Copper-Mediated C-H Amination of Imidazopyridines with N-Fluorobenzenesulfonimide

Article abstract of DOI:10.1021/acs.joc.8b02348

A copper-mediated direct C3 amination of imidazopyridines has been disclosed under additive-free conditions in short reaction times. This methodology utilizes commercially available N-fluorobenzenesulfonimide (NFSI) as the amino source, which exhibits bro

Full text of DOI:10.1021/acs.joc.8b02348

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Article
Copper-Mediated C-H Amination of
Imidazopyridines with N-Fluorobenzenesulfonimide
Shuai Lu, Lu-Lu Tian, Tian-Wei Cui, Yu-Shen Zhu, Xinju Zhu, Xin-Qi Hao, and Mao-Ping Song
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.8b02348 • Publication Date (Web): 23 Oct 2018
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The Journal of Organic Chemistry
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Copper-Mediated C-H Amination of Imidazopyridines with N-
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Fluorobenzenesulfonimide
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Shuai Lu, Lu-Lu Tian, Tian-Wei Cui, Yu-Shen Zhu, Xinju Zhu*, Xin-Qi Hao, and Mao-Ping Song*
College of Chemistry and Molecular Engineering, Zhengzhou University, No. 100 of Science Road, Zhengzhou, Henan
450001, P. R. China
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Supporting Information
ABSTRACT: A copper-mediated direct C3 amination of imidazopyridines has been disclosed under additive-free conditions in
short reaction times. This methodology utilizes commercial available N-fluorobenzenesulfonimide (NFSI) as the amino source,
which exhibits broad substrate scope and good functional group tolerance. The obtained C3-aminated imidazopyridines can under-
go further desulfonylation transformations. Control experiments suggest that this reaction probably proceed via a free radical mech-
anism. Moreover, NFSI also shows potential application in C-H fluorination of imidazopyridines.
group achieved oxidative C-H amination of imidazopyridines
in the presence of (Diacetoxy)iodobenzene.14b At the same
time, the Sun group reported a visible light induced C-H sul-
INTRODUCTION
Aminoarenes are ubiquitous scaffolds due to their high syn-
thetic value and wide application in various natural products,
pharmaceuticals, functional materials, and ligands for organ-
ometallic catalysis.1 Accordingly, intensive efforts have been
devoted to prepare nitrogen-containing compounds in the past
decades.2 The conventional approach to amines involved nitra-
tion/reduction sequence, amination of aryl halide, including
Ullmann-Goldberg, Buchwalk-Hartwig, and Chan-Evans-Lam
Amination.3 Other typical methods employed electrophilic
nitrogen strategy between oxidized nitrogen reagents and car-
bon necleophiles.4 Recently, significant achievements have
been made in the C-H amination, which avoids prefunctionali-
zation of coupling partners, and thus being more efficient and
environmental benign.5 Various electrophilic amination rea-
gents, including azides,6a dioxazolones,6b,c chloroamines,6d
azodicarboxylates,6e and hydroxyamines6f,g have been success-
fully utilized to achieve C-H amination in the presence of tran-
sition-metal catalysts.
On the other hand, imidazo[1,2-a]pyridine moiety is an im-
portant class of N-heterocycles present in biologically active
pharmaceuticals and optoelectronics.7 In recent years, there is
an increasing interest in the preparation and functionalization
of imidazopyridines.8 Up to now, tremendous efforts have
been made to construct C-C,9 C-S,10 C-O,11a C-F,11b and C-P12
bonds via direct C3 functionalizations. However, the for-
mation of C-N bond is less investigated.13,14 Recently, the
Gryko group prepared polycyclic imidazopyridines via oxida-
tive intramolecular C-H amination.14a Subsequently, the Hajra
Scheme 1 Methodologies for C-H amination using NFSI.
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c
d
fonamidation methodology.14c Despite the above achievements,
the diversity of amino source is still limited.
yields. [(MeCN)4Cu]BF4 (0.5 equiv). [(MeCN)4Cu]BF4 (1.0
equiv). eUnder Ar. fUnder O2. g[(MeCN)4Cu]PF6 (1.0 equiv).
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As a commercial available amination reagent, N-
fluorobenzenesulfonimide (NFSI) has attracted much at-
tention since the pioneering work of the Zhang and other
group.15 Up to now, great achievements have been made
for difunctionalization of olefins, such as cyanoamination,16a,b
fluoroamination,16c,d alkoxyamination,16e carboamination,16f
and other transformations.16g,h Meanwhile, NFSI could also
react with allenes,17a alkynes,17b benzylic carbon,17c and diazo-
carbonyl compounds17d to accomplish C-H amination. Notably,
the Zhang, the Ritter, the Itami, and other groups have also
reported C-H amination of (hetero)arenes in the presence of
Pd, Cu, Fe, and metal-free conditions (Scheme 1a-d).18,19
In our previous work, our group have achieved C-H tosyl-
methylation,9c sulfonylation and sulfenylation,10d and cya-
nation20d of imdazopyridines. Inspired by the above achieve-
ments and our previous work,20 we herein firstly developed
direct C-H amination of imidazopyridines using NFSI as the
nitrogen source (Scheme 1e).
exhibited the best performance to afford the desired product
2a in 21% yield (Table 1, entry 4). The combination of addi-
tional ligands led to decreased efficiency (see the Supporting
Info). Subsequently, the catalytic loading of [(MeCN)4Cu]BF4
was investigated, indicating 1 equiv of Cu salt was required to
provide 2a in 82% yield (Table 1, entry 7). Next, other sol-
vents were screened (Table 1, entries 8-11), which showed
inferior efficiency compared with DCE. To our delight, the
amination of imidazopyridine 1a could still be efficiently
achieved in 10 min (Table 1, entry 13). Further shortening the
reaction time to 5 min resulted in decreased yield (Table 1,
entry 14). When the reaction was carried out under argon or
oxygen atmosphere, decreased yields were observed (Table 1,
entries 15 and 16). We also tested the reaction in the presence
of 1 equiv of [(MeCN)4Cu]PF6, which only delivered 2a in
73% yield (Table 1, entry 17). The structure of 2a was further
confirmed by X-ray diffraction (see the Supporting Info).
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Scheme 2 Substrate scope of 2-phenyllimidazo[1,2-
RESULTS AND DISCUSSION
α
]pyridinesa
2-phenylimidazo[1,2-α]pyridine 1a (0.2 mmol) and NFSI (0.4
mmol) was selected as model substrates to optimize the reac-
tion conditions (Table 1). Initially, different copper salts (20
mol%) was examined in DCE at 100 oC, and [(MeCN)4Cu]BF4
Table 1 Optimization of reaction conditionsa
Entry
Copper salts
Solvent
Time
Yield
[%]b
13
1
2
CuCl
DCE
DCE
DCE
DCE
DCE
DCE
DCE
toluene
dioxane
MeCN
THF
12 h
12 h
CuBr
11
13
21
20
38
82
trace
34
30
18
82
84
73
73
64
73
3
CuI
12 h
4
[(MeCN)4Cu]BF4
[(MeCN)4Cu]PF6
[(MeCN)4Cu]BF4
[(MeCN)4Cu]BF4
[(MeCN)4Cu]BF4
[(MeCN)4Cu]BF4
[(MeCN)4Cu]BF4
[(MeCN)4Cu]BF4
[(MeCN)4Cu]BF4
[(MeCN)4Cu]BF4
[(MeCN)4Cu]BF4
[(MeCN)4Cu]BF4
[(MeCN)4Cu]BF4
[(MeCN)4Cu]PF6
12 h
5
6c
7d
8d
12 h
12 h
12 h
12 h
9d
12 h
10d
11d
12d
13d
14d
15d, e
16d, f
17g
12 h
12 h
aReaction conditions:
1 (0.2 mmol), NFSI (0.4 mmol),
DCE
DCE
DCE
DCE
DCE
DCE
0.5 h
10 min
5 min
10 min
10 min
10 min
[(MeCN)4Cu]BF4 (0.2 mmol), DCE (1 mL), under air,
100 oC, 10 min. b1a (6.0 mmol), NFSI (12.0 mmol).
With the optimized condition in hand (Table 1, entry 13),
the substrate scope of 2-phenylimidazo[1,2-α]pyridines was
investigated. Initially, various substitutions on the benzene
ring at the C2 position of imidazo[1,2-α]pyridines was exam-
ined (Scheme 2). In general, both electron-donating (R = OMe,
t-Bu, Et, Me) and electron-withdrawing groups (F, Cl, Br, I,
CF3) at the para-, meta-, and ortho-positions proceeded
aReaction conditions: 1a (0.2 mmol), NFSI (0.4 mmol), Cu
o
b
salt (20 mol%), solvent (1 mL), under air, 100 C. Isolated
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o
smoothly to provide the aminated products in 40-87% yields.
yields in the presence of KOH in MeOH at 60 C for 1 h
(Scheme 4).
