Palladium(II)-catalyzed direct regioselectively oxidative acylation of azobenzenes with toluene derivatives

Article abstract of DOI:10.1021/jo5000219

A highly efficient and practical procedure to acylazobenzene via Pd-catalyzed oxidative C-H bond activation from toluene has been developed. Various mono- and diacylazobenzene were afforded simultaneously in moderate to excellent yields for 33 examples. Toluene and its derivatives were served as potential and ideal acylation reagents. The mono- and diacylated products could be controlled by the oxidant loading.

Full text of DOI:10.1021/jo5000219

Article
pubs.acs.org/joc
Palladium(II)-Catalyzed Direct Regioselectively Oxidative Acylation of
Azobenzenes with Toluene Derivatives
Hongyu Song,† Dong Chen,† Chao Pi,† Xiuling Cui,*,†,‡ and Yangjie Wu*,†
†Department of Chemistry, Henan Key Laboratory of Chemical Biology and Organic Chemistry, Key Laboratory of Applied
Chemistry of Henan Universities, Zhengzhou University, Zhengzhou, 450052 P. R. China
‡School of Biomedical Sciences, Engineering Research Center of Molecular Medicine of Chinese Education Ministry, Xiamen Key
Laboratory of Ocean and Gene Drugs, Institute of Molecular Medicine of Huaqiao University, Fujian, Xiamen, 361021 P. R. China
S
* Supporting Information
ABSTRACT: A highly efficient and practical procedure to acylazobenzene via Pd-catalyzed oxidative C−H bond activation from
toluene has been developed. Various mono- and diacylazobenzene were afforded simultaneously in moderate to excellent yields
for 33 examples. Toluene and its derivatives were served as potential and ideal acylation reagents. The mono- and diacylated
products could be controlled by the oxidant loading.
dibenzoylated products. To the best of our knowledge, this is
the first case to access dibenzoylated azobenzenes via transition
metal-catalyzed C−H bond activation.
INTRODUCTION
■
Acylazobenzene and its derivatives are ubiquitous motifs and
have been widely applied in the fields of functional advanced
materials, chemical sensors, pharmaceuticals, food additives,
and industrial dyes.1 However, the process of building such a
structure has lagged behind. Only several impressive examples
have emerged in the recent two years. For instance, the
research group of Wang developed the acylation of azobenzene
by Pd-catalyzed oxidative coupling of azobenzenes with
aldehydes using tert-butyl hydroperoxide (TBHP) as an oxidant
via chelation-assisted ortho C−H bond activation.2 Then, they
further disclosed the palladium-catalyzed decarboxylative ortho-
acylation of azobenzenes with α-oxocarboxylic acids.3
Remarkable progress has made on aldehydes, α-oxocarbox-
ylic acids, or alcohol as a reactant for the acylation of aromatic
compounds based on transition metal-catalyzed C−H
activation.4,5 Recently, great attention has been paid to the
use of toluene and its derivatives as acylation reagents, due to
its stability, low toxicity, and ample availability compared to
those of aldehydes and α-oxocarboxylic acids. Patel,6 Kwong,7
Sun,8 and Zhang9 independently realized the regioselective
acylation of 2-phenylpyridine and acetanilide with toluene
derivatives to afford o-acyl-2-phenylpyridines and o-acylaceta-
nilides. Recently, the Lu10 group reported the acylation of
azobenzene with toluene to afford acylated products. Herein,
we present a highly efficient and regioselective acylation of
azobenzenes with toluene and its derivatives catalyzed by
palladium in the presence of TBHP, leading to a variety of
acylazobenzenes. Both mono- and diacylazobenzene were
obtained simultaneously. Further investigation revealed that
TBHP loading contributed to the distribution of mono- and
RESULTS AND DISCUSSION
■
The condensation of azobenzene 1a and toluene 2a was initially
chosen as a model reaction to screen the reaction parameters.
The results are summarized in Table 1. The reaction was
carried out in toluene at 80 °C with 10 mol % Pd(OAc)2 as a
catalyst and TBHP (4 equiv, 70% solution in water) as an
oxidant. As expected, this protocol was feasible and the desired
o-benzoylazobenzene 3a was afforded in 49% yield (entry 1).
When the reaction temperature was reduced, the yield was
decreased to 38% (entry 2). Screening solvents revealed that
CH3CN and DCE were effective solvents (entries 3−4), while
other solvents, such as DMSO, DMF, and dioxane turned out
to be inferior in the model reaction (entries 5−7). When the
mole ratio of toluene and CH3CN was changed from 1/1 (v/v)
to 3/1 (v/v), the yield was increased obviously and reached
80% (entry 8−9). It could be concluded that solvent played a
crucial role, and CH3CN proved to be the best solvent for this
transformation. Furthermore, different Pd catalysts were also
investigated, in which Pd(OAc)2 exhibited the highest activity.
Other Pd sources including Pd(TFA)2 and PdCl2 did not
enhance the yield of product 3a (entries 11 and 12). Further
exploration on TBHP loading was also examined and indicated
that 4 equiv of TBHP could bring the highest yield of 80%.
