Ytterbium pentafluorobenzoate as a novel fluorous Lewis acid catalyst in the synthesis of 2,4-disubstituted quinolines

Article abstract of DOI:10.1016/j.tet.2011.09.004

A series of simple, efficient, stable and recoverable rare earth metal pentafluorobenzoates [RE(Pfb)₃] have been synthesized for the first time. A highly efficient and environmentally friendly synthesis of 2,4-disubstituted quinolines catalyzed by Yb(Pfb)₃ via one-pot reaction of aldehydes, alkynes and amines under solvent-free conditions has been explored.

Full text of DOI:10.1016/j.tet.2011.09.004

Tetrahedron 67 (2011) 8465e8469
Contents lists available at SciVerse ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Ytterbium pentafluorobenzoate as a novel fluorous Lewis acid catalyst in the
synthesis of 2,4-disubstituted quinolines
*
Jun Tang, Limin Wang , Dan Mao, Wenbo Wang, Liang Zhang, Shengying Wu, Yongshu Xie
Key Laboratory for Advanced Materials and Institute of Fine Chemicals, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 29 June 2011
Received in revised form 25 August 2011
Accepted 6 September 2011
Available online 8 September 2011
A series of simple, efficient, stable and recoverable rare earth metal pentafluorobenzoates [RE(Pfb) ] have
been synthesized for the first time. A highly efficient and environmentally friendly synthesis of 2,4-
3
disubstituted quinolines catalyzed by Yb(Pfb)
3
via one-pot reaction of aldehydes, alkynes and amines
under solvent-free conditions has been explored.
Ó 2011 Elsevier Ltd. All rights reserved.
Keywords:
Ytterbium pentafluorobenzoate
Lewis acid
Rare earth metal
Quinolines
One-pot reaction
1. Introduction
use, recoverability, especially strong water-tolerated ability, while
the traditional Lewis acid catalysts, like TiCl , AlCl , BF , etc., are
4
3
4
The chemistry of rare earth metals has been under extensive
investigations for the last decades owing to their rich structural
information of rare earth metal complexes and wide applications in
organic chemistry.1 However, most rare earth complexes’ struc-
tures are too complicated to be easily characterized, and they are
extremely unstable in air and water, making the applications of
easily decomposed or deactivated in the presence of even a small
amount of water and need stoichiometric use. Rare earth metal
triflates are so powerful that it has become a common practice to
test rare earth metal triflates in both the known and some new
5
reactions in the last few decades. Therefore, to develop a new type
of fluorous rare earth metal Lewis acid catalyst, which is simple,
stable, efficient, well-characterized, and as powerful as rare earth
metal triflates, is of obvious interest.
2
these complexes far from being an exact science. Because of the
unique properties of fluorous ligands in electronics, thermally
controlled miscibility and interfacial activities, polyfluorinated
complexes as catalysts have been well recognized, especially in
Quinoline and their derivatives occurring in a large number of
6
biologically active natural products attract much attention. Due to
3
field of fluorous biphasic catalysis (FBC). Generally, these catalysts
their widely biological activities, the synthesis of quinolines has
been extensively researched over the years. Kuninobu and co-
have advantages of high activity, low catalytic use and strong
water-tolerated ability. In most cases, the catalysts could be re-
coverable. Importantly, some fluorous catalysts could also be used
directly in organic solvent or solvent-free system. In these cases the
fluorous catalysts can be dissolved with organic solvents or sub-
strates directly at high temperature and be easily separated when
reaction is finished. In this endeavour, the design and synthesis of
metal catalyst coordinated by perfluoroalkylated anion is of great
importance.
7
workers have explored an important methodology that provided
an access to synthesis of 2,4-disubstituted quinoline derivatives
from simple starting materials using CuCl and AgOTf as catalysts.
This methodology has been improved greatly by Wang and co-
8
workers, although it still took a long reaction time (1.5e4 days). Tu
9
co-workers have utilized a single catalyst FeCl
3
to promote the
one-pot reaction of aldehydes, alkynes and amines affording 2,4-
disubstituted quinolines. But the catalyst loading is not satisfac-
tory and the catalyst cannot be recycled. Very recently, a micro-
wave-assisted methodology promoted by a solid acid catalyst was
4
Rare earth metal triflates, which represent the classic fluorous
Lewis acid catalysts, have the advantages of high activity, catalytic
10
also developed for this transformation. Further investigations are
still needed for this transformation, especially to build an envi-
ronmentally friendly methodology of one-pot reaction catalyzed by
a single catalyst, which is catalytic use and reusable.
