Palladium-catalyzed Suzuki cross-coupling of arylhydrazines via C-N bond cleavage

Article abstract of DOI:10.1021/jo500026g

The first example of Pd-catalyzed Suzuki cross-coupling of readily available arylhydrazines with arylboronic acids via C-N bond cleavage was developed under air, affording various biaryl compounds with broad substrate applicability and moderate to good yields. Moreover, the rigorous exclusion of air/moisture is not required in these transformations. Thus, the protocol represents a simple and efficient procedure to access biaryl compounds.

Full text of DOI:10.1021/jo500026g

Note
pubs.acs.org/joc
Palladium-Catalyzed Suzuki Cross-Coupling of Arylhydrazines via
C−N Bond Cleavage
Zhimin Peng,† Gaobo Hu,† Hongwei Qiao,† Pengxiang Xu,*,† Yuxing Gao,*,† and Yufen Zhao†,‡
†Department of Chemistry and Key Laboratory for Chemical Biology of Fujian Province, College of Chemistry and Chemical
Engineering, Xiamen University, Xiamen 361005 Fujian, China
‡Key Laboratory of Bioorganic Phosphorus Chemistry and Chemical Biology (Ministry of Education), Department of Chemistry
Tsinghua University, Beijing 100084, China
S
* Supporting Information
ABSTRACT: The first example of Pd-catalyzed Suzuki cross-coupling of readily available arylhydrazines with arylboronic acids
via C−N bond cleavage was developed under air, affording various biaryl compounds with broad substrate applicability and
moderate to good yields. Moreover, the rigorous exclusion of air/moisture is not required in these transformations. Thus, the
protocol represents a simple and efficient procedure to access biaryl compounds.
Scheme 1. (1) Palladium-Catalyzed Suzuki Cross-Coupling
of N′-Tosylarylhydrazines. (2) Palladium-Catalyzed Suzuki
Cross-Coupling of Arylhydrazines
alladium-catalyzed cross-coupling reactions via selective
1
Pcleavage of unreactive bonds such as carbon−hydrogen,
carbon−carbon,2 and carbon−nitrogen bonds have been used
as one of the most powerful synthetic tools for the construction
of carbon−carbon and carbon−heteroatom bonds because they
afford unique organic transformations which are not readily
available by classic methods. Among these methods, the
exploration of the cross-coupling reactions involving carbon−
nitrogen bond cleavage is rare, especially for the nonactivated
carbon−nitrogen bonds,3 which are generally activated through
conversion to diazonium salts,3a−c ammonium salt,3d−f
azaheterocycles,3g,h or tosylhydrazones.3i However, these
methods suffer from drawbacks (e.g., limited substrate scope,
the unstable nature of the substrates or harsh reaction
conditions, etc.) as a result of limited application. Diaryl
compounds are ubiquitous structural motifs that frequently
occur in natural products and pharmacologically active
compounds. Thus, the development of new methods for the
preparation of diaryl compounds under relatively mild reaction
conditions has received much attention. Although various
coupling partners have been explored to synthesize biaryls with
arylboranes in the presence of palladium catalysts in the past
few decades,4 electrophilic counterparts have been substantially
limited to organic halides and triflate. Thus, there is still a need
for broadening the scope of electrophilic partners to achieve
unique organic transformations that are not obtainable through
known approaches. Recently, Lu and co-workers reported the
Pd-catalyzed Suzuki cross-coupling of N′-tosyl arylhydrazines
for the preparation of biaryl compounds (Scheme 1).5
However, this approach was complicated by the need to
prepare N′-tosyl arylhydrazine substrates beforehand. On the
other hand, arylhydrazines are readily obtainable and extremely
valuable compounds in organic chemistry that are widely used
for the preparation of numerous nitrogen-containing com-
pounds, but little attention has been paid to their use as
arylating regents via denitrogenation. Recently, Loh and co-
workers reported the first example of the Pd-catalyzed C−C
bond formation of arylhydrazines with olefins via C−N bond
cleavage.6 Very recently, Pd-catalyzed direct denitrogenative C-
3-arylation of 1H-indoles with arylhydrazines via C−N bond
cleavage has been developed.7 However, to the best of our
knowledge, the Pd-catalyzed direct cross-coupling of arylhy-
drazines with arylboronic acids has not been reported. Herein,
we disclose the first Pd-catalyzed direct Suzuki cross-coupling
of arylhydrazines with arylboronic acids for the synthesis of
valuable biaryl motifs via C−N bond cleavage.
