Fe(CrO2)2-catalyzed, photoactivated oxidative one-pot tandem synthesis of substituted quinolines from primary alcohols and arylamines

Article abstract of DOI:10.1007/s10593-018-2275-1

[Figure not available: see fulltext.] A one-pot tandem synthesis of substituted quinolines involving selective catalytic oxidation of primary alcohols to the corresponding aldehydes and their subsequent condensation with arylamines has been developed. Fe(CrO₂)₂ has been used as a catalyst, and oxidation has been performed with aqueous H₂O₂. To accelerate the catalytic oxidation of alcohols, photoactivation method has been applied.

Full text of DOI:10.1007/s10593-018-2275-1

DOI 10.1007/s10593-018-2275-1
Chemistry of Heterocyclic Compounds 2018, 54(3), 369–374
Fe(CrO2)2-catalyzed, photoactivated oxidative one-pot tandem synthesis
of substituted quinolines from primary alcohols and arylamines
Aynur R. Makhmutov1*, Akhat G. Mustafin1, Salavat M. Usmanov1
1 Bashkir State University,
32 Z. Validi St., Ufa 450076, Russia; e-mail: ainurmax@mail.ru
Published in Khimiya Geterotsiklicheskikh Soedinenii,
2018, 54(3), 369–374
Submitted November 23, 2017
Accepted after revision January 31, 2018
A one-pot tandem synthesis of substituted quinolines involving selective catalytic oxidation of primary alcohols to the corresponding
aldehydes and their subsequent condensation with arylamines has been developed. Fe(CrO2)2 has been used as a catalyst, and oxidation
has been performed with aqueous H2O2. To accelerate the catalytic oxidation of alcohols, photoactivation method has been applied.
Keywords: arylamines, primary alcohols, substituted quinolines, iron-containing catalyst, photoactivation.
Development of processes based on catalytic oxidation
of alcohols to the corresponding aldehydes or ketones and
their exploitation in subsequent synthesis of various classes
of organic substances is of special scientific and practical
interest. As a rule, these chemical transformations are related to
tandem syntheses involving two or more bond-forming
transformations and proceeding in a one-pot mode where
the subsequent reaction is the consequence of the active inter-
mediate formation in the previous chemical transformation.
The considerable availability and stability of alcohols make
them valuable reagents. The tandem approach has been
successfully implemented in synthesis of esters,1 amides,2
alkenes,3 heterocyclic compounds,4 C–H activation pro-
ducts,5 and acetals.6 Catalytic systems in these syntheses
possess two main functions. The first function is oxidation
of the alcohol to the corresponding carbonyl compound
(mainly via transfer of hydrogen atoms to the acceptor
compounds). The second function is catalysis of the
reaction of aldehydes or ketones with various organic sub-
strates to afford the desired products. Catalytic systems
based on ruthenium complexes [Ru(PPh3)3(CO)(H)2] and
[Ru(p-cymene)Cl2]2 have been described in detail.7 Crotono-
nitrile has been usually exploited as a hydrogen acceptor,
and anhydrous and anaerobic environment is essential for
tandem synthesis involving ruthenium catalysts.
Synthesis of substituted quinolines from alcohols and
arylamines in CCl4 has been also described.9 The reaction
proceeded in a pulp digester at 140°C with a fractional
charge of the reagents within 4 h. Iron-containing
compounds were screened for effective catalytic activity in
this chemical transformation.
A feature of iron compounds is their variable valency
(Fe3+ + е– ↔ Fe2+) which allows them to act as mediators
of redox processes.10 As a rule, trivalent iron compounds
are oxidants of organic substances.11 The oxidative
properties of Fe3+ ions are excellently activated not only
thermally but also under ultraviolet (UV) irradiation. Thus,
photooxidation of primary aliphatic alcohols using FeCl3
has been described.11,12 The reaction is completed with total
reduction of Fe3+ ions, and the composition of the mixture
of products depends on the conditions of the process (pH,
the presence of H2O in the system, etc.). Aerobic
photocatalytic oxidation of H2O–alcohol mixtures in the
presence of FeCl3 and NaNO2 leads to selective formation
of aldehydes.12
In this paper, we present the results of the study of a one-pot
tandem synthesis of substituted quinolines based on
selective catalytic oxidation of primary alcohols to
aldehydes and their subsequent condensation reaction with
arylamines promoted by iron chromite (Fe(CrO2)2) and an
oxidizer – 5 wt % aq H2O2. The investigated tandem
synthesis, in contrast to the known methods,7,9 was carried
out in a single batch at room temperature and atmospheric
pressure in an environmentally safe aqueous medium. To
accelerate the chemical transformations, the photoactiva-
Tandem syntheses have been successfully used to
construct practically important nitrogen heterocyclic com-
pounds. For example, 2,3-dialkylindoles were obtained in
the reaction of aniline and vicinal diols in the presence of
iridium and ruthenium complexes at 170°C within 24 h.8
0009-3122/18/54(3)-0369©2018 Springer Science+Business Media, LLC
369

Chemistry of Heterocyclic Compounds 2018, 54(3), 369–374
Scheme 2
tion method was tested. The heterogeneous catalyst –
Fe(CrO2)2 was synthesized by a photochemical method.
