Copper-mediated formal [5+1] annulation of 2-vinylanilines and glyoxylic acid: A facile approach for the synthesis of 4-arylated quinolines

Article abstract of DOI:10.1016/j.tet.2020.131832

A copper-mediated formal [5 + 1] oxidative annulation of 2-vinylanilines and glyoxylic acid to 4-arylated quinolines was developed. A series of 4-arylated quinoline derivatives were obtained in good to excellent yields. This protocol could be carried out efficiently on gram scale. The transformation probably underwent nucleophilic addition/6π electrocyclization/oxidative aromatization and the elimination of CO₂ cascade processes.

Full text of DOI:10.1016/j.tet.2020.131832

Tetrahedron xxx (xxxx) xxx
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Copper-mediated formal [5þ1] annulation of 2-vinylanilines and
glyoxylic acid: A facile approach for the synthesis of 4-arylated
quinolines
,
Yunyu Xiang a, Puying Luo b **, Tianxin Hao a, Weikang Xiong a, Xiaolin Song a,
,
*
Qiuping Ding a
a Key Laboratory of Small Functional Organic Molecule, Ministry of Education and Jiangxi’s Key Laboratory of Green Chemistry, Jiangxi Normal University,
Nanchang, Jiangxi, 330022, PR China
b Department of Gynecology, Jiangxi Provincial People’s Hospital, Nanchang, Jiangxi, 330006, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
A copper-mediated formal [5 þ 1] oxidative annulation of 2-vinylanilines and glyoxylic acid to 4-arylated
quinolines was developed. A series of 4-arylated quinoline derivatives were obtained in good to excellent
yields. This protocol could be carried out efficiently on gram scale. The transformation probably un-
Received 3 October 2020
Received in revised form
25 November 2020
Accepted 30 November 2020
Available online xxx
derwent nucleophilic addition/6
cascade processes.
p
electrocyclization/oxidative aromatization and the elimination of CO2
© 2020 Elsevier Ltd. All rights reserved.
Keywords:
2-Vinylanilines
Quinolones
Glyoxylic acid
Oxidation
Decarboxylation
1. Introduction
made, the development of new strategies for more efficiently
construction of quinoline scaffolds is still desirable.
Quinolines are privileged structural motifs, which can be found
in many pharmaceuticals and biologically active natural products
(Fig. 1) [1,2], such as Quinine, Aablaquine, Amodiaquine, Prima-
quine, Mefloquine, Pitavastain, Piperaquine and so on. Many
quinoline-containing molecules possess diverse activities, such as
antimalarial, anticancer, anti-inflammatory, anti-HIV, antibacterial,
and antituberculosis activities [1e,2]. Owing to the great impor-
tance of quinoline and its derivatives, great efforts have been made
on the development of efficient methods for the synthesis of them.
The general protocols for the construction of quinoline ring
including Skraup reaction [3], GouldeJacobs [4], Doebnerꢀvon
Miller [5], Niementowski [6], Knorr [7], ConradꢀLimpach [8], Pfit-
Recently, decarboxylative coupling reaction is a valuable alter-
native to forming carbon-carbon or carbon-heteroatom bond [14],
which has been widely used in organic synthesis. Readily available
glyoxylic acid and its derivatives can serve as decarboxylative
coupling reagent [15]. In 2012, Gooben reported the decarbox-
ylative allylation of glyoxylic acids with diallyl carbonate [16]. In
2017, Wang and co-works reported the formylation reactions using
glyoxylic acid and diethoxyacetic acid as formyl equivalents [17]. Xu
group developed an Ir-photoredox-catalyzed decarboxylative
Michael addition [18]. In 2018, Tao group reported the Pd-catalyzed
hydroformylation of terminal arylacetylenes using glyoxylic acid as
formyl source [19]. Wu reported the 3-formylation of indoles via Ni-
catalyzed dehydrogenative-decarboxylative coupling with glyox-
ylic acid [20]. Recently, Huang also reported the formylation of
amines through electrochemical decarboxylation of glyoxylic acid
[21].
€
zinger [9], Friedlander reaction [10], Povarov Reaction [11], and
some other protocols [12,13]. Although great progresses have been
2-Vinylanilines have been evidenced as versatile synthetic re-
agents in modern organic syntheses. A range of functionalized N-
heterocyles, such as quinolones [13b,22], indoles [23], quinolone-2-
thiones [24], cinnolines [25], indazoles [26], and 2-quinolinones
* Corresponding author.
** Corresponding author.
E-mail addresses: luopuying1979@126.com (P. Luo), dingqiuping@jxnu.edu.cn
(Q. Ding).
https://doi.org/10.1016/j.tet.2020.131832
0040-4020/© 2020 Elsevier Ltd. All rights reserved.