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Compared with strong electron-withdrawing groups (R1 =
CF3), decreased yields were obtained for OMe- substituted
products 2b (51%) and 2g (36%). Next, the effect of substitu-
tions at the C6, C7, and C8 position on the amination reactivi-
ty was evaluated. Similarly, a wide range of functional groups,
including alkyl (1r and 1aa), halogen (1s-v and 1ab-ac), CF3
(1w and 1ad), and ester (1x), were well tolerated under the
current catalytic system. The compatibility of halogen-
substituted imidazopyridines could be utilized for further
transformations. However, low yields were obtained for CN
(2y, 17%), OMe (2z, 20%), and C8-substituted imidaz-
opyridines (2af, 39%; 2ag, 22%; and 2ah, 36%). Finally, di-
substituted 2-phenylimidazo[1,2-α]pyridines could also react
with NFSI to provide the corresponding products 2ai-al in 36-
74% yields. To uncover the synthetic potential for this proto-
col, a gram-scale production of amination of 1a was also con-
ducted, furnishing the desired product 2a in 79% yield.
Scheme 4 Desulfonylation of aminated imidazo[1,2-
α
]pyridinesa
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To further extend the scope of amination reaction, we
next explored various imidazoheterocycles as the reac-
tants (Scheme 3). Compared with 2-phenylimidazo[1,2-
α]pyridines, decreased yields were observed for 4a and 4b
probably due to the steric hindrance between N(SO2Ph)2
and substrates. Nevertheless, imidazopyridazine and im-
idazothiazole were successfully underwent C3-amination
to deliver products 4c and 4d in 73% and 59% yields,
respectively. For substrates with 2-furan and 2-thiophene
aReaction conditions:
2 (0.1 mmol), KOH (8 equiv),
MeOH (2.5 mL), 60 oC, 1 h.
,
Apart from acting as amination reagent, NFSI can be
also utilized as the fluoride source.22 Recently, the Sun
group have reported fluorination of imidazopyridines was
also achieved using selectfluor as the electrophilic fluori-
nating reagent.11b Inspired by the above work, fluorinated
product
6 was isolated in 36% yield under preliminary
substitutions, a mixture of 4e, 4e’ and 4f, 4f’ was isolated
in low yields, respectively.
investigation (Scheme 5). Further optimization of condi-
tions is currently in progress in our lab.
Scheme 3 Substrate scope of imidazoheterocyclesa
Scheme 5 Substrate scope of 2-phenyllimidazo[1,2-
α
]pyridinesa
aReaction conditions: 1a (0.2 mmol), NFSI (0.3 mmol),
CuO (20 mol%), DCE (2 mL), 80 oC, 12 h, under air.
To explore the reaction mechanism, a set of control ex-
periments were performed (Scheme 6). The aminated
product could not be detected in the absence of
[(MeCN)4Cu]BF4, indicating the necessity of Cu salt. Un-
der the optimized conditions, addition of a radical scav-
enger TEMPO (1 equiv) completely suppressed the ami-
nation reaction. Also, When 1 equiv BHT was added, the
aminated product 2a was isolated in only 16% yield. The-
se results suggest that the amination transformation is
likely to proceed via a radical pathway.
aReaction conditions:
3 (0.2 mmol), NFSI (0.4 mmol),
On the basis of above discussion and relevant litera-
tures,16a,19d,23 a plausible amination mechanism was pro-
[(MeCN)4Cu]BF4 (0.2 mmol), DCE (1 mL), under air,
100 oC, 10 min. b2 h.
posed
[(MeCN)4Cu]BF4 with NFSI provides L4CuIII(BF4)F(NSI)
, which is in equilibrium with Cu(II)-stabilized species
. Subsequently, radical addition of between Cu(II) spe-
cies and imidazopyridine 1a selectively produces
(Scheme
7).
Initially,
oxidation
of
Encouraged by the above results, we next sought to in-
vestigate desulfonylation of obtained products according
to previous literatures.18a,21 However, complete desul-
fonylation of aminated products was proved to be unsuc-
cessful under various conditions. Nevertheless,
A
B
B
Scheme 6 Control experiments
monodesulfonylated products
5 was obtained in 48-88%
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coupling constants (J) in hertz (Hz). HRMS were determined
on a Q-Tof Micro MS/MS System ESI spectrometer.
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General procedure for the C-H amination of imidaz-
opyridines. To a 15 mL sealed tube were added imidazo[1,2-
α]pyridines 1 or imidazoheterocycles 3 (0.2 mmol), NFSI (0.4
mmol, 126 mg), and [(MeCN)4Cu]BF4 (0.2 mmol, 63 mg) in
DCE (1 mL) under air. The reaction mixture was stirred at
100 °C for 10 min and then cooled to room temperature. After
removal of solvent under reduced pressure, the residue was
purified by preparative TLC on silica gel plates using petrole-
um ether/EtOAc as the eluent to give the corresponding prod-
ucts 2 or 4.
General procedure for desulfonylation of C3-aminated
imidazopyridines. To a 15 mL sealed tube were added 2a or
2h or 2q or 2aa (0.1 mmol), KOH (0.4 mmol, 42.5 mg) in
MeOH (2.5 mL) under air. The reaction mixture was heated at
60 °C for 1 h and then cooled to room temperature. After re-
moval of solvent under reduced pressure, the residue was puri-
fied by preparative TLC on silica gel plates using petroleum
ether/EtOAc as the eluent to give the target product 5.
General procedure for the C-H fluorination of imidaz-
opyridine 1a. To a 15 mL sealed tube were added 2-
phenylimidazo[1,2-α]pyridine 1a (0.2 mmol, mg), NFSI (0.3
mmol, 94.6 mg), CuO (0.04 mmol, 3.2 mg), and Cs2CO3 (0.4
mmol, 130.3 mg) in DCE (2 mL) under air. The reaction mix-
ture was heated at 80 °C for 12 h and then cooled to room
temperature. After removal of solvent under reduced pressure,
the residue was purified by preparative TLC on silica gel
plates using petroleum ether: EtOAc = 2: 1 as the eluent to
give the target product 6.
C3-functionalized intermediate
Next, imidazopyridine radical
generate imidazopyridine cation
C
C
and Cu(II) species
is oxidized by NFSI to
, bis-sulfonylamidyl
radical, and F- through a SET process.19c Finally, the
D.
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E
deprotonation of
HF.
E afforded the desired product 2a and
Scheme 7 Proposed mechanism
N-(2-phenylimidazo[1,2-a]pyridin-3-yl)-N-
(phenylsulfonyl)benzenesulfonamide (2a). Yellow solid (82.3
o
1
CONCLUSION
mg, 84%), m.p. = 107-108 C. H NMR (600 MHz, CDCl3) δ
7.92 (d, J = 7.9 Hz, 4H), 7.72 (d, J = 7.7 Hz, 2H), 7.64 (d, J =
8.9 Hz, 1H), 7.58 (t, J = 7.4 Hz, 2H), 7.51 (d, J = 6.8 Hz, 1H),
7.40 (t, J = 7.7 Hz, 4H), 7.29-7.28 (m, 1H), 7.17 (t, J = 7.3 Hz,
1H), 7.11 (t, J = 7.6 Hz, 2H), 6.65 (t, J = 6.8 Hz, 1H). 13C{1H}
NMR (150 MHz, CDCl3) δ 145.6, 144.5, 139.1, 134.6, 131.8,
129.1, 129.0, 128.4, 128.1, 127.5, 126.8, 123.9, 118.0, 112.6,
In conclusion, we have developed a facile and efficient
strategy for regioselective C3 amination of imidazo[1,2-
α]pyridine with NFSI in the presence of [(MeCN)4Cu]BF4.
Under the optimized conditions, a broad range of func-
tionalities were well tolerated to effieienty deliver the
desired aminated products, which could further undergo
desulfonylation to produce the corresponding benzenesul-
fonamide derivatives. The current methodology was fea-
tured with several advantages such as operational simplic-
ity, short reaction time, and broad substrate scope. More-
over, the gram-scale production of aminated imidaz-
opyridine, as well as potential fluorination of imidaz-
opyridine, probably possesses application in medicinal
chemistry.
+
111.1. HRMS (positive ESI): [M+H]+ calcd for C25H20N3O4S2 :
490.0890, found 490.0882.
N-(2-(2-methoxyphenyl)imidazo[1,2-a]pyridin-3-yl)-N-
(phenylsulfonyl)benzenesulfonamide (2b). Yellow solid (53.2
o
1
mg, 51%), m.p. = 203-204 C. H NMR (600 MHz, CDCl3) δ
7.87 (d, J = 7.1 Hz, 4H), 7.67-7.63 (m, 2H), 7.56-7.55 (m, 3H),
7.36 (t, J = 6.6 Hz, 4H), 7.26-7.20 (m, 2H), 6.82 (t, J = 6.5 Hz,
1H), 6.70-6.69 (m, 2H), 3.67 (s, 3H). 13C{1H} NMR (150
MHz, CDCl3) δ 157.5, 145.0, 144.2, 139.0, 134.2, 131.3,
130.1, 128.8, 128.8, 126.4, 123.9, 121.1, 119.9, 118.2, 112.5,
112.1, 110.7, 55.3. HRMS (positive ESI): [M+H]+ calcd for
EXPERIMENTAL SECTION
+
C26H22N3O5S2 : 520.0995, found 520.1001.