Increasing the TBHP loading to 6 equiv or decreasing to 3
Received: January 6, 2014
Published: March 6, 2014
© 2014 American Chemical Society
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a
Table 1. Optimization of the reaction conditions for the condensation of azobenzene 1a with toluene 2a
b
entry
catalyst
oxidant (equiv)
solvent (v/v)
PhCH3
T (°C)
yield (%)
1
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(TFA)2
PdCl2
TBHP (4)
TBHP (4)
TBHP (4)
TBHP (4)
TBHP (4)
TBHP (4)
TBHP (4)
TBHP (4)
TBHP (4)
TBHP (3)
TBHP (4)
TBHP (4)
TBHP (5)
TBHP (6)
TBHP (15)
80
70
80
80
80
80
80
80
80
80
80
80
80
80
80
49
38
2
PhCH3
3
PhCH3/CH3CN (1:1)
PhCH3/DCE (1:1)
PhCH3/DMSO (1:1)
PhCH3/DMF (1:1)
PhCH3/dioxane (1:1)
PhCH3/CH3CN (2:1)
PhCH3/CH3CN (3:1)
PhCH3/CH3CN (3:1)
PhCH3/CH3CN (3:1)
PhCH3/CH3CN (3:1)
PhCH3/CH3CN (3:1)
PhCH3/CH3CN (3:1)
PhCH3
70
4
59
5
trace
trace
trace
65
6
7
8
9
80
10
11
12
13
14
15
57
68
55
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
75
67
83
a
Reaction conditions: azobenzene 1a (0.2 mmol), catalyst (10 mol %), TBHP (4 equiv), solvent (2 mL), 80 °C under air atmosphere for 24 h.
Isolated yields.
b
a
Table 2. Ortho-acylation of azobenzenes with toluene
a
Reaction conditions: azobenzene derivatives (0.2 mmol), toluene (1.5 mL), Pd(OAc)2 (10 mol %), TBHP (4 equiv), CH3CN (0.5 mL) at 80 °C
under air atmosphere for 24 h.
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equiv could not improve the yield evidently (entries 10, 13, 14).
Only monoacylated product 3a was afforded under the above-
mentioned reaction conditions. To our surprise, when the
TBHP loading was increased to 15 equiv, a diacylated product
3b was afforded in 83% yield (entry 15). Monoacylated product
3a was not observed, while a trace amount of triacylated
product was detected. These results indicated that the loading
of TBHP contributed to the distribution of mono- and
dibenzoylated products.
Table 3. Ortho-acylation of azobenzene with toluene
derivatives
a
With the optimized reaction conditions in hand, the ortho-
acylation of various azobenzenes with toluene was investigated
and the results were summarized in Table 2. Moderate to
excellent yields were obtained for most cases. In general, the
azobenzenes with electron-donating groups gave higher yields
than those with electron-withdrawing groups. Electron-rich
azobenzenes, such as azobenzene, 2,2′-dimethylazobenzene,
3,3′-dimethylazobenzene, bis(3,5-dimethyl)-azobenzene, 4,4′-
dimethylazobenzene, 3,3′-dimethoxyazobenzene, 4,4′-dime-
thoxyazobenzene provided the corresponding products in
76−91% yields (3a, 3ba−3ga). Azobenzenes with electron-
withdrawing groups, for example, 4,4′-difluoroazobenzene, 4,4′-
dichloroazobenzene, 3,3′-dibromoazobenzene, and 4,4′-di-
(trifluoromethoxy)azobenzene gave the desired products in
50−68% yields (3ha−3la). The strong electron-withdrawing
group, such as NO2, obviously restrained the reaction and could
not afford the desired product under the standard reaction
conditions. These results further demonstrated that the
electron density of substrates played a more important role
than the steric hindrance. No significant steric effect of the
ortho- or meta-substituted azobenzene was found in the
acylation reaction. 2,2′-Dimethylazobenzene, 3,3′-dimethylazo-
benzene, bis(3,5-dimethyl)azobenzene could give similar yields
(3a vs 3ba, 3ca, 3da). An excellent regioselectivity was found
for the meta-substituted azobenzenes (3ca, 3fa, 3ja), in which
the acylation reaction only occurred at the para-position of the
substituent group, largely due to the steric hindrance.
Next, we tested the scope of the toluene derivatives as the
acylation reagents (Table 3). Both electron-deficient (such as F,
Cl, Br; 3aa−3af) and electron-rich (such as CH3O, CH3; 3ag−
3ak) toluene derivatives could proceed smoothly and afford the
corresponding acylated products in moderate to good yields.
This transformation was slightly affected by the steric
hindrance. Toluene substituted at the para-position gave higher
yields than those with ortho-substituted groups. For examples,
4-chlorotoluene and 4-bromotoluene gave 87% and 83% yields
respectively, while 2-chlorotoluene, 2-bromotoluene only gave
59% and 61% yields (3ab vs 3ad and 3ac vs 3ae). To our
delight, halo groups (F, Cl, Br) on the aromatic ring remained
intact in the products, which provided the possibility for the
further useful transformations (3aa−3ae). It is worth noting
that the reaction only took place on one methyl group and the
other one still remained (such as mesitylene, xylene; 3aj, 3ak)
because the oxidation of one methyl to the carbonyl group
slows down the oxidation of the second methyl group.
a
Reaction conditions: azobenzene (la, 0.2 mmol), toluene derivatives
(1.5 mL), Pd(OAc)2 (10 mol %), TBHP (4 equiv), CH3CN (0.5 mL)
at 80 °C under air atmosphere for 24 h.
F, Cl; 3m, 3n) and triacylazobenzenes were obtained as main
products for those with electron-donating groups (such as CH3,
CH3O; 3r, 3s, 3t, 3u). The molecular structure of the
diacylated product (3o) was further confirmed by single-crystal
X-ray diffraction analysis,11 and the configuration is shown in
Figure 1 in the Supporting Information.