Please cite this article as: Y. Xiang, P. Luo, T. Hao et al., Copper-mediated formal [5þ1] annulation of 2-vinylanilines and glyoxylic acid: A facile
approach for the synthesis of 4-arylated quinolines, Tetrahedron, https://doi.org/10.1016/j.tet.2020.131832

Y. Xiang, P. Luo, T. Hao et al.
Tetrahedron xxx (xxxx) xxx
Table 1
Optimization of the reaction conditionsa.
entry
co-oxidant (1.5 equiv)
solvent
yield %b
1
2
3
4
5
6
7
8
Cu2O
CuCl
CuI
CuSO4
CuCO3$Cu(OH)2
Cu(NO3)2$3H2O
Cu(OAc)2
AgOAc
K2S2O8
e
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMF
CH3CN
1,4-dioxane
EtOH
toluene
DCE
THF
DMSO
DMSO (80 ꢁC)
DMSO (50 ꢁC)
51
80
trace
71
53
47
90
36
31
trace
N.R.
74
72
36
35
18
28
75
9
10
11c
12d
13
14
15
16
17
18
19
20
21
22
e
Cu(OAc)2
Cu(OAc)2
Cu(OAc)2
Cu(OAc)2
Cu(OAc)2
Cu(OAc)2
Cu(OAc)2
Cu(OAc)2
Cu(OAc)2 (0.5 equiv)
Cu(OAc)2
Cu(OAc)2
Fig. 1. Some quinoline-containing bioactive molecules.
[27], have been prepared via cascade C(sp2)-H activation/cycliza-
tion of 2-vinylanilines. Such transformations could proceed well,
with or without transition-metal. For instance, a number of useful
N-heterocycles have been obtained efficiently promoted by several
kinds of transition-metal, such as Rh, Pd, Ru, and Cu catalysts.
Recently, the group of Ma [22e], Cheng [13b], Yan [22c], Zeng
[22a,b], and us [22d] described the transition-metal-catalyzed
C(sp2)-H activation/annulation of 2-vinylanilines to give function-
alized quinolines. Meanwhile, the synthesis of some indoles, qui-
nolone-2-thiones, cinnolines, and 2-quinolinones were reported
under transition-metal-free conditions promoted by Brønsted acid
or base. In 2018, Quan and co-workers reported the synthesis of
quinoline-2-thiones via base-catalyzed thio-lactamization of 2-
vinylanilines with CS2 [24].
trace
59
90
76
a
Reaction conditions: 1a (0.2 mmol), glyoxylic acid 2 (0.4 mmol, 2.0 equiv), co-
oxidant (1.5 equiv), and solvent (2 mL) with stirring at 130 ꢁC for 1.5 h under air
atmosphere.
b
Isolated yields of 3a.
Under oxygen (O2) condition.
Under nitrogen (N2) condition.
c
d
80 ꢁC (Table 1, entry 21, 90%). However, the yield was obviously
decreased to 76% when the reaction was carried out at 50 ꢁC
(Table 1, entry 22).
Promoted by the aforementioned information and our recent
interest in the synthesis of functionalized quinoline derivatives
[28], we herein report the copper-mediated oxidative annulation of
2-vinylanilines and glyoxylic acid to 4-arylated quinolines.
With the optimized reaction conditions in hand, we investigated
the scope and limitation of 2-vinylanilines 1 (Table 2). Generally,
the results showed that the method was successfully applied to a
wide range of 2-vinylanilines 1. Substrates bearing both electron-
donating (R1 ¼ Me, Bu, OCH3) and electron-withdrawing (R1 ¼ F,
t
2. Results and discussion
Cl, Br, CF3, OCF3) groups on the anilines all worked well to afford the
desired products in good to excellent yields. For example, products
3c and 3d with tertiary butyl and methoxy group were obtained in
92% and 91%, respectively. Substrates containing fluoro and tri-
fluoromethoxy also provided the desired products 3e and 3h both
in high yields. Substitutes (R1) at the meta and ortho positions of the
anilines showed little effect on the efficiency, leading to the cor-
responding quinolines (3j-3o) in moderate to good yields. Next, we
investigated the substitute effect of R2 under the same reaction
conditions. A range of functional group such as methyl, fluoro and
methoxy were tolerated, providing the desired products (3p-3u) in
good yields. While the yield of 4-(4-pentylphenyl) quinolone (3r) is
relative low 65%. It is worthwhile to note that 2-(prop-1-en-2-yl)
aniline also carried out smoothly to afford the desired products (3v)
in moderate yield (41%). Furthermore, 2, 4-dimethyl-6-(1-
phenylvinyl) aniline was amenable for the present protocol,
affording the product 3w in 80% yield. 4-Phenylbenzo[h]quinoline
(3x) was obtained in 94% yield from corresponding substrate.
Then, to illustrate the synthetic utility of this transformation, a
gram-scale synthesis of quinoline 3a was performed (Scheme 1).
