Microwave-Assisted Metal-Free Rapid Synthesis of C4-Arylated Quinolines via Povarov Type Multicomponent Reaction

Article abstract of DOI:10.1002/ejoc.201900325

A rapid microwave assisted, (±) camphor-10-sulfonic acid (CSA) promoted, Povarov type multicomponent synthesis of 4-arylated quinolines from anilines, alkynes, and paraformaldehyde is described. This reaction proceeds through [4+2] cycloaddition of imine (formed in situ from aniline and paraformaldehyde) and alkynes in the presence of CSA, without any metal catalyst. Mechanistic study revealed that CSA inhibit the synthesis of Troger's base and assist the cycloaddition of imines with alkynes by activating the imine.

Full text of DOI:10.1002/ejoc.201900325

A Journal of
Accepted Article
Title: Microwave-Assisted Metal-Free Rapid Synthesis of C4-Arylated
Quinolines via Povarov Type Multicomponent Reaction
Authors: Devesh Chandra, Ankit Kumar Dhiman, Rakesh Kumar, and
Upendra Sharma
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To be cited as: Eur. J. Org. Chem. 10.1002/ejoc.201900325
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10.1002/ejoc.201900325
European Journal of Organic Chemistry
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Microwave-Assisted Metal-Free Rapid Synthesis of C4-
Arylated Quinolines via Povarov Type Multicomponent
Reaction
Devesh Chandra,[a] Ankit Kumar Dhiman,[a] Rakesh Kumar,[a] and Upendra Sharma*[a]
Abstract: Herein rapid microwave assisted, (±) camphor-10-sulfonic acid (CSA) promoted Povarov type multicomponent synthesis of 4-
arylated quinolines from anilines, alkynes, and paraformaldehyde is described. This reaction proceeds through [4+2] cycloaddition of
imine (formed in situ from aniline and paraformaldehyde) and alkynes in presence of CSA, without any metal catalyst. Mechanistic study
revealed that CSA inhibit the synthesis of Troger’s base and assist the cycloaddition of imine with alkyne by activating imine.
Keywords: Quinoline, alkyne, (±) camphor-10-sulfonic acid, Povarov reaction, microwave synthesis.
for 2,4-disubstituted quinolines synthesis. Recently, Jiang
and coworkers disclosed a Zn-promoted synthesis of 4-
substituted quinoline from vinyl azides and anilines through
dual synthon approach.[11]
Introduction
For the synthesis and functionalization of quinolines, rapid
transition metal-free/additive-free synthetic protocols are in
high demand as quinoline scaffolds have been recognized as
vital heterocyclic motifs obeying to their importance in natural
products, pharmaceuticals, and material science.[1] Among
them, 4-arylated quinolines possess excellent biological
activities[2], and leading examples include yaequinolone[3] and
peniprequinolone[4] (Figure 1). Substituted quinolines are also
being used in dye stuff[5] and photonics.[6]
Figure 1. Representative examples of 4-aryl quinolines.
Obeying to the importance of 4-aryl quinolines, various
methods have been developed for their synthesis. These
includes Ni-catalyzed cyclization of 2-iodoanilines with
alkynyl aryl ketones,[7] and Cu-catalyzed multicomponent
Scheme 1. Seelected examples of 4-arylated quinoline synthesis.
synthesis of 2,4-disubstituted quinolines.[8] FeCl3-catalyzed
A3-coupling of aniline, alkyne and aldehyde to provide 2,4-
Subsequently, Fe-catalyzed synthesis of 4-arylquinolines
disubstituted quinolines,[9] and metal clay based catalysts has
from aryl methyl ketones and aryl amine was reported by
also been reported.[10] All these methods are only applicable
Jadhav and Singh (scheme 1b).[12] Co(III)-catalyst based C-
H activation approches have also been utilized for the
synthesis of 4-arylated quinolines.[13] First approch includes
[a]
Mr. Devesh Chandra, Mr. Ankit Kumar Dhiman, Mr. Rakesh
Kumar, Prof. Dr. Upendra Sharma*
annulation of aryl methyl ketones and aryl amines using
o
Natural Product Chemistry & Process Development Division
and AcSIR, CSIR-IHBT, Palampur, Himachal Pradesh 176061,
India
E-mail: *upendra@ihbt.res.in; upendraihbt@gmail.com
Homepage: http://www.ihbt.res.in/en/staff/scientific-
staff?chronoform=sctdetail&task=detail&id=41
paraformaldehyde as the CO surrogate at 130 C (Scheme
1a).[13a] Later, Yi et al. utlizes alkyne as coupling partner with
aniline and DMSO as CO surrogate for the synthesis of 4-
substuted quinolines at 120oC (Scheme 1c).[13b] Co(III)-
catalyzed annulation of anilides with internal alkynes to form
3,4-diarylated quinolines has also been disclosed by Zhang[14]
and Li[15] group independently. The removal of trace metal
Supporting information and ORCID(s) from the author(s) for
this article for this article is given via a link at the end of the
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10.1002/ejoc.201900325
European Journal of Organic Chemistry
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impurities from the final product particularly in
We screened different organic acids, i.e., pivalic acid,
adamantane carboxylic acid, p-toluene sulfonic acid, triflic
acid, and (±) camphor-10-sulfonic acid (CSA) for carrying out
this transformation. This screening revealed CSA as the
organic molecule of choice for promoting the formation of
desired product 3aa. Further screening of solvents provided
TFE as an ideal solvent for the formation of 3aa (89% yield.
