Dimerization of Aromatic Compounds Using Palladium-Carbon-Catalyzed Suzuki-Miyaura Cross-Coupling by One-Pot Synthesis

Article abstract of DOI:10.1055/s-0036-1591892

The aromatic dimers play a significant role in many aspects. Herein, we report a simple palladium-carbon catalyst that is highly effective for the dimerization of brominated aromatic compounds under mild conditions using abundant brominated aromatic compounds, bis(pinacolate)diboron and potassium acetate by a 'one-pot' method. This process, which we believe proceeds via a Suzuki-Miyaura cross-coupling reaction mechanism, allows access to a variety of aromatic compounds under mild reaction conditions and has a good functional group tolerance with moderate to high yields.

Full text of DOI:10.1055/s-0036-1591892

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F. Du et al.
Letter
Dimerization of Aromatic Compounds Using Palladium-Carbon-
Catalyzed Suzuki–Miyaura Cross-Coupling by One-Pot Synthesis
Fangyu Du
Qifan Zhou
Dongdong Liu
Ting Fang
Pd-C (0.01 equiv)
B2Pin2 (1.5 equiv)
KOAc (3 equiv)
X
R
Br
R
X
EtOH, 60 °C
X
R
Yajie Shi
R = alkyl, phenyl, amino,
hydroxy, methoxy, halogen
X = CH, N
Yang Du
16 examples, yields 7.4%–98.8%
Guoliang Chen*
Key Laboratory of Structure-Based Drug Design & Discovery of
Ministry of Education, Shenyang Pharmaceutical University,
Shenyang 110016, P. R. of China
spucgl@163.com
Received: 04.11.2017
Accepted after revision: 18.12.2017
Published online: 31.01.2018
The main features of aromatic compounds are as fol-
lows: solid molecular structure, high electron density, and
symmetry,1
0,11
which have important effect on the poly-
DOI: 10.1055/s-0036-1591892; Art ID: st-2017-w0813-l
meric materials. Therefore, aromatic polymer materials are
widely used in engineering plastics, polymeric membranes,
etc.
Abstract The aromatic dimers play a significant role in many aspects.
Herein, we report a simple palladium-carbon catalyst that is highly ef-
fective for the dimerization of brominated aromatic compounds under
mild conditions using abundant brominated aromatic compounds,
bis(pinacolate)diboron and potassium acetate by a ‘one-pot’ method.
This process, which we believe proceeds via a Suzuki–Miyaura cross-
coupling reaction mechanism, allows access to a variety of aromatic
compounds under mild reaction conditions and has a good functional
group tolerance with moderate to high yields.
As the aromatic polymers have become more and more
functional, the research on their synthetic methods has at-
tracted scientists’ attention. The C–C bond-formation reac-
12
13
tions involving name reactions include the Suzuki, Heck,
and Sonogashira14 cross-coupling reaction, etc. Certainly,
the synthetic methods of biphenyl derivatives are mainly as
follows:1
5–18
the substituted halobenzene coupled with sub-
Key words Self-coupling, Suzuki–Miyaura cross-coupling, palladium-
carbon, catalysis, dimerization
stituted phenyl boronic acid catalyzed by palladium cata-
lysts with different ligands or supports such as Pd(dba)2,
Aromatic dimers are ubiquitous reagents in organic syn-
thesis and play a significant role in many aspects, such as
pharmaceutical and chemical industries. The antimicrobial
agent, magnolol (Figure 1), extracted from Magnolia offici-
[1,1′-bis(diphenylphosphino)ferrocene]
um(II), palladium chloride, etc.
dichloropalladi-
The byproducts of the Suzuki–Miyaura cross-coupling
have been reported,19 but no general method was proposed.
Here, we disclose the development of conditions for the di-
merization of substituted brominated aromatic compounds
using the cheap and readily available catalyst of palladium-
carbon. These reactions occur at mild temperature (60 °C),
employ substituted brominated aromatic compounds and
inexpensive catalysts, and afford high yields. These reac-
tions likely proceed via a Suzuki–Miyaura coupling reaction
pathway. Importantly, this process is general with respect
to both the substituents and aromatic ring type. This wide
scope allows the preparation of many substituted aromatic
dimers. To our delight, some substituted brominated aro-
matic compounds showed a good functional group toler-
ance with moderate to high yields, and some coupling re-
sults can be preliminarily summarized which were advan-
tageous for the preparation of self-coupling compounds.