The result showed that the approach could be carried out on gram
2-(1-Phenylvinyl)aniline 1a was chosen as a model substrate to
optimize the reaction conditions using various co-oxidants and
solvents. Firstly, we found that the desired product 3a was obtained
in 51% yield when the reaction was stirred in the presence of 1.5
equiv of Cu2O in DMSO under air atmosphere for 1.5 h at 130 ꢁC
(Table 1, entry 1). Encouraged by this discovering, we next exam-
ined the effects of other Cu oxidants such as CuCl, CuI, CuSO4,
CuCO3$Cu(OH)2, Cu(NO3)2$3H2O and Cu(OAc)2 (Table 1, entries
2e7). We found that Cu(OAc)2 can provide quinoline 3a in 90% yield
(Table 1, entry 7). However, lower yields were obtained in the
presence of other oxidants such as AgOAc and K2S2O8 (Table 1,
entries 8 and 9). Controlled experiment confirmed that it’s neces-
sity to obtain satisfied results in the presence of copper-oxidant
(Table 1, entries 10 and 11). In addition, air also played important
role in this transformation (Table 1, entry 12). Then, the evaluation
of various other solvents, such as DMF, CH3CN, 1,4-dioxane, EtOH,
toluene, DCE and THF, showed that DMSO still was the best solvent
for this reaction (Table, entries 13e19). Lowering the loading of
Cu(OAc)2 (50 mol%) produced inferior yield (59%, Table 1, entry 20).
Finally, the reaction temperature was examined, and the yield
could maintain a high level when the temperature was reduced to
2

Y. Xiang, P. Luo, T. Hao et al.
Tetrahedron xxx (xxxx) xxx
Table 2
Substrate scopea,b
.
a
The reactions were carried out with 1 (0.2 mmol), Cu(OAc)2 (0.3 mmol), and HCOCO2H$H2O 2 (0.4 mmol) in DMSO (2 mL) at 80 ꢁC for 1.5 h.
Isolated yields.
b
scale (6.0 mmol) smoothly to give the desired product 3a in 83%
yield.
Based on previous reports [15e22] and the results of our control
to provide 2,3-dihydroquinoline 6. Finally, the desired product 3a is
formed from 6 via copper salt-mediated oxidative aromatization
and elimination of CO2 under air atmosphere.
experiments, a plausible mechanism for the synthesis of the 4-
phenylquinoline is illustrated in Scheme 2. Initially, the Lewis
acid Cu(OAc)2-catalyzed nucleophilic addition of 2-vinylanilines 1a
and glyoxylic acid 2 led to intermediate 4, followed by the release of
H2O and formed the intermediate imine 5, which was observed by
3. Conclusion
In summary, we have developed a facile approach for the con-
struction of 4-aryl- and 4-methyl-quinolines from 2-vinylanilines
and commercially available glyoxylic acid. A broad range of 2-
HRMS. Subsequently, imine 5 can undergo a 6
p electrocyclization
3

Y. Xiang, P. Luo, T. Hao et al.
Tetrahedron xxx (xxxx) xxx
Scheme 1. Gram-scale reaction.
Scheme 2. Proposed mechanism for the synthesis of 4-arylated quinoline.
vinylanilines were served as effective substrates, affording to the
corresponding quinolines in good to excellent yields. The trans-
formation could be carried out efficiently on gram scale. Further
investigations on bio-activities of these 4-arylated quinoline de-
rivatives are currently underway in our laboratory.
4.2. 4-Phenylquinoline (3a). Isolated (Rf ¼ 0.4, EtOAc e petroleum
ether ¼ 1:5) as a yellow liquid (36.1 mg, 88% yield)
1H NMR (400 MHz, CDCl3)
d
8.95 (s, 1H), 8.18 (d, J ¼ 8.4 Hz, 1H),
7.92 (d, J ¼ 8.4 Hz, 1H), 7.72 (t, J ¼ 7.2 Hz, 1H), 7.56e7.46 (m, 6H),
7.32 (d, J ¼ 4.0 Hz,1H). 13C{1H}NMR (100 MHz, CDCl3)
d 150.0, 148.7,
148.5, 138.0, 129.9, 129.6, 129.3, 128.6, 128.4, 126.6, 125.9, 121.4.
HRMS (ESI): m/z [M þ H]þ calcd for C15H12Nþ: 206.0964, found:
206.0969.
4. Experimental section
Nuclear magnetic resonance (NMR) spectra are recorded in
parts per million from internal tetramethylsilane on the
d
scale. 1H
4.3. 6-Methyl-4-phenylquinoline (3b)
and 13C{1H} NMR spectra were recorded on a Bruker AV-400
spectrometer operating at 400 MHz and 100 MHz, respectively.
All chemical shift values are quoted in ppm and coupling constants
quoted in Hz. High resolution mass spectrometry (HRMS) spectra
were obtained on a micrOTOF II instrument.
Isolated (Rf ¼ 0.4, EtOAc e petroleum ether ¼ 1:5) as a colorless
liquid (31.5 mg, 72% yield). 1H NMR (400 MHz, CDCl3)
d 8.86 (d,
J ¼ 4.4 Hz, 1H), 8.07 (d, J ¼ 8.6 Hz, 1H), 7.66 (s, 1H), 7.57e7.48 (m,
6H), 7.28 (d, J ¼ 4.4 Hz, 1H), 2.46 (s, 3H). 13C{1H}NMR (100 MHz,
CDCl3)
d 149.1, 147.8, 147.3, 138.3, 136.5, 131.6, 129.6, 129.5, 128.6,
128.3, 126.7, 124.6, 121.4, 21.8. HRMS (ESI): m/z [M þ H]þ calcd for
C
16H14Nþ: 220.1121, found: 220.1125.