*
Corresponding author. Tel./fax: þ86 21 64253881; e-mail addresses: wangli-
min@ecust.edu.cn, Liming.wang@qub.ac.uk (L. Wang).
0
040-4020/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2011.09.004

8466
J. Tang et al. / Tetrahedron 67 (2011) 8465e8469
2
. Results and discussion
Table 1
The one-pot synthesis of 2,4-diphenylquinoline under various experimental
a
conditions
Herein, we have synthesized a series of air-stable and water-
tolerated rare earth metal pentafluorobenzoates [RE(Pfb) ] for the
3
first time. These complexes have been prepared from penta-
fluorobenzoic acid and excess rare earth metal oxides at reflux in
Ph
CHO
NH
2
Cat.
Air
+
+
Ph
N
1
a
water and THF (H
analyses were grown from
fluorobenzoate in dioxane/hexane. X-ray crystal structure analyses
revealed a coordination polymer structure of [Yb(C COO)
O) $2n diox (Fig. 1). In the crystal structure, each Yb(III) atom
2
O/THF¼1/4) for 24 h. Crystals suitable for X-ray
a
solution of ytterbium penta-
ꢀ
Yieldb (%)
Entry
Cat.
Solvent
CH ClCH
PhCH
Temp ( C)
Time (h)
F
6 5
3
1
2
3
4
5
6
7
8
9
Yb(Pfb)
Yb(Pfb)
Yb(Pfb)3
Yb(Pfb)
Yb(Pfb)
3
3
2
2
Cl
Reflux
Reflux
35
Reflux
80
80
80
80
80
24
24
48
48
12
12
12
12
12
48
48
48
48
45
82
10
Trace
90
60
Trace
95
(
H
2
2 n
]
3
is coordinated to eight O atoms, donated by a chelating penta-
fluorobenzoate, four bridging pentafluorobenzoates and two ter-
minal water molecules. Thus a coordination polymer with a chain
CH Cl2
2
3
3
EtOH
None
None
None
None
None
None
None
None
None
11
Yb(OTf)
M(Pfb)
Sc(Pfb)
3
c
structure is formed by the linkage of the bridging carboxylates.
3
3
d
88 (90, 88, 87)e
Trace
Trace
Trace
Trace
Yb(Pfb)
None
3
10
11
12
13
80
FeCl
AlCl
ZnCl
3
110
110
110
3
3
a
A mixture of aniline (1 mmol), benzaldehyde (1 mmol), phenylacetylene
(1.5 mmol) and catalyst (10 mol %) were stirred one-pot either with solvent (2 mL)
or not.
b
Isolated yields.
c
M¼La, Sm, Eu, Dy.
d
e
The catalyst loading was 2 mol %.
The catalyst was recycled and reused for three times.
extremely excellent catalytic activity affording the desired product
in 95% yield. However, considering the high price of scandium, fur-
ther investigations for Yb(Pfb) catalyzing the one-pot reactionwere
3
still conducted. We found the best catalyst loading was 2 mol %, and
the catalyst could be recycled and reused for three times without
significant loss of activity (Table 1, entry 9). To evaluate the back-
ground reaction, a mixture of benzaldehyde, aniline and phenyl-
acetylene was stirred in one-pot under solvent-free conditions
without catalyst. Trace product was detected after 48 h reaction. We
also did not detect any desired product in the cases of some tradi-
tional Lewis acids as catalyst in the solvent-free conditions (Table 1,
Fig. 1. A chain structure of [Yb(C
Lattice dioxane molecules, fluorine and hydrogen atoms are omitted for clarity.
6 5 3 2 2 n
F COO) (H O) ] $2n diox: green, Yb; red, O; black, C.
The RE(Pfb)
3
are very stable in air and water-tolerated just as
1
2
16
19
19
23
23
139
RE(OTf) . The peaks of 794.8431(100%) ( C21, O6, F15, Na,
3
139
12
13
16
La) and 795.8478(18.36%) ( C20, C, O6, F15, Na,
La)
were found in lanthanum pentafluorobenzoate’s electrospray ion-
ization mass spectrometry (methanol as solvent). Thermograv-
imetry-differential thermal analysis (TG-DTA) shows that Yb(Pfb)
loses two molecules of crystallization water at about 130 C, and the
dehydrated complex is decomposed at about 400 C. The thermal
stability of the complex up to 400 C is probably essential to further
ꢀ
entries 11e13), even if the temperature was increased to 110 C.