1–3
nalis is a typical aromatic dimer.
In recent years, some
theoretical studies have confirmed that dimers or oligo-
mers are the main features of G-protein-coupled receptors,
4–6
Chung and his coworkers7
such as the opioid receptor.
discovered that biphenyl-type neolignan derivatives from
the twigs of Magnolia denudate have anti-inflammatory ac-
tivity. The dimers of small molecules have been used in the
8,9
development of new drugs.
HO
OH
magnolol
Figure 1 The structure of magnolol
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F. Du et al.
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The experimental procedures were conducted according
isolated in 98.7% yield. The reaction enjoys wide substrate
scope with respect to substituted brominated aromatic
compounds (Table 2).
20
to a literature report with some modifications which
were conducive to the formation of coupling products (Ta-
ble 1). At first, we examined the reaction of bromobenzene
in acetonitrile. Under basic conditions in the presence of a
catalyst, only a small amount of the desired product biben-
zene (3a) was obtained (Table 1, entry 1)
Attempts to optimize the molar ratio of bibenzene with
bis(pinacolate)diboron were successful. This led to more
promising results when the ratio increased to 1.5 (Table 1,
entries 1–4). The reaction temperature was also an import-
ant factor and the coupling reaction cannot be carried out
at room temperature (Table 1, entry 5). Different solvents
including acetonitrile, dimethylsulfoxide, and ethanol were
tested and a protic solvent was favored, with ethanol being
the most effective in the screening reaction (Table 1, entries
A range of functional groups on the substituted bromo-
benzene proved to be compatible, including phenyl, alkyl,
methoxy, hydroxyl, and amino (1b–j, Table 2, entries 2–10).
The ability of substituted bromobenzene to participate in
the reaction opens the possibility for dimerization of het-
eroaromatic compounds. Bromopyridine and substituted
bromopyridine can also be used in the reaction (1k,l, Table
2, entries 11 and 12). The use of brominated aromatic com-
pounds bearing groups at different positions gave different
yields. Brominated aromatic compounds substituted in the
para position were prone to produce desired products of
self-coupling. Moreover, brominated aromatic compounds
substituted in the para position produced the desired prod-
ucts more easily than compounds substituted in the meta
position. When the substituents were in the meta position,
the coupling reaction was not prone to occur, and resulted
in a 7.4% yield of 1j (Table 2, entry 10). Nevertheless, when
the substituent was a carboxyl group, the coupling prod-
ucts could not be observed and debromination occurred,
such as 1o,p (Table 2, entries 15 and 16). Surprisingly, the
yields of debromination were above 90%. On the contrary,
after the esterification of carboxyl groups, the desired self-
coupling product was obtained (1m, Table 2, entry 13). A
plausible explanation for this difference was the kinetic
competition between the hydrogen source and the borate
6
–8). Attempts to optimize the reaction through modifica-
tion of the base proved unsuccessful, and the kind of bases
had an important effect on the reaction, with potassium ac-
etate proving to be optimal in terms of yield and ease of
use. We replaced palladium-carbon with a palladium cata-
lyst with different ligands which led to different results.
With the use of PdCl (dppf) and Pd(PPh ) , the desired self-
2
3 4
coupling products were not observed and the main prod-
ucts were benzene borates (Table 1, entries 12 and 13). Un-
der these optimized conditions, the desired bibenzene was
Table 1 Identification of the Reaction Conditions
catalyst (0.01 equiv)
base (3 equiv)
Br
O
O
O
O
+
B
B
solvent, 60 °C,
argon, 6 h
1a
2
3a
Entry
Molar Ratio (1a:2) Solvent
Base
Catalyst
Temp (℃)
Yield (%)a
1
1:0.1
1:0.5
1:1
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
EtOH
DMSO
EtOH
EtOH
EtOH
EtOH
EtOH
MeCOOK
MeCOOK
MeCOOK
MeCOOK
MeCOOK
MeCOOK
MeCOOK
MeCOOK
Pd-C
Pd-C
Pd-C
Pd-C
Pd-C
Pd-C
Pd-C
Pd-C
Pd-C
Pd-C
Pd-C
60
60
60
60
ATb
80
60
60
60
60
60
60
60
9.2
2
20.3
56.8
87.2
–
3
4
1:1.5
1:1.5
1:1.5
1:1.5
1:1.5
1:1.5
1:1.5
1:1.5
1:1.5
1:1.5
5b
6c
7
86.0
98.7
45.6
60.3
70.0
71.7
–
8
9
Et
Na
NaHCO
3
N
1
1
1
0
2
CO
3
1
3
2c
3c
MeCOOK
MeCOOK
PdCl
Pd(PPh
2
(dppf)
1
3
)
4
–
a
Isolated yield with column chromatography.
