Metal-Ligand Cooperative Approach to Achieve Dehydrogenative Functionalization of Alcohols to Quinolines and Quinazolin-4(3 H)-ones under Mild Aerobic Conditions

Article abstract of DOI:10.1021/acs.joc.9b01343

A simple metal-ligand cooperative approach for the dehydrogenative functionalization of alcohols to various substituted quinolines and quinazolin-4(3H)-ones under relatively mild reaction conditions (≤90 °C) is reported. Simple and easy-to-prepare air-stable Cu(II) complexes featuring redox-active azo-aromatic scaffolds, 2-arylazo-(1,10-phenanthroline) (L^1,2), are used as catalyst. A wide variety of substituted quinolines and quinazolin-4(3H)-ones were synthesized in moderate to good isolated yields via dehydrogenative coupling reactions of various inexpensive and easily available starting materials under aerobic conditions. A few control experiments and deuterium labeling studies were carried out to understand the mechanism of the dehydrogenative coupling reactions, which indicate that both copper and the coordinated azo-aromatic ligand participate in a cooperative manner during the catalytic cycle.

Full text of DOI:10.1021/acs.joc.9b01343

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Article
Metal-Ligand Cooperative Approach to Achieve
Dehydrogenative Functionalization of Alcohols to Quinolines
and Quinazolin-4(3H)-ones under Mild Aerobic Conditions
Siuli Das, Suman Sinha, Deepannita Samanta, Rakesh
Mondal, Gargi Chakraborty, Paula Brandão, and Nanda D. Paul
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.9b01343 • Publication Date (Web): 22 Jul 2019
Downloaded from pubs.acs.org on July 22, 2019
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Metal-Ligand Cooperative Approach to Achieve Dehydrogenative
Functionalization of Alcohols to Quinolines and Quinazolin-4(3H)-
ones under Mild Aerobic Conditions
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Siuli Das, Suman Sinha, Deepannita Samanta, Rakesh Mondal, Gargi Chakraborty, Paula
‡
,†
Brandaõ, and Nanda D. Paul*
†
Department of Chemistry, Indian Institute of Engineering Science and Technology, Shibpur,
Botanic Garden, Howrah 711103, West Bengal, India
§
Present Address: Department of Chemistry, Indian Institute of Technology, Kanpur, Kanpur-
2
08016, India
‡
Departamento de Química, CICECO-Instituto de Materiais de Aveiro,Universidade de Aveiro,
3
810-193 Aveiro, Portugal
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Abstract. A simple metal-ligand cooperative approach for the dehydrogenative functionalization
of alcohols to various substituted quinolines and quinazolin-4(3H)-ones under relatively mild
reaction conditions (≤90°C) is reported. Simple and easy to prepare air stable Cu(II)-complexes
1
,2
featuring redox-active azo-aromatic scaffolds, 2-arylazo-(1,10-phenanthroline) (L ) are used as
catalyst. Wide variety of substituted quinolines and quinazolin-4(3H)-ones were synthesized in
moderate to good isolated yields via dehydrogenative coupling reactions of various inexpensive
and easily available strarting materials under aerobic conditions. A few control experiments and
deuterium labelling studies were carried out to understand the mechanism of the dehydrogenative
coupling reactions which indicate that both copper and the coordinated azo-aromatic ligand
participate in a cooperative manner during the catalytic cycle.
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Introduction. Synthesis of nitrogen heterocycles has drawn considerable attention over the years
1
because of their presence in a wide spectrum of natural and synthetic organic molecules. Among
2
3
them quinolines and quinazolin-4(3H)-ones are common structural motifs found in a large
number of natural products and medicinally important compounds showing a broad range of
bioactivities (Figure 1). Therefore, development of green, atom-economic synthetic approaches
for the preparation of highly functionalized N-heterocycles such as quinolines and quinazolin-
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(3H)-ones from inexpensive and easily available starting materials under relatively mild
4
conditions is desirable.
N
Cl
N
O
N
H
N
N
O
O
N
N
O
N
F
N
H
N
Cl
H
Cl
F
F
Afloqualone
(Sedative, Anticancer,
Albaconazole
(Antifungal, Antibacterial)
Cloroqualone
(Sedative, Antitussive)
Anti-anxiety)
O
Cl
OCH3
O
O
O
N
I
N
N
OH
N
H
OH
H3CO
N
OCH3
H2N
Clioquinol
Robustine
(Anticancer)
Berberine
Anticancer)
(Antifungal,
Primaquine
(Antimalarial)
(
Antiprotozoal)
Figure 1. Selected examples of drugs containing quinoline and quinazolin-4(3H)-one moieties.
In recent times, the dehydrogenative functionalization of alcohols has emerged as an
attractive atom economic and green synthetic route for the benign synthesis of various
5
functionalized organic moleules including N-heterocycles. In the last one decade, a
significant progress have been achieved in designing new catalysts and synthetic
strategies to attain efficient dehydrogenative functionalization of cheap and eco-friendly
6-16
alcohols to numerous valuable products including N-heterocycles.
The groups of
6
7
8a
9a
10
Crabtree, Beller, Kempe, Milstein, and Saito independently reported Ru or Ir-
9
b
8b
11
catalyzed synthesis of pyrroles. Milstein, Kempe, Liu and Sun, and co-workers
reported Ir- and Ru-catalysed dehydrogenative synthesis of pyridines. Recently,
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pyrimidines were also synthesized following the same dehydrogenative coupling
8c
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approach. Dehydrogenative synthesis of quinolines were achieved by Shim, Yus,
14
9b
11
Verpoort, Milstein, Liu and Sun via a Ru-catalyzed indirect Friedlander synthesis.
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The groups of Zhou, Li and some others developed the synthesis of quinazolin-4(3H)-
ones via Ru and Ir-catalyzed dehydrogenative coupling of 2-aminobenzamides and
alcohols. Recently, Li and Lang reported Ru-catalyzed dehydrogenative synthesis of
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benzimidazoles and benzoxazoles.
Despite, achieving tremendous advances on N-heterocycle synthesis via the
straightforward dehydrogenative functionalization of alcohols, the catalyst mostly used
6-17
are toxic and precious noble metals like Ru, Rh, and Ir.
Therefore, to make the
dehydrogenative functionalization of alcohols more environment friendly and
economically affordable these precious heavy metals ought to be replaced by non-
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22
precious, earth-abundant metals like Mn, Fe, Co, Cu, and Ni. However, these
metals tend to react by one electron pathway and the corresponding two electron redox
events are mostly associated with high energy barrier and hence elevated temperature is
2
3
almost always required.
23
In this regard, the cooperative catalysis, involving synergistic participation of both
metal and ligands, offers an attractive alternative to achieve chemical transformations
which are usually difficult to attain using first-row base metals under relatively mild
conditions. Herein we report a simple copper catalyzed metal-ligand cooperative
approach for dehydrogenative functionalization of alcohols to various substituted
quinolines and quinazolin-4(3H)-ones under relatively mild aerial conditions. Well
defined, air-stable and affordable copper(II)-complexes (1a
,b, 2a,b) of tridentate azo-
aromatic ligands, 2-arylazo(1,10-phenanthroline) are used as catalysts. Azo-
24,25
chromophores are redox active and known to participate as an electron sink
during
dehydrogenation of alcohols. We envisioned that copper and the azo-aromatic scaffold
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will participate in a synergistic manner and will allow us to carry out these
dehydrogenative functionalization reactions under mild conditions (≤90°C).
Results and Discussion. Four Cu(II)-complexes, dichloro-(E)-2-(phenyldiazenyl)-1,10-
phenanthroline-Cu(II) (1a), dibromo-(E)-2-(phenyldiazenyl)-1,10-phenanthroline-Cu(II) (1b),
dichloro-(E)-2-((4-chlorophenyl)diazenyl)-1,10-phenanthroline-Cu(II) (2a) and dibromo-(E)-2-
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(
(4-chlorophenyl)diazenyl)-1,10-phenanthroline-Cu(II) (2b) of the tridentate azo-aromatic pincer,
1
,2
2-arylazo-1,10-phenanthroline (L ) were synthesized via stirring an equimolar mixture of CuX
2
1,2
(X = Cl, Br) and L in ethanol for four hours under air (Scheme 1). Characterization of the
isolated complexes using available spectroscopic techniques including X-ray single crystal
diffraction (of 2b) reveals penta-coordinate geometry around the Cu(II)-center with the
II
molecular formula of [Cu LX
2
] (Scheme 1). X-ray structure of 2b, unveils that two N-donor
atoms N1(phen) and N4(azo) occupy the apical positions with a N1−Cu−N4 angle of
50.33(16)°. The N-N bond distance was found to be 1.264(6)Å indicating the presence of
1
2
4
unreduced azo-chromophore. The room temperature magnetic moment of these complexes are
further in agreement with the Cu(II)-oxidation state.
N
N
N
N
X
II
CuX2
EtOH
+
CuII
N
N
Stir, 4h
N
N
X
1
a,b (R=H, X = Cl,Br)
2
a,b (R=Cl, X = Cl,Br)
eff = 1.74 B (1a)
eff = 1.75 B (2a)
R
R
Scheme 1. Synthesis of Cu(II)-complexes and crystal structure of 2b
.
Upon electrochemical analysis using Cyclic Voltammetry, the complexes 1a
,b and
2
a
,
b
exhibited ligand centered irreversible one-electron reductions in CH CN at the
3
potential range of -0.22 - -0.26V (See SI). The irreversibility may be due to the loss of a
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chlorido (in case of complex 1a, 2a) or bromido (in case of complex 1b, 2b) ligand upon
reduction.
Electronic structure elucidation using DFT at B3LYP level revealed that the complex,
2a
[
2
Cu(L )Cl ] (2a), is an open shell doublet species with a spin population of 0.51 on the
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Cu(II)-center and 0.10 spin population on the azo-aromatic scaffold (Figure 2). Molecular
orbital analysis showed that the LUMOs are ligand centered; primarily localized on the
azo-chromophore (see SI). This is indicative of the fact that the redox active azo-
chromophore can act as an electron sink during the catalytic cycle.
Figure 2. Spin density plot of 2a.
