Ruthenium-catalyzed acceptorless dehydrogenative coupling of o-aminobenzyl alcohols with ketones to quinolines in the presence of carbonate salt

Article abstract of DOI:10.1016/j.jcat.2020.12.016

A ruthenium complex bearing a functional 2,2′-bibenzimidazole ligand [(p-cymene)Ru(BiBzImH₂)Cl][Cl] was designed, synthesized and found to be a general and highly efficient catalyst for the synthesis of quinolines via acceptorless dehydrogenative coupling of o-aminobenzyl alcohols with ketones in the presence of carbonate salt. It was confirmed that NH units in the ligand are crucial for catalytic activity. The application of this catalytic system for the scale-gram synthesis of biologically active molecular was also undertaken. Notably, this research exhibits new potential of metal–ligand bifuctional catalysts for acceptorless dehydrogenative reactions.

Full text of DOI:10.1016/j.jcat.2020.12.016

Journal of Catalysis 395 (2021) 340–349
Contents lists available at ScienceDirect
Journal of Catalysis
journal homepage: www.elsevier.com/locate/jcat
Ruthenium-catalyzed acceptorless dehydrogenative coupling
of o-aminobenzyl alcohols with ketones to quinolines in the presence
of carbonate salt
⇑
⇑
Xiangchao Xu, Yao Ai, Rongzhou Wang, Liping Liu, Jiazhi Yang , Feng Li
School of Chemical Engineering, Nanjing University of Science & Technology, Nanjing 210094, PR China
a r t i c l e i n f o
a b s t r a c t
A ruthenium complex bearing a functional 2,20-bibenzimidazole ligand [(p-cymene)Ru(BiBzImH2)Cl][Cl]
was designed, synthesized and found to be a general and highly efficient catalyst for the synthesis of
quinolines via acceptorless dehydrogenative coupling of o-aminobenzyl alcohols with ketones in the
presence of carbonate salt. It was confirmed that NH units in the ligand are crucial for catalytic activity.
The application of this catalytic system for the scale-gram synthesis of biologically active molecular was
also undertaken. Notably, this research exhibits new potential of metal–ligand bifuctional catalysts for
acceptorless dehydrogenative reactions.
Article history:
Received 10 November 2020
Revised 15 December 2020
Accepted 17 December 2020
Available online 24 December 2020
Keywords:
Acceptorless hydrogenative coupling
Ruthenium
Ó 2020 Elsevier Inc. All rights reserved.
Metal-ligand bifunctional catalyst
2,20-bibenzimidazole
Quinolines
1. Introduction
liberation of hydrogen gas [8]. Such methodologies provide the
clearest and most atom-economical processes as alternatives to
Quinolines represent an important class of nitrogen-containing
heterocycles which were frequently found in the alkaloid family
[1]. They exhibited also a wide range of biological properties and
were utilized as ligands of transition metal catalysts and
organocatalysts [2,3], and building blocks of functional materials
[4]. For this reason, a series of classical synthetic methods, such
as Skraup, Doebner-von Miller, Conrad-Limpach, Pfitzinger and
Friedlaeder synthesises, have been developed in past decades [5].
Among them, Friedlaeder synthesises, e.g. acid or base-mediated
coupling of o-aminobenzaldehydes with ketones, are considered
to be one of the most straightforward methods to access quinolines
although o-aminobenzaldehydes are very unstable materials and
prone to self-condensation [6]. In recent years, transition metal-
catalyzed oxidative cyclization of o-aminobenzyl alcohols with
ketones as a modified Friedlaeder synthesises have been reported
[7]. However, these procedures required extra addition of large
excess of ketones, unsaturated olefines or molecular oxygen as sac-
rificial hydrogen acceptors to generate in situ o-
aminobenzaldehydes from o-aminobenzyl alcohols. More recently,
much attention has been paid to the development of transition
metal-catalyzed acceptorless dehydrogenative reactions with the
traditional oxidation reactions. Several groups have reported
acceptorless dehydrogenative coupling of o-aminobenzyl alcohols
with ketones to quinolines catalyzed by iridium [9], ruthenium
[10], nickel [11], manganese [12] and rhenium complexes [13].
However, all these procedures required the presence of large
amount of inorganic strong base (KOH, tBuOK), and thus the poten-
tial of practical application is still highly restricted.
Fujita and co-workers have developed a series of Cp*Ir com-
plexes bearing a bipyridine or a bipyridonate ligand, which exhib-
ited high activities for acceptorless dehydrogenation of alcohols
and N-heterocycles [14], and hydrogen production from an
alcohol-water solution under basic conditions based on the con-
cept of ligand-promoted dehydrogenation [15]. We have also
demonstrated that such Cp*Ir complexes are highly effective
metal–ligand bifunctional catalysts for hydrogen auto-transfer
process [16], acceptorless dehydrogenative cyclization [17], and
transfer hydrogenation of aldehydes and ketones [18]. As part of
a continuing interest in the field, we turned our attention from
iridium complexes to ruthenium ones because ruthenium is much
cheaper than iridium [19]. Herein, we with to describe the design
and synthesis, of
bibenzimidazole ligand that contains a tautomerism structure
and protic hydrogens like -hydroxypyridine (Scheme 1). Further-
more, this complex was found to be a general and highly efficient
a
ruthenium complex bearing
a
2,20-
a
⇑
Corresponding authors.
E-mail addresses: jiazhiyang@njust.edu.cn (J. Yang), fengli@njust.edu.cn (F. Li).
https://doi.org/10.1016/j.jcat.2020.12.016
0021-9517/Ó 2020 Elsevier Inc. All rights reserved.

X. Xu, Y. Ai, R. Wang et al.
Journal of Catalysis 395 (2021) 340–349
[OTf]2
O
HO
HO
HO
Ir H2O
Ir H2O
Ir Cl
Ir Cl
Cl
O
OH
N
N
N
N
N
N
[OTf]2
[Na]
HO
Cl
Cl
O
Me
N
Ru Cl
N
Ir H2O
Ir OH
N
Ru H2O
OH
N
O
N
OH
N
N
N
N
N
N
H
H
This work
Scheme 1. Metal-Ligand Bifunctional Catalysts for Acceptorless Dehydrogenation.
catalyst for the acceptorless dehydrogenative coupling of o-
aminobenzyl alcohols with ketones to quinolines in the presence
of carbonate.
2. Result and discussion
The synthetic procedure to prepare the designed ruthenium
complex [(p-cymene)Ru(BiBzImH2)Cl][Cl] was outlined in
Scheme 2. The reaction of [(p-cymene)RuCl2]2 with 2,20- bibenzim-
idazole (2.2 equiv) was performed in THF at 60 °C for 12 h. The
formed yellow solid was collected by filtration and then washed
with THF. The complex is stable to air and moisture both in the
solid state and in solution. The crystal for X-ray crystallography
was obtained and its molecular structure was shown in Fig. 1 with
pertinent bond lengths and angles. 2,20-Bibenzimidazole ligand is
bonded to ruthenium center with two nitrogen atoms with a bond
angle of 76.60 (19) in a chelating fashion. Bond lengths of N1-Ru
and N3-Ru are 2.118 (5) Å and 2.135 (5) Å, respectively.
