Efficient synthesis of novel 5-phenylsulfonyl-substituted 4,5-dihydro-1Hpyrazolo[ 3,4-b]pyridines

Article abstract of DOI:10.3184/174751916X14737765008687

An efficient method for the synthesis of novel 5-phenylsulfonyl substituted 4,5-dihydro-1H-pyrazolo[3,4-b]pyridines from 5-Aminopyrazoles, aldehydes and β-ketosulfones in refluxing acetic acid is described. The X-ray crystallographic structure of the prod

Full text of DOI:10.3184/174751916X14737765008687

JOURNAL OF CHEMICAL RESEARCH 2016
VOL. 40 OCTOBER, 591–593
RESEARCH PAPER 591
Efficient synthesis of novel 5-phenylsulfonyl-substituted 4,5-dihydro-1H-
pyrazolo[3,4-b]pyridines
Ling Fan*, Chengcheng Ruan, Binghuang Guo, Xiwu Tang and Peng Xia
Hubei Collaborative Innovation Center for Rare Metal Chemistry, Hubei Key Laboratory of Pollutant Analysis and Reuse Technology, Hubei Normal University,
Huangshi 435002, P.R. China
Anefficientmethodforthesynthesisofnovel5-phenylsulfonylsubstituted4,5-dihydro-1H-pyrazolo[3,4-b]pyridinesfrom5-aminopyrazoles,
aldehydes and β-ketosulfones in refluxing acetic acid is described. The X-ray crystallographic structure of the product was determined.
Keywords: phenylsulfonyl group, 4,5-dihydro-1H-pyrazolo[3,4-b]pyridines, β-ketosulfones, Hantzsch-type reaction
1
Recently, the Hantzsch-type three-component reaction of an
aldehyde, an active methylene compound and aminopyrazole has
been extensively investigated, often affording the substituted 4,7-
dihydro-1H-pyrazolo[3,4-b]pyridine.1,2 The phenylsulfonyl moiety
is usually incorporated as an active unit in many nitrogen-containing
pharmaceutical heterocyclic molecules3 and commercial drugs, such
as rofecoxib,4 parecoxib5 and etoricoxib.6 Moreover, β-ketosulfone
can be used as an important synthon for introducing the sulfonyl
moiety into a molecule.7 However, unlike other β-dicarbonyl
compounds and their analogues, β-ketosulfone has rarely been
exploited as an active methylene compound in the Hantzsch-type
multicomponent reaction.8 Recently, Saleh and co-workers found
that sonicating a mixture of 5-aminopyrazole, aromatic aldehyde
and β-ketosulfone at room temperature in the presence of a
catalytic amount of p-toluenesulfonic acid yielded the 5-position
unsubstituted pyrazolo[3,4-b]pyridines in excellent yields involving
the desulfonylation pathway.9 As a continuation of our work on the
synthesis of functionalised pyrazolo[3,4-b]pyridine,10 we herein
report an efficient synthesis of novel 5-phenylsulfonyl-substituted
4,5-dihydro-pyrazolo[3,4-b]pyridines from 5-aminopyrazole,
aldehyde and β-ketosulfone in refluxing acetic acid.
yield, which was confirmed by means of H NMR, 13C NMR,
IR, MS and X-ray single-crystal diffraction analysis (Fig.
1). It is well known that the Hantzsch-type multicomponent
reaction often affords the usual 4,7-dihydro-1H-pyrazolo[3,4-b]
pyridine or its aromatisation product pyrazolo[3,4-b]pyridine.
However, it should be noted that the novel 5-phenylsulfonyl-
substituted 4,5-dihydro-1H-pyrazolo[3,4-b]pyridine was the
main product in this reaction, probably due to the effect of the
electron-withdrawing sulfonyl group. In addition, 3,5-dimethyl-
1,4,7-triphenyl-1,7-dihydrodipyrazolo[3,4-b:4',3'-e]pyridine (4a')
was isolated in 12% yield. Decreasing the reaction temperature
resulted in a lower yield of 4a.