To clarify the reaction mechanism, some controlled experi-
ments were carried out under the optimized conditions as
follows: (1) By adding a radical scavenger (ascorbic acid) to the
reaction,12 this reaction was inhibited, and the rate of reactions
was greatly suppressed. Only a trace amount of the desired
product was detected (Scheme 1a). (2) Benzaldehyde was
obtained in 7% yield from the oxidization of toluene under the
standard reaction condition in the absence of palladium catalyst
and azobenzene (Scheme 1b). 3) With the use of benzaldehyde
as an acylation reagent instead of toluene under the standard
reaction conditions, the desired product 3a was obtained in
45% yield, and benzoic acid was detected (Scheme 1c). Part of
benzaldehyde 2b was oxidated into benzoic acid, whereas
toluene gave higher yield, and an unwanted side reaction was
prevented under the same reaction conditions. Moreover,
toluene and its derivatives are less toxic and more easily
available compared to benzaldehyde. In view of the above
merits, toluene was used as an ideal and efficient acylation
reagent. The results obtained demonstrated that a radical
process was involved in the catalytic system and that the
azobenzene reacted with the benzoyl radical rather than the
benzyl radical.
Then, we investigated the diacylation reaction of azobenzene
(1a) with toluene (2a). The substrate scope was also tested,
and the results are shown in Table 4. When the loading of
TBHP was increased to 15 equiv, a diacylazobenzene was
formed. Azobenzene derivatives substituted with weakly
electron-withdrawing or electron-donating groups could give
moderate to good yields. An amazing phenomenon was
discovered wherein azobenzenes substituted with electron-
withdrawing groups mainly afforded diacylazobenzenes (such as
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Table 4. Multi-acylation of azobenzenes with toluene
derivatives
Scheme 2. Proposed reaction mechanism for Pd(II)-
catalyzed acylation of azobenzene
a
a five-membered cyclopalladated intermediate A,9,14 which has
7
f
been confirmed by previous research. Then the palladacycle A
reacted with the benzoyl radical,15 which was formed in situ
from the oxidation of toluene, and produced the dimeric
Pd(III)16 or reactive Pd(IV)17 species B. Finally, the
intermediate B underwent reductive elimination and provided
the acylazobenzene C. Meanwhile, the Pd(II) was regenerated
for the next catalytic cycle.
CONCLUSIONS
■
In summary, we have developed a highly efficient protocol to
synthesize o-acylazobenzenes through the Pd(II)-catalyzed C−
H bond activation of azobenzenes with toluene derivatives.
Toluene could be used as an ideal acylation reagent in this
transformation. Meanwhile, diacylazobenzenes were obtained
when TBHP loading was increased. Moreover, the mild
reaction conditions together with operational simplicity would
provide an unprecedented capacity in the installation of various
versatile functional groups at various positions of the
azobenzene. It could be applied to the synthesis of natural
products and other available compounds.
a
Reaction conditions: azobenzene derivatives (la, 0.2 mmol), toluene
derivatives (2a, 2 mL), Pd(OAc)2 (10 mol %), TBHP (3 mmol) at 80
°C under air atmosphere for 24 h.
Scheme 1. Controlled experiments
EXPERIMENTAL SECTION
■
General Procedure for Preparation of Azobenzenes. Aryl-
amine (1.0 mmol), CuBr (4.2 mg, 0.03 mmol), pyridine (8.7 mg, 0.09
mmol), and toluene (4 mL) were added together. The mixture was
stirred at 60 °C under air (1 atm) for 20 h, then cooled down to room
temperature. The volatiles were removed under reduced pressure. The
residue was purified by flash chromatography on a short silica gel using
petroleum ether/ethyl acetate (v/v = 50:1) to afford the azobenzene
and its derivatives.
Typical Procedure for the Acylation of Azobenzenes. The
mixture of azobenzene (1a, 36.4 mg, 0.20 mmol), toluene (2a, 1.5
mL). Pd(OAc)2 (4.6 mg, 0.02 mmol), TBHP (4 equiv, 0.8 mmol), and
anhydrous CH3CN (0.5 mL) was stirred at 80 °C for 24 h and then
cooled down to room temperature. The volatiles were removed under
reduced pressure, and the residue was purified by a flash column
chromatography on silica gel using petroleum ether/ethyl acetate (v/v
= 20:1) to give the corresponding monoacylated product.
The mixture of azobenzene (1a, 36.4 mg, 0.20 mmol), toluene (2a,
2 mL), Pd(OAc)2 (4.6 mg, 0.02 mmol), and TBHP (15 equiv, 3
mmol) was stirred at 80 °C for 24 h and then cooled down to room
temperature. The volatiles were removed under reduced pressure. The
On the basis of these results we obtained and found in the
literature3,13 a plausible reaction mechanism that was proposed
and is shown in Scheme 2. First, Pd(OAc)2 reacted with
azobenzene by chelation-directed C−H bond activation to form
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residue was purified by a flash column chromatography on silica gel
using petroleum ether/ethyl acetate (v/v = 7:1 or 4:1) to give the
diacylated product.
(E)-(4-Methoxyphenyl)(2-(phenyldiazenyl)phenyl)-
methanone 3ag: red oil (46 mg, 73%); 1H NMR (400 MHz,
CDCl3): δ 7.92 (d, J = 7.9 Hz, 1H), 7.76 (d, J = 8.8 Hz, 2H), 7,64−
7.60 (m, 1H), 7.59−7.50 (m, 4H), 7.38−7.35 (m, 3H), 6.86 (d, J = 8.8
Hz, 2H), 3.82 (s, 3H). 13C NMR (100 MHz, CDCl3): δ 194.8, 162.4,
151.2, 149.2, 136.8, 131.0, 130.3, 129.8, 129.5, 128.0, 127.6, 122.0,
118.4, 112.6, 54.5. IR (KBr): 3441, 3145, 2920, 2851, 1741, 1660,
1600, 1401, 1257, 1176, 1147, 1029, 932, 846, 775, 690, 609, 561
cm−1. HRMS (ESI) Calcd For C20H16N2O2: [M + H]+, 317.1285,
Found: 317.1285.