With the synthesized [(p-cymene)Ru(BiBzImH2)Cl][Cl] (cat. 1)
in hand, we investigated its catalytic activity for the acceptorless
dehydrogenative coupling of o-aminobenzyl alcohol (1a) with ace-
tophenone (2a). In the presence of cat. 1 (1 mol %) and Cs2CO3 (0.5
equiv), the reaction was carried out at 125 °C for 12 h to afford the
product 3aa in 92% yield (Table 1, entry 1). Using its analog [(p-
cymene)Ru(BiBzImMe2)Cl][Cl] (cat. 2) as an alternative catalyst,
the product 3aa was obtained in only 16% yield (Table 1, entry
Fig. 1. X-ray structure of [(p-cymene)Ru(BiBzImH2)Cl][Cl] (thermal ellipsoids set at
50% probability). Hydrogen atoms have been omitted for clarity. Selected bond
lengths [Å] and angles [deg]: Ru-N1, 2.118 (5); Ru-N3, 2.135 (5); Ru-C1, 2.175 (6);
Ru-C4, 2.178(6); Ru-C5, 2.191 (6); Ru-C2, 2.194 (6); Ru-C6, 2.202 (7); Ru-C3, 2.214
(6); Ru-Cl, 2.3982 (18); N1-Ru-N3, 76.60 (19); N1-Ru-Cl1, 85.24 (15); N3-Ru-Cl1,
84.90 (15).
the ligand are crucially important for the catalytic activity of ruthe-
nium complexes. When other ruthenium complexes (cat. 5–11)
were examined, reactions afforded the product 3aa in 14–41%
yields (Table 1, entries 5–11). Then, cat. 1 was chosen as a catalyst
for further investigation. Tries to use of K2CO3 or Na2CO3 as an
alternative base, to reduce the amount of Cs2CO3, and to decrease
reaction temperature resulted in relatively low yields (Table 1,
entries 12–15).
2). In the case of ruthenium complexes bearing a functional
a-
hydroxypyridine ligand [(p-cymene)Ru (6,60-(OH)2bpy)(H2O)]
[OTf]2 (cat. 3) and its analog [(p-cymene) (6,60-(OMe)2bpy)(H2O)]
[OTf]2 (cat. 4), product 3aa was obtained in 89% and 19% yields,
respectively (Table 1, entries 3–4). Obviously, NH or OH units in
Cl
N
Ru Cl
N
THF, 60 oC
N
[(p-cymene)RuCl2]2
+
N
N
H
N
H
under air
N
N
H
H
67% yield
Scheme 2. The Synthesis of [(p-cymene)Ru(BiBzImH2)Cl][Cl].
341

X. Xu, Y. Ai, R. Wang et al.
Journal of Catalysis 395 (2021) 340–349
Table 1
products 3ap and 3aq in 80% and 84% yields, respectively. Readi-
lyreducible or labile substituents, such as nitro and cyano groups,
were well tolerated, reactions afforded desired products 3ar and
3as in 82% and 85% yields, respectively. When 1-(4-
phenylphenyl)ethanone and 1-(pyrazin-2-yl)ethanone were used,
corresponding products 3at and 3au were made in 80% and 76%
yields, respectively. Non-methyl ketones, such as propiophenone,
n-butyrophenone and 1-tetralone could be converted to corre-
sponding quinolines 3av-3ax in 77–82% yields. For aliphatic
ketones, such as 1-cyclopropylethanone and 3,3-dimethylbutan-
2-one, desired products 3ay and 3az were successfully isolated in
86% and 83% yields, respectively.
Coupling of o-Aminobenzyl Alcohol (1a) with Acetophenone (2a) under Various
Conditions.a
To expand further generality of reaction, the couplings with
respect to o-aminobenzyl alcohols were investigated (Table 3).
Transformations of o-aminobenzyl alcohols bearing an electron-
rich substituent gave corresponding products 3ba and 3ca in 84%
and 87% yields, respectively. Similarly, desired products 3da-3ga
were obtained in 81–85% yields when o-aminobenzyl alcohols
bearing an electron-efficient substituent were utilized as
substrates.
Based experimental results, two possible simultaneous mecha-
nisms for the present synthesis of quinolines via acceptorless
dehydrogenative coupling of o-aminobenzyl alcohols with ketones
were presented (Scheme 3). The initial step of reaction involved
the formation of species A via the reaction of cat. 1 with Cs2CO3.
With the process of the activation of alcohols, the ligand accepted
a proton to give alkoxy ruthenium species B, which further under-
went ß-hydrogen elimination to give aldehydes and ruthenium
hydride species C. In mechanism I, the ligand-promoted simultane-
ous hydrogen transfer from the hydride on the ruthenium and the
proton on the ligand resulted in the regeneration of catalytic spe-
cies A and the liberation of a molecular hydrogen. Furthermore, a
base-promoted cross-aldol condensation between ketones and
resulting
o-aminobenzaldehydes
afforded
a,ß-unsaturated
ketones, followed by an intramolecular cyclodehydration occurred
to give quinolines. In mechanism II, after a base-promoted cross-
adol condensation between ketones and resulting aldehydes, the
hydride on the ruthenium and proton on the ligand of species C
were simultaneously transferred to the C@C bond of
unsaturated ketones, resulted in the regeneration of catalytic spe-
cies A and the liberation of -alkylated ketones, which underwent
a,ß-
a
sequential intramolecular cyclodehydration/dehydrogenation to
afford corresponding quinolines.
To support the proposed mechanism for acceptorless dehydro-
genation, the liberation of gas in the process of model reaction
was collected through a water displacement (Table 1, entry 1). This
gas was determined to molecular hydrogen by GC analysis and was
calculated to be 87% yield (299.15 K, 100,300 Pa, 21.6 mL).
As outlined in Scheme 4, the gram-scale synthesis of a biologi-
cally active molecule (Na+ channel antagonists) was represented in
order to demonstrate the application of this catalytic system.
Under standard conditions, the coupling of 1a (25 mmol) and 2a
(30 mmol, 1.2 equiv) gave the product 3aa in 85% yield. Subse-
quently, the reduction of 3aa was carried out in the presence of
NaBH3CN (2 equiv) to afford the product 4 in 71% yield, which
are further reacted with NH2CN (7 equiv) to give the desired pro-
duct 5 in 30% yield according to the previous report [20].
aReaction conditions: 1a (1 mmol), 2a (1.2 mmol), catalyst (1 mol % Ru), base
(x equiv), tert-amyl alcohol (1 mL), 12 h.
bYield was determined based on the 1H NMR spectrum of the crude reaction mixture
with 1,3,5-trimethoxybenzene as the internal standard.
cIsolated yield.