In order to explore the generality of the reaction, the substrate
scope was further examined, as shown in Scheme 1. The reactions
of electron-donating (–Me, –OMe, –N(CH3)2) and electron-
withdrawing (–NO2, –Cl, –Br) substituted benzaldehydes with
2a and 3a afforded the corresponding products 4b–h in 52–73%
yields. The substrates for furan-2-carbaldehyde and thiophene-
2-carbaldehyde were also suitable for the reaction, delivering
the corresponding products 4i and 4j in 50% and 56% yields,
respectively. However, aliphatic butanal gave only the product 4k
in 30% yield. In addition, replacement of 2a with 1,3-diphenyl-
1H-pyrazol-5-amine (2b) also resulted in 4l in good yield.
Moreover, when 1-(phenylsulfonyl)propan-2-one (3b) was
employed to react with 1a and 2a, it was found that 4m and 4m'
were obtained in 51% and 20% yields, respectively (Scheme 2).
When a mixture of benzaldehyde (1a), 3-methyl-1-phenyl-
1H-pyrazol-5-amine (2a) and 1-phenyl-2-(phenylsulfonyl)
ethanone (3a) was heated in refluxing acetic acid for 8 h,
(4RS,5SR)-3-methyl-1,4,6-triphenyl-5-(phenylsulfonyl)-4,5-
dihydro-1H-pyrazolo[3,4-b]pyridine (4a) was obtained in 67%
Fig. 1 X-ray structure of compound 4a with 30% probability.
* Correspondent. E-mail: fanlinghbnu@163.com

592 JOURNAL OF CHEMICAL RESEARCH 2016
R1
H
R1
C O
R2
N
O
S
R2
Ph
O
1
AcOH, 120 oC
6~10 h
O
S
O
+
N
H2N
N
N
Ph
Ph
N
Ph
O
Ph
Ph
4a~4l
3a
2
1
2
1
2
4a
4b
4c
4d
4e
4f
(R =Ph, R =Me, 67%)
4g
4h
(R =4-ClC6H4, R =Me, 57%)
1
2
1
2
(R =4-BrC6H4, R =Me, 52%)
(R =4-MeC6H4, R =Me, 52%)
1
2
1
2
(R =4-MeOC6H4, R =Me, 73%)
4i
4j
4k
4l
(R =2-furyl, R =Me, 50%)
1
2
1
2
(R =2-MeOC6H4, R =Me, 61%)
(R =2 thienyl, R =Me, 56%)
1
2
1
2
(R =4-NMe2C6H4, R =Me, 68%)
(R =n-C3H7, R =Me, 30%)
1
2
1
2
(R =2-NO2C6H4, R =Me, 56%)
(R =Ph, R =Ph, 55%)
Scheme 1 Scope of the substrates.
Ph
H
C O
1a
Ph
O
S
O
Ph
Me
Me
N
Me
Ph
O
S
O
O
S
O
AcOH
120 oC, 8 h
+
N
+
Ph
N
H2N
2a
N
N
Ph
Me
N
N
Me
N
O
Ph
Ph
Ph
'
4m
3b
4m
(20%)
(51%)
Scheme 2
300 MHz) δ 8.42 (d, J = 8.6 Hz, 4H), 7.59–7.46 (m, 9H), 7.31–7.26 (m,
2H), 2.10 (s, 6H); 13C NMR (CDCl3, 75 MHz) δ 150.5, 144.5, 141.5, 139.7,
134.3, 129.03, 128.95, 128.8, 128.1, 125.1, 120.3, 113.5, 14.8; Anal. calcd for
C27H21N5: C, 78.05; H, 5.09; N, 16.86; found: C, 78.19; H, 5.10; N, 16.83.