As shown in Table 2, the substrate scope of one-pot reaction of
aldehydes, alkynes and amines affording 2,4-disubstituted quino-
3
ꢀ
ꢀ
lines catalyzed by 2 mol % of Yb(Pfb)
3
under solvent-free conditions
ꢀ
applications. The spectrogram was provided in Supplementary
data.
Table 2
a
Scope of one-pot synthesis of 2,4-disubstituted quinolines catalyzed by Yb(Pfb)
3
As an extension of our contributions in the field of rare earth
Ph
12
metal Lewis acid mediated one-pot reaction synthesis, we hope
Yb(Pfb) could promote the one-pot reaction of aldehydes, alkynes
CHO
NH2
Yb(Pfb)
3
3
R2
+
+Ph
Neat, air
and amines affording 2,4-disubstituted quinolines efficiently. As
shown in Table 1, a mixture of aniline, benzaldehyde, phenyl-
N
1
R1
R1
R2
3
acetylene and 10 mol % of Yb(Pfb) were stirred in refluxing 1,2-
dichloroethane for 24 h. To our delight, the desired product 1a
was isolated in 45% yield successfully. Then the effect of the solvent
on the reaction was examined. Toluene was found to be the best
solvent, with which the product was obtained in 82% yield (Table 1,
entries 1e4). Recently, solvent-free condition is highly demanded
in the context of green chemistry. So we tried to carry out the re-
action without solvent.
ꢀ
Yieldb (%)
Entry
R1
R2
H
4-OCH
4-CH
4-F
4-Cl
3-Cl
2-Cl
H
H
H
H
H
Temp ( C)
Product
1
2
3
4
5
6
7
8
9
H
H
H
H
H
H
H
80
80
80
80
80
80
80
80
80
1a
1b
1c
1d
1e
1f
1g
1h
1i
88
90
92
89
92
65
75
89
91
62
70
63
Trace
3
3
Very exciting, the desired product was obtained in 90% yield
4-CH
4-OCH3
4-Cl
4-NO
2-NO
3-NO2
3
ꢀ
with 12 h heating at 80 C.
1
1
1
0
1
2
80
1j
1k
1l
To prove our catalyst’s superiority, the reaction was catalyzed by
Yb(OTf) as comparison and the desired product was afforded in 60%
3
yield. Some other rare earth metal pentafluorobenzoates were also
tested for this reaction (Table 1, entries 7e8). Interestingly, all other
tested rare earth metal pentafluorobenzoates showed no catalytic
2
120
120
120
2
13
H
1m
a
A mixture of amine (1 mmol), aldehyde (1 mmol), phenylacetylene (1.5 mmol)
and Yb(Pfb)3 (2 mol %) were stirred one-pot for 12 h without solvent.
b
activity for this reaction except scandium. Sc(Pfb)
3
revealed
Isolated yields.

J. Tang et al. / Tetrahedron 67 (2011) 8465e8469
8467
was examined. Both electron-deficient and electron-rich 4-
substitutied anilines provided excellent yields (Table 2, entries
e5). But ortho and meta substituted anilines are not the suitable
substrates for this protocol (Table 2, entries 6e7). Electron-rich
aldehydes reacted with aniline and phenylacetylene very
smoothly in excellent yields (Table 2, entries 8 and 9). Several
CHO
2
H
N
N
Yb(Pfb)3
Solvent-free
+
+
Ph
2n
electron-deficient aromatic aldehydes need harsher conditions
ꢀ
(
120 C heating), and 3-nitrobenzaldehyde could not afford the
Scheme 3. The corresponding propargylamine was obtained in the case of piperidine.
desired product. Aliphatic aldehydes are not suitable substrates for
this reaction. It is noteworthy that a potential chiral ligand 1n was
obtained in excellent yield (Scheme 1). The application of this
easily-prepared chiral ligand, which has the advantages of good
stereoselectivity and ability of complex with metals, is under fur-
ther investigation in our laboratory.