(E)-Phenyl(2-(phenyldiazenyl)phenyl)methanone 3a: red oil
1
(46 mg, 80%); H NMR (400 MHz, CDCl3): δ 7.96 (d, J = 7.9 Hz,
1H), 7.82−7.78 (m, 2H), 7.67−7.63 (m, 1H), 7.60−7.58 (m, 2H),
7.50−7.44 (m, 3H), 7.39−7.30 (m, 5H). 13C NMR (100 MHz,
CDCl3): δ 196.1, 151.0, 149.3, 137.4, 135.9, 131.8, 130.4, 129.9, 129.8,
128.4, 127.9, 127.8, 127.3, 121.9, 119.1, 76.4, 76.1, 75.8. HRMS (ESI)
Calcd For C19H14N2O: [M + H]+, 286.1106, Found: 286.1108.
(E)-(4-Fluorophenyl)(2-(phenyldiazenyl)phenyl)methanone
(E)-(2-(Phenyldiazenyl)phenyl)(o-tolyl)methanone 3ah: red
1
1
oil (43 mg, 72%); H NMR (400 MHz, CDCl3): δ 7.79 (d, J = 7.9
3aa: red solid (46 mg, 76%), mp 93−94 °C; H NMR (400 MHz,
Hz, 1H), 7.69 (dd, J = 7.3 Hz, J = 1.2 Hz, 1H), 7.64−7.55 (m, 2H),
7.40−7.33 (m, 5H), 7.27 (t, J = 7.3 Hz, 2H), 7.20 (d, J = 7.5 Hz, 1H),
7.07 (t, J = 7.5 Hz, 1H), 2.56 (s, 3H). 13C NMR (100 MHz, CDCl3): δ
199.5, 152.8, 151.2, 139.5, 138.8, 138.6, 131.9, 131.8, 131.7, 131.6,
131.1, 131.1, 129.8, 129.2, 125.8, 123.3, 119.3, 21.6. IR (KBr): 3438,
3135, 2927, 2852, 1742, 1665, 1401, 1301, 1245, 1161, 928, 774, 731,
689, 635 cm−1. HRMS (ESI) Calcd For C20H16N2O: [M + Na]+,
323.1155, Found: 323.1155.
(E)-(3,5-Dimethylphenyl)(2-(phenyldiazenyl)phenyl)-
methanone 3ai: red oil (41 mg, 66%); 1H NMR (400 MHz,
CDCl3): δ 7.90 (d, J = 7.8 Hz, 1H), 7.66−7.62 (m, 1H), 7.60−7.54
(m, 2H), 7.50 (dd, J = 7.7 Hz, J = 1.4 Hz, 2H), 7.38−7.34 (m, 5H),
7.12 (s, 1H), 2.28 (s, 6H). 13C NMR (100 MHz, CDCl3): δ 196.6,
151.2, 149.5, 137.6, 137.0, 136.5, 133.5, 130.3, 129.7, 129.7, 127.9,
127.7, 126.3, 122.0, 118.7, 20.2. IR (KBr): 3448, 3158, 2923, 2853,
1742, 1662, 1596, 1580, 1447, 1401, 1313, 1284, 1225, 1151, 925, 888,
833, 774, 704, 698, 675, 600 cm−1. HRMS (ESI) Calcd For
C21H18N2O: [M + H]+, 315.1492, Found: 315.1496.
CDCl3): δ 7.95 (d, J = 7.8 Hz, 1H), 7.82−7.77 (m, 2H), 7.68−7.64
(m, 1H), 7.61−7.55 (m, 2H), 7.49−7.46 (m, 2H), 7.41−7.33 (m, 3H),
7.06−7.02 (m, 2H). 13C NMR (100 MHz, CDCl3): δ 196.0, 165.9 (d,
JC−F = 253.1 Hz), 152.4, 150.7, 136.9, 135.3 (d, JC−F = 3.0 Hz), 132.4
(d, JC−F = 9.3 Hz), 131.9, 131.3 (d, JC−F = 3.6 Hz), 129.4, 129.1, 123.3,
120.7, 115.9 (d, JC−F = 21.8 Hz). IR (KBr): 3441, 3134, 2925, 2852,
1742, 1667, 1598, 1505, 1401, 1287, 1237, 1147, 1097, 932, 851, 774,
688, 603 cm−1. HRMS (ESI) Calcd For C19H13FN2O: [M + H]+,
305.1085, Found: 305.1088.
(E)-(4-Chlorophenyl)(2-(phenyldiazenyl)phenyl)methanone
1
3ab: red solid (56 mg, 87%), mp 96−97 °C; H NMR (400 MHz,
CDCl3): δ 7.96−7.94 (m, 1H), 7.72−7.69 (m, 2H), 7.67−7.63 (m,
1H), 7.60−7.54 (m, 2H), 7.47−7.44 (m, 2H), 7.38−7.32 (m, 5H). 13C
NMR (100 MHz, CDCl3): δ 196.3, 152.3, 150.7, 139.6, 137.2, 136.6,
132.0, 131.4, 131.4, 131.1, 129.4, 129.1, 123.3, 121.0. IR (KBr): 3442,
3142, 2920, 2851, 1663, 1585, 1399, 1287, 1252, 1091, 1014, 931, 846,
775, 745, 692, 549 cm−1. HRMS (ESI) Calcd For C19H13ClN2O: [M +
H]+, 321.0789, Found: 321.0790.
