Oxidative annulations via double C-H bond cleavages: Approach to quinoline derivatives

Article abstract of DOI:10.1002/aoc.6156

An approach to complicated quinoline derivatives catalyzed by rhodium catalytic system via oxidative annulations was proposed. A systematic exploration was completed. All kinds of reaction parameters were determined. And 55 kinds of target molecules were obtained with moderate to high yields. Combination of double oxidants made the conversion proceed smoothly. A clear reaction mechanism was put forward. Adjacent π systems might provide assistance for realizing the activation of relatively unreactive C(5)-H of imidazole rings by forming five-membered metallacycle intermediates. In addition, scaled-up experiment verified the practical applicability.

Full text of DOI:10.1002/aoc.6156

Received: 17 September 2020
DOI: 10.1002/aoc.6156
Revised: 19 December 2020
Accepted: 27 December 2020
F U L L P A P E R
Oxidative annulations via double C H bond cleavages:
Approach to quinoline derivatives
Zhenghui Liu1
Tiancheng Mu5
| Shien Guo2
| Peng Wang3,4
| Zhenzhong Yan1
|
1School of Pharmaceutical and Materials
Engineering, Taizhou University,
Taizhou, China
2State-Province Joint Engineering
Laboratory of Zeolite Membrane
Materials, Institute of Advanced Materials
(IAM), Nanchang, China
An approach to complicated quinoline derivatives catalyzed by rhodium cata-
lytic system via oxidative annulations was proposed. A systematic exploration
was completed. All kinds of reaction parameters were determined. And
55 kinds of target molecules were obtained with moderate to high yields. Com-
bination of double oxidants made the conversion proceed smoothly. A clear
reaction mechanism was put forward. Adjacent π systems might provide assis-
tance for realizing the activation of relatively unreactive C(5) H of imidazole
rings by forming five-membered metallacycle intermediates. In addition,
scaled-up experiment verified the practical applicability.
3Beijing National Laboratory for
Molecular Sciences, Key Laboratory of
Colloid, Interface and Thermodynamics,
CAS Research/Education Center for
Excellence in Molecular Sciences,
Institute of Chemistry, Chinese Academy
of Sciences, Beijing, China
K E Y W O R D S
4School of Chemistry and Chemical
Engineering, Key Laboratory of Green
Chemical Media and Reactions, Ministry
of Education, Collaborative Innovation
Center of Henan Province for Green
Manufacturing of Fine Chemicals, Henan
Normal University, Xinxiang, China
cyclization, homogeneous catalysis, oxidation, quinoline derivative, Rh catalyst
5Department of Chemistry, Renmin
University of China, Beijing, China
Correspondence
Zhenghui Liu, School of Pharmaceutical
and Materials Engineering, Taizhou
University, Taizhou 318000, China.
Email: liuzhenghui@tzc.edu.cn;
liuzhenghui@iccas.ac.cn
Tiancheng Mu, Department of Chemistry,
Renmin University of China, Beijing
100872, China.
Email: tcmu@ruc.edu.cn
Funding information
Zhejiang Province Public Welfare
Technology Application Research Project,
Grant/Award Number: LGG19B060002;
National Natural Science Foundation of
China, Grant/Award Number: 21773307
Appl Organomet Chem. 2021;35:e6156.
wileyonlinelibrary.com/journal/aoc
© 2021 John Wiley & Sons, Ltd.
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https://doi.org/10.1002/aoc.6156

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LIU ET AL.
1 | INTRODUCTION
based catalytic system to achieve the diannulation of
heteroaryls, which provided a feasible way to the modifi-
cations of C (sp2) H bonds. Although these synthetic
methods could be applied to preparation of poly-
substituted quinolines, they were still limited to quino-
line derivatives with relatively simple structures. For
more practical applications, methods for syntheses of
complicated quinoline derivatives were necessary. There-
fore, substituted imidazoles might be a feasible starting
molecules. As for the functionalizations and modifica-
tions of imidazole and imidazole derivatives, there have
been numerous reports.[12] An upsurge has been
witnessed in the exploration of new catalytic conversions
by metal-catalyzed C H activation pathways over the
recent years.[13] We intended to employ alkynes to syn-
thesize quinoline derivatives using substituted imidaz-
oles. In fact, direct C (sp2) H activation catalyzed by
transition metal systems employing alkynes as coupling
participants is doable, conformed to atom-economy, and
owns high site selectivity.[11,14]
Quinoline and its derivatives are extensively existed skel-
etons in privileged heterocyclic scaffold systems and rep-
resent the typical class of heterocycles. They have been
widely used in the pharmaceuticals, synthons,[1]
ligands,[2] and so forth. Some pharmaceutical molecules
containing quinoline structures are shown in Scheme 1.
2-(2-Methylquinolin-4-ylamino)-N-phenylacetamide (a)
is a highly active antileishmanial drug. 4-Methoxy-
2-(3-methyloxiran-2-yl)quinoline (b) and (E)-2-(prop-
1-en-1-yl)quinoline (c), (natural products generated from
the bark of Galipea longiflora trees of the Rutaceae fam-
ily), are the agents of leishmaniasis, valid against the par-
asites Leishmania sp. And N1, N1-diethyl-N6-(6-methoxy-
4-methylquinolin-8-yl)hexane-1,6-diamine (d) is an agent
of Chagas' disease against the protozoan parasite
Trypanosoma cruzy. In addition, quinoline derivatives
can act as versatile precursors with potential tailored
electronic and photonic functions.[3]
An important mission of organic and catalytic chem-
istry is the development of approaches that could realize
readily available precursors transformed into target mole-
cules in an efficient manner.[4] Plentiful preparations of
quinoline derivatives have been put forward since the
late 1800s. Some conventional named reactions of great
antiquity are Conrad–Limpach, Doebner–von Miller,
Pfitzinger, Friedländer, Skraup, and Combes syntheses.[5]
However, there are some drawbacks in these methods,
such as side reactions, less generality, strong acid or basic
conditions, and operational complexity. Recently, more
facile, environmentally friendly and versatile synthetic
methods have been reported. In 2006, Jia et al[6] proposed
a microwave irradiation (300 W) method catalyzed by p-
TsOH with a fast reaction speed. In 2010, Akbari et al[7]
synthesized and used “task-specific” ionic liquids (sul-
fonic acid functionalized ionic liquid) for the preparation
of quinoline derivatives using one-pot synthesis. In 2011,
Hasaninejad et al[8] employed sulfuric acid-modified
polyethylene glycol 6000 (PEG-OSO3H, 3 mol%) hetero-
geneous catalyst under solvent-free condition. In 2014,
Javanshir et al[9] made use of p-toluenesulfonic acid
(PTSA) completed the conversion at room temperature.
In 2018, Zhou et al[10] utilized Cu (NO3)2 and
MgCl2ꢀ6H2O as catalysts for the transformation in etha-
nol. Particularly, in 2016, Shankar et al[11] set up a Ru-
Stimulated by aforementioned and other related liter-
atures coupled with our interest and accumulation in this
field,[11,15] herein, we set up a homogeneous catalytic sys-
tem for the synthesis of quinoline derivatives using oxida-
tive annulations via double C H bond cleavages of
substituted imidazoles with alkyne derivatives.
2 | RESULTS AND DISCUSSION
2.1 | Determination of metal catalysts
Metal compounds with specific ligands or additives
own excellent catalytic abilities. In an initial series of
explorations, eight kinds of frequently used metal com-
plexes were tested for the template reaction (Table 1).
Cobalt and palladium complexes could not provide 3a
(entries 1–3). Moreover, ruthenium and iridium com-
plexes performed better but still with low yields
(entries 4 and 5). Finally, three kinds of rhodium com-
plexes were tested. [Cp*RhCl2]2 gave the highest yield
(entry 8), whereas [Cp*Rh (MeCN)3](SbF6)2 provided
obvious lower yield (entry 7). However, Rh (PPh3)3Cl
offered no product (entry 6). This strongly implied that
ligands played an important role in the catalytic
process.
SCHEME 1 Quinoline derivatives with diverse
pharmacological properties

LIU ET AL.
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TABLE 1 Metal-catalyzed oxidative
annulation of substituted imidazole
with alkyne (template reaction)
Entry
Metal catalyst
[Cp*CoCl2]2
Conversion (%)[a]
Yield (%)[a]
1
2
3
4
5
6
7
8
4
5
<1
<1
<1
15
Pd (OAc)2
Pd (PPh3)2Cl2
[RuCl2(p-cymene)]2
[Cp*IrCl2]2
3
16
13
4
10
Rh (PPh3)3Cl
<1
31
[Cp*Rh (MeCN)3](SbF6)2
[Cp*RhCl2]2
36
97
95
Note. Reaction conditions: 1a, 0.2 mmol; 2a, 0.3 mmol; metal catalyst, 5 mol%; AgOAc 0.4 mmol, O2 (1 atm);
DCE (dichloroethane), 1.5 ml; 120ꢁC; 2 h.
aDetermined by 1H NMR relative to 1,3,5-trimethoxybenzene as an external standard.
2.2 | Selection of oxidants
of oxidants of their combination were tested (exhibited in
Figure 1). Three Ag-containing oxidants performed not so
A proper oxidant was quite vital for an organic oxidation
reaction with sufficient ability to oxidate specific sites and
no destruction by over oxidation. For this purpose, 14 kinds
well with low to moderate yields. Cu (II) salts were gener-
ally employed in this kind of transformation. Therefore,
four kinds of Cu (II) salts were used. Cu(2-EH)2 behaved
FIGURE 1 Comparation of different
oxidants for template reaction. Reaction
conditions: 1a, 0.2 mmol; 2a, 0.3 mmol;
[Cp*RhCl2]2, 5 mol%; oxidant 0.4 mmol, O2
(1 atm); DCE (dichloroethane), 1.5 ml; 120ꢁC;
2 h