Table 1).
pharmaceuticals can increase the overall process cost.[16]
.
Metal-free approaches are also described for the synthesis of
aryl-substituted quinolines.[17] In this regard, recently Tiwari et.
al.,[17c] developed a K2S2O8 promoted metal-free protocol for
the synthesis of quinoline via annulation of aniline and alkynes.
(Scheme 1d). However use of excess K2S2O8 limits the scope
of this approach. In addition, long reaction time and high
reaction temperature in all these reactions warrant further
intervention.
Traditionally, Povarov reaction[18] i.e. [4+2] cycloaddition of
imines and olefins is a most anticipated method for the
synthesis of substituted N-heterocycle. However, terminal
alkynes and paraformaldehyde are rarely used in Povarov
type reactions for 4-substituted quinolines synthesis.[19] On the
other hand, mainly inorganic lewis acids[20] are known to
promote this type of reaction, but the organic acid are rarely
explored.[21] Intrestingly, acceleration of chemical reactions by
organic molecules constitute a vibrant area in organic
chemistry due to their ease of handling, stability, and
environmental friendliness.[22]
Under best optimal reaction conditions various substituted
anilines (1a-1p) were allowed to couple with phenyl acetylene
(2a, Table 2). Anilines substituted at ortho-position with
halogen, electron withdrawing and electron donating groups
(1a-1g) provided C8-substituted quinolines in low to excellent
yields (3aa-3ga, 23-88%). The meta-substituted anilines (1h,
1i) also reacted with 2a providing a regio-isomeric mixture of
products (3ha, 3ia).
Table 2. Substrate scope with anilines.a
Hence, in continuation of our group’s research interest in
the development of the methodologies for synthesis and
functionalization[23] of quinolines, herein we describe a
Povarov type multicomponent reaction for the synthesis of 4-
substituted quinoline using (±) camphor-10-sulfonic acid
(CSA) as the promotor.
Result and discussion
Initially, phenyl acetylene (0.1 mmol), aniline (0.12 mmol)
and paraformaldehyde (0.125 mmol) were selected as model
substrates and reacted under microwave irradiation at 90°C.
Instead of desired 4-phenyl quinoline (3aa), troger’s base[24]
(A) was formed in good amount.
Table 1. Optimization study.a
Entry
1
Deviation from standard conditions
no deviation
Yieldb (%)
89
2
3
4
5
without CSA
ndc
nd
45
24
without (HCHO)n
aReaction conditions: anilines (1a-p; 0.36 mmol), alkynes (2a; 0.3 mmol),
paraformaldehyde (0.375 mmol), CSA (0.15 mmol), TFE (0.2 M), µW
irradiation, 90 °C, 20 min.; b30 min.
MeOH instead of TFE
CoCp*(CO)I2 instead of CSA
Similarly, the para-substituted anilines (1j-1n) were also
compatible affording the desired products in low to good yields
(3ja-3na, 32-90%). Disubstituted anilines such as 4-iodo-2-
nitroaniline (1o) and 2-amino-5,6,7,8-tetrahydronaphthalene
also reacted successfully albeit providing the corresponding
desired product in low yields (3oa and 3pa).
6
heating (24h) instead of µW
pivalic acid instead of CSA
triflic acid instead of CSA
46
40
68
32
<5
7
8
9
admantane carboxylic acid instead of CSA
PTSA instead of CSA
10
Next, various alkynes were reacted with ortho-toluidine (1b)
(Table 3). Different para-substituted phenyl acetylenes (2a-
2g) were well tolerated under optimal reaction conditions and
provided the desired products in 31-76% yields (3ba-bg). The
aReaction conditions: anilines (1a; 0.12 mmol), alkynes (2a; 0.1 mmol),
paraformaldehyde (0.125 mmol), CSA (0.05 mmol), TFE (0.2M), µW
irradiation, 90 °C, 20 min.bGC yields by using n-decane as internal standard.
cTroger's base A was formed
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10.1002/ejoc.201900325
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polyaromatic alkyne (2h) also gave the desired product (3bh)
in good yield. Although 3-ethynylthiophene provided the
desired product 3bi in 48% of yield, 2-ethynylpyridine failed to
react. Internal alkyne did not react under current reaction
conditions. Further, we examined different aldehydes (4a-4c)
as a substitute of paraformaldehyde. Benzaldehyde and
furfural were found suitable substrates but acetaldehyde
CN) with 1a provides corresponding products in 1:3 ratio
(Scheme 2f).[24] These experiments disclosed that imine with
electron donating group and alkyne with electron withdrawing
group favors the annulations for the synthesis of 4-arylated
quinolines.
failed to react.
Table 3. Substrate scope with alkynes.a
Scheme 2. Control Experiments.
On the basis of thses experiments and literature,[17a, 20c]
plausible reaction mechanism for the synthesis of 4-arylated
quinoline is proposed (Scheme 3).
a
aReaction conditions: anilines (1a-b; 0.36 mmol), alkynes (2a-k; 0.3 mmol),
paraformaldehyde (0.375 mmol), CSA (0.15 mmol), TFE (0.2 M), µW
irradiation, 90 °C, 20 min. b30 min.