4.1. Typical procedure for the synthesis of 4-arylated quinolines
from 2-vinylanilines 1 and glyoxylic acid 2
To a 25 mL Schlenk tube equipped with a stir bar, 2-vinylaniline
1 (0.2 mmol), glyoxylic acid 2 (0.4 mmol) and Cu(OAc)2 (0.3 mmol)
in DMSO (2 mL) were added, the mixture was stirred at 80 ꢁC for
1.5 h. After the completion of the reaction, monitored by TLC, the
mixture was cooled to room temperature. The residue was diluted
with H2O solution (10 mL) and extracted with dichloromethane
(3 ꢂ 10 mL). The solvent concentrated via reduced pressure, and the
residue was purified by silica gel chromatography with petroleum
ether/ethyl acetate (1/5) as the eluent to obtain the product 3.
4.4. 6-(tert-butyl)-4-phenylquinoline (3c)
Isolated (Rf ¼ 0.4, EtOAc e petroleum ether ¼ 1:5) as a colorless
liquid (48.2 mg, 92.3% yield). 1H NMR (400 MHz, CDCl3)
d 8.88 (d,
J ¼ 4.4 Hz,1H), 8.12 (d, J ¼ 8.8 Hz,1H), 7.88 (s,1H), 7.83 (d, J ¼ 8.8 Hz,
1H), 7.55e7.45 (m, 5H), 7.30 (d, J ¼ 4.4 Hz, 1H), 1.34 (s, 9H). 13C{1H}
NMR (100 MHz, CDCl3)
d 149.4, 149.3, 148.3, 147.2, 138.3, 129.5,
129.3, 128.5, 128.4, 128.2, 126.3, 121.4, 120.7, 35.1, 31.1. HRMS (ESI):
m/z [M þ H]þ calcd for C19H20Nþ: 262.1590, found: 262.1581.
4

Y. Xiang, P. Luo, T. Hao et al.
Tetrahedron xxx (xxxx) xxx
4.5. 6-Methoxy-4-phenylquinoline (3d)
4.11. 7-Methyl-4-phenylquinoline (3j)
Isolated (Rf ¼ 0.4, EtOAc e petroleum ether ¼ 1:5) as a yellow
solid (42.4 mg, 91% yield); mp: 62e64 ꢁC. 1H NMR (400 MHz, CDCl3)
Isolated (Rf ¼ 0.4, EtOAc e petroleum ether ¼ 1:5) as a yellow
solid (34.9 mg, 80% yield); mp: 66e68 ꢁC. 1H NMR (400 MHz,
d
8.79 (d, J ¼ 4.4 Hz, 1H), 8.07 (d, J ¼ 9.2 Hz, 1H), 7.55e7.47 (m, 5H),
CDCl3)
d
8.84 (d, J ¼ 4.4 Hz, 1H), 8.06 (d, J ¼ 8.4 Hz, 1H), 7.59 (dd,
7.38 (dd, J ¼ 9.2, 2.8 Hz, 1H), 7.27 (d, J ¼ 4.4 Hz, 1H), 7.19 (d,
J ¼ 8.2, 7.2 Hz, 1H), 7.47e7.39 (m, 3H), 7.32e7.20 (m, 3H), 7.19 (d,
J ¼ 2.8 Hz, 1H), 3.78 (s, 3H). 13C{1H} NMR (100 MHz, CDCl3)
d
157.9,
J ¼ 4.0 Hz, 1H), 2.01 (s, 3H). 13C{1H} NMR (100 MHz, CDCl3)
d 149.8,
147.5, 147.1, 144.8, 138.4, 131.3, 129.3, 128.7, 128.4, 127.7, 121.8, 121.7,
103.7, 55.4. HRMS (ESI): m/z [M þ H]þ calcd for C16H14NOþ:
236.1070, found: 236.1071.
149.0, 148.6, 142.4, 135.7, 129.9, 128.9, 128.7, 127.9, 127.8, 126.3,
123.5, 24.5. HRMS (ESI): m/z [M þ H]þ calcd for C16H14Nþ: 220.1121,
found: 220.1120.