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LIU ET AL.
badly, and Cu (OCOCF3)2 gave no product. However, Cu
(OAc)2 and Cu (OAc2)2ꢀH2O provided products with rela-
tively higher yields. It is worth noting that Cu (OAc2)2ꢀH2O
owned an obviously higher yield than Cu (OAc)2, which
indicated that differences of crystal structure were crucial
for the conversion, and it was consistent to previous report
(RhCl3ꢀ3H2O 97% yield vs. RhCl3 18% yield; reductive car-
bonylationofiodobenzenewithCOandH2 toaffordbenzal-
dehyde).[16] Next, some common oxidants were put into
used. K2S2O8 supplied no product, and TEMPO and O2 pro-
vided low yields. Crucially, we tried to combine O2 with
metal salt oxidants. As a result, Cu (OAc)2/O2, AgOAc/O2,
and Cu (OAc)2ꢀH2O/O2 all improved the yields signifi-
cantly, amongwhichAgOAc/O2 gavethehighest 3ayieldof
95%. After that, NaOAc/O2 was tested as a control group.
The elevated yield compared with O2 confirmed the syner-
gisticeffectbetweenO2 andOAc−.
AgOAc/O2 were explored, as shown in Figure 2a.
[Cp*RhCl2]2 dosages of 1% and 2% performed badly,
affording extremely low yields. Elevating the dosage to
3% or 4% showed a sharp enhancement. When the dosage
was 5%, the highest yield was obtained. And further
increasing the dosage of [Cp*RhCl2]2 could not provide
any further improvement of yield. After that, the dosage
of AgOAc was determined (Table S1). Apparently, 0.1–-
0.3 mmol of AgOAc was not enough with 3a yield of
23%–78%. A 0.4-mmol AgOAc was just enough, because
further increasing the dosage of AgOAc could not lead
increase of yield.
2.4 | Effects of solvents
As the media of reactions, solvents strongly affected the
catalytic performances of the system. The effects of eight
representative organic solvents on the catalytic process
were explored (Figure 2b). Polar protic solvents (EtOH
and MeOH) gave medium yields. MeCN provided the
lowest yield; by contrast, dioxane, toluene, and DME per-
formed better. However, DCE offered the highest yield
and thus was the suitable solvent.
2.3 | Optimized dosages of [Cp*RhCl2]2
and AgOAc/O2
After ascertaining the suitable match of [Cp*RhCl2]2 and
AgOAc/O2, the optimized dosages of [Cp*RhCl2]2 and
FIGURE 2 Oxidative annulations via double C H bond cleavages for the preparation of quinoline derivatives from substituted
imidazoles and alkynes. Reaction conditions: 1a, 0.2 mmol; 2a, 0.3 mmol; [Cp*RhCl2]2, 5 mol%; AgOAc 0.4 mmol, O2 (1 atm); DCE
(dichloroethane), 1.5 ml; 120ꢁC; 2 h. Yields were determined by 1H NMR relative to 1,3,5-trimethoxybenzene as an external standard.
(a) Effects of dosage of [Cp*RhCl2]2, (b) effects of solvents, (c) effects of temperature, and (d) kinetic analysis

LIU ET AL.
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2.5 | Effects of temperature
with R1 = various substituent groups were put into
use (3q–3an). They gave 68%–89% yields. It seemed
that electronic effect of R1 had little impact on the
reaction. In addition, versatility of this method was
further explored by changing R4 to diverse groups.
Heteroaryl-substituted acetylenes participated in this
In order to make a thorough investigation of the cata-
lytic system, the effects of the reaction temperature
were tested in the scope from 70ꢁC to 140ꢁC. Tempera-
ture owned a significant effect on the reaction; some-
times, it could even make a difference between no
reaction and full conversion. Here, in the catalytic sys-
tem, 70ꢁC was too low to offer enough energy for the
reaction (Figure 2c). With the increasing temperatures,
the 3a yields increased. And 120ꢁC was high enough
to get the highest yield. In addition, further elevating
the temperature to 130ꢁC or even 140ꢁC did not
improve the yield.
reaction.
Generally
speaking,
examples
using
heteroaryl-substituted acetylenes tended to have rela-
tively lower yields than benzene or aliphatic chain
substituted acetylenes. Specifically, those with electron-
donating heteroaromatic rings (furan and thiophene
rings; 81%–84% yields; 3aq, 3ar, and 3bc) owned
higher yields than those with electron-withdrawing
heteroaromatic rings (pyridine rings; 75%–78%; 3ao,
3ap, 3az, and 3ba). Examples of electron-rich/poor aryl
enabled acetylenes were also tried (74%–88% yields;
3as–3aw). Similarly, those with electron-rich aryl
enabled acetylenes (86%–88% yields; 3as and 3at)
owned higher yields than those with electron-poor aryl
enabled acetylenes (74%–78%; 3au, 3av, and 3aw). As
for asymmetrical aryl–alkyl alkynes, 75%–87% yields
were obtained (3ax–3bc). Because of asymmetry,
isomers were gained in each test. Still, electron-
donating groups promoted the yields. Above all,
55 kinds of quinoline derivatives were synthesized
smoothly.
2.6 | Authentication of component
necessity
A set of control experiments were conducted with the
lack of [Cp*RhCl2]2, AgOAc/O2, or solvent to verify the
indispensability of each component (Table S2). As
expected, the reaction could not proceed without
[Cp*RhCl2]2, AgOAc/O2, or solvent.
2.7 | Kinetic study
Kinetic observations were conducted, and Figure 2d
showed the time-dependent yields of 3a. Initially, 3a
yield increased almost linearly within 50 min. As the
reaction went on, the reaction rate gradually slowed
down to some extent. Finally, the highest yield (95%) was
obtained at 120 min. Further extending the reaction time
to 160 min, 3a yield nearly kept unchanged. This meant
that reaction time of 120 min was suitable for this
transformation.
2.9 | Scaled-up experiment
In order to explore the practical viability of the trans-
formation, a 10 times large-scale experiment was con-
ducted (Scheme 3). A 3a yield of 78% was obtained
after 120 min. And it increased to 91% after 180 min.
This result indicates that the catalytic system could
find potential valuable applications in industrial
production.
2.8 | Substrate scope
2.10 | Reaction mechanism
With the optimized reaction condition, the scope of
this synthesis was explored, as exhibited in Scheme 2.
At the start, substrates with R1 = phenyl or substituted
phenyls were tested (3a–3p). In general, substrates
with R1 = phenyl tended to perform better than those
The process of C H activation catalyzed by Rh (III) has
long been investigated with numerous experimental and
computational results, and thus, the catalytic mechanism
owned a relatively clear profile.[17] As exhibited in
Scheme 4, C (sp2) H activation and insertion of Rh (III)
complex gave five-membered intermediate I, presumably
with the assistance of adjacent π system. Subsequently,
intermediate II formed via coordination with alkyne.
Then, Rh C bond was regioselectively inserted by alkyne
affording a seven-membered ring intermediate III.
Finally, reductive elimination process provided
product 3a.
with R1
=
substituted phenyls (both electron-
withdrawing and electron-donating). Substrate 2 with
R4 = phenyl was conducive to the yield presumably
facilitated by the assistance of conjugated π systems. It
is worth noting that cyano group led to a relatively
lower yield (3l), perhaps owing to the instability of
cyano group in the reaction condition. Next, substrates

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LIU ET AL.
SCHEME 2 Substrate scope. Reaction conditions: 1, 0.2 mmol; 2, 0.3 mmol; [Cp*RhCl2]2, 5 mol%; AgOAc 0.4 mmol, O2 (1 atm); DCE
(dichloroethane), 1.5 ml; 120ꢁC; 2 h. Isolated yields (for NMR spectra, see supporting information). aRatio of isomers (Major isomers are
shown; H NMR yields)

