Synthesis and catalytic applications of sulfonate β-ketoimine and β-diimine in the Suzuki reaction in aqueous phase

Article abstract of DOI:10.1016/j.jorganchem.2008.08.038

A series of sulfonated β-ketoimine and β-diimine compounds were synthesized and characterized. As supporting ligands they were used in the Suzuki cross-coupling reaction in aqueous phase with PdCl₂ as catalyst. The new catalytic system can tolerate a wide range of substrates.

Full text of DOI:10.1016/j.jorganchem.2008.08.038

Journal of Organometallic Chemistry 693 (2008) 3692–3696
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis and catalytic applications of sulfonate b-ketoimine and b-diimine in the
Suzuki reaction in aqueous phase
*
Xuming Guo, Jin Zhou, Xiaoyan Li, Hongjian Sun
School of Chemistry and Chemical Engineering, Shandong University, Shanda Nanlu 27, Jinan 250100, People’s Republic of China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 4 August 2008
Received in revised form 27 August 2008
Accepted 29 August 2008
Available online 8 September 2008
A series of sulfonated b-ketoimine and b-diimine compounds were synthesized and characterized. As
supporting ligands they were used in the Suzuki cross-coupling reaction in aqueous phase with PdCl2
as catalyst. The new catalytic system can tolerate a wide range of substrates.
Ó 2008 Elsevier B.V. All rights reserved.
Keywords:
Suzuki reaction
Aryl bromide
Aryl boric acid
b-Ketoimine
b-Diimine
Palladium chloride
1. Introduction
the room-temperature Suzuki cross-coupling reaction with good
to excellent yields and high turnover numbers [21].
The homogeneous palladium-catalyzed cross-coupling reaction
of aryl halides with aryl boronic acids in the presence of base, the
Suzuki reaction, has become an important method for generating
carbon–carbon bond, in particular for a convenient formation of
biaryls, because of its higher stability, wide range functional group
tolerance in the reaction partners [1–10]. Most of these reactions
were performed in traditional organic solvents and resulted in con-
siderable environmental pollution. Therefore, the replacement of
organic solvents by water has received remarkable attention in
catalysis. Some water-soluble catalysts for the Suzuki reaction
have been developed [11–17]. But most of the water-soluble cata-
lysts are palladium complexes with polar oder ionic phosphorus-li-
gand [18].
b-Ketomine and b-diimine can be also used as supporting li-
gands in the olefin polymerization [22,23]. Kirchner reported an
efficient synthesis of N,N0-diaryl and dialkyl b-diimines with the
central carbon atom as part of five- and six-membered ring
systems. At the same time, the catalytic activity of palladium(II)
compounds with these ligands has been studied in N-methyl-2-
pyrrolidone as a solvent for C–C coupling reactions [24].
In this paper we report on the synthesis, characterization and
some applications of b-ketomines and b-diimines as supporting li-
gands in the palladium-catalyzed Suzuki reaction in aqueous
phase. Reaction conditions were optimized for catalytic perfor-
mance. This catalytic system was also examined using different
substrates.
Instead of phosphorus-containing ligands, some nitrogen-
containing ligands in combination with palladium compounds
were used in the Suzuki reaction. A family of sulfonamide-based
palladium complexes and phenylhydrazine-based palladacycles
have been applied in the Suzuki reaction [19]. Liu et al. found that
2. Results and discussion
2.1. Synthesis of sulfonated b-ketoimines and b-diimines
the cylcopalladated complex [Pd(Cl)(j
2N,C–CH2C6H2(Me)2-
CH@NC6H3(Pri)2)2 is an excellent catalyst for Suzuki crossing-cou-
pling reactions in aqueous medium under aerobic conditions [20].
Zhang et al. developed a Pd(OAc)2/guanidine aqueous system for
2,6-Dialkyl anilines were sulfonated at 180–190 °C with con-
centrated sulfuric acid in yields of 65–75% (Scheme 1) [25,26].