General Experimental Details. Unless otherwise indicated, all
the starting materials and reagents were commercially availa-
ble and used without further purification. Imidazo[1,2-
α]pyridines 1 and imidazoheterocycles 3 were prepared ac-
cording to previous literatures.7a, 24 All reactions were carried
out using 15 mL sealed tube. Melting points were measured on
N-(phenylsulfonyl)-N-(2-(o-tolyl)imidazo[1,2-a]pyridin-3-
yl)benzenesulfonamide (2c). Yellow solid (48.2 mg, 47%), m.p.
o
1
= 193-194 C. H NMR (600 MHz, CDCl3) δ 7.78 (d, J = 7.3
Hz, 4H), 7.64-7.56 (m, 4H), 7.45 (d, J = 7.0 Hz, 1H), 7.36 (t, J
= 7.0 Hz, 4H), 7.28-7.26 (m, 1H), 7.19 (t, J = 7.0 Hz, 1H),
7.09 (d, J = 7.0 Hz, 1H), 7.03 (t, J = 6.8 Hz, 1H), 6.68 (t, J =
5.6 Hz, 1H), 2.15 (s, 3H). 13C{1H} NMR (150 MHz, CDCl3) δ
147.8, 144.2, 138.9, 138.1, 134.3, 131.4, 130.4, 129.7, 129.0,
128.7, 126.5, 125.1, 124.0, 118.0, 112.7, 111.8, 20.5. HRMS
1
a melting point apparatus. H, 13C and 19F NMR spectra were
recorded on Bruker DPX 400 or Bruker DPX 600 instruments
using TMS as an internal standard. Data are reported as fol-
lows: chemical shift (δ ppm), multiplicity (s = single, d = dou-
blet, t = triplet, q = quartet, m = multiplet), integration, and
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(positive ESI): [M+H]+ calcd for C26H22N3O4S2 : 504.1046,
found 504.1051.
8.2 Hz, 4H), 7.30-7.26 (m, 1H), 7.14-7.11 (m, 1H), 7.03 (t, 7.8
Hz, 1H), 6.69 (td, J = 6.8, 1.0 Hz, 1H). 13C{1H} NMR (100
MHz, CDCl3) δ 144.5, 144.0, 138.7, 134.8, 134.1, 133.7,
129.4, 129.2, 128.9, 128.5, 127.4, 127.2, 125.6, 124.0, 118.0,
113.0, 111.3. HRMS (positive ESI): [M+H]+ calcd for
1
2
3
4
5
6
7
8
N-(2-(2-fluorophenyl)imidazo[1,2-a]pyridin-3-yl)-N-
(phenylsulfonyl)benzenesulfonamide (2d). Green solid (75.6
o
1
mg, 75%), m.p. = 163-164 C. H NMR (600 MHz, CDCl3) δ
7.91 (d, J = 7.5 Hz, 4H), 7.72-7.65 (m, 3H), 7.56 (t, J = 7.0 Hz,
2H), 7.39 (t, J = 7.3 Hz, 4H), 7.30 (t, J = 7.6 Hz, 1H), 7.19 (m,
1H), 6.97 (t, J = 7.1 Hz, 1H), 6.86 (t, J = 9.2 Hz, 1H), 6.73 (t,
J = 6.4 Hz, 1H). 13C{1H} NMR (150 MHz, CDCl3) δ 160.9,
159.2, 144.5, 142.2, 138.7, 134.6, 131.1, 130.4 (d, J = 8.1 Hz),
129.0, 128.9, 126.9, 124.1, 123.6 (d, J = 3.3 Hz), 120.3 (d, J =
12.8 Hz), 118.3, 116.0 (d, J = 21.7 Hz), 113.0, 112.2. 19F
NMR (565 MHz, CDCl3) δ -111.8. HRMS (positive ESI):
+
C25H19ClN3O4S2 : 524.0500, found 524.0503.
N-(2-(3-bromophenyl)imidazo[1,2-a]pyridin-3-yl)-N-
(phenylsulfonyl)benzenesulfonamide (2j). White solid (93.4
o
1
mg, 82%), m.p. = 191-192 C. H NMR (400 MHz, CDCl3) δ
7.92-7.90 (m, 4H), 7.83 (t, J = 1,7 Hz, 1H), 7.69-7.57 (m, 5H),
7.44-7.40 (m, 4H), 7.31-7.27 (m, 2H), 6.97 (t, J = 7.9 Hz, 1H),
6.70 (td, J = 6.8, 1.0 Hz, 1H). 13C{1H} NMR (100 MHz,
CDCl3) δ 144.6, 144.0, 138.8, 134.8, 134.0, 131.4, 130.4,
129.6, 129.2, 128.9, 127.2, 126.0, 124.0, 122.4, 118.0, 113.0,
111.3. HRMS (positive ESI): [M+H]+ calcd for
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17
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21
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23
24
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28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
[M+H]+ calcd for C25H19FN3O4S2 : 508.0796, found 508.0799.
N-(2-(2-chlorophenyl)imidazo[1,2-a]pyridin-3-yl)-N-
(phenylsulfonyl)benzenesulfonamide (2e). Yellow solid (70.1
+
+
C25H19BrN3O4S2 : 567.9995, found 567.9999.
o
1
mg, 67%), m.p. = 169-170 C. H NMR (600 MHz, CDCl3) δ
7.91 (d, J = 7.6 Hz, 4H), 7.75 (d, J = 7.3 Hz, 1H), 7.67 (d, J =
8.9 Hz, 1H), 7.62 (d, J = 6.5 Hz, 1H), 7.57 (t, J = 7.2 Hz, 2H),
7.40 (t, J = 7.4 Hz, 4H), 7.29 (t, J = 7.7 Hz, 1H), 7.24 (d, J =
7.8 Hz, 1H), 7.18 (t, J = 7.3 Hz, 1H), 7.14 (t, J = 7.3 Hz, 1H),
6.71 (t, J = 6.5 Hz, 1H). 13C{1H} NMR (150 MHz, CDCl3) δ
145.0, 144.2, 138.8, 134.4, 134.4, 131.4, 131.0, 130.1, 129.8,
129.1, 128.8, 126.8, 126.1, 123.9, 118.4, 113.0, 112.3. HRMS
N-(2-(4-(tert-butyl)phenyl)imidazo[1,2-a]pyridin-3-yl)-N-
(phenylsulfonyl)benzenesulfonamide (2k). White solid (87.7
o
1
mg, 80%), m.p. = 204-205 C. H NMR (600 MHz, CDCl3) δ
7.92 (d, J = 7.3 Hz, 4H), 7.68 (d, J = 7.7 Hz, 2H), 7.62 (d, J =
8.8 Hz, 1H), 7.54 (t, J = 6.5 Hz, 2H), 7.48 (d, J = 6.2 Hz, 1H),
7.37 (t, J = 7.0 Hz, 4H), 7.24 (t, J = 7.3 Hz, 1H), 7.12 (d, J =
7.7 Hz, 2H), 6.62 (t, J = 5.9 Hz, 1H), 1.29 (s, 9H). 13C{1H}
NMR (150 MHz, CDCl3) δ 151.2, 145.7, 144.5, 139.2, 134.6,
129.1, 129.0, 128.9, 127.2, 126.7, 125.0, 123.8, 117.9, 112.5,
110.8, 34.6, 31.2. HRMS (positive ESI): [M+H]+ calcd for
(positive ESI): [M+H]+ calcd for C25H19ClN3O4S2 : 524.0500,
+
found 524.0502.
+
N-(2-(2-bromophenyl)imidazo[1,2-a]pyridin-3-yl)-N-
(phenylsulfonyl)benzenesulfonamide (2f). White solid (45.4
C29H28N3O4S2 : 546.1516, found 546.1518.
N-(2-(4-ethylphenyl)imidazo[1,2-a]pyridin-3-yl)-N-
o
1
mg, 40%), m.p. = 184-185 C. H NMR (600 MHz, CDCl3) δ
7.93 (d, J = 7.2 Hz, 4H), 7.76 (d, J = 7.3 Hz, 1H), 7.68 (d, J =
8.8 Hz, 1H), 7.58 (s, 3H), 7.47 (d, J = 7.7 Hz, 1H), 7.41 (t, J =
7.1 Hz, 4H), 7.29 (t, J = 7.0 Hz, 1H), 7.20 (t, J = 6.9 Hz, 1H),
7.11 (t, J = 7.5 Hz, 1H), 6.70 (t, J = 5.9 Hz, 1H). 13C{1H}
NMR (150 MHz, CDCl3) δ 146.1, 144.0, 138.9, 134.4, 133.3,
132.8, 131.5, 130.0, 129.1, 128.8, 126.7, 126.7, 124.3, 123.9,
118.5, 112.9, 112.2. HRMS (positive ESI): [M+H]+ calcd for
(phenylsulfonyl)benzenesulfonamide (2l). White solid (71.6
o
1
mg, 69%), m.p. = 169-170 C. H NMR (400 MHz, CDCl3) δ
7.92-7.90 (m, 4H), 7.66-7.61 (m, 3H), 7.55 (t, J = 7.5 Hz, 2H),
7.48 (d, J = 6.9 Hz, 1H), 7.37 (t, J = 8.1 Hz, 4H), 7.26-7.22 (m,
1H), 6.93 (d, J = 8.3 Hz, 2H), 6.62 (td, J = 6.8, 0.9 Hz, 1H),
2.57 (q, J = 7.6 Hz, 2H), 1.22 (t, J = 7.6 Hz, 3H). 13C{1H}
NMR (100 MHz, CDCl3) δ 145.7, 144.5, 144.5, 139.1, 134.6,
129.2, 129.0, 129.0, 127.7, 127.5, 126.7, 123.8, 117.8, 112.6,
+
+
C25H19BrN3O4S2 : 567.9995, found 567.9999.