Having established the optimal conditions (Table 1, entry 1), the
scope of reaction with respect to ketones was conducted and these
results are outlined in Table 2. Transformations of acetophenones
bearing an electron-rich substituent gave the corresponding prod-
ucts 3ab-3ah in 76–84% yields. Acetophenones bearing one or two
halogen atoms were also readily cyclized to desired products 3ai-
3ao in 77–85% yields.
Furthermore, this system was applied to substrates bearing
more serious electron-deficient substituents, such as trifluo-
romethyl and trifluoromethoxy groups, affording corresponding
3. Conclusions
In summary, we demonstrated the design and synthesis of a
ruthenium complex bearing a functional 2,20-bibenzimidazole
ligand and developed it as the first catalyst for acceptorless dehy-
drogeantive coupling of o-aminobenzyl alcohols with ketones to
quinolines in the presence of carbonate salt. Under environmen-
342

X. Xu, Y. Ai, R. Wang et al.
Journal of Catalysis 395 (2021) 340–349
Table 2
Table 3
Scope of Reaction with Respect to Ketone.a,b
Scope of Reaction with Respect to o-Aminobenzyl Alcohols.a,b
a
Reaction conditions: 1 (1 mmol), 2a (1.2 mmol), cat. 1 (1 mol %), Cs2CO3 (0.5
equiv), tert-amyl alcohol (1 mL), 125 °C, 12 h.
b
Isolated yield.
intensity). Accurate masses are reported for the molecular ion
[M]+, [M + H]+ or [M ꢀ Cl]+. Melting points were measured on a
X-6 micro-melting apparatus. Proton nuclear magnetic resonance
(1H NMR) spectra were recorded at 500 MHz. Chemical shifts are
reported in delta (d) units, parts per million (ppm) downfield from
tetramethylsilane or ppm relative to the center of the singlet at
7.26 ppm for CDCl3 and 3.31 ppm for CD3OD. Coupling constants
J values are reported in Hertz (Hz), and the splitting patterns were
designated as follows: s, singlet; d, doublet; t, triplet; m, multiplet;
b, broad. 13C{1H} NMR spectra were recorded on a 125 MHz spec-
trophotometer with broadband 1H decoupling. Chemical shifts for
13C{1H} NMR spectra are reported in delta (d) units, ppm relative to
the center of the triplet at 77.0 ppm for CDCl3 and 49.0 ppm for
CD3OD. 13C NMR spectra were routinely run with broadband
decoupling. Analytical thin-layer chromatography (TLC) was car-
ried out using 0.2 mm commercial silica gel plates.
[(p-cymene)Ru(6,60-(OH)2bpy)(H2O)][OTf]2 (cat. 3) [19c], [(p-
cymene)Ru(6,60-(OMe)2bpy)(H2O)][OTf]2 (cat. 4) [19c], [(p-
cymene)RuCl2]2 (cat. 5) [21], {(p-cymene)RuCl2[P(NMe2)3]} (cat.
6) [22], [(p-cymene)RuCl2(PPh3)] (cat. 7) [23], [{RuCl(m-Cl)(g3 g3
: -
C10H16)}2] (cat. 8) [24], [RuCl2(PPh3)3] (cat. 9) [25], [(terpy)3RuCl3]
(cat. 10) [26] and [Ru(cod)Cl2] (cat. 11) [27] were synthesized
according the previous reports.
4.2. Procedure for the synthesis of [(p-cymene)Ru(BiBzImH2)Cl][Cl]
a
Reaction conditions: 1a (1 mmol), 2 (1.2 mmol), cat. 1 (1 mol %), Cs2CO3 (0.5
To an oven-dried Schlenk tube were added [(p-cymene)RuCl2]2
(100 mg, 0.163 mmol), 2-(1H-benzo[d]imidazol-2-yl)-1H-benzo[d]
imidazole (84 mg, 0.359 mmol, 2.2 equiv) and THF (6 mL), and the
mixture was heated at 60 °C for 12 h. The reaction mixture was
allowed to cool to ambient temperature. Then, the precipitate
was filtered and washed with THF, affording the resulting product.
[(p-cymene)Ru(BiBzImH2)Cl][Cl]. Yellow solid; 67% yield
(110 mg); mp > 300 °C; 1H NMR (500 MHz, CD3OD) 8.13 (d,
J = 8.1 Hz, 2H), 7.85 (d, J = 8.0 Hz, 2H), 7.68–7.61 (m, 4H), 6.45
(d, J = 6.1 Hz, 2H), 6.25 (d, J = 6.1 Hz, 2H), 2.45–2.43 (m, 1H),
2.31 (s, 3H), 0.93 (d, J = 6.9 Hz, 6H); 13C{1H} NMR (125 MHz, CD3-
OD) d 143.5, 143.0, 136.2, 127.7, 126.7, 118.8, 115.3, 84.6, 80.6,
32.5, 22.3, 19.4. HRMS (ESI) m/z calcd for C24H24ClN4Ru+ (M)+
505.07275, found 505.07269.
equiv), tert-amyl alcohol (1 mL), 125 °C, 12 h.
b
Isolated yield.
tally benign conditions,
a series of desirable products were
obtained in high yields. It was confirmed that NH units in the
ligand are crucial for catalytic activity. The application of this cat-
alytic system for the scale-gram synthesis of biologically active
molecular was also undertaken. Notably, this research exhibits
new potential of metal–ligand bifuctional catalysts for acceptorless
dehydrogenative reactions.
4. Experimental section
4.1. General experimental details
4.3. Procedure for the synthesis of [(p-cymene)Ru(BiBzImMe2)Cl][Cl]
High-resolution mass spectra (HRMS) were obtained on a HPLC-
To an oven-dried Schlenk tube were added [(p-cymene)RuCl2]2
Q-TOF-MS (Micro) spectrometer and are reported as m/z (relative
(100 mg, 0.163 mmol), 1-methyl-2-(1-methyl-1H-benzo[d]imida
343

X. Xu, Y. Ai, R. Wang et al.
Journal of Catalysis 395 (2021) 340–349
Mechanism I
Cl
H2N
O
Ru
N
N
R1
OH
NH2
R1
N
N
H
H
B
Cl
Cl
O
R3
H2O
R2
Ru
Ru Cl
R3
O
NH2
Cs2CO3
-HCl
N
N
N
O
-H2O
R1
R1
N
R2
N
N
N
R2
NH2
R3
N
N
H
H
R1
H
cat. 1
A
Cl
H
Ru
N
N
H2
N
N
H
H
C
Cl
Mechanism II
H2N
O
Ru
N
N
R1
N
N
H
OH
NH2
R1
H
B
Cl
Cl
Cl
H
Ru
Ru Cl
Cs2CO3
Ru
O
R1
+
N
N
N
N
N
N
NH2
-HCl
N
H
N
N
N
N
N
H
H
H
C
H
cat. 1
A
Cl
H2N
R1
O
H
R3
R2
Ru
N
R3
N
O
N
R3
R2
R3
R2
-H2
-H2O
N
R2
O
NH2
R1
R1
R1
H
H2O
H
R2
N
N
R3
C
:
vacant site
Scheme 3. Proposed Reaction Mechanisms.
cat. 1 (1 mol %)
Cs2CO3 (0.5 equiv)
O
OH
NH2
1a (25 mol)
+
tert-amyl alcohol
N
125 oC, 12 h
2a (1. 2 equiv)
3aa, 85% yield
NaBH3CN (2 equiv)
AcOH, rt, 10 h
NH2CN (7 equiv)
N
N
H
.
ethanol, reflux, 2 day
1N HCl
HCl
.