For the preliminary understanding of the reaction pathway,
few experiments were carried out. The standard reaction as
well as the reaction between aniline and paraformaldehyde
without CSA afforded troger’s base as the only product
(Scheme 2a and 2b). These reactions confirm the role of CSA
in promoting the reaction via inhibiting the formation of the
troger’s base. The reaction of N-(4-methoxyphenyl)-1-
phenylmethanimine (II) with 2a, in the presence of CSA, afford
the product B in 32% yield whereas no product was observed
without CSA (Scheme 2c and 2d). These two experiments
confirm imine (II) as possible intermediate and the role of CSA
in promoting cycloaddition between imine and alkynes via
activating imine. Furthermore, a competition experiment
between 1j (p-Me) and 1q (p-CN) with 2a provides the
corresponding products in 7:1 ratio (Scheme 2e); on the other
hand, competition experiment between 2b (p-Me) and 2l (p-
Scheme 3. Plausible mechanism for quinolines synthesis.
The reaction may proceed through the formation of in situ
generated intermediate I from the condensation of aniline and
paraformaldehyde. Cycloaddition of 2a with CSA activated
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7.40 (d, J = 7.5 Hz, 1H), 7.33–7.36 (m, 1H), 2.88 (s, 3H) ppm; 13C
NMR (75 MHz, CDCl3)  = 148.86, 148.84, 147.9, 138.7, 137.5,
129.73 , 129.67, 128.6 , 128.4, 126.9, 126.4, 124.1, 121.3, 18.8 ppm;
IR (ZnSe): νmax = 3033, 2920, 1587, 1489, 1402, 1350, 1091, 852, 767,
702 cm-1; HRMS (ESI-TOF): m/z [M+H]+ calcd for C16H14N 220.1121,
found 220.1111.
imine (II) via a Povarov type multicomponent reaction afforded
intermediate IV, which on spontaneous oxidation yield the
final product 3aa.
Conclusions
8-fluoro-4-phenylquinoline (Table 1, entry 3ca). White crystal (59
mg, 88%). m.p. 81.8-82°C. 1H NMR (600 MHz, CDCl3):  = 9.00 (d, J
= 3.6 Hz, 1H), 7.76-7.66 (m, 1H), 7.57-7.51 (m, 3H), 7.52-7.49 (m, 2H),
7.46-7.40 (m, 3H) ppm; 13C NMR (150 MHz, CDCl3)  = 150.1, 148.5,
137.8, 129.6, 128.8, 128.8, 122.5, 121.8, 113.5, 113.4 ppm; 19F NMR
(565 MHz, CDCl3):  = 124.8. IR (ZnSe): νmax = 3033, 2916, 1562,
1489, 1402, 1392, 1068, 877, 694 cm-1. HRMS (ESI-TOF): m/z [M+H]+
calcd for C15H11N 224.0870, found 224.0860.
In summary, we have developed a rapid microwave-assisted
metal-free method for the synthesis of 4-substituted
quinolines by using an organic molecule as an acid promotor.
Experimental Section
General Methods
8-chloro-4-phenylquinoline (Table 1, entry 3da). Yellow liquid (49
mg, 69%). 1H NMR (600 MHz, CDCl3)  = 9.07 (d, J = 4.2 Hz, 1H),
7.84-7.87 (m, 2H), 7.51-7.55 (m, 3H), 7.47-7.49 (m, 2H), 7.40-7.43 (m,
2H); 13C NMR (150 MHz, CDCl3)  = 150.6, 149.3, 145.1, 137.8, 134.0,
129.67, 129.66 (2C), 128.82, 128.80(2C) 128.4, 126.5, 125.3, 122.4;
IR (ZnSe): νmax (cm-1) 3036, 2922, 1585, 1489, 1444, 1386, 1033, 856,
761; HRMS (ESI-TOF): m/z [M+H]+ calcd for C15H11ClN, 240.0475
found 240.0560.
Reagent Information: All experiments were performed in CEM
Discover using SynergyTM software. High-resolution mass spectra
were recorded by Q-TOF using the electrospray ionization (ESI-TOF)
method. All chemicals were purchased from the Sigma-Aldrich and
TCI. TLC plates (Aluminium sheet silica gel 60 F254) were purchased
from Merck. Flash chromatography was performed over silica gel
(230−400 mesh) using n-hexane and ethyl acetate as eluents.
8-bromo-4-phenylquinoline (Table 1, entry 3ea). Yellow liquid (52
mg, 62%). 1H NMR (600 MHz, CDCl3)  = 9.07 (d, J = 4.8 Hz, 1H),
8.07 (dd, J = 7.2 Hz, J = 1.2 Hz 1H), 7.88 (dd, J = 8.4 Hz, J = 1.2 Hz
1H), 7.50-7.54 (m, 3H), 7.46-7.48 (m, 2H), 7.40 (d, J = 4.2 Hz, 1H),
7.34 (t, J = 7.8 Hz 1H) ppm; 13C NMR (150 MHz, CDCl3)  = 150.8,
149.4, 145.8, 137.7, 133.3, 129.7, 128.79, 128.77 , 128.4, 127.0,
126.1, 125.4, 122.3 ppm; IR (ZnSe): νmax () 3036, 2922, 1585, 1489,
1444, 1386, 1033, 856, 761 cm-1. HRMS (ESI-TOF): m/z [M+H]+ calcd.
for C15H11BrN 284.0069, found 284.0052.