4.6. 6-Fluoro-4-phenylquinoline (3e)
4.12. 7-Fluoro-4-phenylquinoline (3k)
Isolated (Rf ¼ 0.4, EtOAc e petroleum ether ¼ 1:5) as a yellow
Isolated (Rf ¼ 0.4, EtOAc e petroleum ether ¼ 1:5) as a colorless
liquid (43.5 mg, 98% yield). 1H NMR (400 MHz, CDCl3)
d 8.91 (d,
liquid (36.8 mg, 83% yield). 1H NMR (400 MHz, CDCl3)
d 8.91 (s, 1H),
J ¼ 4.4 Hz, 1H), 8.17 (dd, J ¼ 9.2, 5.6 Hz, 1H), 7.59e7.43 (m, 7H), 7.35
8.01 (d, J ¼ 8.4 Hz,1H), 7.68e7.60 (m, 1H), 7.45e7.37 (m, 5H), 7.26 (s,
(d, J ¼ 4.4 Hz, 1H). 13C{1H} NMR (100 MHz, CDCl3)
d
160.7 (d, 1JC-
1H), 7.14 (t, J ¼ 8.4 Hz, 1H). 13C{1H} NMR (100 MHz, CDCl3)
d 158.3
¼ 246 Hz), 149.3, 148.0, 145.9, 137.6, 132.4 (d,3JC-F ¼ 9.2 Hz), 129.3,
1
2
F
(d, JC-F ¼ 257.3 Hz), 150.3, 150.0, 146.2, 140.4, 129.0 (d, JC-
128.8, 128.7, 127.6 (d, 3JC-F ¼ 9.4 Hz), 121.8, 119.7 (d, 2JC-F ¼ 25.7 Hz),
3
3
¼ 9.4 Hz), 128.5 (d, JC-F ¼ 3.7 Hz), 128.0, 127.7, 126.1 (d, JC-
F
2
109.2 (d, JC-F ¼ 23.0 Hz). HRMS (ESI): m/z [M þ H]þ calcd for
2
¼ 4.1 Hz), 123.6, 117.5, 111.9 (d, JC-F ¼ 21.7 Hz). HRMS (ESI): m/z
F
C
15H11FNþ: 224.0870, found: 224.0873.
[M þ H]þ calcd for C15H11FNþ: 224.0870, found: 224.0875.
4.7. 6-Chloro-4-phenylquinoline (3f)
4.13. 7-Chloro-4-phenylquinoline (3l)
Isolated (Rf ¼ 0.4, EtOAc e petroleum ether ¼ 1:5) as a white
solid (35.5 mg, 74% yield); mp: 62e64 ꢁC. 1H NMR (400 MHz, CDCl3)
Isolated (Rf ¼ 0.4, EtOAc e petroleum ether ¼ 1:5) as a colorless
liquid (38 mg, 80% yield). 1H NMR (400 MHz, CDCl3)
d 8.90 (d,
d
8.92 (d, J ¼ 4.4 Hz, 1H), 8.11 (d, J ¼ 9.0 Hz, 1H), 7.88 (d, J ¼ 2.4 Hz,
J ¼ 4.4 Hz, 1H), 8.13 (d, J ¼ 8.4 Hz, 1H), 7.63e7.54 (m, 2H), 7.44e7.37
1H), 7.65 (dd, J ¼ 9.0, 2.0 Hz, 1H), 7.57e7.50 (m, 3H), 7.49e7.45 (m,
(m, 3H), 7.34e7.27 (m, 3H). 13C{1H} NMR (100 MHz, CDCl3)
d
150.1,
2H), 7.34 (d, J ¼ 4.4 Hz, 1H). 13C{1H} NMR (100 MHz, CDCl3)
d 150.1,
149.6, 148.3, 140.8, 130.8, 129.7, 129.6, 128.9, 127.8, 127.7, 124.9,
124.6. HRMS (ESI): m/z [M þ H]þ calcd for C15H11ClNþ: 240.0575,
found: 240.0580.
147.8, 147.1, 137.3, 132.6, 131.5, 130.3, 129.4, 128.8, 128.7, 127.5, 124.7,
122.1. HRMS (ESI): m/z [M þ H]þ calcd for C15H11ClNþ: 240.0575,
found: 240.0579.
4.8. 6-Bromo-4-phenylquinoline (3g)
4.14. 7-Bromo-4-phenylquinoline (3 m)
Isolated (Rf ¼ 0.4, EtOAc e petroleum ether ¼ 1:5) as a white
solid (41.6 mg, 74% yield); mp: 59e61 ꢁC. 1H NMR (400 MHz, CDCl3)
Isolated (Rf ¼ 0.4, EtOAc e petroleum ether ¼ 1:5) as a yellow
liquid (27.1 mg, 48% yield). 1H NMR (400 MHz, CDCl3)
d 8.94 (d,
d
8.94 (d, J ¼ 4.4 Hz, 1H), 8.05 (s, 1H), 8.04 (d, J ¼ 10.8 Hz, 1H), 7.79
J ¼ 4.4 Hz, 1H), 8.18 (d, J ¼ 8.4 Hz, 1H), 7.92 (d, J ¼ 8.4 Hz,1H), 7.73 (t,
J ¼ 8.0 Hz, 1H), 7.55e7.46 (m, 5H), 7.34 (d, J ¼ 4.4 Hz, 1H). 13C{1H}
(dd, J ¼ 9.0, 2.2 Hz, 1H), 7.56e7.50 (m, 3H), 7.49e7.45 (m, 2H), 7.35
(d, J ¼ 4.4 Hz, 1H). 13C{1H} NMR (100 MHz, CDCl3)
d 150.3, 147.7,
NMR (100 MHz, CDCl3)
d 149.9, 148.7, 148.5, 138.0, 129.8, 129.5,
147.3, 137.3, 132.9, 131.6, 129.4, 128.8, 128.7, 128.0, 122.1, 120.9.
HRMS (ESI): m/z [M þ H]þ calcd for C15H11BrNþ: 284.0069, found:
284.0070.