HCl HN
5, 30% yield
Na+ Channel antagonists
NH2
4, 71% yield
Scheme 4. The Gram-Scale Synthesis of Biologically Active Molecule (Na+ Channel Antagonists).
344

X. Xu, Y. Ai, R. Wang et al.
Journal of Catalysis 395 (2021) 340–349
zol-2-yl)-1H-benzo[d]imidazole (94 mg, 0.359 mmol, 2.2 equiv)
and THF (6 mL), and the mixture was heated at 60 °C for 12 h.
The reaction mixture was allowed to cool to ambient temperature.
Then, the precipitate was filtered and washed with THF, affording
the resulting product.
[(p-cymene)Ru(BiBzImMe2)Cl][Cl]. Yellow solid; 62% yield
(108 mg); mp > 300 °C; 1H NMR (500 MHz, CD3OD) 8.15–8.13
(m, 2H), 7.92–7.90 (m, 2H), 7.73–7.69 (m, 4H), 6.42 (d, J = 6.0 Hz,
2H), 6.26 (d, J = 6.1 Hz, 2H), 4.46 (s, 6H), 2.42–2.39 (m, 1H), 2.26
(s, 3H), 0.92 (d, J = 6.8 Hz, 6H); 13C{1H} NMR (125 MHz, CD3OD)
d 144.8, 142.7, 138.3, 128.1, 127.2, 119.4, 113.7, 84.9, 81.1, 36.0,
32.4, 22.3, 19.4. HRMS (ESI) m/z calcd for C26H28ClN4Ru+ (M + H)+
533.10405, found 533.10425.
{1H} NMR (125 MHz, CDCl3) d 161.1, 157.1, 148.2, 141.1, 136.7,
129.8, 129.7, 129.6, 127.4, 127.2, 126.3, 120.0, 119.1, 115.3,
112.7, 53.4.
2-(4-Methoxyphenyl)quinoline (3ag) [28]. White solid; 80%
yield (188 mg); mp 122–123 °C; 1H NMR (500 MHz, CDCl3) d
8.19–8.13 (m, 4H), 7.85–7.79 (m, 2H), 7.71 (t, J = 7.3 Hz, 1H),
7.50 (t, J = 7.4 Hz, 1H), 7.06 (d, J = 8.8 Hz, 2H), 3.89 (s, 3H); 13C
{1H} NMR (125 MHz, CDCl3) d 160.8, 156.9, 148.3, 136.6, 132.3,
129.5, 128.9, 127.4, 126.9, 125.9, 118.5, 114.2, 55.4.
2-(Benzo[d][1,3]dioxol-5-yl)quinoline (3ah) [29]. Light yellow
solid; 81% yield (202 mg); mp 87–88 °C; 1H NMR (500 MHz, CDCl3)
d 8.16–8.11 (m, 2H), 7.79–7.74 (m, 3H), 7.70 (t, J = 7.7 Hz, 1H), 7.66
(d, J = 8.1 Hz, 1H), 7.50–7.47 (m, 1H), 6.95 (d, J = 8.1 Hz, 1H), 6.03 (s,
2H); 13C{1H} NMR (125 MHz, CDCl3) d 155.6, 148.8, 148.4, 148.2,
136.6, 134.1, 129.6, 129.5, 127.4, 127.0, 126.0, 121.7, 118.6,
108.4, 107.9, 101.3.
2-(3-Fluorophenyl)quinoline (3ai) [32]. Pale-yellow solid; 80%
yield (179 mg); mp 47–48 °C; 1H NMR (500 MHz, CDCl3) d 8.23 (d,
J = 8.6 Hz, 1H), 8.18 (d, J = 8.5 Hz, 1H), 7.93 (d, J = 8.7 Hz, 2H), 7.85–
7.82 (m, 2H), 7.74 (t, J = 7.7 Hz, 1H), 7.54 (t, J = 7.5 Hz, 1H), 7.50–
7.46 (m, 1H), 7.17–7.14 (m, 1H); 13C{1H} NMR (125 MHz, CDCl3) d
164.3 (d, JC-F = 244.2 Hz), 155.8, 148.2, 142.0 (d, JC-F = 7.8 Hz), 136.9,
130.3 (d, JC-F = 8.1 Hz), 129.8, 129.8, 127.5, 127.4, 126.6, 123.1,
118.7, 116.2 (d, JC-F = 20.9 Hz), 114.6 (d, JC-F = 22.6 Hz).
2-(4-Fluorophenyl)quinoline (3aj) [33]. White solid; 79% yield
(176 mg); mp 90–91 °C; 1H NMR (500 MHz, CDCl3) d 8.22–8.14 (m,
4H), 7.83 (d, J = 8.7 Hz, 2H), 7.73 (t, J = 7.7 Hz, 1H), 7.52 (t, J = 7.5 Hz,
1H), 7.20 (t, J = 8.7 Hz, 2H); 13C{1H} NMR (125 MHz, CDCl3) d 164.8
(d, JC-F = 247.5 Hz), 156.2, 148.2, 136.9, 135.8, 129.8, 129.7, 129.4
(d, JC-F = 8.3 Hz), 127.5, 127.1, 126.3, 118.6, 115.8 (d, JC-F = 21.5 Hz).
2-(3-Chlorophenyl)quinoline (3ak) [31]. Light yellow solid;
77% yield (184 mg); mp 91–92 °C; 1H NMR (500 MHz, CDCl3) d
8.17–8.13 (m, 3H), 7.99–7.97 (m, 1H), 7.77–7.74 (m, 2H), 7.70 (t,
J = 7.7 Hz, 1H), 7.49 (t, J = 7.5 Hz, 1H), 7.40 (d, J = 5.3 Hz, 2H);
13C{1H} NMR (125 MHz, CDCl3) d 155.6, 148.1, 141.3, 136.9,
134.8, 129.9, 129.8, 129.7, 129.2, 127.6, 127.4, 127.2, 126.5,
125.5, 118.5.