The condensation of acetylacetone with the sulfonated 2,6-dial-
kyl anilines (1a–d) in the ratio of 1:1.1 in the presence of catalytic
amounts of formic acid affords b-ketoimines (2a–d) in yields of 80–
90% (Scheme 2). The sulfonated b-diimines (3a–d) were obtained
by reaction of sulfonated anilines (1a–d) with acetylacetone
(2:1.05) in the presence of hydrochloric acid in yields of 60–65%
* Corresponding author. Tel.: +86 531 88361350; fax: +86 531 88564464.
E-mail address: hjsun@sdu.edu.cn (H. Sun).
0022-328X/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2008.08.038

X. Guo et al. / Journal of Organometallic Chemistry 693 (2008) 3692–3696
3693
Table 1
NH2
Ligand optimization in aqueous Suzuki coupling reactiona
NH2
R
R
R
Yieldb (%)
H2SO4 , 180-190 0C
R
Entry
Ligand
L:Pd
1)
1
2
3
4
5
6
No
2c
2c
2c
3a
3a
46
92c
96
81
93
73
2) NaHCO3
1:1
1:1
1.5:1
1:1
1.5:1
SO3 Na
1a-1d
R = CH(CH3 )2, C2H5, CH3, H
a
Reaction conditions: 1.0 mmol bromobenzene, 1.5 mmol phenylboronic acid,
1a, 1b, 1c, 1d
1% Pd, 80 °C, 2 ml water, 1.5 mmol KOH, 0.5 mmol tetrabutylammonium bromide.
b
GC yield after 2 h.
c
Under aerobic conditions.
Scheme 1.
(Scheme 3). The formation of b-ketoimines (2a–d) and b-diimines
(3a–d) were monitored by UV-spectroscopy using the C@N absorp-
tion band of the b-ketoimines (2a–d) at 317 nm which is separated
from that of the anilines (at about 250 nm). Similarly, for the C@N
group in the b-diimines the UV-absorption is shifted to 343 nm
(3a–d) from that of 250 nm for the anilines (1a–d).
All b-ketoimine and b-diimine compounds were characterized
by IR, 1H NMR, MS, and elemental analysis. The molecular and
crystal structure of the b-diimine 3b was determined through X-
ray diffraction [27].
acts as phase-transfer agent, but also forms PhB(OH)3ꢀBu4N+
[31–33].
Under same catalytic conditions, different bases were investi-
gated in the experiments (Table 2). Here potassium hydroxide gave
the best catalytic result. K2CO3, an effective base for the cyclopalla-
dated-imine catalyst in the Suzuki reaction [34], proved to be
slightly inferior to KOH, leading to a 92% isolated yield (Table 2, en-
try 5). Na2CO3 and NaHCO3 are slightly inferior to K2CO3 (Table 2,
entry 1 and 2). Other bases such as KOtBu, N(CH2CH3)3, NaOMe,
and NaOAc, proved to be less effective for the cross-coupling of
bromobenzene with phenylboronic acid (Table 2, entries 3, 6–8).
In Table 3 the results with different ligands are compared. We
observed that the coupling of bromobenzene and phenylbornic
acid in the presence of 1 mol% of PdCl2 and KOH in water at
80 °C without any supporting ligand, gave 42% isolated yield (Table
3, entry 1). The addition of the b-ketoimine or the b-diimine li-
gands in the catalytic system remarkably improved the yields (Ta-
ble 3, entries 2–9). With different substitutents in 2, 6-positions of
the phenyl ring different trends of the sulfonated Pd/b-ketoimine
system and the sulfonated Pd/b-diimine system were observed.
For the sulfonated Pd/b-ketoimine system, ligand 2c gave the high-
est yield (Table 3, entry 4); while ligand 3a brought the highest
2.2. The Suzuki reaction
The reaction of bromobenzene with phenyl boronic acid in
aqueous phase was selected to study the catalytic conditions
(Scheme 4). The results are collected in Table 1. The yields with
the ratio of ligand/palladium (1:1) are higher than those with a ra-
tio (1.5:1) (Table 1, entry 4 and 3; entry 6 and 5). This conclusion is
consistent with the catalytic system of phosphine ligands where
the yields under aerobic conditions are lower than under inert
atmosphere (N2) (Table 1, entry 2 and 3) [28–30].