Photochemical synthesis of the Fe(CrO2)2 catalyst.
Fe(CrO2)2 was chosen as a heterogeneous catalyst for the
tandem synthesis of substituted quinolines. The uniqueness
of the selected catalyst lies in the fact that it exhibits
catalytic activity both in the oxidation of primary alcohols
to the corresponding aldehydes with aq H2O2 and the
condensation reaction of aldehydes and arylamines. This
feature of Fe(CrO2)2 made it possible to combine the
oxidation and condensation reactions into a single tandem
synthesis.
A number of works have been devoted to the problems
of catalytic oxidation of organic substances, including
alcohols, by a solution of H2O2 in the presence of divalent
iron compounds.13 Such conditions are referred as the
Fenton reaction. Usually, the oxidation process is directed
to the complete destruction of organic substances. However,
the Fenton reaction finds considerable application in
synthetic practice.14 Therefore, in order to avoid a complete
oxidation of alcohols to carboxylic acids and CO2, diluted
aq H2O2 (5 wt %) and less active, insoluble divalent iron
compound – Fe(CrO2)2 as a catalyst have been used in this
work. Consequently, the stage of oxidation of alcohols in
tandem synthesis can be considered as a special case of the
Fenton reaction. The catalytic activity of iron compounds
in the condensation reaction of aldehydes and aniline to
afford different quinolines has been described previously.15
A significant advantage of Fe(CrO2)2 lies in the possibility
of carrying out heterogeneous catalysis because, after the
completion of the tandem process, the catalyst may be
easily separated from the reaction products by simple
decantation or filtration. The catalytic activity of hetero-
geneous Fe(CrO2)2, as indicated by the conversion of the
initial arylamines and the yield of the desired reaction
products, is not inferior to the performance of the known
homogeneous catalyst – FeCl3·6H2O.16
was developed on the basis of the previously studied two-
stage catalytic synthesis of 2,3-dialkylquinolines by
condensation of aniline (1) and photooxidation products of
alcohols in the presence of FeCl3·6H2O.17
The efficiency of the tandem synthesis was estimated
according to the conversion of the starting material 1. The
maximum conversion of compound 1 (62%) to afford
product 3a was achieved in the presence of 1.5 equiv (with
respect to the alcohol) of H2O2 (Table 1, entry 1). In
addition, decrease in the amount of H2O2 to equimolar
reduced the conversion of aniline (1) to 44% and ensured
Table 1. Effect of the structure of alcohol RCH2CH2OH, amount
of H2O2, and photoactivation on the conversion of aniline (1)
and composition of the mixture of tandem synthesis products
2a–d, 3a–d, and 4a–d*
Conversion
of aniline (1)**, %
Composition of the mixture of
reaction products**, %
Entry
R
15 mmol (1.5 equiv) H2O2
1
2
3
4
H
Me
Et
62
60
57
52
2a (–)
2b (–)
2c (–)
2d (–)
3a (98)
3b (96)
3c (95)
3d (92)
4a (2)
4b (4)
4c (5)
4d (8)
Pr
10 mmol (1.0 equiv) H2O2
5
6
7
8
H
Me
Et
44
41
38
33
2a (50)
2b (54)
2c (56)
2d (61)
3a (38)
3b (34)
3c (31)
3d (24)
4a (12)
4b (12)
4c (13)
4d (15)
Catalyst Fe(CrO2)2 was synthesized in a photochemical
reaction of FeCl3·6H2O and K2Cr2O7 in H2O–EtOH
solution (Scheme 1). The reaction proceeded under the
irradiation with Hg lamp at 20°C for 1 h. The developed
photochemical method allowed to isolate Fe(CrO2)2 in
quantitative yield. The resulting catalyst was a finely
dispersed, black-brown powder.