LIU ET AL.
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7.83 (ddd, J = 7.5, 1.5, 0.5 Hz, 1H), 7.63 (m, 1H),
7.51–7.44 (m, 1H), 7.44–7.37 (m, 3H), 3.43 (t,
J = 7.1 Hz, 2H), 2.62 (t, J = 7.1 Hz, 2H), 1.61 (m,
4H), 1.45–1.33 (m, 4H), 0.92 (td, J = 7.9, 0.8 Hz, 6H);
13C{1H} NMR (101 MHz, Chloroform-d) δ 143.5, 135.5,
133.2, 132.6, 132.1, 130.9, 129.4, 129.1, 129.0, 128.9,
128.3, 123.1, 123.0, 115.8, 30.2, 30.1, 29.8, 29.6, 22.2,
13.8; HRMS (ESI) m/z [M + H]+ calcd for C25H29N2
357.2325. Found: 357.2330.
SCHEME 3 Scaled-up experiment
4.1.2 | 4,5-Diethyl-1-phenylimidazo[1,5-a]
quinoline (3b)
1H NMR (400 MHz, Chloroform-d) δ 8.30–8.24 (m,
2H), 8.12–8.07 (m, 2H), 7.82 (ddd, J = 7.5, 1.5, 0.5 Hz,
1H), 7.68 (m, 1H), 7.50–7.45 (m, 1H), 7.45–7.37 (m,
3H), 3.37 (q, J = 8.0 Hz, 2H), 2.64–2.45 (m, 2H), 1.14
(dt, J = 9.0, 8.0 Hz, 6H); 13C{1H} NMR (101 MHz,
Chloroform-d) δ 144.3, 139.3, 136.2, 133.2, 132.8, 130.5,
129.2, 129.0, 128.9, 128.8, 128.6, 128.5, 123.3, 122.5,
115.9, 22.8, 22.7, 16.0, 15.7; HRMS (ESI) m/z
[M
301.1702.
+
H]+ calcd for C21H21N2 301.1699. Found:
4.1.3 | 4,5-Diisopropyl-1-phenylimidazo
[1,5-a]quinoline (3c)
1H NMR (400 MHz, Chloroform-d) δ 8.29–8.23 (m,
2H), 8.01 (ddd, J = 7.5, 1.5, 0.5 Hz, 1H), 7.94 (s, 1H),
7.78 (ddd, J = 7.5, 1.5, 0.5 Hz, 1H), 7.62 (m, 1H),
7.51–7.45 (m, 1H), 7.45–7.39 (m, 2H), 7.36 (td, J = 7.5,
1.5 Hz, 1H), 3.90 (m, 1H), 3.81 (m, 1H), 1.14 (dd,
J = 7.2, 6.8 Hz, 12H); 13C{1H} NMR (101 MHz,
Chloroform-d) δ 144.3, 137.6, 136.7, 134.4, 130.6, 129.9,
129.3, 128.9, 128.8, 128.7, 128.1, 127.3, 123.1, 122.9,
115.8, 30.5, 29.2, 22.5, 22.4; HRMS (ESI) m/z
SCHEME 4 Proposed mechanism
3 | CONCLUSIONS
To sum up, a homogeneous Rh catalytical system was put
forward for the synthesis of quinoline derivatives from
substituted imidazoles and alkynes. Combination of dou-
ble oxidants was crucial for the transformation. In the
mechanism, adjacent π systems might provide assistance
for realizing the activation of relatively unreactive C(5) H
of imidazole rings by forming five-membered metallacycle
intermediates. Moreover, the success of scaled-up experi-
ment provided more potential in the practical application.
[M
329.2009.
+
H]+ calcd for C23H25N2 329.2012. Found:
4.1.4 | 1,4,5-Triphenylimidazo[1,5-a]
quinoline (3d)
4 | EXPERIMENTAL
4.1 | NMR and HRMS characterization
of products
1H NMR (400 MHz, Chloroform-d) δ 8.21 (ddd, J = 7.4,
1.6, 0.8 Hz, 2H), 8.07 (s, 1H), 7.71 (m, 1H), 7.61 (td,
J = 7.5, 1.5 Hz, 1H), 7.59–7.38 (m, 15H); 13C{1H} NMR
(101 MHz, Chloroform-d) δ 141.1, 138.7, 136.6, 135.8,
135.4, 133.0, 131.5, 131.3, 130.8, 130.2, 129.6, 129.5, 128.7,
128.5, 128.2, 128.0, 127.9, 127.8, 125.1, 123.3, 122.6, 114.4;
HRMS (ESI) m/z [M + H]+ calcd for C29H21N2 397.1699.
Found: 397.1671.
4.1.1 | 4,5-Dibutyl-1-phenylimidazo[1,5-a]
quinoline (3a)
1H NMR (400 MHz, Chloroform-d) δ 8.27–8.21 (m,
2H), 8.09 (s, 1H), 8.01 (ddd, J = 7.5, 1.5, 0.5 Hz, 1H),

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LIU ET AL.
4.1.5 | 4,5-Dibutyl-7-methyl-
1-phenylimidazo[1,5-a]quinoline (3e)
(m, 4H), 1.45–1.33 (m, 4H), 0.92 (t, J = 8.0 Hz, 6H); 13C
{1H} NMR (101 MHz, Chloroform-d) δ 143.0, 135.4, 133.2,
131.2, 130.8, 130.7, 130.5, 129.8, 129.4, 129.1, 129.0, 128.9,
128.2, 125.9, 125.8, 124.7, 123.3, 123.2, 122.6, 116.8, 116.7,
30.9, 30.1, 29.8, 29.7, 22.2, 13.7; HRMS (ESI) m/z
[M + H]+ calcd for C26H28F3N2 425.2199. Found:
425.2221.
1H NMR (400 MHz, Chloroform-d) δ 8.25–8.19 (m, 2H),
8.11 (s, 1H), 7.77 (dt, J = 1.6, 0.6 Hz, 1H), 7.62 (dd,
J = 7.5, 0.5 Hz, 1H), 7.51–7.45 (m, 2H), 7.45–7.38 (m,
2H), 3.47 (t, J = 7.1 Hz, 2H), 2.61 (t, J = 7.1 Hz, 2H), 2.41
(t, J = 0.6 Hz, 3H), 1.67–1.57 (m, 4H), 1.45–1.33 (m, 4H),
0.92 (t, J = 8.0 Hz, 6H); 13C{1H} NMR (101 MHz,
Chloroform-d) δ 143.5, 134.7, 133.8, 132.9, 132.6, 132.2,
131.7, 130.8, 130.5, 129.6, 129.3, 128.7, 128.1, 123.0, 115.5,
30.1, 30.0, 29.9, 29.7, 22.2, 20.7, 13.7; HRMS (ESI) m/z
[M + H]+ calcd for C26H31N2 371.2481. Found: 371.2479.
4.1.9 | 4,5-Dibutyl-1-(p-tolyl)imidazo
[1,5-a]quinoline (3i)
1H NMR (400 MHz, Chloroform-d) δ 8.11 (s, 1H),
8.00–7.93 (m, 3H), 7.83 (m, 1H), 7.63 (td, J = 7.5, 1.5 Hz,
1H), 7.42 (td, J = 7.5, 1.5 Hz, 1H), 7.34 (m, 2H), 3.43 (t,
J = 7.1 Hz, 2H), 2.61 (t, J = 7.1 Hz, 2H), 2.43 (t,
J = 0.6 Hz, 3H), 1.67–1.57 (m, 4H), 1.45–1.33 (m, 4H),
0.92 (t, J = 8.0 Hz, 6H); 13C{1H} NMR (101 MHz,
Chloroform-d) δ 143.3, 140.0, 135.2, 133.6, 132.6, 131.8,
129.9, 129.4, 129.3, 128.9, 128.2, 128.0, 123.1, 123.0, 115.8,
30.1, 29.9, 29.7, 22.2, 21.2, 14.0; HRMS (ESI) m/z
[M + H]+ calcd for C26H31N2 371.2482. Found: 371.2450.
4.1.6 | 4,5-Dibutyl-7-ethyl-
1-phenylimidazo[1,5-a]quinoline (3f)
1H NMR (400 MHz, Chloroform-d) δ 8.22 (m, 2H), 8.10
(s, 1H), 7.66–7.60 (m, 2H), 7.50–7.44 (m, 1H), 7.44–7.38
(m, 2H), 7.35 (dd, J = 7.5, 1.5 Hz, 1H), 3.47 (t, J = 7.1 Hz,
2H), 2.73 (q, J = 8.0 Hz, 2H), 2.61 (t, J = 7.1 Hz, 2H),
1.67–1.57 (m, 4H), 1.45–1.33 (m, 4H), 1.23 (t, J = 8.0 Hz,
3H), 0.92 (td, J = 7.9, 0.6 Hz, 6H); 13C{1H} NMR
(101 MHz, Chloroform-d) δ 143.5, 143.2, 133.8, 133.7,
133.2, 131.8, 130.7, 129.8, 129.7, 129.4, 128.6, 128.3, 128.1,
123.0, 115.8, 30.1, 30.0, 29.7, 28.1, 22.2, 15.2, 13.9; HRMS
(ESI) m/z [M + H]+ calcd for C27H33N2 385.2638. Found:
385.2633.
4.1.10 | 4,5-Dibutyl-1-(4-methoxyphenyl)
imidazo[1,5-a]quinoline (3j)
1H NMR (400 MHz, Chloroform-d) δ 8.10 (s, 1H), 7.99
(m, 1H), 7.91–7.83 (m, 3H), 7.64 (td, J = 7.5, 1.5 Hz, 1H),
7.38 (td, J = 7.5, 1.5 Hz, 1H), 7.04–6.98 (m, 2H), 3.82 (s,
3H), 3.43 (t, J = 7.1 Hz, 2H), 2.61 (t, J = 7.1 Hz, 2H),
1.67–1.57 (m, 4H), 1.45–1.33 (m, 4H), 0.92 (t, J = 8.0 Hz,
6H); 13C{1H} NMR (101 MHz, Chloroform-d) δ 160.9,
143.2, 134.9, 133.6, 132.0, 129.9, 129.7, 129.6, 129.4, 128.9,
124.9, 123.1, 122.8, 115.8, 113.9, 55.3, 30.2, 30.1, 29.9,
29.7, 22.2, 13.5; HRMS (ESI) m/z [M + H]+ calcd for
C26H31N2O 387.2431. Found: 387.2430.
4.1.7 | 4,5-Dibutyl-7-methoxy-
1-phenylimidazo[1,5-a]quinoline (3g)
1H NMR (400 MHz, Chloroform-d) δ 8.24 (m, 2H), 8.10
(s, 1H), 7.81 (dd, J = 7.5, 0.5 Hz, 1H), 7.50–7.45 (m, 1H),
7.45–7.38 (m, 2H), 7.17 (dd, J = 1.5, 0.5 Hz, 1H), 6.98 (dd,
J = 7.5, 1.5 Hz, 1H), 3.85 (s, 3H), 3.47 (t, J = 7.1 Hz, 2H),
2.60 (t, J = 7.1 Hz, 2H), 1.67–1.56 (m, 4H), 1.45–1.33 (m,
4H), 0.92 (m, 6H); 13C{1H} NMR (101 MHz, Chloroform-
d) δ 155.2, 143.5, 133.2, 131.0, 130.8, 130.4, 130.1, 129.9,
129.8, 129.4, 128.6, 128.1, 116.6, 116.5, 108.9, 55.8, 30.3,
30.1, 30.0, 29.7, 22.2, 13.8; HRMS (ESI) m/z [M + H]+
calcd for C26H31N2O 371.2482. Found: 371.2488.
4.1.11 | 1-([1,1'-Biphenyl]-4-yl)-
4,5-dibutylimidazo[1,5-a]quinoline (3k)
1H NMR (400 MHz, Chloroform-d) δ 8.10 (s, 1H), 8.04
(m, 1H), 7.87 (m, 1H), 7.86–7.81 (m, 2H), 7.68 (td,
J = 7.5, 1.5 Hz, 1H), 7.62 (dd, J = 7.6, 1.4 Hz, 4H),
7.50–7.41 (m, 3H), 7.41–7.33 (m, 1H), 3.43 (t, J = 7.1 Hz,
2H), 2.70–2.54 (m, 2H), 1.67–1.58 (m, 4H), 1.45–1.33 (m,
4H), 0.92 (t, J = 8.0 Hz, 6H); 13C{1H} NMR (101 MHz,
Chloroform-d) δ 142.9, 141.3, 139.9, 134.6, 132.9, 131.4,
131.2, 129.4, 129.3, 129.2, 128.8, 128.8, 128.7, 128.0, 127.8,
127.3, 123.1, 122.8, 115.8, 30.1, 29.8, 29.7, 22.2, 13.9;
HRMS (ESI) m/z [M + H]+ calcd for C31H33N2 433.2638.
Found: 433.2640.
4.1.8 | 4,5-Dibutyl-1-phenyl-
7-(trifluoromethyl)imidazo[1,5-a]quinoline
(3h)
1H NMR (400 MHz, Chloroform-d) δ 8.25–8.19 (m, 2H),
8.16–8.09 (m, 2H), 7.91–7.82 (m, 2H), 7.50–7.38 (m, 3H),
3.47 (t, J = 7.1 Hz, 2H), 2.60 (t, J = 7.1 Hz, 2H), 1.67–1.57