4.4. Procedure for acceptorless dehydrogenative coupling of ketones
with o-aminobenzyl alcohols to quinolines catalyzed by [(p-cymene)
Ru(BiBzImH2)Cl][Cl]
In a round-bottomed flask with a condenser tube were added o-
aminobenzyl alcohols 1 (1 mmol) and ketones 2 (1.2 mmol, 1.2
equiv), cat. 1 (6 mg, 0.01 mmol, 1 mol %), Cs2CO3 (163 mg,
0.5 mmol, 0.5 equiv) and tert-amyl alcohol (1 mL). The reaction
mixture was heated at 125 °C in an oil bath for 12 h and then
cooled to ambient temperature, concentrated in vacuo and purified
by flash column chromatography with hexane/ethyl acetate (10:1,
v/v) to afford corresponding products.
2-Phenylquinoline (3aa) [28]. White solid; 86% yield (177 mg);
mp 84–85 °C; 1H NMR (500 MHz, CDCl3) d 8.22–8.16 (m, 4H), 7.88
(d, J = 8.6 Hz, 1H), 7.83 (d, J = 8.1 Hz, 1H), 7.72 (t, J = 7.5 Hz, 1H),
7.54–7.50 (m, 3H), 7.46 (t,
J =
7.3 Hz, 1H); 13C{1H} NMR
(125 MHz, CDCl3) d 157.3, 148.3, 139.6, 136.7, 129.7, 129.6,
129.3, 128.8, 127.5, 127.4, 127.1, 126.2, 118.9.
2-(o-Tolyl)quinoline (3ab) [29]. White solid; 84% yield
(184 mg); mp 75–76 °C; 1H NMR (500 MHz, CDCl3) d 8.20–8.15
(m, 2H), 7.86 (d, J = 8.1 Hz, 1H), 7.73 (t, J = 7.7 Hz, 1H), 7.57–7,49
(m, 3H), 7.34–7.39 (m, 3H), 2.41 (s, 3H); 13C{1H} NMR (125 MHz,
CDCl3) d 160.3, 147.9, 140.7, 136.0, 136.0, 130.8, 129.7, 129.6,
128.5, 127.5, 126.7, 126.4, 126.0, 122.3, 20.3.
2-(4-Chlorophenyl)quinoline (3al) [32]. White solid; 83% yield
(198 mg); mp 110–111 °C; 1H NMR (500 MHz, CDCl3) d 8.24 (d,
J = 8.6 Hz, 1H), 8.16–8.12 (m, 3H), 7.86–7.83 (m, 2H), 7.74 (t,
J = 7.7 Hz, 1H), 7.54 (t, J = 7.5 Hz, 1H), 7.51 (d, J = 8.6 Hz, 2H);
13C{1H} NMR (125 MHz, CDCl3) d 156.0, 148.2, 138.0, 136.9,
135.5, 129.8, 129.7, 129.0, 128.8, 127.5, 127.2, 126.5, 118.5.
2-(3,4-Dichlorophenyl)quinoline (3am) [29]. Light yellow
solid; 78% yield (214 mg); mp 105–106 °C; 1H NMR (500 MHz,
CDCl3) d 8.31 (d, J = 2.1 Hz, 1H), 8.22 (d, J = 8.6 Hz, 1H), 8.15 (d,
J = 8.5 Hz, 1H), 7.99 (dd, J = 8.4 and 2.1 Hz, 1H), 7.83–7.79 (m,
2H), 7.74 (t, J = 7.7 Hz, 1H), 7.57–7.53 (m, 2H); 13C{1H} NMR
(125 MHz, CDCl3) d 154.4, 148.1, 139.4, 137.0, 133.5, 133.1,
130.6, 129.9, 129.7, 129.3, 127.4, 127.3, 126.7, 126.4, 118.1.
2-(3-Bromophenyl)quinoline (3an) [29]. White solid; 85%
yield (242 mg); mp 73–74 °C; 1H NMR (500 MHz, CDCl3) d 8.34
(s, 1H), 8.19–8.15 (m, 2H), 8.05 (d, J = 7.8 Hz, 1H), 7.81–7.78 (m,
2H), 7.72 (t, J = 7.6 Hz, 1H), 7.57 (d, J = 7.9 Hz, 1H), 7.52 (t,
J = 7.5 Hz, 1H), 7.36 (t, J = 7.9 Hz, 1H); 13C{1H} NMR (125 MHz,
CDCl3) d 155.5, 148.1, 141.6, 136.9, 132.1, 130.5, 130.2, 129.8,
129.7, 127.4, 127.3, 126.6, 126.0, 123.1, 118.6.
2-(p-Tolyl)quinoline (3ac) [28]. White solid; 81% yield
(177 mg); mp 74–75 °C; 1H NMR (500 MHz, CDCl3) d 8.17 (t,
J = 9.8 Hz, 2H), 8.08 (d, J = 8.1 Hz, 2H), 7.86 (d, J = 8.6 Hz, 1H),
7.81 (d, J = 8.1 Hz, 1H), 7.71 (t, J = 7.7 Hz, 1H), 7.50 (t, J = 7.4 Hz,
1H), 7.33 (d, J = 8.0 Hz, 2H), 2.43 (s, 3H); 13C{1H} NMR (125 MHz,
CDCl3) d 157.2, 148.2, 139.3, 136.8, 136.6, 129.6, 129.5, 127.4,
127.0, 126.0, 118.8, 21.3.
2-(4-Ethylphenyl)quinoline (3ad) [30]. White solid; 82% yield
(192 mg); mp 48–49 °C; 1H NMR (500 MHz, CDCl3) d 8.17 (t,
J = 8.4 Hz, 2H), 8.09 (d, J = 8.2 Hz, 2H), 7.85 (d, J = 8.6 Hz, 1H),
7.81 (d, J = 8.1 Hz, 1H), 7.71 (t, J = 7.7 Hz, 1H), 7.50 (t, J = 7.0 Hz,
1H), 7.36 (d, J = 8.3 Hz, 2H), 2.73 (q, J = 7.6 Hz, 2H), 1.29 (t,
J = 7.6 Hz, 3H); 13C{1H} NMR (125 MHz, CDCl3) d 157.4, 148.3,
145.7, 137.1, 136.6, 129.6, 129.5, 128.4, 127.5, 127.4, 127.1,
126.1, 118.9, 28.7, 15.5.
2-(4-Isopropylphenyl)quinoline (3ae) [31]. Light yellow solid;
82% yield (202 mg); mp 86–87 °C; 1H NMR (500 MHz, CDCl3) d
8.20–8.15 (m, 2H), 8.10 (d, J = 8.2 Hz, 2H), 7.86 (d, J = 8.6 Hz,
1H), 7.82 (d, J = 8.1 Hz, 1H), 7.71 (t, J = 7.7 Hz, 1H), 7.50 (t,
J = 7.5 Hz, 1H), 7.40 (d, J = 8.2 Hz, 2H), 3.02–2.96 (m, 1H), 1.31
(d, J = 7.0 Hz, 6H); 13C{1H} NMR (125 MHz, CDCl3) d 157.4, 150.3,
148.3, 137.3, 136.6, 129.7, 129.5, 127.5, 127.4, 127.0, 126.9,
126.0, 118.9,34.0, 23.9.