(4RS,5SR)-3-Methyl-1,6-diphenyl-5-(phenylsulfonyl)-4-p-tolyl-4,5-
dihydro-1H-pyrazolo[3,4-b]pyridine (4b): Yellow solid; 134 mg, yield
52%; m.p. 187–189 °C; 1H NMR (CDCl3, 300 MHz) δ 7.94 (d, J = 8.3 Hz,
2H), 7.55–7.38 (m, 9H), 7.31–7.17 (m, 4H), 7.03 (d, J = 8.0 Hz, 2H), 6.95
(d, J = 8.0 Hz, 2H), 5.14 (s, 1H), 4.98 (s, 1H), 2.25 (s, 3H), 2.18 (s, 3H);
13C NMR (CDCl3, 75 MHz) δ 156.9, 145.2, 145.0, 138.4, 137.5, 137.0,
136.5, 136.2, 134.2, 131.6, 129.9, 129.0, 128.65, 128.56, 128.2, 127.9, 126.7,
126.1, 121.8, 104.5, 69.1, 36.7, 21.0, 12.0; FTIR (KBr) (ν cm−1): 3440, 2923,
1499, 1310, 1181, 1121, 1076, 768, 683; HRMS m/z (MALDI) calcd for
C32H28N3O2S [M + H]+ 518.1897; found: 518.1907.
(4RS,5SR)-4- (4-Methoxyphenyl)-3-methyl-1,6-diphenyl-5-
(phenylsulfonyl)-4,5-dihydro-1H-pyrazolo[3,4-b]pyridine (4c): Yellow
solid; 194 mg, yield 73%; m.p. 150–151 °C; 1H NMR (CDCl3, 300 MHz)
δ 7.93 (d, J = 7.9 Hz, 2H), 7.54 (d, J = 8.8 Hz, 2H), 7.50–7.38 (m, 7H),
7.31–7.17 (m, 4H), 7.00–6.95 (m, 2H), 6.77–6.74 (m, 2H), 5.13 (s, 1H), 4.96
(s, 1H), 3.72 (s, 3H), 2.17 (s, 3H); 13C NMR (CDCl3, 75 MHz) δ 159.1, 156.9,
145.2, 145.1, 138.5, 137.1, 136.6, 134.2, 131.6, 131.3, 129.0, 128.7, 128.6,
128.3, 127.98, 127.96, 126.1, 121.8, 114.6, 104.7, 69.4, 55.2, 36.4, 12.0; FTIR
(KBr) (ν cm−1): 3437, 2932, 1504, 1315, 1247, 1181, 1123, 1078, 752, 682;
HRMS m/z (MALDI) calcd for C32H28N3O3S [M + H]+ 534.1846; found:
534.1847.
(4RS,5SR)-4- (2-Methoxyphenyl)-3-methyl-1,6-diphenyl-5-
(phenylsulfonyl)-4,5-dihydro-1H-pyrazolo[3,4-b]pyridine (4d): Yellow
solid; 163 mg, yield 61%; m.p. 117–119 °C; 1H NMR (CDCl3, 300 MHz)
δ 7.92 (d, J = 8.2 Hz, 2H), 7.56 (d, J = 7.6 Hz, 2H), 7.50–7.38 (m, 7H),
7.32–7.15 (m, 5H), 6.91 (d, J = 8.1 Hz, 1H), 6.71 (t, J = 7.5 Hz, 1H), 6.59
(d, J = 7.5 Hz, 1H), 5.52 (s, 1H), 5.15 (s, 1H), 3.95 (s, 3H), 2.17 (s, 3H);
13C NMR (CDCl3, 75 MHz) δ 157.8, 156.3, 145.9, 145.4, 138.5, 137.2, 137.1,
134.0, 131.4, 129.00, 128.96, 128.6, 128.5, 128.2, 127.9, 126.2, 126.0, 121.8,
120.8, 110.7, 103.5, 66.6, 55.5, 31.5, 12.1; FTIR (KBr) (ν cm−1): 3437, 2932,
1504, 1315, 1247, 1181, 1123, 1078, 752, 682; HRMS m/z (MALDI) calcd
for C32H28N3O3S [M + H]+ 534.1846; found: 534.1836.
