Regioselective Synthesis of C-3-Functionalized Quinolines via Hetero-Diels-Alder Cycloaddition of Azadienes with Terminal Alkynes

Article abstract of DOI:10.1021/acs.joc.6b01186

A highly efficient metal and protection-free approach for the regioselective synthesis of C-3-functionalized quinolines from azadienes (in situ generated from 2-aminobenzyl alcohol) and terminal alkynes through [4 + 2] cycloaddition has been developed. An unprecedented reaction of 2-aminobenzyl alcohol with 1,3- and 1,4-diethynylbenzene provided the C-3 tolylquinolines via [4 + 2] HDA and oxidative decarboxylation. The -NH₂ group directed mechanistic approach was well supported by the control experiments and deuterium-labeling studies and by isolating the azadiene intermediate. The reactivity and selectivity of unprotected azadiene in metal-free base-assisted hetero-Diels-Alder reaction is exploited to quickly assemble an important class of C-3-functionalized quinolines, which are difficult to access.

Full text of DOI:10.1021/acs.joc.6b01186

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Article
Regioselective Synthesis of C-3 Functionalized Quinolines via
Hetero Diels-Alder Cycloaddition of Azadienes with Terminal Alkynes
Rakesh K. Saunthwal, Monika Patel, and Akhilesh K. Verma
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.6b01186 • Publication Date (Web): 05 Jul 2016
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Regioselective Synthesis of C-3 Functionalized Quinolines
via Hetero Diels-Alder Cycloaddition of Azadienes with
Terminal Alkynes
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Rakesh K. Saunthwal, Monika Patel and Akhilesh K. Verma*
Synthetic Organic Chemistry Research Laboratory, Department of Chemistry,
University of Delhi, Delhi – 110007, India
Email: averma@acbr.du.ac.in
ABSTRACT: A highly efficient metal and protection-free approach for the regioselective synthesis of
C-3 functionalized quinolines from azadienes (in situ generated from 2-aminobenzyl alcohol) and
terminal alkynes through [4+2] cycloaddition has been developed. An unprecedent reaction of 2-
aminobenzyl alcohol with 1,3- and 1,4-diethynylbenzene provided the C-3 tolyl-quinolines via [4+2]
HDA and oxidative decarboxylation. The –NH2 group directed mechanistic approach was well
supported by the control experiments, deuterium labelling studies, and by isolating azadiene
intermediate. The reactivity and selectivity of unprotected azadiene in metal-free base-assisted hetero
diels alder (HDA) reaction is exploited to quickly assemble an important class of C-3 functionalized
quinolines, which are difficult to access.
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INTRODUCTION
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Quinolines are commonly occurring structural motifs found in numerous pharmaceuticals,1-2 and are
extensively used in drug discovery (Figure 1).3 The quinoline core structure can be synthesized by various
traditional methods such as Skraup reaction,4 Friedlaender synthesis,5 Combes quinoline synthesis,6
Larock quinolines synthesis7 and other8 quinoline synthesis. Alternatively the groups of Wang,9 Huang,10
and Kwon11 have demonstrated the transition-metal-catalyzed synthesis of C-3 functionalized quinolines
from o-substituted anilines. Very recently, Balaraman and fellow workers reported the Rh/dppm-catalyzed
synthesis of C-3 quinoline via C–H activation (Scheme 1a).12 The wide utility of these metal-catalyzed
processes is inconsistent for the base-mediated regioselective intermolecular [4+2] cycloaddition to
synthesize substituted quinolines.
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Figure 1 Biologically Active Quinoline Skeleton.
The [4+2] cycloaddition reactions of azadiene13 with electron-rich carbon-carbon triple bond are
a useful method for the synthesis of six-membered N-heterocyclic rings and have wide application in
natural product synthesis;14 however the low reactivity of alkynes as dienophiles has limited their
efficacy within the reaction. The metal-catalyzed regioselective intermolecular reactions of alkynes with
azadiene is well reported;15 however base promoted [4+2] annulation of terminal alkynes with in situ
generated azadiene is still challenging.
Scheme 1. Previous Synthetic Approaches and Our Designed Approach for the Synthesis of
Quinolines
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In last decades, Bergman,16 Jun,17 Cheng18 and Wang19 group elaborated the regioselective transition-
metal-catalyzed synthesis of pyridine via hetero diels alder reaction. In 2008, Arndt20 et al
demonstrated the [4+2] cycloaddition chemistry for the synthesis of pyridines at a higher temperature.
Later, Zimmer21 and co-workers investigated the Lewis acid-mediated cycloaddition process with both
electron-neutral and electron-rich dienophiles (Scheme 1b). An attractive strategy for the synthesis of
pyridines using azadiene motif was presented by Rovis group.22 In contrast to the synthesis of pyridines,
access of quinolines from azadienes remain elusive. In 2015, Ravikumar22e and co-workers have
developed an efficient protocol which utilizes the DMSO for the oxidation of benzyl alcohol to
benzaldehyde (Scheme 1c). The research activity of our group is mainly focused on the superbase-
mediated23 reactions and heterocyclic24 synthesis. Very recently we have explored the [4+2]
cycloaddition chemistry of 2-aminobenzyl alcohol with internal alkynes;24f herein we report an extended
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chemistry of C-3 functionalized quinolines via KOH-DMSO mediated [4+2] cycloaddition of azadiene
with terminal alkynes. We assumed that the direct synthesis of C-2 functionalized quinolines could
occur via KOH-DMSO promoted oxidation of 2-aminobenzyl alcohol into 2-aminobenzaldehyde
followed by the reaction with an alkyne, though designed pathway was unsuccessful (Scheme 1d, route
A and Scheme 7). We also visualized the regioselective synthesis of C-3 functionalized quinolines via
KOH-DMSO mediated [4+2] cycloaddition of azadiene (can be generated in situ from o-aminobenzyl
alcohol) with alkyne (Scheme 1d, route B).
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RESULTS AND DISCUSSION
In preliminary experiments, a number of acids and bases were examined using 2-aminobenzyl alcohol
1a and phenyl acetylene 2a as model substrates (Table 1). We carried out the reaction of 1a with alkyne
2a using HCl and BF3.OEt at 80 °C for 24 h, the product 3a was not obtained (entries 1–2). Using our
o
hydroamination condition;23 the desired product 3a was obtained in 65% yield at 120 C (entry 3).
Lowering the reaction temperature provided the product 3a in 68% yield (entry 4). Further decrease in
the reaction time and temperature provided the desired product 3a in 70 and 80% yields respectively at
90 oC (entries 5–6). Other alkali bases provided the desired product 3a in lower yield (entries 7–10) (for
detailed optimization, see supporting information).