110.8, HRMS (positive ESI): [M+H]+ calcd for C27H24N3O4S2 :
N-(2-(3-methoxyphenyl)imidazo[1,2-a]pyridin-3-yl)-N-
518.1203, found 518.1205.
(phenylsulfonyl)benzenesulfonamide (2g). Yellow solid (37
N-(phenylsulfonyl)-N-(2-(p-tolyl)imidazo[1,2-a]pyridin-3-
yl)benzenesulfonamide (2m). White solid (85.6 mg, 85%), m.p.
o
1
mg, 36%), m.p. = 172-173 C. H NMR (600 MHz, CDCl3) δ
7.92 (d, J = 7.6 Hz, 4H), 7.64 (d, J = 8.9 Hz, 1H), 7.58 (t, J =
7.2 Hz, 2H), 7.47 (d, J = 6.5 Hz, 1H), 7.40 (t, J = 7.4 Hz, 4H),
7.36-7.35 (m, 2H), 7.28-7.27 (m, 1H), 7.06 (t, J = 7.7 Hz, 1H),
6.74 (d, J = 8.0 Hz, 1H), 6.65 (t, J = 6.2 Hz, 1H), 3.69 (s, 3H).
13C{1H} NMR (150 MHz, CDCl3) δ 159.3, 145.6, 144.5, 139.2,
134.6, 133.2, 129.1, 129.0, 129.0, 126.8, 123.8, 120.4, 118.0,
115.9, 112.7, 111.5, 111.2, 55.2. HRMS (positive ESI):
o
1
= 182-183 C. H NMR (400 MHz, CDCl3) δ 7.92-7.90 (m,
4H), 7.26-7.55 (m, 5H), 7.48 (d, J = 6.8 Hz, 1H), 7.38 (t, J =
8.2 Hz, 4H), 7.26-7.22 (m, 1H), 6.90 (d, J = 8.0 Hz, 2H), 6.61
(td, J = 6.8, 0.8 Hz, 1H), 2.28 (s, 3H). 13C{1H} NMR (150
MHz, CDCl3) δ 145.7, 144.5, 139.2, 138.2, 134.4, 129.0,
129.0, 128.8, 127.4, 126.7, 123.8, 117.8, 112.5, 110.8, 21.1.
+
HRMS (positive ESI): [M+H]+ calcd for C26H22N3O4S2 :
+
[M+H]+ calcd for C26H22N3O5S2 : 520.0995, found 520.0996.
504.1046, found 504.1050.
N-(2-(4-fluorophenyl)imidazo[1,2-a]pyridin-3-yl)-N-
(phenylsulfonyl)benzenesulfonamide (2n). Yellow solid (77.8
N-(phenylsulfonyl)-N-(2-(m-tolyl)imidazo[1,2-a]pyridin-3-
yl)benzenesulfonamide (2h). White solid (77.7 mg, 77%), m.p.
o
1
o
1
= 160-161 C. H NMR (400 MHz, CDCl3) δ 7.93-7.90 (m,
4H), 7.64-7.53 (m, 6H), 7.40-7.36 (m, 4H), 7.28-7.23 (m, 1H),
7.02-6.96 (m, 2H), 6.65 (td, J = 6.8, 1.0 Hz, 1H), 2.18 (s, 3H).
13C{1H} NMR (150 MHz, CDCl3) δ 145.7, 144.5, 139.1, 137.5,
134.6, 131.7, 129.3, 129.0, 128.1, 128.0, 126.8, 124.7, 123.9,
117.9, 112.6, 111.0, 21.3. HRMS (positive ESI): [M+H]+
mg, 77%), m.p. = 193-194 C. H NMR (600 MHz, CDCl3) δ
7.93 (d, J = 7.6 Hz, 4H), 7.73-7.71 (m, 2H), 7.63-7.61 (m, 3H),
7.48 (d, J = 6.8 Hz, 1H), 7.43 (t, J = 7.9 Hz, 4H), 7.29-7.27 (m,
1H), 6.80 (t, J = 8.7 Hz, 2H), 6.66 (t, J = 6.7 Hz, 1H). 13C{1H}
NMR (150 MHz, CDCl3) δ 162.9 (d, J = 246.9 Hz), 144.7,
144.5, 139.1, 134.7, 129.4 (d, J = 8.3 Hz), 129.1, 129.0, 128.1,
126.9, 123.8, 117.9, 115.1 (d, J = 21.6 Hz), 112.7, 110.9. 19F
NMR (565 MHz, CDCl3) δ -113.2. HRMS (positive ESI):
+
calcd for C26H22N3O4S2 : 504.1046, found 504.1049.
N-(2-(3-chlorophenyl)imidazo[1,2-a]pyridin-3-yl)-N-
[M+H]+ calcd for C25H19FN3O4S2 : 508.0796, found 508.0799.
N-(2-(4-chlorophenyl)imidazo[1,2-a]pyridin-3-yl)-N-
(phenylsulfonyl)benzenesulfonamide (2o). White solid (64.7
+
(phenylsulfonyl)benzenesulfonamide (2i). White solid (90.1
o
1
mg, 86%), m.p. = 157-158 C. H NMR (400 MHz, CDCl3) δ
7.91 (dd, J = 7.4, 1.0 Hz, 4H), 7.67-7.56 (m, 6H), 7.41 (t, J =
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o
1
o
1
mg, 62%), m.p. = 195-196 C. H NMR (400 MHz, CDCl3) δ
7.92 (dd, J = 8.4, 1.0 Hz, 4H), 7.67-7.60 (m, 5H), 7.48 (d, J =
6.9 Hz, 1H), 7.43-7.40 (m, 4H), 7.29-7.25 (m, 1H), 7.08-7.05
(m, 2H), 6.65 (td, J = 6.8, 1.0 Hz, 1H). 13C{1H} NMR (100
MHz, CDCl3) δ 144.5, 144.4, 139.0, 134.7, 134.4, 130.4,
129.2, 129.0, 128.8, 128.3, 127.0, 123.8, 118.0, 112.9, 111.2.
mg, 81%), m.p. = 188-189 C. H NMR (600 MHz, CDCl3) δ
7.93 (d, J = 8.1 Hz, 4H), 7.74 (d, J = 8.0 Hz, 2H), 7.60 (t, J =
7.4 Hz, 2H), 7.50 (d, J = 9.4 Hz, 1H), 7.43-7.41 (m, 5H), 7.29
(d, J = 9.4 Hz, 1H), 7.18 (t, J = 7.4 Hz, 1H), 7.12 (t, J = 7.5 Hz,
2H). 13C{1H} NMR (150 MHz, CDCl3) δ 146.1, 142.9, 139.0,
134.9, 131.5, 130.3, 129.2, 128.9, 128.7, 128.2, 127.5, 124.1,
118.6, 111.6, 107.6. HRMS (positive ESI): [M+H]+ calcd for
1
2
3
4
5
6
HRMS (positive ESI): [M+H]+ calcd for C25H19ClN3O4S2 :
+
+
524.0500, found 524.0503.
C25H19BrN3O4S2 : 567.9995, found 567.9996.
7
8
9
N-(2-(4-iodophenyl)imidazo[1,2-a]pyridin-3-yl)-N-
(phenylsulfonyl)benzenesulfonamide (2p). White solid (107.1
N-(6-iodo-2-phenylimidazo[1,2-a]pyridin-3-yl)-N-
(phenylsulfonyl)benzenesulfonamide (2v). Yellow solid (96.1
o
1
o
1
mg, 87%), m.p. = 189-190 C. H NMR (400 MHz, CDCl3) δ
7.92-7.90 (m, 4H), 7.66-7.61 (m, 3H), 7.48-7.40 (m, 9H),
7.29-7.25 (m, 1H), 6.66 (td, J = 6.8, 1.0 Hz, 1H). 13C{1H}
NMR (100 MHz, CDCl3) δ 144.6, 144.5, 139.0, 137.2, 134.7,
131.4, 129.2, 129.0, 127.1, 123.8, 118.0, 112.9, 111.3, 94.9.
mg, 78%), m.p. = 195-196 C. H NMR (400 MHz, CDCl3) δ
7.93-7.91 (m, 4H), 7.75-7.73 (m, 2H), 7.62-7.58 (m, 2H), 7.51
(t, J = 1.0 Hz, 1H), 7.43-7.39 (m, 6H), 7.19-7.15 (m, 1H),
7.13-7.09 (m, 2H). 13C{1H} NMR (100 MHz, CDCl3) δ 145.6,
143.0, 139.0, 135.0, 134.8, 131.4, 129.9, 129.3, 128.9, 128.7,
128.2, 127.5, 118.9, 111.1, 75.8. HRMS (positive ESI):
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
HRMS (positive ESI): [M+H]+ calcd for C25H19IN3O4S2 :
+
[M+H]+ calcd for C25H19IN3O4S2 : 615.9856, found 615.9857.
+
615.9856, found 615.9858.
N-(phenylsulfonyl)-N-(2-(4-
N-(2-phenyl-6-(trifluoromethyl)imidazo[1,2-a]pyridin-3-yl)-N-
(trifluoromethyl)phenyl)imidazo[1,2-a]pyridin-3-
yl)benzenesulfonamide (2q). White solid (92.5 mg, 83%), m.p.