AT = ambient temperature.
b
c
Almost no reactions were observed by TLC.
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F. Du et al.
Letter
ester undergoing transmetalation. The proton was not con-
ducive to the formation of boronate ester intermediates, re-
sulting in debromination. Additionally, the coupling activi-
ty of bromobenzyl (1n, Table 2, entry 14) was also very high
and afforded 1,2-diphenylethane in 78% yield. The forma-
tion of benzylboronic acid pinacol ester (3q, Figure 2)
proved that bromobenzyl underwent the same mechanism
leading to 1,2-diphenylethane.
Table 2 Scope with Respect to Substituted Aromatic Compounds
Pd-C (0.01 equiv)
potassium acetate (3 equiv)
Ar-Ar a
O
O
O
O
Ar Br
+
B
B
EtOH, argon, 60 °C
1
2
3
Entry
1
Substrate
Products
Time (h)
6
Yield (%)b
98.7
Br
3a
1a
Br
2
3
12
5
98.1
30.3
3b
1b
Br
1c
3c
4
8
50.0
Br
1d
3d
O
O
O
Br
5
6
3
3
66.7
87.7
1e
O
3e
O
Br
O
1f
3f
OH
Br
7
OH
12
75.5
HO
1g
3g
HO
Br
HO
OH
8
9
12
8
90.0
94.3
1h
3h
H2N
Br
H2N
NH2
1i
3i
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F. Du et al.
Letter
Table 2 (continued)
Entry
Substrate
Products
Time (h)
8
Yield (%)b
7.4
H2N
H2N
Br
10
11
1
j
3
j
NH2
N
F
Br
F
F
N
N
18
98.2
1k
3k
N
Br
12
13
14
N
12
8
41.8
48.4
78.0
N
1
l
3l
MeOOC
Br
MeOOC
COOMe
1
m
3m
Br
3
1n
3n
COOH
COOH
1
5c
6
7
98.8
93.3
Br
Br
1
o
3o
COOH
COOH
1
6c
1p
3p
a
Unless otherwise noted, the product was dimeric.
Isolated yield with column chromatography.
b
c
The self-coupling target products were not observed and debromination occurred.
O
B
complex. Then the intermediate coupled with another mol-
ecule of the aryl-palladium(II)–bromine complex resulting
in the aromatic dimer.
O
3
q
Figure 2 The intermediate of benzylboronic acid pinacol ester
In summary, we have developed a catalytic system for
the dimerization of brominated aromatic compounds that
utilizes readily available brominated aromatic compounds
and related heteroaromatic compounds. This protocol pro-
poses an inexpensive catalyst of palladium-carbon in C–C
bond construction and provides some examples of di-
merization of brominated aromatic compounds using read-
ily available starting materials under mild reaction condi-
tions. This reaction allows the conversion of simple starting
materials into complex aromatic compounds, which are im-
portant synthetic intermediates in organic synthesis. The
key to this discovery was the identification of a cheap cata-
lyst of palladium-carbon that can be used to synthesize the
aromatic dimer compounds by a ‘one-pot’ method. To our
delight, some substituted brominated aromatic compounds
The mechanism of the self-coupling is analogous to the
catalytic cycle for the other cross-coupling reactions and
has four distinct steps: 1) oxidative addition of an organic
halide to the Pd(0) species to form Pd(II); 2) exchange of the
anion attached to the palladium for the anion of the base
12
(metathesis); 3) transmetalation between Pd(II) and the al-
kylborate complex; and 4) reductive elimination to form
the C–C σ bond and regeneration of Pd(0). Certainly, the
brominated aromatic compounds reacted with bis(pinaco-
late)diboron which underwent two cycles resulting in self-
coupling products (Scheme 1). The main processes are as
follows: a molecule of brominated aromatic compound cou-
pled with bis(pinacolate)diboron and formed an arylborate
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F. Du et al.
Letter
(
(
(
7) Chung, C. Y.; Kuo, W. L.; Hwang, T. L.; Chung, M. I.; Chen, J. J.