2-(3-Methoxyphenyl)quinoline (3af) [30]. Light yellow solid;
76% yield (179 mg); mp 107–108 °C; 1H NMR (500 MHz, CDCl3) d
8.19 (t, J = 9.5 Hz, 2H), 7.86 (d, J = 8.6 Hz, 1H), 7.82 (d, J = 8.1 Hz,
1H), 7.77–7.76 (m, 1H), 7.73–7.69 (m, 2H), 7.52 (t, J = 7.5 Hz,
1H), 7.42 (t, J = 7.9 Hz, 1H), 7.02–7.00 (m, 1H), 3.92 (s, 3H); 13C
2-(4-Bromophenyl)quinoline (3ao) [29]. White solid; 82%
yield (233 mg); mp 114–115 °C; 1H NMR (500 MHz, CDCl3) d
8.24 (d, J = 8.6 Hz, 1H), 8.16 (d, J = 8.5 Hz, 1H), 8.07 (d,
J = 8.5 Hz, 2H), 7.85–7.82 (m, 2H), 7.74 (t, J = 7.6 Hz, 1H), 7.66 (d,
J = 8.5 Hz, 2H), 7.54 (t, J = 7.4 Hz, 1H); 13C{1H} NMR (125 MHz,
CDCl3) d 155.9, 148.2, 138.5, 136.9, 131.9, 129.8, 129.7, 129.1,
127.5, 127.2, 126.5, 123.9, 118.4.
2-(4-(Trifluoromethyl)phenyl)quinoline (3ap) [32]. White
solid; 80% yield (219 mg); mp 122–123 °C; 1H NMR (500 MHz,
345

X. Xu, Y. Ai, R. Wang et al.
Journal of Catalysis 395 (2021) 340–349
CDCl3) d 8.27–8.22 (m, 3H), 8.19 (d, J = 8.5 Hz, 1H), 7.86–7.82 (m,
2H), 7.77–7.73 (m, 3H), 7.55 (t, J = 7.5 Hz, 1H); 13C{1H} NMR
(125 MHz, CDCl3) d 155.6, 148.2, 142.9, 137.1, 131.2 (q, JC-
{1H} NMR (125 MHz, CDCl3) d 163.4, 147.8, 135.9, 129.3, 128.4,
127.4, 126.7, 125.2, 119.1, 18.0, 10.2.
2-(Tert-butyl)quinoline (3az) [38]. Light yellow oil; 83% yield
(154 mg); 1H NMR (500 MHz, CDCl3) d 8.06 (d, J = 8.5 Hz, 2H),
7.76 (d, J = 8.2 Hz, 1H), 7.66 (t, J = 7.6 Hz, 1H), 7.52 (d, J = 8.7 Hz,
1H), 7.46 (t, J = 7.4 Hz, 1H), 1.47 (s, 9H); 13C{1H} NMR (125 MHz,
CDCl3) d 169.2, 147.4, 135.8, 129.4, 128.9, 127.2, 126.4, 125.6,
118.2, 38.1, 30.1.
6-methyl-2-phenylquinoline (3ba) [39]. White solid; 84% yield
(184 mg); mp 60–61 °C; 1H NMR (500 MHz, CDCl3) d 8.15–8.10 (m,
3H), 8.07 (d, J = 8.5 Hz, 1H), 7.83 (d, J = 8.6 Hz, 1H), 7.57–7.50 (m,
4H), 7.46–7.43 (m, 1H), 2.54 (s, 3H); 13C{1H} NMR (125 MHz,
CDCl3) d 156.4, 146.8, 139.7, 136.0, 131.9, 129.3, 129.0, 128.7,
127.4, 127.1, 126.3, 118.9, 21.5.
6-methoxy-2-phenylquinoline (3ca) [40]. White solid; 87%
yield (204 mg); mp 128–129 °C; 1H NMR (500 MHz, CDCl3) d
8.14–8.06 (m, 4H), 7.84 (d, J = 8.6 Hz, 1H), 7.52 (t, J = 7.6 Hz, 2H),
7.44 (t, J = 7.3 Hz, 1H), 7.40 (dd, J = 9.2 and 2.7 Hz, 1H), 7.10 (d,
J = 2.5 Hz, 1H), 3.95 (s, 3H); 13C{1H} NMR (125 MHz, CDCl3) d
157.7, 155.1, 144.4, 139.8, 135.5, 131.2, 128.9, 128.8, 128.1,
127.3, 122.3, 119.3, 105.0, 55.5.
6-fluoro-2-phenylquinoline (3da) [41]. White solid; 83% yield
(186 mg); mp 90–91 °C; 1H NMR (500 MHz, CDCl3) d 8.17–8.14 (m,
4H), 7.90 (d, J = 8.7 Hz, 1H), 7.55–7.43 (m, 5H); 13C{1H} NMR
(125 MHz, CDCl3) d 161.3 (d, J = 246.5 Hz), 156.7, 145.3, 139.3,
136.1 (d, J = 4.9 Hz), 132.2 (d, J = 9.0 Hz), 129.4, 128.8, 127.4,
119.9, 119.7, 119.6, 110.5 (d, J = 21.5 Hz).
6-chloro-2-phenylquinoline (3ea) [41]. White solid; 85% yield
(204 mg); mp 109–110 °C; 1H NMR (500 MHz, CDCl3) d 8.16–8.09
(m, 4H), 7.90 (d, J = 8.6 Hz, 1H), 7.80 (s, 1H), 7.66 (dd, J = 9.0 and
2.4 Hz, 1H), 7.53 (d, J = 7.4 Hz, 2H), 7.49–7.46 (m, 1H); 13C{1H}
NMR (125 MHz, CDCl3) d 157.5, 146.6, 139.2, 135.8, 131.9, 131.3,
130.5, 129.5, 128.9, 127.7, 127.5, 126.1, 119.7.
7-chloro-2-phenylquinoline (3fa) [42]. White solid; 83% yield
(200 mg); mp 110–111 °C; 1H NMR (500 MHz, CDCl3) d 8.20–8.15
(m, 4H), 7.89 (d, J = 8.6 Hz, 1H), 7.77 (d, J = 8.7 Hz, 1H), 7.55–7.52
(m, 2H), 7.49–7.47 (m, 2H); 13C{1H} NMR (125 MHz, CDCl3) d 158.2,
148.6, 139.1, 136.5, 135.4, 129.6, 128.8, 128.6, 128.6, 127.5,127.2,
125.4, 119.0.