To optimize the catalysis conditions, phenylboronic acid
(1a) and phenylhydrazine (2a) were selected as the model
substrates, and some representative results are shown in Table
1. Initially, we attempted to explore the coupling of 1a with 2a
using Pd(OAc)2 as a catalyst, PPh3 as a ligand, PivOH as an
acid, and DMF as a solvent at 90 °C under open air, and the
desired product 3aa was obtained in 47% yield (Table 1, entry
1). Encouraged by this result, we further examined the effect of
catalyst, solvent, ligand, temperature, and acid on the reaction
yield. Various transition-metal complexes including Pd, Ni, and
Cu salts were examined, with the finding that palladium salts,
Received: January 7, 2014
Published: February 21, 2014
© 2014 American Chemical Society
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Note
a
reaction of various arylboronic acids with phenylhydrazine 2a.
As shown in Table 2, the substrates having different electron-
withdrawing and electron-donating substituents were all
efficiently coupled to afford the corresponding oxidative
coupling products with moderate to good yields, demonstrating
that this new Pd-catalyzed aerobic oxidative Suzuki coupling is
a general and practically useful method for the preparation of
various valuable biaryls. Thus, a variety of functionalities, such
as methyl (1b, 1c), alkoxyl (1d), fluoro (1e), chloro (1f),
trifluoromethyl (1g), and amino (1k), were all tolerated under
similar reaction conditions. Notably, the p-tolylboronic acid 1b
and meta-substituted counterpart 1c afforded similar yields of
77% and 73%, respectively, but sterically demanding o-
tolylboronic acid only gave a very low yield of 12%, illustrating
that this coupling reaction is sensitive to sterichindrance
(entries 2 and 3). Gratifyingly, both bulky 2-naphthylboronic
acid 1i and 3,4-methylenedioxyphenylboronic acid 1j were also
good coupling partners for this oxidative coupling reaction,
giving the corresponding products in good yields (3ia, 3ja,
76%, 88%, respectively, entries 9−10). Nevertheless, boronic
ester 1l and potassium phenyltrifluoroborate 1n were not
suitable for this protocol (entries 12 and 13).
To gain more insight into the substrate scope of this coupling
reaction, a variety of arylhydrazines and arylboronic acids were
further evaluated under the optimal reaction conditions (Table
3). It was found that various arylboronic acids and
arylhydrazines containing both electron-donating and elec-
tron-withdrawing groups were all good coupling partners in this
transformation. Thus, besides phenylhydrazine (2a), other
arylhydrazines with various substituents could also react with
phenylboronic acid (1a) to afford the corresponding products
in moderate to good yields (entries 1−5). Notably, arylboronic
acids containing electron-withdrawing groups such as 4-
fluorophenylboronic acid (1e) also coupled well with
arylhydrazines bearing electron-withdrawing groups such as 4-
nitrophenylhydrazine (2e) and 4-hydrazinobenzoic acid (2k),
and the desired biaryls products 3ee and 3ek were obtained in
72% and 93% yields, respectively (entries 10 and 11). We also
detected this reaction with alkylhydrazines such as benzylhy-
drazine under similar conditions but observed no coupling
products, probably due to the low stability of alkyl
intermediates.
Table 1. Optimization of the Reaction Conditions
entry
catalyst
ligand
PPh3
acid
solvent
yield (%)
1
Pd(OAc)2
Pd2(dba)3
PdCl2
PivOH
PivOH
PivOH
PivOH
PivOH
PivOH
PivOH
PivOH
PivOH
PivOH
PivOH
PivOH
PivOH
PivOH
PivOH
PivOH
PivOH
TFA
DMF
NMP
NMP
NMP
NMP
NMP
NMP
NMP
DMA
DMSO
dioxane
toluene
NMP
NMP
NMP
NMP
NMP
NMP
NMP
NMP
NMP
NMP
NMP
47
28
6
2
PPh3
PPh3
PPh3
PPh3
PPh3
PPh3
PPh3
PPh3
PPh3
PPh3
PPh3
bpy
3
4
Pd(PPh3)4
Cu(OAc)2
Ni(OAc)2
43
0
5
6
0
7
0
8
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
78
46
4
9
10
11
12
13
14
15
16
17
18
19
20
69
47
8
1,10-Phen
dppp
dppb
dppe
PPh3
PPh3
PPh3
PPh3
PPh3
PPh3
25
37
14
7
60
10
39
77
70
74
CF3SO3H
AcOH
PivOH
PivOH
PivOH
b
21
c
22
d
23
a
Conditions:1a (0.50 mmol), 2a (1.75 mmol), catalyst (5 mol %),
ligand (15 mol % for bidentate, 30 mol % for monodentate), acid
b
(0.75 mmol), solvent (2 mL), 4 h, 90 °C, under open air. Using 10
c
d
mol % of Pd(OAc)2. At 110 °C. Under O2.