Intrigued by the characterization data, we began our study to synthesize quinolines
via dehydrogenative coupling of primary alcohols with ketones using the complex 2a as
the catalyst. Initially, 2-aminobenzyl alcohol (3a) was reacted with acetophenone (4a
)
under various reaction conditions to find out the optimal reaction conditions for the
synthesis of 2-phenylquinoline (5aa). Under aerial conditions, highest yield, 96% of 5aa
was obtained in toluene at 85°C with 1.0 mol% catalyst loading and 0.5 equiv. NaOH
after 18h. Increasing the catalyst or base loading beyond the optimized condition does not
improve the yield, however, upon lowering the yield decreases.
To further explore the potential of our catalyst, the possibility of dehydrogenative
functionalization of alcohols to quinazolin-4(3H)-ones was also explored. To our delight,
under the pre-optimized conditions (Table 1, entry 3), the dehydrogenative coupling of
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-aminobenzamide (6a) and benzylalcohol (7a) proceeds smoothly affording 66% of
2-phenylquinazolin-4(3H)-one (8aa). Slight modification of the reaction conditions by
increasing the catalyst loading to 5.0 mol% and increasing the temperature to 90°C
yielded the highest yield (95%) of 8aa in 36h (Table 1, entry 12).
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Other Cu(II)-salts, such as CuCl
2
.2H
2
O and anhydrous CuBr were found to be less
2
effective/ineffective and yielded only a small amount of the desired products (Table 1,
entries 17, 18). Very small or trace amount of the desired products were obtained in
absence of the catalyst or base (Table 1, entries 19, 20). In presence of only NaOH, 5aa
and 8aa were obtained in 19 and 16% and in presence of ligand and NaOH 5aa and 8aa
were obtained in 22 and 18% respectively (Table 1, entries 20, 21). Even a 1:1 mixture of
2
CuCl
2
.2H
2
O and
L
was also found to be less effective than the pre-formed catalyst 2a
,
affording 5aa and 8aa in 44 and 63% yields respectively (Table 1, entry 22). Reaction did
not peoceed in absence of oxygen, under inert atmosphere 5aa and 8aa were obtained in
trace amounts. However, under positive oxygen pressure we did not observe any
noticeable change in yields of 5aa and 8aa
.
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6
a-c
Table 1. Optimization of the Reaction Conditions.
O
O
O
N
CH3
NH2
NH
OH
NH2
N
Catalyst, Base,
Solvent, Temp.,
R
Catalyst, Base,
Solvent, Temp.,
36h, air
5
aa
8aa
R= NH for 5aa
R= H for 8aa
18h, air
2
0
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b
Entry
Catalyst
mol%)
Solvent
Base
Temp
Yield (%)
(5aa)
80
92
96
30
90
94
95
trace
NR
70
95
95
94
93
90
88
(
(°C)
40
60
85
85
85
85
85
85
85
85
85
90
90
90
90
90
90
(8aa)
56
63
66
35
55
63
64
trace
trace
54
65
95
94
91
88
85
1
2
3
4
5
6
7
8
9
2a (5.0 mol%)
2a (3.0 mol%)
2a (1.0 mol%)
2a (1.0 mol%)
2a (1.0 mol%)
2a (1.0 mol%)
2a (1.0 mol%)
2a (1.0 mol%)
2a (1.0 mol%)
2a (1.0 mol%)
2a (1.0 mol%)
2a (5.0 mol%)
2a (5.0 mol%)
2b (5.0 mol%)
1a (5.0 mol%)
1b (5.0 mol%)
Toluene
Toluene
Toluene
Toluene
Toluene
NaOH (1.0 equiv.)
NaOH (0.5 equiv.)
NaOH (0.5 equiv.)
K
3
PO
4
(0.5 equiv.)
KOH (0.5 equiv.)
t
Toluene NaO Bu (0.5 equiv.)
t
Toluene
ACN
Ethanol
THF
Xylene
Toluene
Xylene
Toluene
Toluene
Toluene
Toluene
KO Bu (0.5 equiv.)
NaOH (0.5 equiv.)
NaOH (0.5 equiv.)
NaOH (0.5 equiv.)
NaOH (0.5 equiv.)
NaOH (0.7 equiv.)
NaOH (0.7 equiv.)
NaOH (0.7 equiv.)
NaOH (0.7 equiv.)
NaOH (0.7 equiv.)
NaOH (1.0 equiv.)
10
11
12
13
14
15
16
17
CuCl
5.0 mol%)
CuBr
2
.2H
2
O
35
21
(
18
19
2
Toluene
NaOH (1.0 equiv.)
90
33
20
(5.0 mol%)
-
Toluene
Toluene
NaOH (0.7 equiv.)
-
NaOH (1.0 equiv.)
NaOH (1.0 equiv.)
90
90
90
90
22
trace
19
18
trace
16
20
21
22
2a (5.0 mol%)
1
,2
L
(5.0 mol%) Toluene
2
CuCl
2
+L (1:1) Toluene
44
63
(
5.0 mol%)
c
2
3
2a (5.0 mol%)
Toluene
NaOH (0.7 equiv.)
90
trace
trace
a
Stoichiometry: for quinoline: acetophenone (1.10 mmole); 2-aminobenzyl alcohol (1.0
mmole); for quinazolinone: 2-aminobenzamide (1.0 mmol); benzyl alcohol (1.10 mmol).
b
c
Isolated yields after column chromatography. inert condition.
Having obtained the optimal conditions, we studied the substrate scope and the
versatility of the dehydrogenative coupling reactions catalyzed by 2a. Since catalyst 2a
was found to be more efficient compared to the others (Table 1, entries 14-16), substrate
screening was carried out with the former. The catalyst was well tolerant towards a wide
variety of substituted ketones (in case of quinolines) and substituted benzylalcohols (in
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case of quinazolin-4(3H)-ones) bearing electron -donating, -withdrawing, heteroaryl
functionalities under the optimized reaction conditions (Table 2 and Table 3).
Table 2. Dehydrogenative Coupling of Various Acetophenones with Various 2-
a-c
Aminobenzyl Alcohols.
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
O
OH
CH3
2a (1.0 mol%)
+
N
+
R
H O
2
2 +
2
H O
Toluene, NaOH
NH2
(3a-c)
R
R
0
8
5 C, 18h
(4a- u)
(
5aa- 5au,5ba,5ca)
R
R
N
N
N
N
N
R
1) 96%(R=H, 5aa)
10) 71% (R=Me, 5aj)
11) 62% (R=OMe, 5ak)
12) 40% (R=F, 5al)
1
4) 55% (R=Br, 5an)
16) 74% (5ap)
2) 95%(R=Me, 5ab)
15) 69% (R=NO2, 5ao)
3) 81%(R=OMe, 5ac)
4) 75% (R=NH2, 5ad)
5) 60% (R=F, 5ae)
6) 93% (R=Cl, 5af)
13) 58% (R=Cl, 5am)
7) 96% (R=Br, 5ag)
8
) 85% (R=NO2, 5ah)
9) 66% (R=CF3, 5ai)
N
N
N
S
S
17) 80% (5aq)
18) 64% (5ar)
19) 79%(5as)
Me
N
N
Cl
N
N
Br
20) 78%(5at)
21) 81% (5au)
22) 67% (5ba)
23) 71% (5ca)
a
b
Stoichiometry: acetophenone (1.1 mmol); 2-aminobenzyl alcohol (1.0 mmol); NaOH (0.5 equiv).
Isolated yields after column chromatography. aerial condition.
c
For example, acetophenones or benzylalcohols having electron donating -Me group at
para- position produced the corresponding quinolines and quinazolin-4(3H)-ones in 95%
isolated yields (Table 2, entry 2, and Table 3, entry 2). Strong electron withdrawing
2 3
groups like NO , CF were also found to be compatible affording the respective
quinolines (Table 2, entries 8, 9) and quinazolin-4(3H)-ones (Table 3, entries 7, 8) in
moderate to good yields. Reactions also proceed smoothly with heteroaryl alcohols (Table
2, entries 16, 18, 19 and Table 3, entries 19, 20). Long chain aliphatic alcohol also yielded
the corresponding quinazolin-4(3H)-one, however in much lower yield and after a slightly
long reaction time (Table 3, entry 21).
To further supplement the substrate scope, various substituted 2-aminobenzylalcohols (3b,
3
c) and 2-aminobenzamides (6b-f) were reacted separately under the optimized conditions. To
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1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
our pleasure, both electron donating and -withdrawing substitution on 2-aminobenzylalcohol and
2-aminobenzamides resulted in considerable high yield of quinolines (5ba, 5ca) (67%-71%) and
quinazolin-4(3H)-ones (8ba-8fa, 8eb) (65-95%) respectively (Table 2, 4).
a-c
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Table 3. Dehydrogenative Coupling of Various Benzylalcohols with 2-Aminobenzamide.
O
O
NH2
OH
NH
2
a (5.0 mol%)
+
2 2 2
+ 2H O + H O
NH2
Toluene, NaOH
N
R
o
9
0
C, 36h
(
6a)
(7a-u)
(8aa-8au)
NH
O
O
O
N
O
N
NH
NH
R
NH
R
R
N
N
R
R
1) 95%(R=H, 8aa)
) 95%(R=Me, 8ab)
) 77%(R=OMe, 8ac)
4) 83%(R=F, 8ad)
) 82%(R=Cl, 8ae)
) 80%(R=Br, 8af)
7) 52%(R=NO2, 8ag)
) 92%(R=CF3, 8ah)
10) 64%(R=Me, 8aj)
11) 55%(R=Cl, 8ak)
12) 52%(R=Br, 8al)
13) 95%(R=Me, 8am)
4) 93%(R=OMe, 8an)
17) 95%(R=OMe, 8aq)
18) 62%(R=Cl, 8ar)
1
2
3
15) 69%(R=Cl, 8ao)
1
6) 65%(R=Br, 8ap)
O
O
5
6
O
NH
NH
NH
N
N
S
8
N
N
t
9) 94%(R= Bu, 8ai)
19) 56%(8as)
20) 68%(8at)
21) 35%(8au)
a
b
Stoichiometry: 2-aminobenzamide (1.0 mmol); benzyl alcohol (1.1 mmol); NaOH (0.7equiv).
Isolated yields after column chromatography. aerial condition.
c
Table 4. Dehydrogenative Coupling of Various 2-Aminobenzamides with Various Benzyl
a-c
Alcohols.