Table 1. Reaction Developmenta
entry
acid/base
HCl
solvent
DMSO
DMSO
DMSO
DMSO
time (h)
24
temp (°C)
80
yield (%)b
N.R
1
2
3
4
BF3.OEt
KOH
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80
N.R
24
120
65
KOH
24
100
68
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KOH
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
20
16
16
16
16
16
90
90
90
90
90
90
70
80
75
65
63
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KOH
725
8
KtOBu
NaOH
CsOH
K3PO4
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aReactions were performed using 0.5 mmol of (2-aminophenyl) methanol 1a,
b
phenylacetylene 2a (0.4 mmol) and base/acid (1.0 equiv) in 2.0 mL of solvent
Isolated yield. N.R = no reaction
With optimized conditions in hand, we examined the substrate scope of the developed chemistry
by using a variety of alkyne 2a–q (Table 2). The reaction of substrate 1a, with phenyl acetylene 2a,
provided the desired product 3a in 80% yield (entry 1). The reaction proceeded well with alkynes 2b–g
bearing electron-donating groups such as p-Me, m-Me, o-Me, p-Et, p-nBu and p-tBu on the phenyl ring,
and afforded the desired products 3b–g in 81–84% yields (entries 2–7). Alkynes 2h–i with strong
electron-donating substituents such as –OMe, and –OPh afforded the corresponding quinoline
compounds 3h–i in 87 and 85% yields respectively (entry 8 and 9). When an electron-rich thienyl ring
was used for the reaction, the desired product 3j was obtained in 84% yield (entry 10). It was interesting
to note that under the optimized reaction condition, electron-deficient heteroaromatic alkynes 2k and
bulky 9-ethynylphenanthrene 2l also provided the targeted products 3k and 3l in 74 and 76% yields
respectively (entries 11 and 12). We further extended the scope of the developed protocol with electron-
withdrawing alkynes 2m–p, the desired products 3m–p were obtained in 68–73% yields with an
excellent regioselectivity (entries 13–16). Inseparable complex mixture was obtained in the reaction of
2-aminobenzylalcohol (1a) with 1-hexyne (2q) (entry 17). All the above results infer that the regio- and
chemoselectivity of the reaction depend on the electronic density distribution along the C–C triple
bond.26
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Table 2. Substrate Scope of the Alkynes.a,b
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entry
1
alcohol
alkyne
products
yields (%)b
80
2a
3a
3b
1a
1a
2
3
2b
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2c
2d
2e
2f
3c
3d
3e
3f
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2g
2h
3g
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2i
3i
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2j
2k
3j
3k
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1a
12
2l
3l
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14
2m
2n
3m
3n
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71
1a
1a
15
2o
3o
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1a
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17
2p
2q
3p
3q
1a
1a
c
-
aUsing optimized conditions (entry 6, Table 1). Isolated yield. Inseparable complex mixture. CCDC
b
c
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number for 3e is 1456743.
Next, we extended the substrate scope using varied of 2-aminobenzyl alcohols 1b–d as another coupling
partner (Table 3). The reaction of (2-amino-5-chlorophenyl)methanol 1b with alkynes 2a, 2e and 2k
provided the desire products 4a–c in good yields (entries 1–3). The reaction well accommodates the Br-
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substituted aminobenzyl alcohol 1c with alkynes 2a, 2c and 2g to give the desired products 4d–f in 72–
74% yields (entries 4–6). Further, reaction of (6-aminobenzo[d][1,3]dioxol-5-yl)methanol 1d with
alkynes 2j–k, 2a, 2e, 2g provided the regioselective C-3 functionalized quinolines 4g–k in good yields
(entries 7–11).
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Table 3. Substrate Scope of the o-Aminobenzyl Alcohols a
entry
1
alcohols
alkyne
products
yields (%)b
70c
2a
4a
4b
1b
1b
2
3
2e
73c
2k
2a
2c
4c
4d
4e
68c
72c
74c
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1c
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2g
2j
4f
72c
80
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4g
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1d
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2k
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4i
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4j
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1d
11
2f
4k
78
a Using optimized conditions (entry 6, Table 1). b Isolated yield. c 20 h for 4a–f
Encouraged by the above results, we next elaborate the substrate scope of the developed chemistry using
dialkynes (Scheme 2). It is interesting to note, the reaction of 1,3- and 1,4-diethynylbenzene 2q–r with
substrate 1a, provided the unexpected product 3b–c in 52% and 49% yields respectively along with
unidentified complex mixture.
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Scheme 2. Scope of Dialkynes
After attaining the successful results with 2-aminobenzyl alcohol (primary alcoholic group), we
next examine the scope of 1-(2-aminophenyl)ethan-1-ol 5 with terminal alkynes (Scheme 3). The
reaction of substrate 5 with electron-releasing alkyne 2k and electron-withdrawing alkyne 2p was
fruitful in affording the desired cycloaddition products 6a–b in moderate yields.
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Scheme 3. Scope of Secondary Alcohol
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Inspired by the previous literature condition22f-g we performed the reaction of benzylalcohol 7 with
KOH/DMSO at 90oC for 24 h; the methodology provided the oxidation of benzylalcohol 7 to
benzaldehyde 8 in 50% yield (Scheme 4).
Scheme 4. KOH/DMSO Promoted Oxidation
In order to support the proposed mechanistic pathway, various preliminary experiments were
performed (Scheme 5). For the validation of possible reaction pathway, we performed the reaction of 2-
aminobenzaldehyde 9 with alkyne 2a under optimized reaction condition, the quinoline 3a was not
observed (Scheme 5, i). We further examine the reaction of 1-(2-amino phenyl)ethanone 11 with 2a,
instead of quinoline 3a, 2-(4-methylquinolin-2-yl)aniline 12 (self condensation product of 11) was
obtained in 90% yield (Scheme 5, ii). For the confirmation of possible reaction intermediate, we
performed a gram-scale reaction of 2-aminobenzyl alcohol 1a with KOH-DMSO at 90oC; the oxidation
of benzyl alcohol was not observed, however highly unstable azadiene 13 was obtained in 5% yield
along with the inseparable complex mixture (Scheme 5, iii). The reaction of unstable azadiene 13 with
alkyne 2a under standard reaction condition provided the quinoline 3a in 12% yield. The above control
experiments clearly suggests the formation of quinoline via azadiene intermediate 13 (Scheme 5, iv).
Use of molecular sieves, declines the yield of the product 3a probably due to the low concentration of
H+ counter ions (Scheme 5, v).