LIU ET AL.
9 of 15
4.1.12 | 4,5-Dibutyl-1-(p-tolyl)imidazo
[1,5-a]quinoline-7-carbonitrile (3l)
7.50–7.43 (m, 3H), 7.41–7.33 (m, 1H), 3.47 (t, J = 7.1 Hz,
2H), 2.72–2.57 (m, 2H), 2.42 (t, J = 0.6 Hz, 3H), 1.67–1.58
(m, 4H), 1.45–1.33 (m, 4H), 0.92 (m, 6H); 13C{1H} NMR
(101 MHz, Chloroform-d) δ 143.1, 141.3, 140.1, 134.3,
133.3, 132.9, 132.5, 131.5, 131.1, 130.8, 129.3, 129.2, 128.9,
128.7, 127.8, 127.1, 122.8, 115.5, 30.0, 29.8, 29.6, 22.2,
20.8, 13.8; HRMS (ESI) m/z [M + H]+ calcd for C32H35N2
447.2795. Found: 447.2794.
1H NMR (400 MHz, Chloroform-d) δ 8.12 (s, 1H), 7.90
(dd, J = 7.5, 0.5 Hz, 1H), 7.89–7.84 (m, 3H), 7.81 (dd,
J = 7.5, 1.5 Hz, 1H), 7.35 (m, 2H), 3.47 (t, J = 7.1 Hz, 2H),
2.61 (t, J = 7.1 Hz, 2H), 2.42 (t, J = 0.6 Hz, 3H), 1.67–1.57
(m, 4H), 1.45–1.33 (m, 4H), 0.92 (t, J = 8.0 Hz, 6H); 13C
{1H} NMR (101 MHz, Chloroform-d) δ 143.0, 139.9, 135.1,
133.1, 133.0, 132.7, 131.4, 129.6, 129.4, 129.3, 128.2, 127.8,
126.6, 118.8, 116.9, 110.0, 30.7, 30.1, 30.0, 29.7, 22.2, 21.2,
13.7; HRMS (ESI) m/z [M + H]+ calcd for C27H30N3
396.2434. Found: 396.2431.
4.1.16 | 1-([1,1'-Biphenyl]-4-yl)-
4,5-dibutyl-7-methoxyimidazo[1,5-a]
quinoline (3p)
1H NMR (400 MHz, Chloroform-d) δ 8.10 (s, 1H),
7.91–7.85 (m, 2H), 7.75 (dd, J = 7.5, 0.5 Hz, 1H), 7.65–7.58
(m, 4H), 7.49–7.42 (m, 2H), 7.42–7.35 (m, 1H), 7.15 (dd,
J = 1.5, 0.5 Hz, 1H), 6.98 (dd, J = 7.5, 1.5 Hz, 1H), 3.83 (s,
3H), 3.47 (t, J = 7.1 Hz, 2H), 2.70–2.54 (m, 2H), 1.69–1.57
(m, 4H), 1.45–1.34 (m, 4H), 0.92 (t, J = 8.0 Hz, 6H); 13C
{1H} NMR (101 MHz, Chloroform-d) δ 155.3, 143.0, 141.5,
140.1, 133.2, 132.7, 131.1, 130.7, 130.5, 129.3, 129.0, 128.9,
128.7, 127.8, 127.7, 127.1, 116.6, 109.1, 55.7, 30.4, 30.0,
29.7, 29.6, 22.2, 13.6; HRMS (ESI) m/z [M + H]+ calcd for
C32H35N2O 463.2744. Found: 463.2747.
4.1.13 | 4,5-Dibutyl-7-methoxy-
1-(4-methoxyphenyl)imidazo[1,5-a]
quinoline (3m)
1H NMR (400 MHz, Chloroform-d) δ 8.11 (s, 1H),
7.92–7.86 (m, 2H), 7.77 (dd, J = 7.5, 0.5 Hz, 1H), 7.16 (dd,
J = 1.5, 0.5 Hz, 1H), 7.04–6.96 (m, 3H), 3.84 (d, J = 8.3 Hz,
6H), 3.47 (t, J = 7.1 Hz, 2H), 2.61 (t, J = 7.1 Hz, 2H),
1.67–1.56 (m, 4H), 1.45–1.33 (m, 4H), 0.92 (t, J = 8.0 Hz,
6H); 13C{1H} NMR (101 MHz, Chloroform-d) δ 161.2,
155.2, 143.0, 133.2, 131.4, 131.0, 130.5, 129.7, 129.4, 129.2,
125.0, 116.7, 116.6, 113.7, 109.0, 55.8, 55.3, 30.4, 30.1, 29.7,
29.6, 22.2, 13.5; HRMS (ESI) m/z [M + H]+ calcd for
C27H33N2O2 417.2536. Found: 417.2535.
4.1.17 | 4,5-Dibutyl-1-isopropylimidazo
[1,5-a]quinoline (3q)
1H NMR (400 MHz, Chloroform-d) δ 7.99 (s, 1H), 7.84
(m, 1H), 7.66 (td, J = 7.5, 1.5 Hz, 1H), 7.56 (m, 1H), 7.41
(td, J = 7.5, 1.6 Hz, 1H), 3.43 (t, J = 7.1 Hz, 2H), 3.24 (m,
1H), 2.62 (t, J = 7.1 Hz, 2H), 1.62 (p, J = 7.1 Hz, 4H),
1.45–1.33 (m, 10H), 0.92 (t, J = 8.0 Hz, 6H); 13C{1H} NMR
(101 MHz, Chloroform-d) δ 155.4, 135.8, 132.6, 132.0,
129.5, 128.9, 128.8, 127.8, 123.0, 122.6, 115.8, 30.4, 30.2,
29.9, 29.7, 27.4, 22.2, 20.5, 13.9; HRMS (ESI) m/z
[M + H]+ calcd for C22H31N2 323.2481. Found: 323.2479.
4.1.14 | 4,5-Dibutyl-1-(4-methoxyphenyl)-
7-(trifluoromethyl)imidazo[1,5-a]quinoline
(3n)
1H NMR (400 MHz, Chloroform-d) δ 8.21 (m, 1H), 8.15
(dd, J = 1.5, 0.5 Hz, 1H), 8.11 (s, 1H), 7.92–7.88 (m, 2H),
7.86 (dd, J = 7.5, 1.5 Hz, 1H), 7.08–7.02 (m, 2H), 3.83 (s,
3H), 3.47 (t, J = 7.1 Hz, 2H), 2.70–2.54 (m, 2H), 1.69–1.59
(m, 4H), 1.45–1.33 (m, 4H), 0.96–0.89 (m, 6H); 13C{1H}
NMR (101 MHz, Chloroform-d) δ 161.1, 142.8, 135.5,
133.1, 131.1, 130.5, 129.8, 129.3, 129.2, 126.3, 126.2, 125.2,
123.4, 123.3, 116.8, 116.7, 113.8, 55.3, 30.9, 30.0, 29.9,
29.6, 22.2, 14.0; HRMS (ESI) m/z [M + H]+ calcd for
C27H30F3N2O 455.2305. Found: 455.2300.
4.1.18 | 1-(4,5-Dibutylimidazo[1,5-a]
quinolin-1-yl)ethan-1-one (3r)
1H NMR (400 MHz, Chloroform-d) δ 8.52 (m, 1H), 8.22
(s, 1H), 7.81 (m, 1H), 7.67 (td, J = 7.5, 1.5 Hz, 1H), 7.43
(td, J = 7.5, 1.5 Hz, 1H), 3.43 (t, J = 7.1 Hz, 2H), 2.68 (s,
3H), 2.61 (t, J = 7.1 Hz, 2H), 1.67–1.58 (m, 4H), 1.45–1.33
(m, 4H), 0.92 (t, J = 8.0 Hz, 6H); 13C{1H} NMR (101 MHz,
Chloroform-d) δ 190.3, 146.2, 137.5, 132.9, 132.5, 131.8,
129.4, 129.1, 128.7, 123.0, 122.9, 117.1, 30.4, 30.2, 29.9,
29.7, 27.2, 22.2, 13.7; HRMS (ESI) m/z [M + H]+ calcd for
C21H27N2O 323.2118. Found: 323.2121.
4.1.15 | 1-([1,1'-Biphenyl]-4-yl)-
4,5-dibutyl-7-methylimidazo[1,5-a]
quinoline (3o)
1H NMR (400 MHz, Chloroform-d) δ 8.11 (s, 1H),
7.88–7.83 (m, 2H), 7.74 (m, 1H), 7.65–7.56 (m, 5H),