Pr
5 mmol (0.5 equiv) H2O2
9
H
Me
Et
29
25
22
20
2a (62)
2b (63)
2c (62)
2d (63)
3a (22)
3b (20)
3c (20)
3d (19)
4a (16)
4b (17)
4c (18)
4d (18)
10
11
12
Scheme 1
Pr
Photoactivation, 150 mmol (1.25 equiv) H2O2***
13
14
15
16
H
Me
Et
98
92
89
87
2a (–)
2b (–)
2c (–)
2d (–)
3a (97)
3b (95)
3c (95)
3d (91)
3a (24)
3e (66)
4a (3)
4b (5)
4c (5)
4d (9)
4a (8)
4e (2)
Pr
Effect of the amount of H2O2 on the yield of tandem
synthesis products. The Fe(CrO2)2-catalyzed reaction of
aniline (1) and primary aliphatic alcohols in the presence of
H2O2 is shown in Scheme 2. Products of the initially
selected model reaction of EtOH and aniline (1) were
2-methyl-1,2-dihydroquinoline (2a), a stable precursor of
the desired product 2-methylquinoline (3a), and a by-
product N-ethylaniline (4a). The presented tandem process
17 H (Ph)*4
˃99
2a (–)
* Reaction conditions: Fe(CrO2)2 (4 mol %), RCH2CH2OH (10 mmol),
aq H2O2 (5 wt %), rt, 9 h, then aniline (1) (5 mmol), rt, 5 min.
** Determined by GC.
*** Reaction conditions: Fe(CrO2)2 (4 mol %), RCH2CH2OH (120 mmol),
aq H2O2 (5 wt %, 150 mmol), λ <400 nm, rt, 2 h, then aniline (1)
(50 mmol), rt, 5 min.
*4 Equimolar mixture of EtOH and BnOH was exploited.
370

Chemistry of Heterocyclic Compounds 2018, 54(3), 369–374
Scheme 3
FeO·Cr2O3
FeO·Cr2O3
H2O2
h OH
.OH
.OH
Path a
H2O2
N
5aA
Me
– 2 H2O
H2O
H2O
O
FeO·Cr2O3
– 1
1
EtOH
– H2O
N
H
2a
Me
Me
H
N
Me
Path b
5aA
3a
N
H
5aB
– 4a
CH2
the formation of products 2a, 3a, and 4a with a molar ratio of
4:3:1 (entry 5). Intermediate 2a could be easily oxidized to
2-methylquinoline (3a) by input of an additional amount of
H2O2. With a further decrease in the amount of H2O2 to
0.5 equiv, the conversion of the starting material 1 was
only 29%, and the formation of compound 4a was slightly
favored, as indicated by the molar ratio of the products
(entry 9).
Oxidation of EtOH to acetaldehyde by H2O2 in the
presence of the catalyst Fe(CrO2)2 (4 mol %) was the
slowest reaction of the tandem synthesis and proceeded at
20°C for 9 h. An attempt to accelerate the oxidation step by
increasing temperature favored the formation of a mixture
of oxidation products and their derivatives – acetaldehyde,
1,1-diethoxyethane, AcOH, EtOAc, and CO2. Conse-
quently, the tendency of aldehyde formation decreases at
elevated temperatures leading to poor selectivity in the
condensation reaction stage of the tandem synthesis.
The photoactivation method for increasing the
efficiency of tandem synthesis of 2-methylquinoline
(3a). In order to accelerate the oxidation of EtOH and
improve the selectivity toward acetaldehyde, the photo-
activation method was applied. It is known that UV
irradiation enhances the productivity of the photo-Fenton
reaction due to the expedited hydroxyl radical generation
stage: Fe(OH)2+ + hν → Fe2+ + ·OH.18 As established
earlier, the photogenerated radicals ·OH can easily and
selectively oxidize H2O–alcohol mixtures to aldehydes in
the presence of FeCl3·6H2O.12 The approach of the
photogeneration of ·OH radicals allowed to improve the
overall efficiency of the tandem synthesis of 2-methyl-
quinoline (3a) by increasing the selectivity of the oxidation
of EtOH and reducing the reaction time to 2 h.
The presumptive mechanism of the photoactivated
EtOH oxidation to acetaldehyde and its further conden-
sation with aniline (1) in the presence of Fe(CrO2)2 and
aq H2O2 (1.25 equiv relative to the alcohol) is shown in
Scheme 3. As a result of interaction of H2O2 and FeO, the
catalyst Fe(CrO2)2 (or FeO·Cr2O3) is oxidized to Fe(OH)O,
and hydroxyl radical ·OH is formed. Absorbing a quantum
of the Hg lamp irradiation, the oxidized form of Fe(OH)O
is degraded by releasing ·OH, and the catalyst is restored to the
original form. Thus, there is a cyclic photoredox process that
generates two hydroxyl radicals during one catalytic cycle.
In aqueous medium, EtOH is selectively oxidized to
acetaldehyde by hydroxyl radicals.12 The reaction of aniline
(1) with acetaldehyde gives a Schiff base existing in two
tautomeric forms: aldimine 5aA and enamine 5aB.
