5, 142.0, 147.4, 152.6, 161.2; HRMS:
m/z calcd for C27H22N3O2: 420.1707, found: 420.1707
;
(s, 9H), 2.04 (s, 3H), 5.14 (s, 1H), 7.23–7.60 (m, 13H).
13C NMR (CDCl3): δ 12.2, 31.2, 34.2, 37.1, 102.6, 103.5,
113.4, 117.3, 120.4, 122.7, 123.7, 125.0, 127.4, 127.6,
129.9, 131.4, 135.3, 137.9, 141.9, 147.2, 149.1, 152.4,
161.4. HRMS: m/z calcd for C30H28N3O2: 462.2176,
[M + H]+.
found: 462.2178 [M+ H]+.
7-(4-Methoxyphenyl)-8-methyl-10-phenyl-10,11-dihydro-
chromeno[4,3-b]pyrazolo[4,3-e]pyridin-6(7H)-one (4c).
White
solid, mp 217–219°C; IR (KBr) 758, 1032, 1250, 1454,
1539, 1710, 3430 cmꢀ1 1H NMR (CDCl3): δ 2.04
7-(4-(Dimethylamino)phenyl)-8-methyl-10-phenyl-10,11-dihydro-
chromeno[4,3-b]pyrazolo[4,3-e] pyridin-6(7H)-one (4f). Yellow
;
solid, mp 260–261°C; IR (KBr) 765, 1033, 1214,
(s, 3H), 3.74 (s, 3H), 5.20 (s, 1H), 6.78 (d, J=8.5Hz, 2H),
7.24–7.60 (m, 11H); 13C NMR (CDCl3): δ 12.2, 36.9,
55.2, 102.9, 103.5, 113.4, 113.6, 117.6, 120.1, 122.7,
123.8, 127.6, 129.3, 130.1, 131.6, 135.1, 137.3, 138.0,
141.4, 147.4, 152.5, 158.2, 161.3; HRMS: m/z calcd for
1533, 1709, 3444 cmꢀ1 1H NMR (CDCl3): δ 2.09 (s,
;
3H), 2.89 (s, 6H), 5.25 (s, 1H), 6.65–6.67 (m, 2H),
7.07 (s, 1H), 7.18–7.22 (m, 1H), 7.30–7.61 (m, 9H);
13C NMR (CDCl3): δ 12.3, 36.7, 40.9, 103.4, 103.7,
112.7, 113.5, 117.7, 119.7, 122.6, 123.8, 127.6, 129.0,
130.2, 131.5, 135.1, 138.1, 141.0, 147.6, 152.6, 161.3;
HRMS: m/z calcd for C28H25N4O2: 449.1972, found:
C25H20N3O: 436.1656, found: 436.1656 [M+H]+.
7-(2-Methoxyphenyl)-8-methyl-10-phenyl-10,11-dihydro-
449.1972 [M + H]+.
chromeno[4,3-b]pyrazolo[4,3-e]pyridin-6(7H)-one (4d).
White
solid, mp 171–174°C; IR (KBr) 757, 1023, 1246, 1542,
7-(3-Hydroxyphenyl)-8-methyl-10-phenyl-10,11-dihydro-
1
1696, 3448 cmꢀ1; H NMR (CDCl3): δ 2.07 (s, 3H), 3.84
chromeno[4,3-b]pyrazolo[4,3-e]pyridin-6(7H)-one (4g).
Yellow
solid, mp 159–160°C; IR (KBr) 765, 1043, 1211, 1450,
1537, 1671, 3291cmꢀ1 1H NMR (DMSO-d6): δ 1.97
(s, 3H), 5.67 (s, 1H), 6.83–6.89 (m, 2H), 7.12–7.22
(m, 3H), 7.30–7.33(m, 1H), 7.39–7.44 (m, 2H), 7.50–7.58
(m, 5H); 13C NMR (CDCl3): δ 12.1, 32.1, 55.9,
102.5, 103.4, 111.3, 113.3, 117.7, 119.7, 120.8, 122.6,
123.8, 127.5, 127.8, 129.8, 130.2, 131.5, 133.5, 135.2,
138.1, 142.4, 147.5, 152.7, 156.7, 161.0; HRMS:
;
(s, 3H), 5.09 (s, 1H), 6.54–6.57 (m, 1H), 6.66–6.74
(m, 2H), 7.05 (t, J =7.8 Hz, 1H), 7.35–7.44 (m, 3H),
7.55–7.69 (m, 5H), 8.04–8.07 (m, 1H), 9.27 (s, 1H),
10.02 (s, 1H); 13C NMR (DMSO-d6): δ 12.1, 101.4,
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M. Liu, G. Yin, C. Zhu, and C. Yao
Vol 000
104.1, 113.4, 114.0, 114.8, 116.5, 118.7, 122.6, 123.7,
126.7, 129.0, 129.4, 131.8, 136.0, 138.8, 143.8, 145.9,
147.6, 152.0, 157.2, 160.6; HRMS: m/z calcd for
C26H20N3O3: 422.1499, found: 422.1499 [M + H]+.