In these catalytic conditions the presence of tetrabutylammo-
nium bromide (TBAB) is crucial, possibly because it not only
NH2
R
R
R
MeOH,
formic acid
O
N
+
reflux, 48h
O
O
R
SO3Na
SO3Na
1a-1d
2a-2d
Scheme 2.
NH2
R
R
R
R
hydrochloric acid
N
R
N
R
+
reflux, 48h
MeOH,
O
O
HO3S
SO3Na
SO3Na
1a-1d
3a-3d
Scheme 3.
PdCl2 / Ligands
KOH
Br
(OH)2B
+
Scheme 4.

3694
X. Guo et al. / Journal of Organometallic Chemistry 693 (2008) 3692–3696
Table 2
Table 4
Effect of base in water Suzuki coupling reactiona
Aqueous Suzuki coupling reaction of bromobenzene and phenylboronic acida
Entry
Base
Yieldb (%)
Entry
L (mol%)
Solvent (1:1)
TBAB (equiv.)
t (h)
Yieldb
1
2
3
4
5
6
7
8
Na2CO3
NaHCO3
K(OtBu)
KOH
76
84
35
96
92
33
29
31
1
2
3
4
5
6
7
8
2c (0.1)
2c (0.1)
2c (0.1)
H2O/CH3CN
H2O/C2H5OH
H2O/CH3COCH3
H2O
H2O
H2O
0.5
0.5
0.5
0.5
3
3
3
3
6
3
9
3
3
3
6
2
95
95
94
96
78
96c
95c
94
93
91
72
92c
2c (0.05)
2c (0.03)
2c (0.03)
2c (0.01)
3a (0.1)
3a (0.05)
3a (0.05)
3a (0.03)
3a (0.03)
K2CO3
N(CH2CH3)3
NaOMe
NaOAc
H2O
H2O/CH3CN
H2O/CH3CN
H2O
H2O
H2O
0.5
0.5
9
a
Reaction conditions: 1.0 mmol bromobenzene, 1.5 mmol phenylboronic acid,
1% PdCl2, 1% 2c, 80 °C, 2 ml water, 1.5 mmol base, 0.5 mmol tetrabutylammonium
bromide (TBAB).
10
11
12
b
GC yield after 2 h.
a
Reaction conditions: 1.0 mmol bromobenzene, 1.5 mmol phenylboronic acid,
80 °C, 2 ml solvent, 1.5 mmol base.
b
Isolated yields, all reactions were monitored by GC, yields are average of two
Table 3
runs.
Influence of ligands on the palladium-catalyzed Suzuki reaction of bromobenzene
c
At 100 °C.
with phenylboronic acida
Entry
Ligand
Yieldb
1
2
3
4
5
6
7
8
9
No L
2a
2b
2c
2d
3a
3b
3c
42c
91
93
96
87
93
90
88
84
Table 5
Suzuki coupling reactions of arylbromides with various arylboronic acidsa
Entry
X
Y
Z
t (h)
Yield(%)b
1
2
3
Br
Br
Br
H
H
H
H
3
3
2
93c
97
4-Me
4-OMe
95
93c
97
3d
4
5
6
7
8
Br
Br
Br
Br
Br
H
4-Cl
H
4-Me
4-OMe
4-Cl
2
6
4
3
4
a
Reaction conditions: 1.0 mmol bromobenzene, 1.5 mmol phenylboric acid,
4-Me
4-Me
4-Me
4-Me
95
95
94
80 °C, 2 ml water, 1.5 mmol base, 0.5 mmol tetrabutylammonium bromide,
b
Isolated yields, all reactions were monitored by GC, yields are average of two
runs.
94
c
92c
90
A large amount of palladium black was observed.
9
Br
Br
Br
Br
4-OMe
4-OMe
4-OMe
4-OMe
H
4
5
4
3
10
11
12
4-Me
4-OMe
4-Cl
94
93
yield (Table 3, entry 6) for the sulfonated Pd/b-diimine system. We
conclude that both steric and electronic effects of these ligands
play a role in the catalytic system. A detailed analysis of these
trends is presently not feasible. In the Pd/b-diimine system steric
effects are decisive, because ligand 3a with the more bulky iso-pro-
pyl groups gives superior yields.