especially Pd(OAc)2, were the optimal choice for the coupling
reaction (Table 1, entries 1−4). In contrast, other metal salts
such as Cu(OAc)2 and Ni(OAc)2 gave no corresponding
product (entries 5 and 6). Additionally, the reaction did not
occur in the absence of Pd(OAc)2, illustrating that Pd(OAc)2
catalyst was essential to achieve a high yield (entry 7). The type
of solvent was vital to the present catalytic reaction. 1-
Methylpyrrolidin-2-one (NMP) was found to be the best
choice and gave yields up to 78% (entries 8−12). To advance
the process further, a subsequent survey on the role of ligands
showed PPh3 as the most favored one to push the reaction
forward (entries 8 and 13−17). Among the various acids
screened, pivalic acid (PivOH) turned out to be the best acid
and enhanced the coupling to provide 3aa in 78% yield (entry
8). Other acids and corresponding yields were as follows: TFA,
60%; CF3SO3H, 10%; and CH3COOH, 39% (entries 18−20).
Notably, in the absence of either air or pivalic acid, the
couplings only gave 6% and 16% yields, respectively, indicating
that they were involved in the reaction process. Using pure
oxygen as the oxidant instead of air, the yield dropped slightly
to 74% (entry 23). Note that increasing the load of Pd(OAc)2
to 10 mol % and raising the temperature from 90 to 100 °C did
not improve the yield (entries 21 and 22). In the absence of
either phenylhydrazine (1a) or phenyl boronic acid (2a), the
reaction only generated a trace amount of product 3aa,
disclosing that self-coupling of 1a or 2a was not performed
smoothly under the present Pd-catalysis system.
A plausible mechanism was illustrated in Scheme 2. Initially,
palladiaziridine complex A was formed in the presence of
substrate 2a and Pd(II)2L2, which has been established by
Muniz.8 Then oxidative addition of complex A with Pd(0)L
̃
2
generated the palladium(II)-centered complex B via C−N bond
cleavage.6 Next, protonolysis of B resulted in the formation of
the aryl palladium complex C and the palladiaziridine complex
D, which was decomposed into Pd(0)L2, N2, and H2O by air.
The arylpalladium complex C could be transformed to a
palladium(II) biaryl intermediate E in the presence of
phenylboronic acid 1a. Subsequently, intermediate E would
undergo C−C reductive elimination to give the desired product
3aa and Pd(0)L2. Finally, the catalytic cycle was completed
through reoxidation of Pd(0) to Pd(II) by air with the
assistance of a ligand and an acid via the peroxopalladium
complex.9 Obviously, the acid is a key factor in the overall
transformation. A delicate pKa balance might be reached
between phenylhydrazine and the acid in order to prevent
complete protonation of the former to avoid inhibiting Pd
coordination and promote the aerobic reoxidation of Pd(0).
Under the optimized reaction conditions in footnote a, Table
2, the generality of this novel process was extended to the
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Note
a
Table 2. Suzuki Reaction of Phenylhydrazine with Arylboronic Acids
a
Conditions: 1 (0.50 mmol), 2a (1.75 mmol), Pd(OAc)2 (5 mol %), PPh3 (30 mol %), PivOH (0.75 mmol), NMP (2 mL), 4 h, 90 °C, under open
air.
range of readily available unactivated arylhydrazines with
arylboronic acids, providing a simple and practical synthetic
tool for the preparation of various biaryl compounds via C−N
bond cleavage. The noticeable advantages of this protocol
include the use of air as a green oxidant, with no need for
exclusion of moisture or air and broad substrate applicability.
Importantly, in contrast, the direct use of arylhydrazines
without the need to simultaneously prepare N′-tosylarylhy-
drazines, improving greatly the reaction efficiency, represents a
prominent advantage of the method. This protocol further
extends the scope of C−C bond construction and should be an
efficient complement to the classical Suzuki cross-coupling
reaction.