Interaction of these compounds in the presence of catalyst
Fe(CrO2)2 leads to 2-methyl-1,2-dihydroquinoline (2a).19
The final product 3a is formed in oxidation of compound
2a by H2O2 according to path a. However, when H2O2 is
deficient, azomethine 5aA can also function as an
oxidizing agent, and by-product 4a is formed (path b). A
more detailed study of the photoactivated catalytic tandem
process mechanism is the subject of further work.
The influence of the structure of alcohol and
arylamine on tandem synthesis. The influence of the
structure of primary aliphatic alcohol on the conversion of
the starting material 1 and the yield of the reaction products
2, 3, and 4 a–d was studied (Scheme 2, Table 1). Increase
in the length of the hydrocarbon radical of the alcohol
caused a decrease in the conversion of aniline (1). In the
presence of excess oxidant (1.5 equiv H2O2), selective
conversion of starting material 1 to substituted quinolines
3a–d occurred (Table 1, entries 1–4). However, as in the
case of the model system, a decrease in the amount of
oxidant affected the composition of the reaction product
mixture. 1,2-Dihydroquinolines 2a–d and N-alkylanilines
4a–d were obtained along with products 3a–d when an
equimolar amount of H2O2 was used (entries 5–8). It is
evident that the proportion of 1,2-dihydroquinolines
increases with the length of the alkyl radical of the alcohol.
Moreover, in the presence of 0.5 equiv of oxidizing agent,
conversion of aniline (1) was significantly lower and the
amount of N-alkylanilines 4a–d in the reaction mixture
increased with the length of the alkyl radical of the alcohol
(entries 9–12).
Under the conditions of photoactivated tandem synthe-
sis, conversion of the starting material 1 and the yield of
the desired products 3a–d were the highest and did not
depend on the structure of the investigated alcohols
371

Chemistry of Heterocyclic Compounds 2018, 54(3), 369–374
Scheme 4
(Scheme 4, Table 1, entries 13–16). The products of
tandem synthesis with aliphatic alcohols were 2,3-disub-
stituted quinolines 3a–d and N-alkylanilines 4a–d.
1,2-Dihydroquinolines 2a–d were not found in the reaction
mixture because they were completely oxidized by H2O2.
When equimolar mixture of EtOH and benzyl alcohol
(BnOH) was exploited in the synthesis, formation of
2-phenylquinoline (3e), 2-methylquinoline (3a), and small
amount of by-products 4a,e was observed (Scheme 4). As
indicated by the experimental data, the ratio of the products
was shifted toward compound 3e (Table 1, entry 17).
Consequently, the more favorable direction of photo-
activated tandem synthesis with a mixture of aliphatic and
aromatic alcohols is the formation of 2-aryl-substituted
quinolines.
The effect of the structure of arylamines was tested in
the reaction of o-, m-, and p-toluidines 6a–c and EtOH
(Scheme 5). The presence and different location of the methyl
group in the benzene ring did not affect the conversion of
arylamines (in all cases 98%). The yield of the desired
products – dimethylquinolines 7a–d was up to 96%.
Shimadzu QP2010 Ultra, equipped with a Restek Rtx-5MS
column (length 30 m, internal diameter 0.25 mm, thickness
of a liquid film 0.25 μm), was used to identify the products
of the tandem synthesis; electron ionization (70 eV). The
composition of the mixture of reaction products was
established using a hardware-software complex based on
Khromatek Kristall 5000.1 (with an electron capture
detector – ECD) and 5000.2 (with a flame ionization
detector – FID) chromatographs, equipped with Agilent
Technologies 19091F-413 HP-FFAP (30 m × 0.32 mm,
0.25 μm) and SGE Analytical Science (30 m × 0.32 mm,
0.5 μm) columns, respectively. For calibration, standard
solutions of reaction products 3a–e and 4a–e with a
concentration of 0.01 M, 0.05 M, and 0.1 M in Et2O were
used. Standard compounds 3a–e and 4a–e were synthesized
and isolated according to the method reported previously.17
Commercially available substituted anilines 6a–c (Acros),
aliphatic alcohols (EKOS-1) were distilled prior to use as
the starting materials. Chemically pure FeCl3·6H2O (Brom)
and K2Cr2O7 (Russkiy khrom) were exploited without
additional purification.