From Table 4 we conclude that the palladium-catalyzed Suzuki
reaction with the sulfonated b-ketoimines and b-diimines as sup-
porting ligands can not only be carried out in neat water but also
in mixed media such as H2O/CH3CN, H2O/C2H5OH, H2O/CH3COCH3
giving high yields (Table 4, entries 1–3, 8–9). Surprisingly, with
smaller amounts of catalyst (less than 0.05 mol%) the addition of
TBAB is not essential (Table 4, entries 5–6, 10–12). In these cases
the prolonged reaction times and/or raised reaction temperatures
are needed in order to increase the yields. Moreover, no palladium
black appeared as by-product. Under optimized conditions
(0.01 mol% catalyst/100 °C/without TBAB) the Suzuki reaction with
the supporting ligand 2c could be completed after 9 h with 95%
yield (Table 4, entry 7).
92
91c
99
13
Br
4-COMe
H
3
96c
99
14
15
Br
Br
2-CHO
2-CHO
4-Me
H
2
2
98
96c
96
16
17
Br
Br
3-NO2
3-NO2
H
4-Me
2
3
99
96c
90
18
19
20
21
22
23
24
Br
Br
Br
Br
Cl
Cl
Cl
4-C6H5
1-naphthalene
4-NH2
2-NH2
2-NO2
H
H
H
H
H
4-CH3
H
5
5
3
3
12
9
24
95
98
98
89d
90d
33d
4-NO2
H
a
Reaction conditions: 1.0 mmol bromobenzene, 1.5 mmol phenylboronic acid,
0.03 mol% PdCl2/complex 2c, 100 °C, 2 ml water, 1.5 mmol KOH.
b
Isolated yields, all reactions were monitored by GC, yields are average of two
runs.
c
0.03 mol% PdCl2/3a complex.
TBAB (0.1 equiv.) as the additive. 1.0 mol% complex was used.
d
With the optimized conditions, we screened a representative
range of aryl halides for the reaction (Scheme 5). The results are
summarized in Table 5.
As illustrated in Table 5, the palladium catalyst with the sulfo-
nated b-ketoimines and b-diimines ligands for the Suzuki reaction
proved exceptionally active. Regardless of phenyl halides and phe-
nyl boronic acids with the electron-donating or electron-withdraw-
PdCl2 / Ligand (1:1)
KOH, H2O
(OH) B
X
+
2
Y
Y
Z
Z
Scheme 5.

X. Guo et al. / Journal of Organometallic Chemistry 693 (2008) 3692–3696
3695
ing groups in different positions of the phenyl rings, these catalytic
systems always gave good to excellent yields of products. The cat-
alytic combinations tolerate a wide range of sensitive functional
groups, such as CHO, NO2, OMe, Me, NH2, Cl, and COMe in both sub-
strates. Even without TBAB addition the Suzuki reaction could be
catalyzed by less than 0.05 mol% catalyst without by-product or
palladium black. It is also worthy to be mentioned that the system
is effective for the coupling of un-activated aryl chlorides (Table 5,
entries 22–23), but more catalyst and a small amount of TBAB were
required to improve the yield. The coupling of chlorobenzene with
phenyl boronic acid gave moderate yield (Table 5, entry 24).
CH), 1.92 (s, 6H, CH3). MS (APCI-MS): m/z: 254.1 [MꢀNa]ꢀ. Elemen-
tal Anal. Calc. for C11H12NNaO4S (277.28 g/mol): C: 47.65; H: 4.36;
N: 5.05. Found: C: 47.48; H: 4.28; N: 5.10%.