129.3, 128.6, 128.4, 126.8, 126.6, 125.9, 121.3. HRMS (ESI): m/z [M þ
H]þ calcd for C15H11BrNþ: 284.0069, found:284.0070.
4.15. 8-Methyl-4-phenylquinoline (3n)
4.9. 4-Phenyl-6-(trifluoromethoxy)quinoline (3h)
Isolated (Rf ¼ 0.4, EtOAc e petroleum ether ¼ 1:5) as a yellow
Isolated (Rf ¼ 0.4, EtOAc e petroleum ether ¼ 1:5) as a yellow
solid (47.3 mg, 82% yield); mp: 64e66 ꢁC. 1H NMR (400 MHz, CDCl3)
liquid (40.5 mg, 93% yield). 1H NMR (400 MHz, CDCl3)
d 8.97 (d,
J ¼ 4.4 Hz, 1H), 7.75 (d, J ¼ 8.4 Hz, 1H), 7.57 (d, J ¼ 6.8 Hz, 1H),
d
8.97 (d, J ¼ 3.0 Hz, 1H), 8.22 (d, J ¼ 9.2 Hz, 1H), 7.75 (s, 1H),
7.53e7.46 (m, 5H), 7.37 (dd, J ¼ 8.4, 7.2 Hz, 1H), 7.32 (d, J ¼ 4.4 Hz,
7.61e7.48 (m, 6H), 7.40 (d, J ¼ 4.3 Hz, 1H). 13C{1H} NMR (100 MHz,
1H), 2.87 (s, 3H). 13C{1H} NMR (100 MHz, CDCl3)
d 148.7, 147.8,
CDCl3)
d 150.4, 148.5, 147.2, 147.0, 137.2, 132.1, 129.4, 128.9, 127.1,
138.5,137.4, 129.6,129.5, 128.5, 128.3, 126.8, 126.3,124.0, 121.2, 18.6.
HRMS (ESI): m/z [M þ H]þ calcd for C16H14Nþ: 220.1121, found:
220.1123.
123.3, 122.1, 120.5 (q, 1JC-F ¼ 256.3 Hz), 116.6. HRMS (ESI): m/z [M þ
H]þ calcd for C16H11F3NOþ: 290.0787, found: 290.0780.
4.10. 4-Phenyl-6-(trifluoromethyl)quinoline (3i)
4.16. 8-Methoxy-4-phenylquinoline (3o)
Isolated (Rf ¼ 0.4, EtOAc e petroleum ether ¼ 1:5) as a yellow
solid (38.3 mg, 71% yield); mp: 61e63 ꢁC. 1H NMR (400 MHz, CDCl3)
Isolated (Rf ¼ 0.4, EtOAc e petroleum ether ¼ 1:2) as a yellow
solid (37.6 mg, 80% yield); mp: 103e105 ꢁC.1H NMR (400 MHz,
d
9.04 (d, J ¼ 4.4 Hz, 1H), 8.29 (d, J ¼ 8.8 Hz, 1H), 8.24 (s, H), 7.90 (d,
J ¼ 8.8 Hz, 1H), 7.59e7.48 (m, 5H), 7.43 (d, J ¼ 4.4 Hz, 1H). 13C{1H}
CDCl3)
J ¼ 8.0 Hz,1H), 7.34 (d, J ¼ 4.4 Hz,1H), 7.05 (d, J ¼ 7.2 Hz, 1H), 4.10 (s,
3H). 13C{1H} NMR (100 MHz, CDCl3)
155.6, 148.7, 148.3, 140.7,
d
8.95 (d, J ¼ 4.4 Hz, 1H), 7.52e7.42 (m, 6H), 7.39 (t,
NMR (100 MHz, CDCl3)
d 151.9, 149.7, 149.5, 137.0, 131.2, 129.4,
129.0, 128.9,128.5 (q, 2JC-F ¼ 32.3 Hz), 125.9, 125.0 (q, 3JC-F ¼ 3.0 Hz),
d
1
3
124.0 (q, JC-F ¼ 270.8 Hz), 123.9 (q, JC-F ¼ 4.5 Hz), 122.4. HRMS
(ESI): m/z [M þ H]þ calcd for C16H11F3Nþ: 274.0838, found:
274.0840.
138.3, 129.5, 128.5, 128.3, 127.8, 126.6, 122.0, 117.6, 107.4, 56.1. HRMS
(ESI): m/z [M þ H]þ calcd for C16H14NOþ: 236.1070, found:
236.1079.
5

Y. Xiang, P. Luo, T. Hao et al.
Tetrahedron xxx (xxxx) xxx
4.17. 4-(p-tolyl)quinoline (3p)
J ¼ 8.0 Hz, 1H), 7.50 (t, J ¼ 8.0 Hz, 1H), 7.43 (t, J ¼ 8.0 Hz, 1H), 7.34 (d,
J ¼ 4.4 Hz, 1H), 7.08 (d, J ¼ 7.6 Hz, 1H), 7.05e7.01 (m, 2H), 3.86 (s,
Isolated (Rf ¼ 0.4, EtOAc e petroleum ether ¼ 1:5) as a colorless
3H). 13C{1H} NMR (100 MHz, CDCl3)
d 159.7, 149.9, 148.7, 148.4,
liquid (40.1 mg, 92% yield). 1H NMR (400 MHz, CDCl3)
d
8.92 (d,
139.4, 129.8, 129.7, 129.3, 126.8, 126.6, 126.0, 122.0, 121.2, 115.2,
113.9, 55.4. HRMS (ESI): m/z [M þ H]þ calcd for C16H14NOþ:
236.1070, found: 236.1072.