152.3, 161.5, 162.4.; HRMS: m/z calcd for C25H19N4O2:
407.1503, found: 407.1503 [M + H]+.
7,8-Dimethyl-10-phenyl-10,11-dihydrochromeno[4,3-b]pyrazolo[4,3-
e]pyridin-6(7H)-one (4m). Yellow solid, mp 207–209°C;
1
IR (KBr) 754, 1014, 1215, 1527, 1662, 3448 cmꢀ1; H
7-(4-Bromophenyl)-8-methyl-10-phenyl-10,11-dihydrochromeno[4,3-
NMR (CDCl3): δ 1.45 (d, J = 6.6 Hz, 3H), 2.32 (s, 3H),
4.27 (q, J = 6.6 Hz, 1H), 6.98 (s, 1H), 7.30–7.45 (m, 4H),
7.52–7.61 (m, 5H). 13C NMR (CDCl3): δ 12.3, 23.1, 26.8,
103.9, 104.3, 113.3, 117.7, 119.6, 122.6, 123.9, 127.6,
130.2, 131.6, 134.8, 138.0, 142.1, 147.0, 152.5, 161.7;
HRMS: m/z calcd for C21H18N3O2: 344.1394, found:
b]pyrazolo[4,3-e]pyridin-6(7H)-one (4h).
White solid, mp
239–240°C; IR (KBr) 753, 1050, 1393, 1538, 1696,
3428 cmꢀ1
;
1H NMR (CDCl3): δ 2.05 (s, 3H), 5.29
(s, 1H), 7.18–7.25 (m, 2H), 7.27–7.61 (m, 11H); 13C NMR
(CDCl3): δ 12.3, 37.5, 102.3, 102.8, 113.1, 117.8, 119.8,
120.6, 122.7, 124.0, 127.8, 130.1, 130.3, 131.4, 131.9,
135.0, 137.9, 141.6, 143.9, 147.4, 152.7, 161.1; HRMS:
m/z calcd for C26H19BrN3O2: 484.0655, found: 484.0655
344.1384 [M + H]+.
8-Methyl-7-phenyl-7,11-dihydro-6H-chromeno[4,3-b]isoxazolo[4,5-
[M + H]+.
e]pyridin-6-one (4n).
White solid, mp 254–256°C; IR
(KBr) 757, 1063, 1264, 1514, 1666, 3447cmꢀ1; 1H NMR
(DMSO-d6): δ 1.91 (s, 3H), 5.17 (s, 1H), 7.15–7.22
(m, 1H), 7.27 (d, J =4.2 Hz, 4H), 7.38–7.47 (m, 2H),
7.63–7.69 (m, 1H), 8.21 (d, J = 7.2 Hz, 1H), 11.5 (s, 1H);
13C NMR (DMSO-d6): δ 9.8, 37.3, 95.2, 100.5, 113.3,
116.8, 123.1, 124.2, 126.6, 127.8, 128.3, 132.2, 143.1,
145.4, 152.2, 158.4, 159.1, 160.2; HRMS: m/z calcd for
C20H15N2O3: 331.1077, found: 331.1078 [M+ H]+.