(phenylsulfonyl)benzenesulfonamide (2w). Yellow solid (89.2
o
1
mg, 80%), m.p. = 183-184 C. H NMR (400 MHz, CDCl3) δ
7.94-7.91 (m, 4H), 7.79-7.77 (m, 2H), 7.71 (d, J = 9.4 Hz, 1H),
7.66 (s, 1H), 7.61-7.57 (m, 2H), 7.42-7.36 (m, 5H), 7.22-7.18
(m, 1H), 7.15-7.11 (m, 2H). 13C{1H} NMR (100 MHz, CDCl3)
δ 147.1, 144.2, 138.9, 135.0, 131.2, 129.3, 129.0, 128.8, 128.3,
127.6, 123.0 (q, J = 269.8 Hz), 122.7 (q, J = 16.3 Hz), 118.7,
117.1 (q, J = 34.3 Hz), 112.7. 19F NMR (376 MHz, CDCl3) δ -
62.1. HRMS (positive ESI): [M+H]+ calcd for
o
1
= 211-212 C. H NMR (400 MHz, CDCl3) δ 7.93-7.91 (m,
4H), 7.86 (d, J = 8.1 Hz, 2H), 7.65 (d, J = 9.0 Hz, 1H), 7.59-
7.55 (m, 2H), 7.51-7.49 (m, 1H), 7.41-7.35 (m, 6H), 7.31-7.27
(m,1H), 6.68 (td, J = 6.8, 1.0 Hz, 1H). 13C{1H} NMR (100
MHz, CDCl3) δ 144.6, 143.9, 138.9, 135.5, 134.9, 129.9 (q, J
= 32.1 Hz), 129.2, 129.0, 127.7, 127.5 (q, J = 232.8 Hz), 127.2,
125.0 (q, J = 3.45 Hz), 124.1 (q, J = 270.4 Hz), 123.9, 118.1,
113.1, 111.9. 19F NMR (376 MHz, CDCl3) δ -62.8. HRMS
+
C26H19F3N3O4S2 : 558.0764, found 558.0768.
+
(positive ESI): [M+H]+ calcd for C26H19F3N3O4S2 : 558.0764,
methyl
2-phenyl-3-(N-
found 558.0765.
(phenylsulfonyl)phenylsulfonamido)imidazo[1,2-a]pyridine-6-
N-(6-methyl-2-phenylimidazo[1,2-a]pyridin-3-yl)-N-
(phenylsulfonyl)benzenesulfonamide (2r). White solid (84.6
carboxylate (2x). White solid (78.8 mg, 72%), m.p. = 193-194
1
oC. H NMR (600 MHz, CDCl3) δ 8.17 (s, 1H), 7.94 (d, J =
o
1
mg, 84%), m.p. = 191-192 C. H NMR (400 MHz, CDCl3) δ
7.93-7.91 (m, 4H), 7.74-7.72 (m, 2H), 7.58-7.50 (m, 3H),
7.39-7.36 (m, 4H), 7.17-7.06 (m, 5H), 2.06 (s, 3H). 13C{1H}
NMR (150 MHz, CDCl3) δ 145.4, 143.5, 139.3, 134.5, 132.1,
129.8, 129.1, 129.0, 128.3, 128.1, 127.5, 122.4, 121.7, 117.2,
7.2 Hz, 4H), 7.83 (d, J = 9.1 Hz, 1H), 7.75 (d, J = 6.9 Hz, 2H),
7.64 (d, J = 9.1 Hz, 1H), 7.59-7.58 (m, 2H), 7.41 (t, J = 7.0 Hz,
4H), 7.19-7.18 (m, 1H), 7.14-7.13 (m, 2H), 3.85 (s, 3H).
13C{1H} NMR (150 MHz, CDCl3) δ 164.5, 147.2, 145.0, 139.0,
134.7, 131.3, 129.2, 129.0, 128.9, 128.2, 127.7, 127.6, 126.6,
117.4, 116.9, 112.2, 52.3. HRMS (positive ESI): [M+H]+
+
18.1. HRMS (positive ESI): [M+H]+ calcd for C26H22N3O4S2 :
+
504.1046, found 504.1048.
calcd for C27H22N3O6S2 : 548.0945, found 548.0947.
N-(6-fluoro-2-phenylimidazo[1,2-a]pyridin-3-yl)-N-
(phenylsulfonyl)benzenesulfonamide (2s). Yellow solid (84.3
N-(6-cyano-2-phenylimidazo[1,2-a]pyridin-3-yl)-N-
(phenylsulfonyl)benzenesulfonamide (2y). Yellow solid (17.3
o
1
o
1
mg, 83%), m.p. = 209-210 C. H NMR (400 MHz, CDCl3) δ
7.93-7.91 (m, 4H), 7.72-7.70 (m, 2H), 7.61-7.56 (m, 3H),
7.42-7.38 (m, 4H), 7.36-7.35 (m, 1H), 7.19-7.14 (m, 2H),
7.12-7.08 (m, 2H). 13C{1H} NMR (100 MHz, CDCl3) δ 154.5,
152.1, 146.7 (d, J = 2.1 Hz), 142.0, 139.0, 134.9, 131.6, 129.2,
129.0, 128.6, 128.2, 127.4, 118.8 (d, J = 25.5 Hz), 118.5 (d, J
= 8.7 Hz), 112.5, 111.0 (d, J = 38.5 Hz). 19F NMR (376 MHz,
CDCl3) δ -138.4. HRMS (positive ESI): [M+H]+ calcd for
mg, 17%), m.p. = 192-193 C. H NMR (600 MHz, CDCl3) δ
7.93 (d, J = 7.8 Hz, 4H), 7.75 (d, J = 7.7 Hz, 2H), 7.69-7.65
(m, 3H), 7.62 (s, 1H), 7.46 (t, J = 7.7 Hz, 4H), 7.34 (d, J = 9.2
Hz, 1H), 7.23 (t, J = 7.1 Hz,1H), 7.14 (t, J = 7.4 Hz, 2H).
13C{1H} NMR (150 MHz, CDCl3) δ 147.4, 143.6, 138.8, 135.2,
130.8, 129.8, 129.4, 129.3, 128.9, 128.3, 127.7, 126.5, 118.9,
115.7, 112.7, 99.0. HRMS (positive ESI): [M+H]+ calcd for
+
C26H19N4O4S2 : 515.0842, found 515.0846.
+
C25H19FN3O4S2 : 508.0796, found 508.0797.
N-(7-methoxy-2-phenylimidazo[1,2-a]pyridin-3-yl)-N-
N-(6-chloro-2-phenylimidazo[1,2-a]pyridin-3-yl)-N-
(phenylsulfonyl)benzenesulfonamide (2z). Yellow solid (20.7
o
1
(phenylsulfonyl)benzenesulfonamide (2t). White solid (88.5
mg, 20%), m.p. = 184-185 C. H NMR (600 MHz, CDCl3) δ
7.92 (d, J = 7.1 Hz, 4H), 7.68 (d, J = 6.7 Hz, 2H), 7.57-7.56
(m, 2H), 7.39 (t, J = 6.7 Hz, 4H), 7.29 (d, J = 6.7 Hz, 1H),
7.15-7.14 (m, 1H), 7.10-7.09 (m, 2H), 6.91 (s, 1H), 6.36-6.35
(m, 1H), 3.88 (s, 3H). 13C{1H} NMR (150 MHz, CDCl3) δ
159.4, 146.2, 145.3, 139.1, 134.6, 131.9, 129.1, 129.0, 128.3,
128.0, 127.3, 124.3, 109.9, 107.5, 95.2, 55.7. HRMS (positive
o
1
mg, 85%), m.p. = 195-196 C. H NMR (400 MHz, CDCl3) δ
7.93-7.91 (m, 4H), 7.74-7.72 (m, 2H), 7.61-7.55 (m, 3H),
7.42-7.38 (m, 4H), 7.34-7.34 (m, 1H), 7.21-7.15 (m, 2H),
7.13-7.09 (m, 2H). 13C{1H} NMR (100 MHz, CDCl3) δ 146.3,
142.8, 139.0, 134.9, 131.5, 129.2, 128.9, 128.7, 128.2, 127.5,
121.9, 121.9, 121.2, 118.3, 111.8. HRMS (positive ESI):
[M+H]+ calcd for C25H19ClN3O4S2 : 524.0500, found 524.0502.
ESI): [M+H]+ calcd for C26H22N3O5S2 : 520.0995, found
+
+
N-(6-bromo-2-phenylimidazo[1,2-a]pyridin-3-yl)-N-
(phenylsulfonyl)benzenesulfonamide (2u). White solid (91.6
520.0996.
N-(7-methyl-2-phenylimidazo[1,2-a]pyridin-3-yl)-N-
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+
(phenylsulfonyl)benzenesulfonamide (2aa). White solid (85.2
[M+H]+ calcd for C26H22N3O4S2 : 504.1046, found 504.1049.
N-(2-phenyl-8-(trifluoromethyl)imidazo[1,2-a]pyridin-3-yl)-N-
(phenylsulfonyl)benzenesulfonamide (2ag). Yellow solid
(24.7mg, 22%), m.p. = 171-172 oC. 1H NMR (600 MHz,
CDCl3) δ 7.92 (d, J = 7.4 Hz, 4H), 7.75 (d, J = 7.2 Hz, 2H),
7.63-7.60 (m, 4H), 7.41 (t, J = 7.3 Hz, 4H), 7.17 (t, J = 6.8 Hz,
1H), 7.10 (t, J = 7.3 Hz, 2H), 6.70 (t, J = 6.4 Hz, 1H). 13C{1H}
NMR (150 MHz, CDCl3) δ 146.3, 140.1, 138.9, 134.8, 131.2,
129.2, 129.0, 128.8, 128.1, 127.8, 127.1, 125.1 (q, J = 5.2 Hz),
122.5 (q, J = 270.8 Hz), 119.6 (q, J = 33.6 Hz), 112.2, 110.8.
19F NMR (565 MHz, CDCl3) δ -63.0. HRMS (positive ESI):
o
1
1
2
3
4
5
6
7
8
mg, 85%), m.p. = 173-174 C. H NMR (400 MHz, CDCl3) δ
7.91-7.89 (m, 4H), 7.70-7.68 (m, 2H), 7.56-7.52 (m, 2H),
7.39-7.35 (m, 6H), 7.16-7.06 (m, 3H), 6.48 (dd, J = 7.2, 1.2
Hz, 1H), 2.38 (s, 3H). 13C{1H} NMR (150 MHz, CDCl3) δ
145.5, 145.0, 139.1, 138.0, 134.6, 132.0, 129.0, 129.0, 128.3,
128.0, 127.4, 123.1, 116.4, 115.3, 110.4, 21.3. HRMS (posi-
tive ESI): [M+H]+ calcd for C26H22N3O4S2 : 504.1046, found
+
504.1049.
N-(7-chloro-2-phenylimidazo[1,2-a]pyridin-3-yl)-N-
(phenylsulfonyl)benzenesulfonamide (2ab). White solid
(78.3mg, 75%), m.p. = 206-207 oC. 1H NMR (600 MHz,
CDCl3) δ 7.90 (d, J = 7.7 Hz, 4H), 7.69 (d, J = 7.7 Hz, 2H),
7.62 (s, 1H), 7.57 (t, J = 7.3 Hz, 2H), 7.40-7.38 (m, 5H), 7.17
(t, J = 6.8 Hz, 1H), 7.10 (t, J = 7.5 Hz, 2H). 6.63 (d, J = 7.1 Hz,
1H). 13C{1H} NMR (150 MHz, CDCl3) δ 146.3, 144.3, 138.9,
134.8, 133.4, 131.4, 129.2, 129.0, 128.7, 128.2, 127.5, 124.2,
116.8, 114.3, 111.4. HRMS (positive ESI): [M+H]+ calcd for
9
[M+H]+ calcd for C26H19FN3O4S2 : 558.0764, found 558.0769.
+
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
methyl
2-phenyl-3-(N-
(phenylsulfonyl)phenylsulfonamido)imidazo[1,2-a]pyridine-8-
carboxylate (2ah). White solid (39 mg, 36%), m.p. = 81-82 oC.
1H NMR (600 MHz, CDCl3) δ 8.02 (d, J = 7.1 Hz, 1H), 7.90
(d, J = 7.8 Hz, 4H), 7.77 (d, J = 7.7 Hz, 2H), 7.68 (d, J = 6.7
Hz, 1H), 7.59 (t, J = 7.4 Hz, 2H), 7.40 (t, J = 7.4 Hz, 4H), 7.17
(t, J = 7.4 Hz, 1H), 7.09 (t, J = 7.3 Hz, 2H), 6.72 (t, J = 6.8 Hz,
1H), 4.07 (s, 3H). 13C{1H} NMR (150 MHz, CDCl3) δ 164.7,
146.3, 142.0, 139.0, 134.8, 131.5, 131.2, 129.2, 129.0, 128.7,
128.0, 127.8, 127.6, 120.1, 111.9, 111.5, 52.8. HRMS (posi-
+
C25H19ClN3O4S2 : 524.0500, found 524.0504.
N-(7-bromo-2-phenylimidazo[1,2-a]pyridin-3-yl)-N-
(phenylsulfonyl)benzenesulfonamide (2ac). White solid
(68.2mg, 60%), m.p. = 204-205 oC. 1H NMR (400 MHz,
CDCl3) δ 7.91-7.89 (m, 4H), 7.82 (d, J = 1.2 Hz, 1H), 7.70-
7.68 (m, 2H), 7.59-7.55 (m, 2H), 7.41-7.37 (m, 4H), 7.34 (dd,
J = 7.2, 0.5 Hz, 1H), 7.19-7.15 (m, 1H), 7.12-7.08 (m, 2H).
6.75 (dd, J = 7.2, 1.9 Hz, 1H). 13C{1H} NMR (100 MHz,
CDCl3) δ 146.1, 144.5, 138.9, 134.8, 131.3, 129.8, 129.2,
129.0, 128.8, 128.2, 127.5, 124.2, 121.0, 120.2, 116.6, 111.5.
tive ESI): [M+H]+ calcd for C27H22N3O6S2 : 548.0945, found
+
548.0949.
N-(6-fluoro-2-(p-tolyl)imidazo[1,2-a]pyridin-3-yl)-N-
(phenylsulfonyl)benzenesulfonamide (2ai). Yellow solid (77.1
o
1
mg, 74%), m.p. = 187-188 C. H NMR (600 MHz, CDCl3) δ
7.92 (d, J = 7.4 Hz, 4H), 7.59 (d, J = 6.4 Hz, 5H), 7.40 (t, J =
7.0 Hz, 4H), 7.33 (s, 1H), 7.14 (t, J = 8.3 Hz, 1H), 6.90 (d, J =
7.1 Hz, 2H), 2.27 (s, 3H). 13C{1H} NMR (150 MHz, CDCl3) δ
154.0, 152.4, 146.8, 142.0, 139.1, 138.5, 134.7, 129.2, 129.0,
128.9, 128.8, 127.3, 118.6 (d, J = 25.1 Hz), 118.4 (d, J = 8.6
Hz), 112.3, 111.0 (d, J = 41.9 Hz), 21.2. 19F NMR (565 MHz,
CDCl3) δ -138.6. HRMS (positive ESI): [M+H]+ calcd for
+
HRMS (positive ESI): [M+H]+ calcd for C25H19BrN3O4S2 :
567.9995, found 567.9998.
N-(2-phenyl-7-(trifluoromethyl)imidazo[1,2-a]pyridin-3-yl)-N-
(phenylsulfonyl)benzenesulfonamide (2ad). Yellow solid
o
1
(103.5 mg, 93%), m.p. = 212-213 C. H NMR (600 MHz,
CDCl3) δ 7.95 (s, 1H), 7.91 (d, J = 7.9 Hz, 4H), 7.72 (d, J =
7.7 Hz, 2H), 7.59 (t, J = 7.5 Hz, 3H), 7.40 (t, J = 7.4 Hz, 4H),
7.19 (t, J = 7.1 Hz, 1H), 7.12 (t, J = 7.2 Hz, 2H), 6.82 (d, J =
7.1 Hz, 1H). 13C{1H} NMR (150 MHz, CDCl3) δ 147.3, 142.7,
138.9, 134.9, 131.2, 129.2, 129.0, 128.9, 128.6 (q, J = 34.3
Hz), 128.2, 127.6, 124.8, 122.9 (q, J = 271.0 Hz), 116.0 (q, J =
4.7 Hz), 112.6, 108.4 (q, J = 2.5 Hz). 19F NMR (565 MHz,
CDCl3) δ -63.8. HRMS (positive ESI): [M+H]+ calcd for
+
C26H21FN3O4S2 : 522.0952, found 522.0953.
N-(6-iodo-2-(p-tolyl)imidazo[1,2-a]pyridin-3-yl)-N-
(phenylsulfonyl)benzenesulfonamide (2aj). Yellow solid (44.9
o
1
mg, 36%), m.p. = 209-210 C. H NMR (600 MHz, CDCl3) δ
7.93 (d, J = 7.6 Hz, 4H), 7.64-7.61 (m, 4H), 7.49 (s, 1H), 7.44
(t, J = 7.5 Hz, 4H), 7.39 (s, 2H), 6.91 (d, J = 7.5 Hz, 2H), 2.29
(s, 3H). 13C{1H} NMR (150 MHz, CDCl3) δ 145.8, 143.0,
139.2, 138.6, 134.7, 134.7, 129.2, 129.0, 128.9, 128.8, 128.5,
127.4, 118.8, 110.8, 75.5, 21.2. HRMS (positive ESI): [M+H]+
+
C26H19F3N3O4S2 : 558.0764, found 558.0767.
Methyl
2-phenyl-3-(N-
+
(phenylsulfonyl)phenylsulfonamido)imidazo[1,2-a]pyridine-7-
calcd for C26H21IN3O4S2 : 630.0013, found 630.0016.
carboxylate (2ae). Yellow solid (36.7mg, 34%), m.p. = 205-
N-(phenylsulfonyl)-N-(2-(p-tolyl)-6-
(trifluoromethyl)imidazo[1,2-a]pyridin-3-
o
1
206 C. H NMR (400 MHz, CDCl3) δ 8.35-8.34 (m, 1H),
7.93-7.91 (m, 4H), 7.76-7.74 (m, 2H), 7.62-7.58 (m, 2H), 7.48
(dd, J = 7.2, 0.8 Hz, 1H), 7.43-7.39 (m, 4H), 7.24-7.18 (m,
2H), 7.15-7.11 (m, 2H), 3.98 (s, 3H). 13C{1H} NMR (150
MHz, CDCl3) δ 165.2, 147.4, 143.4, 139.0, 134.8, 131.4,
129.2, 129.0, 128.8, 128.2, 127.6, 123.6, 120.4, 112.7, 111.9,
yl)benzenesulfonamide (2ak). White solid (77.2 mg, 68%),
m.p. = 212-213 oC. 1H NMR (600 MHz, CDCl3) δ 7.92 (d, J =
7.6 Hz, 4H), 7.70 (d, J = 9.2 Hz, 1H), 7.66-7.59 (m, 5H), 7.41
(t, J = 7.3 Hz, 4H), 7.36 (d, J = 9.2 Hz, 1H), 6.93 (d, J = 7.4
Hz, 2H), 2.29 (s, 3H). 13C{1H} NMR (150 MHz, CDCl3) δ
147.3, 144.2, 139.0, 139.0, 134.8, 129.3, 129.0, 128.9, 128.3,
127.5, 123.1 (q, J = 269.7 Hz), 122.7 (q, J = 5.6 Hz), 122.5,
118.6, 117.0 (q, J = 34.4 Hz), 112.4, 21.2. 19F NMR (565 MHz,
CDCl3) δ -62.1. HRMS (positive ESI): [M+H]+ calcd for
52.8. HRMS (positive ESI): [M+H]+ calcd for C27H22N3O6S2 :
+
548.0945, found 548.0948.
N-(8-methyl-2-phenylimidazo[1,2-a]pyridin-3-yl)-N-
(phenylsulfonyl)benzenesulfonamide (2af). Yellow solid
(39.1mg, 39%), m.p. = 170-171 oC. 1H NMR (400 MHz,
CDCl3) δ 7.93-7.90 (m, 4H), 7.75-7.73 (m, 2H), 7.59-7.55 (m,
2H), 7.41-7.36 (m, 5H), 7.18-7.04 (m, 4H), 6.55 (t, J = 6.8 Hz,
1H), 2.66 (s, 3H). 13C{1H} NMR (150 MHz, CDCl3) δ 145.2,
144.8, 139.2, 134.5, 132.2, 129.0, 129.0, 128.2, 128.1, 128.0,
127.7, 125.4, 121.7, 112.6, 111.3, 16.5. HRMS (positive ESI):
+
C27H21F3N3O4S2 : 572.0920, found 572.0923.
N-(2-(2-bromophenyl)-6-methylimidazo[1,2-a]pyridin-3-yl)-
N-(phenylsulfonyl)benzenesulfonamide (2al). Yellow solid (76
o
1
mg, 65%), m.p. = 197-198 C. H NMR (600 MHz, CDCl3) δ
7.94 (d, J = 7.9 Hz, 4H), 7.76 (d, J = 7.6 Hz, 1H), 7.59-7.56
(m, 3H), 7.47 (d, J = 8.0 Hz, 1H), 7.41 (t, J = 7.6 Hz, 4H),
7
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7.22 (s, 1H), 7.18 (t, J = 7.4 Hz, 1H), 7.12-7.08 (m, 2H), 2.12
6.55 (t, J = 6.7 Hz, 1H), 6.03 (d, J = 2.9 Hz, 1H). 13C{1H}
(s, 3H). 13C{1H} NMR (150 MHz, CDCl3) δ 145.8, 143.1,
139.1, 134.3, 133.3, 133.0, 131.5, 129.9, 129.7, 129.0, 128.9,
126.7, 124.4, 122.7, 121.7, 117.7, 111.9, 18.1. HRMS (posi-
NMR (150 MHz, CDCl3) δ 148.0, 144.7, 139.3, 138.8, 138.8,
136.7, 134.8, 134.2, 129.3, 129.1, 128.9, 128.9, 127.1, 123.6,
118.0, 114.3, 113.2, 111.9, 110.4. HRMS (positive ESI):
1
2
3
4
5
6
7
8
tive ESI): [M+H]+ calcd for C26H21BrN3O4S2 : 582.0151,
[M+H]+ calcd for C35H27N4O9S4 : 775.0655, found 775.0663.
+
+
found 582.0154.
N-(phenylsulfonyl)-N-(2-(thiophen-2-yl)imidazo[1,2-
N-(2-(naphthalen-2-yl)imidazo[1,2-a]pyridin-3-yl)-N-
(phenylsulfonyl)benzenesulfonamide (4a). Yellow solid (38.4
a]pyridin-3-yl)benzenesulfonamide (4f). Green solid (12.7 mg,
1
13%), m.p. = 160-161 oC. H NMR (600 MHz, CDCl3) δ 7.97
o
1
mg, 36%), m.p. = 188-189 C. H NMR (600 MHz, CDCl3) δ
8.22 (s, 1H), 7.93-7.87 (m, 5H), 7.74-7.68 (m, 2H), 7.62-7.58
(m, 3H), 7.46-7.37 (m, 4H), 7.31-7.26 (m, 5H), 6.69 (t, J = 5.5
Hz, 1H). 13C{1H} NMR (150 MHz, CDCl3) δ 145.5, 144.7,
139.1, 134.4, 133.3, 133.0, 129.2, 129.0, 129.0, 128.8, 127.7,
127.3, 127.0, 126.9, 126.4, 125.8, 125.1, 123.9, 118.0, 112.8,
(d, J = 7.9 Hz, 4H), 7.62-7.61 (m, 3H), 7.45 (t, J = 7.2 Hz, 5H),
7.27-7.25 (m, 1H), 7.17 (d, J = 4.8 Hz, 1H), 7.06 (d, J = 2.5
Hz, 1H), 6.69-6.68 (m, 1H), 6.65 (t, J = 6.7 Hz, 1H). 13C{1H}
NMR (150 MHz, CDCl3) δ 144.6, 141.3, 139.5, 134.7, 134.7,
129.1, 128.9, 127.7, 127.0, 126.6, 125.9, 123.6, 117.7, 112.8,
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
109.8. HRMS (positive ESI): [M+H]+ calcd for C23H18N3O4S3 :
+
111.4. HRMS (positive ESI): [M+H]+ calcd for C29H22N3O4S2 :
496.0454, found 496.0455.
N-(phenylsulfonyl)-N-(5-(3-(N-
+
540.1046, found 540.1049.
N-(2-phenylbenzo[d]imidazo[2,1-b]thiazol-3-yl)-N-
(phenylsulfonyl)benzenesulfonamide (4b). Yellow solid (29.6
(phenylsulfonyl)phenylsulfonamido)imidazo[1,2-a]pyridin-2-
yl)thiophen-2-yl)benzenesulfonamide (4f’). Yellow solid (8.5
mg, 5%), m.p. = 91-92 oC. 1H NMR (600 MHz, CDCl3) δ 8.00
(d, J = 7.7 Hz, 4H), 7.97 (d, J = 7.7 Hz, 4H), 7.72-7.66 (m,
4H), 7.60-7.57 (m, 5H), 7.49 (t, J = 7.6 Hz, 4H), 7.45 (d, J =
6.7 Hz, 1H), 7.30-7.27 (m, 1H), 6.82 (d, J = 3.8 Hz, 1H), 6.67
(t, J = 6.6 Hz, 1H), 6.30 (d, J = 3.8 Hz, 1H). 13C{1H} NMR
(150 MHz, CDCl3) δ 144.5, 140.1, 139.0, 139.0, 137.9, 135.2,
134.2, 132.2, 129.4, 129.1, 128.9, 128.7, 127.3, 123.8, 123.7,
117.9, 113.2, 110.3. HRMS (positive ESI): [M+H]+ calcd for
o
1
mg, 27%), m.p. = 220-221 C. H NMR (600 MHz, CDCl3) δ
7.96 (d, J = 7.9 Hz, 4H), 7.66 (d, J = 7.7 Hz, 2H), 7.63 (d, J =
8.0 Hz, 1H), 7.54 (t, J = 7.4 Hz, 2H), 7.35 (t, J = 7.6 Hz, 4H),
7.21 (t, J = 6.8 Hz, 1H), 7.11 (t, J = 7.0 Hz, 1H), 7.05 (t, J =
7.4 Hz, 2H), 6.93-6.89 (m, 2H). 13C{1H} NMR (150 MHz,
CDCl3) δ 149.0, 138.8, 134.6, 129.8, 129.5, 128.9, 128.0,
126.9, 125.6, 124.8, 123.7, 114.4. HRMS (positive ESI):
[M+H]+ calcd for C27H20N3O4S3 : 546.0610, found 546.0613.
+
+
N-(2-phenylimidazo[1,2-b]pyridazin-3-yl)-N-
C35H27N4O8S5 : 791.0427, found 791.0448.
(phenylsulfonyl)benzenesulfonamide (4c). Yellow solid (51.2
N-(2-phenylimidazo[1,2-a]pyridin-3-yl)benzenesulfonamide
o
1
o
1
mg, 52%), m.p. = 211-212 C. H NMR (600 MHz, CDCl3) δ
8.09 (s, 1H), 7.95 (d, J = 7.4 Hz, 5H), 7.87 (d, J = 7.0 Hz, 2H),
7.53 (t, J = 6.7 Hz, 2H), 7.36 (t, J = 7.1 Hz, 4H), 7.21-7.16 (m,
3H), 7.10-7.08 (m, 1H). 13C{1H} NMR (150 MHz, CDCl3) δ
145.6, 142.7, 139.4, 138.4, 134.3, 131.6, 129.3, 128.9, 128.6,
128.3, 127.6, 125.7, 119.2, 115.2. HRMS (positive ESI):
(5a). White solid (16.7 mg, 48%), m.p. = 218-219 C. H
NMR (600 MHz, DMSO) δ 10.68 (s, 1H), 8.13 (d, J = 6.4 Hz,
1H), 7.70 (d, J = 4.4 Hz, 2H), 7.58 (d, J = 8.9 Hz, 1H), 7.53 (d,
J = 7.6 Hz, 2H), 7.44 (t, J = 7.2 Hz, 1H), 7.35-7.29 (m, 3H),
7.16 (s, 3H), 6.95 (t, J = 6.5 Hz, 1H). 13C{1H} NMR (150
MHz, DMSO) δ 142.8, 140.6, 140.2, 133.5, 133.0, 129.5,
128.3, 128.0, 127.2, 127.0, 126.5, 124.1, 117.3, 113.7, 112.9,
HRMS (positive ESI): [M+H]+ calcd for C19H16N3O2S+:
350.0958, found 350.0957.