(4RS,5SR) -N, N-Dimethyl- 4- [3-methyl-1,6 -diphenyl-5-
(phenylsulfonyl)-4,5-dihydro-1H-pyrazolo[3,4-b]pyridin-4-yl]aniline
(4e): Yellow solid; 186 mg, yield 68%; m.p. 132–134 °C; 1H NMR (CDCl3,
300 MHz) δ 7.95 (d, J = 8.3 Hz, 2H), 7.65–7.38 (m, 11H), 7.28–7.17 (m, 2H),
6.91 (d, J = 8.8 Hz, 2H), 6.56 (d, J = 8.7 Hz, 2H), 5.09 (s, 1H), 4.98 (s, 1H),
2.87 (s, 6H), 2.18 (s, 3H); 13C NMR (CDCl3, 75 MHz) δ 156.9, 149.8, 145.2,
In summary, we have developed an efficient method for the
synthesis of novel 4,5-dihydro-1H-pyrazolo[3,4-b]pyridines,
instead of the commonly reported 4,7-dihydro-1H-pyrazolo[3,4-b]
pyridines, from 5-aminopyrazoles, aldehydes and β-ketosulfones in
refluxing acetic acid. The phenylsulfonyl group was successfully
introduced into the nitrogen-containing heterocyclic molecules. All
these newly synthesised compounds were characterised by means
of 1H NMR, 13C NMR, IR and MS. The structure of 4a was further
confirmed by X-ray single-crystal diffraction analysis.
Experimental
All reactants were commercially available and used without further
purification. Melting points were determined using an X-4 Melting-point
Apparatus (KWF Sci-Tech Development Company Limited, Beijing,
1
China) and are uncorrected. H and 13C NMR were recorded in CDCl3
using Bruker AV 300 MHz spectrometers at 300 and 75 MHz, respectively.
Chemical shifts are reported relative to TMS (internal standard). IR spectra
were recorded in KBr on a Nicolet 5700 FTIR spectrometer. Mass spectra
were recorded on an Ultraflex TOF/TOF (MALDI) or a LCQ Advantage
MAX (ESI). The CHN microanalyses were carried out with a PerkinElmer
2400 Elemental Analyzer. Flash column chromatography was performed
on 200–300 mesh silica gel.
Synthesis of 4; general procedure
A mixture of aldehydes (1, 0.5 mmol), 5-aminopyrazoles (2, 0.5 mmol)
and β-ketosulfones (3, 0.5 mmol) was heated in acetic acid (5 mL) below
120 °C. After the reaction was completed (6~10 h, monitored by TLC), the
mixture was slowly cooled to room temperature and purified by column
chromatography using petroleum ether–ethyl acetate as the eluent to deliver
the desired products 4.
(4RS,5SR)-3-Methyl-1,4,6-triphenyl-5-(phenylsulfonyl)-4,5-dihydro-
1H-pyrazolo[3,4-b]pyridine (4a): Yellow solid; 169 mg, yield 67%;
m.p. 212–214 °C; 1H NMR (CDCl3, 300 MHz) δ 7.93 (d, J = 7.0 Hz, 2H),
7.54–7.39 (m, 9H), 7.30–7.18 (m, 7H), 7.09–7.06 (m, 2H), 5.18 (s, 1H), 4.99
(s, 1H), 2.18 (s, 3H); 13C NMR (CDCl3, 75 MHz) δ 156.9, 145.2, 139.3,
138.4, 137.0, 136.4, 134.2, 131.7, 129.3, 129.0, 128.7, 128.6, 128.2, 128.0,
127.8, 126.8, 126.2, 121.8, 104.3, 69.0, 37.1, 12.0; FTIR (KBr) (ν cm−1):
3438, 2924, 1494, 1318, 1184, 1125, 1077, 757, 681; ESI-MS: m/z 504.02 [M
+ H]+. Anal. calcd for C31H25N3O2S: C, 73.93; H, 5.00; N, 8.34; found: C,
74.05; H, 5.01; N, 8.32.
3,5-Dimethyl-1,4,7-triphenyl-1,7-dihydrodipyrazolo[3,4-b:4',3'-e]
pyridine (4a'):11 Yellow solid; 25 mg, yield 12%; 1H NMR (CDCl3,

JOURNAL OF CHEMICAL RESEARCH 2016 593
145.0, 138.5, 137.2, 136.6, 134.1, 131.5, 129.0, 128.63, 128.56, 128.3, 127.9,
127.6, 126.0, 121.8, 113.0, 105.1, 69.3, 40.5, 36.4, 12.0; FTIR (KBr) (ν cm−1):
3429, 2918, 2302, 1618, 1510, 1126, 1074, 761, 686; HRMS m/z (MALDI)
calcd for C33H31N4O2S [M + H]+ 547.2162; found: 547.2157.