8-Methyl-7-(4-nitrophenyl)-10-phenyl-10,11-dihydrochromeno[4,3-
b]pyrazolo[4,3-e]pyridin-6(7H)-one (4i). Yellow solid, mp
207–209°C; IR (KBr) 755, 1039, 1349, 1533, 1674,
3426 cmꢀ1 1H NMR (CDCl3): δ 1.96 (s, 3H), 5.37
;
(s, 1H), 7.17– 7.55 (m, 11H), 8.07 (d, J = 8.6 Hz, 2H); 13
C
NMR (CDCl3): δ 12.3, 38.1, 101.4, 102.0, 112.9, 117.9,
120.0, 122.7, 123.7, 124.2, 128.0, 129.3, 130.4, 132.3,
135.1, 137.7, 142.1, 146.7, 147.2, 151.9, 152.7, 161.1;
HRMS: m/z calcd for C26H19N4O4: 451.1401, found:
General one-pot procedure for the synthesis of 5. A mixture
of 1 (0.5 mmole), 2 (0.5 mmole) and 3a (0.5 mmole) was
heated in AcOH/DMSO (1:5, 6 mL) at 140°C. After the
reaction was completed (10 h, monitored by TLC), the
mixture was slowly cooled at room temperature and
purified by column chromatography using petroleum
ether–ethyl acetate as the eluent to deliver the desired
451.1404 [M +H]+.
7-(Furan-2-yl)-8-methyl-10-phenyl-10,11-dihydrochromeno[4,3-
b]pyrazolo[4,3-e]pyridin-6(7H)-one (4j). Yellow solid, mp
225–227°C; IR (KBr) 760, 1213, 1258, 1531, 1673,
3437 cmꢀ1 1H NMR (CDCl3): δ 2.22 (s, 3H), 5.50
;
(s, 1H), 6.20 (d, J = 3.2 Hz, 1H), 6.27–6.29 (m, 1H), 7.20–
7.59 (m, 10H); 13C NMR (CDCl3): δ 12.1, 31.5, 99.3,
100.6, 105.8, 110.3, 113.2, 117.8, 119.8, 122.7, 124.0,
127.8, 130.2, 132.0, 135.2, 137.9, 141.5, 142.4, 147.5,
152.7, 155.9, 161.2; HRMS: m/z calcd for C24H18N3O3:
396.1343, found: 396.1346 [M + H]+.
product 5.
8-Methyl-7,10-diphenylchromeno[4,3-b]pyrazolo[4,3-e]pyridin-
6(10H)-one (5a). Yellow solid, mp 253–255°C; IR (KBr)
754, 1082, 1193, 1497, 1644, 1733 cmꢀ1 1H NMR
;
(CDCl3): δ 1.92 (s, 3H), 7.30–7.41 (m, 5H), 7.53–7.61
(m, 6H), 8.37 (d, J =7.7 Hz, 2H), 8.68 (d, J = 7.9 Hz, 1H);
13C NMR (CDCl3): δ 14.3, 109.8, 116.9, 117.4, 119.7,
121.0, 124.4, 125.7, 126.2, 127.1, 128.1, 128.4, 129.1,
132.4, 136.4, 138.9, 145.8, 150.9, 152.1, 152.5, 152.9,
159.5; HRMS: m/z calcd for C26H18N3O2: 404.1394,
8-Methyl-10-phenyl-7-(thiophen-2-yl)-10,11-dihydro-chromeno[4,3-
b]pyrazolo[4,3-e]pyridin-6(7H)-one (4k).
White solid, mp
206–208°C; IR (KBr) 758, 1032, 1255, 1537, 1692,
3429 cmꢀ1 1H NMR (CDCl3): δ 2.19 (s, 3H), 5.71
;
(s, 1H), 6.88–6.91 (m, 1H), 7.06 (d, J =3.0 Hz, 1H), 7.11–
7.13 (m, 1H), 7.22 (s, 1H), 7.30–7.37 (m, 3H), 7.43–7.51
(m, 1H), 7.52–7.54 (m, 1H), 7.57–7.61 (m, 3H); 13C
NMR (CDCl3): δ 12.2, 32.4, 102.2, 102.8, 113.2, 117.9,
119.8, 122.7, 124.0, 124.3, 124.8, 126.7, 127.8, 130.3,
131.9, 135.1, 137.9, 141.2, 147.5, 149.2, 152.6, 161.4;
HRMS: m/z calcd for C24H18N3O2S: 412.1114, found:
412.1109 [M +H]+.
found: 404.1380 [M+ H]+.