10 of 15
LIU ET AL.
4.1.19 | 4,5-Dibutylimidazo[1,5-a]
quinoline-1-carbonitrile (3s)
HRMS (ESI) m/z [M + H]+ calcd for C21H29N2O
325.2274. Found: 325.2271.
1H NMR (400 MHz, Chloroform-d) δ 8.52 (m, 1H),
7.87–7.81 (m, 2H), 7.70 (td, J = 7.5, 1.5 Hz, 1H), 7.31 (td,
J = 7.5, 1.5 Hz, 1H), 3.43 (t, J = 7.1 Hz, 2H), 2.59 (t,
J = 7.1 Hz, 2H), 1.67–1.55 (m, 4H), 1.44–1.33 (m, 4H),
0.92 (td, J = 7.9, 0.6 Hz, 6H); 13C{1H} NMR (101 MHz,
Chloroform-d) δ 136.3, 133.4, 132.1, 131.5, 130.6, 129.6,
128.6, 123.2, 122.3, 118.3, 114.9, 112.0, 30.4, 30.2, 30.0,
29.7, 22.2, 13.8; HRMS (ESI) m/z [M + H]+ calcd for
C20H24N3 306.1965. Found: 306.1966.
4.1.23 | 4,5-Dibutyl-1-(ethylthio)imidazo
[1,5-a]quinoline (3w)
1H NMR (400 MHz, Chloroform-d) δ 8.06 (s, 1H), 7.88
(m, 1H), 7.68 (m, 1H), 7.56 (m, 1H), 7.39 (td, J = 7.5,
1.5 Hz, 1H), 3.43 (t, J = 7.1 Hz, 2H), 3.06 (q, J = 8.0 Hz,
2H), 2.62 (t, J = 7.1 Hz, 2H), 1.67–1.57 (m, 4H), 1.45–1.38
(m, 3H), 1.38–1.33 (m, 4H), 0.92 (t, J = 8.0 Hz, 6H); 13C
{1H} NMR (101 MHz, Chloroform-d) δ 151.4, 135.7, 132.7,
132.0, 131.3, 129.7, 128.7, 123.9, 123.0, 121.7, 116.6, 30.3,
30.2, 30.0, 29.7, 26.5, 22.2, 14.3, 13.8; HRMS (ESI) m/z
[M + H]+ calcd for C21H29N2S 341.2046. Found:
341.2044.
4.1.20 | 4,5-Dibutyl-1-chloroimidazo
[1,5-a]quinoline (3t)
1H NMR (400 MHz, Chloroform-d) δ 7.85–7.79 (m, 2H),
7.69 (td, J = 7.5, 1.5 Hz, 1H), 7.57 (m, 1H), 7.31 (m, 1H),
3.43 (t, J = 7.1 Hz, 2H), 2.60 (t, J = 7.1 Hz, 2H), 1.67–1.57
(m, 4H), 1.44–1.33 (m, 4H), 0.92 (td, J = 7.9, 0.6 Hz, 6H);
13C{1H} NMR (101 MHz, Chloroform-d) δ 135.9, 133.3,
132.6, 131.3, 130.2, 129.8, 129.3, 127.0, 123.4, 122.1, 119.7,
30.4, 30.2, 29.9, 29.7, 22.2, 14.0; HRMS (ESI) m/z
[M + H]+ calcd for C19H24ClN2 316.1701. Found:
316.1699.
4.1.24 | (4,5-Dibutylimidazo[1,5-a]
quinolin-1-yl)(phenyl)methanone (3x)
1H NMR (400 MHz, Chloroform-d) δ 8.52 (m, 1H), 8.24
(s, 1H), 8.02–7.96 (m, 2H), 7.82 (m, 1H), 7.62–7.55 (m,
2H), 7.54–7.47 (m, 2H), 7.39 (td, J = 7.5, 1.5 Hz, 1H), 3.43
(t, J = 7.1 Hz, 2H), 2.60 (t, J = 7.1 Hz, 2H), 1.62 (p,
J = 7.1 Hz, 4H), 1.45–1.33 (m, 4H), 0.92 (td, J = 7.9,
0.6 Hz, 6H); 13C{1H} NMR (101 MHz, Chloroform-d) δ
187.2, 143.0, 136.0, 134.4, 132.9, 132.6, 131.9, 131.6, 130.3,
130.0, 129.4, 128.9, 128.4, 123.1, 122.9, 117.5, 30.1, 30.0,
29.8, 29.7, 22.2, 13.9; HRMS (ESI) m/z [M + H]+ calcd for
C26H29N2O 385.2274. Found: 385.2269.
4.1.21 | 4,5-Dibutyl-1-ethylimidazo[1,5-a]
quinoline (3u)
1H NMR (400 MHz, Chloroform-d) δ 7.89 (s, 1H), 7.85
(m, 1H), 7.70 (td, J = 7.5, 1.5 Hz, 1H), 7.55 (m, 1H), 7.37
(td, J = 7.5, 1.5 Hz, 1H), 3.43 (t, J = 7.1 Hz, 2H), 2.93 (q,
J = 8.0 Hz, 2H), 2.61 (t, J = 7.1 Hz, 2H), 1.67–1.58 (m,
4H), 1.45–1.37 (m, 3H), 1.35 (t, J = 8.0 Hz, 4H), 0.92 (td,
J = 7.9, 0.6 Hz, 6H); 13C{1H} NMR (101 MHz,
Chloroform-d) δ 150.2, 134.8, 132.9, 131.8, 129.1, 128.7,
127.6, 126.7, 123.3, 122.4, 115.8, 30.4, 30.2, 30.1, 29.7,
22.8, 22.2, 13.7, 11.0; HRMS (ESI) m/z [M + H]+ calcd for
C21H29N2 309.2325. Found: 309.2321.
4.1.25 | 4,5-Diisopropylimidazo[1,5-a]
quinoline-1-carbonitrile (3y)
1H NMR (400 MHz, Chloroform-d) δ 8.48 (m, 1H), 7.79
(ddd, J = 7.5, 1.5, 0.5 Hz, 1H), 7.66 (td, J = 7.5, 1.5 Hz,
1H), 7.57 (s, 1H), 7.36 (td, J = 7.5, 1.5 Hz, 1H), 3.80 (m,
1H), 3.12 (m, 1H), 1.14 (dd, J = 6.8, 2.2 Hz, 12H); 13C{1H}
NMR (101 MHz, Chloroform-d) δ 137.1, 136.9, 135.1,
130.3, 129.1, 128.8, 127.7, 123.2, 123.1, 118.2, 115.1, 112.0,
30.4, 29.8, 22.5, 22.4; HRMS (ESI) m/z [M + H]+ calcd for
C18H20N3 278.1651. Found: 278.1645.
4.1.22 | 4,5-Dibutyl-1-ethoxyimidazo
[1,5-a]quinoline (3v)
1H NMR (400 MHz, Chloroform-d) δ 7.91 (s, 1H), 7.82
(m, 1H), 7.75 (td, J = 7.5, 1.5 Hz, 1H), 7.57 (m, 1H), 7.36
(m, 1H), 4.25 (q, J = 8.0 Hz, 2H), 3.43 (t, J = 7.1 Hz, 2H),
2.74–2.58 (m, 2H), 1.61 (m, 4H), 1.45–1.33 (m, 7H), 0.92
(t, J = 8.0 Hz, 6H); 13C{1H} NMR (101 MHz, Chloroform-
d) δ 156.0, 135.0, 133.2, 131.5, 129.5, 128.5, 123.7, 123.6,
122.9, 122.6, 115.8, 64.6, 30.4, 30.2, 29.7, 22.2, 14.6, 13.6;
4.1.26 | 1-Ethoxy-4,5-diisopropylimidazo
[1,5-a]quinoline (3z)
1H NMR (400 MHz, Chloroform-d) δ 7.99 (m, 1H), 7.78
(s, 1H), 7.69 (td, J = 7.5, 1.5 Hz, 1H), 7.58 (m, 1H), 7.34
(td, J = 7.5, 1.5 Hz, 1H), 4.25 (q, J = 8.0 Hz, 2H), 3.37 (m,