Chem. Biodiversity 2015, 12, 1263.
8) Si, T.; Li, B.; Xiong, W.; Xu, B.; Tang, W. Org. Biomol. Chem. 2017,
Ar-Ar
Ar-Br
Pd(0)
1
5, 9903.
9) Goto, H.; Katagiri, H.; Furusho, Y.; Yashima, E. J. Am. Chem. Soc.
006, 128, 7176.
10) Yuan, X.; Wu, L.; Zong, Z.; Wei, X. Modern Chemical Industry
999, 19, 12.
Ar-Pd(II)-Ar
O
Ar-Pd(II)-Br
2
(
1
O
O
(11) Dong, R.; Sun, X. B.; Li, Y. B.; Zhang, J. X. Modern Chemical Indus-
try 2012, 32, 22.
(12) Miyaura, N.; Suzuki, A. Chem. Informationsdienst 1979, 19, 135.
(13) Heck, R. F. J. Am. Chem. Soc. 1968, 90, 5518.
Ar
B
Br
B
O
Ar-Br
Pd(0)
(
(
(
14) Cassar, L. J. Organomet. Chem. 1975, 93, 253.
15) Ilie, A.; Roiban, G. D.; Reetz, M. T. ChemistrySelect 2017, 2, 1392.
16) Fyfe, J. W.; Fazakerley, N. J.; Watson, A. J. Synfacts 2017, 56,
O
Ar-Pd(II)
OAc
B
Ar-Pd(II)-Br
1249.
O
O
O
(
17) Mondal, M.; Begum, T.; Gogoi, P. K.; Bora, U. ChemistrySelect
2016, 1, 4645.
B
AcO–
Ar-Pd(II)-OAc
(18) Sarvestani, M.; Azadi, R. Appl. Organomet. Chem. 2016, 31,
e3667.
O
B
O
(
19) Ishiyama, T.; Murata, M.; Miyaura, N. J. Org. Chem. 1995, 60,
B
O
O
7508.
(
(
20) Molander, G. A.; Dehmel, F. J. Am. Chem. Soc. 2004, 35, 10313.
21) (a) Ceylan, M.; Fındık, E.; Seçen, H. Helv. Chim. Acta 2010, 91,
Scheme 1 The mechanism of the catalytic cycle
559. (b) Ito, R.; Migita, T.; Morikawa, N.; Okuni, M.; Simamura,
O. Bull. Chem. Soc. Jpn. 2006, 36, 985. (c) Bamfield, P.; Quan, P.
M. Synthesis 1978, 537. (d) Kern, W.; Ebersbach, H. W.; Ziegler, I.
Makromol. Chem. 1959, 31, 154. (e) Berezin, A. A.; Koutentis, P.
A. Tetrahedron 2011, 67, 4069. (f) James, J. GB 857153, 1960.
showed a good functional group tolerance with moderate
to high yields. However, reactions with some special sub-
strates such as aromatic carboxylic acids did not produce
the target products of self-coupling, but resulted in debro-
mination in very high yields. Efforts to apply our palladium-
carbon system to other catalytic dimerization reactions and
to expand the scope of the dimerization of aromatic com-
pounds to other classes of aromatic compounds are cur-
rently under way in our laboratory.
(g) Filippi, S.; Madrigali, L.; Polacco, G.; Magagnini, P.; La Mantia,
F. P.; Acierno, D. Polym. Eng. Sci. 2010, 46, 139. (h) Shingte, R. D.;
Rege, A. V.; Pishavikar, D. G.; Shah, S. V. J. Univ. Bombay, Sci.
1951, 20, 89. (i) Reuter, R.; Wegner, H. A. Chemistry 2011, 17,
2987. (j) Lee, K.; Lee, P. H. Tetrahedron Lett. 2008, 49, 4302.
(k) Zeng, M.; Du, Y.; Shao, L.; Qi, C.; Zhang, X. M. J. Org. Chem.
2010, 75, 2556. (l) Ogata, Y.; Hojo, M.; Morikawa, M.; Maekawa,
J. J. Org. Chem. 1962, 27, 3373. (m) Metallinos, C.; Zaifman, J.;
Belle, L. V.; Dodge, L.; Pilkington, M. Organometallics 2009, 28,
4
534. (n) Kajigaeshi, S.; Nakagawa, T.; Nagasaki, N.; Fujisaki, S.