(E)-(2-(Phenyldiazenyl)phenyl)(m-tolyl)methanone 3aj: red
(E)-(4-Bromophenyl)(2-(phenyldiazenyl)phenyl)methanone
1
1
3ac: red solid (60 mg, 83%), mp 99−100 °C; H NMR (400 MHz,
oil (53 mg, 89%); H NMR (400 MHz, CDCl3): δ 7.94 (d, J = 8.0
CDCl3): δ 7.96 (d, J = 7.5 Hz, 1H), 7.68−7.66 (m, 1H), 7.65−7.64
(m, 1H), 7.63−7.62 (m, 1H), 7.59−7.54 (m, 2H), 7.52−7.50 (m, 2H),
7.47−7.45 (m, 2H), 7.39−7.36 (m, 3H). 13C NMR (100 MHz,
CDCl3): δ 196.4, 152.3, 150.7, 137.7, 136.5, 132.1, 132.0, 131.5, 131.4,
131.3, 131.2, 129.5, 129.4, 129.4, 129.4, 129.1, 128.3, 123.3, 121.0. IR
(KBr): 3433, 3135, 2923, 2851, 1668, 1584, 1397, 1286, 1256, 1067,
1011, 929, 844, 760, 692, 639, 548, 533 cm−1. HRMS (ESI) Calcd For
C19H13BrN2O: [M + H]+, 365.0284, Found: 365.0286.
(E)-(2-Chlorophenyl)(2-(phenyldiazenyl)phenyl)methanone
3ad: red oil (38 mg, 59%); 1H NMR (400 MHz, CDCl3): δ 7,83 (d, J
= 7.6 Hz, 1H), 7.74 (d, J = 7.9 Hz, 1H), 7.67−7.64 (m, 1H), 7.61−
7.57 (m, 1H), 7.55−7.53 (m, 1H), 7.41−7.37 (m. 3H), 7.35−7.29 (m,
4H), 7.27−7.23 (m, 1H). 13C NMR (100 MHz, CDCl3): δ 195.9,
152.2, 151.0, 139.9, 137.0, 132.4, 132.2, 131.8, 131.5, 130.9, 130.7,
130.6, 130.0, 128.8, 126.6, 123.2, 117.7. IR (KBr): 3441, 3134, 2920,
2851, 1742, 1671, 1470, 1435, 1401, 1300, 1240, 1150, 1059, 1038,
930, 774, 743, 687, 630, 551 cm−1. HRMS (ESI) Calcd For
C19H13ClN2O: [M + H]+, 321.0789, Found: 321.0790.
Hz, 1H), 7.66−7.62 (m, 2H), 7.58 (d, J = 4.2 Hz, 2H), 7.53 (d, J = 7.5
Hz, 1H), 7.47 (dd, J = 4.8 Hz, J = 1.3 Hz, 2H), 7.37−7.33 (m, 3H),
7.29−7.23 (m, 2H), 2.33 (s, 3H). 13C NMR (100 MHz, CDCl3): δ
197.8, 152.5, 150.8, 138.9, 138.5, 137.6, 134.0, 131.7, 131.2, 131.1,
130.2, 129.3, 129.2, 128.6, 127.3, 123.3, 120.3, 21.6. IR (KBr): 3441,
3133, 2919, 2851, 1742, 1667, 1602, 1586, 1401, 1294, 1258, 961, 775,
724, 686, 636 cm−1. HRMS (ESI) Calcd For C20H16N2O: [M + Na]+,
323.1155, Found: 323.1158.
(E)-(2-(Phenyldiazenyl)phenyl)(p-tolyl)methanone 3ak: red
1
oil (43 mg, 72%); H NMR (400 MHz, CDCl3): δ 7.94 (d, J = 7.8
Hz, 1H), 7.68 (d, J = 8.1 Hz, 2H), 7.66−7.61 (m, 1H), 7.59−7.56 (m,
2H), 7.49−7.47 (m, 2H), 7.37−7.31 (m, 3H), 7.17 (d, J = 8.0 Hz,
2H), 2.36 (s, 3H). 13C NMR (100 MHz, CDCl3): δ 197.2, 152.5,
150.7, 144.0, 137.8, 136.3, 131.7, 131.2, 131.0, 130.0, 129.5, 129.3,
129.0, 123.3, 120.1, 22.1. IR (KBr): 3442, 3133, 2920, 2851, 2360,
1743, 1664, 1606, 1401, 1312, 1295, 1252, 1181, 1147, 930, 837, 774,
732, 688, 605 cm−1. HRMS (ESI) Calcd For C20H16N2O: [M + Na]+,
323.1155, Found: 323.1159.
(E)-(2-Bromophenyl)(2-(phenyldiazenyl)phenyl)methanone
3ae: red oil (44 mg, 61%); 1H NMR (400 MHz, CDCl3): δ 7.85 (dd, J
= 7.6 Hz, J = 1.1 Hz, 1H), 7.73−7.71 (m, 1H), 7.68−7.64 (m, 1H),
7.61−7.57 (m, 1H), 7.54−7.51 (m, 1H), 7.47 (dd, J = 7.7 Hz, J = 1.7
Hz, 1H), 7.43−7.27 (m, 6H), 7.22−7.17 (m, 1H). 13C NMR (100
MHz, CDCl3): δ 196.5, 152.3, 151.2, 141.8, 136.5, 133.9, 132.6, 131.7,
131.5, 130.8, 130.8, 130.4, 128.8, 127.2, 123.3, 120.4, 117.5. IR (KBr):
3435, 3135, 2919, 2851, 1741, 1671, 1587, 1432, 1401, 1299, 1240,
930, 774, 687, 629 cm−1. HRMS (ESI) Calcd For C19H13BrN2O: [M +
H]+, 365.0284, Found: 365.0286.