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Scheme 5. Preliminary Mechanistic Studies
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Quinoline synthesis using azadiene 13
Ph
Ph
Ph
KOH (1.0 equiv)
iv
NH
N
(CH3)2SO
12 h, 90 oC
13
2a
3a, 12%
Role of water in the mechanism
KOH (1.0 equiv)
Ph
OH
NH2
4Ao MS
v
N
(CH3)2SO
16 h, 90 oC
1a
3a, 40%
2a
Role of NH2 group in the mechanism
Ph
KOH (1.0 equiv)
Ph
OH
vi
O
(CH3)2SO
16 h, 90 oC
14; 55%
Hydroxylation product
7
2a
Ph
2a
Ph
KOH (1.0 equiv)
OH
vii
7
14
(CH3)2SO
16 h, 90 oC
N
NH2
10%
3a, 65%
1a
Deuterium labelling study
KOH / (CH3)2SO
Ph
no D incorporation
viii
D2O workup
N
2a
3a: 80%
Ph
OH
NH2
60% incorporation of D
D
1a
Ph
KOH / (CD3)2SO
ix
x
N
D 90% incorporation of D
H2O workup /
without H2O workup
3a': 80%
H
N
(37%)
D
Ph
Ph
KOH (1.0 equiv)
H
(CD3)2SO
12 h, 90 oc
N
D
(18%)
3a
3a''
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When we perform the reaction of benzyl alcohol 7 with 2a in the presence of KOH-DMSO, the
hydroxyalkoxylation product 14 was obtained in 55% yield which suggests the crucial role of the -NH2
group in the reaction (Scheme 5, vi).23g A competition experiment between 1a and 7 with alkyne 2a was
performed; the product 3a was found in 65% yield; however hydroxylated product 14 was observed
only in 10% yield. This experiment indicate that the presence of o-NH2 group direct the formation of
intermediate 13 (Scheme 5, vii vs vi).
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Deuterium-labeling experiments were conducted to investigate the detailed mechanism of the reaction
(Scheme 5, viii-x). When alcohol 1a and alkyne 2a were subjected to the standerized reaction condition
followed by work up using D2O, no exchange of proton was observed in product 3a (Scheme 5, viii).
Surprising results were obtained when we performed the reaction using DMSO-d6 as a solvent; product
3a' was obtained in 80% yield with 60% and 90% incorporation of deuterium at C-2 and C-4 position
(Scheme 5, ix). Interestingly, when final product quinoline 3a was subjected to KOH/DMSO-d6 at 90oC,
product 3a'' was obtained with 18% and 37% incorporation of deuterium at C-2 and C-4 position
respectively (Scheme 5, x). The above isotopic labeling experiments infer that the reaction proceeds via
H-D exchange within the reaction (Scheme 5, ix vs x).
Based on the evidence obtained from the control experiments and isotopic studies, a plausible
mechanism is proposed in Scheme 6.27 We have designed two possible pathways for the generation of
azadiene intermediate 13. The mechanism is initiated by the protonation of the 2-aminobenzyl alcohol 1
via KOH-DMSO suspension which leads to the formation of imine type motif Q. The anion of the
DMSO abstracts the proton and forms azadiene 1323f,g (Route A, Scheme 6). Another route to achieve
the key intermediate 13 is via an attack of -OH nucleophile onto soft electrophilic sulphur of dimethyl
sulfoxide to form an intermediate X. The Intermediate X leads to the formation of azadiene 13 through
the formation of intermediate Y (Route B). The consequent [4+2] cycloaddition (R) of azadiene 13 with
alkyne 2/2’28 would form dihydro quinoline S. The H-D exchange of species S would generate species
T, which upon auto-oxidation leads to the formation of quinoline (Scheme 6i).
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An unusual result obtained in Scheme 2 enforced us to investigate the mechanism of the reaction
of 1,3- and 1,4-diethynylbenzene 2q–r with substrate 1a has been described in Scheme 6, ii. The
mechanism proceeded via nucleophilic addition of in situ formed water on to quinoline A and generates
the ion B which forms aldehyde intermediate D through enol C. The auto-oxidation of intermediate D
triggered the formation of carboxylate intermediate E which subsequently leads to the formation of
product 3b and 3c via decarboxylation (Scheme 6ii).
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Scheme 6. Final Mechanistic Pathway
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CONCLUSION
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In summary, a novel base promoted synthesis of C-3 functionalized quinolines from azadiene (generated
in situ from o-aminobenzyl alcohol) and terminal alkynes have been developed via [4+2] HDA reaction
with an excellent chemo- and regioselectivity. Reaction of 2-aminobenzyl alcohol with 1,3- and 1,4-
diethynylbenzene provided the unusual C-3 tolyl-quinolines via [4+2] HDA and successive oxidative
decarboxylation. The developed chemistry was also flourishing with secondary 2-aminobenzylalcohol
with terminal alkynes. The results of the control experiments support the -NH2 group directed
mechanistic pathway via azadiene formation and not through aldehyde formation. We overcame the
challenges of selectivity (chemo-, and regio) and constructed biologically important quinolines in a site-
selective fashion.
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EXPERIMENTAL SECTION
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General Method. H NMR (400 MHz) and 13C NMR (100 MHz) spectra were recorded in
CDCl3/DMSO-d6. Chemical shifts for protons and carbons are reported in ppm from tetramethylsilane
and are referenced to the carbon resonance of the solvent. Data are reported as follows: chemical shift,
multiplicity (s = singlet, br s = broad singlet, d = doublet, t = triplet, q = quartet, m = multiplet, dd =
doublet of doublet), coupling constants in Hertz and integration. High-resolution mass spectra were
recorded on electrospray mass spectrometer. Crystal structure analysis was accomplished on single
needles X-ray diffractometer. TLC analysis was performed on commercially prepared 60 F254 silica gel
plates and visualized by either UV irradiation or by staining with I2. All purchased chemicals were used
as received. All melting points are uncorrected.
2-amino-5-bromobenzyl alcohol (1c) by literature reported method.29
Synthesis of (6-aminobenzo[d][1,3]dioxol-5-yl)methanol :
Step 1. To a cooled (ice-bath) solution of 6-nitrobenzo[d][1,3]dioxole-5-carbaldehyde (1.0 g, 10 mmol)
in EtOH (15 mL) was added NaBH4 ( 1.5 eq.), and the mixture stirred for 2 h at 0 °C. Careful
evaporation of the solvent gave an orange semi-solid, which was slowly treated with saturated aq.
NH4Cl (10 mL) solution. After evolution of H2 gas ended, the aqueous phase was extracted with
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CH2Cl2. The combined organic phases were washed with H2O and brine, dried over Na2SO4 and
filtered. Evaporation of the solvent gave (6-nitrobenzo[d][1,3]dioxol-5-yl)methanol (0.9 g, 90%) which
was used in the next step without further purification.