128.0, 127.1, 126.7, 126.6, 122.2, 102.8, 69.4, 38.1; FTIR (KBr) (ν cm−1):
3440, 3059, 2927, 1493, 1447, 1310, 1183, 1128, 1076, 756, 686, 535; HRMS
m/z(MALDI) calcd for C36H28N3O2S [M + H]+ 566.1897; found: 566.1901.
(4RS,5SR)-3,6-Dimethyl-1,4-diphenyl-5-(phenylsulfonyl)-4,5-dihydro-
1H-pyrazolo[3,4-b]pyridine (4m): Yellow solid; 112 mg, yield 51%;
m.p. 155–157 °C; 1H NMR (CDCl3, 300 MHz) δ 7.64 (d, J = 8.4 Hz, 2H),
7.45–7.33 (m, 5H), 7.31–7.24 (m, 6H), 7.01 (d, J = 7.8 Hz, 2H), 4.88 (s, 1H),
4.10 (s, 1H), 2.49 (s, 3H), 2.06 (s, 3H); 13C NMR (CDCl3, 75 MHz) δ 161.4,
145.0, 144.2, 139.7, 138.3, 136.4, 134.3, 129.3, 128.8, 128.6, 128.1, 127.8,
126.8, 126.2, 121.9, 103.3, 73.3, 36.7, 28.4, 11.8; FTIR (KBr) (ν cm−1):
3435, 3057, 2925, 1593, 1498, 1438, 1308, 1122, 1076, 759, 689; HRMS m/z
(MALDI) calcd for C26H24N3O2S [M + H]+ 442.1584; found: 442.1587.
3-Methyl-1,4-diphenyl-6-(phenylsulfonylmethyl)-1H-pyrazolo[3,4-b]
pyridine (4m'): White solid; 44 mg, yield 20%; m.p. 236–238 °C; 1H NMR
(CDCl3, 300 MHz) δ 8.35 (d, J = 7.7 Hz, 2H), 7.94 (d, J = 7.9 Hz, 2H), 7.75
(d, J = 7.2 Hz, 2H), 7.69–7.64 (m, 1H), 7.56–7.46 (m, 7H), 7.33–7.28 (m,
1H), 7.21 (s, 1H), 4.78 (s, 2H), 2.70 (s, 3H); 13C NMR (CDCl3, 75 MHz) δ
156.4, 151.5, 141.6, 139.4, 138.3, 137.7, 134.3, 132.1, 129.7, 129.3, 129.0,
128.8, 128.7, 127.4, 125.6, 121.0, 117.4, 114.9, 59.3, 15.1; FTIR (KBr) (ν
cm−1): 3436, 2923, 1592, 1497, 1413, 1141, 1083, 752, 686; HRMS m/z
(MALDI) calcd for C26H22N3O2S [M + H]+ 440.1427; found: 440.1429.
(4RS,5SR) -3-Methyl- 4- (2-nitrophenyl) -1,6-diphenyl-5-
(phenylsulfonyl)-4,5-dihydro-1H-pyrazolo[3,4-b]pyridine (4f): Yellow
solid; 153 mg, yield 56%; m.p. 230–232 °C; 1H NMR (CDCl3, 300 MHz)
δ 7.95 (d, J = 7.9 Hz, 1H), 7.86 (d, J = 7.4 Hz, 2H), 7.63 (d, J = 7.8 Hz, 2H),
7.51–7.20 (m, 13H), 6.78 (d, J = 7.3 Hz, 1H), 5.73 (s, 1H), 5.25 (s, 1H), 2.14
(s, 3H); 13C NMR (CDCl3, 75 MHz) δ 157.8, 148.3, 146.7, 145.2, 138.4,
137.4, 136.7, 134.1, 133.7, 132.5, 131.9, 130.3, 129.1, 129.0, 128.8, 128.7,
128.2, 126.5, 125.2, 122.0, 103.3, 67.6, 31.9, 12.0; FTIR (KBr) (ν cm−1):
3423, 1509, 1338, 1182, 1127, 1079, 751, 689, 531; HRMS m/z (MALDI)
calcd for C31H25N4O4S [M + H]+ 549.1591; found: 549.1590.