3. Conclusion
In summary, we have synthesized a series of rare earth metal
pentafluorobenzoates from the direct reaction of penta-
2 3
fluorobenzoic acid and RE O for the first time. The ytterbium
pentafluorobenzoate showed excellent Lewis acid ability in cata-
lyzing one-pot synthesis of 2,4-disubstituted quinoline derivatives.
The methodology has the advantages of good to excellent yields,
readily available starting materials, solvent-free during the reaction
3
process, catalytic use and reuse of catalyst. The RE(Pfb) are well-
characterized, simple, efficient, water-tolerated, air and thermal
stable, with potential wide range of applications in Lewis acid ca-
talysis and green chemistry.
4. Experimental section
0
0
4.1. Synthesis and characterization of rare earth metal
Scheme 1. One-pot synthesis of (S)-3-(4-phenylquinolin-2-yl)-1,1 -binaphthyl-2,2 -
diol as a potential chiral ligand.
pentafluorobenzoates
A series of rare earth metal pentafluorobenzoates was prepared
from pentafluorobenzoic acid and excess rare earth oxides in water
According to the above results, our proposed mechanism of the
one-pot synthesis of 2,4-diphenylquinolines is depicted in
and THF (H
2
O/THF¼1/4) at reflux for 24 h. More water was added to
Scheme 2. The mechanism of the reaction catalyzed by Yb(Pfb)
might be similar with the reaction catalyzed by other Lewis acids,
3
dilute the suspension when the reaction finished. The filtrate ob-
tained from high speed centrifugal separation was collected and
removed the solvent. Then water was added again to redissolve it,
and the resulting solution was filtered carefully. The white powders
III
3 3
like AuCl , FeCl . However, Yb may perform better catalytic ac-
tivity on both processes of imine addition and cyclization, and the
water in the reaction system cannot make the catalyst deactivate or
decompose. The intermediate 2a was failed to be isolated. But in the
case of piperidine, the corresponding propargylamine 2n was ob-
tained in 85% yield (Scheme 3). We believe that 2a is an important
intermediate, and this one-pot reaction undergoes domino imine
formation, imine addition, cyclization and oxidation.
ꢀ
were obtained after the filtrates were collected and dried at 120 C
in vacuum for 4 h.
The Inductively Coupled Plasma spectrometry (ICP) of ytterbium
pentafluorobenzoate showed the content of Yb as 21.9% (the the-
oretical value is 21.5%). It was supported that the expected metal-
1
9
eligand ratio (Yb/C
6 5
F COO) was 1/3. Compared with the F NMR of
19
pentafluorobenzoic acid, Nd and Gd pentafluorobenzoates’
F
YbIII
NMR showed all peaks were shifted to low field for about 3 ppm,
and the peaks of the two F atoms near the carboxyl were split to
double-peaks. Rare earth metal pentafluorobenzoates’ infrared
spectrums (IR) showed the pentafluorobenzoic acid’s two strong
CHO
+
NH2
N
-
H O
2
H
ꢁ
1
ꢁ1
19
absorption peaks
n
]
C O
(3000 cm ),
n
OeH (1716 cm ) all dis-
12
16
19
23
139
appeared. The peaks of 794.8431(100%) ( C21, O6, F15, Na,
H
139
12
13
16
23
YbIII
La) and 795.8478(18.36%) ( C20, C, O6, F15, Na,
La)
N
were found in lanthanum pentafluorobenzoate’s electrospray ion-
ization mass spectrometry (ESI-MS) clearly illustrating its structure
Imine addition
6 5
is La(C F COO)3.
2a
4.2. General procedure for synthesis of 1ael
A mixture of amine (1 mmol), aldehyde (1 mmol), phenyl-
acetylene (1.5 mmol) and ytterbium pentafluorobenzoate (2 mol %)
was stirred one-pot without solvent at 80 C or 120 C for 12 h.
When the reaction was finished, the mixture was cooled to room
2 2
temperature and washed by CH Cl . The residue is the catalyst that
Cyclization
Oxidation
Air
ꢀ
ꢀ
N
N
can be directly used in next cycle reaction. The organic layer was
concentrated in vacuo, purified by chromatography affording the
desired product 1ael (EtOAc/Petroleum ether¼1:20 to 1:10). When
the catalyst had good solubility with the substrates at room
3
a
1a
Scheme 2. The proposed mechanism of one-pot synthesis of 2,4-diphenylquinoline
catalyzed by Yb(Pfb)3.