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Step 2. (6-nitrobenzo[d][1,3]dioxol-5-yl)methanol (0.9 g) was dissolved in EtOH (35 mL) and H2O (5
mL). NH4Cl (1.0 equiv) and Fe-powder (6.0 equiv) were added and the mixture was heated to reflux for
6 h. After cooling at room temperature, the solution was decanted from the solids, diluted with CH2Cl2,
and washed with saturated aq. NaHCO3 (35 mL) solution. The aqueous phase was extracted extensively
with CH2Cl2, and the combined organic phases were washed with brine solution, dried over Na2SO4,
filtered and evaporated to give (6-aminobenzo[d][1,3]dioxol-5-yl)methanol as an off-white solid.30
1
(6-Aminobenzo[d][1,3]dioxol-5-yl)methanol (1d). The product was obtained as a off-white solid. H
NMR (400 MHz, DMSO) δ 6.64 (s, 1H), 6.29 (s, 1H), 5.79 (s, 2H), 4.91 ( t, J = 5.3 Hz, 1H), 4.64 (s,
2H), 4.27 (d, J = 5.3 Hz, 2H); 13C NMR (100 MHz, DMSO) δ: 146.4, 141.3, 137.9, 117.6, 108.2, 99.8,
96.9, 60.7. HRMS (ESI-TOF) [M]+ Calcd for [C8H9NO3] 167.0582, found 167.0582.
1-(2-aminophenyl)ethanol (12).31 A mixture of 2-aminoacetophenone (0.159 g, 1.1 mmol) and NaBH4
(0.061g, 1.5 mmol) in EtOH (12 mL) was refluxed under argon for 2 h affording after work-up 1-(2-
aminophenyl)ethanol as a white solid. The structure and purity of 1-(2-aminophenyl) ethanol were
confirmed by comparison of their physical and spectral data (1H NMR and 13C NMR) with those
reported in literature7
General Procedure for the Synthesis of Functionalized Quinolines 3a-p.
In an oven-dried round bottom flask, a solution of aminophenylmethanol 1 (0.5 mmol), internal alkyne 2
(0.4 mmol) and 1.0 equiv of crushed KOH in 2.0 mL of DMSO were added under inert atmosphere. The
resulting reaction mixture was heated at 90 °C for 24−30 h. Progression of the reaction was monitored
by TLC analysis; after complete consumption of starting material, the reaction was cooled to room
temperature. The reaction mixture was diluted with ethyl acetate (10 mL) and water (15 mL). The layers
were separated, and the organic layer was washed with aqueous saturated brine solution and dried over
Na2SO4. Organic layer was concentrated under reduced pressure. The crude material so obtained was
purified by column chromatography on silica gel (100−200) (hexane:ethyl acetate; 90/10). The structure
and purity of known starting materials were confirmed by comparison of their physical and spectral data
(1 H NMR, 13C NMR, and HRMS).
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3-phenylquinoline (3a). The product was obtained as a pale yellow oil, (82.0 mg, 80%), 1H NMR (400
MHz, CDCl3) δ 9.20 (d, J = 3.0 Hz, 1H), 8.55 (d, J = 2.3 Hz, 1H), 8.03–7.97 (m, 2H), 7.80 (d, J = 8.4
Hz, 2H), 7.72–7.68 (m, 1H), 7.57 (t, J = 6.9 Hz, 1H), 7.50–7.43 (m, 2H), 7.40–7.37 (m, 1H); 13C NMR
(100 MHz, CDCl3) δ: 149.4, 146.8, 137.0, 132.8, 129.5, 129.2, 128.6, 128.4, 128.2, 127.7, 127.2, 127.0.
HRMS (ESI-TOF) [M+H]+ Calcd for [C15H11N] 206.0970, found 206.0963.
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3-(p-Tolyl)quinoline (3b). The product was obtained as a pale brown needles, mp:91–94 C. (89.7 mg,
82%), 1H NMR (400 MHz, CDCl3) δ 9.16 (d, J = 2.3 Hz, 1H), 8.26 (d, J = 2.3 Hz, 1H), 8.13 (d, J = 8.4
Hz, 1H), 7.85 (d, J = 6.9 Hz, 1H), 7.71–7.67 (m, 1H), 7.60 (d, J = 7.6 Hz, 2H), 7.57–7.53 (m, 1H), 7.32
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(d, J = 7.6 Hz, 2H), 2.43 (s, 3H); C NMR (100 MHz, CDCl3) δ: 149.9, 147.1, 138.0, 134.9, 133.7,
132.8, 129.8, 129.2, 129.1, 128.0, 127.9, 127.2, 126.9, 21.2. HRMS (ESI-TOF) [M+H]+ Calcd for
[C16H13N] 220.1126, found 220.1153.
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3-(m-Tolyl)quinoline (3c). The product was obtained as a brown oil (88.6 mg, 81%), H NMR (400
MHz, CDCl3) δ 9.17 (d, J = 2.3 Hz, 1H), 8.28 (d, J = 2.3 Hz, 1H), 8.13 (d, J = 8.4 Hz, 1H), 7.87 (d, J =
8.4 Hz, 1H), 7.73–7.69 (m, 1H), 7.57 (t, J = 6.9 Hz, 1H), 7.51 (d, J = 6.9 Hz, 2H), 7.41 (t, J = 7.6 Hz,
1H), 7.26–7.24 (m, 1H), 2.46 (s, 3H); 13C NMR (100 MHz, CDCl3) δ: 149.9, 147.2, 138.8, 137.8, 133.9,
133.1, 129.3, 129.1, 129.0, 128.8, 128.1, 128.0, 127.9, 126.9, 124.5, 21.5. HRMS (ESI-TOF) [M+H]+
Calcd for [C16H13N] 220.1126, found 220.1148.
3-(o-Tolyl)quinoline (3d). The product was obtained as brown oil (91.9 mg, 84%), 1H NMR (400 MHz,
CDCl3) δ 8.85 (d, J = 2.3 Hz, 1H), 8.08 (d, J = 8.4 Hz, 1H), 8.01 (d, J = 1.52 Hz, 1H), 7.77 (d, J = 8.4
Hz, 1H), 7.68–7.64 (m, 1H), 7.52–7.48 (m, 1H), 7.26–7.24 (m, 4H), 2.25 (s, 3H); 13C NMR (100 MHz,
CDCl3) δ: 151.4, 146.9, 138.0, 135.8, 135.3, 134.7, 130.6, 130.1, 129.3, 129.2, 128.1, 127.8, 127.7,
126.9, 126.1, 20.4. HRMS (ESI-TOF) [M+H]+ Calcd for [C16H13N] 220.1126, found 220.1149.