Tandem synthesis of substituted quinolines 3a–d
without photoactivation (General method). The synthesis
was carried out in a 20-ml glass vial with constant stirring
by means of a magnetic stirrer. To a finely dispersed
Fe(CrO2)2 (90 mg, 4 mol %), the corresponding alcohol
(10 mmol) was added. The mixture was then shaken and
left for 24 h. Just before the reaction, the suspension of the
catalyst in alcohol was subjected to ultrasonic treatment for
10 min. To the obtained suspension, aq H2O2 (5 wt %,
10 ml, 15 mmol) was added. The reaction mixture was
stirred at room temperature and atmospheric pressure for
9 h. Then aniline (1) (466 mg, 5 mmol) was added and
stirring was continued for 5 min. After completion of the
reaction, the mixture was extracted with Et2O (10 ml). The
upper organic phase was separated, dried with anhydrous
MgSO4, and Et2O was removed under reduced pressure.
The residue was fractionally distilled under reduced
pressure to afford products 3a–d.
Photoactivated tandem synthesis of substituted
quinolines 3a–e, 4a–e, and 7a–d (General method). Synthe-
sis was carried out in a Lelesil Innovative Systems photo-
catalytic reactor with a 500-ml quartz reactor. Fe(CrO2)2
(1.07 g, 4 mol %) and the corresponding alcohol (120 mmol)
were placed in the reactor flask, shaken, and left for 24 h.
Just before the reaction, the suspension of the catalyst in
alcohol was subjected to ultrasonic treatment for 10 min.
To the obtained suspension, aq H2O2 (5 wt %, 102 ml,
150 mmol) was added. The reactor was connected to the
installation in accordance with the manufacturer's instruct-
ions. The source of the radiation was a medium-pressure
Scheme 5
EtOH, H2O2
Fe(CrO 2)2 (4 mol %)
Me
Me
H2O, rt, 2 h
 < 400 nm
N
Me
NH2
6a (2-Me)
7a (8-Me, 94%)
b (3-Me)
b (7-Me, 51%) + c (5-Me, 45%)
c
d
(6-Me, 92%)
(4-Me)
In conclusion, study of the tandem synthesis consisting
of selective catalytic oxidation of primary alcohols to the
corresponding aldehydes and their condensation with
arylamines in the presence of a heterogeneous catalyst –
Fe(CrO2)2 and an oxidizer H2O2 has been presented. The
catalyst Fe(CrO2)2 was obtained by the photochemical
synthesis. The developed reaction sequence afforded the
desired products – alkyl- and aryl-substituted quinolines in
high yield. The concentration of the oxidizer and exploita-
tion of photoactivation has the greatest effect on the yield
of the products. In the case of photoactivation, the tandem
synthesis of substituted quinolines is accelerated and their
yield is increased. A probable mechanism of photoactivated
tandem synthesis of 2-methylquinoline is proposed.
Experimental
1H and 13C NMR spectra were acquired on a Bruker
Avance III pulsed spectrometer (500 and 125 MHz,
respectively) using СDCl3 as a solvent and TMS as internal
standard.
A
gas chromatograph–mass spectrometer
372

Chemistry of Heterocyclic Compounds 2018, 54(3), 369–374
Hg lamp with a power of 250 W. The spectral composition
of the radiation was as follows (in terms of energy): UV
(48%), visible (43%), and IR (9%). The range of wave-
lengths was 222–1368 nm. A light flux reached the reaction
system passing through an aqueous layer thermostated at
20°C. Photoactivation was performed within 2 h. Then,
aniline (1) (4.66 g, 50 mmol) or arylamine 6a–c (50 mmol)
was added. The reaction mixture was stirred for 5 min.
After completion of the reaction, the mixture was extracted
with Et2O (100 ml). The upper organic phase was
separated, dried with anhydrous MgSO4, and Et2O was
removed under reduced pressure. The residue was
fractionally distilled under reduced pressure to afford
products 3a–e, 4a–e, and 7a–d.
2-Butyl-3-propylquinoline (3d). Yield 9.0 g (91%),
1
yellow oily liquid, bp 143°C (1 mmHg). H NMR spectrum,
δ, ppm (J, Hz): 1.13 (3H, t, J = 7.2, (CH2)2CH2CH3); 1.25
(3H, t, J = 7.2, CH2CH2CH3); 1.38 (2H, m, (CH2)2CH2CH3);
1.71 (2H, m, CH2CH2CH3); 1.75 (2H, m, CH2CH2CH2CH3);
2.72 (2H, t, J = 7.5, CH2(CH2)2CH3); 2.81 (2H, t, J = 7.2,
CH2CH2CH3); 7.53 (1H, t, J = 7.8, H-6); 7.62 (1H, t,
J = 7.8, H-7); 7.65 (1H, s, H-4); 7.78 (1H, d, J = 7.8, H-5);
8.01 (1H, d, J = 7.9, H-8). 13С NMR spectrum, δ, ppm: 13.4;
13.9; 22.8; 23.2; 31.9; 34.4; 35.7; 125.5; 126.9; 127.2;
128.3; 128.5; 130.2; 134.2; 146.8; 161.1. Mass spectrum,
m/z (Irel, %): 227 [M]+ (25), 184 (11), 157 (100), 115 (12).