LIU ET AL.
11 of 15
1H), 3.11 (m, 1H), 1.37 (t, J = 8.0 Hz, 3H), 1.15 (dd,
J = 9.7, 6.8 Hz, 12H); 13C{1H} NMR (101 MHz,
Chloroform-d) δ 156.2, 137.2, 135.5, 133.4, 129.1, 128.0,
123.4, 123.2, 122.6, 121.1, 115.8, 65.0, 30.2, 29.1, 22.5,
22.4, 14.6; HRMS (ESI) m/z [M + H]+ calcd for
C19H25N2O 297.1961. Found: 297.1958.
11H), 7.44–7.36 (m, 2H), 2.63 (s, 3H); 13C{1H} NMR
(101 MHz, Chloroform-d) δ 190.5, 142.5, 138.3, 138.2,
136.7, 135.7, 134.0, 132.3, 131.2, 130.3, 129.5, 128.1, 128.0,
127.7, 127.5, 127.4, 126.5, 126.1, 123.1, 115.4, 27.2; HRMS
(ESI) m/z [M + H]+ calcd for C25H19N2O 363.1492.
Found: 363.1488.
4.1.27 | (4,5-Diisopropylimidazo[1,5-a]
quinolin-1-yl)(phenyl)methanone (3aa)
4.1.31 | 4,5-Diphenylimidazo[1,5-a]
quinoline-1-carbonitrile (3ae)
1H NMR (400 MHz, Chloroform-d) δ 8.48 (m, 1H), 8.10 (s,
1H), 8.02–7.96 (m, 2H), 7.80 (ddd, J = 7.5, 1.5, 0.5 Hz, 1H),
7.66–7.56 (m, 2H), 7.54–7.47 (m, 2H), 7.40 (td, J = 7.5,
1.5 Hz, 1H), 3.91 (hept, J = 6.8 Hz, 1H), 3.36 (m, 1H), 1.15
(dd, J = 10.1, 6.8 Hz, 12H); 13C{1H} NMR (101 MHz,
Chloroform-d) δ 187.3, 143.1, 137.4, 137.0, 134.4, 134.2,
132.6, 131.1, 129.7, 129.6, 129.1, 128.7, 124.0, 123.1, 117.4,
30.3, 28.7, 22.5, 22.4; HRMS (ESI) m/z [M + H]+ calcd for
C24H25N2O 357.1961. Found: 357.1966.
1H NMR (400 MHz, Chloroform-d) δ 8.70 (m, 1H), 7.73
(s, 1H), 7.73–7.65 (m, 2H), 7.58–7.37 (m, 11H); 13C{1H}
NMR (101 MHz, Chloroform-d) δ 138.6, 136.4, 135.9,
135.2, 134.4, 133.3, 131.1, 129.6, 129.5, 128.2, 128.1, 127.7,
127.6, 127.3, 125.2, 124.5, 123.5, 116.6, 112.2, 111.2;
HRMS (ESI) m/z [M + H]+ calcd for C26H16N3 370.1339.
Found: 370.1342.
4.1.32 | 1-Chloro-4,5-diphenylimidazo
[1,5-a]quinoline (3af)
4.1.28 | 1,4,5-Triisopropylimidazo[1,5-a]
quinoline (3ab)
1H NMR (400 MHz, Chloroform-d) δ 7.70 (s, 1H),
7.69–7.63 (m, 2H), 7.62–7.54 (m, 3H), 7.54–7.45 (m, 7H),
7.45–7.38 (m, 2H); 13C{1H} NMR (101 MHz, Chloroform-
d) δ 138.6, 136.5, 135.6, 135.4, 133.0, 131.0, 130.0, 129.7,
129.6, 128.2, 128.0, 127.8, 127.6, 127.3, 126.7, 124.4, 123.2,
122.6, 118.0; HRMS (ESI) m/z [M + H]+ calcd for
C23H16ClN2 355.0996. Found: 355.0990.
1H NMR (400 MHz, Chloroform-d) δ 8.01 (m, 1H), 7.96
(ddd, J = 7.5, 1.5, 0.5 Hz, 1H), 7.84 (s, 1H), 7.68 (td,
J = 7.5, 1.5 Hz, 1H), 7.38 (td, J = 7.5, 1.5 Hz, 1H), 3.91
(m, 1H), 3.81 (dq, J = 13.6, 6.8 Hz, 1H), 3.24 (m, 1H),
1.37 (d, J = 6.8 Hz, 6H), 1.14 (dd, J = 6.8, 0.9 Hz, 12H);
13C{1H} NMR (101 MHz, Chloroform-d) δ 155.4, 137.4,
135.5, 133.7, 129.4, 129.1, 128.5, 125.8, 123.3, 122.4, 115.8,
30.2, 28.5, 27.8, 22.5, 22.4, 20.5; HRMS (ESI) m/z
[M + H]+ calcd for C20H27N2 295.2168. Found: 295.2165.
4.1.33 | 1-Ethyl-4,5-diphenylimidazo
[1,5-a]quinoline (3ag)
1H NMR (400 MHz, Chloroform-d) δ 7.84 (s, 1H),
7.71–7.64 (m, 1H), 7.64–7.37 (m, 13H), 2.92 (q,
J = 8.0 Hz, 2H), 1.35 (t, J = 8.0 Hz, 3H); 13C{1H} NMR
(101 MHz, Chloroform-d) δ 146.1, 138.5, 136.4, 134.9,
134.7, 131.5, 131.1, 130.8, 129.6, 129.3, 128.2, 128.1, 127.7,
127.6, 126.7, 125.9, 124.4, 123.3, 114.3, 23.1, 11.0; HRMS
(ESI) m/z [M + H]+ calcd for C25H21N2 349.1699, found
349.1674.
4.1.29 | 1-Isopropyl-4,5-diphenylimidazo
[1,5-a]quinoline (3ac)
1H NMR (400 MHz, Chloroform-d) δ 7.98 (s, 1H),
7.73–7.66 (m, 1H), 7.65–7.36 (m, 13H), 3.23 (m, 1H), 1.38
(d, J = 6.8 Hz, 6H); 13C{1H} NMR (101 MHz, Chloroform-
d) δ 150.3, 138.2, 136.7, 135.6, 134.6, 133.3, 132.3, 131.2,
130.1, 129.5, 128.1, 128.0, 127.6, 127.5, 127.4, 126.7, 125.2,
123.1, 114.3, 27.7, 20.5; HRMS (ESI) m/z [M + H]+ calcd
for C26H23N2 363.1856. Found: 363.1860.
4.1.34 | 1-Ethoxy-4,5-diphenylimidazo
[1,5-a]quinoline (3ah)
4.1.30 | 1-(4,5-Diphenylimidazo[1,5-a]
quinolin-1-yl)ethan-1-one (3ad)
1H NMR (400 MHz, Chloroform-d) δ 7.93 (s, 1H),
7.71–7.63 (m, 2H), 7.59–7.54 (m, 2H), 7.54–7.39 (m, 10H),
4.25 (q, J = 8.0 Hz, 2H), 1.39 (t, J = 8.0 Hz, 3H); 13C{1H}
NMR (101 MHz, Chloroform-d) δ 163.1, 137.1, 136.7,
135.6, 134.6, 132.4, 131.2, 130.0, 129.9, 128.1, 128.0, 127.5,
1H NMR (400 MHz, Chloroform-d) δ 8.70 (m, 1H), 8.20
(s, 1H), 7.72 (ddd, J = 7.3, 1.7, 0.5 Hz, 1H), 7.62–7.44 (m,