O
O
N
NH2
OH
NH
2a (5.0 mol%)
+
+
2 2
2
2H O + H O
NH2
Toluene, NaOH
R
R
R
o
9
0 , 36h
(
6b- f)
(7a,b)
(
8ba- 8fa,8eb)
O
O
O
Me
Me
NH
NH
NH
N
N
N
R
Br
R
1
) 95%(R=Me, 8ba)
3) 94%(8da)
4) 71%(R=H, 8ea)
5) 75%(R=Me, 8eb)
2) 68%(R=Br, 8ca)
O
MeO
MeO
NH
N
OMe
6) 96%(8fa)
a
b
Stoichiometry: 2-aminobenzamide (1.0 mmol); benzyl alcohol (1.1 mmol); NaOH (0.7 equiv).
Isolated yields after column chromatography. aerial condition.
c
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To further investigate the synthetic potential of our catalyst 2a we performed "gram"-scale
reaction of 3a with 4a and to our pleasure obtained 5aa in 88% yield. 8aa was also obtained in
58% yield upon "gram"-scale reaction of 3a and 4a (Scheme 2).
O
OH
CH3
2a (1.0 mol%)
+
NaOH (0.5 equiv.)
Toluene, 85°C
18h, aerial condition
NH2
a, 1.0g
N
3
4a
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
(8.1 mmol)
9.7 mmole
5aa, 1.5g
8% yield
8
O
O
OH
NH2
NH2
NH
N
2
a (5.0 mol%)
+
NaOH (0.7 equiv.)
Toluene, 90°C
36h, aerial condition
7
a
6a, 1.0g
(7.3 mmol)
8
aa, 0.9g
58% yield
8
.8 mmol
Scheme 2. Gram-Scale synthesis of 5aa and 8aa.
Finally to unveil the reaction mechanism a series of control experiments were performed.
Firstly, to check the purity of catalyst 2a, inductively coupled plasma optical emission
spectrometry (ICP-OES) was performed. Only 0.16 ppb of palladium and 1.8 ppb of iron was
detected as trace metal impurities. No cobalt or nickel was detected. On carrying out the
synthesis of 2-phenylquinoline (5aa) and 2-phenylquinazolin-4(3H)-one (8aa) with 100 ppb of
palladium and copper seperately under the optimized conditions, 5aa and 8aa was obtained in 20
and 16% yields respectively, which is quite close to that obtained in presence of only NaOH.
This experimental data clearly demonstrates that the complex 2a plays an active role in the
catalysis.
Since, our catalysts 1 or 2 undergoes ligand centered reduction and can produce azo-anion
2
4,25
radical,
yl)oxyl). Contrary to our previous results, in presence of TEMPO, the yields of benzaldehyde
dehydrogenated product of benzylalcohol), 5aa, and 8aa remain almost unaltered indicating the
reactions were performed in presence of TEMPO ((2,2,6,6-Tetramethylpiperidin-1-
2
4c
(
non-involvement of any organic radicals during the present Cu-catalyzed dehydrogenation
reactions.
-
-
Next to check the feasibility of 1e hydrogen atom transfer (HAT) vs. 2e hydride transfer
pathway (involving a transient copper-hydride intermediate) the dehydrogenation of
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1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
cyclobutanol(radical clock substrate) was performed under the optimized conditions using 2a as
the catalyst. Formation of cyclobutanone as the dehydrogenated product indeed points to the
-
involvement of the 2e -hydride transfer process and rules out the possibility of HAT process
involving ketyl radical intermediate as was also supported by the results obtained in presence of
TEMPO (see SI).
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Azo-aromatic ligands, even if does not form radical, can also act as an electron sink during a
2
4
chemical reaction involving its azo/hydrazo redox couple. Therefore, to investigate the
possibility of the involvement of the azo-chromophore, 1-phenylethanol (10a) and deuterated 1-
phenylethanol (D
2
-10a) were subjected to dehydrogenation stoichiometrically under the
optimized conditions in presence of argon. IR spectroscopic data of the reaction mixtures exhibit
-1
-1
N-H stretching at 3029 and 3063 cm and N-D stretching at 2079 and 2121 cm indicating the
active involvement of the coordinated azo-aromatic scaffold during dehydrogenation of 10a and
2
4
D
2
-10a respectively (See SI).
Next, to check whether H
2
evolution occurs during alcohol dehydrogenation,
intermolecular hydrogen transfer reactions were carried out in a closed system using 4-
methoxybenzaldehyde (11a) and 2,4- dimethoxybenzaldehyde (11b) (Scheme 3).
Maintaining a closed system under both inert and aerobic conditions when
dehydrogenation of 1-phenylethanol (10a) was carried out separately in presence of 11a
and 11b, no hydrogenated products of the aldehydes (11a or 11b) were obtained as shown
2 2
in Scheme 3. On the other hand, H O was detected spectrophotometrically under aerobic
24c
conditions (See Figure S4 in SI).
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OH
H
O
H
inert
O
condition
+
+
R3
R1
H
R3
R1
H
O
R2
H
R2
unreacted
trace amount (4a)
O
Not Observed
R2= OMe, R1=R3= H)
(R1=R3= OMe, R2= H)
2
a (5.0 mol%)
(
+
(R2= OMe, R1=R3= H, 11a)
(R =R = OMe, R = H, 11b)
R3
R1 Toluene, NaOH
1
3
2
o
85 C, 18h
O
OH
R2
H
(10a)
(R = OMe, R =R = H, 11a)
2 1 3
R1=R3= OMe, R2= H, 11b)
O
H
(
aerial
condition
+
+
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
R3
R1
R3
R1
9
3% (4a)
R2
unreacted
R2= OMe, R1=R3= H, 11a)
R1=R3= OMe, R2= H, 11b)
R2
Not Observed
(R2= OMe, R1=R3= H)
(R1=R3= OMe, R2= H)
(
(
OH
D
H
O
inert
condition
O
+
+
R3
R1
R3
R1
H
O
D
R2
O
R2
unreacted
R2= OMe, R1=R3= H, 11a)
D
trace amount (4a)
O
Not Observed
(R2= OMe, R1=R3= H)
(R1=R3= OMe, R2= H)
2
a (5.0 mol%)
(
+
R3
R1 Toluene, NaOH
(R =R = OMe, R = H, 11b)
1
3
2
o
85 C, 18h
OH
D
R2
H
(
D2-10a)
(R2= OMe, R1=R3= H, 11a)
R1=R3= OMe, R2= H, 11b)
O
(
aerial
condition
+
+
R3
R1
R3
R1
9
3% (4a)
R2
unreacted
R = OMe, R =R = H, 11a)
R2
Not Observed
(R2= OMe, R1=R3= H)
(
(
2
1
3
(
R =R = OMe, R = H)
R1=R3= OMe, R2= H, 11b)
1 3 2
Scheme 3. Hydrogen transfer reactions.
A plausible mechanism for the present Cu-catalysed dehydrogenative synthesis of
quinoline and quinazolin-4(3H)-ones via the dehydrogenative coupling of benzyl alcohols
with ketones and 2-aminobenzamide respectively, is shown in Scheme 5. The reaction is
believed to begin with the deprotonation of the primary alcohols followed by formation of
the copper-alkoxy intermediate (
corresponding aldehydes.
B) which then undergoes dehydrogenation to produce the
The dehydrogenation of alcohols from intermediate
A, can proceed via hydride
transfer to the copper center followed by hydrogen atom walking to the azo-
2
5
chromophore or direct hydride transfer to the azo-chromophore of the coordinated azo-
aromatic ligands to form the intermediate . The intermediate , upon protonation, forms
the intermediate which further coordinates with second molecule of alcohol forming
B
B
C
2 2
the dihydrazo intermediate D. D upon reaction with molecular oxygen forms H O and
1
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1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
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4
4
4
4
4
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5
5
5
5
5
5
5
5
5
6
transforms back to
A
. The aldehydes, thus generated undergo NaOH mediated cross aldol
condensation with ketones to form the intermediate
produce quinoline via cyclodehydration reaction.
E
which in the subsequent steps
O
O
NH
H
NH
N
2
a (5.0 mol%)
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
N
Toluene, NaOH
H
o
9
0 C, 24 h
9aa
96% (8aa)
Scheme 4. Dehydrogenation of 2,3-dihydro-2-phenylquinazolin-4(1H)-one.
On the other hand, condensation of the in-situ formed aldehydes with 2-
aminobenzamide produce the cyclic aminal 9aa which then undergoes further
dehydrogenation to afford quinazolin-4(3H)-one. Notably, the preformed cyclic aminal
2
,3-dihydro-2-phenylquinazolin-4(1H)-one (9aa), when subjected to dehydrogenation
under optimized reaction conditions for 24 hours afforded 8aa in 96% yield (Scheme 4).
N
N
II
N
Cu
N
O2
H2O2
X
X
O2
H2O2
Catalyst
R
N
N
N
X
N
N
X
N
II
Cu
II
Cu
II
Cu
N
N
N
NH
NH
N
II
NH
NH
Cu
N
N
X
O
X
O
N
N
(A)
Base
Ar
Ar
(
D)
O
NH
NH
Ar
R
R
(F)
R
Ar
R
NH2
NH2
O
O
(I)
O
O
O
N
H2O
NH
ArCH2OH
NH
N
H
ArCHO
Quinazolin-4(3H)one
O
N
N
N
N
II
Cu
N
N
N
II
N
N
II
Cu
N
N
II
Cu
NH2
O
Cu
N
NH
(
C)
NH
CH3
X
N
X
N
X
H
X
H
(H)
(G)
(
B)
O
NH2
R
R
R
R
1
a,b (R=H, X = Cl,Br)
N
2a,b (R=Cl, X = Cl,Br)
(E)
Quinoline
Scheme 5. Plausible mechanism for the dehydrogenative functionalization of alcohols to
quinolines and quinazolin-4(3H)ones catalyzed by 2.
Conclusion. In summary we have developed a simple and straightforward approach of
dehydrogenative functionalization of environmentally benign alcohols to various substituted
quinolines and quinazolin-4(3H)-ones under relatively mild (≤90°C) aerobic conditions using an
1
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earth abundant and affordable copper complex of a tridentate azo-aromatic scaffold as catalyst.
Variety of substituted quinolines and quinazolin-4(3H)-ones were synthesized in moderate to
good isolated yields starting form various inexpensive and easily available starting precursors.
Control experiments and mechanistic investigation indicate synergistic participation of both
copper and azo-aryl ligand during this dehydrogenative coupling reactions which possibly
allowed us to achieve these reactions under comparatively mild conditions (≤90°C). Our present
result would possibly open up several other new aspects of metal-ligand cooperativity during
catalysis which will probably enable us to achieve various other new chemical transformations
using cheap and earth abundant base metal catalysts under relatively mild reaction conditions.