8-Methyl-10-phenyl-7-(p-tolyl)chromeno[4,3-b]pyrazolo[4,3-
e]pyridin-6(10H)-one (5b). White solid, mp 250–251°C; IR
(KBr) 758, 1079, 1194, 1499, 1561, 1599, 1734cmꢀ1; 1H
NMR (CDCl3): δ 1.97 (s, 3H), 2.49 (s, 3H), 7.22
(d, J =8.0 Hz, 2H), 7.32–7.43 (m, 5H), 7.54–7.62
(m, 3H), 8.36–8.39 (m, 2H), 8.68–8.71 (m, 1H); 13C
NMR (CDCl3): δ 14.4, 21.5, 110.0, 116.9, 117.6, 119.7,
121.0, 124.4, 125.7, 126.1, 127.0, 128.8, 129.1, 132.4,
133.3, 138.1, 138.9, 145.9, 150.9, 152.1, 152.9, 153.0,
159.5; HRMS: m/z calcd for C27H20N3O2: 418.1550,
8-Methyl-10-phenyl-7-(pyridin-2-yl)-10,11-dihydrochromeno[4,3-
b]pyrazolo[4,3-e]pyridin-6(7H)-one (4l).
White solid, mp
252–254°C; IR (KBr) 760, 1044, 1260, 1535, 1696,
3434 cmꢀ1 1H NMR (CDCl3): δ 2.05 (s, 3H), 5.43
;
found: 418.1548 [M+ H]+.
7-(4-Methoxyphenyl)-8-methyl-10-phenylchromeno[4,3-
b]pyrazolo[4,3-e]pyridin-6(10H)-one (5c). White solid, mp
(s, 1H), 7.04–7.11 (m, 3H), 7.28–7.41 (m, 5H), 7.53
(d, J= 8.1Hz, 2H), 7.63–7.68 (m, 1H), 8.27–8.28 (m,
2H); 13C NMR ( CDCl3): δ 12.5, 40.9, 101.1, 102.0,
113.4, 117.3, 120.8, 121.8, 123.5, 123.6, 124.1, 128.0,
129.7, 131.5, 136.1, 136.3, 138.1, 143.6, 147.0, 149.2,
225–227°C; IR (KBr) 751, 1183, 1249, 1503, 1602,
1736 cmꢀ1 1H NMR (CDCl3): δ 2.02 (s, 3H), 3.93
;
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Month 2015
Selective Synthesis of Pyrazolo[3,4-b]pyridines and
Pyrazolo[3,4-b]pyridin-6(7H)-ones
(s,3H), 7.07 (d, J =8.7 Hz, 2H), 7.25 (s, 1H), 7.27–7.28 (m,
1H), 7.33–7.44 (m, 3H), 7.56–7.63 (m, 3H), 8.38
(d, J=7.8Hz, 2H), 8.70–8.73 (m, 1H); 13C NMR (CDCl3):
δ 14.6, 55.3, 110.1, 113.6, 116.9, 117.8, 119.8, 121.1,
124.4, 125.7, 126.2, 128.4, 128.6, 129.1, 132.4, 138.9,
145.9, 151.0, 152.2, 152.7, 152.9, 159.6, 159.7; HRMS:
m/z calcd for C27H20N3O3: 434.1499, found: 434.1489
reflux. After the reaction was completed (30min, monitored
by TLC), insoluble solid was formed, which was filtrated
and washed with a small amount of anhydrous ethanol to
give the product 6.
5-(2-Hydroxybenzoyl)-3-methyl-1,4-diphenyl-4,5-dihydro-1H-
pyrazolo[3,4-b]pyridin-6(7H)-one (6a).
White solid,
mp 222–223°C; IR (KBr) 756, 918, 1252, 1494, 1680,
3170, 3454 cmꢀ1 1H NMR (CDCl3): δ 1.81 (s, 3H),
[M+H]+.
;
4.59 (d, J = 6.9 Hz, 1H), 4.81 (d, J = 6.9 Hz, 1H),
6.87– 6.92 (m, 1H), 6.99–7.02 (m, 1H), 7.23–7.25
(m, 2H), 7.27–7.40 (m, 6H), 7.44–7.50 (m, 3H),
7.62–7.65 (m, 1H), 8.78 (br, 1H), 11.9 (s, 1H); 13C
NMR (CDCl3): δ 12.5, 40.4, 57.2, 101.2, 118.8,
118.9, 119.2, 123.2, 127.4, 127.8, 127.9, 129.2,
129.8, 130.4, 136.3, 137.1, 140.6, 147.0, 163.2,
167.1, 200.7; HRMS: m/z calcd for C26H22N3O3:
424.1656, found: 424.1659 [M + H]+.