8468
J. Tang et al. / Tetrahedron 67 (2011) 8465e8469
temperature, the reaction mixture was extracted by CH
2
Cl
2
and
129.54, 129.35, 128.66, 128.45, 127.56, 126.23, 125.78, 125.70,
þ
H
2
O. The organic layer was dried with Na SO , concentrated in
2
4
119.26, 21.45. HRMS, M , found 295.1360, C22
295.1361.
H17N requires
vacuo, purified by chromatography affording the desired product.
The water layer, which contains the catalyst, was dried in vacuo.
The catalyst was then recovered and reused for next reaction.
4.3.9. 2-(4-Methoxyphenyl)-4-phenylquinoline (1i). 1H NMR (400
MHz, CDCl
3.89 (s, 3H), 7.06 (d, J¼8.8 Hz, 2H), 7.43e7.47 (m, 1H),
7.52e7.57 (m, 5H), 7.70e7.74 (m, 1H), 7.79 (s, 1H), 7.89 (d, J¼8.4 Hz,
3
) d
1
4
.3. The H and 13C spectrum of the desired product
13
1
3
H), 8.17e8.24 (m, 3H); C NMR (100 MHz, CDCl ) d 160.87, 156.47,
4
d
.3.1. 2,4-Diphenylquinoline (1a). 1
7.47e7.58 (m, 9H), 7.75 (t, J¼7.2 Hz, 1H), 7.85 (s, 1H), 7.93 (d,
H
NMR (400 MHz, CDCl
3
)
149.03, 148.85, 138.55, 132.25, 129.93, 129.59, 129.47, 128.94,
128.60, 128.38, 125.99, 125.65, 125.55, 118.93, 114.25, 55.41. HRMS,
13
þ
J¼8.4 Hz, 1H), 8.23 (d, J¼7.2 Hz, 2H), 8.28 (d, J¼8.4 Hz, 1H); C NMR
100 MHz, CDCl 156.93, 149.20, 148.88, 139.71, 138.46, 130.19,
29.61,129.55, 129.38, 128.88, 128.53, 128.44,127.63, 126.37, 125.82,
M , found 311.1311, C22
H17NO requires 311.1310.
(
1
3
) d
4.3.10. 2-(4-Chlorophenyl)-4-phenylquinoline (1j). 1H NMR (400
MHz, CDCl 7.49e7.56 (m, 8H), 7.73e7.78 (m, 2H), 7.91 (d,
J¼8.0 Hz, 1H), 8.16 (d, J¼8.4 Hz, 2H), 8.23 (d, J¼8.4 Hz, 1H); C NMR
100 MHz, CDCl 155.55, 149.44, 148.79, 138.27, 138.05, 135.58,
þ
125.88, 119.39. HRMS, M , found 281.1203, C21
H15N requires
3
) d
13
2
81.1204.
(
3
) d
4
.3.2. 6-Methoxy-2,4-diphenylquinoline (1b). 1H NMR (400 MHz,
130.01, 129.72, 129.55, 129.03, 128.85, 128.65, 128.52, 126.56,
þ
CDCl
3
)
d
3.81 (s, 3H), 7.20 (d, J¼2.4 Hz, 1H), 7.39e7.47 (m, 2H),
125.85, 125.71, 118.92. HRMS, M , found 315.0817, C21
H14ClN re-
13
7.50e7.60 (m, 7H), 7.79 (s,1H), 8.15e8.18 (m, 3H); C NMR (100 MHz,
quires 315.0815.
CDCl
3
)
d
157.86, 154.62, 147.81, 145.00, 139.80, 138.81, 131.67, 129.44,
129.05, 128.86, 128.77, 128.42, 127.37, 126.71, 121.88, 119.66, 103.73,
4.3.11. 2-(4-Nitrophenyl)-4-phenylquinoline (1k). 1
MHz, CDCl 7.51e7.57 (m, 6H), 7.75e7.79 (m, 1H), 7.82 (s, 1H), 7.93
d, J¼8 Hz, 2H), 8.25 (d, J¼8.4 Hz, 1H), 8.30e8.36 (m, 4H); C NMR
(100 MHz, CDCl 153.97, 149.85, 148.82, 148.31, 145.36, 137.93,
H NMR (400
þ
5
5.45. HRMS, M , found 311.1310, C22
H17NO requires 311.1310.