J ¼ 4.4 Hz, 1H), 8.17 (d, J ¼ 8.4 Hz, 1H), 7.94 (d, J ¼ 8.4 Hz, 1H), 7.71 (t,
J ¼ 8.4 Hz, 1H), 7.48 (t, J ¼ 8.4 Hz, 1H), 7.40 (d, J ¼ 8.0 Hz, 2H),
7.35e7.30 (m, 3H), 2.46 (s, 3H). 13C{1H} NMR (100 MHz, CDCl3)
d
150.0, 148.7, 148.6, 138.4, 135.1, 129.8, 129.5, 129.3, 129.2, 126.9,
4.23. 4-Methylquinoline (3v). Isolated (Rf ¼ 0.4, EtOAc e petroleum
ether ¼ 1:5) as a colorless liquid (12 mg, 41% yield)
126.5, 126.0, 121.3, 21.3. HRMS (ESI): m/z [M þ H]þ calcd for
C
16H14Nþ: 220.1121, found: 220.1126.
1H NMR (400 MHz, CDCl3)
d
8.76 (d, J ¼ 4.4 Hz, 1H), 8.11 (d,
4.18. 4-(4-fluorophenyl)quinoline (3q)
J ¼ 8.4 Hz, 1H), 7.98 (d, J ¼ 8.4 Hz, 1H), 7.70 (t, J ¼ 7.6 Hz, 1H), 7.55 (t,
J ¼ 7.6 Hz, 1H), 7.21 (d, J ¼ 4.0 Hz, 1H), 2.69 (s, 3H). 13C{1H} NMR
Isolated (Rf ¼ 0.4, EtOAc e petroleum ether ¼ 1:5) as a yellow
(100 MHz, CDCl3)
d 150.1, 148.0, 144.3, 130.0, 129.1, 128.3, 126.3,
liquid (35.6 mg, 80% yield). 1H NMR (400 MHz, CDCl3)
d 8.94 (s, 1H),
123.8, 121.8, 18.6. HRMS (ESI): m/z [M þ H]þ calcd for C10H10Nþ:
8.18 (d, J ¼ 8.4 Hz, 1H), 7.87 (d, J ¼ 8.4 Hz, 1H), 7.73 (dd, J ¼ 8.0,
144.0808, found: 144.0812.
7.2 Hz, 1H), 7.54e7.45 (m, 3H), 7.31 (d, J ¼ 4.2 Hz, 1H), 7.22 (t,
J ¼ 8.4 Hz, 2H). 13C{1H} NMR (100 MHz, CDCl3)
d
162.5 (d, JC-
1
4.24. 6,8-Dimethyl-4-phenylquinoline (3w). Isolated (Rf ¼ 0.4,
EtOAc e petroleum ether ¼ 1:5) as a yellow liquid (37.2 mg, 80%
yield)
¼ 246.8 Hz),149.9,148.7,147.4,133.9 (d, 3J CeF ¼ 3.2 Hz),131.3 (d, 2J
F
CeF ¼ 8.2 Hz), 130.0, 129.4, 126.8, 125.6, 121.4, 115.7 (d, 2J
CeF ¼ 21.4 Hz). HRMS (ESI): m/z [M þ H]þ calcd for C15H11FNþ:
224.0870, found: 224.0875.
1H NMR (400 MHz, CDCl3)
(m, 6H), 7.41 (s, 1H), 7.26 (d, J ¼ 4.4 Hz, 1H), 2.83 (s, 3H), 2.40 (s, 3H).
13C{1H} NMR (100 MHz, CDCl3)
148.0, 147.8, 146.4, 138.7, 137.0,
d
8.89 (d, J ¼ 4.4 Hz, 1H), 7.51e7.45
4.19. 4-(4-pentylphenyl)quinoline (3r)
d
136.0, 131.9, 129.6, 128.5, 128.1, 126.8, 122.6, 121.3, 21.8, 18.5. HRMS
(ESI): m/z [M þ H]þ calcd for C17H16Nþ: 234.1277, found: 234.1280.