(4RS,5SR) -4- (4-Chlorophenyl) -3-methyl-1,6-diphenyl-5-
(phenylsulfonyl)-4,5-dihydro-1H-pyrazolo[3,4-b]pyridine (4g): Yellow
solid; 154 mg, yield 57%; m.p. 213–215 °C; 1H NMR (CDCl3, 300 MHz)
δ 7.93 (d, J = 8.4 Hz, 2H), 7.54–7.39 (m, 9H), 7.32–7.18 (m, 6H), 7.01 (d,
J = 8.4 Hz, 2H), 5.16 (s, 1H), 4.92 (s, 1H), 2.17 (s, 3H); 13C NMR (CDCl3,
75 MHz) δ 156.8, 145.1, 138.4, 137.7, 136.8, 136.3, 134.3, 133.8, 131.8, 129.5,
129.0, 128.8, 128.6, 128.3, 128.2, 128.0, 126.3, 121.8, 103.8, 68.9, 36.6, 12.0;
FTIR (KBr) (ν cm−1): 3443, 2922, 2335, 1494, 1183, 1123, 1080, 757, 680;
HRMS m/z (MALDI) calcd for C31H25ClN3O2S [M + H]+ 538.1351; found:
538.1359.
Single crystal X-ray crystallography
The X-ray data were collected on a Bruker SMART APEX CCD area-
detector diffractometer using graphite monochromated Mo Ka radiation
(λ = 0.71073 Å) at 296(2) K. The structures were solved by direct methods
with the SHELXS-97 program and refinements on F2 were performed
with the SHELXL-97 program using full-matrix least-squares techniques.
CCDC 1483380 contains the supplementary data for this paper. The data
can be obtained free of charge from the Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif.
(4RS,5SR) -4- (4-Bromophenyl) -3-methyl-1,6-diphenyl-5-
(phenylsulfonyl)-4,5-dihydro-1H-pyrazolo[3,4-b]pyridine (4h): Yellow
solid; 151 mg, yield 52%; m.p. 204–206 °C; 1H NMR (CDCl3, 300 MHz)
δ 7.93 (d, J = 7.0 Hz, 2H), 7.54–7.35 (m, 11H), 7.32–7.17 (m, 4H), 6.95 (d,
J = 8.4 Hz, 2H), 5.14 (s, 1H), 4.92 (s, 1H), 2.17 (s, 3H); 13C NMR (CDCl3,
75 MHz) δ 156.8, 145.1, 138.3, 138.2, 136.8, 136.3, 134.3, 132.4, 131.8,
129.0, 128.8, 128.6, 128.2, 128.0, 126.3, 121.9, 121.8, 103.7, 68.8, 36.6, 12.0;
FTIR (KBr) (ν cm−1): 3397, 1493, 1316, 1185, 1126, 1076, 825, 758, 684;
HRMS m/z (MALDI) calcd for C31H25BrN3O2S [M + H]+ 582.0845; found:
582.0847.
Crystal data for compound (4a). C31H25N3O2S,
M = 503.60,
crystal system: monoclinic, space group P2(1)/c, lattice parameters:
a = 9.624(4) Å, b = 18.149(8) Å, c = 14.421(7) Å, α = 90°, β = 96.387(9)°,
γ = 90°, V = 2503.2(19) Å3, Z = 4, Dc = 1.336 g·cm−3, F000 = 1056, final R
indices [I> 2sigma(I)]: R1 = 0.0500, wR2 = 0.1316.