3
) d
13
(
4
.3.3. 6-Methyl-2,4-diphenylquinoline (1c). 1H NMR (400 MHz,
3
) d
CDCl
.12e8.16 (m, 3H); C NMR (100 MHz, CDCl
47.55, 139.85, 138.75, 136.36, 131.89, 130.00, 129.68,129.29, 128.92,
28.70, 128.42, 127.61, 125.83, 124.52, 119.49, 115.34, 21.94. HRMS,
3
)
d
2.40 (s, 3H), 7.37e7.54 (m, 9H), 7.62 (s, 1H), 7.73 (s, 1H),
130.36, 130.07, 129.55, 128.77, 128.27, 127.37, 126.17, 125.79, 123.97,
13
þ
8
1
1
3
)
d
156.07, 148.54,
119.05. HRMS, M , found 326.1057, C21
H N O
14 2 2
requires 326.1055.
4.3.12. 2-(2-Nitrophenyl)-4-phenylquinoline (1l). 1
MHz, CDCl 7.39e7.45 (m, 8H), 7.54e7.57 (m, 1H), 7.64e7.68 (m,
H), 7.86e7.90 (m, 2H), 8.14 (d, J¼8.4 Hz, 1H). C NMR (100 MHz,
CDCl 155.18, 149.35, 149.30, 148.54, 137.72,135.67, 132.75, 131.67,
H NMR (400
þ
M , found 295.1359, C22
H17N requires 295.1361.
3
) d
13
2
4
.3.4. 6-Fluoro-2,4-diphenylquinoline (1d). 1
H
NMR (400 MHz,
3
) d
CDCl
3
)
d
7.26e7.59 (m, 10H), 7.85 (s, 1H), 8.18e8.20 (m, 2H), 8.25
130.11, 129.93, 129.65, 129.52, 128.71, 127.20, 125.79, 124.55, 120.80.
13
þ
(
1
1
1
dd, J¼5.2, 8.8 Hz, 1H); C NMR (100 MHz, CDCl
59.38), d (156.33, 156.30), d (148.72, 148.67), 145.98, 139.38,
38.00, d (132.63, 132.55), 129.45, 129.40, 128.91, 128.82, 128.68,
27.49, d (126.59, 126.49), 119.88, d (119.82, 119.57), d (109.20,
3
)
d
d (161.84,
HRMS, M , found 326.1055, C21
H
14
N
2
O
2
requires 326.1055.
4.3.13. (S)-2,2 -Dihydroxy-1,1 -binaphthyl-3-carbaldehyde(1n). 1H
NMR (400 MHz, CDCl 13.41(br, 1H), 8.91 (s, 1H), 8.16 (s, 1H),
7.86e7.98 (m, 4H), 7.44e7.14 (m, 15H), 5.11 (br, 1H). C NMR
100 MHz, CDCl 162.03, 155.53, 152.78, 151.52, 147.79, 135.78,
0
0
3
) d
þ
13
108.97). HRMS, M , found 299.1112, C21
H14FN requires 299.1110.
(
3
) d
4
.3.5. 6-Chloro-2,4-diphenylquinoline (1e). 1
H
NMR (400 MHz,
135.69, 133.60, 133.44, 131.44, 130.18, 129.56, 129.48, 129.38, 129.16,
128.44, 128.33, 127.91, 127.58, 127.51, 126.63, 124.86, 124.77, 124.22
CDCl 7.46e7.60 (m, 8H), 7.68 (dd, J¼2.4, 9.2 Hz, 1H), 7.84 (s, 1H),
3
) d
13
7
.88 (d, J¼2.4 Hz,1H), 8.17e8.20 (m, 3H); C NMR (100 MHz, CDCl
3
)
(two signals overlapped), 124.07, 123.40, 121.43, 121.25, 117.80,
þ
d
157.08, 148.45, 147.26, 139.22, 137.78, 132.23, 131.77, 130.46,
29.62, 129.48, 128.93, 128.85, 128.74, 127.56, 126.51, 124.51, 120.04.
117.75, 114.36, 114.00. HRMS, [Mþ1] , found 490.1790, C35
H23NO
2
1
requires 490.1807.
þ
HRMS, M , found 315.0815, C21
H14ClN requires 315.0815.