Analytical Information: The melting points were recorded on a
Bronsted Electro thermal 9100. All isolated compounds are
1
characterized by H NMR, 13C NMR, LC–MS, and IR. In addition, all
of the compounds are further characterized by HRMS. Mass spectra
were recorded on Water Q-ToF Micro mass spectrometer. IR was
analyzed by Shimadzu IR Prestige-21with ZnSe Single reflection ATR
accessory. Nuclear magnetic resonance spectra were recorded on a
Bruker-Avance 600 or 300 MHz instrument. All 1H NMR experiments
are reported in units, parts per million (ppm), and were measured
relative to the signals for residual chloroform (7.26). All 13C NMR
spectra were reported in ppm relative to deuterated chloroform (77.23)
4-phenylquinoline-8-carbonitrile (Table 1, entry 3fa). White crystal
(46 mg, 67%); m.p. 138-139.8 °C. 1H (600 MHz, CDCl3)  = 9.16 (d, J
= 4.2 Hz, 1H), 8.21-8.17 (m, 2H), 7.65- 7.55 (m, 4H), 7.55-7.48 (m,
3H) ppm; 13C NMR (150 MHz, CDCl3)  = 152.1, 149.3, 148.2, 135.6,
131.3, 129.6, 129.1, 129.0, 127.0, 125.9, 123.0, 117.6ppm. IR (ZnSe):
νmax () 2922, 2225, 1745, 1556, 1282, 1033, 798, 653 cm-1. HRMS
(ESI-TOF): m/z [M+H]+ calcd. for C16H11N2 231.0917, found 231.0923.
1
and all were obtained with H decoupling. Optimization studies were
done by GC by using n-decane as an internal standard.
General Procedure for Synthesis of 4-substituted
quinolines: To a solution of phenylacetylene (0.3 mmol) in TFE
(0.2M), paraformaldehyde (0.375 mmol) aniline (0.36 mmol) and (±)
camphor-10-sulfonic acid (0.15 mmol) were added in a glass reaction
tube with sealed cap and irradiate with microwave in CEM Discover
using SynergyTM software for 20 min. or until the full conversion
monitored by standard monitoring tools i.e TLC at 100 °C. The crude
reaction mixture was concentrated at reduced pressure. Isolation and
purification were done by flash chromatography using n-hexane and
ethyl acetate mixture as an eluent.
4,8-diphenylquinoline (Table 1, entry 3ga). White solid (19 mg,
1
23%); m.p. 252-253 °C. H NMR (600 MHz, CDCl3)  = 8.97 (d, J =
4.8 Hz, 1H), 7.92 (d, J = 8.4 Hz, 1H), 7.71-7.74 (m, 3H), 7.50-7.56
(m,8H), 7.43 (t, J = 7.2 Hz, 1H), 7.35 (d, J = 4.2 Hz, 1H) ppm; 13C NMR
(150 MHz, CDCl3)  =149.8, 148.7, 146.6, 141.4, 140.1, 138.6, 130.8
(2C), 130.4, 129.8, 128.7, 128.5, 128.1, 127.5, 127.4, 126.3, 125.8,
121.4 ppm. IR (ZnSe): νmax = 3031, 1563, 1480, 1394, 1287, 1156,
1070, 840, 765, 700 cm-1. HRMS (ESI-TOF): m/z [M+H]+ calcd. for
C21H16N 282.1277, found 282.1280.
Characterization data
4-phenylquinoline (Table 1, entry 3aa). Yellow liquid (78 mg, 78%);
1H NMR (300 MHz, CDCl3):  = 8.95 (d, J = 4.2 Hz, 1H), 8.18 (d, J =
8.4 Hz, 1H), 7.93 (d, J = 8.4 Hz, 1H), 7.71-7.76 (m, 1H), 7.48-7.53 (m,
6H), 7.34 (d, J = 4.2 Hz, 1H) ppm; 13C NMR (75 MHz, CDCl3):  =
150.1, 148.8, 148.7, 138.1, 129.9, 129.7(2C), 129.5, 128.7(2C), 128.6,
126.9, 126.8, 126.0, 121.5 ppm. IR (ZnSe): νmax = 3055, 2925, 1573,
1490, 1390, 1276, 1029, 850, 767, 655 cm-1. HRMS (ESI-TOF): m/z
[M+H]+ calcd. for C15H12N 206.0964, found 206.0951.
Regioisomeric mixture of 7-methyl-4-phenylquinoline and 5-
methyl-4-phenylquinoline (Table 1, entry 3ha). Yellow liquid (28 mg,
42%, a:b :: 1:2.5). 1H NMR (600 MHz, CDCl3) (isomer a)  = 8.90 (d,
J = 4.2 Hz, 1H), 7.95 (s, 1H), 7.81 (d, J = 8.4 Hz, 1H), 7.48-7.54 (m,
5H), 7.29 (d, J = 7.8 Hz, 2H), 7.21 (d, J = 4.2 Hz, 2H), 2.58 (s, 3H)
ppm ;13C NMR (150 MHz, CDCl3):  = 149.7, 148.8, 148.6, 142.4,
135.7, 129.9, 128.9, 128.8, 127.9, 127.8, 126.3, 123.5, 24.5 ppm; 1H
NMR (600 MHz, CDCl3) (isomer b):  = 8.86 (d, J = 4.2 Hz, 1H), 7.60
(t, J = 7.8 Hz, 1H), 7.46-7.42 (m, 3H), 7.34-7.32 (m, 3H), 2.02 (s, 3H);
13C NMR (150 MHz, CDCl3) (isomer b):  = 149.9, 149.0, 139.6, 138.1,
129.5, , 128.9, 128.6, 128.5, 128.3, 127.9, 125.5, 124.7, 120.6, 19.6
8-methyl-4-phenylquinoline (Table 1, entry 3ba). Pale yellow liquid
(50 mg, 76%); 1H NMR (300 MHz, CDCl3)  = 8.98 (d, J = 4.2 Hz, 1H),
7.76 (d, J = 8.4 Hz, 1H), 7.59 (d, J = 6.3 Hz, 1H), 7.48-7.53 (m, 5H),
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10.1002/ejoc.201900325
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ppm. IR (ZnSe): νmax = 2928, 1632, 1575, 1459, 1244, 1196, 827, 759,
700 cm-1. HRMS (ESI-TOF): m/z M+H]+ calcd. for C16H14N 220.1121,
found 220.1112.