Isolated (Rf ¼ 0.4, EtOAc e petroleum ether ¼ 1:5) as a yellow
liquid (35.3 mg, 65% yield). 1H NMR (400 MHz, CDCl3)
d 8.92 (d,
J ¼ 4.4 Hz, 1H), 8.17 (d, J ¼ 8.0 Hz, 1H), 7.96 (dd, J ¼ 8.4, 0.8 Hz, 1H),
7.75e7.67 (m, 1H), 7.60e7.46 (m, 1H), 7.44e7.39 (m, 2H), 7.35e7.32
(m, 3H), 2.74e2.68 (m, 2H), 1.70 (d, J ¼ 7.8 Hz, 2H), 1.44e1.36 (m,
4.25. 4-phenylbenzo[h]quinoline (3x). Isolated (Rf ¼ 0.4, EtOAc e
petroleum ether ¼ 1:5) as a white solid (47.9 mg, 94% yield); mp:
111e113 ꢁC
4H), 0.96e0.90 (m, 3H). 13C{1H} NMR (100 MHz, CDCl3)
d 149.9,
1H NMR (400 MHz, CDCl3)
d
8.80 (d, J ¼ 4.4 Hz, 1H), 7.94 (d,
148.7, 148.6, 143.4, 135.3, 129.8, 129.4, 128.6, 126.9, 126.5, 126.0,
121.3, 35.8, 31.6, 31.1, 22.6, 14.0. HRMS (ESI): m/z [M þ H]þ calcd for
J ¼ 9.0 Hz,1H), 7.86 (d, J ¼ 9.0 Hz,1H), 7.75 (d, J ¼ 7.6 Hz,1H), 7.57 (d,
J ¼ 8.4 Hz, 1H), 7.41e7.34 (m, 4H), 7.31e7.27 (m, 2H), 7.22 (d,
J ¼ 4.8 Hz, 1H), 7.04 (t, J ¼ 8.0 Hz, 1H). 13C{1H} NMR (100 MHz,
C
20H22Nþ: 276.1747, found: 276.1750.
4.20. 4-(2-methoxyphenyl)quinoline (3s)
CDCl3)
d 148.6, 147.4, 147.3, 141.6, 131.9, 130.3, 128.7, 128.2, 127.6,
127.5, 127.2, 127.1, 127.0, 125.6, 124.4, 123.3, 122.9. HRMS (ESI): m/z
[M þ H]þ calcd for C19H14Nþ: 256.1121, found: 256.1125.
Isolated (Rf ¼ 0.4, EtOAc e petroleum ether ¼ 1:5) as a white
solid (38.4 mg, 82% yield); mp: 89e92 ꢁC. 1H NMR (400 MHz, CDCl3)
d
8.93 (d, J ¼ 4.4 Hz, 1H), 8.15 (d, J ¼ 8.4 Hz, 1H), 7.67 (t, J ¼ 7.6 Hz,
Declaration of competing interest
1H), 7.61 (d, J ¼ 8.4 Hz, 1H), 7.47e7.40 (m, 2H), 7.31 (d, J ¼ 4.0 Hz,
1H), 7.25 (d, J ¼ 7.2 Hz,1H), 7.08 (d, J ¼ 7.6 Hz,1H), 7.04 (d, J ¼ 8.4 Hz,
The authors declare that they have no known competing
financial interests or personal relationships that could have
appeared to influence the work reported in this paper.
1H), 3.68 (s, 3H). 13C{1H} NMR (100 MHz, CDCl3)
d 156.8, 149.9,
148.4, 145.9, 131.2, 130.0, 129.6, 129.1, 127.5, 126.8, 126.4, 126.2,
122.2, 120.7, 111.2, 55.5. HRMS (ESI): m/z [M þ H]þ calcd for
C
16H14NOþ: 236.1070, found: 236.1072.
Acknowledgement
4.21. 4-(3-fluorophenyl)quinoline (3t)
Thank the National Natural Science Foundation of China
(21662017 and 21961016), and the Natural Science Foundation of
Jiangxi Province of China (20202BAB203003) very much for
financial support.
Isolated (Rf ¼ 0.4, EtOAc e petroleum ether ¼ 1:5) as a colorless
liquid (39.2 mg, 88% yield). 1H NMR (400 MHz, CDCl3)
d 8.94 (d,
J ¼ 4.4 Hz, 1H), 8.19 (d, J ¼ 8.4 Hz, 1H), 7.88 (d, J ¼ 8.4 Hz, 1H), 7.73 (t,
J ¼ 7.6 Hz, 1H), 7.54e7.45 (m, 2H), 7.31 (d, J ¼ 4.0 Hz, 1H), 7.27 (d,
J ¼ 7.6 Hz, 1H), 7.23e7.16 (m, 2H). 13C{1H} NMR (100 MHz, CDCl3)
Appendix A. Supplementary data
1
3
d
162.7 (d, JC-F ¼ 245.9 Hz, 1H), 149.9, 148.7, 147.1, 140.1 (d, JC-
¼ 7.6 Hz), 130.2 (d, 3JC-F ¼ 8.4 Hz), 130.0, 129.5, 126.9, 126.4, 125.5,
Supplementary data to this article can be found online at
https://doi.org/10.1016/j.tet.2020.131832.
F
125.3 (d, 4JC-F ¼ 3.0 Hz, 1H), 121.2, 116.6 (d, 2JC-F ¼ 22 Hz), 115.4 (d,
2JC-F ¼ 20.9 Hz). HRMS (ESI): m/z [M þ H]þ calcd for C15H11FNþ:
224.0870, found: 224.0874.
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7