7-(2-Methoxyphenyl)-8-methyl-10-phenylchromeno[4,3-
b]pyrazolo[4,3-e]pyridin-6(10H)-one (5d). Yellow solid, mp
254–256°C; IR (KBr) 754, 1080, 1245, 1499, 1640,
1
1736 cmꢀ1; H NMR (CDCl3): δ 2.02 (s, 3H), 3.75 (s,
3H), 7.07–7.15 (m, 3H), 7.33–7.44 (m, 3H), 7.49–
7.63 (m, 4H), 8.40 (d, J = 8.0 Hz, 2H), 8.73 (d,
J = 8.1 Hz, 1H); 13C NMR (CDCl3): δ 14.0, 55.7,
110.7, 110.8, 116.9, 117.6, 119.9, 120.5, 121.1, 124.3,
125.4, 125.7, 126.1, 128.4, 129.1, 130.1, 132.3, 139.0,
145.8, 149.8, 151.3, 152.1, 152.9, 156.0, 159.4; HRMS:
m/z calcd for C27H20N3O3: 434.1499, found: 434.1499
5-(2-Hydroxybenzoyl)-3-methyl-1-phenyl-4-(p-tolyl)-4,5-dihydro-
1H-pyrazolo[3,4-b]pyridin-6(7H)-one (6b).
White solid,
mp 217–218°C; IR (KBr) 745, 918, 1156, 1246, 1498,
1676, 3230, 3442cmꢀ1 1H NMR (CDCl3): δ 1.81 (s,
[M + H]+.
;
8-Methyl-7-(4-nitrophenyl)-10-phenylchromeno[4,3-b]pyrazolo[4,3-
e]pyridin-6(10H)-one (5e). Yellow solid, mp 270–272°C;
3H), 2.30 (s, 3H), 4.55 (d, J = 6.8 Hz, 1H), 4.78
(d, J = 6.8 Hz, 1H), 6.89 (t, J= 7.5 Hz, 1H), 7.00 (d,
J = 8.3 Hz, 1H), 7.12–7.25 (m, 5H), 7.31–7.52 (m, 5H),
7.64 (d, J = 7.9 Hz, 1H), 8.94 (s, 1H), 11.91 (s, 1H);
13C NMR (CDCl3): δ 12.5, 21.0, 39.9, 57.3, 101.4, 118.8,
119.2, 123.1, 127.3, 127.8, 129.6, 129.8, 130.4, 136.3,
137.0, 137.1, 137.4, 137.5, 147.0, 163.1, 167.5, 200.9;
HRMS: m/z calcd for C27H24N3O3: 438.1812, found:
IR (KBr) 760, 1085, 1202, 1346, 1506, 1564, 1601,
1
1733 cmꢀ1; H NMR (CDCl3): δ 1.95 (s, 3H), 7.33–7.46
(m, 3H), 7.53–7.63 (m, 5H), 8.36 (d, J= 7.7 Hz, 2H), 8.42
(d, J = 8.7Hz, 2H), 8.68–8.71 (m, 1H). 13C NMR
(CDCl3): δ 14.5, 109.4, 116.6, 117.0, 119.3, 121.1, 123.5,
124.7, 125.7, 126.6, 128.4, 129.2, 132.9, 138.6, 143.4,
144.8, 147.9, 149.4, 150.9, 152.2, 152.7, 159.6. HRMS:
m/z calcd for C26H17N4O4: 449.1244, found: 449.1448
438.1818 [M + H]+.
[M + H]+.
5-(2-Hydroxybenzoyl)-4-(4-methoxyphenyl)-3-methyl-1-phenyl-
8-Methyl-10-phenyl-7-(thiophen-2-yl)chromeno[4,3-b]pyrazolo[4,3-
e]pyridin-6(10H)-one (5f). Yellow solid, mp 260–262°C;
4,5-dihydro-1H-pyrazolo[3,4-b] pyridin-6(7H)-one (6c). White
solid, mp 193–194°C; IR (KBr) 758, 1251, 1504, 1674,
1
3417, 3595 cmꢀ1; H NMR (CDCl3): δ 1.84 (s, 3H), 3.78
IR (KBr) 760, 1074, 1190, 1251, 1496, 1563,
1
1737 cmꢀ1; H NMR (CDCl3): δ 2.14 (s, 3H), 7.09–7.11
(s, 3H), 4.58 (d, J= 6.9 Hz, 1H), 4.81 (d, J =6.9 Hz, 1H),
6.83–6.93 (m, 3H), 7.00 (d, J = 8.3 Hz, 1H), 7.18
(d, J =8.6 Hz, 2H), 7.32–7.36 (m, 1H), 7.43–7.52
(m, 5H), 7.66 (d, J = 8.1 Hz, 1H), 8.24 (s, 1H),
11.90 (s, 1H); 13C NMR (CDCl3): δ 12.5, 39.6,
55.3, 57.5, 101.6, 114.5, 118.87, 118.91, 119.2,
123.1, 128.0, 128.5, 129.9, 130.4, 132.5, 136.1,
137.1, 137.2, 147.1, 159.0, 163.2, 167.0, 200.8;
HRMS: m/z calcd for C27H24N3O4: 454.1761, found:
454.1761 [M + H]+.