4.3. Synthesis of the b-diimines (3a–d)
Synthesis of 3a: A mixture of sulfonated 2,6-diisopropyl aniline
(1a) (5.58 g, 20 mmol) and acetylacetone (1.05 g, 10.5 mmol) in
anhydrous methanol was stirred under reflux (40 ml). 0.82 ml of
concentrated HCl (10 mmol) was added dropwise. The reaction
was monitored by recording UV spectra. When the 343 nm peak
reached its maximum, the reaction was stopped. After cooling,
anhydrous ether was added dropwise until a small amount of
white solid had formed. Stirring was continued at room-tempera-
ture until precipitation was complete, filtration and evaporation
of the remaining solvent afforded 3a as a white solid (3.60 g,
59%). 1H NMR (300 MHz, D2O): d7.41 (s, 4H, Ar), 4.21 (s, 1H, CH),
2.65–2.58 (heptet, J = 6.6 Hz, 4H, CH), 2.56 (s, 6H, CH3), 0.94–0.92
(d, J = 6.6 Hz, 12H, CH3), 0.74–0.71 (d, J = 6.6 Hz, 12H, CH3). MS
(APCI-MS): m/z: 577.5 ([MꢀNa]ꢀ, 100%), 288.4 ([MꢀNaꢀH]/2,
42%). Elemental Anal. Calc. for C29H41N2Na2O6S2 (600.78 g/mol):
C: 57.98; H: 6.88; N: 4.66. Found: C: 57.92; H: 6.48; N: 4.65%.
Compound 3b, 3c, and 3d were obtained with the same method
as for 3a.
3. Conclusion
In conclusion, a series of water-soluble sulfonated b-ketoimine
and b-diimine ligands were synthesized and characterized. As sup-
porting ligands they can be used in the palladium-catalyzed Suzuki
reaction of phenyl bromide and phenyl boronic acid in the pres-
ence of TBAB in aqueous phase. This catalytic system tolerates a
wide range of substrates, including not only phenyl halides but
also phenyl boronic acids. These results provide environmentally
benign preparations of diaryl compounds. Further studies on the
reaction mechanism with this catalytic system and further applica-
tions are currently under investigation.
Compound 3b: 1H NMR (300 MHz, D2O): d7.28 (s, 4H, Ar), 4.133
(s, 1H, CH), 2.53 (s, 6H, CH3), 2.16 (q, J = 7.5 Hz, 8H, CH2), 0.82-0.77
(t, J = 7.5 Hz, 12H, CH3), MS (APCI-MS): m/z: 521.2 ([MꢀNa]ꢀ, 48%),
4. Experimental
260.1 ([MꢀNaꢀH]/2, 100%). Elemental Anal. Calc. for C25H33
-
4.1. Synthesis of sulfonated 2,6-dialkyl anilines (1a–d)
N2Na2O6S2 (544.67 g/mol): C: 55.13; H: 6.11; N: 5.14. Found: C:
55.26; H: 6.00; N: 5.50%.
Compound 3c: 1H NMR (300 MHz, D2O): d7.20 (s, 4H, Ar), 4.06 (s,
1H, CH), 2.52 (s, 6H, CH3), 1.79 (s, 12H, CH3), MS (APCI-MS): m/z:
465.0 ([MꢀNa]ꢀ, 25%), 232.1 ([MꢀNaꢀH]/2, 100%). Elemental Anal.
Calc. for C21H25N2Na2O6S2 (488.56 g/mol): C: 51.63; H: 5.16; N:
5.73. Found: C: 51.88; H: 5.19; N: 6.00%.
The sulfonated 2,6-dialkyl anilines (1a–d) were prepared
according to the literature [25,26].
4.2. Synthesis of the b-ketoimines (2a–d)
Compound 3d: 1H NMR (300 MHz, D2O): d7.74–7.71 (d, 2H,
J = 7,8Hz, Ar), 7.33–7.30 (d, 2H, J = 7.8, Ar), 5.52 (s, 1H, CH), 2.36
(s, 6H, CH3). MS (APCI-MS): m/z: 409.1 ([MꢀNa]ꢀ, 65%), 204.1
([MꢀNaꢀH]/2, 100%). Elemental Anal. Calc. for C17H17N2Na2O6S2
(432.45 g/mol): C: 47.22; H: 3.96; N: 6.48. Found: C: 47.38; H:
4.20; N: 6.59%.
Synthesis of 2a: A mixture of sulfonated 2,6-diisopropyl aniline
(1a) (5.58 g, 20 mmol) and acetylacetone (2.20 g, 22 mmol) in
refluxing anhydrous methanol (40 ml) was kept stirring, and
0.3 ml of formic acid was added to the reaction solution. Ultraviolet
spectra were recorded to monitor the reaction process. When the
317 nm peak reached its maximum, the reaction was stopped.