7-bromo-2-phenylquinoline (3ga) [43]. White solid; 81% yield
(229 mg); mp 113–114 °C; 1H NMR (500 MHz, CDCl3) d 8.36 (s, 1H),
8.18–8.14 (m, 3H), 7.89 (d, J = 8.6 Hz, 1H), 7.68 (d, J = 8.7 Hz, 1H),
7.60 (dd, J = 8.6 and 1.8 Hz, 1H), 7.54–7.46 (m, 3H); 13C{1H} NMR
(125 MHz, CDCl3) d 158.1, 148.9, 139.1, 136.6, 132.0, 129.7,
129.7, 128.9, 128.7, 127.6, 125.7, 123.7, 119.2.
= 32.2 Hz), 129.9, 129.8, 127.8, 127.5, 127.4, 126.8, 125.7, 125.7,
F
125.3 (q, JC-F = 270.4 Hz), 118.7.
2-(4-(Trifluoromethoxy)phenyl)quinoline (3aq). Light yellow
oil; 84% yield (243 mg); 1H NMR (500 MHz, CDCl3) d 8.25–8.15
(m, 4H), 7.85–7.83 (m, 2H), 7.76–7.73 (t, J = 7.7 Hz, 1H), 7.55 (t,
J = 7.5 Hz, 1H), 7.38 (d, J = 8.2 Hz, 2H); 13C{1H} NMR (125 MHz,
CDCl3) d 115.8, 150.2, 148.2, 138.3, 137.0, 129.9, 129.7, 129.1,
127.5, 127.2, 126.6, 121.6 (q, JC-F = 256.5 Hz), 121.1, 118.6. HRMS
(ESI) m/z calcd for C16H11F3NO+ (M + H)+ 290.07873, found
290.07880.
2-(4-Nitrophenyl)quinoline (3ar) [34]. Yellow solid; 82% yield
(205 mg); mp 134–135 °C; 1H NMR (500 MHz, CDCl3) d 8.38–8.34
(m, 4H), 8.31 (d, J = 8.6 Hz, 1H), 8.20 (d, J = 8.4 Hz, 1H), 7,93 (d,
J = 8.5 Hz, 1H), 7.88 (d, J = 8.1 Hz, 1H), 7.78 (t, J = 7.7 Hz, 1H),
7.59 (t, J = 7.5 Hz, 1H); 13C{1H} NMR (125 MHz, CDCl3) d 154.5,
148.3, 148.2, 145.4, 137.3, 130.2, 129.9, 128.2, 127.5, 127.3,
124.0, 118.7.
4-(Quinolin-2-yl)benzonitrile (3as) [35]. Yellow solid; 85%
yield (196 mg); mp 92–93 °C; 1H NMR (500 MHz, CDCl3) d 8.30–
8.27 (m, 3H), 8.18 (d, J = 8.4 Hz, 1H), 7.89 (t, J = 9.7 Hz, 2H), 7.82
(d, J = 8.4 Hz, 2H), 7.79–7.76 (m, 1H), 7.60–7.57 (m, 1H); 13C{1H}
NMR (125 MHz, CDCl3) d 154.9, 148.2, 143.7, 137.3, 132.6, 130.1,
129.9, 128.0, 127.6, 127.5, 127.1, 118.8, 118.6, 112.7.
2-([1,10-Biphenyl]-4-yl)quinoline (3at) [29]. White solid; 80%
yield (226 mg); mp 178–179 °C; 1H NMR (500 MHz, CDCl3) d
8.27–8.18 (m, 4H), 7.94 (d, J = 8.6 Hz, 1H), 7.85 (d, J = 8.0 Hz,
1H), 7.78–7.74 (m, 3H), 7.69 (d, J = 7.2 Hz, 2H), 7.54 (t, J = 7.1 Hz,
1H), 7.48 (t, J = 7.6 Hz, 2H), 7.38 (t, J = 7.3 Hz, 1H); 13C{1H} NMR
(125 MHz, CDCl3) d 156.9, 148.3, 142.1, 140.6, 138.5, 136.8,
129.7, 129.7, 128.8, 127.9, 127.5, 127.5, 127.2, 127.1, 126.3, 118.8.
2-(Pyrazin-2-yl)quinoline (3au) [36]. Light yellow solid; 76%
yield (158 mg); mp 156–157 °C; 1H NMR (500 MHz, CDCl3) d
9.88 (s, 1H), 8.66–8.64 (m, 2H), 8.50 (d, J = 8.6 Hz, 1H), 8.32 (d,
J = 8.6 Hz, 1H), 8.22 (d, J = 8.5 Hz, 1H), 7.88 (d, J = 8.1 Hz, 1H),
7.77 (t,
J =
7.7 Hz, 1H), 7.61–7.58 (m, 1H); 13C{1H} NMR
(125 MHz, CDCl3) d 154.1, 151.3, 147.9, 144.6, 144.1, 143.5,
137.1, 130.0, 129.9, 128.4, 127.6, 127.3, 118.7.
3-Methyl-2-phenylquinoline (3av) [29]. Light yellow oil; 77%
yield (169 mg); 1H NMR (500 MHz, CDCl3) d 8.14 (d, J = 8.5 Hz,
1H), 8.01 (s, 1H), 7.78 (d, J = 8.1 Hz, 1H), 7.66 (t, J = 7.7 Hz, 1H),
7.60–7.58 (m, 2H), 7.53–7.47 (m, 3H), 7.45–7.42 (m, 1H), 2.46 (s,
3H); 13C{1H} NMR (125 MHz, CDCl3) d 160.5, 146.6, 140.9, 136.7,
129.3, 129.2, 128.8, 128.7, 128.3, 128.1, 127.6, 126.7, 126.4, 20.6.
3-Ethyl-2-phenylquinoline (3aw) [29]. Light yellow oil; 82%
yield (192 mg); 1H NMR (500 MHz, CDCl3) d 8.14 (d, J = 8.5 Hz,
1H), 8.04 (s, 1H), 7.81 (d, J = 8.2 Hz, 1H), 7.66 (t, J = 7.7 Hz, 1H),
7.55–7.41 (m, 6H), 2.78 (q, J = 7.5 Hz, 2H), 1.19 (t, J = 7.5 Hz,
3H); 13C{1H} NMR (125 MHz, CDCl3) d 160.6, 146.3, 140.9, 135.2,
134.9, 129.2, 128.7, 128.7, 128.2, 128.0, 127.7, 126.7, 126.3, 26.0,
14.7.
5,6-Dihydrobenzo[c]acridine (3ax) [33]. White solid; 80% yield
(185 mg); mp 62–63 °C; 1H NMR (500 MHz, CDCl3) d 8.58 (d,
J = 7.6 Hz, 1H), 8.14 (d, J = 8.5 Hz, 1H), 7.92 (s, 1H), 7.75 (d,
J = 8.1 Hz, 1H), 7.64 (t, J = 7.7 Hz, 1H), 7.48–7.41 (m, 2H), 7.37 (t,
J = 7.4 Hz, 1H), 7.28 (d, J = 7.4 Hz, 1H), 3.13 (t, J = 7.0 Hz, 2H),
3.01 (t, J = 6.9 Hz, 2H); 13C{1H} NMR (125 MHz, CDCl3) d 153.4,
147.6, 139.4, 134.7, 133.6, 130.5, 129.6, 129.4, 128.6, 127.9,
127.8, 127.3, 126.9, 126.0, 28.8, 28.4.