3-(4-Ethylphenyl)quinoline (3e). The product was obtained as a brown needles, mp 83–86 oC. (95.5 mg,
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82%), H NMR (400 MHz, CDCl3) δ 9.07 (d, J = 2.3 Hz, 1H), 8.15 (s, 1H), 8.03 (d, J = 8.4 Hz, 1H),
7.73 (d, J = 8.4 Hz, 1H), 7.60–7.56 (m, 1H), 7.52 (d, J = 6.9 Hz, 2H), 7.44 (t, J = 6.9 Hz, 1H), 7.24 (d, J
= 7.6 Hz, 2H), 2.61 (q, J = 7.6 Hz, 2H), 1.19 (t, J = 6.9 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ: 160.8,
146.5, 144.3, 135.9, 133.2, 129.2, 128.8, 128.6, 128.3, 127.8, 127.5, 126.9, 126.3, 28.4, 15.6. HRMS
(ESI-TOF) [M+H]+ Calcd for [C17H15N] 234.1282, found 234.1299.
3-(4-Butylphenyl)quinoline (3f). The product was obtained as brown oil (108.3 mg, 83%), 1H NMR (400
MHz, CDCl3) δ 9.25 (d, J = 2.3 Hz, 1H), 8.32 (d, J = 2.3 Hz, 1H), 8.21 (d, J = 8.4 Hz, 1H), 7.90 (d, J =
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8.4 Hz, 1H), 7.78–7.74 (m, 1H), 7.68 (d, J = 8.4 Hz, 2H), 7.61 (t, J = 8.4 Hz, 1H), 7.39 (d, J = 7.6 Hz,
2H), 2.77–2.69 (m, 2H), 1.76–1.69 (m, 2H), 1.52–1.43 (m, 2H), 1.05–1.02 (m, 3H); 13C NMR (100
MHz, CDCl3) δ: 149.8, 147.1, 142.9, 135.0, 133.6, 132.7, 129.14, 129.07, 129.0, 127.9, 127.8, 127.1,
126.8, 35.2, 33.5, 22.3, 13.9. HRMS (ESI-TOF) [M+H]+ Calcd for [C19H19N] 262.1595, found
262.1599.
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3-(4-(tert-Butyl)phenyl)quinoline (3g). The product was obtained as a orange semi–solid (104.4 mg,
80%), 1H NMR (400 MHz, CDCl3) δ 9.19 (d, J = 3.0 Hz, 1H), 8.28 (d, J = 1.5 Hz, 1H), 8.14 (d, J = 8.4
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Hz, 1H), 7.86 (d, J = 8.4 Hz, 1H), 7.73–7.66 (m, 3H), 7.58–7.54 (m, 3H), 1.40 (s, 9H); C NMR (100
MHz, CDCl3) δ:151.2, 149.9, 147.1, 134.9, 133.6, 132.8, 129.2, 129.1, 128.0, 127.9, 127.0, 126.9,
126.1, 34.6, 31.3. HRMS (ESI-TOF) [M+H]+ Calcd for [C19H19N] 262.1595, found 262.1612.
3-(4-Methoxyphenyl)quinoline (3h).The product was obtained as a pale yellow needles, mp: 99–102 oC.
( 102.2 mg, 87%), 1H NMR (400 MHz, CDCl3) δ 9.16 (d, J = 1.16 Hz, 1H), 7.97 (s, 1H), 7.85 (d, J =
8.4 Hz, 1H), 7.76 (d, J = 7.6 Hz, 1H), 7.67–7.64 (m, 3H), 7.56 (t, J = 7.6 Hz, 1H), 6.76 (d, J = 8.4 Hz,
2H), 3.75 (s, 3H); 13C NMR (100 MHz, CDCl3) δ: 160.3, 157.8, 149.8, 136.0, 132.4, 129.2, 129.1,
129.0, 128.8, 127.8, 126.9, 126.2, 114.6, 55.4. HRMS (ESI-TOF) [M+H]+ Calcd for [C16H13NO]
236.1075, found 236.1095.
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3-(4-Phenoxyphenyl)quinoline (3i). The product was obtained as a yellow needles, mp: 86–88 C,
(126.2 mg, 85%), 1H NMR (400 MHz, CDCl3) δ 9.14 (d, J = 2.3 Hz, 1H), 8.22 (d, J = 2.3 Hz, 1H), 8.12
(d, J = 8.4 Hz, 1H), 7.82 (d, J = 6.9 Hz, 1H), 7.70–7.66 (m, 1H), 7.65–7.61 (m, 2H), 7.53 (t, J = 8.4 Hz,
1H), 7.38–7.35 (m, 2H), 7.15–7.11 (m, 3H), 7.08–7.06 (m, 2H); 13C NMR (100 MHz, CDCl3) δ: 157.5,
156.6, 149.6, 147.0, 133.0, 132.7, 132.5, 129.8, 129.2, 129.0, 128.6, 127.9, 127.8, 126.9, 123.6, 119.1.
HRMS (ESI-TOF) [M+H]+ Calcd for [C21H15NO] 298.1232, found 298.1251.
3-(Thiophen-3-yl)quinoline (3j). The product was obtained as a brown needles, mp: 80–83 oC. (88.6 mg,
84%), 1H NMR (400 MHz, CDCl3) δ 9.19 (d, J = 2.3 Hz, 1H), 8.27–8.26 (m, 1H), 8.10 (d, J = 8.4 Hz,
1H), 7.83 (d, J = 8.4 Hz, 1H), 7.71–7.64 (m, 2H), 7.57–7.51 (m, 2H), 7.49–7.47 (m, 1H); 13C NMR (100
MHz, CDCl3) δ: 149.4, 147.1, 138.8, 132.0, 129.2, 128.7, 128.0, 127.8, 127.0, 126.0, 121.6. HRMS
(ESI-TOF) [M+H]+ Calcd for [C13H9NS] 212.0534, found 212.0553.
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3-(Pyridin-2-yl)quinoline (3k). The product was obtained as dark brown oil (76.2 mg, 74%), H NMR
(400 MHz, CDCl3) δ 9.51 (d, J = 3.0 Hz, 1H), 8.76 (d, J = 2.2 Hz, 2H), 8.15 (d, J = 8.4 Hz, 1H), 7.92 (d,
J = 8.4 Hz, 1H), 7.88–7.80 (m, 2H), 7.74 (t, J = 6.8 Hz, 1H), 7.60–7.53 (m, 1H), 7.31 (t, J = 5.4 Hz,
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1H); 13C NMR (100 MHz, CDCl3) δ: 154.7, 150.1, 149.1, 137.1, 133.9, 130.0, 129.2, 129.0, 128.5,
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127.0, 122.8, 120.8. HRMS (ESI-TOF) [M+H]+ Calcd for [C14H10N2] 207.0922, found 207.0919.