(m, 1H), 7.22–7.24 (m, 1H), 7.34–7.44 (m, 3H), 7.56–
7.63 (m, 4H), 8.37 (d, J = 7.7 Hz, 2H), 8.68–8.71 (m,
1H); 13C NMR (CDCl3): δ 13.7, 111.3, 116.9, 121.1,
124.5, 125.7, 126.3, 126.86, 126.93, 127.1, 129.1, 132.6,
135.4, 138.8, 145.5, 145.8, 150.8, 152.1, 152.8, 159.0;
HRMS: m/z calcd for C24H16N3O2S: 410.0958, found:
410.0959 [M + H]+.
7,8-Dimethyl-10-phenylchromeno[4,3-b]pyrazolo [4,3-e]pyridin-
6(10H)-one (5g). Yellow solid, mp 236–237°C; IR (KBr)
759, 1088, 1249, 1497, 1574, 1723 cmꢀ1 1H NMR
;
4-(4-(tert-Butyl)phenyl)-5-(2-hydroxybenzoyl)-3-methyl-
(CDCl3): δ 2.87 (s, 3H), 3.27 (s, 3H), 7.33–7.40 (m, 3H),
7.56–7.61 (m, 3H), 8.34–8.37 (m, 2H), 8.60–8.63 (m,
1H); 13C NMR (CDCl3): δ 16.6, 18.5, 110.6, 116.6,
117.9, 119.7, 120.9, 124.4, 125.6, 126.1, 129.0, 132.3,
138.9, 145.1, 150.9, 152.2, 152.5, 152.8, 160.9; HRMS:
m/z calcd for C21H16N3O2: 342.1237, found: 342.1232
[M + H]+.
1-phenyl-4,5-dihydro-1H-pyrazolo[3,4-b]
pyridin-6(7H)-one
(6d). White solid, mp 242–243°C; IR (KBr) 751, 1249,
1
1499, 1675, 3227, 3444 cmꢀ1; H NMR (CDCl3): δ 1.31
(s, 9H), 1.93 (s, 3H), 4.54 (d, J= 5.0 Hz, 1H), 4.85
(d, J = 5.0 Hz, 1H), 6.94 (t, J= 7.2 Hz, 1H), 7.03 (d,
J = 8.5 Hz, 1H), 7.19 (d, J = 8.3 Hz, 2H), 7.34–7.43 (m,
3H), 7.50–7.55 (m, 5H), 7.74 (d, J = 7.3 Hz, 1H), 8.02 (s,
1H), 11.89 (s, 1H); 13C NMR (CDCl3): δ 12.4, 31.3,
34.5, 39.9, 57.6, 101.4, 118.4, 119.0, 119.2, 123.1,
126.1, 126.8, 128.0, 129.9, 130.4, 136.3, 137.1, 137.2,
General one-pot procedure for the synthesis of 6.
A
mixture of
1 (0.5mmole), 2 (0.5mmole) and 3a
(0.5mmole) was heated in AcOH/EtOH (1:20, 6mL) under
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

M. Liu, G. Yin, C. Zhu, and C. Yao
Vol 000
Synthesis of 3-methyl-1,4-diphenyl-4,5-dihydro-1H-pyrazolo
[3,4-b]pyridin-6(7H)-one (11). A solution of 3a (0.5mmole)
137.7, 147.1, 150.8, 163.3, 166.9, 200.7; HRMS: m/z
calcd for C30H30N3O3: 480.2282, found: 480.2313
[M + H]+.
was heated in EtOH (4mL) under reflux. After the reaction
was completed (4h, monitored by TLC), the mixture was
slowly cooled at room temperature and purified by column
chromatography using petroleum ether–ethyl acetate
as eluent to deliver 11 as the white solid; mp 148–149°C;
4-(4-Bromophenyl)-5-(2-hydroxybenzoyl)-3-methyl-1-phenyl-
4,5-dihydro-1H-pyr-azolo[3,4-b]pyridin-6(7H)-one (6e).