Scheme 2. Proposed Mechanism
EXPERIMENTAL SECTION
■
All reactions were carried out under air. Purification of reaction
products was carried out by flash chromatography using silica gel
1
(300−400 mesh). H NMR (400 MHz) and 13C NMR (100 MHz)
spectra were recorded on 400 MHz spectrometers with tetramethylsi-
lane (TMS) as internal standard. All coupling constants are absolute
values, and J values are expressed in hertz. All new compounds were
further characterized by HRMS (FT-ICR-MS). Spectroscopic data of
the known compounds match the data reported in the corresponding
references.
Typical Procedure for Pd-Catalyzed Suzuki Cross-Coulping
of Arylhydrazines with Aryl Boronic Acids. A mixture of aryl
boronic acid 1 (0.5 mmol, 61 mg), arylhydrazine 2 (1.75 mmol, 189
mg), Pd(OAc)2 (0.025 mmol, 5.6 mg), PPh3 (0.15 mmol, 39.3 mg),
In summary, we have developed a novel and efficient
methodology that allows for the construction of C−C bonds
through Pd-catalyzed air-based oxidative coupling of a wide
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Note
a
Table 3. Suzuki Reaction of Arylboronic Acids with Arylhydrazines
a
Conditions: 1 (0.50 mmol), 2 (1.75 mmol), Pd(OAc)2 (5 mol %), PPh3 (30 mol %), PivOH (0.75 mmol), NMP (2 mL), 4 h, 90 °C, under open
air.
and trimethylacetic acid (0.75 mmol, 76.5 mg) was stirred at 90 °C in
7.45 (m, 2H), 7.41−7.37 (m, 1H), 7.19−7.14 (m, 2H). 13C{1H} NMR
(CDCl3, 100 MHz): δ 162.6 (d, JC−F = 246.3 Hz), 140.4, 137.5 (d,
JC−F = 3.35 Hz), 129.0, 128.8 (d, JC−F = 8.04 Hz), 127.4, 127.2, 115.7
(d, JC−F = 21.35 Hz). IR νmax (cm−1): 1595, 1486, 1451, 1105, 837,
758, 687. GC−MS m/z: 172 (M+, 100).
N-methylpyrrolidone (2 mL) for 4 h under air. After completion of the
reaction (indicated by TLC), the mixture was concentrated under
vacuum and the crude product was purified by silica gel
chromatography using petroleum ether as eluent to provide the
corresponding product 3.
4-Chlorobiphenyl13 (3fa) (CAS No. 2051-62-9). White solid; 77
Spectral Data of the Compounds. Biphenyl10 (3aa) (CAS no.
92-52-4). White solid; 60 mg, 78% yield. 1H NMR (CDCl3, 400
MHz): δ 7.62−7.59 (m, 4H), 7.47−7.42 (m, 4H), 7.37−7.33 (m, 2H).
13C{1H} NMR (CDCl3, 100 MHz): δ 141.4, 128.9, 127.4, 127.3. IR
mg, 82% yield. H NMR (CDCl3, 400 MHz): δ 7.64−7.53 (m, 4H),
1
7.49−7.37 (m, 5H). 13C{1H} NMR (CDCl3, 100 MHz): δ 140.1,
139.8, 133.5, 129.04, 129.01, 128.5, 127.7, 127.1. IR νmax (cm−1): 1478,
1398, 1093, 832, 758, 689. GC−MS m/z: 188 (M+, 100).
νmax (cm−1): 1568, 1481, 1428, 1343, 902, 728, 696. GC−MS m/z:
154 (M+,100).
3-(Trifluoromethyl)biphenyl14 (3ga) (CAS No. 366-04-1). White
solid; 77 mg, 70% yield. 1H NMR (CDCl3, 400 MHz): δ 7.86 (s, 1H),
7.78 (d, J = 7.60 Hz, 1H), 7.63−7.55 (m, 4H), 7.51−7.47 (m, 2H),
7.44−7.39 (m, 1H). 13C{1H} NMR (CDCl3, 100 MHz): δ 142.2,
4-Methylbiphenyl10 (3ba) (CAS No. 644-08-6). White solid; 64 mg,
77% yield. 1H NMR (CDCl3, 400 MHz): δ 7.68−7.65 (m, 2H), 7.59−
7.57 (m, 2H), 7.52−7.48 (m, 2H), 7.42−7.38 (m, 1H), 7.34−7.32 (m,
2H), 2.47 (s, 3H). 13C{1H} NMR (CDCl3, 100 MHz): δ 141.3, 138.5,
137.1, 129.6, 128.8, 127.3, 127.12, 127.10, 21.2. IR νmax (cm−1): 3027,
2922, 1487, 822, 755, 695. GC−MS m/z: 168 (M+, 100).