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3-(Phenanthren-9-yl)quinoline (3l). The product was obtained as a brown oil (115.9 mg, 76%), 1H NMR
(400 MHz, CDCl3) δ 9.15 (br s, 1H), 8.79 (d, J = 8.4 Hz, 1H), 8.73 (d, J = 8.4 Hz, 1H), 8.29–8.27 (m,
2H), 7.91–7.86 (m, 3H), 7.81–7.76 (m, 2H), 7.69 (t, J = 6.9 Hz, 2H), 7.65–7.59 (m, 2H), 7.57–7.53 (m,
1H); 13C NMR (100 MHz, CDCl3) δ: 151.8, 147.2, 136.2, 134.8, 133.7, 131.2, 130.7, 130.6, 130.1,
129.5, 129.2, 128.7, 127.8, 127.77, 127.0, 126.98, 126.8, 126.7, 126.2, 123.0, 122.5. HRMS (ESI-TOF)
[M+H]+ Calcd for [C23H15N] 306.1282, found 306.1305.
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3-(4-(Trifluoromethoxy)phenyl)quinoline (3m). The product was obtained as a brown semi–solid (105.4
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mg, 73%), H NMR (400 MHz, CDCl3) δ 9.04 (d, J = 1.5 Hz, 1H), 8.18 (s, 1H), 8.06 (d, J = 8.4 Hz,
1H), 7.78 (d, J = 8.4 Hz, 1H), 7.66–7.61 (m, 3H), 7.50 (t, J = 6.8Hz, 1H), 7.28 (d, J = 8.3Hz, 2H); 13C
NMR (100 MHz, CDCl3) δ: 149.5, 149.2, 147.4, 136.6, 133.4, 132.4, 129.7, 129.2, 128.8, 128.0, 127.8,
127.2, 121.6. HRMS (ESI-TOF) [M+H]+ Calcd for [C16H10F3NO] 290.0792, found 290.0796.
3-(3-Methoxyphenyl)quinoline (3n). The product was obtained as a yellow oil (83.4 mg, 71%), 1H NMR
(400 MHz, CDCl3) δ 9.18 (d, J = 7.3 Hz, 1H), 8.28 (d, J = 1.5 Hz, 1H), 8.15 (d, J = 8.4 Hz, 1H), 7.87
(d, J = 7.6 Hz, 1H), 7.74–7.70 (m, 1H), 7.57 (t, J = 8.4 Hz, 1H), 7.44 (t, J = 7.6 Hz, 1H), 7.30–7.24 (m,
2H), 6.98 (dd, J = 8.4 and 2.3 Hz, 1H), 3.89 (s, 3H); 13C NMR (100 MHz, CDCl3) δ: 160.1, 149.8,
147.3, 139.2, 133.6, 133.2, 130.1, 129.3, 129.1, 127.9, 127.86, 126.9, 119.7, 113.3, 113.1, 55.3. HRMS
(ESI-TOF) [M+H]+ Calcd for [C16H13NO] 236.1075, found 236.1096.
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3-(3,5-Dimethoxyphenyl)quinoline (3o). The product was obtained as a orange oil (90.1 mg, 68%), H
NMR (400 MHz, CDCl3) δ 9.16 (d, J = 2.2 Hz, 1H), 8.28 (s, 1H), 8.14 (d, J = 8.4 Hz, 1H), 7.87 (d, J =
7.6 Hz, 1H), 7.72 (t, J = 7.6 Hz, 1H), 7.58 (t, J = 7.2 Hz, 1H), 6.84–6.83 (m, 2H), 6.55–6.54 (m, 1H),
3.88 (s, 6H); 13C NMR (100 MHz, CDCl3) δ: 161.3, 149.8, 140.6, 133.3, 129.4, 129.1, 129.0, 128.0,
127.0, 126.8, 118.0, 114.4, 105.7, 99.8, 55.1. HRMS (ESI-TOF) [M+H]+ Calcd for [C17H15NO2]
266.1181, found 266.1180.
3-(4-(Trifluoromethyl)phenyl)quinoline (3p). The product was obtained as a yellow needles, mp: 131–
133 oC. (95.5 mg, 70%), 1H NMR (400 MHz, CDCl3) δ 9.06 (d, J = 2.3 Hz, 1H), 8.22 (d, J = 2.3 Hz,
1H), 8.06 (d, J = 8.4 Hz, 1H), 7.80 (d, J = 7.6 Hz, 1H), 7.71–7.64 (m, 3H), 7.50 (t, J = 8.4 Hz, 1H), 7.39
(d, J = 8.4 Hz, 1H), 7.33–7.29 (m, 1H); 13C NMR (100 MHz, CDCl3) δ: 149.3, 140.5, 133.8, 130.0,
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for [C16H10F3N] 274.0843, found 274.0842.
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6-Chloro-3-phenylquinoline (4a). The product was obtained as a yellow needles, mp: 93–95 C. (83.6
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= 9.2 Hz, 1H), 7.86 (d, J = 1.5 Hz, 1H), 7.71–7.69 (m, 2H), 7.66–7.61 (m,1H), 7.55–7.52 (m 2H), 7.47–
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7.44 (m, 1H); C NMR (100 MHz, CDCl3) δ: 150.2, 145.6, 137.4, 134.7, 132.7, 132.2, 130.8, 130.3,
129.2, 128.6, 128.4, 127.4, 126.6 HRMS (ESI-TOF) [M+H]+ Calcd for [C15H10ClN] 240.0580, found
240.0577.
6-Chloro-3-(4-ethylphenyl)quinoline (4b). The product was obtained as a yellow oil. (97.4 mg, 73%),
1H NMR (400 MHz, CDCl3) δ 9.16 (d, J = 1.9 Hz, 1H), 8.18 (d, J = 1.5 Hz, 1H), 8.06 (d, J = 9.2 Hz,
1H), 7.85 (d, J = 2.3 Hz, 1H), 7.64–7.61 (m, 3H), 7.36 (d, J = 8.4 Hz, 2H), 2.74 (q, J = 7.6 Hz, 2H),
1.30 (t, J = 7.6 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ: 150.2, 145.5, 144.8, 134.6, 132.6, 131.8, 130.8,
130.1, 128.8, 128.7, 127.3, 126.5, 28.6, 15.5. HRMS (ESI-TOF) [M+H]+ Calcd for [C17H14ClN]
268.0893, found 268.0890.
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6-Chloro-3-(pyridin-2-yl)quinoline (4c). The product was obtained as brown oil (81.6 mg, 68%), H
NMR (400 MHz, CDCl3) δ 9.52 (d, J = 1.5 Hz, 1H), 8.77 (d, J = 1.9 Hz, 2H), 8.15 (d, J = 8.4 Hz, 1H),
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7.94–7.81 (m, 3H), 7.74 (t, J = 7.6 Hz, 1H), 7.58 (t, J = 7.6 Hz, 1H); C NMR (100 MHz, CDCl3) δ:
154.7, 150.1, 149.1, 148.0, 137.1, 134.0, 131.8, 130.0, 129.0, 128.5, 127.8, 127.0, 122.8, 120.8. HRMS
(ESI-TOF) [M+H]+ Calcd for [C14H9ClN2] 241.0533, found 241.0523.