White
solid, mp 220–221°C; IR (KBr) 753, 1074, 1247, 1317,
1
1493, 1678, 3238, 3447cmꢀ1; H NMR (CDCl3): δ 1.81
1
IR (KBr) 766, 1074, 1330, 1680, 3449cmꢀ1; H NMR
(s, 3H), 4.61 (d, J = 7.6Hz, 1H), 4.77 (d, J =7.6 Hz, 1H),
6.87–6.93 (m, 1H), 6.99–7.02 (m, 1H), 7.14–7.17 (m, 2H),
7.31–7.32 (m, 1H), 7.37–7.54 (m, 7H),7.59–7.62 (m, 1H),
8.64 (s, 1H), 11.86 (s, 1H);13C NMR (CDCl3): δ 12.6,
39.7, 56.8, 100.8, 118.9, 119.0, 119.3, 121.7, 123.1, 128.0,
129.3, 129.7, 130.2, 132.3, 136.3, 137.0, 137.3, 139.5,
146.8, 163.1, 167.0, 200.3; HRMS: m/z calcd for
C26H21BrN3O3: 502.0761, found: 502.0767 [M+H]+.
5-(2-Hydroxybenzoyl)-3-methyl-1-phenyl-4-(thiophen-2-yl)-4,5-
(CDCl3): δ 1.96 (s, 3H), 2.87 (dd, J1 =16.3Hz, J2 =6.5Hz,
1H), 3.08 (dd, J1 =16.3Hz, J2 =7.3Hz, 1H), 4.24 (t,
J=6.8Hz, 1H), 7.22–7.25 (m, 2H), 7.28–7.41 (m, 3H),
7.46–7.53 (m, 4H), 7.76 (s, 1H); 13C NMR (CDCl3): δ
12.5, 35.5, 40.6, 102.7, 122.9, 127.1, 127.2, 127.8, 128.9,
129.9, 137.3, 137.4, 142.2, 146.9, 169.6; HRMS: m/z calcd
for C19H18N3O: 304.1444, found: 304.1447 [M+H]+.
dihydro-1H-pyrazolo[3,4-b] pyridin-6(7H)-one (6f).
Yellow
Acknowledgments. We gratefully acknowledge support from the
Educational Commission of Hubei Province (D20142501).
solid, mp 226–227°C; IR (KBr) 757, 1075, 1251, 1338,
1
1495, 1681, 3233, 3439 cmꢀ1; H NMR (CDCl3): δ 1.99
(s, 3H), 4.92 (s, 2H), 6.90–6.98 (m, 3H), 7.00–7.03 (m,
1H), 7.20–7.22 (m, 1H), 7.29–7.35 (m, 1H), 7.40–7.55 (m,
5H), 7.75–7.79 (m, 1H), 8.43 (s, 1H), 11.84 (s, 1H); 13C
NMR (CDCl3): δ 12.3, 35.5, 58.1, 101.2, 118.6, 119.0,
119.4, 123.2, 125.1, 125.3, 127.1, 128.0, 129.8, 130.3,
136.1, 137.0, 137.3, 144.2, 146.9, 163.2, 166.5, 200.1;
HRMS: m/z calcd for C24H20N3O3S: 430.1220, found:
430.1221 [M+ H]+.
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One-pot procedure for the synthesis of 8 and 10. Products
8 and 10 were synthesized as analogous procedure for 4 and 6.
(Z)-5-(3-Hydroxybut-2-en-1-yl)-3-methyl-1,4-diphenyl-4,5-
dihydro-1H-pyrazolo[3,4-b]pyridin-6(7H)-one (8).
White
solid; mp 229–230°C; IR (KBr) 757, 1076, 1324, 1603,
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(s, 3H), 2.02 (s, 3H), 3.70 (d, J = 5.8 Hz, 1H), 4.64
(d, J = 5.8 Hz, 1H), 5.58 (s, 1H), 7.20–7.24 (m, 2H),
7.28–7.39 (m, 4H), 7.45–7.49 (m, 4H), 8.16 (s, 1H),
15.07 (s, 1H); 13C NMR (CDCl3): δ 12.4, 23.8, 38.6,
60.3, 100.0, 101.7, 122.9, 127.4, 127.5, 127.9, 129.0,
129.9, 136.2, 137.2, 140.9, 147.2, 167.2, 188.5, 190.4;
HRMS: m/z calcd for C23H22N3O3: 388.1656, found:
388.1662 [M + H]+.
