Iron-catalyzed tandem reactions of aldehydes, terminal alkynes, and primary amines as a strategy for the synthesis of quinoline derivatives

Article abstract of DOI:10.1002/jhet.417

FeCl₃-catalyzed three-component tandem condensation/addition/ cyclization/oxidation reactions of aldehydes, terminal alkynes, and primary amines have been developed. The processes can provide a diverse range of quinoline derivatives in good yields from simple starting materials. A possible reaction mechanism was proposed.

Full text of DOI:10.1002/jhet.417

January 2011
Iron-Catalyzed Tandem Reactions of Aldehydes, Terminal
Alkynes, and Primary Amines as a Strategy for the Synthesis of
Quinoline Derivatives
153
Yicheng Zhang,a Pinhua Li,a and Lei Wanga,b
*
aDepartment of Chemistry, Huaibei Normal University, Huaibei, Anhui 235000,
People’s Republic of China
bState Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry,
Chinese Academy of Sciences, Shanghai 200032, People’s Republic of China
*E-mail: leiwang@chnu.edu.cn
Received October 8, 2009
DOI 10.1002/jhet.417
Published online 6 October 2010 in Wiley Online Library (wileyonlinelibrary.com).
FeCl3-catalyzed three-component tandem condensation/addition/cyclization/oxidation reactions of
aldehydes, terminal alkynes, and primary amines have been developed. The processes can provide a
diverse range of quinoline derivatives in good yields from simple starting materials. A possible reaction
mechanism was proposed.
J. Heterocyclic Chem., 48, 153 (2011).
INTRODUCTION
The quinoline nucleus is a prominent structural motif
found in numerous natural products and synthetic com-
pounds with important pharmacological and biological
activities [13–15], and thus the development of efficient
syntheses of highly functionalized quinoline derivatives
has been the focus of most researches for many decades
and continues to be an active and rewarding research
area [16]. However, most of the existing methods suffer
from the limited availability of substrates or require
multistep procedures. During the course of our efforts
directed toward the development of iron-catalyzed or-
ganic transformations, we found that treatment of alde-
hydes, primary amines, with terminal alkynes in the
presence of FeCl3 (10% mol) without any ligand and
additive gave 2,4-disubstituted quinoline derivatives in
good yields with high atom economy [17]. This reaction
would proceed presumably through a tandem condensa-
tion/addition/cyclization/oxidation reactions with only
water as the waste product (Scheme 1).
Iron salts as effective, alternative, and promising tran-
sition-metal catalysts have received much more attention
in recent years because of their less expensive, readily
available, and environmentally benign properties. During
the last half decade, iron-catalyzed oxidation [1], hydro-
genation [2], hydrosilylation [3], and carbon-carbon
bond forming reactions have been intensively investi-
gated [4–6]. Most recently, iron-catalyzed S-arylation of
thiols [7], N-arylation of nitrogen nucleophiles [8], and
O-arylation of phenols [9] with aryl halides, and A3-
coupling reaction of aldehyde, alkyne, and amine have
been developed [10]. Because of interest for both the
academic and the industrial community, it is desirable to
expand the application scope of iron catalysts in organic
transformations due to their unique and significant
advantages.
One current important area of modern synthetic chem-
istry is the development of efficient practical methods
that minimize the requisite time, cost, labour, resource
management, and waste generation (atom economy) for
the desired transformation [11]. Tandem reaction (sev-
eral transformations in one synthetic operation) approach
is recognized as a powerful method toward this goal,
and only a single reaction solvent, workup procedure,
and purification step may be required to provide a prod-
uct that would otherwise have to be made over the
course of several individual steps [12].
Scheme 1
C
V
2010 HeteroCorporation

154
Y. Zhang, P. Li, and L. Wang
Vol 48
Table 1
Effect of solvent and iron source on the tandem reaction.a
RESULTS AND DISCUSSION
Our initial investigation focused on the effect of sol-
vent on the three-component tandem reactions of alde-
hydes, terminal alkynes, and primary amines. Several
solvents were screened in a model reaction of phenyla-
cetylene, benzaldehyde, and aniline, and a significant
solvent effect was observed (Table 1). When the reac-
tions were conducted in 1,2-dichloroethane and 1,2-
dibromoethane under an air atmosphere, excellent yields
of products (93%, 92%) were obtained. Use of toluene,
nitromethane (CH3NO2), and dioxane as solvents led to
lower yields of isolated products, and only 12% yield of
the desired product was obtained while the reaction was
performed in ethylene glycol. What surprised us was the
reaction didn’t work when DMSO and DMF were used
as solvent (Table 1, entries g and h). It should be worth
noting that 68% yield of the desired tandem product
was isolated when the reaction was carried out under a
nitrogen atmosphere (Table 1, entry d).