2-Phenylquinoline (3e). Yield 6.7 g (66%), pale-yellow
1
powder, mp 82°C. H NMR spectrum, δ, ppm (J, Hz): 7.46–
The physicochemical parameters and spectroscopic
characteristics of the reaction products 3a–e, 4a–e, and 7a–d
correspond to the literature data.9,20
7.74 (5H, m, H Ar); 7.79 (1H, d, J = 8.4, H-4); 7.89 (1H, d,
J = 8.8, H-3); 8.11–8.16 (3H, m, H-5,6,7); 8.19–8.22 (1H,
m, H-8). 13С NMR spectrum, δ, ppm: 119.5; 127.1; 127.2;
127.7; 127.8; 128.2; 129.1; 130.4; 131.8; 137.2; 139.0;
145.9; 157.9. Mass spectrum, m/z (Irel, %): 206 (21), 205
[M]+ (100), 204 (53), 102 (20).
2-Methyl-1,2-dihydroquinoline (2a). Mass spectrum,
m/z (Irel, %): 145 [M]+ (23), 144 (33), 143 (97), 130 (100).
2-Ethyl-3-methyl-1,2-dihydroquinoline (2b). Mass
spectrum, m/z (Irel, %): 173 [M]+ (19), 172 (41), 171 (94),
144 (100).
N-Ethylaniline (4a). Yield 178 mg (3%), pale-yellow
1
oily liquid, bp 72–73°C (10 mmHg). H NMR spectrum,
3-Ethyl-2-propyl-1,2-dihydroquinoline (2c). Mass
spectrum, m/z (Irel, %): 201 [M]+ (22), 200 (37), 199 (96),
156 (100).
δ, ppm (J, Hz): 1.30 (3H, t, J = 7.2, CH3); 3.21 (2H, q,
J = 7.2, СH2); 3.65 (1H, br. s, NH); 6.66 (2H, d, J = 7.6,
H-2,6); 6.74 (1H, t, J = 7.6, H-4); 7.21 (2H, t, J = 7.6,
H-3,5). 13С NMR spectrum, δ, ppm: 14.9; 38.5; 112.9;
117.2; 129.3; 148.5. Mass spectrum, m/z (Irel, %): 121 [M]+
(50), 106 (100), 93 (10), 79 (15), 77 (20), 44 (15).
2-Butyl-3-propyl-1,2-dihydroquinoline (2d). Mass
spectrum, m/z (Irel, %): 229 [M]+ (28), 228 (35), 227 (91),
172 (100).
2-Methylquinoline (3a). Yield 6.7 g (97%), yellow oily
N-Propylaniline (4b). Yield 310 mg (5%), yellow oily
1
1
liquid, bp 80–81°C (2 mmHg). H NMR spectrum, δ, ppm
liquid, bp 96°C (10 mmHg). H NMR spectrum, δ, ppm
(J, Hz): 2.78 (3H, s, CH3); 7.22 (1H, d, J = 8.0, H-3); 7.46
(1H, t, J = 7.5, H-6); 7.68 (1H, t, J = 7.5, H-7); 7.73 (1H, d,
J = 9.2, H-5); 7.97 (1H, d, J = 8.0, H-8); 8.03 (1H, d,
J = 7.5, H-4). 13С NMR spectrum, δ, ppm: 25.1; 121.7;
125.4; 126.3; 127.4; 128.8; 129.2; 135.8; 147.8; 158.7.
Mass spectrum, m/z (Irel, %): 143 [M]+ (100), 128 (20), 115
(22).
2-Ethyl-3-methylquinoline (3b). Yield 7.5 g (95%),
yellow oily liquid, bp 97–99°C (2 mmHg). 1H NMR
spectrum, δ, ppm (J, Hz): 1.38 (3H, t, J = 7.2, CH2CH3);
2.38 (3Н, s, CH3); 2.96 (2Н, q, J = 7.6, CH2); 7.40 (1H, t,
J = 8.0, H-7); 7.58 (1H, t, J = 8.0, H-6); 7.62 (1H, d,
J = 8.0, H-5); 7.70 (1H, s, H-4); 8.06 (1H, d, J = 8.0, H-8).
13С NMR spectrum, δ, ppm: 12.8; 18.6; 29.4; 125.6; 126.7;
127.3; 128.2; 128.5; 129.3; 135.6; 146.7; 163.2. Mass
spectrum, m/z (Irel, %): 172 (12), 171 [M]+ (100), 170 (73),
168 (21), 143 (26), 128 (16), 77 (13).