+
[M+H]+ calcd for C24H19N4O4S2 : 491.0842, found 491.0845.
N-(6-phenylimidazo[2,1-b]thiazol-5-yl)-N-
(phenylsulfonyl)benzenesulfonamide (4d). Yellow solid (58.9
o
1
mg, 59%), m.p. = 175-176 C. H NMR (600 MHz, CDCl3) δ
7.92 (d, J = 7.0 Hz, 4H), 7.59-7.56 (m, 4H), 7.41 (t, J = 6.8 Hz,
4H), 7.14-7.13 (m, 1H), 7.10-7.08 (m, 2H), 6.69 (d, J = 16.6
Hz, 2H). 13C{1H} NMR (150 MHz, CDCl3) δ 150.1, 147.1,
138.9, 134.6, 131.9, 129.1, 128.9, 128.1, 128.1, 126.7, 118.1,
113.0, 112.2. HRMS (positive ESI): [M+H]+ calcd for
N-(2-(4-(trifluoromethyl)phenyl)imidazo[1,2-a]pyridin-3-
yl)benzenesulfonamide (5b). Yellow solid (33.4mg, 80%), m.p.
o
1
= 260-261 C. H NMR (600 MHz, DMSO) δ 10.83 (s, 1H),
8.23 (d, J = 6.4 Hz, 1H), 7.86 (d, J = 7.6 Hz, 2H), 7.62 (d, J =
8.9 Hz, 1H), 7.49 (t, J = 5.7 Hz, 4H), 7.40-7.35 (m, 2H), 7.25
(t, J = 7.1 Hz, 2H), 7.01 (t, J = 6.2 Hz, 1H). 13C{1H} NMR
(150 MHz, DMSO) δ 143.1, 140.3, 138.7, 137.1, 133.4, 129.4,
128.1 (q, J = 31.6 Hz), 127.7, 127.0, 127.0, 125.2 (q, J = 3.5
Hz), 124.7 (q, J = 270.1 Hz), 124.4, 117.5, 114.7, 113.3. 19F
NMR (565 MHz, DMSO) δ -61.2. HRMS (positive ESI):
[M+H]+ calcd for C20H15F3N3O2S+: 418.0832, found 418.0835.
N-(2-(m-tolyl)imidazo[1,2-a]pyridin-3-yl)benzenesulfonamide
+
C23H18N3O4S3 : 496.0454, found 496.0453.
N-(2-(furan-2-yl)imidazo[1,2-a]pyridin-3-yl)-N-
(phenylsulfonyl)benzenesulfonamide (4e). Red solid (15.6 mg,
16%), m.p. = 64-65 oC. 1H NMR (600 MHz, CDCl3) δ 7.95 (d,
J = 7.6 Hz, 4H), 7.67-7.62 (m, 4H), 7.47 (t, J = 7.9 Hz, 4H),
7.30 (t, J = 7.4 Hz, 1H), 6.93 (s, 1H), 6.74 (t, J = 6.7 Hz, 1H),
6.70 (d, J = 3.2 Hz, 1H), 6.21-6.20 (m, 1H). 13C{1H} NMR
(150 MHz, CDCl3) δ 146.9, 144.9, 142.9, 139.4, 137.6, 134.5,
129.0, 128.9, 127.2, 123.8, 117.8, 113.0, 111.1, 109.8, 109.7.
o
1
(5c). Yellow solid (31.9 mg, 88%), m.p. = 208-209 C. H
NMR (600 MHz, CDCl3) δ 8.29 (d, J = 6.4 Hz, 1H), 7.58 (d, J
= 8.8 Hz, 1H), 7.45 (d, J = 7.3 Hz, 2H), 7.28-7.24 (m, 2H),
7.08-7.06 (m, 4H), 6.86-6.83 (m, 3H), 2.08 (s, 3H). 13C{1H}
NMR (150 MHz, CDCl3) δ 143.4, 141.4, 138.7, 137.5, 132.9,
131.9, 128.6, 128.5, 127.9, 127.8, 127.1, 126.2, 124.3, 124.0,
117.1, 112.6, 112.6, 21.2. HRMS (positive ESI): [M+H]+
calcd for C20H18N3O2S+: 364.1114, found 364.1115.
+
HRMS (positive ESI): [M+H]+ calcd for C23H18N3O5S2 :
480.0682, found 480.0684.
N-(phenylsulfonyl)-N-(2-(4-(N-
(phenylsulfonyl)phenylsulfonamido)furan-2-yl)imidazo[1,2-
a]pyridin-3-yl)benzenesulfonamide (4e’). Yellow solid (9.7
o
1
mg, 6%), m.p. = 176-177 C. H NMR (600 MHz, CDCl3) δ
8.07 (d, J = 7.8 Hz, 4H), 7.99 (d, J = 7.8 Hz, 4H), 7.64 (t, J =
7.3 Hz, 2H), 7.60 (d, J = 8.9 Hz, 1H), 7.54-7.52 (m, 6H), 7.48-
7.44 (m, 5H), 7.23 (t, J = 7.6 Hz, 1H), 6.84 (d, J = 2.8 Hz, 1H),
N-(7-methyl-2-phenylimidazo[1,2-a]pyridin-3-
yl)benzenesulfonamide (5d). White solid (25.8 mg, 71%), m.p.
o
1
= 221-222 C. H NMR (600 MHz, DMSO) δ 10.60 (s, 1H),
8.01 (d, J = 5.1 Hz, 1H), 7.67-7.67 (m, 2H), 7.52 (d, J = 7.4
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The Journal of Organic Chemistry
velopments Using Nitrogen–Heteroatom Bonds as Amination
Hz, 2H), 7.43 (t, J = 6.8 Hz, 1H), 7.34-7.29 (m, 3H), 7.15 (s,
3H), 6.80 (d, J = 5.9 Hz, 1H), 2.37 (s, 3H). 13C{1H} NMR
(150 MHz, DMSO) δ 143.1, 140.7, 137.2, 133.4, 133.1, 129.4,
129.2, 128.3, 127.8, 127.1, 126.9, 123.5, 115.5, 115.3, 113.3,
21.2. HRMS (positive ESI): [M+H]+ calcd for C20H18N3O2S+:
364.1114, found 364.1117.
Reagents in the Synthesis of Aminoarenes. J. Org. Chem.
2017, 82, 839-847. (c) Bhunia, S.; Pawar, G. G.; Kumar, S. V.;
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2017, 56, 16136-16179.
1
2
3
4
5
3-fluoro-2-phenylimidazo[1,2-a]pyridine (6). Yellow solid
(15.2 mg, 36%), m.p. = 94-95 oC. 1H NMR (600 MHz, CDCl3)
δ 8.02 (d, J = 7.6 Hz, 2H), 7.92 (d, J = 6.7 Hz, 1H), 7.54 (d, J
= 9.1 Hz, 1H), 7.47 (t, J = 7.4 Hz, 2H), 7.34 (t, J = 7.3 Hz, 1H),
7.15 (t, J = 7.2 Hz, 1H), 6.85 (t, J = 6.6 Hz, 1H). 13C{1H}
NMR (150 MHz, CDCl3) δ 138.7 (d, J = 273.2 Hz), 136.9 (d, J
= 5.6 Hz), 131.7 (d, J = 5.2 Hz), 128.8, 127.8, 126.3 (d, J =
4.0 Hz), 123.8, 122.7, 120.4, 117.9, 112.6. 19F NMR (565
MHz, CDCl3) δ -154.9. HRMS (positive ESI): [M+H]+ calcd
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2360. (f) Zhu, D.; Yang, G.; He, J.; Chu, L.; Chen, G.; Gong,
W.; Chen, K.; Eastgate, M. D.; Yu, J.-Q. Ligand-Promoted
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
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31
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41
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43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
+
for C13H10FN2 : 213.0823, found 213.0824.
ASSOCIATED CONTENT
Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website.
X-ray data for 2a (CIF)
Optimization of reaction conditions, crystallography of product 2a,
and NMR spectra (PDF)
AUTHOR INFORMATION
Corresponding Author
*E-mail: zhuxinju@zzu.edu.cn; mpsong@zzu.edu.cn.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENT
Financial support from the National Natural Science Foundation
of China (Grant No. 21672192), the China Postdoctoral Science
Foundation (Grant Nos. 2016M602254 and 2016M600582), the
Program for Science & Technology Innovation Talents in Univer-
sities of Henan Province (Grant No. 17HASTIT004), and the Aid
Project for the Leading Young Teachers in Henan Provincial In-
stitutions (Grant No. 2015GGJS-157) is gratefully appreciated.
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