3-Methylbiphenyl11 (3ca) (CAS No. 643-93-6). White solid; 61 mg,
73% yield. 1H NMR (CDCl3, 400 MHz): δ 7.66−7.64 (m, 2H), 7.51−
7.45 (m, 4H), 7.41−7.37 (m, 2H), 7.23 (d, J = 7.40 Hz, 1H), 2.48 (s,
3H). 13C{1H} NMR (CDCl3, 100 MHz): δ 141.5, 141.4, 138.4,
128.82, 128.80, 128.13, 128.11, 127.31, 127.29, 124.4, 21.6. IR νmax
(cm−1): 3058, 3029, 2918, 1600, 1481, 791, 752, 698. GC−MS m/z:
168 (M+, 100).
140.0, 131.5, 131.2, 130.6, 129.4, 129.2, 128.2, 127.4, 124.4 (q, JC−F
=
272.50 Hz), 124.1 (q, JC−F = 3.05 Hz). IR νmax (cm−1): 1424, 1334,
1261, 1166, 1126, 758, 701. GC−MS m/z: 222 (M+, 100).
4-(Trifluoromethoxy)biphenyl14 (3ha) (CAS No. 71274−84−5).
White solid; 63 mg, 53% yield. 1H NMR (CDCl3, 400 MHz): δ 7.64−
7.57 (m, 4H), 7.50−7.45 (m, 2H), 7.42−7.38 (m, 1H), 7.33−7.31 (m,
2H). 13C{1H} NMR (CDCl3, 100 MHz): δ 148.9, 140.2, 140.0, 129.0,
128.6, 127.8, 127.3, 122.0, 121.4, 119.4. IR νmax (cm−1): 1486, 1211,
1155, 1005, 851, 765, 736, 690. GC−MS m/z: 238 (M+,100).
2-Phenylnaphthalene13 (3ia) (CAS No. 612-94-2). White solid; 77
1
mg, 76% yield. H NMR (CDCl3, 400 MHz): δ 8.09 (s, 1H), 7.97−
4-Methoxybiphenyl11 (3da) (CAS No. 613−37−6). White solid; 51
7.89 (m, 3H), 7.81−7.76 (m, 3H), 7.57−7.50 (m, 4H), 7.45−7.40 (m,
1H). 13C{1H} NMR (CDCl3, 100 MHz): δ 141.3, 138.7, 133.8, 132.8,
129.0, 128.6, 128.3, 127.8, 127.6, 127.5, 126.4, 126.1, 125.9, 125.7. IR
νmax (cm−1): 3056, 1452, 1264, 859, 820, 770, 757, 688. GC−MS m/z:
204 (M+, 100).
1
mg, 56% yield. H NMR (CDCl3, 400 MHz): δ 7.63−7.58 (m, 4H),
7.47 (t, J = 7.64 Hz, 2H), 7.38−7.34 (m, 1H), 7.05−7.03 (m, 2H),
3.89 (s, 3H). 13C{1H} NMR (CDCl3, 100 MHz): δ 159.3, 140.9,
133.87, 128.84, 128.3, 126.84, 126.77, 114.3, 55.4. IR νmax (cm−1):
2961, 1606, 1486, 1268, 1035, 833, 760, 688. GC−MS m/z: 184 (M+,
100).
5-Phenylbenzo[d][1,3]dioxole15 (3ja) (CAS No. 24382-05-6).
Yellow oil; 87 mg, 88% yield. 1H NMR (CDCl3, 400 MHz): δ
7.59−7.57 (m, 2H), 7.48−7.44 (m, 2H), 7.39−7.35 (m, 1H), 7.14−
7.11 (m, 2H), 6.94 (d, J = 7.96 Hz, 1H), 6.02 (s, 2H); 13C{1H} NMR
4-Fluorobiphenyl12 (3ea) (CAS No. 324-74-3). White solid; 64 mg,
75% yield. 1H NMR (CDCl3, 400 MHz): δ 7.61−7.56 (m, 4H), 7.50−
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Note
(CDCl3, 100 MHz): δ 148.2, 147.2, 141.0, 135.7, 128.8, 127.01,
126.97, 120.7, 108.7, 107.8, 101.2. IR νmax (cm−1): 3061, 2890, 2777,
1601, 1478, 1454, 1224, 1106, 1039, 936, 889, 812, 759, 697. GC−MS
m/z: 198 (M+, 100).