Synthesis 1985, 674. (o) Somogyi, L. J. Heterocycl. Chem. 2010,
4, 1235.
Funding Information
4
Financial support from the Natural Science Foundation of Liaoning
Province (201602707) and the Discipline Construction Program of
Shenyang Pharmaceutical University (52134606) is gratefully ac-
(
22) General Procedure
To a solution of brominated aromatic compounds (1 equiv),
bis(pinacolate)diboron (1.5 equiv), and anhydrous ethanol (15
mL) was added palladium-carbon (0.01 equiv), followed by
potassium acetate (3 equiv) under argon. The mixture was
heated to 60 °C with stirring for the indicated time. The reactor
was cooled to room temperature, and the reaction mixture was
filtered, and the filtrate was concentrated under reduced pres-
sure. The residue was extracted with dichloromethane (3 × 20
mL), and the organic layer was washed with water (2 × 20 mL)
and once with brine (25 mL), dried over magnesium sulfate and
concentrated in vacuo. The product was purified by flash
column chromatography on silica gel using petroleum ether as
eluent.
knowledged.
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Supporting Information
Supporting information for this article is available online at
https://doi.org/10.1055/s-0036-1591892.
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References and Notes
(1) Runeberg, J.; Faurholt, C.; Stenhagen, E.; Sillén, L. G.; Zaar, B.;
Diczfalusy, E. Acta Chem. Scand. 1958, 12, 188.
2) Agharahimi, M. R.; Lebel, N. A. J. Org. Chem. 1995, 60, 1856.
3) Anrong, L. CN 1270168, 2000.
4) Reggio, P. H. AAPS J. 2006, 8, E322.
5) Huang, J.; Chen, S.; Zhang, J. J.; Huang, X. Y. Nat. Struct. Mol. Biol.
Biphenyl (3a)
21a
(
(
(
(
Yield 0.97 g, 98.7%; pale solid; mp 69–71 °C (lit. mp 69–71
1
℃); R = 0.23 (PE). H NMR (400 MHz, CDCl ): δ = 7.60 (t, J = 1.24
f
3
Hz, 2 H), 7.44 (t, J = 7.20 Hz, 2 H), 7.34 (t, J = 7.36 Hz, 1 H). 13
C
NMR (150 MHz, CDCl ): δ = 141.2, 128.7, 127.2, 127.1. GC–MS:
3
2013, 20, 419.
m/z = 154.2.
(
6) Zhang, J.; Ferguson, S. S.; Barak, L. S.; Bodduluri, S. R.; Laporte, S.
4,4′-Dimethyl-1,1′-biphenyl (3b)
Yield 0.52 g, 98.1%; white solid; mp 125 ℃ (lit. mp 125 ℃);
21b
A.; Law, P. Y.; Caron, M. G. Hebei Med. 2005, 95, 7157.
©
Georg Thieme Verlag Stuttgart · New York — Synlett 2018, 29, A–F

F
Synlett
F. Du et al.
Letter
1
R = 0.50 (PE). H NMR (600 MHz, CDCl ): δ = 7.45 (d, J = 7.68 Hz,
2
NMR (150 MHz, DMSO-d ): δ = 146.2, 128.0, 125.4, 113.7. ESI-
MS: m/z [M + H] = 185.1.
f
3
6
13
+
H), 7.24 (d, J = 8.22 Hz, 2 H), 2.38 (s, 6 H). C NMR (150 MHz,
CDCl ): δ = 138.3, 136.7, 129.4, 126.8, 21.1. GC–MS: m/z = 182.2.
3,3′-Diaminobiphenyl (3j)
3
2
1i
Benzerythrene (3c)
Yield 0.20 g, 30.3%; white solid; mp > 300 ℃ (lit. mp 315–318
Yield (40 mg, 7.4%); brown solid; mp 89–90 °C (lit. mp 93 ℃);
2
1c
1
R = 0.26 (EtOAc/PE = 1:5). H NMR (400 MHz, CDCl ): δ = 7.22–
f
3
1
°
C); R = 0.57 (EtOAc/PE = 1:10). H NMR (400 MHz, CDCl ): δ =
7.16 (q, J = 8.32 Hz, J = 16.08 Hz, 2 H), 6.95 (d, J = 7.64 Hz, 2 H),
f
3
1
2
13
13
7
1
5
.77–7.37 (m, 18 H). C NMR (150 MHz, CDCl ): δ = 140.7,
6.84 (s, 2 H), 6.64–6.62 (q, J1 = 1.44 Hz, J2 = 7.88 Hz, 2 H).