113.7 ppm; 19F NMR (565 MHz, CDCl3)  = -62.25 ppm. IR (ZnSe):
νmax = 2981, 2922, 2864, 1726, 1587, 1309, 1163, 1055, 1012, 812,
761, 702 cm-1. HRMS (ESI-TOF) m/z [M+H]+ calcd for C16H11CF3N
240.0575, found 240.0570.
Regioisomeric mixture of 7-methyl-4-phenylquinoline and 5-
methyl-4-phenylquinoline (Table 1, entry 3ia). Pale yellow liquid (21
mg, 30%) (a: b :: 1: 1.3). 1H NMR (600 MHz , CDCl3): (isomer a):  =
8.94 (d, J = 4.2 Hz, 1H), 8.17 (d, J = 1.8 Hz, 1H), 7.86 (d, J = 9.0 Hz,
1H), 7.49-7.47 (m, 2H), 7.42-7.43 (m, 4H) 7.31 (d, J = 4.2 Hz, 1H)
ppm; 13C NMR (CDCl3, 150 MHz):  = 151.0, 149.1, 148.6, 140.8,
137.5, 135.3, 129.5, 128.93, 128.73, 127.6, 127.3, 125.2, 121.5 ppm;
1H NMR (600 MHz, CDCl3) (isomer b):  = 8.91 (d, J = 4.8 Hz, 1H),
8.14 (dd, J = 8.4, 1.2 Hz, 1H), 7.25-7.64 (m, 1H), 7.58 (dd, J = 7.2, 1.2
Hz, 1H), 7.50-7.56 (m, 3H), 7.33-7.35 (m, 3H) ppm; 13C NMR (150
MHz, CDCl3):  = 150.1, 149.6, 148.3, 140.8, 130.8, 129.7, 128.9,
6-iodo-8-nitro-4-phenylquinoline (Table 1, entry 3oa). Orange solid
1
(36 mg, 32%); m.p. 102-104°C. H NMR (300 MHz, CDCl3)  = 9.07
(d, J = 4.2 Hz, 1H), 8.45 (s, 1H), 8.22 (s, 1H), 7.57-7.59 (m, 3H), 7.45-
7.49 (m, 3H) ppm.13C NMR (75 MHz, CDCl3)  = 152.4, 149.1, 147.9,
139.3, 138.7, 136.4, 131.7, 129.56 (2C), 129.52, 129.3(2C), 123.7,
88.8 ppm. HRMS (ESI-TOF) m/z [M+H]+ calcd. for C15H10IN2O2
376.9781, found 376.9790.
4-phenyl-6,7,8,9-tetrahydrobenzo[g]quinoline (Table 1, entry 3pa).
1
Reddish brown liquid (20 mg, 26%). H NMR (600 MHz, CDCl3)  =
129.65, 128.72, 127.7, 124.9, 124.6, 121.5 ppm. IR (ZnSe): νmax
=
8.94 (d, J = 4.8 Hz, 1H), 7.64 (d, J = 8.4, 1H), 7.47-7.53 (m, 5H), 7.29
(d, J = 4.2 Hz, 1H), 7.23 (d, J = 8.4 Hz, 1H), 3.39-3.41 (m, 3H), 2.93-
2.96 (m, 3H), 1.97-2.00 (m, 2H), 1.89-1.94 (m, 2H) ppm; 13C NMR (150
MHz, CDCl3)  = 148.8, 148.5, 147.5, 138.7, 138.4, 134.9, 129.7,
129.1, 128.6, 128.4, 125.0, 122.9, 120.7, 30.5, 25.4, 23.2, 23.0ppm.
IR (ZnSe): νmax = 2927, 2862, 1668, 1435, 1278, 1155, 1028, 968, 781,
700, 675 cm-1. HRMS (ESI-TOF): m/z [M+H]+ calcd. for C19H18N
260.1434, found 260.1450.
3036, 2922, 1585, 1489, 1444, 1386, 1033, 856, 761 cm-1. HRMS
(ESI-TOF) m/z [M+H]+ calcd. for C15H11ClN 240.0575, found
240.0560.
6-methyl-4-phenylquinoline (Table 1, entry 3ja). Orange liquid (59
mg, 90%). 1H NMR (300 MHz, CDCl3)  = 8.87 (d, J = 4.5 Hz, 1H),
8.07 (d, J = 8.7 Hz, 1H), 7.66 (s, 1H), 7.48-7.54 (m, 6H), 7.28 (d, J =
4.5 Hz, 1H), 2.46 (s, 3H) ppm; 13C NMR (75 MHz, CDCl3)  = 150.2,
148.1, 147.1, 137.5, 132.8, 131.6, 130.5, 129.6, 128.96, 128.91, 127.7,
124.8, 122.2, 21.9; IR (ZnSe): νmax () 2922, 1622, 1574, 1462, 1244,
1190, 827, 759, 700 cm-1. HRMS (ESI-TOF): m/z [M + H]+ calcd. for
C16H14N 220.1121, found 220.1109.