After cooling, anhydrous ether was added dropwise to the reaction
solution until a white solid appeared. Stirring was continued at
room-temperature until a large amount of white solid had formed.
Filtration and evaporation of the solvent afforded 2a as a white so-
lid (6.50 g, 90%). 1H NMR (300 MHz, D2O): d 7.58 (s, 2H, Ar), 5.30 (s,
1H, CH), 2.79–2.93 (heptet, J = 6.9, 2H, CH), 1.96 (s, 3H, CH3), 1.54
(s, 3H, CH3), 1.11–1.13 (d, J = 6.9, 6H, CH3), 0.99–1.01 (d, J = 6.9,
6H, CH3). MS (APCI-MS): m/z: 338.4 [MꢀNa]ꢀ. Elemental Anal.
Calc. for C17H24NNaO4S (361.44 g/mol): C: 56.49%; H: 6.69%; N:
3.88%. Found: C: 56.36; H: 6.60; N: 3.91%.
4.4. General procedure for the Suzuki coupling reaction
Under nitrogen, a round bottom flask equipped with a reflux
condenser, was charged with bromobenzene (0.157 g, 1 mmol),
phenyl boronic acid (0.183 g, 1 mmol), KOH (0.0842 g, 1.5 mmol),
a stock solution of 2 c/PdCl2 complex in water (0.001 M, 1 ml),
and 1 ml water. The mixture was stirred in a preheated 100 °C
oil bath for 3 h, and then allowed to cool to room-temperature.
After the addition of water (8 ml) and extraction with ether
(3 ꢁ 10 ml), the organic phase was dried over MgSO4, filtered,
passed over silica gel by flash chromatography and analyzed by
GC and GC-MS. All products were characterized by NMR [35].
Compounds 2b, 2c, and 2d were obtained with the same meth-
od as for 2a.
Compound 2b: 1H NMR (300 MHz, D2O): d 7.49 (s, 2H, Ar), 5.29
(s, 1H, CH), 2.46–2.38 (q, J = 7.2 Hz, 4H, CH3), 2.12 (s, 3H, CH3), 1.54
(s, 3H, CH3), 1.10–0.98 (t, J = 7.2 Hz, 6H, CH3). MS (APCI-MS): m/z:
310.3 [MꢀNa]ꢀ. Elemental Anal. Calc. for C15H20NNaO4S (333.38 g/
mol): C: 54.04; H: 6.05; N: 4.20. Found: C: 53.98%; H: 5.99%; N:
4.10%.
Acknowledgements
This work was supported by NSFC No. 20372042 and the Sci-
ence Foundation of Shandong Y2006B18.
Compound 2c: 1H NMR (300 MHz, D2O): d7.50 (s, 2H, Ar), 5.34 (s,
1H, CH), 2.13 (s, 6H, CH3), 1.99 (s, 3H, CH3), 1.16 (s, 3H, CH3). MS
(APCI-MS): m/z: 282.1 [MꢀNa]ꢀ. Elemental Anal. Calc. for
C13H16NNaO4S (305.33 g/mol): C: 51.14; H: 5.28; N: 4.59. Found:
C: 51.32; H: 5.28; N: 4.75%.