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[15] Chen, J. H.; Liu, W. M.; Ma, J. J.; Xu, H. T.; Wu, J. S.; Tang,
X. L.; Fan, Z. Y.; Wang, P. F. J Org Chem 2012, 77, 3475.
[16] Hao, Y.; Xu, X. P.; Chen, T.; Zhao, L. L.; Ji, S. J. Org Biomol
Chem 2012, 10, 724.
5′-(2-hydroxybenzoyl)-3′-methyl-1′-phenyl-5′,7′-dihydro-2H-
spiro [acenaphthylene-1,4′-pyrazolo[3,4-b]pyridine]-2,6′(1′H)-
dione (10). Yellow solid; mp 269–270°C; IR (KBr) 759,
1304, 1490, 1562, 1633, 1715, 3257, 3440 cmꢀ1 1H
;
NMR (DMSO-d6): δ 0.86 (s, 3H), 6.41 (s, 1H), 6.88
(d, J= 7.7Hz, 2H), 7.36–7.69 (m, 8H), 7.88–8.05
(m, 4H), 8.31 (d, J= 8.1 Hz, 1H), 10.99 (s, 1H), 11.20
(s, 1H); 13C NMR (DMSO-d6): δ 11.3, 52.2, 58.1, 102.8,
117.6, 119.3, 120.4, 121.8, 122.1, 122.7, 125.2, 127.1,
128.7, 128.9, 129.3, 130.2, 131.4, 131.5, 132.4, 136.3,
137.8, 138.1, 139.3, 141.2, 144.1, 160.0, 168.1,
197.9,201.6; HRMS: m/z calcd for C31H22N3O4:
500.1605, found: 500.1616 [M + H]+.
[17] Pal, S.; Khan, M. N.; Karamthulla, S.; Choudhury, L. H. RSC
Adv 2013, 3, 15705.
[18] Ghosh, A.; Khan, A. T. Tetrahedron Lett 2014, 55, 2006.
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Month 2015
Selective Synthesis of Pyrazolo[3,4-b]pyridines and
Pyrazolo[3,4-b]pyridin-6(7H)-ones
[19] Yin, G. D.; Ren, T. B.; Rao, Y.; Zhou, Y. F.; Li, Z.; Shu, W. M.;
Wu, A. X. J Org Chem 2013, 78, 3132.
space group P2(1)/n, Z = 4, 4468 reflections measured, 3399 unique
(Rint = 0.0418) which were used in all calculations. The final wR(F
was 0.1185 (all data).
[22] Ahadi, S.; Ghahremanzadeh, R.; Mirzaei, P. Bazgir, A.
Tetrahedron 2009, 65, 9316.
[23] Jiang, B.; Zhang, G.; Ma, N.; Shi, F.; Tu, S. J.; Kaur, P.; Li, G. G.
Org Biomol Chem 2011, 9, 3834.
[24] Shi, F.; Zhang, J. Y.; Tu, S. J.; Jia, R. H.; Zhang, Y.; Jiang, B.;
Jiang, H. J Heterocyclic Chem 2007, 44, 1013.
2)
[20] Crystal data of 4a (CCDC 1037057). C24H19N3O2·2C2H6O,
M = 497.58, triclinic, a = 11.270(4), b = 12.125(4), c = 12.411(5) Å,
α = 111.185(8)°, β = 103.908(9)°, γ = 109.487(9)°, U = 1359.3(8) Å3,
T = 296(2) K, space group P-1, Z 2, 6921 reflections measured, 3115
unique (Rint = 0.0605) which were used in all calculations. The final wR
(F2) was 0.2101 (all data).
[21] Crystal data of 6a (CCDC 1037058). C26H21N3O3,
M = 423.46, monoclinic, a = 16.8092(15), b = 6.6511(7), c = 21.0780(19)
Å, α = 90°, β = 112.272(2)o, γ = 90°, U = 2180.7(4) Å3, T = 296(2) K,
[25] Ma, N.; Jiang, B.; Zhang, G. Tu, S. J.; Wever, W.; Li, G. G.
Green Chem 2010, 12, 1357.
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet