Electrochemical HI-mediated Intermolecular C-N Bond Formation to Synthesize Imidazoles from Aryl Ketones and Benzylamines

Article abstract of DOI:10.1021/acs.joc.0c00316

An efficient and novel electrochemical oxidative tandem cyclization of aryl ketones and benzylamines for the synthesis of 1,2,4-trisubstituted-(1H)-imidazoles has been developed under metal- and oxidant-free conditions. This direct C-N bond formation strategy, with a broad functional group tolerance, affords the desired imidazoles in moderate to excellent yields.

Full text of DOI:10.1021/acs.joc.0c00316

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Article
Electrochemical HI-Mediated Intermolecular C-N Bond Formation
to Synthesize Imidazoles from Aryl Ketones and Benzylamines
Zan Yang, Jiaqi Zhang, Liping Hu, An Li, Lijun Li, Kun Liu, Tao Yang, and Congshan Zhou
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.0c00316 • Publication Date (Web): 13 Apr 2020
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Electrochemical HI-Mediated Intermolecular C-N Bond
Formation to Synthesize Imidazoles from Aryl Ketones and
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16
Benzylamines
Zan Yang, Jiaqi Zhang, Liping Hu, An Li, Lijun Li, Kun Liu*, Tao Yang*, Congshan Zhou*
College of Chemistry and Chemical Engineering, Hunan Institute of Science and Technology, Yueyang
414006, China
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liukun328@126.com, yangtaozcs@126.com and zhoucongsh@126.com
Ar
O
H
undivided cell
N
+
Ar
Ar
Ar
NH2
External oxidant-free
Transition metal-free
Mild conditions
N
H
Ar
32 examples
up to 95% yield
Gram-scale synthesis
ABSTRACT
An efficient and novel electrochemical oxidative tandem cyclization of aryl ketones and benzylamines for
the synthesis of 1,2,4-trisubstituted-(1H)-imidazoles has been developed under metal- and oxidant-free
conditions. This direct C-N bond formation strategy, with a broad functional group tolerance, afford the
desired imidazoles in moderate to excellent yields.
and organic chemistry.5 Accordingly, various of method
INTRODUCTION
have been developed for the synthesis of 1,2,4-
Recently, the C-N bond formation has drawn attention
for the construction of nitrogen-containing molecules via
direct C-H amination.1 Compared with the Ullmann,
Buchwald and Hartwig reaction,2 the direct C-H amination,
especially the C-H/N-H coupling reaction, provided a
green and atom-economical approach for the synthesis of
various functional nitrogen-containing skeleton.3
trisubstituted-(1H)-imidazoles.
Ji
reported
a
CuI/BF3•Et2O-co-catalyzed tandem C-N cyclization
reaction of ketones with benzylamines for the construction
of 1,2,4-trisubstituted-(1H)-imidazoles under neat
conditions and in the presence of O2 (scheme 1a).6 Jiang
described a metal-free method for the synthesis of
imidazoles from ketones and benzylamines using I2 and 12
M HCl (scheme 1b).7 The Cu(OTf)2/I2-catalyzed C=C
bond cleavage for the synthesis of imidazoles from
chalcones and benzylamines have also been developed
(scheme 1c).8 Moreover, the imidazoles have been
synthesized form benzylamines with vinyl azides or
Imidazoles are an important class of nitrogen
heterocycles
owing
to
their
biological
and
pharmacological activities, such as antitumor,
antiplasmodium, antifungal and PPARδ modulator.4 In
addition, the imidazoles has also been used in materials
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enamides have also been prepared by Yan and Huang,
Initially, the reaction of acetophenone (1a) with
respectively (scheme 1d and 1e).9 However, these
strategies suffer from stoichiometric chemical oxidants,
heavy metal residues and functionalized starting materials.
Thus, the development of green and efficient multiple-
component strategy for the synthesis of imidazoles under
metal-free and oxidant-free conditions is highly desirable.
benzylamine (2a) as model substrates in an undivided cell
under 10 mA constant current using HI as the catalyst, n-
BuNBF4 as the electrolyte, C(+)/Pt(-) as the electrodes in
o
DMSO at 70 C for 6 h was studied, the desired product
3aa was obtained in 83% yield (table 1, entry 1). When
PTSA (p-toluenesulfonic acid) instead of HI as the catalyst,
no target product was found (table 1, entry 2). Further, a
series of iodine slats were screened, such as, KI, TBAI (
tetrabutylammonium iodide) and TBAI/HOAc, no
significant increase of product 3aa was observed (table 1,
entries 3-5). The effect of electrolytes was also
investigated, and n-BuNBF4 showed better result for this
transformation (table 1, entries 6-7). Either increasing or
decreasing the electric current resulted in a lower yield of
3aa (table 1, entries 8-9). No desired imidazole was
detected when the reaction was carried without HI (table
1, entry 10). The lower yield was afforded by increasing or
decreasing the amount of HI (table 1, entries 11-12). When
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Previous work: chemical oxidant
Ar
O
N
+
H2N
Ar
R
N
Ar
Ar
Ar
(a) Ji and Wang et al: R = H, CuI, BF3 Et2O, O2
(b) Jiang et al: R = H, I2, 12 M HCl, O2
(c) Somappa et al: R = CHPh, Cu(OTf)2, I2
Ar
N
R
N
+
H2N
Ar
Ar
Ar
Ar
Ar
(d) Yan et al: R = N3, I2, TBHP
(e) Huang et al: R = NHAc, CuBr, I2
This work: anodic oxidant
Ar
N
O
H
N
undivided cell
+
Ar
H2N
Ar
o
Ar
the reaction carried at 60 C, the product of 3aa was
H
External oxidant-free
obtained in 56% yield (table 1, entry 13). No significant
improvement of the yield of 3aa with higher temperature
(table 1, entry 14). Furthermore, EtOH and MeCN as
solvent were examined, and DMSO gave the best result
(table 1, entries 15-16). Used Pt or Ni plate instead of
carbon rod as an anode, the yield of corresponding product
was decreased (table 1, entries 17-18). Notably, no desired
Transition metal-free
Gram-scale synthesis
Scheme 1. Method for the synthesis of 1,2,4-trisubstituted
imidazoles
Electrosynthesis has enabled as a useful synthetic tool
for the assembly of valuable chemical transformations via
anodic oxidant process.10 Recently, various anodic
oxidation cyclization reaction has been developed for the
synthesis of nitrogen containing heterocycles via C-N
bond formation.11 On the other hand, the electrochemical
promoted formation C-N bond for the synthesis of
heterocyclic compounds such as imidazoles, are extremely
limited. Yu developed an electrochemically mediated
synthesis of imidazo[1,2-a]pyridines from acetophenones,
unsatruated and alkyl ketones with 2-aminopyridines
through the intermolecular C-N bond formation.12 Wang
reported an electrochemical tandem cyclization for the
construction of imidazo[1,5-a]quinolines in the presence
of iodine.13 Inspired by these studies and our previous
works14, herein, we disclosed the electrochemical
oxidative transformation of aryl ketones with
benzylamines into 1,2,4-trisubstituted-(1H)-imidazoles
under transition metal and oxidant free conditions.
product was afforded in the absence of electric current，
and the oxazole obtained in 7% yield. (table 1, entry 19).
Additionally, a 5 mmol scale reaction of 1a with 2a was
carried out, affording the desired product in 71% yield
(table 1, entry 20).
Table 1. Screening of Optimal Conditionsa
O
H
undivided cell
N
+
H2N
N
(+)C/(-)Pt
I = 10 mA
HI, DMSO, 70 o
H
C
1a
2a
3aa
Entry
Variation from the standard
conditions
Yield
[%]
1
2
none
83
PTSA instead of HI
N. R.
RESULTS AND DISCUSSION
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KI instead of HI
TBAI instead of HI
TBAI, HOAc (20 mol%)
instead of HI
47
13
55
yied. In addition, heterocyclic,1-naphthyl and 2-naphthyl
derived ketone gave the corresponding product 3ta-3va in
89%, 65% and 90% yield, respectively. However, when
aliphatic ketone was employed, no desired product 3wa
was obtained, likely due to the low activity of aliphatic
ketone under the present conditions.
6
7
8
KI instead of n-BuNBF4
LiClO4 instead of n-BuNBF4
I = 15 mA instead of I = 10 mA,
4 h
75
51
63
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Scheme 2. Substrate scope of aryl ketonesa
9
I = 5 mA instead of I = 10 mA,
10 h
60
O
H
undivided cell
+
Ar
H2N
10
11
12
13
14
15
16
17
no HI
N. R.
72
N
N
(+)C/(-)Pt
I = 10 mA
HI, DMSO, 70 oC
H
HI (50 mol%)
Ar
HI (10 mol%)
45
3
1
2a
At 60 oC
At 80 oC
56
3ia
3ja
3ka
R = 4-Cl,
R = 3-Cl,
R = 2-Cl,
R = 4-Br,
, 89%
, 92%
, 93%
, 84%
, 75%
3na
, 90%
, 86%
3aa
R = H,
, 83%
74
3ba
3ca
3da
R = 4-Me,
R = 3-Me,
R = 2-Me,
R = 4-i-Bu,
R = 4-OMe,
R = 4-SMe,
, 87%
, 89%
, 88%
EtOH instead of DMSO
MeCN instead of DMSO
(+)Pt/(−)Pt instead of
(+)C/(−)Pt, 10 mA/cm2
(+)Ni/(−)Pt instead of
(+)C/(−)Pt, 10 mA/cm2
no electric current, 24 h
none
77
3la
N
3ea
, 65%
3fa
trace
72
3ma
R = 4-CF3,
, 82%
R = 4-OCF3,
N
3ga
, 86%
R
3oa
3pa
R = 4-CN,
R = 4-Ph,
3ha
, 60%
R = 2-F,
, 88%
18b
75
N
N
N
19
20c
N. R.
71
R
R
O
O
N
N
N
S
aReaction conditions: carbon rod anode, Pt plate cathode
(1cm×1cm), undivided cell, I = 10 mA (10 mA/cm2), 1a
(0.3 mmol), 2a (1.2 mmol), HI (20 mol%, 50% aq), n-
BuNBF4 (0.1 mmol), DMSO (10 mL), under air
atmosphere at 70 oC for 6 h, 7.5 F/mol. bNi plate anode
(1cm×1cm). c1a (5 mmol).
3ta
, 89%
3qa
R = OMe,
R = Cl,
, 95%
3sa
, 86%
3ra
, 83%
N
N
N
N
N
N
3wa
3va, 90%
, n.r.
3ua
, 65%
With the optimized protocol in hand, various kinds of
aryl ketones with benzylamine were examined in scheme
2. Various substituted aryl ketones bearing electron-
donating or electron-withdrawing groups were tested,
furnishing the imidazoles 3aa-3sa in moderate to excellent
yields. Surprisingly, the aryl ketone brings thio- group
reacted with 2a smoothly to afford 3ga in 86% yield,
which indicated that the oxidation pecks of starting
materials is lower than the thio- group. It is worth
mentioning that halogen-substituted ketones 3ha-3la (F,
Cl, Br) were also tolerated in this electrochemical
transformation, but 2-F substituted ketone gave slightly
lower yield. The electron deficient 4-acetylbenzonitrile
was used with 2a, the product 3oa was prepared in 86%
Furthermore, acetophenone with a variety of benzylamines
were tested under electrolytic conditions. As shown in
scheme 3, benzylamine derivatives with various functional
groups such as -Me, -t-Bu, -OMe, -F, -Cl were subjected
to the reaction, a moderate to good yield of corresponding
products 3ab-3ai were provided. When (3,4-
dichlorophenyl)-methanamine
2j
reacted
with
acetophenone 1a under optimized protocol, the 1,2,4-
trisubstitued imidazole 3aj was achieved in 52% yield.
Moreover, heterocyclic methanamine performed smoothly
with 1a, furnishing the corresponding product 3ak in good
yield. However, phenylethylamine and n-propylamine are
not afford the desired product after the reaction.
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Scheme 3. Substrate scope of benzylaminesa
Ph
(a)
O
2.0 equiv I2
H2N
+
N
Ar
20 mol% HI
Ph
DMSO, 70 o
C
N
Ph
Ph
O
H
2a
3aa, trace
1a
N
N
undivided cell
+
Ar
Ph
(b)
(c)
H2N
Ar
O
(+)C/(-)Pt
I = 10 mA
HI, DMSO, 70 oC
(+)C/(-)Pt
H2N
H2N
H2N
I
H
N
+
20 mol% HI
Ph
DMSO, 70 oC, 4 h
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N
3aa, 71%
Ph
3
1a
2
2a
5
O
R
Cl
N
3ab
3ac
standard conditions
R = 4-Me,
R = 2-Me,
, 76%
, 63%
Cl
+
N
Ph
3ad
R = 4-t-Bu,
, 67%
3ae
N
Ph
R = 4-OMe,
, 86%
, 83%
2a
3.0 equiv TEMPO 3aa, trace
1a
3af
R = 4-F,
R = 4-Cl,
R = 3-Cl,
R = 2-Cl,
3.0 equiv BHT
3aa, trace
N
3ag
, 88%
H2N
(d)
3ah
, 85%
, 91%
+
N
Cl
R
3ai
N
OMe
O
Cl
3aj
, 52%
standard
conditions
O
Ph
Ph
Ph
N
N
N
N
N
Ph
Ph
N
O
N
N
N
N
Ph
Ph
N
N
N
N
OMe
Ph
3ak
, 86%
3al
, n.r.
3am
, n.r.
OMe
MeO
MeO
3aa
3a'
3a''
3ae
To get insight into the electrochemical oxidative C-N
bond formation reaction, several control experiments
were carried out (scheme 4). Firstly, 1a and 2a reacted
with stoichiometric iodine as oxidant, 20 mol% HI as
catalyst, no desired product 3aa was detected, and afford
the oxazole in 45% yield3f (scheme 4a). Moreover, 2-
iodo-acetopheneone 5 instead of 1a was investigated
under electrochemical conditions, the 1H-imidazole was
obtained in 71% yield (scheme 4b). In addition, 3.0 equiv
of TEMPO (2,2,6,6-tetramethylpiperidin-1-oxyl) and
BHT (2,6-di-tert-butyl-4-methylphenol) was added to the
electrochemical reaction and only trace of 3aa was
isolated (scheme 4c). The competition experiment of
acetophenone, benzylamine with 4-methoxybenzylamine
were examined, only 43% yield of 3aa was observed
(scheme 4d).
Scheme 4. Control experiments
To further understand the electrochemical oxidative C-
N bond formation process, cyclic voltammograms were
performed in scheme 5. The CV of HI (curve b) exhibited
two oxidation peaks at 0.12 v and 1.1 v vs Ag/AgCl. The
mixture of HI with 1a presented two oxidation peaks at
0.31 v and 1.29 v vs Ag/AgCl (curve c), the pecks of 1.29
v may result from 2-iodo-acetopheneone. In addition, the
oxidation peck of the mixture of HI, 1a and 2a was
observed at 0.81 v vs Ag/AgCl (curve d), due to the
reaction of the mixture is in progress.
Scheme 5. Cyclic voltammogram recorded on (+)C/(-)Pt
in n-BuNBF4 (0.1 mmol)/DMSO (10 mL) at 70 oC;
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Ag/AgCl as reference electrode, at 25 mV/s scan rate: (a)
using CDCl3 as the solvent and TMS as an internal
background; (b) HI (0.06 mmol) ; (c) HI (0.06 mmol) +
1a (0.3 mmol); (d) HI (0.06 mmol) + 1a (0.3 mmol) + 2a
(1.2 mmol).
standard. HRMS were obtained from the Bruker
micrOTOF-Q II. All reagents and solvents are
commercially available compounds and without further
purification. Melting points were recorded a X-4
instrument and were uncorrected.
Based on our experimental results and previous works15,
a plausible reaction mechanism for electrochemical
oxidative tandem cyclization of aryl ketones and
benzylamines was proposed in scheme 6. Firstly, the
molecular iodine is generated via the anodic oxidation of
I-.14 Then, molecular iodine reacted with 1a to formed the
2-iodo-acetopheneone 5,11 which undergoes nucleophilic
substitution/condensation with 2a to afford the
intermediate I. Subsequently, intramolecular oxidative
cyclization of the intermediate I to give the intermediate
III. Finally, the proton elimination/oxidation of the
intermediate III generated the final product 3aa.
2I-
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General procedure: A 25 mL two-necked flask,
equipped with Pt plate cathode (1cm×1cm), carbon rod
anode (ϕ 6 mm), and a magnetic stir bar. The mixture of
acetophenone (0.3 mmol, 36 mg), benzylamine (1.2 mmol,
129 mg), HI (0.06 mmol, 7.7 mg), n-BuNBF4 (0.1 mmol,
33.0 mg) and DMSO (10 mL) was stirred at a constant
o
current of 10 mA under air at 70 C (metal bath) for 6 h.
Upon completion, the mixture was cooled to room
temperature, washed with water, extracted with EtOAc (15
mL×3), dried with anhydrous Na2SO4, and concentrated.
The desired product 3 was obtained by column
chromatography (PE/EtOAc=15:1).
3aa
-e-
O
Gram-Scale synthesis of 3aa. In 250 mL three-necked
flask, equipped with (+)C/(-)Pt electrode, with 1a (5.0
mmol, 601 mg), 2a (20 mmol, 2.14 g), HI (1.0 mmol, 128
mg), n-BuNBF4 (1.5 mmol, 494 mg) and DMSO (100 mL).
The mixture was stirred at a constant current of 10 mA
under air at 70 oC (metal bath). Upon completion
(monitored by TLC), the mixture was cooled to room
temperature, washed with water, extracted with EtOAc (40
mL×3), dried with anhydrous Na2SO4, concentrated, and
purified. The desired product 3aa was obtained in 71%
(1.10 g) yield.
1-benzyl-2,4-diphenyl-1H-imidazole (3aa).6 Yellow
solid, yield 83% (77 mg, PE/EtOAc=15:1 as eluent), mp
116 - 117 °C. 1H NMR (400 MHz, CDCl3) δ 7.83 (d, J =
7.6 Hz, 2H), 7.59 (dd, J = 6.3, 2.7 Hz, 2H), 7.43 - 7.21 (m,
10H), 7.11 (d, J = 7.1 Hz, 2H), 5.18 (s, 2H).13C{1H} NMR
(101 MHz, CDCl3) δ 148.7, 141.5, 136.9, 134.0, 130.4,
129.1, 129.1, 128.7, 128.6, 128.0, 126.9, 126.7, 125.0,
116.9, 50.5.
-2e-
Ph
-2H+
1a
H2
Ph
I2
O
HN
Ph
I
N
+2e-
Ph
5
Ph
III
-H2O
-HI
BnNH2
2a
2H+
Ph
Ph
-2e- -e-
-2H+
Ph
Ph
N
N
NH
N
Ph
Ph
I
II
Scheme 6. Proposed reaction mechanism
In summary, we have discovered a novel and efficient
protocol for the synthesis of 1,2,4-trisubstituted-(1H)-
imidazoles via electrochemical oxidative C-N bond
formation reaction under metal- and oxidant-free
conditions by using readily available starting materials.
This approach exhibited a wide of functional groups
tolerance and provided access to various imidazoles in
moderate to excellent yields.
1-benzyl-2-phenyl-4-(p-tolyl)-1H-imidazole
(3ba).6
Yellow solid, yield 87% (85 mg, PE/EtOAc=15:1 as
1
eluent), mp 126 - 127 °C. H NMR (400 MHz, CDCl3) δ
EXPERIMENTAL SECTION
7.72 (d, J = 8.1 Hz, 2H), 7.57 (m, 2H), 7.34 (dm, 3H), 7.32
- 7.25 (m, 3H), 7.16 - 7.12 (m, 3H), 7.05 (m, 2H), 5.09 (s,
2H), 2.30 (s, 3H). 13C{1H} NMR (101 MHz, CDCl3) δ
148.5, 141.7, 137.1, 136.5, 130.6, 129.1, 129.1, 129.0,
General methods: 1H, 13C and 19F spectra were
recorded a Bruker AVANCE II 400 MHz spectrometer
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128.7, 128.5, 128.3, 128.04, 126.8, 125.0, 116.6, 50.5,
21.41.
1-benzyl-2-phenyl-4-(m-tolyl)-1H-imidazole (3ca).9b
2.4 Hz, 3H), 7.26 - 7.23 (m, 2H), 7.19 (s, 1H), 7.14 - 7.07
(m, 2H), 5.17 (s, 2H), 2.46 (s, 3H). 13C{1H} NMR (101
MHz, CDCl3) δ 148.7, 141.1, 136.8, 136.5, 131.2, 130.4,
129.1, 129.1, 129.0, 128.7, 128.0, 127.0, 126.7, 125.4,
116.7, 50.5, 16.1. HRMS (ESI-TOF) m/z calcd for
C23H21N2S [M+H]+ 357.1420, found 357.1415.
Yellow solid, yield 89% (87 mg, PE/EtOAc=15:1 as
1
eluent), mp 125 - 126 °C. H NMR (400 MHz, CDCl3) δ
7.70 (s, 1H), 7.57 (m, 3H), 7.36 (m, 3H), 7.32 - 7.25 (m,
3H), 7.20 - 7.16 (m, 2H), 7.10 - 7.00 (m, 3H), 5.12 (s, 2H),
2.34 (s, 3H). 13C{1H} NMR (101 MHz, CDCl3) δ 148.5,
141.6, 138.1, 136.9, 133.9, 130.4, 129.0, 129.0, 128.6,
128.4, 128.3, 127.9, 127.62, 126.6, 125.7, 122.1, 116.9,
50.4, 21.5.
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1-benzyl-4-(2-fluorophenyl)-2-phenyl-1H-imidazole
(3ha).9a Yellow solid, yield 60% (59 mg, PE/EtOAc=15:1
as eluent), mp 68 - 69 °C. 1H NMR (400 MHz, CDCl3) δ
8.39 - 8.23 (m, 1H), 7.60 (m, 2H), 7.48 (d, J = 4.0 Hz, 1H),
7.42 (m, 3H), 7.34 (m, 3H), 7.23 - 7.18 (m, 2H), 7.16 - 7.04
(m, 3H), 5.24 (s, 2H). 13C{1H} NMR (101 MHz, CDCl3) δ
159.7 (d, J = 245.8 Hz) 148.1, 136.8, 135.0 (d, J = 1.9 Hz),
130.3, 129.1, 129.0 (d, J = 2.8 Hz), 128.7, 128.0, 127.7 (d,
J = 4.3 Hz), 127.6 (d, J = 8.5 Hz), 126.6, 124.3 (d, J = 3.1
Hz), 121.2 (d, J = 14.3 Hz), 115.4 (d, J = 22.0 Hz), 50.5.
19F NMR (376 MHz, CDCl3) δ -114.55.
1-benzyl-2-phenyl-4-(o-tolyl)-1H-imidazole
(3da).7
Yellow solid, yield 88% (86 mg, PE/EtOAc=15:1 as
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eluent), mp 112 - 114 °C. H NMR (400 MHz, CDCl3) δ
7.97 (d, J = 6.8 Hz, 1H), 7.65 - 7.58 (m, 2H), 7.40 - 7.37
(m, 3H), 7.34 - 7.28 (m, 3H), 7.23 - 7.15 (m, 3H), 7.13 -
7.07 (m, 3H), 5.21 (s, 2H), 2.48 (s, 3H). 13C{1H} NMR
(101 MHz, CDCl3) δ 147.8, 140.9, 137.1, 134.9, 133.5,
130.8, 130.5, 129.1, 129.0, 129.0, 128.7, 128.6, 128.0,
126.9, 126.6, 126.0, 119.7, 50.5, 22.0.
1-benzyl-4-(4-chlorophenyl)-2-phenyl-1H-imidazole
(3ia).6 Yellow solid, yield 89% (92 mg, PE/EtOAc=15:1
as eluent), mp 125 - 127 °C. 1H NMR (400 MHz, CDCl3)
δ 7.84 - 7.68 (m, 2H), 7.65 - 7.55 (m, 2H), 7.45 - 7.39 (m,
3H), 7.32 (m, 5H), 7.20 (s, 1H), 7.11 (m, 2H), 5.18 (s, 2H).
13C{1H} NMR (101 MHz, CDCl3) δ 148.8, 140.5, 136.7,
132.7, 132.3, 130.3, 129.2, 129.1, 129.0, 128.7, 128.7,
128.1, 126.7, 126.2, 117.02, 50.6.
1-benzyl-4-(4-isobutylphenyl)-2-phenyl-1H-imidazole
(3ea, PE/EtOAc=15:1 as eluent).7 Yellow solid, yield 65%
(71 mg), mp 111 - 113 oC. 1H NMR (400 MHz, CDCl3) δ
7.74 (d, J = 8.1 Hz, 2H), 7.59 (dd, J = 6.5, 3.2 Hz, 2H),
7.41 (m, 3H), 7.39 - 7.30 (m, 4H), 7.22 (s, 1H), 7.18 - 7.13
(m, 3H), 5.22 (s, 2H), 2.47 (d, J = 7.2 Hz, 2H), 1.87 (m,
1H), 0.91 (s, 3H), 0.89 (s, 3H). 13C{1H} NMR (101 MHz,
CDCl3) δ 148.5, 141.7, 140.4, 136.9, 131.4, 130.4, 129.4,
129.0, 129.0, 129.0, 128.6, 128.0, 126.7, 124.7, 116.5, 50.5,
45.2, 30.3, 22.4.
1-benzyl-4-(3-chlorophenyl)-2-phenyl-1H-imidazole
(3ja).9a Yellow solid, yield 92% (95 mg, PE/EtOAc=15:1
as eluent), mp 97 - 98 °C. 1H NMR (400 MHz, CDCl3) δ
7.84 (s, 1H), 7.62 - 7.60 (d, J = 7.6 Hz, 1H), 7.49 - 7.47
(m, 2H), 7.33 - 7.32 (m, 3H), 7.28 - 7.26 (m, 3H), 7.25 (s,
2H), 7.21 - 7.13 (m, 1H), 7.07 - 7.04 (m, 2H). 13C{1H}
NMR (101 MHz, CDCl3) δ 148.7, 139.8, 136.3, 135.5,
134.3, 130.2, 129.7, 129.0, 128.9, 128.9, 128.5, 128.2,
128.0, 126.5, 124.9, 123.0, 117.4, 60.3.
1-benzyl-4-(4-methoxyphenyl)-2-phenyl-1H-imidazole
(3fa).6 Yellow solid, yield 82% (84 mg, PE/EtOAc=10:1
as eluent), mp 146 - 148 °C. 1H NMR (400 MHz, CDCl3)
δ 7.82 - 7.72 (m, 2H), 7.63 - 7.55 (m, 2H), 7.40 (dd, J =
5.1, 1.9 Hz, 3H), 7.33 (dd, J = 5.3, 2.2 Hz, 3H), 7.17 - 7.10
(m, 3H), 6.94 - 6.87 (m, 2H), 5.18 (s, 2H), 3.80 (s, 3H).
13C{1H} NMR (101 MHz, CDCl3) δ 158.7, 148.5, 141.4,
137.0, 130.5, 129.0, 129.0, 129.0, 128.7, 128.0, 127.0,
126.7, 126.2, 115.9, 114.0, 55.3, 50.5.
1-benzyl-4-(2-chlorophenyl)-2-phenyl-1H-imidazole
(3ka).9a Yellow solid, yield 93% (96 mg, PE/EtOAc=15:1
as eluent), mp 60 - 62 °C. 1H NMR (400 MHz, CDCl3) δ
8.32 (dd, J = 7.9, 1.7 Hz, 1H), 7.73 (s, 1H), 7.58 (dd, J =
6.6, 3.0 Hz, 2H), 7.38 (dd, J = 5.2, 1.7 Hz, 4H), 7.33 - 7.24
(m, 4H), 7.15 - 7.07 (m, 3H), 5.19 (s, 2H). 13C{1H} NMR
(101 MHz, CDCl3) δ 147.8, 137.5, 136.9, 132.5, 130.8,
130.3, 130.2, 129.8, 129.1, 129.1, 129.1, 128.7, 128.0,
127.6, 127.0, 126.6, 121.74, 50.6.
1-benzyl-4-(4-(methylthio)phenyl)-2-phenyl-1H-
imidazole (3ga). Yellow solid, yield 86% (92 mg,
PE/EtOAc=10:1 as eluent), mp 158 - 159 °C. 1H NMR
(400 MHz, CDCl3) δ 7.79 - 7.71 (m, 2H), 7.62 - 7.55 (m,
2H), 7.40 (dt, J = 4.6, 2.8 Hz, 3H), 7.32 (pd, J = 5.9, 5.1,
1-benzyl-4-(4-bromophenyl)-2-phenyl-1H-imidazole
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(3la).7 Yellow solid, yield 84% (98 mg, PE/EtOAc=15:1
= 8.0, 4.2 Hz, 6H), 7.46 - 7.39 (m, 5H), 7.37 - 7.29 (m,
as eluent), mp 164 - 166 °C. 1H NMR (400 MHz, CDCl3)
δ 7.69 (dd, J = 8.8, 2.1 Hz, 2H), 7.58 (dd, J = 6.6, 3.0 Hz,
2H), 7.46 (d, J = 8.6 Hz, 2H), 7.43 - 7.38 (m, 3H), 7.32
(dd, J = 9.7, 7.3 Hz, 3H), 7.21 (s, 1H), 7.11 (d, J = 6.6 Hz,
2H), 5.18 (s, 2H). 13C{1H} NMR (101 MHz, CDCl3) δ
148.9, 140.5, 136.7, 133.1, 131.6, 130.2, 129.2, 129.1,
129.1, 129.0, 128.7, 128.1, 126.74, 126.7, 126.5, 120.5,
117.1, 50.6.
4H), 7.26 (s, 1H), 7.12 (d, J = 6.8 Hz, 2H), 5.20 (s, 2H).
13C{1H} NMR (101 MHz, CDCl3) δ 148.8, 141.2, 141.0,
139.5, 136.9, 133.1, 130.4, 129.1, 129.1, 128.8, 128.7,
128.1, 127.3, 127.1, 126.9, 126.7, 125.34, 117.1, 50.6.
1-benzyl-4-(3,4-dimethoxyphenyl)-2-phenyl-1H-
imidazole (3qa).8 Yellow solid, yield 95% (105 mg,
PE/EtOAc=8:1 as eluent), mp 105 - 107 °C. 1H NMR (400
MHz, CDCl3) δ 7.55 - 7.45 (m, 2H), 7.36 (d, J = 1.8 Hz,
1H), 7.28 (dd, J = 5.1, 1.8 Hz, 3H), 7.25 - 7.15 (m, 4H),
7.05 (s, 1H), 6.99 (d, J = 6.8 Hz, 2H), 6.74 (d, J = 8.4 Hz,
1H), 5.05 (s, 2H), 3.82 (s, 3H), 3.75 (s, 3H). 13C{1H} NMR
(101 MHz, CDCl3) δ 149.1, 148.4, 148.1, 141.4, 137.0,
130.5, 129.0, 128.7, 128.0, 127.4, 126.6, 117.3, 116.2,
111.3, 108.4, 56.0, 55.9, 50.4.
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1-benzyl-2-phenyl-4-(4-(trifluoromethyl)phenyl)-1H-
imidazole (3ma).6 Yellow solid, yield 75% (85 mg,
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PE/EtOAc=12:1 as eluent), mp 133 - 135 °C. H NMR
(400 MHz, CDCl3) δ 7.92 (d, J = 8.1 Hz, 2H), 7.64 - 7.57
(m, 4H), 7.48 - 7.41 (m, 3H), 7.34 - 7.28 (m, 4H), 7.13 (d,
J = 6.7 Hz, 2H), 5.22 (s, 2H). 13C{1H} NMR (101 MHz,
CDCl3) δ 149.2, 140.3, 137.6, 136.6, 130.2, 129.4, 129.2,
129.1, 128.9, 128.7, 128.5, 128.3, 126.8, 125.6 (q, J = 3.8
Hz), 125.0, 118.1, 50.7. 19F NMR (376 MHz, CDCl3) δ -
62.24.
1-benzyl-4-(3,4-dichlorophenyl)-2-phenyl-1H-
imidazole (3ra).9b Yellow solid, yield 83% (94 mg,
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PE/EtOAc=12:1 as eluent), mp 132 - 134 °C. H NMR
(400 MHz, CDCl3) δ 7.93 (d, J = 1.7 Hz, 1H), 7.64 - 7.54
(m, 3H), 7.45 - 7.29 (m, 7H), 7.21 (s, 1H), 7.11 (d, J = 7.0
Hz, 2H), 5.18 (s, 2H). 13C{1H} NMR (101 MHz, CDCl3) δ
149.06, 139.36, 136.5, 134.3, 132.7, 130.5, 130.2, 130.1,
129.3, 129.2, 129.0, 128.8, 128.2, 126.8, 126.7, 124.2,
117.6, 50.7.
1-benzyl-2-phenyl-4-(4-(trifluoromethoxy)phenyl)-1H-
imidazole (3na). Yellow solid, yield 90% (106 mg,
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PE/EtOAc=10:1 as eluent), mp 165 - 167 °C. H NMR
(400 MHz, CDCl3) δ 7.83 (d, J = 8.7 Hz, 2H), 7.59 (dd, J
= 6.5, 2.8 Hz, 2H), 7.42 (dt, J = 5.9, 3.5 Hz, 3H), 7.33 (dq,
J = 10.6, 5.0, 3.6 Hz, 3H), 7.25 - 7.18 (m, 3H), 7.11 (d, J
= 6.9 Hz, 2H), 5.20 (s, 2H). 13C{1H} NMR (101 MHz,
CDCl3) δ 148.9, 148.0, 148.0, 140.3, 136.7, 133.0, 130.2,
129.2, 129.1, 129.0, 128.7, 128.1, 126.7, 126.2, 121.2,
117.1, 50.6. 19F NMR (376 MHz, CDCl3) δ -57.78. HRMS
(ESI-TOF) m/z calcd for C23H18N2F3O [M+H]+ 395.1366,
found 395.1371.
4-(benzo[d][1,3]dioxol-5-yl)-1-benzyl-2-phenyl-1H-
imidazole (3sa). Yellow solid, yield 86% (91 mg,
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PE/EtOAc=10:1 as eluent), mp 161 - 162 °C. H NMR
(400 MHz, CDCl3) δ 7.59 - 7.57 (m, 2H), 7.39 (dd, J = 4.8,
1.6 Hz, 3H), 7.33 - 7.31 (m, 5H), 7.11 (d, J = 6 Hz, 3H),
6.80 (d, J = 8.4 Hz, 1H), 5.91 (s, 2H), 5.17 (s, 2H). 13C{1H}
NMR (101 MHz, CDCl3) δ 148.4, 147.9, 141.4, 140.3,
136.9, 130.4, 129.1, 129.0, 128.7, 128.6, 128.4, 127.0,
126.7, 118.4, 116.1, 108.5, 105.8, 100.9, 53.2. HRMS
(ESI-TOF) m/z calcd for C23H18N2O2 [M+H]+ 354.1363,
found 354.1365.
4-(1-benzyl-2-phenyl-1H-imidazol-4-yl)benzonitrile
(3oa). Yellow solid, yield 86% (86 mg, PE/EtOAc=12:1 as
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eluent), mp 152 - 154 °C. H NMR (400 MHz, CDCl3) δ
8.00 - 7.87 (m, 2H), 7.67 - 7.57 (m, 4H), 7.47 - 7.41 (m,
3H), 7.40 - 7.32 (m, 4H), 7.17 - 7.10 (m, 2H), 5.23 (s, 2H).
13C{1H} NMR (101 MHz, CDCl3) δ 149.4, 139.6, 138.5,
136.4, 132.5, 129.9, 129.5, 129.2, 129.0, 128.8, 128.3,
126.8, 125.2, 119.4, 118.73, 109.7, 50.7. HRMS (ESI-TOF)
m/z calcd for C23H18N3 [M+H]+ 336.1495, found 336.1489.
4-([1,1'-biphenyl]-4-yl)-1-benzyl-2-phenyl-1H-
1-benzyl-2-phenyl-4-(thiophen-2-yl)-1H-imidazole
(3ta).8 Yellow solid, yield 89% (84 mg, PE/EtOAc=15:1
as eluent), mp 98 - 100 °C. 1H NMR (400 MHz, CDCl3) δ
7.62 - 7.52 (m, 2H), 7.43 - 7.36 (m, 3H), 7.33 - 7.28 (m,
4H), 7.15 (dd, J = 5.1, 1.0 Hz, 1H), 7.13 - 7.06 (m, 3H),
7.00 (dd, J = 5.0, 3.6 Hz, 1H), 5.15 (s, 2H). 13C{1H} NMR
(101 MHz, CDCl3) δ 148.5, 137.9, 136.8, 136.7, 130.1,
129.2, 129.1, 129.1, 128.7, 128.1, 127.6, 126.7, 123.4,
122.1, 116.3, 50.5.
imidazole (3pa).9b Yellow solid, yield 88% (100 mg,
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PE/EtOAc=15:1 as eluent), mp 128 - 130 °C. H NMR
(400 MHz, CDCl3) δ 7.90 (d, J = 8.3 Hz, 2H), 7.61 (dd, J
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2H), 1.32 (s, 9H), 1.31 (s, 9H). 13C{1H} NMR (101 MHz,
(3ua).9b Yellow solid, yield 65% (70 mg, PE/EtOAc=15:1
as eluent), mp 126 - 127 °C. 1H NMR (400 MHz, CDCl3)
δ 8.72 - 8.56 (m, 1H), 7.88 - 7.85 (m, 1H), 7.83 - 7.79 (m,
2H), 7.72 - 7.65 (m, 2H), 7.52 - 7.46 (m, 3H), 7.45 - 7.42
(m, 2H), 7.38 - 7.37 (m, 2H), 7.35 - 7.32 (m, 2H), 7.26 (d,
J = 7.1 Hz, 2H), 7.20 (d, J = 7.1 Hz, 2H), 5.32 (s, 2H).
13C{1H} NMR (101 MHz, CDCl3) δ 148.3, 140.8, 137.0,
134.0, 131.9, 131.3, 130.5, 129.1, 129.1, 129.0, 128.7,
128.3, 128.0, 127.7, 126.7, 126.7, 126.1, 126.0, 125.6,
125.5, 120.0, 50.6.
CDCl3) δ 152.7, 151.9, 150.7, 144.4, 134.0, 133.6, 132.1,
128.7, 128.3, 127.7, 127.6, 126.3, 126.0, 125.9, 125.8, 51.2,
34.9, 34.7, 31.5, 31.4. HRMS (ESI-TOF) m/z calcd for
C30H35N2 [M+H]+ 423.2795, found 423.2798.
1-(4-methoxybenzyl)-2-(4-methoxyphenyl)-4-phenyl-
1H-imidazole (3ae).9b Yellow solid, yield 86% (96 mg,
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PE/EtOAc=10:1 as eluent), mp 117 - 119 °C. H NMR
(400 MHz, CDCl3) δ 7.81 (d, J = 7.2 Hz, 2H), 7.58 - 7.50
(m, 2H), 7.34 (t, J = 7.7 Hz, 2H), 7.24 - 7.18 (m, 2H), 7.04
(d, J = 8.6 Hz, 2H), 6.97 - 6.91 (m, 2H), 6.90 - 6.84 (m,
2H), 5.09 (s, 2H), 3.81 (s, 3H), 3.78 (s, 3H). 13C{1H} NMR
(101 MHz, CDCl3) δ 160.2, 159.3, 134.2, 130.5, 128.9,
128.5, 128.1, 126.7, 124.9, 123.0, 116.5, 114.4, 114.1, 55.4,
55.3, 50.0.
1-benzyl-4-(naphthalen-2-yl)-2-phenyl-1H-imidazole
(3va).9b Yellow solid, yield 90% (97 mg, PE/EtOAc=15:1
as eluent), mp 136 - 138 °C. 1H NMR (400 MHz, CDCl3)
δ 8.38 (s, 1H), 7.89 - 7.82 (m, 2H), 7.82 - 7.75 (m, 2H),
7.64 - 7.56 (m, 2H), 7.39 (td, J = 6.3, 4.3 Hz, 5H), 7.34 -
7.24 (m, 4H), 7.08 (d, J = 6.6 Hz, 2H), 5.13 (s, 2H). 13C{1H}
NMR (101 MHz, CDCl3) δ 148.9, 141.5, 136.9, 133.9,
132.7, 131.5, 130.4, 129.2, 129.1, 129.1, 128.8, 128.2,
128.2, 128.1, 127.7, 126.8, 126.2, 125.4, 123.8, 123.1,
117.5, 50.6.
1-(4-fluorobenzyl)-2-(4-fluorophenyl)-4-phenyl-1H-
imidazole (3af, ).9b Yellow solid, yield 83% (86 mg,
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PE/EtOAc=15:1 as eluent), mp 82-83 °C. H NMR (400
MHz, CDCl3) δ 7.81 (d, J = 7.4 Hz, 2H), 7.54 (dd, J = 8.6,
5.4 Hz, 2H), 7.37 (t, J = 7.5 Hz, 2H), 7.25 (t, J = 5.9 Hz,
2H), 7.14 - 6.99 (m, 6H), 5.15 (s, 2H). 13C{1H} NMR (101
MHz, CDCl3) δ 163.2 (d, J = 250.5 Hz), 162.4 (d, J = 248.3
Hz), 147.6, 141.6, 133.8, 132.4 (d, J = 3.3 Hz), 131.0 (d, J
= 8.5 Hz), 128.6, 128.4 (d, J = 8.1 Hz), 127.0, 126.5 (d, J
= 3.4 Hz), 124.9, 116.7, 116.1 (d, J = 21.7 Hz), 115.8 (d, J
= 21.8 Hz), 49.9. 19F NMR (376 MHz, CDCl3) δ -111.51,
-113.71.
1-(4-methylbenzyl)-4-phenyl-2-(p-tolyl)-1H-imidazole
(3ab).9b Yellow solid, yield 76% (77 mg, PE/EtOAc=15:1
as eluent), mp 94 - 95 °C.1H NMR (400 MHz, CDCl3) δ
7.86 - 7.78 (m, 2H), 7.50 (dd, J = 8.3, 1.8 Hz, 2H), 7.38 -
7.33 (m, 2H), 7.24 - 7.21 (m, 4H), 7.16 (d, J = 7.9 Hz, 2H),
7.03 (d, J = 8.0 Hz, 2H), 5.16 (s, 2H), 2.38 (s, 3H), 2.34 (s,
3H). 13C{1H} NMR (101 MHz, CDCl3) δ 148.7, 141.3,
139.0, 137.8, 134.1, 133.9, 129.7, 129.3, 129.0, 128.5,
127.6, 126.7, 126.7, 124.9, 116.6, 50.3, 21.4, 21.2.
1-(2-methylbenzyl)-4-phenyl-2-(o-tolyl)-1H-imidazole
(3ac).8 Yellow solid, yield 63% (64 mg, PE/EtOAc=15:1
as eluent), mp 104 - 106 °C. 1H NMR (400 MHz, CDCl3)
δ 8.16 - 7.97 (m, 2H), 7.44 (t, J = 7.6 Hz, 2H), 7.38 - 7.22
(m, 4H), 7.22 - 7.04 (m, 5H), 6.59 (d, J = 7.1 Hz, 1H), 5.03
(s, 2H), 2.20 (s, 3H), 2.14 (s, 3H). 13C{1H} NMR (101
MHz, CDCl3) δ 151.0, 143.6, 138.5, 134.4, 134.3, 133.6,
130.6, 130.2, 130.0, 129.9, 129.8, 128.2, 127.6, 127.5,
127.4, 126.5, 125.7, 125.59, 115.4, 48.6, 19.8, 19.1.