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6-Bromo-3-phenylquinoline (4d). The product was obtained as yellow oil (102.2 mg, 72%), H NMR
(400 MHz, CDCl3) δ 9.18 (d, J = 1.5 Hz, 1H), 8.30 (d, J = 1.9 Hz, 1H), 8.14 (d, J = 8.4 Hz, 1H), 7.88 (d,
J = 7.6 Hz, 1H), 7.74–7.68 (m, 3H), 7.60–7.56 (m, 1H), 7.55–7.51 (m, 2H); 13C NMR (100 MHz,
CDCl3) δ: 147.2, 141.8, 137.8, 133.3, 130.5, 129.4, 129.1, 128.5, 128.1, 128.0, 127.4, 127.0, 126.3.
HRMS (ESI-TOF) [M+H]+ Calcd for [C15H10BrN] 284.0075, found 284.0068.
6-Bromo-3-(m-tolyl)quinoline (4e). The product was obtained as yellow oil (110.2 mg, 74%), 1H NMR
(400 MHz, CDCl3) δ 9.17 (d, J = 1.5 Hz, 1H), 8.30 (d, J = 1.5 Hz, 1H), 8.14 (d, J = 8.4 Hz, 1H), 7.88 (d,
J = 7.6 Hz, 1H), 7.72 (t, J = 6.8 Hz, 1H), 7.52–7.51 (m, 3H), 7.42 (t, J = 7.6 Hz, 1H), 2.47 (s, 3H); 13C
NMR (100 MHz, CDCl3) δ: 150.0, 138.9, 137.8, 133.2, 129.3, 129.13, 129.07, 128.8, 128.1, 128.0,
127.0, 124.5, 21.6. HRMS (ESI-TOF) [M+H]+ Calcd for [C16H12BrN] 298.0231, found 298.0223.
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6-Bromo-3-(4-(tert-butyl)phenyl)quinoline (4f). The product was obtained as yellow oil (122.4 mg,
72%), 1H NMR (400 MHz, CDCl3) δ 9.19 (d, J = 2.3 Hz, 1H), 8.30 (d, J = 1.5 Hz, 1H), 8.13 (d, J = 8.4
Hz, 1H), 7.88 (d, J = 8.4 Hz, 1H), 7.74–7.66 (m, 3H), 7.60–7.55 (m, 3H), 1.39 (s, 9H); 13C NMR (100
MHz, CDCl3) δ: 151.4, 150.1, 135.0, 133.7, 133.1, 129.4, 129.3, 128.1, 127.2, 127.0, 126.3, 53.6, 31.4.
HRMS (ESI-TOF) [M+H]+ Calcd for [C19H18BrN] 340.0701, found 340.0699.
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7-(Thiophen-3-yl)-[1,3]dioxolo[4,5-g]quinoline (4g). The product was obtained as dark brown oil (102
mg, 80%), 1H NMR (400 MHz, CDCl3) δ 8.89 (d, J = 2.3 Hz, 1H), 8.03 (d, J = 1.5 Hz, 1H), 7.50 (t, J =
2.3 Hz, 1H), 7.39 (s, 2H), 7.33 (s, 1H), 7.00 (s, 1H), 6.03 (s, 2H); 13C NMR (100 MHz, CDCl3) δ: 150.7,
148.3, 146.6, 145.1, 138.9, 131.5, 127.4, 126.9, 126.0, 125.2, 121.0, 105.4, 102.7, 101.8. HRMS (ESI-
TOF) [M+H]+ Calcd for [C14H9NO2S] 256.0432, found 256.0429.
7-(Pyridin-2-yl)-[1,3]dioxolo[4,5-g]quinoline (4h). The product was obtained as brown needles, mp:
90–92 oC. (97.5 mg, 78%), 1H NMR (400 MHz, CDCl3) δ 8.59 (d, J = 3.8 Hz, 1H), 7.50 (t, J = 7.6 Hz,
1H), 7.22 (d, J = 7.6 Hz, 1H), 7.09–7.07 (m, 1H), 6.52 (s, 2H), 6.06 (s, 2H), 5.81 (s, 2H); 13C NMR (100
MHz, CDCl3) δ: 163.4, 149.4, 146.4, 140.2, 136.1, 135.3, 121.4, 121.1, 112.2, 108.7, 100.3, 96.9.
HRMS (ESI-TOF) [M+H]+ Calcd for [C15H10N2O2] 251.0820, found 251.0814.
7-Phenyl-[1,3]dioxolo[4,5-g]quinoline (4i). The product was obtained as dark brown needles, mp 67–70
oC, (93.3 mg, 75%), 1H NMR (400 MHz, CDCl3) δ 8.95 (d, J = 2.3 Hz, 1H), 8.12 (d, J = 2.2 Hz, 1H),
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7.67 (d, J = 7.6 Hz, 2H), 7.50 (t, J = 6.8 Hz, 2H), 7.43–7.39 (m, 2H), 7.10 (s, 1H), 6.12 (s, 2H); C
NMR (100 MHz, CDCl3) δ: 150.7, 148.2, 147.2, 145.4, 137.9, 132.5, 132.4, 129.1, 127.8, 127.2, 125.1,
105.4, 102.9, 101.8. HRMS (ESI-TOF) [M+H]+ Calcd for [C16H11NO2] 250.0868, found 250.0872.
7-(4-Ethylphenyl)-[1,3]dioxolo[4,5-g]quinoline (4j). The product was obtained as yellow solid (106.6
mg, 77%), 1H NMR (400 MHz, CDCl3) δ 8.88 (d, J = 2.3 Hz, 1H), 8.02 (d, J = 1.5 Hz, 1H), 7.53 (d, J =
7.6 Hz, 2H), 7.33 (s, 1H), 7.26 (d, J = 7.6 Hz, 2H), 7.03 (s, 1H), 6.04 (s, 2H), 2.66 (q, J = 7.6 Hz, 2H),
1.22 (t, J = 7.6 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ: 150.5, 147.4, 145.4, 144.1, 135.3, 132.4, 132.1,
128.6, 127.9, 127.1, 125.2, 105.6, 104.6, 102.8, 28.6, 15.6. HRMS (ESI-TOF) [M+H]+ Calcd for
[C18H15NO2] 278.1181, found 278.1154.