Our work in this area is in progress and will be reported in due course.
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Experimental Section.
General Information. Tetrahydrofuran(THF), xylene and toluene used in the reactions were
refluxed and distilled over sodium/benzophenone maintaining an argon atmosphere and stored
over 4 Å molecular sieves. All the other chemicals were purchased from commercial suppliers
and were used without further purification. Merck 60 F254 silicagel plate (0.25 mm thickness)
was used for performing analytical TLC and Merck 60 silica gel (60−120 mesh) was used for
1
column chromatography. H NMR spectra were recorded on Bruker DPX-300 (300 MHz),
Bruker DPX-400 (400 MHz), and Bruker DPX-500 (500 MHz) spectrometers. For collecting
microanalytical data (C, H, N), a Perkin Elmer 240C elemental analyzer was used. Jobin-Yvon
ULTIMA 2 ICP optical emission spectrometer was used to carry out ICP-OES analysis.
Synthesis of Catalyst dichloro-(E)-2-(phenyldiazenyl)-1,10-phenanthroline-Cu(II) complex
1
(
1a). In a 100 mL round bottom flask, 100 mg (0.314 mmol) of the ligand, L was allowed to
dissolve in ethanol and 53.5 mg (0.314 mmol) of CuCl
2
.2H O was added to it. Color of the
2
resultant solution immediately changes from orange to deep red. Upon stirring the reaction
mixture for four hours in a magnetic stirrer a red color precipitate was formed. The precipitate
1
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2
2
2
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5
5
5
5
5
5
5
5
5
6
was isolated by filtration of the reaction mixture and was purified by fractional crystallization
with methanol/diethyl ether solvent mixture. Its yield and characterization data are as follows:
-
1
-1
-1
Yield 92%. UV/Vis : λmax/nm (ε, M cm ), 329(11,708), 385(10,987). IR (KBr cm ): 1638 (ν,
C=N), 1352 (ν, N=N). μeff (RT): 1.74 µ . Elemental Analysis: C18 CuN : calcd: C, 51.63; H,
.89; N, 13.38. Found: C, 51.54; H, 3.01; N, 13.45%.
B
H
12Cl
2
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2
Synthesis of Catalyst dibromo-(E)-2-(phenyldiazenyl)-1,10-phenanthroline-Cu(II) complex
1
(1b). In a 100 mL round bottom flask, 100 mg (0.352 mmol) of the ligand, L was allowed to
2
dissolve in ethanol. Then on addition of 78.6 mg (0.352 mmol) of anhydrous CuBr the colour of
the solution immediately changes from orange to deep red. Upon stirring the reaction mixture for
four hours in a magnetic stirrer a red color precipitate was formed. The precipitate was isolated
by filtration of the reaction mixture and was purified by fractional crystallization with
methanol/diethyl ether solvent mixture. Its yield and characterization data are as follows: Yield
-1
-1
-1
89%. UV/Vis : λmax/nm (ε, M cm ), 323(15,288), 387(14,222). IR (KBr cm ): 1620 (ν, C=N),
1347 (ν, N=N). C18 CuN : calcd: C, 42.59; H, 2.38; N, 11.04. Found: C, 42.51; H, 2.48; N,
1.10%.
H12Br
2
4
1
Synthesis of Catalyst dichloro-(E)-2-((4-chlorophenyl)diazenyl)-1,10-phenanthroline-Cu(II)
complex (2a).Catalyst 2a was prepared following the same procedure as catalyst 1a. Its yield
-
1
-1
and characterization data are as follows: Yield 92%. UV/Vis : λmax/nm (ε, M cm ), 334(15,900),
-
1
389(19,100). IR (KBr cm ): 1623 (ν, C=N), 1345 (ν, N=N). μeff(RT): 1.75 µ
Analysis: C18 CuN : calcd: C, 47.70; H, 2.45; N, 12.36. Found: C, 47.61; H, 2.55; N,
2.48%.
B
. Elemental
H
11Cl
3
4
1
Synthesis of Catalyst dibromo-(E)-2-((4-chlorophenyl)diazenyl)-1,10-phenanthroline-
Cu(II) complex (2b). Catalyst 2b was prepared following the same procedure as catalyst 1b. Its
-1
-1
yield and characterization data are as follows: Yield 90%. UV/Vis : λmax/nm (ε, M cm ),
-1
3
30(19,893), 390(23,095). IR (KBr cm ): 1609 (ν, C=N), 1340 (ν, N=N). Elemental Analysis:
C
18
H11Br
2
ClCuN
4
: calcd: C, 39.88; H, 2.05; N, 10.33. Found: C, 39.79; H, 2.14; N, 10.39%.
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Procedure for Dehydrogenative Coupling of 2-Aminobenzylalcohols and Acetophenones.
Under aerial condition a mixture of catalyst 2a (1.0 mol%), NaOH (0.5 equiv.), acetophenone
(
1.10 mmol) and 2-aminobenzylalcohol (1.0 mmol) were added to a 50.0 mL round bottom flask.
Then 5.0 mL of toluene was added to it and the round bottom flask containing the reaction
mixture was placed in an oil bath pre-heated at 85°C. The reaction was continued for 18h. After
the reaction was completed, the resulting mixture was concentrated under vacuum and purified
by column chromatography (silica gel). Eluent: petroleum ether/ethyl acetate (18 : 1)
1
1
1
1
1
1
1
1
1
1
2
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Procedure for Dehydrogenative Coupling of Alcohols and 2-Aminobenzamides. A mixture
of catalyst 2a (4.0 mol%), NaOH (0.7 equiv.), alcohol (1.10 mmol) and 2-aminobenzamide (1.0
mmol) were added to a 50.0 mL round bottom flask. Then 5.0 mL of toluene was added to it and
the round bottom flask containing the reaction mixture was placed in an oil bath pre-heated at
90°C. The reaction was continued for 36 h. After the reaction was completed, the resulting
mixture was concentrated under vacuum and purified by flash column chromatography (silica
gel). Eluent: petroleum ether/ethyl acetate (3:1).
Transfer Hydrogenation Reactions.
Under Inert Conditions. To an oven dried schlenk tube, 1-phenylethanol (10a) (1.0 mmol),
4
-methoxybenzaldehyde (11a) (1.0 mmol) or 2,4-dimethoxybenzaldehyde (11b)(1.0 mmol) and
NaOH (0.5 equiv.) were added under an argon atmosphere. Then the schlenk tube was evacuated,
backfilled with argon, 3.0 mL of degassed toluene was added and sealed with a teflon screw cap.
The reaction mixture was stirred in an oil bath at 85°C for 18h. After this the resultant mixture
was concentrated and purified by column chromatography. Eluent: petroleum
ether/dichloromethane (4:1). The dehydrogenated product of 1-phenylethanol was isolated in
trace amount while no transfer hydrogenation was observed.
Under Aerial Conditions. Under air, to an oven dried schlenk tube, 1-phenylethanol (10a)(1.0
mmol),4-methoxybenzaldehyde (11a) (1.0 mmol) or 2,4-dimethoxybenzaldehyde (11b) (1.0
mmol) and NaOH (0.5 equiv.) were added. Then 3.0 mL of toluene was added and the schlenk
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tube was sealed with a teflon screw cap. The reaction mixture was stirred in an oil bath at 85°C
for 18h. After this the resultant mixture was concentrated and purified by column
chromatography. Eluent: petroleum ether/dichloromethane (4:1). The dehydrogenated product of
1
-phenylethanol was isolated in 93% yield. In this case also no hydrogenated products of 11a or
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11b were obtained.
The same procedure as above was repeated with D
2
-10a and same result as above was obtained.
2
3c
Detection of Hydrogen Peroxide during the Catalytic Reactions. During catalytic alcohol
oxidation reactions, production of H
2
O
2
was detected spectrophotometrically monitoring the
−
gradual development of the characteristic absorption band for I
3
at 350 nm. 1-phenylethanol
t
(
1.0 mmol), KO Bu (0.1 mmol) and 3.0 mol% of catalyst 2a in 5.0 mL of dry toluene was added
in a 50 ml round bottom flask containing a stir bar and heated to 70°C for 4 h. 5.0 mL of distilled
water was added to the reaction mixture, and the resultant solution was extracted three times
with dichloromethane. To stop further oxidation of the alcohol, the separated aqueous layer thus
obtained was then acidified with H
2
SO to pH 2. A 10% KI solution and a few drops of 3%
4
ammonium molybdate solution were then added to it. The hydrogen peroxide produced during
−
−
−
the catalytic cycle oxidises I to I
2
, which reacts with excess I to form I
3
according to the
−
+
−
−
following chemical reactions: (i) H
2
O
2
+ 2I + 2H → 2H
2
O + I
2
; (ii) I
2
(aq) + I → I
3
.
X-Ray Crystallography. We successfully obtained good quality single crystals, suitable for X-
ray diffraction, of 2b via slow evaporation of its methanol−diethyl ether solvent mixture. Single-
crystal X-ray diffraction data of 2b were collected with monochromated Mo Kα radiation (λ =
0.71073 Å) on a Bruker SMART Apex II diffractometer equipped with a CCD area detector. For
26
data reduction the SAINT-NT software package was used. With SADABS program, multiscan
27
absorption correction was applied to all intensity data. The structures were solved by a
combination of direct methods with subsequent difference Fourier syntheses and refined by
2
8
fullmatrix least-squares on F2 using the SHELX-2013 suite. In all the cases, the non-hydrogen
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atoms were treated anisotropically. The crystal data along with the refinement details are given
in Table S1.
Computational Details. All the electronic structures were assigned by DFT calculations using
29
30
the Gaussian 09 program with B3LYP hybrid functional (G09/B3LYP). Geometry
optimizations were performed without imposing geometric constraints. Within the calculations
the quasi-relativistic effective core pseudo potential proposed by Hay and Wadt, LANL2DZ
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pseudo potential, and the corresponding optimized set of basis function has been employed for
30
Cu. For carbon, hydrogen, nitrogen, and chlorine 6-31G* basis set was used.
Characterisation Data of the Isolated Compounds.
12,14a
2
-phenylquinoline (5aa).