(J, Hz): 1.13 (3H, t, J = 7.2, CH3); 1.77 (2H, m,
CH2СH2CH3); 3.20 (2H, t, J = 7.0, СH2CH2CH3); 3.72 (1H,
br. s, NH); 6.75 (2H, d, J = 8.2, H-2,6); 6.84 (1H, t, J = 8.1,
H-4); 7.24 (2H, t, J = 8.0, H-3,5). 13С NMR spectrum,
δ, ppm: 11.8; 22.9; 45.9; 112.8; 117.2; 129.5; 148.7. Mass
spectrum, m/z (Irel, %): 135 [M]+ (17), 106 (100), 77 (21).
N-Butylaniline (4c). Yield 332 mg (5%), yellow oily
1
liquid, bp 112–113°C (10 mmHg). H NMR spectrum,
δ, ppm (J, Hz): 1.35 (3H, t, J = 7.6, CH3); 1.38–1.52 (2H,
m, (СH2)2СH2CH3); 1.52–1.70 (2H, m, СH2СH2СH2CH3);
3.10 (2H, t, J = 6.8, СH2(СH2)2CH3); 3.81 (1H, br. s, NH);
6.61 (2H, d, J = 7.6, H-2,6); 6.71 (1H, t, J = 6.8, H-4); 7.19
(2H, t, J = 7.2, H-3,5). 13С NMR spectrum, δ, ppm: 13.8;
22.9; 30.2; 43.3; 112.7; 117.1; 129.2; 148.6. Mass
spectrum, m/z (Irel, %): 149 [M]+ (20), 106 (100), 77 (14).
N-Pentylaniline (4d). Yield 639 mg (9%), yellow oily
1
liquid, bp 124–125°C (10 mmHg). H NMR spectrum,
3-Ethyl-2-propylquinoline (3c). Yield 8.3 g (95%),
yellow oily liquid, bp 118°C (1 mmHg). 1H NMR
spectrum, δ, ppm (J, Hz): 0.97 (3H, t, J = 7.2,
CH2CH2CH3); 1.11 (3H, t, J = 7.2, CH2CH3); 1.80–1.90
(2H, m, CH2CH2CH3); 2.82 (2Н, q, J = 7.2, СH2CH3); 2.99
(2Н, t, J = 8.0, CH2CH2CH3); 7.44 (1H, t, J = 8.0, H-7);
7.62 (1H, t, J = 7.2, H-6); 7.72 (1H, d, J = 7.6, H-5); 7.84
(1H, s, H-4); 8.08 (1H, d, J = 8.0, H-8). 13С NMR
spectrum, δ, ppm: 14.4; 14.5; 22.9; 25.2; 37.8; 125.6;
126.9; 127.5; 128.4; 129.2; 133.9; 146.4; 162.1. Mass
spectrum, m/z (Irel, %): 199 [M]+ (27), 170 (14), 158 (17),
157 (100).
δ, ppm (J, Hz): 1.39 (3H, t, J = 7.0, CH3); 1.42–1.53 (2H, m,
(СH2)3СH2CH3); 1.55–1.70 (2H, m, (СH2)2СH2СH2CH3);
1.74–1.98 (2H, m, CH2СH2(СH2)2CH3); 3.06 (2H, t,
J = 7.4, CH2(СH2)3CH3); 3.92 (1H, br. s, NH); 6.76 (2H, d,
J = 8.0, H-2,6); 7.03 (1H, t, J = 8.0, H-4); 7.24 (2H, t,
J = 8.0, H-3,5). 13С NMR spectrum, δ, ppm: 13.9; 22.6;
29.5; 32.3; 43.2; 112.9; 124.7; 129.2; 147.7. Mass
spectrum, m/z (Irel, %): 163 [M]+ (11), 107 (11), 106 (100),
77 (20), 51 (12), 41 (10).
N-Benzylaniline (4e). Yield 183 mg (2%), pale-yellow
crystalline powder, mp 35–38°C. 1H NMR spectrum,
δ, ppm (J, Hz): 4.05 (1H, br. s, NH); 4.38 (2H, s, CH2);
373

Chemistry of Heterocyclic Compounds 2018, 54(3), 369–374
7. (a) Watson, A. J. A.; Maxwell, A. C.; Williams, J. M. J. Org.
6.78 (2H, d, J = 8.2, H-2,6); 6.87 (1H, t, J = 8.1, H-4); 7.24
(2H, t, J = 8.2, H-3,5); 7.26–7.33 (5H, m, H Ar). 13С NMR
spectrum, δ, ppm: 48.6; 112.9; 124.8; 127.2; 127.7; 129.2;
140.2; 147.9. Mass spectrum, m/z (Irel, %): 183 [M]+ (50),
182 (19), 106 (17), 91 (100), 77 (14), 65 (13).