The effect of iron source on the tandem reaction was
also explored. Among the tested iron sources, FeCl3 and
FeBr3 proved to be the best choice (93% and 92% yields,
respectively). FeCl2 were inferior and generated the
desired product in 82% yield, when Fe2O3 was used as
catalyst, only 38% yield was obtained. However,
Fe(NO3)3, Fe2(SO4)3 or Fe powder (100 nm) was found to
be inactive to the tandem reaction (Table 1, entries iꢀn).
Entry
Solvent
Fe source
Yield (%)b
a
b
c
d
Toluene
Dioxane
CH3NO2
FeCl3
FeCl3
FeCl3
FeCl3
71
53
73
1,2-Dichloroethane
93
68c
92
e
f
g
h
i
1,2-Dibromoethane
Ethylene glycol
DMSO
FeCl3
FeCl3
FeCl3
12
0
DMF
FeCl3
FeBr3
FeCl2
0
92
82
1,2-Dichloroethane
1,2-Dichloroethane
1,2-Dichloroethane
1,2-Dichloroethane
1,2-Dichloroethane
1,2-Dichloroethane
1,2-Dichloroethane
1,2-Dichloroethane
j
k
l
Fe(NO3)3
Fe2(SO4)3
Fe2O3
Fe powder
FeCl3
FeCl3
Trace
Trace
38
0
74
m
n
od
pe
93
a Phenylacetylene (112 mg, 1.10 mmol), benzaldehyde (106 mg, 1.00
mmol), aniline (91 mg, 1.00 mmol), Fe source (0.01 mmol), solvent
(2.0 mL) at 120ꢁC for 12 h under an air atmosphere.
b Isolated yields.
c Under a nitrogen atmosphere.
d In the present of FeCl3 (0.05 mmol).
e In the present of FeCl3 (0.20 mmol).
Table 2
Synthesis of quinoline derivatives by FeCl3-catalyzed tandem reaction.a
.
Entry
R1
R2
R3
Yieldb (%)
a
b
c
d
e
f
g
h
i
Ph
Ph
Ph
p-CH3Ph
p-CH3OPh
p-ClPh
p-BrPh
m-ClPh
o-ClPh
Ph
H
H
93
90
88
87
89
85
84
91
83
92
81
82
84
88
89
92
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
H
H
H
H
H
p-CH3
p-CH3O
p-Cl
o-CH3
Ph
Ph
j
k
l
Ph
Ph
Ph
Ph
2,3-[b]-Ph
m
n
o
p
p-CH3Ph
p-FPh
p-ClPh
p-PhPh
Ph
Ph
H
H
H
H
Ph
Ph
a Alkyne (1.10 mmol), aldehyde (1.00 mmol), amine (1.00 mmol), FeCl3 (16 mg, 0.01 mmol), 1,2-dichloroethane (DCE, 2.0 mL) at 120ꢁC for 12 h
under an air atmosphere.
b Isolated yields.
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January 2011
Iron-Catalyzed Tandem Reactions of Aldehydes, Terminal Alkynes, and Primary
Amines as a Strategy for the Synthesis of Quinoline Derivatives
155
Scheme 2. Possible mechanism of iron-catalyzed tandem reaction of
aldehyde, alkyne, and amine.
With respect to the catalyst loading, 10 mol% of FeCl3
was found to be optimal. When only 5 mol% of FeCl3
was used, the desired product was isolated in 74% yield,
and no significant improvement was observed with 20
mol% of Fe (Table 1, entries o and p). During the course
of our further optimization of the reaction conditions, the
reaction was generally completed within 24 h when it
was performed at 120ꢁC by using 10 mol% of FeCl3 in
the absence of any ligand and additive.