8-methyl-4-(p-tolyl)quinoline (Table 2, entry 3bb). Yellow liquid (28
mg, 42%). 1H NMR (600 MHz, CDCl3)  = 8.96 (d, J = 4.2 Hz, 1H),
7.79 (d, J = 8.4 Hz, 1H), 7.58 (d, J = 7.2 Hz, 1H), 7.37-7.40 (m, 3H),
7.32-7.34 (m, 3H), 2.87 (s, 3H), 2.47 (s, 3H) ppm; 13C NMR (150 MHz,
CDCl3):  = 148.8, 148.8, 147.9, 138.3, 137.5, 135.7, 129.7, 129.6,
6-fluoro-4-phenylquinoline (Table 1, entry 3ka). Yellow liquid (31 mg,
47%). 1H NMR (600 MHz, CDCl3):  = 8.91 (d, J = 4.8 Hz, 1H), 8.16-
8.19 (m, 1H), 7.47-7.55 (m, 7H), 7.36 (d, 3.6Hz, 1H) ppm; 13C NMR
(150 MHz, CDCl3)  = 161.6, 159.9, 149.4, 148.2, 145.9, 137.7, 132.5,
132.4, 129.5, 128.9, 128.8, 127.8, 127.7, 121.9, 119.8, 119.6ppm. IR
(ZnSe): νmax = 2924, 1622, 1564, 1492, 1242, 914, 700, 613 cm-1.
HRMS (ESI-TOF): m/z [M + H]+ calcd. for C15H11FN 224.0870, found
224.0883.
129.3, 127.0, 126.3, 124.2, 121.3, 21.4, 18.8 ppm. IR (ZnSe): νmax
=
3369, 2927, 1610, 1498, 1450, 1398, 1276, 1111, 1037, 819, 765, 723
cm-1. HRMS (ESI-TOF) m/z [M+H]+ calcd. for C17H16N 234.1277,
found 234.1289.
4-(4-bromophenyl)-8-methylquinoline (Table 2, entry 3bc). Yellow
liquid (29 mg, 32%). 1H NMR (600 MHz, CDCl3):  = 8.97 (d, J = 4.3
Hz, 1H), 7.71-7.67 (m, 1H), 7.65 (d, J = 8.3 Hz, 1H), 7.59 (dt, J = 7.0,
1.3 Hz, 1H), 7.40 (dd, J = 8.4, 7.0 Hz, 1H), 7.37 (d, J = 8.4 Hz, 1H),
7.30 (d, J = 4.3 Hz, 1H), 2.87 (s, 3H) ppm; 13C NMR (150 MHz, CDCl3)
 = 148.8, 148.8, 147.9, 138.3, 137.4, 135.6, 129.6, 129.6, 129.3,
127.0, 126.2, 124.1, 121.3, 21.4, 18.8 ppm. IR (ZnSe): νmax () 2930,
1668, 1593, 1483, 1406, 1390, 1274, 1072, 1008, 825, 800, 765, 721
cm-1. HRMS (ESI-TOF): calcd m/z [M+H]+ for C16H13BrN 298.0026,
found 298.0218.
6-chloro-4-phenylquinoline (Table 1, entry 3la). Yellow solid (52 mg,
72%); m.p. 66.2- 66.8°C. 1H NMR (600 MHz, CDCl3)  = 8.94 (d, J =
4.8 Hz, 1H), 8.12 (d, J = 9.0 Hz, 1H), 7.89 (d, J = 1.8 Hz, 1H), 7.67 (dd,
J = 9.0, 2.4 Hz, 1H), 7.52-7.57 (m, 3H), 7.48-7.49 (m, 3H), 7.37 (d, J
= 4.8 Hz, 1H) ppm; 13C NMR (150 MHz, CDCl3)  = 150.2, 148.1, 147.1,
137.5, 132.8, 131.6, 130.5, 129.6,128.96, 128.91, 127.7, 124.8,
122.2. IR (ZnSe): νmax = 2920, 16.6, 1583, 1489, 1352, 1155, 1076,
970, 773, 698 cm-1. HRMS (ESI-TOF): [M+H]+ m/z calcd. for
C15H11ClN 240.0575, found 240.0570.
4-(4-methoxyphenyl)-8-methylquinoline (Table 2, entry 3bd).
Yellow liquid (29 mg, 40%). 1H NMR (600 MHz, CDCl3):  = 8.96 (d, J
= 4.2 Hz, 1H), 7.81 (d, J = 8.4 Hz, 1H), 7.58 (d, J = 7.2 Hz, 1H), 7.44
(d, J = 8.4 Hz, 2H), 7.41-7.37 (m, 1H ), 7.05 (d, J = 9.0 Hz, 2H), 3.90
(s, 3H), 2.87 (s, 3H) ppm; 13C NMR (150 MHz, CDCl3)  = 159.9, 148.7,
130.9, 130.8, 129.6, 129.3, 127.0, 126.2, 124.1, 121.2, 114.3, 114.1,
55.5, 18.8 ppm. IR (ZnSe): νmax = 2958, 1648, 1483, 1367, 1224,
1145,760, 720 cm-1. HRMS (ESI-TOF): m/z [M+H]+ calcd. for
C17H16NO 250.1226, found 250.1204.