(E)-(3-Methyl-2-(o-tolyldiazenyl)phenyl)(phenyl)methanone
1
3ba: red solid (53 mg, 85%), mp 75−76 °C; H NMR (400 MHz,
CDCl3): δ 7.65 (d, J = 7.7 Hz, 2H), 7.49−7.41 (m, 2H), 7.37 (t, J =
14.7 Hz, 1H), 7.32−7.21 (m, 5H), 7.15 (d, J = 7.4 Hz, 1H), 7.08 (t, J =
15.2 Hz, 1H), 2.77 (s, 3H), 2.28 (s, 3H). 13C NMR (100 MHz,
CDCl3): δ 197.0, 150.6, 150.5, 139.4, 138.5, 134.6, 132.9, 132.9, 131.7,
131.6, 130.3, 129.4, 128.6, 126.9, 126.4, 126.0, 116.0, 18.8, 17.7. IR
(KBr): 3435, 3150, 2920, 2851, 1665, 1597, 1401, 1316, 1280, 1156,
774, 712, 693, 678, 651 cm−1. HRMS (ESI) Calcd For C21H18N2O:
[M + H]+, 315.1482, Found: 315.1496.
(E)-(4-Nitrophenyl)(2-(phenyldiazenyl)phenyl)methanone
(E)-(4-Methyl-2-(m-tolyldiazenyl)phenyl)(phenyl)methanone
1
1
3af: red solid (30 mg, 45%), mp 110−111 °C; H NMR (400 MHz,
3ca: red solid (54 mg, 86%), mp 86−87 °C; H NMR (400 MHz,
CDCl3): δ 8.90 (d, J = 8.8 Hz, 2H), 8.00 (d, J = 8.0 Hz, 1H), 7.90 (d, J
= 8.8 Hz, 2H), 7.76−7.72 (m, 1H), 7.67−7.60 (m, 2H), 7.42−7.31 (m,
5H). 13C NMR (100 MHz, CDCl3): δ 195.5, 151.7, 150.8, 150.1,
143.5, 134.7, 132.2, 132.2, 131.5, 130.1, 129.3, 129.2, 123.9, 123.0,
122.4. IR (KBr): 3442, 3134, 2922, 2852, 2360, 2341, 1743, 1661,
1603, 1592, 1522, 1401, 1344, 1291, 1244, 1014, 832, 861, 778, 710,
683, 668 cm−1. HRMS (ESI) Calcd For C19H13N3O3: [M + H]+,
332.1030, Found: 332.1029.
CDCl3): δ 7.56 (d, J = 7.7 Hz, 1H), 7.54−7.47 (m, 1H), 7.40−7.37
(m, 3H), 7.30−7.28 (m, 1H), 7.24−7.18 (m, 2H), 7.14 (s, 1H), 2.55
(s, 3H), 2.31 (s, 3H). 13C NMR (100 MHz, CDCl3): δ 197.8, 152.7,
150.9, 141.9, 139.7, 139.1, 134.8, 132.9, 132.4, 131.9, 129.8, 129.5,
129.1, 128.6, 123.0, 121.3, 120.0, 21.9, 21.6. IR (KBr): 3434, 3134,
2923, 2853, 1742, 1655, 1603, 1578, 1447, 1401, 1315, 1289, 1254,
1155, 905, 832, 802, 751, 709, 688, 614 cm−1. HRMS (ESI) Calcd For
C21H18N2O: [M + H]+, 315.1492, Found: 315.1496.
2959
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The Journal of Organic Chemistry
Article
(E)-(2-((3,5-Dimethylphenyl)diazenyl)-4,6-dimethylphenyl)-
(phenyl)methanone 3da: red solid (55 mg, 81%), mp 106−107 °C;
1H NMR (400 MHz, CDCl3): δ 7.81−7.79 (m, 2H), 7.56 (s, 1H),
Hz, 1H), 7.23−7.21 (m, 1H). 13C NMR (100 MHz, CDCl3): δ 196.3,
153.0, 150.7, 138.7, 137.0, 134.7, 134.4, 133.5, 130.8, 130.6, 129.6,
128.8, 125.7, 124.8, 123.8, 123.3, 121.7. IR (KBr): 3435, 3135, 2925,
2853, 1662, 1579, 1400, 1284, 1238, 924, 87, 833, 785, 743, 707, 675,
600 cm−1. HRMS (ESI) Calcd For C19H12Br2N2O: [M + H]+,
442.9389, Found: 442.9384.
(E)-(5-Bromo-2-((4-bromophenyl)diazenyl)phenyl)(phenyl)-
methanone 3ka: red solid (60 mg, 68%), mp 158−159 °C; 1H NMR
(400 MHz, CDCl3): δ 7.83−7.81 (m, 1H), 7.78−7.72 (m, 4H), 7.51
(t, J = 7.3 Hz, 2H), 7.45 (d, J = 8.6 Hz, 2H), 7.39 (t, J = 7.6 Hz, 2H),
7.28 (d, J = 8.7 Hz, 2H). 13C NMR (100 MHz, CDCl3): δ 195.5,
150.9, 149.0, 138.9, 138.1, 134.3, 133.5, 132.6, 132.0, 129.7, 128.8,
126.6, 126.0, 124.6, 121.5. IR (KBr): 3440, 3135, 2924, 2851, 1742,
1663, 1598, 1582, 1571, 1466, 1447, 1400, 1271, 1147, 1064, 1002,
949, 889, 710, 689, 614, 547 cm−1. HRMS (ESI) Calcd For
C19H12Br2N2O: [M + H]+, 442.9387, Found: 442.9389.