1-(4-(tert-butyl)benzyl)-2-(4-(tert-butyl)phenyl)-4-
phenyl-1H-imidazole (3ad). Yellow solid, yield 67% (85
mg, PE/EtOAc=15:1 as eluent), mp 127 - 128 °C. 1H NMR
(400 MHz, CDCl3) δ 8.02 (d, J = 7.4 Hz, 2H), 7.48 (m,
3H), 7.45 - 7.33 (m, 7H), 6.98 (d, J = 8.2 Hz, 2H), 5.32 (s,
1-(4-chlorobenzyl)-2-(4-chlorophenyl)-4-phenyl-1H-
imidazole (3ag).9b Yellow solid, yield 88% (100 mg,
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PE/EtOAc=15:1 as eluent), mp 100 - 102 °C. H NMR
(400 MHz, CDCl3) δ 7.80 (d, J = 7.5 Hz, 2H), 7.47 (d, J =
8.4 Hz, 2H), 7.41 - 7.32 (m, 4H), 7.30 (d, J = 8.4 Hz, 2H),
7.26 - 7.19 (m, 2H), 6.99 (d, J = 8.3 Hz, 2H), 5.11 (s, 2H).
13C{1H} NMR (101 MHz, CDCl3) δ 147.4, 141.9, 135.3,
135.1, 134.0, 133.7, 130.2, 129.3, 129.0, 128.7, 128.7,
127.9, 127.1, 125.0, 117.1, 49.9.
1-(3-chlorobenzyl)-2-(3-chlorophenyl)-4-phenyl-1H-
imidazole (3ah).7 Yellow solid, yield 85% (96 mg,
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PE/EtOAc=15:1 as eluent), mp 125 - 127 °C. H NMR
(400 MHz, CDCl3) δ 8.07 - 7.96 (m, 2H), 7.56 - 7.52 (m,
1H), 7.48 - 7.26 (m, 9H), 7.06 (s, 1H), 6.93 - 6.84 (m, 1H),
5.28 (s, 2H). 13C{1H} NMR (101 MHz, CDCl3) δ 150.3,
145.1, 138.2, 135.1, 134.8, 133.4, 131.8, 130.4, 130.0,
129.7, 129.1, 128.3, 128.2, 127.8, 127.7, 126.6, 126.3,
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124.2, 117.6, 50.8.
Dong, V. M. Catalytic Dehydrogenative Cross-Coupling:
1-(2-chlorobenzyl)-2-(2-chlorophenyl)-4-phenyl-1H-
imidazole (3ai).8 Yellow solid, yield 91% (103 mg,
Forming Carbon-Carbon Bonds by Oxidizing Two
Carbon-Hydrogen Bonds. Chem. Rev. 2011, 111, 1215; (c)
Xie, L.-Y.; Qu, J.; Peng, S.; Liu, K.-J.; Wang, Z.; Ding,
M.-H.; Wang, Y.; Cao, Z.; He, W.-M. Selectfluor-
mediated regioselective nucleophilic functionalization of
N-heterocycles under metal- and base-free conditions.
Green Chem. 2018, 20, 760; (d) Xie, L.-Y.; Peng, S.; Jiang,
L.-L.; Peng, X.; Xia, W.; Yu, X.; Wang, X.-X.; Cao, Z.;
He, W.-M. AgBF4-catalyzed deoxygenative C2-amination
of quinoline N-oxides with isothiocyanates. Org. Chem.
Front. 2019, 6, 167.
1
PE/EtOAc=15:1 as eluent), mp 135 - 136 °C. H NMR
(400 MHz, CDCl3) δ 7.81 (d, J = 7.5 Hz, 2H), 7.46 (d, J =
7.7 Hz, 2H), 7.33 (td, J = 14.7, 12.6, 7.0 Hz, 5H), 7.26 -
7.12 (m, 4H), 6.91 (d, J = 7.2 Hz, 1H), 5.08 (s, 2H). 13C{1H}
NMR (101 MHz, CDCl3) δ 146.0, 141.6, 134.7, 134.0,
133.9, 133.1, 132.8, 131.1, 130.0, 129.8, 129.6, 129.3,
128.6, 127.3, 127.1, 126.9, 124.9, 115.9, 48.2.
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1-(3,4-dichlorobenzyl)-2-(3,4-dichlorophenyl)-4-
phenyl-1H-imidazole (3aj).8 Yellow solid, yield 52% (70
mg, PE/EtOAc=12:1 as eluent), mp 186 - 187 °C. 1H NMR
(400 MHz, CDCl3) δ 8.02 - 7.95 (m, 2H), 7.64 (d, J = 1.9
Hz, 1H), 7.49 - 7.41 (m, 4H), 7.39 - 7.33 (m, 2H), 7.26 (s,
1H), 7.17 (d, J = 1.8 Hz, 1H), 6.84 (dd, J = 8.3, 1.9 Hz,
1H), 5.27 (s, 2H). 13C{1H} NMR (101 MHz, CDCl3) δ
149.3, 145.4, 136.1, 134.2, 133.6, 133.3, 133.1, 132.4,
131.3, 130.8, 129.8, 129.5, 128.4, 128.4, 128.1, 128.0,
127.6, 127.5, 125.2, 117.4, 50.4.
[2] (a) Bariwal, J.; Eycken, E. V. D. C-N bond forming
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Kanyiva, K. S.; Tane, M.; Shibata, T. Iodine-Catalyzed
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H/N-H Annulation of Indolocarboxamides with Arynes:
Construction of Tetracyclic Indoloquinoline Alkaloids.
Org. Lett. 2018, 20, 220; (f) Gao, Q.; Fei, Z.; Zhu, Y.; Jia,
2-(furan-2-yl)-1-(furan-2-ylmethyl)-4-phenyl-1H-
imidazole (3ak).9a Yellow solid, yield 86% (75 mg,
1
PE/EtOAc=15:1 as eluent), mp 103 - 104 °C. H NMR
(400 MHz, CDCl3) δ 7.85 - 7.76 (m, 2H), 7.56 - 7.52 (m,
1H), 7.39 - 7.33 (m, 3H), 7.26 - 7.20 (m, 2H), 6.94 (d, J =
3.4 Hz, 1H), 6.53 (dd, J = 3.4, 1.8 Hz, 1H), 6.33 (dd, J =
3.1, 1.9 Hz, 1H), 6.29 (d, J = 3.2 Hz, 1H), 5.36 (s, 2H).
13C{1H} NMR (101 MHz, CDCl3) δ 149.3, 145.4, 143.1,
142.8, 141.7, 139.1, 133.7, 128.5, 127.0, 125.0, 116.7,
111.6, 110.7, 110.3, 109.0, 43.9.
ACKNOWLEDGMENT
This work was supported by Natural Science Foundation
of China (No. 51974122), National Natural Science
Foundation of Hunan Province (No. 2019JJ50214).
1
Supporting Information Available: The copies of H,
13C and 19F NMR spectra (PDF). This material is available
free of charge via the Internet at http://pubs.acs.org.
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