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[35] (1) Biphenyl d 7.59–7.57 (m, 4H), 7.44–7.40 (m, 4H), 7.35–7.30 (m, 2H). (2) 4-
Methylbiphenyl d 7.54 (d, J = 8.1 Hz, 2H), 7.45 (d, J = 8.1 Hz, 2H), 7.37 (t,
J = 7.8 Hz, 2H), 7.27 (t, J = 8.4 Hz, 1H), 7.19 (d, J = 7.8 Hz, 2H), 2.34 (s, 3H). (3) 4-
Methoxybiphenyl d 7.57–7.52 (m, 4H), 7.42 (t, J = 7.2 Hz, 2H), 7.30 (t, J = 7.2 Hz,
1H), 6.98 (d, J = 9.0 Hz, 2H), 3.85 (s, 3H). (4) 2-Methylbiphenyl d 7.43–7.35 (m,
2H), 7.34–7.27 (m, 3H), 7.26–7.18 (m, 4H), 2.27 (s, 3H). (5) 4-Acetylbiphenyl d
8.04 (d, J = 8.4 Hz, 2H), 7.67 (d, J = 8.7 Hz, 2H), 7.62 (d, J = 8.7 Hz, 2H), 7.55–
7.30 (m, 3H), 2.64 (s, 3H). (6) 4-Chlorobiphenyl d 7.68–7.33 (m 9H). (7) 2-
biphenylcarbaldehyde d 9.98 (s, 1H), 8.03 (d, J = 7.80 Hz, 1H), 7.67–7.61 (m,
1H), 7.52–7.36 (m, 7H). (8) 3-Nitrobiphenyl d 8.43 (s, 1H), 8.18 (d, J = 8.10 Hz,
1H), 7.90 (d, J = 7.80 Hz, 1H), 7.62–7.56 (m, 3H), 7.51–7.39 (m, 3H). (9) p-
Terphenyl d 7.68–7.55 (m, 8H), 7.48–7.44 (m, 4H), 7.38–7.33 (m, 2H). (10) 4-
Aminobiphenyl d 7.52 (d, J = 7.2 Hz, 2H), 7.48–7.35 (m, 4H), 7.25 (t, J = 7.2 Hz,
1H), 6.71 (d, J = 8.7 Hz, 2H), 3.66 (s, 2H). (11) 4, 40-Dimethoxybiphenyl d 7.47
(d, J = 9.0 Hz, 4H), 6.95 (d, J = 9.0 Hz, 4H), 3.83 (s, 6H). (12) 4-Methoxy-40-
methylbiphenyl d 7.50 (d, J = 8.7 Hz, 2H), 7.45 (d, J = 7.8 Hz, 2H), 7.22 (d,
J = 7.8 Hz, 2H), 6.96 (d, J = 8.7 Hz, 2H), 3.83 (s, 3H), 2.38 (s, 3H). (13) 4-
Methylbiphenyl-20-carbaldehyde d 9.98 (s, 1H), 8.00 (d, J = 7.8 Hz, 1H), 7.60 (t,
J = 7.5 Hz, 1H), 7.44(s, J = 7.8 Hz, 1H), 7.41 (d, J = 7.5 Hz, 1H), 7.25 (s, 4H), 2.41
(s, 3H). (14) 4-Chloro-40-methoxybiphenyl d 7.51–7.46 (m, 4H), 7.39 (d, J = 8.7
Hz, 2H), 6.98 (d, J = 8.7 Hz, 2H), 3.86 (s, 3H). (15) 4-Nitro-4-methylbiphenyl d
8.25 (d, J = 8.7 Hz, 2H), 7.72 (d, J = 8.7 Hz, 2H), 7.53 (d, J = 8.1 Hz, 2H), 7.30 (d,
J = 8.1 Hz, 2H), 2.42 (s, 3H). (16) 2-Aminobiphenyl d 7.42–7.38 (m, 4H), 7.36–
7.28 (m, 1H), 7.12 (t, J = 7.8 Hz, 2H), 6.80 (t, J = 7.8 Hz, 1H), 6.72 (d, J = 7.8 Hz,
1H), 3.58 (s, 2H). (17) 2-Nitro-4’-methylbiphenyl d 8.43 (s, 1H), 8.16 (d,
J = 8.4 Hz, 1H), 7.89 (d, J = 7.8 Hz, 1H), 7.58 (t, J = 7.8 Hz, 1H), 7.52 (d, J = 8.4 Hz,
2H), 7.30 (d, J = 7.8 Hz, 2H), 2.42 (s, 3H). (18) 4-Methyl-40-methylbiphenyl d
7.45 (d, J = 7.8 Hz, 4H), 7.20 (d, J = 7.8 Hz, 4H). (19) 4-Chloro-40-
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methylbiphenyl
d 7.50–7.42 (m, 4H), 7.37 (d, J = 8.4 Hz, 2H), 7.24 (d,
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J = 8.4 Hz, 2H). (20) 1-phenylnaphthalene d 7.81–7.71 (m, 3H), 7.41–7.29 (m,
9H).
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