4
.3.14. 1-(1,3-Diphenylprop-2-ynyl)piperidine (2n). 1H NMR (400
MHz, CDCl 1.43e1.47 (m, 2H), 1.56e1.64 (m, 4H), 2.57 (t,
J¼4.8 Hz, 4H), 4.80 (s, 1H), 7.29e7.38 (m, 6H), 7.51e7.54 (m, 2H),
4
.3.6. 7-Chloro-2,4-diphenylquinoline (1f). 1
H
NMR (400 MHz,
3
) d
3
CDCl ) d
7.37 (dd, J¼7.6, 8.4 Hz, 1H), 7.47e7.58 (m, 8H), 7.82 (dd,
1
3
J¼1.2, 8.4 Hz, 1H), 7.86 (dd, J¼1.2, 7.6 Hz, 1H), 7.91 (s, 1H), 8.32e8.34
m, 2H); 13C NMR (100 MHz, CDCl
156.81, 149.76, 144.96, 139.08,
38.16, 134.45, 129.84, 129.71, 129.61, 128.94, 128.71, 128.66, 127.76,
7.64 (d, J¼7.2 Hz, 2H). C NMR (100 MHz, CDCl
3
) d 138.58, 131.82,
(
1
3
)
d
128.56, 128.28, 128.06 (two signals overlap), 127.46, 123.35, 87.84,
86.08, 62.40, 50.72, 26.18, 24.44. HRMS, M , found 275.1676,
þ
þ
127.35, 125.97, 124.87, 119.73. HRMS, M , found 315.0815,
20
C H21N requires 275.1674.
21
C H
14ClN requires 315.0815.
4
.3.15. Gadolinium pentafluorobenzoate [Ga(Pfb)
]. 19F NMR (470
3
4
.3.7. 8-Chloro-2,4-diphenylquinoline (1g). 1
CDCl
7.42 (dd, J¼2.4, 9.2 Hz, 1H), 7.47e7.59 (m, 8H), 7.82 (s, 1H),
.84 (d, J¼8.8 Hz, 1H), 8.18e8.20 (m, 2H), 8.24 (d, J¼2 Hz, 1H);
NMR (100 MHz, CDCl 157.87, 149.34, 149.23, 139.19, 137.96,
35.46, 129.71, 129.50, 129.01, 128.91, 128.76, 128.69, 127.62, 127.22,
H
NMR (400 MHz,
MHz DMSO) 140.44 (s, 2F), 155.76 (s, 1F), 163.46 (s, 2F).
d
3
) d
13
]. 19
d 140.13e140.43 (m, 2F), 155.73 (s, 1F), 163.44 (s,
7
C
4.3.16. Neodymium pentafluorobenzoate [Nd(Pfb)
(470 MHz DMSO)
2F).
3
F
NMR
3
)
d
1
1
þ
27.08, 124.25, 119.41. HRMS, M , found 315.0817, C21
H14ClN re-
quires 315.0815.
Acknowledgements
4
d
.3.8. 4-Phenyl-2-p-tolylquinoline (1h). 1H NMR (400 MHz, CDCl
2.39 (s, 3H), 7.29 (d, J¼8.0 Hz, 2H), 7.39e7.42 (m, 1H), 7.45e7.51
3
)
This research was financially supported by the National Nature
Science Foundation of China (20672035) and Key Laboratory of
Organofluorine Chemistry, Shanghai Institute of Organic Chemistry,
Chinese Academy of Sciences.
(
(
d
m, 5H), 7.65e7.70 (m, 1H), 7.77 (s, 1H), 7.86 (d, J¼8.4 Hz, 1H), 8.08
13
d, J¼8 Hz, 2H), 8.22 (d, J¼8.4 Hz, 1H); C NMR (100 MHz, CDCl
3
)
156.90, 149.10, 148.93, 139.49, 138.57, 136.91, 130.15, 129.66,

J. Tang et al. / Tetrahedron 67 (2011) 8465e8469
8469
Supplementary data
Du, D.; Wang, Z. Chem.dEur. J. 2009, 15, 324; (f) Aplander, K.; Ding, R.;
Lindstr o€ m, U. M.; Wennerberg, J.; Schultz, S. Angew. Chem., Int. Ed. 2007, 46,
4543.
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.tet.2011.09.004.
6
. (a) Adsule, S.; Barve, V.; Chen, D.; Ahmed, F.; Dou, Q. P.; Padhye, S.; Sarkar, F. H. J.
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