Eluent: petroleum ether/ethyl acetate (18 : 1). White solid (96%,
1
1
97 mg). Mp: 82–84 °C. H NMR (300 MHz, CDCl
3
): δ (ppm) = 8.24–8.16 (m, 4H), 7.90–7.82
13
1
(
m, 2H), 7.76–7.71 (m, 1H), 7.57–7.44 (m, 4H). C{ H} NMR (100 MHz, CDCl
3
): δ (ppm) =
157.5, 148.4, 139.8, 136.9, 129.8, 129.8, 129.4, 129.0, 127.7, 127.6, 127.3, 126.4, 119.1.
1
2,14a
2-p-tolylquinoline (5ab).
Eluent: petroleum ether/ethyl acetate (18 : 1). White solid (95%,
1
2
08 mg). Mp: 82–83 °C. H NMR (300 MHz, CDCl ): δ (ppm) = 8.18 (t, J = 8.1 Hz, 2H), 8.08
3
(
d, J = 8.1 Hz, 2H), 7.88–7.80 (m, 2H), 7.72 (t, J = 8.1 Hz, 1H), 7.51 (t, J = 8.1 Hz,1H), 7.34 (d,
13
1
J = 7.5 Hz, 2H), 2.44 (s, 3H). C{ H} NMR (100 MHz, CDCl ): δ (ppm) = 157.5, 148.4, 139.5,
3
137.0, 136.8, 129.8, 129.7, 129.4, 128.6, 127.6, 127.2, 126.2, 119.0, 21.5.
1
2,14a,32
2
-(4-methoxyphenyl)quinoline (5ac).
Eluent: petroleum ether/ethyl acetate (18 : 1).
1
White solid (81%, 81 mg). Mp: 122–124 °C. H NMR (300 MHz, CDCl
3
): δ (ppm) = 8.19–8.13
(
m, 4H), 7.82 (t, J = 9.0 Hz, 2H), 7.71 (t, J = 7.2 Hz, 1H), 7.50 (t, J = 7.7 Hz, 1H), 7.05 (d, J =
1
3
1
8
.5 Hz, 2H), 3.9 (s, 3H). C{ H}NMR (75 MHz, CDCl
3
): δ (ppm) = 161.0, 157.1, 148.4, 136.8,
132.4, 129.7, 129.0, 128.8, 127.6, 127.1, 126.1, 118.7, 114.4, 55.5.
3
3
4-(quinolin-2-yl)benzenamine (5ad). Eluent: petroleum ether/ethyl acetate (18 : 1). Yellow
1
solid (75%, 165 mg). Mp: 192–193 °C. H NMR (400 MHz, CDCl
3
): δ (ppm) = 8.11 (d, J = 8.7
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Hz, 2H), 8.01 (d, J = 8 Hz, 2H), 7.76 (t, J = 8.7 Hz, 2H), 7.67 (t, J = 7.5 Hz, 1H), 7.45 (t, J = 8.7
13
1
Hz, 1H), 6.78 (d, J = 7.5 Hz, 2H), 3.85 (s, 2H). C{ H} NMR (100 MHz, CDCl
3
): δ (ppm) =
157.2, 151.6, 148.1, 136.5, 130.7, 129.4, 129.0, 128.7, 127.4, 126.6, 125.5, 118.3, 115.0.
12,32
2
-(4-fluorophenyl)quinoline (5ae).
Eluent: petroleum ether/ethyl acetate (18 : 1). White
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
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8
9
0
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9
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solid (60%, 134 mg). Mp: 126–127 °C. H NMR (300 MHz, CDCl
3
): δ (ppm) = 8.23–8.14 (m,
4
H), 7.83 (d, J = 8.4 Hz, 2H), 7.74 (t, J = 7.5 Hz, 1H), 7.53 (t, J = 7.5 Hz, 1H), 7.26–7.18 (m,
1
3
1
3
2H). C{ H} NMR (75 MHz, CDCl ): δ (ppm) = 163.7 (d, J = 293.1 Hz), 156.4, 148.4, 137.0,
136.0, 130.0, 129.8 (d, J = 10.5 Hz), 129.6, 129.5, 127.6, 127.2, 126.5, 118.8, 115.9 (d, J = 20.3
Hz).
32
2
-(4-chlorophenyl)quinoline (5af). Eluent: petroleum ether/ethyl acetate (18 : 1). White solid
1
(
93%, 223 mg). Mp: 111–112 °C. H NMR (300 MHz, CDCl
3
): δ (ppm) = 8.19–8.08 (m, 4H),
): δ (ppm) = 155.9, 148.1,
1
3
1
7
.80–7.70 (m, 3H), 7.54–7.46 (m, 3H). C{ H} NMR (75 MHz, CDCl
3
137.9, 137.1, 135.6, 130.0, 129.6, 129.1, 128.9, 127.6, 127.3, 126.6, 118.6.
3
2
2-(4-bromophenyl)quinoline (5ag). Eluent: petroleum ether/ethyl acetate (18 : 1). White solid
1
(
96%, 273 mg). Mp: 117–119 °C. H NMR (300 MHz, CDCl
3
): δ (ppm) = 8.16 (d, J = 8.1 Hz,
2
H), 8.04 (d, J = 8.7 Hz, 2H), 7.79 (d, J = 7.5 Hz, 2H), 7.71 (d, J = 8.1 Hz, 1H), 7.63 (d, J = 8.1
13
1
Hz, 2H), 7.58–7.50 (m, 1H). C{ H} NMR (75 MHz, CDCl
3
): δ (ppm) = 156.0, 148.3, 138.5,
137.0, 132.0, 129.9, 129.8, 129.1, 127.6, 127.3, 126.6, 124.0, 118.5.
1
2,14a
2-(4-nitrophenyl)quinoline (5ah).
solid (85%, 213 mg). Mp: 131–132 °C. H NMR (400 MHz, CDCl
Hz, 2H), 7.95 (d, J = 7.1 Hz, 2H), 7.71 (t, J = 7.1 Hz, 2H), 7.61(t, J = 7.1 Hz, 1H), 7.39 (t, J =
Eluent: petroleum ether/ethyl acetate (18 : 1). Brown
1
3
): δ (ppm) = 8.05 (t, J = 8.3
13
1
7
1
2
.1 Hz, 1H), 6.73 (d, J = 10.0 Hz, 2H). C{ H} NMR (100 MHz, CDCl
3
): δ (ppm) = 157.2,
48.3, 147.9, 136.5, 129.8, 129.5, 129.3, 128.8, 127.4, 126.8, 125.6, 118.4, 115.2.
3
2
-(4-(trifluoromethyl)phenyl)quinoline (5ai). Eluent: petroleum ether/ethyl acetate (18 : 1).
1
White solid (66%, 180 mg). Mp: 124–126 °C. H NMR (300 MHz, CDCl
3
): δ (ppm) = 8.26 (t, J
= 7.3 Hz, 3H), 8.20 (d, J = 9.4 Hz, 1H), 7.85–7.82 (m, 2H), 7.79–7.73 (m, 3H), 7.56 (t, J = 7.3
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Hz, 1H). C{ H} NMR (75 MHz, CDCl
3
): δ (ppm) = 155.7, 148.4, 143.0, 137.2, 130.1, 130.0,
128.0, 127.9, 127.6, 127.5, 127.0, 125.9, 125.8, 118.8.
1
2,14a
2
-o-tolylquinoline (5aj).
Eluent: petroleum ether/ethyl acetate (18 : 1). White solid (71%,
1
1
56 mg). Mp: 74–75 °C. H NMR (300 MHz, CDCl ): δ (ppm) = 8.21 (t, J = 8.3 Hz, 2H), 7.86
3
1
1
1
1
1
1
1
1
1
1
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(
dd, J = 8.3, 1.6 Hz, 1H), 7.78–7.73 (m, 1H), 7.59–7.53 (m, 3H), 7.36–7.35 (m, 3H), 2.46 (s, 3H).
1
3
1
3
C{ H} NMR (75 MHz, CDCl ): δ (ppm) =160.3, 147.9, 140.7, 136.1, 136.0, 130.9, 129.7,
129.6, 128.5, 127.5, 126.7, 126.4, 126.0, 122.4, 20.4.
1
4a
2-(2-methoxyphenyl)quinoline (5ak). Eluent: petroleum ether/ethyl acetate (18 : 1). Yellow
1
liquid (62%, 146 mg). H NMR (300 MHz, CDCl3): δ (ppm) = 8.22 (d, J = 8.3 Hz, 1H), 8.14 (d,
J = 8.3 Hz, 1H), 7.90 (dd, J = 7.5, 3 Hz, 2H), 7.82 (d, J = 7.3Hz, 1H), 7.74–7.69 (m, 1H), 7.52 (t,
J = 7.3 Hz, 1H), 7.46–7.40 (m, 1H), 7.16 (t, J = 7.3 Hz, 1H), 7.03 (d, J = 8.3 Hz, 1H), 3.85 (s,
13
1
3
H). C{ H} NMR (75 MHz, CDCl
3
): δ (ppm) = 157.2 (d, J = 6.7 Hz), 148.3, 135.1, 131.5,
130.4, 129.7, 129.6, 129.2, 127.4, 127.1, 126.2, 123.5, 121.3, 111.5, 55.6.
2
2c
2-(2-fluorophenyl)quinoline (5al). Eluent: petroleum ether/ethyl acetate (18 : 1). Yellow
1
liquid (40%, 89 mg). H NMR (500 MHz, CDCl3): δ (ppm) = 8.22–8.18 (m, 2H), 8.10 (td, J =
7
.5, 1.5 Hz, 1H), 7.90–7.84 (m, 2H), 7.76–7.73 (m, 1H), 7.58–7.54 (m, 1H), 7.46–7.41 (m, 1H),
13
1
7
3
.32 (t, J = 7.5 Hz, 1H), 7.23–7.19 (m, 1H). C{ H} NMR (100 MHz, CDCl ): δ (ppm) = 160.9
(
d, J = 247.5 Hz), 148.5, 136.3, 131.7, 130.9 (d, J = 8.8 Hz), 129.8 (d, J = 15.0 Hz), 128.1 (d, J =
12.5 Hz), 127.6, 127.4, 126.7, 124.8, 124.8, 122.6, 122.5, 116.4 (d, J = 22.5 Hz).
2
2c
2-(2-chlorophenyl)quinoline (5am). Eluent: petroleum ether/ethyl acetate (18 :1). White solid
1
(
58%, 139 mg). Mp: 76–78 °C. H NMR (300 MHz, CDCl3): δ (ppm) = 8.20 (t, J = 9.4 Hz, 2H),
13
1
7
.85 (d, J = 8.4 Hz, 1H), 7.77–7.70 (m, 3H), 7.59–7.50 (m, 2H), 7.43–7.36 (m, 2H). C{ H}
): δ (ppm) = 157.4, 148.1, 139.6, 135.7, 132.4, 131.7, 130.1, 129.9, 129.7,
29.7, 127.6, 127.2, 127.2, 126.8, 122.8.