6-iodo-4-phenylquinoline (Table 1, entry 3ma). Yellow solid (63 mg,
1
64%); m.p. 99.0-99.4°C. H NMR (600 MHz, CDCl3)  = 8.94 (d, J =
4.2 Hz, 1H), 8.28 (d, J = 1.8 Hz , 1H), 7.97 (dd, J = 9.0, 1.8 Hz, 1H),
7.91 (d, J = 9.0 Hz, 1H), 7.53-7.57 (m, 3H), 7.48-7.49 (m, 2H), 7.35 (d,
J = 4.2 Hz, 1H) ppm; 13C NMR (150 MHz, CDCl3)  = 150.4, 147.8,
147.6, 138.4, 137.4, 134.8, 131.5, 129.6, 128.98, 128.94, 128.7, 122.1,
92.9 ppm; IR (ZnSe) νmax () : 2926, 1479, 1348, 1149, 1033, 964, 819,
702, 617 cm-1. HRMS (ESI-TOF) m/z [M+H]+ calcd. for C15H11IN
331.9931, found 331.9942.
4-(4-(tert-butyl) phenyl)-8-methylquinoline (Table2, entry 3be).
1
White solid (96 mg, 70%); m.p. 126.0- 127.0°C. H NMR (600 MHz,
CDCl3):  = 8.97 (d, J = 4.2 Hz, 1H), 7.83 (d, J = 8.4 Hz, 1H), 7.58 (d,
J = 7.2 Hz, 1H), 7.54 (d, J = 7.8 Hz, 2H), 7.45 (d, J = 8.4 Hz, 2H), 7.38-
7.40 (m, 1H), 7.34 (d, J = 4.8 Hz, 1H), 2.87 (s, 3H), 1.41 (s, 9H); 13C
NMR (150 MHz, CDCl3)  = 151.5, 148.89, 148.84, 147.9, 137.4, 135.6,
129.6, 129.5, 127.0, 126.2, 125.6, 124.3, 121.3, 34.9, 31.5, 18.9 ppm.
IR (ZnSe): νmax = 2953, 2922, 1680, 1500, 1363, 1269, 1109, 833, 771
4-phenyl-6-(trifluoromethyl) quinoline (Table 1, entry 3na). Yellow
1
liquid (29 mg, 32%). H NMR (600 MHz, CDCl3)  = 9.13 (d, J = 4.2
Hz, 1H), 8.17-8.33 (d, J = 8.4 Hz, 1H), 8.27 (s, 1H), 7.93 (d, J = 10.7
Hz, 1H), 7.65-7.56 (m, 3H), 7.53 (d, J = 8.0 Hz, 2H), 7.48 (d, J = 4.4
Hz, 1H) ppm; 13C NMR (150 MHz, CDCl3)  = 152.2, 149.7, 148.2,
136.9, 135.6, 131.3, 129.6, 129.2, 129.0, 127.0, 125.9, 123.0, 117.7,
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10.1002/ejoc.201900325
European Journal of Organic Chemistry
FULL PAPER
cm-1. HRMS (ESI-TOF): m/z [M+H]+ calcd. for C20H22N 276.1747,
found 276.1759.
(ZnSe): νmax = 1591, 1573, 1492, 1409, 1008, 883, 632, 698 cm-1;
HRMS (ESI-TOF): m/z [M+H]+ calcd. for C19H14NO 272.1070, found
272.1054.
8-methyl-4-(4-phenoxyphenyl) quinoline (Table2, entry 3bf).
Yellow liquid (48 mg, 31%). 1H NMR (600 MHz, CDCl3)  = 8.97 (d, J
= 4.2 Hz, 1H), 7.81 (d, J = 8.4 Hz, 1H), 7.58 (d, J = 7.2 Hz, 1H), 7.46
(d, J = 8.4 Hz, 2H), 7.39-7.42 (m, 3H), 7.33 (d, J = 4.2 Hz, 1H), 7.13-
7.19 (m, 5H), 2.88 (s, 3H) ppm; 13C NMR (150 MHz, CDCl3)  = 157.8,
156.7, 148.7, 148.1, 147.8, 137.4, 133.1, 131.1, 129.9, 129.6, 126.8,
126.3, 123.91, 123.86, 121.2, 119.5, 118.4, 18.7 ppm; IR (ZnSe): νmax
2951, 2922, 1672, 1587, 1487, 1396, 1232, 1166, 767, 748, 692 cm-1.
HRMS (ESI-TOF): m/z [M+H]+ calcd. for C22H18NO 312.1383, found
311.6693.
6H,13H-5,12-methano[1,3]dioxolo[4',5':4,5]benzo[1,2
b][1,3]dioxolo[4',5':4,5]benzo[1,2-f][1,5]diazocine (Scheme 1, A1).
1H NMR (600 MHz, CDCl3)  = 6.61 (s, 2H), 6.34 (s, 2H), 5.86 (d, J =
1.2 Hz, 2H), 5.83 (d, J = 1.2 Hz, 2H), 4.54 (d, J = 16.4 Hz, 2H), 4.22
(s, 2H), 3.97 (d, J = 16.4 Hz, 2H) ppm; 13C NMR (150 MHz, CDCl3) 
= 146.8, 144.6, 141.6, 120.0, 105.9, 105.6, 100.9, 67.1, 58.4 ppm.
Acknowledgements
8-methyl-4-(4-pentylphenyl) quinoline (Table2, entry 3bg).
1
Authors thanks Director, CSIR-IHBT for continuous
encouragement and providing necessary facilities. D.C. and
R.K. acknowledge DST and UGC, New Delhi, respectively, for
the research fellowship. Financial support from CSIR
(MLP0148/HCP010) is also acknowledged. CSIR-IHBT
communication no. for this manuscript is 0000.