Under the optimized conditions, we extended our
studies to different combinations of aldehydes, primary
amines, and terminal alkynes, and the results are sum-
marized in Table 2. Phenylacetylene and aniline were
initially used as model substrates for exploring the alde-
hyde substrate scope. As can be seen from Table 2,
benzaldehyde and substituted benzaldehydes with both
electron-donating and electron-withdrawing functional-
ities, such as methoxy, methyl, bromo, and chloro
groups, afforded the corresponding quinoline derivatives
in good yields (Table 2, entries aꢀg). It seems that this
reaction was not sensitive to steric effects (such as, 2-
chlorobenzaldehyde giving the desired product in 84%
yield), nor was it to electronic effects (Table 2, entries c
vs d). However, when an aliphatic aldehyde (isobutyral-
dehyde) was subjected to the reaction, only 26% yield
of the desired product was obtained. Then, we examined
the scope of primary amine substrates, a combination of
phenylacetylene-benzaldehyde-amine was chosen and
various amines were surveyed. The results listed in Ta-
ble 2 indicated that p-toluidine, o-toluidine, p-anisidine,
and p-chloroaniline were good substrates for this tandem
transformation, and high yields of the corresponding
products were isolated under the optimized reaction con-
ditions (Table 2, entries h–k). It was worthy noting that
when 1-naphthylamine was used as substrate, the tan-
dem reaction also underwent smoothly to give the corre-
sponding quinoline derivative in 82% yield (Table 2,
entry l). Subsequently, the scope of alkynes in this reac-
tion was also investigated, and it was found that substi-
tuted phenylacetylenes, including p-methylphenylacety-
lene, p-chlorophenylacetylene, p-fluorophenylacetylene,
and diphenylacetylene, were suitable substrates for this
transformation, and the desired products were obtained
in good yields (Table 2, entries m–p). Unfortunately, al-
iphatic alkynes were aborted in this process. Meanwhile,
the reaction carried out in the presence of copper salt or
oxide, such as CuCl, CuBr, CuI, or Cu2O (0.10 equiv.)
in ClCH2CH2Cl was examined. However, no desired
product was observed.
formed alkynyl ate complex underwent nucleophilic
addition to imine formed in situ from aldehyde and pri-
mary amine to generate propargylamine. The triple bond
of propargylamine could be activated by FeCl3 as Lewis
acid to promote an intramolecular nucleophilic attack by
the N-substituted phenyl ring attached to the nitrogen.
The resulting FeIII vinyl ate complex subsequently under-
went decomposition to give the dihydroquinoline inter-
mediate and regenerate FeIII catalyst for further reactions.
In the presence of air oxygen, the generated dihydroqui-
noline could be further oxidized by O2 to afford quino-
line product. Comparing with the similar AuIII-catalyzed
tandem transformation, the stronger Lewis acidity of
FeCl3 than AuCl3 appears to be the main reason for the
higher efficiency of this catalytic system [18].
CONCLUSIONS
In summary, we have developed an efficient, practi-
cal, and economic method for the synthesis of quinoline
derivatives through a FeCl3-catalyzed three-component
tandem condensation/addition/cyclization/oxidation reac-
tions with only water as the waste product. These proc-
esses can provide a diverse range of quinoline deriva-
tives in good yields from simple starting materials. The
method has advantages of broad substrate scope, simple
operation, mild reaction conditions, and high effective-
ness. Further studies on the synthetic application of iron
as catalyst in organic synthesis are currently ongoing in
our group.
A possible mechanism of the FeCl3-catalyzed one-pot
tandem three-component reaction of aldehyde, alkyne,
and amine was proposed in Scheme 2. The catalyst
FeCl3 probably possesses one terminal alkynyl groups
because of the stability of FeIII alkynyl ate complex. The
EXPERIMENTAL
1
All H NMR spectra were recorded at 400 MHz by Bruker
FT-NMR spectrometers. Chemical shift are given as d value
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

156
Y. Zhang, P. Li, and L. Wang
Vol 48
1
with reference to tetramethylsilane (TMS) as internal standard.
The CHN analysis was performed on a Vario El III elementar.
Products were purified by flash chromatography on 230–400
mesh silica gel, SiO2. The chemicals were purchased from
commercial suppliers (Aldrich and Shanghai Chemical Com-
pany, China) and were used without purification prior to use.