NMR (100 MHz,CDCl
3
1
3
2
2
-(3-bromophenyl)quinoline (5an). Eluent: petroleumether/ethyl acetate (18 : 1). White solid
1
(55%, 156 mg). Mp: 74–75 °C. H NMR (300 MHz, CDCl3): δ (ppm) = 8.36 (t, J = 1.7 Hz, 1H),
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1
3
1
J = 7.9 Hz, 1H). C{ H} NMR (75 MHz, CDCl
3
): δ (ppm) = 155.5, 148.2, 141.6, 137.0, 132.2,
130.6, 130.3, 129.9, 129.8, 127.5, 127.3, 126.7, 126.1, 123.2, 118.6.
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-(3-nitrophenyl)quinolone (5ao). Eluent: petroleum ether/ethyl acetate (18 : 1). White solid
0
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9
0
1
(
69%, 173 mg). H NMR (400 MHz, CDCl3): δ (ppm) = 8.99 (s, 1H), 8.50 (d, J = 5.34 Hz, 1H),
8.25 (d, J = 8.6 Hz, 2H), 8.13 (d, J = 7.1 Hz, 1H), 7.88 (d, J = 10.0 Hz, 1H), 7.81 (d, J = 8.6 Hz,
1
3
1
1H), 7.72 (t, J = 7.1 Hz, 1H), 7.65 (t, J = 8.6 Hz, 1H), 7.53 (t, J = 7.1 Hz, 1H). C{ H} NMR
(75 MHz, CDCl3): δ (ppm) = 154.4, 148.4, 148.2, 141.2, 137.5, 133.9, 130.2, 130.0, 129.8,127.6,
127.4, 127.1, 123.2, 122.4, 118.4.
22c
2
-(pyridin-3-yl)quinoline (5ap). Eluent: petroleum ether/ethyl acetate (18 : 1). Brown solid
1
(
74%, 153 mg). Mp: 65–67 °C. H NMR (500 MHz, CDCl3): δ (ppm) = 9.34 (s, 1H), 8.68 (d, J =
3.5 Hz, 1H), 8.49–8.47 (m, 1H), 8.22 (d, J = 8.5 Hz, 1H), 8.16 (d, J = 8.5 Hz, 1H), 7.85–7.81 (m,
1
3
1
2H), 7.75-7.71 (m, 1H), 7.55–7.52 (m, 1H),7.44–7.41 (m, 1H). C{ H} NMR (100 MHz,
CDCl3): δ (ppm) = 154.6, 150.2, 148.8, 148.4, 137.2, 135.2, 135.0, 130.0, 129.8, 127.6, 127.4,
126.8, 123.7, 118.5.
12,32
3
-methyl-2-phenylquinoline (5aq).
Eluent: petroleum ether/ethyl acetate (18 : 1). Pale-
1
yellow oil (80%, 175 mg). H NMR (500 MHz, CDCl3): δ (ppm) = 8.16 (d, J = 8.0 Hz, 1H),
7.97 (s, 1H), 7.75 (d, J = 8.5 Hz, 1H), 7.66 (t, J = 8.0 Hz, 1H), 7.62–7.60 (m, 2H), 7.51–7.48 (m,
1
3
1
3H), 7.46–7.43 (m, 1H), 2.44 (s, 3H). C{ H} NMR (100 MHz, CDCl3): δ (ppm) =160.6, 146.6,
141.0, 136.9, 129.4, 129.4, 129.0, 128.9, 128.4, 128.3, 127.7, 126.8, 126.5, 20.7.
22c
2
-(thiophen-2-yl)quinoline (5ar). Eluent: petroleum ether/ethyl acetate (18 : 1). Brown solid
1
(
64%, 135 mg). Mp: 131–132 °C. H NMR (500 MHz, CDCl3): δ (ppm) = 8.10 (t, J = 9.0 Hz,
13
1
2
H), 7.78–7.68 (m, 4H), 7.49–7.47 (m, 2H), 7.17–7.15 (m, 1H). C{ H} NMR (100 MHz,
CDCl3): δ (ppm) =152.4, 148.1, 145.4, 136.6, 129.8, 129.3, 128.6, 128.1, 127.5, 127.2, 126.1,
25.9, 117.6.
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2c
2-(thiophen-3-yl)quinoline (5as). Eluent: petroleum ether/ethyl acetate (18 : 1). White solid
1
(79%, 167 mg). Mp: 132–133°C. H NMR (300 MHz, CDCl3): δ (ppm) = 8.17 (d, J = 8.0 Hz,
1
H), 8.08–8.03 (m, 2H), 7.90 (d, J = 5.6 Hz, 1H), 7.72 (q, J = 8.0 Hz, 3H), 7.51–7.41 (m, 2H).
13
1
C{ H} NMR (75MHz, CDCl3): δ (ppm) = 153.2, 148.2, 142.6, 136.6, 129.7, 129.4, 127.5,
1
1
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127.1, 126.9, 126.4, 124.7, 119.0.
3
2
2
-cyclopropylquinoline (5at). Eluent: petroleum ether/ethyl acetate (18 : 1). Pale-yellow oil
1
(78%, 132 mg). H NMR (300 MHz, CDCl3): δ (ppm) = 8.00 (d, J = 8.5 Hz, 1H), 7.93 (d, J =
8.5 Hz, 1H), 7.70 (d, J = 8.1 Hz, 1H), 7.63 (t, J = 7.3 Hz, 1H), 7.41 (t, J = 7.4 Hz, 1H), 7.11 (d, J
13
1
=
8.5 Hz, 1H), 2.28–2.19 (m, 1H), 1.17 (d, J = 3.4 Hz, 2H), 1.09 (d, J = 8.1 Hz, 2H). C{ H}
NMR (75 MHz, CDCl3): δ (ppm) = 163.4, 148.0, 135.8, 129.3, 128.6, 127.5, 126.7, 125.2, 119.3,
18.1, 10.3.
3
2
5
,6-dihydrobenzo[c]acridine (5au). Eluent: petroleum ether/ethyl acetate (18 : 1). White solid
1
(81%, 187 mg). Mp: 64–66 °C. H NMR (300 MHz, CDCl3): δ (ppm) = 8.42 (d, J = 7.4 Hz, 1H),
7.98 (d, J = 8.3 Hz, 1H), 7.67 (s, 1H), 7.53–7.43 (m, 2H), 7.28–7.16 (m, 3H), 7.07 (d, J = 7.3 Hz,
1
3
1
1
H), 2.88 (d, J = 5.8 Hz, 2H), 2.80 (d, J = 5.3 Hz, 2H). C{ H} NMR (75 MHz, CDCl3): δ
(
ppm) = 153.4, 147.6, 139.5, 134.7, 133.8, 130.6, 129.8, 129.4, 128.7, 128.0, 127.9, 127.4, 127.0,
126.1, 28.8, 28.4.
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-chloro-2-phenylquinoline (5ba). Eluent: petroleum ether/ethyl acetate (18 : 1). White solid
1
(67%, 161 mg). Mp: 108–109 °C. H NMR (300 MHz, CDCl3): δ (ppm) = 8.19–8.14 (m, 3H),
8.08 (d, J = 8.7 Hz, 1H), 7.79 (d, J = 8.8 Hz, 1H), 7.67 (d, J = 9 Hz, 1H), 7.57–7.48 (m, 3H),
13
1
7
1
8
.43 (dd, J = 8.7, 1.9 Hz, 1H) . C{ H} NMR (100 MHz, CDCl3): δ (ppm) = 158.1,148.6, 139.1,
36.5, 135.4, 129.7, 128.9, 128.7,127.6, 127.2, 125.5, 119.0.
22c
-bromo-6-methyl-2-phenylquinoline (5ca). Eluent: petroleum ether/ethyl acetate (18 : 1).
1
White solid (71%, 212 mg). Mp: 81–82 °C. H NMR (400 MHz, CDCl3): δ (ppm) = 8.30–8.20
(
m, 3H), 8.06 (t, J = 9.0 Hz, 1H), 7.90 (d, J = 9.0 Hz, 1H), 7.62 (d, J = 9.0 Hz, 1H), 7.49 (t, J =
8.0 Hz, 3H), 2.39 (d, J = 9.0 Hz, 3H) .
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2b,34,35
2-phenylquinazolin-4(3H)-one (8aa).
Eluent: petroleum ether/ethyl acetate (3:1). White
): δ (ppm) = 11.83 (s, 1H),
1
solid (95%, 211 mg). Mp: 240−241 °C. H NMR (300 MHz, CDCl
3
8
.34 (d, J = 8.0 Hz, 1H), 8.28 (s, 2H), 7.86–7.81 (m, 2H), 7.60 (s, 3H), 7.52 (t, J = 8.0 Hz, 1H).
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-(p-tolyl)quinazolin-4(3H)-one (8ab).
Eluent: petroleum ether/ethyl acetate (3:1). White
): δ (ppm) = 12.43 (s, 1H),
.14 (dd, J = 6.0, 3.0 Hz, 1H), 8.08 (d, J = 6.0 Hz, 2H), 7.85–7.80 (m, 1H), 7.72 (d, J = 9.0 Hz,
0
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9
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solid (95%, 224 mg). Mp: 244−246 °C. H NMR (300 MHz, DMSO-d
6
8
13
1
1H), 7.52–7.47 ( m,1H), 7.34 (d, J = 9.0 Hz, 2H), 2.38 (s, 3H). C{ H} NMR (75 MHz, DMSO-
d
2
2
6
): δ (ppm) = 162.8, 152.8, 149.4, 142.0, 135.2, 130.4, 129.8, 128.2, 128.0, 127.0, 126.4, 121.4,
1.5.
35
-(4-methoxyphenyl)quinazolin-4(3H)-one (8ac). Eluent: petroleum ether/ethyl acetate (3:1).