115.8 (d, JC−F = 21.5 Hz). IR νmax (cm−1): 2916, 1500, 1108, 821, 763,
737. GC−MS m/z: 190 (M+,100).
4-Fluoro-4′-nitrobiphenyl21 (3ee) (CAS No. 398-24-3). White
1
solid; 78 mg, 72% yield. H NMR (CDCl3, 400 MHz): δ 8.30−8.27
N,N-Diphenyl[1,1-biphenyl]-4-amine16 (3ka) (CAS No. 4432-94-
(m, 2H), 7.71−7.67 (m, 2H), 7.62−7.57 (m, 2H), 7.21−7.16 (m, 2H).
1
13C{1H} NMR (CDCl3, 100 MHz): δ 163.5 (d, JC−F = 249.4 Hz),
4). White solid; 83 mg, 52% yield. H NMR (CDCl3, 400 MHz): δ
7.61−7.59 (m, 2H), 7.52−7.49 (m, 2H), 7.46−7.42 (m, 2H), 7.35−
7.27 (m, 5H), 7.18−7.16 (m, 6H), 7.08−7.04 (m, 2H); 13C{1H} NMR
(CDCl3, 100 MHz): δ 147.8, 147.3, 140.8, 135.3, 129.4, 128.9, 127.9,
127.0, 126.8, 124.6, 124.1, 123.1. IR νmax (cm−1): 3058, 3030, 1590,
1518, 1484, 1325, 1277, 837, 753, 695. GC−MS m/z: 321 (M+,100).
3-Methoxybiphenyl17 (3ab) (CAS No. 2113-56-6). White solid; 61
147.2, 146.7, 135.0 (d, JC−F = 3.37 Hz), 129.3 (d, JC−F = 8.33 Hz),
127.8, 124.3, 116.3 (d, JC−F = 21.81 Hz). IR νmax (cm−1): 2915, 1596,
1511, 1356, 1232, 832, 754, 715. GC−MS m/z: 217 (M+,100).
4′-Fluorobiphenyl-4-carboxylic Acid22 (3ek) (CAS No. 5731-10-2).
White solid; 100 mg, 93% yield. 1H NMR (DMSO−D6, 400 MHz): δ
12.98 (br, 1H), 8.01 (d, J = 8.36 Hz, 2H), 7.79−7.76 (m, 4H) 7.32 (t, J
= 8.84 Hz, 2H). 13C{1H} NMR (CDCl3, 100 MHz): δ 167.1, 162.3 (d,
JC−F = 245.7 Hz), 143.2, 135.5, 130.0, 129.6, 129.0 (d, JC−F = 8.30 Hz),
126.7, 115.9 (d, JC−F = 21.35 Hz). IR νmax (cm−1): 3438, 2252, 2125,
1657, 1053, 1027, 1007, 823, 761. GC−MS m/z: 216 (M+, 100).
2-Chloro-6-(4-fluorophenyl)pyridine23 (3el) (CAS No. 1214354-
55-8). White solid; 41 mg, 40% yield. 1H NMR (CDCl3, 400 MHz): δ
7.99−7.96 (m, 2H), 7.70−7.66 (m, 1H), 7.59−7.57 (m, 1H), 7.25−
7.23 (m, 1H), 7.16−7.12 (m, 2H). 13C{1H} NMR (CDCl3, 100
MHz): δ 164.0 (d, JC−F = 249.70 Hz), 157.1, 151.5, 139.5, 134.0 (d,
JC−F = 3.21 Hz), 129.0 (d, JC−F = 8.52 Hz), 122.6, 118.4, 115.9 (d, JC−F
= 21.67 Hz). IR νmax (cm−1): 1580, 1558, 1511, 1387, 1236, 1166,
1136, 1054, 909, 851, 792, 735. GC−MS m/z: 207 (M+, 100).