7.48 (d, J = 7.2 Hz, 1H), 7.38 (t, J = 7.5 Hz, 2H), 7.22 (s, 1H), 7.00 (d,
J = 12.0 Hz, 3H), 2.46 (s, 3H), 2.29 (s, 3H), 2.25 (s, 6H). 13C NMR
(100 MHz, CDCl3): δ 198.8, 152.6, 150.4, 140.0, 139.1, 138.7, 136.6,
135.4, 134.1, 133.1, 133.0, 129.3, 128.7, 120.9, 116.7, 21.6, 21.4, 19.2.
IR (KBr): 3432, 3149, 2922, 2854, 1742, 1665, 1609, 1449, 1401,
1318, 1268, 1158, 918, 856, 713, 689, 612, 598, 565 cm−1. HRMS
(ESI) Calcd For C23H22N2O: [M + H]+, 343.1805, Found: 343.1808.
(E)-(5-Methyl-2-(p-tolyldiazenyl)phenyl)(phenyl)methanone
1
3ea: red solid (48 mg, 76%), mp 90−91 °C; H NMR (400 MHz,
CDCl3): δ 7.85 (d, J = 8.2 Hz, 1H), 7.77−7.75 (m, 2H), 7.47−7.42
(m, 2H), 7.37−7.30 (m, 5H), 7.10 (d, J = 8.2 Hz, 2H), 2.43 (s, 3H),
2.33 (s, 3H). 13C NMR (100 MHz, CDCl3): δ 197.9, 150.6, 148.9,
142.1, 141.8, 139.0, 137.1, 133.0, 131.9, 129.9, 129.7, 129.6, 128.7,
123.2, 120.6, 21.8. IR (KBr): 3442, 3144, 2919, 2851, 1665, 1597,
1448, 1401, 1316, 1286, 1248, 1209, 1177, 1151, 963, 828, 752, 709,
646, 552, 531 cm−1. HRMS (ESI) Calcd For C21H18N2O: [M + H]+,
315.1492, Found: 315.1494.
(E)-Phenyl(5-(trifluoromethoxy)-2-((4-(trifluoromethoxy)-
phenyl)diazenyl)phenyl)methanone 3la: red solid (45 mg, 50%),
1
mp 96−98 °C; H NMR (400 MHz, CDCl3): δ 7.99 (d, J = 8.8 Hz,
1H), 7.77 (d, J = 7.4 Hz, 2H), 7.56−7.40 (m, 7H), 7.17 (d, J = 8.6 Hz,
2H). 13C NMR (100 MHz, CDCl3): δ 195.3, 151.6, 151.1, 150.2,
148.3, 139.3, 138.0, 133.6, 129.7, 128.8, 124.8, 123.0, 121.7, 121.3,
121.1. IR (KBr): 3435, 3129, 2929, 2854, 1668, 1599, 1497, 1479,
1451, 1401, 1278, 1254, 1213, 1167, 921, 899, 850, 749, 688, 657, 597
cm−1. HRMS (ESI) Calcd For C21H12F6N2O3: [M + H]+, 455.0825,
Found: 455.0824.
(E)-(4-Methoxy-2-((3-methoxyphenyl)diazenyl)phenyl)-
(phenyl)methanone 3fa: red solid (63 mg, 91%), mp 101−102 °C;
1H NMR (400 MHz, CDCl3): δ 7.79 (m, 2H), 7.64 (d, J = 8.4 Hz,
1H), 7.50−7.46 (m, 1H), 7.42−7.36 (m, 3H), 7.29 (d, J = 7.8 Hz,
1H), 7.22−7.15 (m. 2H), 6.97−6.94 (m, 1H), 6.79 (t, J = 2.0 Hz, 1H),
3.98 (s, 3H), 3.65 (s, 3H). 13C NMR (100 MHz, CDCl3): δ 197.2,
162.4, 160.5, 153.7, 152.2, 139.9, 132.9, 131.3, 131.1, 130.0, 129.9,
128.6, 119.3, 118.9, 118.1, 104.6, 102.1, 56.2, 55.7. IR (KBr): 3433,
3134, 3023, 2924, 2852, 1648, 1598, 1485, 1458, 1451, 1401, 1269,
1148, 1102, 1027, 785, 747, 711, 660, 622 cm−1. HRMS (ESI) Calcd
For C21H18N2O3: [M + H]+, 347.1390, Found: 347.1395.