1
White solid (77%, 194 mg). Mp: 240−241 °C. H NMR (400 MHz, DMSO-d
6
): δ (ppm) = 12.40
(
s. 1H), 8.19 (d, J = 8.0 Hz, 2H), 8.13 (d, J = 8.0 Hz, 1H), 7.81 (t, J = 8.0 Hz, 1H), 7.70 (d, J =
1
3
1
8.0 Hz, 1H), 7.48 (t, J = 8.0 Hz, 1H), 7.09 (d, J = 8.0 Hz, 2H), 3.85 (s, 3H). C{ H} NMR (100
MHz, DMSO-d ): δ(ppm) = 162.2, 161.8, 151.9, 148.8, 134.5, 129.4, 127.2, 126.1,125.8, 124.8,
20.6, 114.0,55.4.
6
1
34
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-(4-fluorophenyl)quinazolin-4(3H)-one (8ad). Eluent: petroleum ether/ethyl acetate (3:1).
1
White solid (83%, 199 mg). Mp: 258− 259 °C. H NMR (400 MHz, DMSO-d
6
): δ (ppm) = 12.55
(
s, 1H), 8.25–8.21 (m, 2H), 8.14 (d, J = 8.0, 1H), 7.82(t, J= 8.0 Hz, 1H), 7.72 (d, J = 8.0 Hz, 1H),
13
1
6
7.51(t, J= 8.0 Hz, 1H), 7.37 (t, J = 8.0 Hz, 2H). C{ H} NMR(100 MHz,DMSO-d ): δ (ppm) =
165.3, 162.5 (d, J = 244.0 Hz), 151.4, 148.6, 134.6, 130.4 (d, J = 36.0 Hz), 129.2 (d, J = 12.0
Hz), 127.4, 126.6, 125.8, 120.9, 115.6 (d, J = 88.0 Hz).
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-(4-chlorophenyl)quinazolin-4(3H)-one (8ae). Eluent: petroleum ether/ethyl acetate (3:1).
1
White solid (82%, 211mg). Mp: 294−296 °C. H NMR (400 MHz, DMSO-d
6
): δ (ppm) =12.60
(
s, 1H), 8.21-8.15 (m, 3H), 7.85 (d, J = 8.0 Hz, 1H), 7.74 (d, J = 8.0 Hz, 1H), 7.63 (d, J = 8.0 Hz,
H), 7.54 (t, J = 8.0 Hz, 1H).
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2-(4-bromophenyl)quinazolin-4(3H)-one (8af). Eluent: petroleum ether/ethyl acetate (3:1).
1
White solid (80%, 241 mg). Mp: >300 °C. H NMR (400 MHz, DMSO-d
6
): δ (ppm) = 12.59 (s,
1
H), 8.15–8.10 (m, 3H), 7.83 (t, J = 8.0 Hz, 1H), 7.74 (t, J = 8.0, 2H), 7.53 (t, J = 8.0, 2H).
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-(4-nitrophenyl)quinazolin-4(3H)-one (8ag). Eluent: petroleum ether/ethyl acetate (3:1).
1
1
1
1
1
1
1
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1
1
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8
9
0
1
2
3
4
5
6
7
8
9
0
1
Brown solid (52%, 139 mg). Mp: >300 °C. H NMR (300 MHz, DMSO-d
6
): δ (ppm) = 12.05 (s,
1
H), 8.10–7.94 (m, 3H), 7.76–7.73 (m, 1H), 7.64–7.60 (m, 1H), 7.40 (d, J = 3.3 Hz, 1H), 6.65–
6.61 (m, 2H).
3
4
2-(4-(trifluoromethyl)phenyl)quinazolin-4(3H)-one (8ah). Eluent: petroleum ether/ethyl
1
acetate (3:1). White solid (92%, 267 mg). Mp: >300 °C. H NMR (300 MHz, DMSO-d
6
): δ
(
ppm) = 12.72 (s, 1H), 8.34 (d, J = 9.0 Hz, 2H), 8.17 (dd, J= 6.2, 1.7 Hz, 1H), 7.92 (d, J = 8.0 Hz,
13
1
2
H), 7.85 (dd, J = 6.0, 1.2 Hz, 1H), 7.79–7.76 (m, 1H), 7.59–7.54 (m,1H). C{ H} NMR (75
): δ (ppm) = 162.4, 151.4, 148.5, 135.0, 131.5, 131.0, 128.9, 127.8, 127.3, 126.1,
125.7 (d, J = 3.8 Hz), 121.3.
MHz, DMSO-d
6
34
2-(4-tert-Butyl-phenyl)quinazolin-4(3H)-one (8ai). Eluent: petroleum ether/ethyl acetate (3:1).
1
White solid (94%, 262 mg). Mp: 207−209 °C. H NMR (400 MHz, DMSO-d
6
): δ (ppm) = 12.43
(
s, 1H), 8.14–8.08 (m, 3H), 7.81 (t, J = 8.0 Hz,1H), 7.71 (d, J = 8.0 Hz,1H), 7.54–7.47 (m, 3H),
13
1
1
.29 (s, 9H). C{ H} NMR (75 MHz, DMSO-d
6
): δ (ppm) = 162.5, 154.6, 152.4, 149.0, 134.8,
1
30.0, 127.7, 127.6, 126.7, 126.0, 125.6, 121.0, 34.8, 31.0.
34
2-o-tolylquinazolin-4(3H)-one (8aj). Eluent: petroleum ether/ethyl acetate (3:1). White solid
1
(64%, 151 mg). Mp: 222−224 °C. H NMR (300 MHz, DMSO-d
6
): δ (ppm) = 12.44 ( s, 1H),
8
.16 (dd, J = 9.0, 3 Hz, 1H), 7.86–7.80 (m, 1H), 7.70 (d, J= 9.0 Hz, 1H ), 7.56–7.47 (m, 2H),
13
1
7
6
.42−7.40 (m,1H), 7.35–7.29 (m, 2H), 2.36 (s, 3H). C{ H} NMR (75 MHz, DMSO-d ): δ
(
ppm) = 162.1, 154.6, 148.9, 136.3, 134.8, 134.3, 130.8, 130.2, 129.3,127.5, 127.0, 126.0, 126.0,
121.0, 19.7.
22b
2
-(2-chlorophenyl)quinazolin-4(3H)-one (8ak). Eluent: petroleum ether/ethyl acetate (3:1).
1
White solid (55%, 141 mg). Mp: 194−196 °C. H NMR (400 MHz, CDCl
): δ (ppm) = 10.57 (s,
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1H), 8.27 (d, J = 5.0 Hz, 1H), 7.82–7.79 (m, 3H), 7.54–7.42 (m, 4H). C{ H} NMR (100 MHz,
CDCl ): δ (ppm) = 162.4, 151.2, 149.2, 135.0, 133.0, 132.2, 132.1, 131.6, 130.7, 128.2, 127.6,
27.5, 126.7, 121.3.
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-(2-bromophenyl)quinazolin-4(3H)-one (8al). Eluent: petroleum ether/ethyl acetate (3:1).
0
1
2
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8
9
0
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2
3
4
5
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8
9
0
1
White solid (52%, 157 mg). Mp: 185−187 °C. H NMR (400 MHz, DMSO-d
6
): δ (ppm) = 12.65
(
s, 1H), 8.19 (d, J = 8.0 Hz, 1H), 7.86 (t, J = 8.0 Hz, 1H), 7.78–7.71 (m, 2H), 7.65–7.63 (m, 1H),
1
3
1
7.60–7.46 (m, 3H). C{ H} NMR (75 MHz, DMSO-d
6
): δ (ppm) = 161.6, 153.4, 148.6, 135.9,
134.7, 132.8, 131.8, 130.9, 127.8, 127.6, 127.2, 126.0, 121.3, 121.2 (d, J = 108.0 Hz).
2
2b
2
-m-tolylquinazolin-4(3H)-one (8am). Eluent: petroleum ether/ethyl acetate (3:1). White
1
solid (95%, 224 mg). Mp: 210−211 °C. H NMR (400 MHz, DMSO-d
6
): δ (ppm) = 12.45 (s,
1
H),8.14 (d, J= 8.0 Hz, 1H), 8.00 (s, 1H), 7.95 (d, J = 8.0Hz, 1H), 7.82 (t, J = 8.0Hz, 1H), 7.73
1
3
1
(
d, J = 8.0 Hz, 1H), 7.51(t, J = 8.0Hz, 1H), 7.44–7.38 (m, 2H), 2.39 (s, 3H). C{ H} NMR (100
MHz, DMSO-d ): δ (ppm) = 162.2, 152.4, 148.8, 137.9, 134.6, 132.6, 132.0, 128.5, 128.3, 127.4,
126.5, 125.8, 124.9, 121.0, 21.0.
-(3-methoxyphenyl)quinazolin-4(3H)-one (8an). Eluent: petroleum ether/ethyl acetate (3:1).
6
34
2
1
White solid (93%, 235 mg). Mp: 210−212 °C. H NMR (400 MHz, DMSO-d
): δ (ppm) = 12.52
6
(
s, 1H), 8.16(d, J = 8.0Hz, 1H), 7.84 (t, J = 8.0Hz, 1H), 7.79–7.74 (m, 3H), 7.53 (t, J = 8.0Hz,
13
1
1
H), 7.46 (t, J = 8.0 Hz, 1H), 7.15 (d, J = 8.0Hz, 1H) 3.86 (s, 3H). C{ H} NMR (100 MHz,
): δ (ppm) = 162.4, 159.4, 152.2, 148.7, 134.8, 134.1, 129.9, 127.6, 126.8, 121.1, 120.2,
117.7, 112.6, 55.5.
-(3-chlorophenyl)quinazolin-4(3H)-one (8ao). Eluent: petroleum ether/ethyl acetate (3:1).
DMSO-d
6
22b
2
1
White solid (69%, 177 mg). Mp: 296−297 °C. H NMR (300 MHz, DMSO-d
6
): δ (ppm) = 12.62
(
s, 1H), 8.23 (s, 1H), 8.15 (t, J = 8.0 Hz, 2H), 7.86 (t, J= 8.0 Hz, 1H), 7.77 (d, J = 8.0 Hz, 1H),
7
.67 (d, J = 8.0 Hz, 1H), 7.61–7.54 (m, 2H).
22b
2
-(3-bromophenyl)quinazolin-4(3H)-one (8ap). Eluent: petroleum ether/ethyl acetate (3:1).