General experimental procedure for the tandem
reaction. Under an air atmosphere, a 10 mL of sealable reac-
tion tube equipped with a magnetic stir bar was charged with
an aldehyde (1.00 mmol), amine (1.00 mmol), and the mixture
was heated and stirred in an oil bath at 60ꢁC for 1 h. Then
FeCl3 (16.2 mg, 0.10 mmol), alkyne (1.10 mmol) were added.
The reaction mixture was then stirred in an oil bath at 120ꢁC
until the substrates were consumed completely (about 12 h),
and then it was cooled to room temperature and the solvent
was evaporated, the residue was purified by flash chromatogra-
phy (hexane/AcOEt ¼ 15:1) to afford the desired product.
2-(2-Chlorophenyl)-4-phenylquinoline (4g). H NMR (400
MHz, CDCl3): d ¼ 8.31 (d, J ¼ 8.29 Hz, 1H), 7.87 (s, 1H),
7.83–7.77 (m, 2H), 7.53–7.45 (m, 8H), 7.33 (t, J ¼ 7.61 Hz,
1H); 13C NMR (100 MHz, CDCl3): d ¼ 156.73, 149.66,
144.81, 138.95, 138.01, 134.27, 129.72, 129.60, 129.48,
128.84, 128.59, 128.55, 127.64, 127.12, 125.86, 124.77. Anal.
Calcd. for C21H14ClN: C, 79.87; H, 4.47; N, 4.44. Found: C,
79.93; H, 4.55; N, 4.41.
1
6-Methyl-2,4-diphenylquinoline (4h) [22]. H NMR (400
MHz, CDCl3): d ¼ 8.18–8.13 (m, 3H), 7.77 (s, 1H), 7.65 (s,
1H), 7.58–7.49 (m, 8H), 7.46–7.43 (m, 1H), 2.47 (s, 3H); 13C
NMR (100 MHz, CDCl3): d ¼ 155.98, 148.43, 147.30, 139.68,
138.57, 136.26, 131.76, 129.77, 129.52, 129.14, 128.78,
128.55, 128.27, 127.45, 125.66, 124.35, 119.42, 21.81.
1
6-Methoxyl-2,4-diphenylquinoline (4i) [23]. H NMR (400
MHz, CDCl3): d ¼ 8.16–8.13 (m, 3H), 7.76 (s, 1H), 7.58–7.48
(m, 7H), 7.44–7.37 (m, 2H), 7.19 (d, J ¼ 2.9 Hz,1H), 3.78 (s,
3H); 13C NMR (100 MHz, CDCl3): d ¼ 157.70, 154.56,
147.73, 144.80, 139.65, 138.64, 131.52, 129.30, 128.93,
128.75, 128.65, 128.30, 127.25, 126.57, 121.79, 119.63,
103.56, 55.38.
1
2,4-Diphenylquinoline (4a) [19]. H NMR (400 MHz,
CDCl3): d ¼ 8.26 (d, J ¼ 8.45 Hz, 1H), 8.21–8.18 (m, 2H),
7.93–7.90 (m, 1H), 7.82 (s, 1H), 7.76–7.72 (m, 1H), 7.57–7.45
(m, 9H); 13C NMR (100 MHz, CDCl3): d ¼ 156.87, 149.20,
148.70, 139.56, 138.33, 130.03, 129.54, 129.35, 128.83,
128.56, 128.40, 127.58, 126.33, 125.73, 125.63, 119.38.
1
6-Chloro-2,4-diphenylquinoline (4j) [22]. H NMR (400
MHz, CDCl3): d ¼ 8.18–8.15 (m, 3H), 7.86 (d, J ¼ 2.36 Hz,
1H), 7.82 (s, 1H), 7.66–7.64 (m, 1H), 7.58–7.50 (m, 7H),
7.48–7.44 (m, 1H); 13C NMR (100 MHz, CDCl3): d ¼ 157.00,
148.39, 147.13, 139.11, 137.66, 132.14, 131.65, 130.40,
129.56, 129.39, 128.86, 128.77, 128.67, 127.48, 126.41,
124.43, 120.00.