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127.4, 127.3, 124.6, 123.0, 122.7, 114.1, 64.6, 14.6; HRMS
(ESI) m/z [M + H]+ calcd for C25H21N2O 365.1648.
Found: 365.1651.
NMR (101 MHz, Chloroform-d) δ 152.8, 137.7, 134.6,
130.9, 130.6, 129.6, 128.0, 123.0, 122.7, 119.8, 115.0, 64.5,
30.2, 30.0, 29.7, 29.2, 22.2, 14.7, 14.6, 13.6; HRMS (ESI)
m/z [M + H]+ calcd for C22H31N2O 339.2431. Found:
339.2434.
4.1.35 | 1-(Ethylthio)-
4,5-diphenylimidazo[1,5-a]quinoline (3ai)
4.1.39 | 3-Methyl-4,5-diphenylimidazo
[1,5-a]quinoline-1-carbonitrile (3am)
1H NMR (400 MHz, Chloroform-d) δ 8.05 (s, 1H), 7.71
(m, 1H), 7.68–7.62 (m, 1H), 7.58–7.37 (m, 12H), 3.06 (q,
J = 8.0 Hz, 2H), 1.35 (t, J = 8.0 Hz, 3H); 13C{1H} NMR
(101 MHz, Chloroform-d) δ 149.8, 138.0, 136.6, 135.8,
135.7, 131.8, 131.3, 131.1, 129.9, 129.5, 128.1, 128.0, 127.9,
127.4, 127.3, 126.5, 126.1, 122.9, 114.9, 26.5, 14.3; HRMS
(ESI) m/z [M + H]+ calcd for C25H21N2S 381.1420.
Found: 381.1423.
1H NMR (400 MHz, Chloroform-d) δ 8.70 (m, 1H), 7.71
(m, 1H), 7.64 (td, J = 7.5, 1.5 Hz, 1H), 7.59–7.48 (m, 7H),
7.48–7.38 (m, 4H), 2.79 (s, 3H); 13C{1H} NMR (101 MHz,
Chloroform-d) δ 144.6, 136.5, 136.2, 135.5, 134.8, 134.5,
133.6, 131.2, 130.3, 128.9, 128.2, 128.1, 127.8, 127.6, 127.5,
125.8, 123.2, 117.2, 111.6, 111.0, 14.8; HRMS (ESI) m/z
[M + H]+ calcd for C25H18N3 360.1495. Found: 360.1499.
4.1.36 | (4,5-Diphenylimidazo[1,5-a]
quinolin-1-yl)(phenyl)methanone (3aj)
4.1.40 | 1-Ethoxy-3-methyl-
4,5-diphenylimidazo[1,5-a]quinoline (3an)
1H NMR (400 MHz, Chloroform-d) δ 8.70 (m, 1H), 8.23
(s, 1H), 8.01–7.95 (m, 2H), 7.74 (ddd, J = 7.5, 1.5, 0.5 Hz,
1H), 7.66–7.36 (m, 15H); 13C{1H} NMR (101 MHz,
Chloroform-d) δ 187.2, 139.3, 139.2, 136.5, 136.1, 135.8,
134.2, 133.3, 132.7, 131.7, 131.2, 130.3, 129.8, 129.7, 129.0,
128.6, 128.3, 128.2, 128.1, 127.9, 126.2, 125.0, 123.3, 115.8;
HRMS (ESI) m/z [M + H]+ calcd for C30H21N2O
425.1648. Found: 425.1644.
1H NMR (400 MHz, Chloroform-d) δ 7.76–7.67 (m, 2H),
7.59–7.55 (m, 2H), 7.53–7.39 (m, 10H), 4.26 (q,
J = 8.0 Hz, 2H), 2.78 (s, 3H), 1.38 (t, J = 8.0 Hz, 3H); 13C
{1H} NMR (101 MHz, Chloroform-d) δ 148.8, 142.4, 136.4,
136.2, 135.0, 134.9, 134.6, 131.3, 129.9, 129.1, 128.1, 127.8,
127.5, 127.4, 124.1, 123.1, 115.0, 113.8, 64.4, 14.8, 14.6;
HRMS (ESI) m/z [M + H]+ calcd for C26H23N2O
379.1805. Found: 379.1808.
4.1.37 | 4,5-Dibutyl-1-isopropyl-
3-methylimidazo[1,5-a]quinoline (3ak)
4.1.41 | 1-Phenyl-4,5-di (pyridin-4-yl)
imidazo[1,5-a]quinoline (3ao)
1H NMR (400 MHz, Chloroform-d) δ 7.82 (m, 1H), 7.69
(td, J = 7.5, 1.5 Hz, 1H), 7.57 (m, 1H), 7.40 (td, J = 7.5,
1.5 Hz, 1H), 3.47 (t, J = 7.1 Hz, 2H), 3.24 (m, 1H),
2.69–2.61 (m, 5H), 1.67–1.57 (m, 4H), 1.45–1.33 (m, 10H),
0.96–0.89 (m, 6H); 13C{1H} NMR (101 MHz, Chloroform-
d) δ 156.9, 138.2, 135.9, 131.0, 130.6, 129.1, 128.8, 124.3,
123.2, 122.4, 115.4, 30.2, 30.0, 29.7, 29.5, 29.4, 22.2, 20.5,
15.4, 13.8; HRMS (ESI) m/z [M + H]+ calcd for C23H33N2
337.2638. Found: 337.2633.
1H NMR (400 MHz, Chloroform-d) δ 8.69–8.63 (m, 4H),
8.24–8.18 (m, 2H), 8.09 (s, 1H), 7.72 (m, 1H), 7.65–7.60
(m, 2H), 7.60–7.55 (m, 2H), 7.52 (td, J = 7.4, 1.5 Hz, 1H),
7.50–7.45 (m, 2H), 7.44–7.35 (m, 3H); 13C{1H} NMR
(101 MHz, Chloroform-d) δ 148.3, 141.3, 141.1, 139.9,
135.5, 134.1, 131.6, 130.9, 130.3, 129.6, 128.8, 128.3, 125.6,
124.5, 123.4, 122.5, 114.4; HRMS (ESI) m/z [M + H]+
calcd for C27H19N4 399.1604. Found: 399.1599.
4.1.38 | 4,5-Dibutyl-1-ethoxy-
3-methylimidazo[1,5-a]quinoline (3al)
4.1.42 | 1-Phenyl-4,5-di (pyridin-2-yl)
imidazo[1,5-a]quinoline (3ap)
1H NMR (400 MHz, Chloroform-d) δ 7.82 (m, 1H), 7.70
(td, J = 7.5, 1.5 Hz, 1H), 7.56 (m, 1H), 7.36 (td, J = 7.5,
1.5 Hz, 1H), 4.26 (q, J = 8.0 Hz, 2H), 3.47 (t, J = 7.1 Hz,
2H), 2.70 (s, 3H), 2.65 (t, J = 7.1 Hz, 2H), 1.68–1.57 (m,
4H), 1.45–1.33 (m, 7H), 0.92 (t, J = 8.0 Hz, 6H); 13C{1H}
1H NMR (400 MHz, Chloroform-d) δ 8.80 (dd, J = 7.5,
1.5 Hz, 1H), 8.76–8.70 (m, 1H), 8.60 (m, 1H), 8.43 (s, 1H),
8.25–8.19 (m, 2H), 7.92 (td, J = 7.5, 1.5 Hz, 1H), 7.85–7.77
(m, 3H), 7.75 (m, 1H), 7.71 (td, J = 7.4, 1.4 Hz, 1H),
7.51–7.35 (m, 6H); 13C{1H} NMR (101 MHz, Chloroform-