7-(4-Butylphenyl)-[1,3]dioxolo[4,5-g]quinoline (4k). The product was obtained as brown semi-
1
solid(118.9 mg, 78%), H NMR (400 MHz, CDCl3) δ 8.87 (s, 1H), 8.02 (s, 1H), 7.50 (d, J = 8.4 Hz,
2H), 7.33 (s, 1H), 7.23 (d, J = 7.6 Hz, 2H), 7.01 (s, 1H), 6.03 (d, J = 1.1 Hz, 2H), 2.62–2.58 (m, 2H),
1.61–1.53 (m, 2H), 1.36–1.29 (m, 2H), 0.91–0.86 (m, 3H); 13C NMR (100 MHz, CDCl3) δ: 150.6,
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148.2, 147.2, 145.2, 142.8, 135.2, 132.4, 132.2, 129.2, 127.0, 125.2, 105.4, 102.8, 101.8, 35.3, 33.6,
29.7, 22.4, 14.0. HRMS (ESI-TOF) [M+H]+ Calcd for [C20H19NO2] 306.1494, found 306.1495.
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4-Methyl-3-(p-tolyl)quinoline (6a). The product was obtained as yellow oil (58.2 mg, 50%), H NMR
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(400 MHz, CDCl3) δ 8.76 (s, 1H), 8.10 (d, J = 8.4 Hz, 1H), 8.03 (d, J = 7.6 Hz, 1H), 7.69–7.65 (m, 1H),
7.58–7.54 (m, 1H), 7.28–7.24 (m, 4H), 2.60 (s, 3H), 2.40 (s, 3H); 13C NMR (100 MHz, CDCl3) δ:
151.6, 146.8, 140.5, 137.3, 135.6, 134.3, 129.8, 129.77, 129.1, 128.7, 127.9, 126.6, 124.1, 21.2, 15.6.
HRMS (ESI-TOF) [M+H]+ Calcd for [C17H15N] 234.1283, found 234.1276.
4-Methyl-3-(4-(trifluoromethyl)phenyl)quinoline (6b). The product was obtained as yellow oil (64.5
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mg, 45%), H NMR (400 MHz, CDCl3) δ 8.75 (s, 1H), 8.14 (d, J = 8.4 Hz, 1H), 8.09 (d, J = 7.6 Hz,
1H), 7.76–7.72 (m, 3H), 7.65–7.61 (m, 1H), 7.51 (d, J = 8.4 Hz, 2H), 2.63 (s, 3H); 13C NMR (100 MHz,
CDCl3) δ: 150.7, 147.1, 142.3, 141.0, 133.1, 130.3, 130.0, 129.4, 127.1, 125.4 (q, J = 3.8 Hz, 1C),
124.2, 15.6. HRMS (ESI-TOF) [M+H]+ Calcd for [C17H12F3N] 288.1000, found 288.0970.
Mechanistic control experiments:
Benzaldehyde (8) The product was reported in ref 22f.
o
2-(4-Methylquinolin-2-yl)aniline (12). The product was obtained as a yellow needles, mp : 75–77 C.
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(105.3 mg, 90%), H NMR (400 MHz, CDCl3) δ 8.08 (d, J = 8.4 Hz, 1H), 7.96 (d, J = 8.3 Hz, 1H),
7.73–7.67 (m, 3H), 7.55–7.51 (m, 1H), 7.25–7.21 (m, 1H),6.87–6.81 (m, 2H), 6.22 (br s, 2H), 2.72 (s,
3H); 13C NMR (100 MHz, CDCl3) δ: 158.7, 147.3, 146.5, 144.5, 130.0, 129.6, 129.2, 129.1, 126.3,
125.7, 123.4, 121.5, 120.9, 117.2, 117.1, 18.9. HRMS (ESI-TOF) [M+H]+ Calcd for [C16H14N2]
235.1235, found 235.1245.
6-Methylenecyclohexa-2,4-dienimine (13). The product was obtained as yellow oil, 1H NMR (400 MHz,
CDCl3) δ 7.15–7.11 (m, 1H), 7.03 (d, J = 7.6 Hz, 1H), 6.72–6.66 (m, 2H), 4.50 (s, 2H), 3.76 (br s, 1H);
13C NMR (100 MHz, CDCl3) δ: 146.2, 130.4, 129.4, 121.7, 118.0, 115.8, 70.2 HRMS (ESI-TOF)
[M+H]+ Calcd for [C7H7N] 106.0657, found 106.0665.
(2-(benzyloxy)vinyl)benzene (14) The product was reported in Asian J. Org. Chem., 2016, 5, 213–221
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2,4-D-3-phenylquinoline (3a') The product was obtained as a pale yellow oil, H NMR (400 MHz,
CDCl3) δ 9.16 (s, 0.1H), 8.25 (s, 0.4H), 8.13 (d, J = 8.4 Hz, 1H), 7.83 (d, J = 7.6 Hz, 1H), 7.70–7.66 (m,
3H), 7.55 (d, J = 7.6 Hz, 1H), 7.51–7.47 (m, 2H), 7.41 (d, J = 7.6 Hz, 1H); 13C NMR (100 MHz, CDCl3)
δ: 149.7 (d, J = 10.5 Hz, 1C), 149.3 (d, J = 26.8 Hz, 1C), 147.1, 137.6 (d, J = 2.9 Hz, 1C), 133.5(d, J =
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9.6 Hz, 1C), 133.1 (d, J = 12.5, Hz, 1C), 129.3, 129.1, 129.0, 127.9, 127.8, 127.3, 126.9, 126.8 (d, J
6
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=7.6 Hz, 1C). HRMS (ESI-TOF) [M+H]+ Calcd for [C15H9D2N] 208.1095, found 208.1068.
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Deuterated 3-phenylquinoline (3a'') The product was obtained as a dark orange needle, mp 119–121 oC.
1H NMR (400 MHz, CDCl3) δ 9.24 (d, J = 1.5 Hz, 0.8 H), 8.62 (s, 0.63 H), 8.06–8.03 (m, 2H), 7.86 (d,
J = 7.6 Hz, 2H), 7.75 (t, J = 7.6 Hz, 1H), 7.63 (t, J = 6.8 Hz, 1H), 7.54 (t, J = 7.6 Hz, 2H), 7.46–7.42 (m,
1H);13C NMR (100 MHz, CDCl3) δ: 149.5, 146.8, 137.1, 132.9, 132.8, 129.5, 129.2, 128.7, 128.42,
128.38, 128.2, 127.7, 127.6, 127.2, 127.0. HRMS (ESI-TOF) [M+H]+ Calcd for [C15H9D2N] 208.1095,
found 208.1068.
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ASSOCIATED CONTENT
Supporting Information
The Supporting Information is available free of charge on the ACS Publications website at
http://pubs.acs.org.
1H NMR 13C NMR and HRMS spectra
X-ray crystallographic of compound 3e
AUTHOR INFORMATION
Corresponding Author
*E-mail: averma@acbr.du.ac.in
Notes
The authors declare no competing financial interest.
ACKNOWLEDGEMENTS
The work was supported by SERB (DST) and University of Delhi. R.K.S. and M.P.are thankful to UGC
and DST-SERB for fellowship.
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