1
2-(4-Methylphenyl)-4-phenylquinoline (4b) [20]. H NMR
(400 MHz, CDCl3): d ¼ 8.23 (d, J ¼ 8.45 Hz, 1H), 8.08 (d, J
¼ 8.11 Hz, 2H), 7.86 (d, J ¼ 8.48 Hz, 1H), 7.77 (s, 1H),
7.71–7.67 (m, 1H), 7.53–7.45 (m, 5H), 7.45–7.40 (m, 1H),
7.30 (d, J ¼ 8.10 Hz, 1H), 2.40 (s, 3H); 13C NMR (100 MHz,
CDCl3): d ¼ 156.76, 148.97, 148.70, 139.35, 138.37, 136.70,
129.92, 129.49, 129.39, 128.50, 128.29, 127.39, 126.07,
1
2-Methyl-2,4-diphenylquinoline (4k) [24]. H NMR (400
MHz, CDCl3): d ¼ 8.27 (d, J ¼ 7.85 Hz, 2H), 7.81 (s, 1H),
7.70 (d, J ¼ 8.54 Hz, 1H), 7.55–7.40 (m, 9H), 7.31 (t,
J ¼ 7.56 Hz, 1H), 2.95 (s, 3H); 13C NMR (100 MHz, CDCl3):
d ¼ 154.85, 149.22, 147.64, 139.78, 138.89, 137.90, 129.56,
129.54, 129.20, 128.71, 128.43, 128.16, 127.44, 125.89,
125.62, 123.54, 118.58, 18.39.
125.60, 125.53, 119.38, 21.28.
2-(4-Methoxylphenyl)-4-phenylquinoline
1
[21]. H
(4c)
NMR (400 MHz, CDCl3): d ¼ 8.21 (d, J ¼ 8.22 Hz, 1H),
8.17–8.15 (m, 2H), 7.87 (d, J ¼ 8.35 Hz, 1H), 7.76 (s, 1H),
7.72–7.68 (m, 1H), 7.55–7.49 (m, 5H), 7.45–7.41 (m, 1H),
7.40–7.22 (m, 1H), 3.86 (s, 3H); 13C NMR (100 MHz,
CDCl3): d ¼ 160.76, 156.35, 148.96, 148.70, 138.42, 132.09,
129.80, 129.50, 129.42, 128.86, 128.52, 128.31, 125.92,
125.56, 125.53, 118.85, 114.15, 55.33.
1
2,4-Diphenylbenzo[h]quinoline (4l) [25]. H NMR (400
MHz, CDCl3): d ¼ 9.57 (d, J ¼ 7.58 Hz, 1H), 8.33–8.31 (m,
2H), 7.87 (s, 1H), 7.78 (d, J ¼ 8.00 Hz, 1H), 7.72–7.68 (m,
2H), 7.63–7.59 (m, 2H), 7.51–7.38 (m, 8H); 13C NMR (100
MHz, CDCl3): d ¼ 154.70, 148.88, 146.65, 139.60, 138.71,
133.49, 131.94, 129.59, 129.14, 128.71, 128.48, 128.17,
128.12, 127.51, 127.38, 127.18, 126.78, 125.14, 123.20,
122.75, 119.34.
1
2-(4-Chlorophenyl)-4-phenylquinoline (4d) [18]. H NMR
(400 MHz, CDCl3): d ¼ 8.21 (d, J ¼ 8.45 Hz, 1H), 8.13–8.11
(m, 2H), 7.89–7.87 (m, 1H), 7.74 (s, 1H), 7.73–7.69 (m, 1H),
7.53–7.49 (m, 5H), 7.47–7.43 (m, 3H); 13C NMR (100 MHz,
CDCl3): d ¼ 155.39, 149.30, 148.66, 138.14, 137.89, 135.47,
129.99, 129.63, 129.46, 128.92, 128.74, 128.56, 128.44,
126.47, 125.71, 125.60, 118.81.
1
2-Phenyl-4-p-tolylquinoline (4m) [26]. H NMR (400 MHz,
CDCl3): d ¼ 8.26–8.24 (d, J ¼ 8.63 Hz, 1H), 8.19–8.18 (m,
2H), 7.94 (q, J ¼ 3.75 Hz, 1.2 Hz, 1H), 7.81 (s, 1H), 7.74–
7.71 (m, 1H), 7.54–7.51 (m, 2H), 7.47–7.45 (m, 4H), 7.36 (d,
J ¼ 7.81 Hz, 1H), 2.48 (s, 3H); 13C NMR (100 MHz, CDCl3):
d ¼ 156.86, 149.26, 148.71, 139.62, 138.33, 135.39, 130.00,
129.46, 129.28, 128.81, 127.58, 126.23, 125.84, 125.69,
119.33, 21.31.