1
mg, 67% yield. H NMR (CDCl3, 400 MHz): δ 7.65−7.63 (m, 2H),
7.48 (t, J = 7.50 Hz, 2H), 7.42−7.37 (m, 2H), 7.25−7.22 (m, 1H),
7.19−7.18 (m, 1H), 6.96−6.93 (m, 1H), 3.90 (s, 3H). 13C{1H} NMR
(CDCl3, 100 MHz): δ 160.1, 142.9, 141.2, 129.9, 128.9, 127.5, 127.3,
119.8, 113.0, 112.8, 55.4. IR νmax (cm−1): 3030, 2833, 1598, 1572,
1478, 1420, 1295, 1213, 1177, 1054, 1038, 1019, 756, 697. GC−MS
m/z: 184 (M+,100).
4-(Trifluoromethyl)biphenyl10 (3ac) (CAS No. 398-36-7). White
1
solid; 83 mg, 75% yield. H NMR (CDCl3, 400 MHz): δ 7.72 (br,
4H), 7.64−7.62 (m, 2H), 7.53−7.48 (m, 2H), 7.46−7.42 (m, 1H).
13C{1H} NMR (CDCl3, 100 MHz): δ 144. 9, 139.9, 129.5 (q, JC−F
=
32.56 Hz), 129.1, 128.3, 127.6, 127.4, 125.9 (q, JC−F = 3.69 Hz), 124.5
(q, JC−F = 271.8 Hz). IR νmax (cm−1): 1614, 1489, 1404, 1352, 1114,
1075, 843, 767, 728, 691. GC−MS m/z: 222 (M+, 100).
ASSOCIATED CONTENT
■
3-Nitrobiphenyl18 (3ad) (CAS No. 2113-58-8). White solid; 52 mg,
53% yield. 1H NMR (CDCl3, 400 MHz): δ 8.45 (t, J = 1.96 Hz, 1H),
8.21−8.19 (m, 1H), 7.93−7.91 (m, 1H), 7.64−7.59 (m, 3H), 7.52−
7.48 (m, 2H), 7.45−7.42 (m, 1H); 13C{1H} NMR (CDCl3, 100
MHz): δ 148.9, 143.0, 138.8, 133.2, 129.8, 129.3, 128.7, 127.3, 122.1,
122.06. IR νmax (cm−1): 1528, 1501, 1350, 764, 730, 696. GC−MS m/
z: 199 (M+, 100).
S
* Supporting Information
1
Copies of H NMR and 13C NMR spectra. This material is
available free of charge via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Authors
*E-mail: xpengxiang@xmu.edu.cn.
*E-mail: gaoxingchem@xmu.edu.cn.
■
4-Nitrobiphenyl10 (3ae) (CAS No. 92-93-3). White solid; 63 mg,
64% yield. 1H NMR (CDCl3, 400 MHz): δ 8.31−8.28 (m, 2H), 7.75−
7.72 (m, 2H), 7.64−7.61 (m, 2H), 7.53−7.43 (m, 3H). 13C{1H} NMR
(CDCl3, 100 MHz): δ 147.8, 147.2, 138.9, 129.3, 129.1, 127.9, 127.5,
124.2. IR νmax (cm−1): 2916, 2848, 1595, 1505, 1351, 852, 773, 739,
699. GC−MS m/z: 199 (M+,100).
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
1,4-Diphenylbenzene13 (3af)(CAS No. 92-94-4). White solid; 58
This work was supported by the Chinese National Natural
Science Foundation (Nos. 21202135 and 21075103) and the
Natural Science Foundation of Fujian Province of China (No.
2013J05031), NFFTBS (No. J1210014), and PCSIRT.
1
mg, 51% yield. H NMR (CDCl3, 400 MHz): δ 7.70 (s, 4H), 7.68−
7.66 (m, 4H), 7.50−7.46 (m, 4H), 7.40−7.36 (m, 2H). 13C{1H} NMR
(CDCl3, 100 MHz): δ 140.9, 140.3, 129.0, 127.6, 127.5, 127.2. IR νmax
(cm−1): 3430, 1632, 1454, 1403, 838, 745, 688. GC−MS m/z: 230
(M+,100).
3,3′-Dimethylbiphenyl19 (3cg) (CAS No. 612-75-9). Colorless oil;
REFERENCES
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1
69 mg, 76% yield. H NMR (CDCl3, 400 MHz): δ 7.46−7.41 (m,
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solid; 78 mg, 84% yield. H NMR (CDCl3, 400 MHz): δ 7.57−7.54
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1
mg, 79% yield. H NMR (CDCl3, 400 MHz): δ 7.52−7.47 (m, 4H),
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2737
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