Biomol. Chem. 2012, 10, 240. (b) Watson, A. J. A.;
Maxwell, A. C.; Williams, J. M. J. Org. Lett. 2009, 11, 2667.
8. Tursky, M.; Lorentz-Petersen, L. L. R.; Olsen, L. B.; Madsen, R.
Org. Biomol. Chem. 2010, 8, 5576.
9. (a) Khusnutdinov, R. I.; Bayguzina, A. R.; Aminov, R. I. Russ.
Chem. Bull., Int. Ed. 2013, 62, 133. [Izv. Akad. Nauk, Ser.
Khim. 2013, 134.] (b) Khusnutdinov, R. I.; Bayguzina, A. R.;
Aminov, R. I. Russ. J. Gen. Chem. 2015, 85, 2725.
[Zh. Obshch. Khim. 2015, 1993.] (c) Khusnutdinov, R. I.;
Bayguzina, A. R.; Aminov, R. I. Russ. J. Gen. Chem. 2016,
86, 1613. [Zh. Obshch. Khim. 2016, 1135.]
2,8-Dimethylquinoline (7a). Yield 7.2 g (94%), yellow
1
oily liquid, bp 65–66°C (0.3 mmHg). H NMR spectrum,
δ, ppm (J, Hz): 2.65 (3H, s, CH3); 2.87 (3H, s, CH3); 6.98
(1H, d, J = 8.0, H-5); 7.24 (1H, d, J = 7.6, H-3); 7.38 (1H,
t, J = 8.0, H-6); 7.65 (1H, d, J = 8.0, H-7); 7.89 (1H, d,
J = 7.6, H-4). 13С NMR spectrum, δ, ppm: 21.6; 25.7;
121.6; 125.3; 126.9; 127.3; 128.3; 136.5; 137.5; 144.7;
157.9. Mass spectrum, m/z (Irel, %): 157 [M]+ (100), 156
(31), 143 (10).
10. Eggins, B. R. Chemical Sensors and Biosensors; Wiley:
Chichester, 2002, p. 142.
11. Makhmutov, A. R.; Usmanov, S. M. Bashkir. Khim. Zh. 2017,
24(1), 18.
2,6-Dimethylquinoline (7d). Yield 7.1 g (92%), pale-
yellow crystalline powder, mp 56–60°C.9а 1H NMR
spectrum, δ, ppm (J, Hz): 2.54 (3H, s, CH3); 2.72 (3H, s,
CH3); 7.21 (1H, d, J = 7.6, H-3); 7.59 (1H, d, J = 8.4, H-7);
7.73 (1H, s, H-5); 7.95 (1H, d, J = 7.6, H-4); 7.93 (1H, d,
J = 8.4, H-8). 13С NMR spectrum, δ, ppm: 21.4; 25.1;
121.8; 126.4; 128.3; 131.5; 135.2; 135.4; 146.8; 157.8.
Mass spectrum, m/z (Irel, %): 157 [M]+ (100), 156 (32).
12. Makhmutov, A. R.; Usmanov, S. M. Bashkir. Khim. Zh. 2017,
24(4), 33.
13. (a) Walling, C. Acc. Chem. Res. 1975, 8, 125. (b) Tyre, B. W.;
Watts, R. J.; Miller, G. C. J. Environ. Qual. 1991, 20, 832.
14. Barbusiński, K. Ecol. Chem. Eng. S 2009, 16, 347.
15. Bulgakov, R. G.; Kuleshov, S. P.; Vafin, R. R.;
Dzhemilev, U. M. Russ. J. Org. Chem. 2009, 45, 944.
[Zh. Org. Khim. 2009, 956.]
16. Makhmutov, A. R.; Usmanov, S. M. Bashkir. Khim. Zh. 2017,
24(3), 45.
Authors thank Center for the Collective Use
“Chemistry” of the Institute of Organic Chemistry, Ufa
Scientific Center of the Russian Academy of Sciences.
17. Makhmutov, A. R. J. Sib. Fed. Univ., Chem. 2017, 10, 154.
18. (a) Pozdnyakov, I. P.; Vorobyev, D. Yu.; Glebov, E. M.;
Plyusnin, V. F.; Grivin, V. P.; Ivanov, Y. V.; Bazhin, N. M.
Mendeleev Commun. 2000, 10, 185. (b) Pozdnyakov, I. P.;
Plyusnin, V. F.; Glebov, E. M.; Grivin, V. P.; Vorobyev, D. Yu.;
Bazhin, N. M.; Sosedova, Yu. A. Int. J. Photoenergy 2004,
6, 89.
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