1
White solid (65%, 196 mg). Mp: 297−298 °C. H NMR (400 MHz, DMSO-d
): δ (ppm) = 12.62
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(s, 1H), 8.37 (s, 1H), 8.17 (d, J = 8.0 Hz, 2H), 7.88–7.83 (m, 1H), 7.78 (t, J = 8.0 Hz, 2H), 7.56–
7.50 (m, 2H).
2
2b
2
-(2,4-dimethoxyphenyl)quinazolin-4(3H)-one (8aq). Eluent: petroleum ether/ethyl acetate
1
(
3:1). White solid (95%, 268 mg). Mp: 205−206 °C. H NMR (300 MHz, DMSO-d
6
): δ (ppm) =
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
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6
7
8
9
0
1
2
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4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
10.89 (s, 1H), 8.48 (d, J = 9.0 Hz, 1H), 8.26 (d, J = 8.0 Hz, 1H), 7.75–7.73 (m, 2H), 7.43–7.40
1
3
1
(
m, 1H), 6.70–6.56 (m, 1H), 6.56 (s, 1H), 4.03 (s, 3H), 3.89 (s, 3H). C{ H} NMR (75 MHz,
DMSO-d ): δ(ppm) = 163.9, 162.1, 159.3, 150.8, 149.7, 134.5, 133.1, 127.6, 126.4, 121.0, 112.7,
106.6, 98.9, 56.2, 55.7.
-(2,4-dichlorophenyl)quinazolin-4(3H)-one (8ar).
6
2
2b
2
Eluent: petroleum ether/ethyl acetate
3:1). White solid (62%, 180 mg). Mp: 226−227 °C. H NMR (400 MHz, DMSO-d ): δ (ppm) =
2.66 (s, 1H), 8.18 (d, J = 12 Hz, 1H), 7.89–7.81 (m, 2H), 7.71 (d, J = 8.0 Hz, 2H), 7.61–7.55 (m,
H), 7.59–7.51 (m, 1H).
1
(
6
1
2
2
2b
2-(pyridin-2-yl)quinazolin-4(3H)-one (8as).
Eluent: petroleum ether/ethyl acetate (3:1).
): δ (ppm) = 11.80 (s, 1H), 8.74 (d,
1
Yellow solid (56%, 125 mg). H NMR(400 MHz, DMSO-d
6
J = 4.0 Hz, 1H), 8.44 (d, J = 8.0 Hz, 1H), 8.18 (d, J = 8.0Hz, 1H), 8.06 (t, J = 8.0 Hz, 1H), 7.86
(
t, J = 8.0 Hz, 1H), 7.79 (d, J = 8.0 Hz, 1H), 7.65 (t, J = 8.0 Hz, 1H), 7.56 (t, J = 8.0 Hz, 1H).
34
2
-(thiophen-2-yl)quinazolin-4(3H)-one (8at). Eluent: petroleum ether/ethyl acetate (3:1).
1
Yellow solid (68%, 155 mg). Mp: 270−272 °C. H NMR (300 MHz, DMSO-d
6
): δ (ppm) =
12.65 (s, 1H), 8.22 (d, J = 3.0 Hz, 1H), 8.12 (d, J = 6.0 Hz, 1H), 7.86 (d, J = 6.0, 1.0 Hz, 1H),
7.83–7.77 (m, 1H), 7.64 (d, J = 9.0, 1.2 Hz, 1H), 7.48 (t, J = 8.0 Hz, 1.0 Hz, 1H), 7.23–7.21 (t, J
13
1
=
6
8.0 Hz, 1H). C{ H} NMR (75 MHz, DMSO-d ): δ (ppm) = 161.8, 148.7, 147.8, 137.4, 134.7,
132.2, 129.4, 128.5, 127.0, 126.4, 126.0, 120.9.
34
2
-butylquinazolin-4(3H)-one (8au). Eluent: petroleum ether/ethyl acetate (3:1). White solid
1
(
(
35%, 71 mg). Mp: 108−109 °C. H NMR (300 MHz, DMSO-d
6
): δ (ppm) = 12.15 (s, 1H), 8.07
d, J = 9.0 Hz, 1H), 7.79–7.73 (m, 1H), 7.58 (d, J = 9.0 Hz, 1H), 7.47–7.42 (m, 1H), 2.59 (t, J =
1
3
1
8.0 Hz, 2H), 1.75–1.65 (m, 2H), 1.40–1.30 (m, 2H), 0.90 (t, J = 8.0 Hz, 3H). C{ H} NMR (100
2
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4
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4
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5
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5
5
6
MHz, DMSO-d
6
): δ (ppm) = 161.8, 157.5, 148.9, 134.2, 126.7, 125.8, 125.6, 120.7, 34.1, 28.8,
21.6, 13.6.
22b
8
-methyl-2-phenylquinazolin-4(3H)-one (8ba). Eluent: petroleum ether/ethyl acetate (3:1).
1
White solid (95%, 224 mg). Mp: 246−248 °C. H NMR (400 MHz, DMSO-d
6
): δ(ppm) = 12.45
0
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2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
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7
8
9
0
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2
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7
8
9
0
1
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3
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7
8
9
0
(
s, 1H), 8.14 (d, J = 6.0 Hz, 1H), 8.00 (s, 1H), 7.82 (t, J = 8.0 Hz, 1H), 7.73 (d, J = 6.0 Hz, 1H),
1
3
1
6
7.51 (t, J =6.0 Hz, 1H), 7.44−7.38 (m, 2H), 2.39 (s, 3H). C{ H} NMR (100 MHz, DMSO-d ):
δ (ppm) = 161.5, 154.4, 148.7, 136.1, 134.5, 134.2, 130.5, 129.9, 129.1, 127.4, 126.6, 125.8,
125.7, 121.0, 19.6.
22b
6
-methyl-2-phenylquinazolin-4(3H)-one (8da). Eluent: petroleum ether/ethyl acetate (3:1).
1
White solid (94%, 222 mg). Mp: 266−268 °C. H NMR (300 MHz, DMSO-d
6
): δ (ppm) = 12.44
(
s, 1H), 8.16 (dd, J = 6.0 Hz, 3H), 7.95 (s, 1H), 7.65 (s, 2H), 7.58− 7.51 (m, 3H), 2.46 (s, 3H).
2
2b
8
-bromo-2-phenylquinazolin-4(3H)-one (8ca). Eluent: petroleum ether/ethyl acetate (3:1).
1
White solid (68%, 205 mg). Mp: 219−220 °C. H NMR (300 MHz, DMSO-d
6
): δ (ppm) = 12.75
(s, 1H), 8.25 (d, J = 8.0 Hz, 2H), 8.14 (d, J = 4.0 Hz, 2H), 7.62–7.56 (m, 3H), 7.41 (t, J = 8.0 Hz,
1
H).
22b
8
-bromo-6-methyl-2-phenylquinazolin-4(3H)-one (8ea).
Eluent: petroleum ether/ethyl
): δ
1
acetate (3:1). White solid (71%, 224 mg). Mp: >300 °C. H NMR (300 MHz, DMSO-d
6
(
ppm) =12.64 (s, 1H), 8.22 (t, J = 7.5 Hz, 2H), 8.00 (d, J = 3 Hz, 1H), 7.93 (s, 1H), 7.60–7.52 (m,
3H), 2.43 (s, 3H).
8-bromo-6-methyl-2p-tolylquinazolin-4(3H)-one (8eb). Eluent: petroleum ether/ethyl acetate
1
(
3:1). White solid (75%, 247 mg). Mp: >290 °C. H NMR (300 MHz, DMSO-d
6
): δ (ppm)
=12.59 (s, 1H), 8.16 (d, J = 9.0 Hz, 2H), 8.00−7.93 (m, 2H), 7.37 (d, J = 6.0 Hz, 2H), 2.44 (s,
13
1
3
1
6
H), 2.39 (s, 3H) . C{ H} NMR (100 MHz, DMSO-d
6
): δ (ppm) =161.8, 151.9, 144.1, 141.7,
38.8, 137.2, 129.6, 129.2, 127.7, 125.2, 122.1, 121.8, 21.0, 20.4.
22b
,7,8-trimethoxy-2-phenylquinazolin-4(3H)-one (8fa). Eluent: petroleum ether/ethyl acetate
1
(3:1). White solid (96%, 300 mg). Mp: 273−275 °C. H NMR (400 MHz, DMSO-d
): δ (ppm) =
6
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12.49 (s, 1H), 8.20−8.17 (m, 2H), 7.57−7.54 (m, 3H), 7.38 (s, 1H), 4.07(s, 3H), 3.90 (d, J = 9.5
13
1
Hz, 6H). C{ H} NMR (100 MHz, DMSO-d
6
): δ (ppm) = 161.7, 152.2, 149.6, 148.0, 147.2,
138.4, 132.9, 131.1, 128.6, 127.5, 117.1, 101.2, 62.1, 60.9, 56.0.
22b
2
,3-dihydro-2-phenylquinazolin-(1H)-one (9aa). Eluent: petroleum ether/ethyl acetate (3:1).
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
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4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
White solid (87%, 195 mg). H NMR (400 MHz, DMSO-d
6
): δ (ppm) = 8.26 (s, 1H), 7.60 (d, J =
7.6 Hz, 1H), 7.48 (d, J = 7.2 Hz, 2H), 7.39–7.33 (m, 3H), 7.25–7.21 (m, 1H), 7.08 (s, 1H), 6.73
(d, J = 8.0 Hz, 1H), 6.66 (t, J = 7.6 Hz, 1H), 5.74 (s, 1H).
ASSOCIATED CONTENT
Supporting Information. ORTEP, crytal data refinement parameters, FMO's, Cyclic
voltammogram, UV-Vis spectra, IR spectra, CIF file, cartesian coordinates of the metal complex
1
13
and the H and C NMR spectral data of all the synthesized compounds are provided in the
Supporting Information. This material is available free of charge on the ACS Publications
website.
AUTHOR INFORMATION
Corresponding Author
*E-mail: ndpaul@gmail.com; ndpaul2014@chem.iiests.ac.in.
ORCID
Nanda D. Paul: 0000-0002-8872-1413
Notes
The authors declare no competing financial interest.
Acknowledgements
The research was supported by DST (Project: YSS/2015/001552). S.D.; G.C. thanks UGC, S.S.
thanks IIESTS, and R. M. thanks CSIR for fellowship support. Financial assistance from IIESTS
is acknowledged. PB thanks CICECO-Aveiro Institute of Materials, POCI-01-0145-FEDER-
2
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