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d) δ 154.7, 152.7, 148.9, 141.4, 136.4, 134.0, 133.5, 132.5,
130.9, 128.8, 127.2, 126.0, 125.7, 124.4, 122.7, 115.3;
HRMS (ESI) m/z [M + H]+ calcd for C27H19N4 399.1604.
Found: 399.1599.
128.1, 125.3, 123.3, 114.5, 113.2, 55.3; HRMS (ESI) m/z
[M + H]+ calcd for C31H25N2O2 457.1911. Found:
457.1913.
4.1.47 | 4,5-Bis(4-nitrophenyl)-
1-phenylimidazo[1,5-a]quinoline (3au)
4.1.43 | 4,5-Di (furan-2-yl)-
1-phenylimidazo[1,5-a]quinoline (3aq)
1H NMR (400 MHz, Chloroform-d) δ 8.25–8.16 (m, 6H),
8.07 (s, 1H), 7.85–7.81 (m, 2H), 7.81–7.75 (m, 2H),
7.71–7.63 (m, 2H), 7.50 (m, 1H), 7.49–7.40 (m, 4H); 13C
{1H} NMR (101 MHz, Chloroform-d) δ 148.6, 141.2, 140.9,
138.2, 134.9, 132.8, 130.9, 129.9, 128.9, 127.9, 125.4, 123.1,
114.4; HRMS (ESI) m/z [M + H]+ calcd for C29H19N4O4
487.1401. Found: 487.1403.
1H NMR (400 MHz, Chloroform-d) δ 8.25–8.19 (m, 2H),
8.01 (s, 1H), 7.66–7.58 (m, 3H), 7.55 (ddd, J = 7.4, 1.5,
0.6 Hz, 1H), 7.51–7.41 (m, 3H), 7.41–7.33 (m, 2H), 7.17
(dd, J = 7.5, 1.5 Hz, 1H), 6.98 (dd, J = 7.5, 1.5 Hz, 1H),
6.62 (td, J = 7.5, 1.1 Hz, 2H); 13C{1H} NMR (101 MHz,
Chloroform-d) δ 146.0, 145.2, 143.4, 141.4, 135.5, 130.9,
128.7, 126.9, 124.4, 123.2, 122.1, 115.0, 114.6, 112.8, 110.4;
HRMS (ESI) m/z [M + H]+ calcd for C25H17N2O2
377.1285. Found: 377.1291.
4.1.48 | 4,40-(1-Phenylimidazo[1,5-a]
quinoline-4,5-diyl)dibenzonitrile (3av)
1H NMR (400 MHz, Chloroform-d) δ 8.16 (m, 2H), 8.06
(s, 1H), 7.77–7.73 (m, 2H), 7.73–7.67 (m, 6H), 7.66–7.63
(m, 2H), 7.54–7.39 (m, 5H); 13C{1H} NMR (101 MHz,
Chloroform-d) δ 140.9, 138.9, 137.2, 134.9, 132.7, 131.9,
130.7, 128.8, 127.5, 125.2, 123.3, 118.5, 114.5, 112.3;
HRMS (ESI) m/z [M + H]+ calcd for C31H19N4 447.1604.
Found: 447.1599.
4.1.44 | 1-Phenyl-4,5-di (thiophen-3-yl)
imidazo[1,5-a]quinoline (3ar)
1H NMR (400 MHz, Chloroform-d) δ 8.59 (m, 1H), 8.18
(m, 2H), 8.03 (s, 1H), 7.65 (ddd, J = 7.5, 1.5, 0.5 Hz, 1H),
7.55–7.36 (m, 9H), 7.27 (m, 2H); 13C{1H} NMR (101 MHz,
Chloroform-d) δ 141.1, 139.0, 137.0, 134.5, 132.0, 131.6,
131.1, 130.0, 129.3, 128.8, 127.9, 126.9, 126.2, 125.9, 123.4,
121.6, 118.6, 114.8; HRMS (ESI) m/z [M + H]+ calcd for
C25H17N2S2 409.0828. Found: 409.0832.
4.1.49 | 1-Phenyl-4,5-bis
(4-(trifluoromethyl)phenyl)imidazo[1,5-a]
quinoline (3aw)
1H NMR (400 MHz, Chloroform-d) δ 8.16 (m, 2H), 8.07
(s, 1H), 7.76–7.70 (m, 4H), 7.70–7.63 (m, 2H), 7.54–7.38
(m, 9H); 13C{1H} NMR (101 MHz, Chloroform-d) δ 140.9,
138.4, 136.8, 135.6, 132.7, 131.4, 130.2, 128.9, 128.3, 127.6,
125.7, 124.0, 123.1, 114.5; HRMS (ESI) m/z [M + H]+
calcd for C31H19N2F6 533.1447. Found: 533.1451.
4.1.45 | 4,40-(1-Phenylimidazo[1,5-a]
quinoline-4,5-diyl)bis(N,N-dimethylaniline)
(3as)
1H NMR (400 MHz, Chloroform-d) δ 8.25–8.19 (m, 2H),
8.07 (s, 1H), 7.71 (ddd, J = 7.5, 1.5, 0.5 Hz, 1H), 7.67 (td,
J = 7.5, 1.5 Hz, 1H), 7.60–7.54 (m, 2H), 7.53–7.46 (m, 4H),
7.46–7.42 (m, 3H), 6.89–6.81 (m, 4H), 3.00 (d, J = 4.6 Hz,
12H); 13C{1H} NMR (101 MHz, Chloroform-d) δ 152.0,
140.9, 138.2, 135.0, 132.7, 131.4, 130.3, 128.9, 128.1, 126.2,
125.2, 123.3, 114.4, 111.0, 40.3; HRMS (ESI) m/z
[M + H]+ calcd for C33H31N4 483.2543. Found: 483.2540.
4.1.50 | 5-Butyl-1,4-diphenylimidazo
[1,5-a]quinoline (3ax) or 4-butyl-
1,5-diphenylimidazo[1,5-a]quinoline (3ax')
HRMS (ESI) m/z [M + H]+ calcd for C27H25N2 377.2012.
Found: 377.2015.
4.1.46 | 4,5-Bis(4-methoxyphenyl)-
1-phenylimidazo[1,5-a]quinoline (3at)
4.1.51 | 5-Isopropyl-1,4-diphenylimidazo
[1,5-a]quinoline (3ay) or 4-isopropyl-
1,5-diphenylimidazo[1,5-a]quinoline (3ay')
1H NMR (400 MHz, Chloroform-d) δ 8.13–8.04 (m, 3H),
7.73–7.64 (m, 2H), 7.53–7.37 (m, 9H), 6.94–6.87 (m, 4H),
3.82 (d, J = 2.0 Hz, 6H); 13C{1H} NMR (101 MHz,
Chloroform-d) δ 159.4, 140.9, 135.0, 132.9, 130.3, 128.9,
HRMS (ESI) m/z [M + H]+ calcd for C26H23N2 363.1856.
Found: 363.1858.

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LIU ET AL.
4.1.52 | 5-Butyl-1-phenyl-4-(pyridin-4-yl)
imidazo[1,5-a]quinoline (3az) or 4-butyl-
1-phenyl-5-(pyridin-4-yl)imidazo[1,5-a]
quinoline (3az')
methodology; project administration; resources; software;
supervision; validation; visualization. Zhenzhong Yan:
Conceptualization; data curation; formal analysis;
funding acquisition; investigation; methodology; project
administration;
resources;
software;
supervision.
HRMS (ESI) m/z [M + H]+ calcd for C26H24N3 378.1965.
Found: 378.1968.
Tiancheng Mu: Conceptualization; data curation; for-
mal analysis; funding acquisition; investigation; method-
ology; project administration; resources; software;
supervision; validation; visualization.
4.1.53 | 5-Butyl-1-phenyl-4-(pyridin-3-yl)
imidazo[1,5-a]quinoline (3ba) or 4-butyl-
1-phenyl-5-(pyridin-3-yl)imidazo[1,5-a]
quinoline (3ba')
ORCID
Zhenghui Liu https://orcid.org/0000-0003-0559-4517
Shien Guo https://orcid.org/0000-0001-7928-0022
Peng Wang https://orcid.org/0000-0003-0444-2247
Zhenzhong Yan https://orcid.org/0000-0002-0070-9082
Tiancheng Mu https://orcid.org/0000-0001-8931-6113
HRMS (ESI) m/z [M + H]+ calcd for C26H24N3 378.1965.
Found: 378.1962.
4.1.54 | 5-Butyl-4-(3-methoxyphenyl)-
1-phenylimidazo[1,5-a]quinoline (3bb) or
4-butyl-5-(3-methoxyphenyl)-
REFERENCES
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1-phenylimidazo[1,5-a]quinoline (3bb')
HRMS (ESI) m/z [M + H]+ calcd for C28H27N2O
407.2118. Found: 407.2122.
4.1.55 | 5-Butyl-4-(furan-2-yl)-
1-phenylimidazo[1,5-a]quinoline (3bc) or
4-butyl-5-(furan-2-yl)-1-phenylimidazo
[1,5-a]quinoline (3bc')
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HRMS (ESI) m/z [M + H]+ calcd for C25H23N2O
367.1805. Found: 367.1799.
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ACKNOWLEDGMENTS
This work was supported by the National Natural Science
Foundation of China (21773307) and Zhejiang Province
Public Welfare Technology Application Research Project
(LGG19B060002).
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CONFLICT OF INTEREST
There are no conflicts to declare.
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J. Phys. Org. Chem. 2014, 27, 589.
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Zhenghui Liu: Conceptualization; data curation; formal
analysis; funding acquisition; investigation; methodology;
project administration; resources; software; supervision;
validation; visualization. Shien Guo: Conceptualization;
data curation; formal analysis; investigation; methodol-
ogy; project administration; resources; supervision; vali-
dation; visualization. Peng Wang: Conceptualization;
data
curation;
formal
analysis;
investigation;

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SUPPORTING INFORMATION
Additional supporting information may be found online
in the Supporting Information section at the end of this
article.
How to cite this article: Liu Z, Guo S, Wang P,
Yan Z, Mu T. Oxidative annulations via double
C H bond cleavages: Approach to quinoline
derivatives. Appl Organomet Chem. 2021;35:e6156.
https://doi.org/10.1002/aoc.6156