C
3
40.3, 139.6, 128.8, 127.6, 127.5, 127.1. GC–MS: m/z = 306.2.
,5,5′,5′,8,8,8′,8′-Octamethyl-5,5′,6,6′,7,7′,8,8′-octahydro-2,2′-
NMR (150 MHz, DMSO-d ): δ = 135.5, 133.7, 131.5, 115.4, 115.3,
6
+
112.7. ESI-MS: m/z [M+H] = 185.1.
binaphthalene (3d)
Yield 0.35 g, 50.0%; colorless oily liquid; R = 0.41 (PE). H NMR
5,5′-Difluoro-2,2′-bipyridine (3k)
Yield 0.54 g, 98.2%; off-white solid; mp 153–154 °C (lit. mp
1
21j
f
1
(
400 MHz, CDCl ): δ = 7.49 (s, 2 H), 7.48–7.32 (m, 4 H), 1.73 (s, 8
153–154 ℃); R = 0.87 (EtOAc/PE = 1:5). H NMR (600 MHz,
3
f
13
H), 1.35 (d, J = 5.08 Hz, 24 H). C NMR (150 MHz, CDCl ): δ =
CDCl ): δ = 8.50 (d, J = 2.34 Hz, 2 H), 8.39 (dd, J = 4.38 Hz, J =
3
3
1
2
1
3
1
3
3
44.9, 143.5, 138.9, 126.7, 125.3, 124.5, 35.2, 35.1, 34.3, 34.1,
1.9, 31.8. GC–MS: m/z = 374.3.
8.76 Hz, 2 H), 7.54–7.51 (m, 2 H). C NMR (150 MHz, CDCl ): δ
3
= 160.7, 159.0, 151.4, 151.42, 137.3, 137.1, 123.9, 123.8, 122.3,
122.2. GC-MS: m/z = 192.2.
2,2′-Bipyridine (3l)
,3′-Dimethoxy-1,1′-biphenyl (3e)
21d
Yield 0.38 g, 66.7%; colorless oily liquid (lit.
mp 36 ℃); R =
f
1
21k
0
7
6
1
2
2
.57 (EtOAc/PE = 1:5). H NMR (600 MHz, CDCl ): δ = 7.32 (t, J =
.86 Hz, 2 H), 7.17–7.15 (m, 2 H), 7.11 (t, J = 2.22 Hz, 2 H), 6.88–
.86 (m, 2 H), 3.81 (s, 6 H). C NMR (150 MHz, CDCl ): δ =
59.9, 142.6, 129.7, 119.7, 112.9, 112.8, 55.2. GC–MS: m/z =
Yield 0.41 g, 41.8%; white solid; mp 72 °C (lit. mp 71–72 ℃);
3
1
Rf = 0.27 (EtOAc/PE = 1:5). H NMR (600 MHz, CDCl ): δ = 8.71
3
13
(d, J = 4.26 Hz, 2 H), 8.44 (d, J = 7.86 Hz, 2 H), 7.85 (t, J = 7.62 Hz,
3
13
2 H), 7.34 (t, J = 5.4 Hz, 2 H). C NMR (150 MHz, CDCl ): δ =
3
+
14.2.
156.0, 149.1, 137.1, 123.8, 121.2. ESI-MS: m/z [M + H] = 157.1.
4,4′-Bis(methoxycarbonyl)biphenyl (3m)
,2′-Dimethoxy-1,1′-biphenyl (3f)
21e
21l
Yield 0.50 g, 87.7%; white solid; mp 154–155 °C (lit. mp154–
Yield 0.30 g, 48.4%); white solid; mp 224 °C (lit. mp 224 ℃); Rf
1
1
1
=
=
1
55 ℃); R = 0.60 (EtOAc/PE = 1:3). H NMR (400 MHz, CDCl ): δ
= 0.56 (EtOAc/PE = 1:5). H NMR (400 MHz, CDCl ): δ = 8.15 (d, J
f
3
3
7.35–7.31 (m, 2 H), 7.26–7.02 (m, 2 H), 7.00 (q, J = 7.44 Hz, J
= 8.36 Hz, 4 H), 7.72 (q, J = 8.40 Hz, J = 1.60 Hz, 4 H), 3.97 (s, 6
1
2
1
2
13
13
6.60 Hz, 4 H), 3.77 (s, 6 H). C NMR (150 MHz, CDCl ): δ =
H). C NMR (150 MHz, DMSO-d ): δ = 167.4, 143.7, 130.4,
3
6
57.0, 131.4, 128.6, 127.8, 120.3, 111.1, 55.7. ESI-MS: m/z [M +
129.1, 127.8, 52.7. GC–MS: m/z = 270.2.