Colourless liquid (88 mg, 61%). H NMR (600 MHz, CDCl3)  = 8.96
(d, J = 4.2 Hz, 1H), 7.81 (d, J = 7.8 Hz, 1H), 7.58 (d, J = 7.2 Hz, 1H),
7.37-7.42 (m, 3H), 7.33 (dd, J = 6.6, 1.8 Hz, 3H), 2.88 (s, 3H), 2.71 (t,
J = 7.8 Hz ,2H), 1.68-1.74 (m, 2H), 1.40 (dq, J = 7.2, 3.6 Hz, 4H), 0.94
(t, J = 7.2 Hz, 3H) ppm; 13C NMR (150 MHz, CDCl3)  = 148.9, 148.8,
147.9, 143.4, 137.4, 135.8, 129.64, 129.60, 128.6, 126.9, 126.2, 124.2,
121.3, 35.9, 31.7, 31.3, 22.7, 18.8, 14.2 ppm; IR (ZnSe): νmax = 2922,
2868, 1680, 1496, 1398, 1118, 817, 765, 732 cm-1; HRMS (ESI-TOF):
m/z [M+H]+ calcd. for C21H24N 290.1903, found 290.1893.
Keywords: Quinoline; alkyne; (±) camphor-10-sulfonic acid;
Povarov type multicomponent reaction; Microwave synthesis
8-methyl-4-(phenanthren-9-yl) quinoline (Table 2, entry 3bh).
1
Colourless liquid (46 mg, 48%); H NMR (600 MHz, CDCl3)  = 9.10
(d, J = 4.2 Hz, 1H), 8.82 (d, J = 8.4 Hz, 1H), 8.79 (d, J = 8.4 Hz, 1H),
7.91 (d, J = 8.4 Hz, 1H), 7.74 (t, J = 7.2 Hz, 2H), 7.65-7.68 (m, 2H),
7.58 (d, J = 7.2, 1H), 7.49 (d, J = 4.2 Hz, 1H), 7.41 -7.43 (m, 1H), 7.35-
7.39 (m, 2H), 7.23-7.25 (m, 1H), 2.94 (s, 3H) ppm; 13C NMR (150 MHz,
CDCl3)  = 148.9, 147.71, 147.65, 137.5, 134.9, 131.4, 131.3, 130.6,
130.5, 129.9, 128.9, 128.32, 128.28, 127.3, 127.23, 127.16, 126.96,
126.94, 126.49, 124.7, 123.1, 122.8, 122.51, 18.7 ppm; IR (ZnSe):
νmax = 3419, 3296, 1592, 1402, 1249, 1211, 1006, 758 cm-1; HRMS
(ESI-TOF): m/z [M+Na]+ calcd. for C24H18N 341.1175, found 342.7653.
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8-methyl-4-(thiophen-2-yl)quinoline (Table 2, entry 3bi). Yellow
solid (32 mg, 48 %; m.p. 76.0-77.0°C. 1H NMR (600 MHz, CDCl3):  =
8.95 (d, J = 4.2 Hz, 1H), 7.93 (d, J = 8.4 Hz, 1H), 7.59 (d, J = 6.6 Hz,
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8-methyl-2,4-diphenylquinoline (Table 3, entry 3aaa). Brown resin
(39 mg, 45%). 1H NMR (600 MHz, CDCl3):  = 8.30 (d, J = 7.2 Hz, 2H),
7.86 (s, 1H), 7.74 (d, J = 7.8 Hz, 1H), 7.60 (d, J = 7.2 Hz, 1H), 7.58-
7.50 (m, 7H), 7.49-7.45 (m, 1H), 7.39-7.33 (m, 1H), 2.97 (s, 3H) ppm;
13C NMR (150 MHz, CDCl3):  = 148.89, 148.85, 147.91, 138.31,
137.46, 135.69, 129.65, 129.61, 129.32, 127.00, 126.26, 124.19,
121.30, 21.43, 18.80 ppm. IR (ZnSe): νmax = 2918, 1591, 1554,
1485,1355, 1178, 1095, 1028, 763, 690 cm-1. HRMS (ESI-TOF): m/z
[M+H]+ calcd. for C22H18N 296.1434, found 296.1456.
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(42 mg, 52%). 1H NMR (600 MHz, CDCl3)  = 8.23 (d, J = 8.4 Hz, 1H),
7.89 (d, J = 8.3 Hz, 1H), 7.80 (s, 1H), 7.74 (t, J = 8.2 Hz, 1H), 7.65 (s,
1H), 7.58 (d, J = 4.3 Hz, 4H), 7.55 (dd, J = 8.4, 4.4 Hz, 1H), 7.47 (t, J
= 8.0 Hz, 1H), 7.26 (d, J = 3.4 Hz, 1H) ppm; 13C NMR (150 MHz,
CDCl3)  = 153.9, 149.3, 148.8, 148.7, 144.3, 138.3, 129.9, 129.9,
129.7, 128.7, 128.6, 126.4, 125.9, 125.9, 117.9, 112.4, 110.3 ppm. IR
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.
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FULL PAPER
Quinoline
Synthesis:
Three
Key Topic* Quinoline Synthesis
Devesh Chandra, Ankit Kumar Dhiman,
Rakesh Kumar, and Upendra Sharma*
component
reaction
of
Page No. – Page No.
aniline, alkynes
and
formaldehyde
under
Microwave-Assisted Metal-Free Rapid
Synthesis of C4-Arylated Quinolines
via Povarov Type Multicomponent
Reaction
microwave
irradiation promoted by CSA led to the formation of 4-arylated quinolines via Povarov
type reaction.
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