1
2-(4-Bromophenyl)-4-phenylquinoline (4e) [18]. H NMR
(400 MHz, CDCl3): d ¼ 8.21 (m, 1H), 8.07–8.05 (m, 2H),
7.90–7.87 (m, 1H), 7.75 (s, 1H), 7.74–7.70 (m, 1H), 7.63–7.61
(m, 2H), 7.54–7.49 (m, 5H), 7.48–7.44 (m, 1H); 13C NMR
(100 MHz, CDCl3): d ¼ 155.45, 149.34, 148.67, 138.36,
138.13, 131.89, 130.00, 129.66, 129.47, 129.03, 128.57,
128.45, 126.51, 125.75, 125.62, 123.89, 118.77.
1
4-(4-Fluorophenyl)-2-phenylquinoline (4n) [27]. H NMR
(400 MHz, CDCl3): d ¼ 8.25–8.22 (m, 1H), 8.18–8.16 (m,
2H), 7.84–7.82 (m, 1H), 7.76 (s, 1H), 7.73–7.69 (m, 1H),
7.53–7.42 (m, 6H), 7.23–7.19 (m, 2H); 13C NMR (100 MHz,
CDCl3): d ¼ 164.06, 161.60, 156.79, 148.74, 148.00, 139.44,
134.27, 134.23, 131.24, 131.15, 130.14, 129.56, 129.36,
128.79, 127.50, 126.41, 125.65, 125.28, 119.31, 115.70,
115.49.
1
2-(3-Chlorophenyl)-4-phenylquinoline (4f). H NMR (400
MHz, CDCl3): d ¼ 8.25 (d, J ¼ 8.54 Hz, 1H), 7.98–7.96 (m,
1H), 7.76–7.71 (m, 2H), 7.70 (s, 1H), 7.57–7.47 (m, 7H),
7.42–7.33 (m, 2H); 13C NMR (100 MHz, CDCl3): d ¼ 156.25,
148.52, 147.95, 139.48, 137.91, 132.30, 131.64, 130.02,
129.98, 129.83, 129.56, 129.46, 128.52, 128.38, 127.12,
126.74, 125.62, 125.56, 122.94. Anal. Calcd. for C21H14ClN:
C, 79.87; H, 4.47; N, 4.44. Found: C, 79.81; H, 4.51; N, 4.52.
1
4-(4-Chlorophenyl)-2-phenylquinoline (4o) [26]. H NMR
(400 MHz, CDCl3): d ¼ 8.25–8.23 (m, 1H), 8.23–8.16 (m,
Journal of Heterocyclic Chemistry
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Iron-Catalyzed Tandem Reactions of Aldehydes, Terminal Alkynes, and Primary
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157
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2H), 7.84–7.81 (m, 1H), 7.76 (s, 1H), 7.74–7.70 (m, 1H),
7.54–7.43 (m, 8H); 13C NMR (100 MHz, CDCl3): d ¼ 156.82,
148.71, 147.80, 139.37, 136.69, 134.55, 130.81, 130.15,
129.64, 129.41, 128.82, 128.81, 127.50, 126.50, 125.42,
125.20, 119.20.
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1
4-(Biphenyl-4-yl)-2-phenylquinoline (4p). H NMR (400
MHz, CDCl3): d ¼ 8.26 (d, J ¼ 8.36 Hz, 1H), 8.19 (d, J ¼
7.80 Hz, 2H), 7.95 (d, J ¼ 8.40 Hz, 1H), 7.82 (s, 1H), 7.74–
7.65 (m, 5H), 7.59 (s, 1H), 7.57 (s, 1H), 7.52–7.41 (m, 6H),
7.39–7.35 (t, J ¼ 7.37 Hz, 1H); 13C NMR (100 MHz, CDCl3):
d ¼ 156.81, 148.77, 148.69, 141.21, 140.33, 139.53, 137.19,
130.08, 129.97, 129.50, 129.30, 128.87, 128.78, 127.60,
127.52, 127.21, 127.08, 126.32, 125.63, 125.54, 119.24. Anal.
Calcd. for C27H19N: C, 90.72; H, 5.36; N, 3.92. Found: C,
90.81; H, 5.38; N, 3.81.
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Journal of Heterocyclic Chemistry
DOI 10.1002/jhet