2-Phenyl-1,2,3,4-tetrahydroquinoline Hydrochloride (4) [20].
Colorless oil, 71% yield (3.48 g); 1H NMR (500 MHz, CDCl3) d 7.40–
7.33 (m, 4H), 7.30–7.27 (m, 1H), 7.01 (t, 2H, J = 7.7 Hz), 6.65 (t,
J = 7.3 Hz, 1H), 6.55 (d, J = 7.9 Hz, 1H), 4.45 (dd, J = 9.3 and 3.0 Hz,
1H), 2.96–2.89 (m, 1H), 2.76–2.71 (m, 1H), 2.14–2.10 (m, 1H),
2.03–1.95 (m, 1H); 13C{1H} NMR (125 MHz, CDCl3) d 144.8, 144.7,
129.3, 128.5, 127.4, 126.9, 126.5, 120.8, 117.1, 113.9, 56.2, 31.0, 26.4.
1-Carboximidamido-2-phenyl-1,2,3,4-tetrahydroquinoline
Hydrochloride (5) [20]. White solid, 30% yield (1.04 g); mp 206–
207 °C; 1H NMR (500 MHz, CDCl3) d 7.39 (d, J = 7.4 Hz, 2H), 7.35
(t, J = 7.5 Hz, 2H), 7.28 (t, J = 7.2 Hz, 1H), 7.00 (t, 2H, J = 7.5 Hz),
6.65 (t, J = 7.4 Hz, 1H), 6.54 (d, J = 7.4 Hz, 1H), 4.45 (dd, J = 9.4
and 3.2 Hz, 1H), 2.95–2.89 (m, 1H), 2.76–2.71 (m, 1H), 2.13–2.09
(m, 1H), 2.03–1.95 (m, 1H); 13C{1H} NMR (125 MHz, CDCl3) d
144.8, 144.7, 129.3, 128.5, 127.4, 126.9, 126.5, 120.9, 117.6,
117.1, 113.9, 56.2, 30.9, 26.3.
2-Cyclopropylquinoline (3ay) [37]. Light yellow oil; 86% yield
(146 mg); 1H NMR (500 MHz, CDCl3) d 7.98–7.96 (m, 2H), 7.72
(d, J = 8.2 Hz, 1H), 7.62 (t, J = 7.7 Hz, 1H), 7.41 (t, J = 7.5 Hz, 1H),
7.13 (d, J = 8.5 Hz, 1H), 2.27–2.22 (m, 1H), 1.15–1.07 (m, 4H); 13C
4.5. Procedure for the hydrogen evolution experiment [44]
1a (1 mmol, 123 mg), 2a (145 mg, 1.2 mmol, 1.2 equiv), cat. 1
(6 mg, 0.01 mmol, 1 mol %), Cs2CO3 (165 mg, 0.5 mmol, 0.5 equiv)
346

X. Xu, Y. Ai, R. Wang et al.
Journal of Catalysis 395 (2021) 340–349
and tert-amyl alcohol (1 mL) were added to a 5 mL thick walled
glass vessel with a condenser tube, which was previously degassed
three times and placed under a N2 atmosphere. The vessel was con-
nected to the gas collection apparatus (standard water displace-
Acknowledgements
Financial support by National Natural Science Foundation of
China Jiangsu Province (BE2018051) and Postgraduate Research
& Practice Innovation Program of Jiangsu Province (KYCX20_0380)
is greatly appreciated.
ment apparatus, using
a graduated cylinder to determine
volume), and the entire system was flushed with N2 for 5 min
and allowed to equilibrate for 5 min. The reaction was stirred vig-
orously at 125 °C for 12 h. The presence of hydrogen in the col-
lected gas was confirmed by GC analysis.
Appendix A. Supplementary material
The GC analysis was performed on a gas chromatograph with
Supplementary data to this article can be found online at
https://doi.org/10.1016/j.jcat.2020.12.016.
TCD detector. Injector temperature
=
150 °C, column
temprature = 80 °C, detector temperature (TCD) = 80 °C, carrier
gas = N2, t = 0.558 min.
The volume of 1 mol of H2 at 299.15 K, 100,300 Pa was calcu-
lated according to the van der Waals equation as shown below
References
n2
[1] (a) J.P. Michael, Quinoline, quinazoline and acridone alkaloids, Nat. Prod. Rep
14 (1997) 605–618;
3
(p + a)(V-nb) = nRTwhere R = 8.3145 m ꢁPaꢁmolꢀ1ꢁKꢀ1
;
V2
T = 299.15 K; p = 100 300 Pa; a = 0.02476 Paꢁm6ꢁmolꢀ2; b = 0.026
61 ꢂ 10ꢀ3 m3ꢁmolꢀ1; thus, V (H2, 299.15 K, 100 300 Pa) = 24.8
(b) J.P. Michael, Quinoline, quinazoline and acridone alkaloids, Nat. Prod. Rep.
19 (2002) 742–1740.
[2] (a) M.A. Cinelli, C.T. Reidl, H.Y. Li, G. Chreifi, T.L. Poulos, R.B. Silverman, First
contact: 7-Phenyl-2-aminoquinolines, potent and selective neuronal nitric
oxide synthase inhibitors that target an isoform-specific aspartate, J. Med.
Chem. 63 (2020) 4528–4554;
Lꢁmolꢀ1
.
The collected volume of gas in this experiment above was
21.6 mL, which corresponds to 0.87 mmol of H2.
(b) Q. Xiao, H. Lin, J. Wu, X. Pang, Q. Zhou, Y. Jiang, P. Wang, W. Leung, H. Lee, S.
Jiang, S.Q. Yao, L. Gao, G. Liu, C.J. Xu, Pyridine-embedded phenothiazinium dyes
as lysosome-targeted photosensitizers for highly efficient photodynamic
antitumor therapy, Med. Chem. 63 (2020) 4896–4907;
4.6. Procedure for the gram-scale synthesis of 2-phenylquinoline (3aa)
In a round-bottomed flask with a condenser tube were added 1a
(3.08 g, 25 mmol) and 2a (3.61 g, 30 mmol, 1.2 equiv), cat. 1
(127 mg, 0.25 mmol, 1 mol %), Cs2CO3 (4.08 g, 12.5 mmol, 0.5
equiv) and tert-amyl alcohol (25 mL). The reaction mixture was
heated at 125 °C in an oil bath for 12 h and then cooled to ambient
temperature, concentrated in vacuo, and purified by flash column
chromatography with hexane/ethyl acetate (10:1, v/v) to afford
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Declaration of Competing Interest
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