(4RS,5SR)-4-(Furan-2-yl)-3-methyl-1,6-diphenyl-5-(phenylsulfonyl)-
4,5-dihydro-1H-pyrazolo[3,4-b]pyridine (4i): Yellow solid; 123 mg, yield
50%; m.p. 149–150 °C; 1H NMR (CDCl3, 300 MHz) δ 7.96 (d, J = 8.0 Hz,
2H), 7.44–7.28 (m, 11H), 7.22–7.08 (m, 6H), 6.10–6.08 (m, 1H), 5.75–5.74
(m, 1H), 5.19 (s, 2H), 2.25 (s, 3H); 13C NMR (CDCl3, 75 MHz) δ 157.1,
151.4, 145.2, 144.9, 142.8, 138.3, 136.8, 136.5, 134.2, 131.8, 129.0, 128.8,
128.5, 128.3, 128.0, 126.2, 121.9, 110.4, 106.8, 101.9, 65.0, 31.6, 12.0; FTIR
(KBr) (ν cm−1): 3438, 2924, 1502, 1439, 1307, 1127, 1076, 740, 683; HRMS
m/z (MALDI) calcd for C29H24N3O3S [M + H]+ 494.1533; found: 494.1529.
(4RS,5SR)-3-Methyl-1,6-diphenyl-5-(phenylsulfonyl)-4-(thiophen-
2-yl)-4,5-dihydro-1H-pyrazolo[3,4-b]pyridine (4j): Yellow solid;
143 mg, yield 56%; m.p. 213–215 °C; 1H NMR (CDCl3, 300 MHz) δ 8.01
(d, J = 6.8 Hz, 2H), 7.51–7.37 (m, 9H), 7.30–7.16 (m, 4H), 7.10 (d, J = 5.0 Hz,
1H), 6.85–6.82 (m, 1H), 6.77–6.76 (m, 1H), 5.45 (s, 1H), 5.14 (s, 1H), 2.29
(s, 3H); 13C NMR (CDCl3, 75 MHz) δ 157.0, 145.0, 144.5, 142.8, 138.4,
136.9, 136.4, 134.3, 131.8, 129.0, 128.8, 128.5, 128.3, 128.0, 127.3, 126.2,
125.1, 124.5, 121.9, 104.7, 68.9, 32.8, 12.0; FTIR (KBr) (ν cm−1): 3438,
3059, 2922, 1497, 1444, 1305, 1179, 1122, 1075, 757, 691, 526; HRMS m/z
(MALDI) calcd for C29H24N3O2S2 [M + H]+ 510.1304; found: 510.1305.
(4RS,5SR)-3-Methyl-1,6-diphenyl-5-(phenylsulfonyl)-4-propyl-4,5-
dihydro-1H-pyrazolo[3,4-b]pyridine (4k): Yellow oil; 70 mg, yield 30%;
1H NMR (CDCl3, 300 MHz) δ 8.05 (d, J = 7.4 Hz, 2H), 7.48–7.39 (m,
5H), 7.33–7.28 (m, 4H), 7.19–7.14 (m, 2H), 7.10–7.05 (m, 2H), 4.72 (s, 1H),
3.83–3.78 (m, 1H), 2.23 (s, 3H), 1.32–1.28 (m, 4H), 0.84–0.82 (m, 3H);
13C NMR (CDCl3, 75 MHz) δ 157.1, 144.8, 144.4, 138.4, 137.1, 136.8, 134.0,
131.7, 128.8, 128.5, 128.3, 127.8, 126.0, 121.8, 105.6, 66.4, 36.9, 31.8, 19.6,
13.9, 12.3; FTIR (KBr) (ν cm−1): 3442, 2925, 1632, 1500, 1438, 1310, 1126,
1077, 757, 682; HRMS m/z (MALDI) calcd for C28H28N3O2S [M + H]+
470.1897; found: 470.1899.
Acknowledgment
We gratefully acknowledge the support from the Educational
Commission of Hubei Province (No. B2015132).
Electronic Supplementary Information
The 1H NMR and 13C NMR spectra of compounds 4 are available
through:
stl.publisher.ingentaconnect.com/content/stl/jcr/supp-data
Received 3 June 2016; accepted 27 July 2016
Paper 1604127 doi: 10.3184/174751916X14737765008687
Published online: 23 September 2016
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