1,2-Diphenylethane (3n)
+
H] = 215.1.
2
1m
2
,2′-Biphenol (3g)
Yield 0.83 g, 78.0%; white solid; mp 48–50 °C (lit.
mp 48–50
21f
1
Yield 0.41 g, 75.5%; colorless oily liquid (lit. mp 50 °C); R =
℃); R = 0.37 (EtOAc/PE = 1:5). H NMR (400 MHz, CDCl ): δ =
f
f
3
1
13
0.35 (EtOAc/PE = 1:3). H NMR (400 MHz, CDCl ): δ = 7.38–7.33
7.28 (m, 5 H), 7.20 (m, 5 H), 2.92 (s, 4 H). C NMR (150 MHz,
3
(
m, 2 H), 7.30 (d, J = 1.36 Hz, 1 H), 7.10–7.05 (q, J = 1.00 Hz, J =
CDCl ): δ = 141.8, 128.4, 128.3, 125.9, 37.9. GC–MS: m/z = 182.2.
1
2
3
13
8
1
1
4
.64 Hz, 4 H), 5.40 (br, 2 H). C NMR (150 MHz, CDCl ): δ =
2-Naphthoic Acid (3o)
Yield 0.68 g, 98.8%; white solid; mp 174–180 °C (lit. mp 180–
3
+
21n
52.0, 130.6, 129.2, 122.9, 120.9, 115.9. ESI-MS: m/z [M + H] =
1
84.9.
183 ℃); R = 0.57 (EtOAc/PE/AcOH = 1:3:0.2). H NMR (600 MHz,
f
,4′-Biphenol (3h)
CDCl ): δ = 8.74 (s, 1 H), 8.15 (d, J = 8.52 Hz, 1 H), 8.02 (d, J = 8.16
3
21g
13
Yield 0.86 g, 90.0%; white solid; mp 283 ℃ (lit. mp 282–284
℃
Hz, 1 H), 7.93 (t, J = 9.18 Hz, 2 H), 7.66–7.58 (m, 2 H). C NMR
1
); R = 0.50 (EtOAc/PE = 1:2). H NMR (400 MHz, DMSO-d ): δ =
(150 MHz, CDCl ): δ = 171.9, 136.0, 132.4, 132.2, 129.6, 128.7,
f
6
3
–
9
.38 (s, 2 H), 7.37 (d, J = 8.52 Hz, 4 H), 6.79 (d, J = 8.52 Hz, 4 H).
128.4, 127.8, 126.8, 126.4, 125.4. ESI-MS: m/z [M – H] = 170.9.
1
3
C NMR (150 MHz, DMSO-d ): δ = 155.7, 130.5, 126.3, 115.0.
Benzoic Acid (3p)
Yield 0.47 g, 93.3%; white solid; mp 120–121 °C (lit. mp 119–
6
+
21o
ESI-MS: m/z [M + H] = 184.9.
4
Yield 0.50 g, 94.3%; brown solid; mp 117–119 °C (lit. mp 80
℃
1
,4′-Bianiline (3i)
121 ℃); R = 0.60 (EtOAc/PE = 1:5). H NMR (600 MHz, CDCl ): δ
f
3
21h
= 8.13 (dd, J1 = 1.02 Hz, J2 = 8.10 Hz, 2 H), 7.63–7.61 (m, 1 H),
1
13
); R = 0.15 (EtOAc/PE = 1:3). H NMR (400 MHz, CDCl ): δ =
7.49 (t, J = 7.68 Hz, 2 H). C NMR (150 MHz, CDCl ): δ = 172.4,
f
3
3
13
–
7
.35 (d, J = 7.8 Hz, 4 H), 6.74 (d, J = 7.8 Hz, 4 H), 3.67 (s, 4 H).
C
133.8, 130.2, 129.3, 128.5. ESI-MS: m/z [M – H] = 120.9.
©
Georg Thieme Verlag Stuttgart · New York — Synlett 2018, 29, A–F