(E)-(Diazene-1,2-diylbis(3-fluoro-6,1-phenylene))bis-
(phenylmethanone) 3m: yellow solid (58 mg, 68%), 160−162 °C;
1H NMR (400 MHz, CDCl3): δ 7.77−7.75 (m, 2H), 7.68−7.67 (m,
2H), 7.55−7.47 (m, 2H), 7.41−7.36 (m, 5H), 7.20−7.17 (m, 1H),
7.05−7.04 (m. 2H), 6.97−6.94 (m, 1H), 6.93−6.79 (m, 1H). 13C
NMR (100 MHz, CDCl3): δ 195.3, 194.5, 164.8 (d, JC−F = 252.8 Hz),
165.3, 163.2 (d, JC−F = 255.8 Hz), 162.8, 147.5 (d, JC−F = 3.1 Hz),
147.4, 146.1 (d, JC−F = 2.5 Hz), 140.5 (d, JC−F = 7.5 Hz), 137.9 (d, JC−F
= 6.7 Hz), 137.8, 137.1, 133.4, 133.3, 129.6, 129.2, 128.7, 128.5, 124.8
(d, JC−F = 9.2 Hz), 120.2 (d, JC−F = 9.1 Hz), 118.0 (d, JC−F = 23.0 Hz),
(E)-(5-Methoxy-2-((4-methoxyphenyl)diazenyl)phenyl)-
(phenyl)methanone 3ga: red solid (54 mg, 78%), mp 139−140 °C;
1H NMR (400 MHz, CDCl3): δ 7.93 (d, J = 8.8 Hz, 1H), 7.78 (d, J =
7.6 Hz, 2H), 7.47 (t, J = 14.6 Hz, 1H), 7.36 (t, J = 15.2 Hz, 4H), 7.13
(dd, J = 11.6 Hz, J = 2.7 Hz, 1H), 7.03 (d, J = 2.7 Hz, 1H), 6.79 (d, J =
8.9 Hz, 2H), 3.91 (s, 3H), 3.80 (s, 3H). 13C NMR (100 MHz,
CDCl3): δ 197.4, 162.1, 161.6, 146.7, 144.8, 138.7, 138.5, 132.9, 129.6,
128.6, 124.7, 122.2, 117.0, 114.2, 113.1, 56.1, 55.7. IR (KBr): 3444,
3161, 2964, 2934, 2837, 1665, 1599, 1580, 1499, 1480, 1440, 1413,
1318, 1290, 1224, 1179, 1143, 1107, 1026, 962, 846, 709, 558, 530
cm−1. HRMS (ESI) Calcd For C21H18N2O3: [M + H]+, 347.1390,
Found: 347.1395.
(E)-(5-Fluoro-2-((4-fluorophenyl)diazenyl)phenyl)(phenyl)-
methanone 3ha: red solid (35 mg, 54%), mp 110−111 °C; 1H NMR
(400 MHz, CDCl3): δ 7.99−7.95 (m, 1H), 7.78−7.76 (m, 2H), 7.50
(d, J = 7.4 Hz, 1H), 7.44−7.27 (m. 6H), 7.00 (t, J = 8.6 Hz, 2H). 13C
NMR (100 MHz, CDCl3): δ 195.7, 164.8 (d, JC−F = 251.5 Hz), 164.1
(d, JC−F = 253.2 Hz), 148.7 (d, JC−F = 2.9 Hz), 146.8 (d, JC−F = 3.2
Hz), 139.4 (d, JC−F = 7.1 Hz), 138.1, 133.4, 129.6, 128.8, 125.2 (d, JC−F
= 9.0 Hz), 122.3 (d, JC−F = 9.0 Hz), 118.1 (d, JC−F = 22.8 Hz), 116.2
(d, JC−F = 22.8 Hz), 116.0 (d, JC−F = 24.1 Hz). IR (KBr): 3431, 3128,
2923, 2852, 1658, 1598, 1402, 1279, 1229, 1134, 842, 753, 705, 557
cm−1. HRMS (ESI) Calcd For C19H12F2N2O: [M + H]+, 323.0990,
Found: 323.0990.
(E)-(5-Chloro-2-((4-chlorophenyl)diazenyl)phenyl)(phenyl)-
methanone 3ia: red solid (42 mg, 60%), mp 121−122 °C; 1H NMR
(400 MHz, CDCl3): δ 7.89 (d, J = 8.9 Hz, 1H), 7.77−7.74 (m, 2H),
7.61 (dd, J = 8.6 Hz, J = 2.1 Hz, 1H), 7.57−7.56 (d, J = 3.0 Hz, 1H),
7.53−7.52 (m, 1H), 7.41−7.34 (m, 4H), 7.31−7.28 (m, 2H). 13C
NMR (100 MHz, CDCl3): δ 195.6, 150.5, 148.7, 138.8, 138.1, 138.0,
137.7, 133.5, 131.2, 129.6, 129.5, 129.1, 128.8, 124.4, 121.4. IR (KBr):
3441, 3134, 2922, 2851, 1665, 1588, 1484, 1469, 1448, 1398, 1311,
1295, 1274, 1242, 1176, 1149, 1085, 1007, 965, 906, 836, 802, 765,
744, 715, 694, 650, 548, 529 cm−1. HRMS (ESI) Calcd For
C19H12Cl2N2O: [M + H]+, 355.0400, Found: 355.0404.
117.3 (d, JC−F = 24.0 Hz), 115.9 (d, JC−F = 22.9 Hz), 115.5 (d, JC−F
=
24.1 Hz). IR (KBr): 3434, 3135, 2925, 2855, 1742, 1664, 1595, 1580,
1499, 1478, 1450, 1401, 1317, 1281, 1236, 1204, 897, 886, 864, 845,
699, 646, 567 cm−1. HRMS (ESI) Calcd For C26H16F2N2O2: [M +
H]+, 427.1253, Found: 427.1259.
(E)-(Diazene-1,2-diylbis(2,1-phenylene))bis((4-
fluorophenyl)methanone) 3n: red solid (55 mg, 65%), mp 188−
1
190 °C; H NMR (400 MHz, CDCl3): δ 7.72−7.68 (m, 4H), 7.52−
7.42 (m, 6H), 7.21 (d, J = 8.6 Hz, 2H), 7.03 (t, J = 8.6 Hz, 4H). 13C
NMR (100 MHz, CDCl3): δ 195.4, 165.9 (d, JC−F = 253.6 Hz), 150.0,
137.9, 134.8 (d, JC−F = 2.9 Hz), 132.5 (d, JC−F = 9.4 Hz), 131.6, 131.1,
128.7, 118.9, 115.8 (d, JC−F = 21.8 Hz), 77.6, 77.3, 77.0. IR (KBr):
3432, 3144, 2924, 2853, 1741, 1662, 1594, 1503, 1402, 1299, 1247,
1232, 1222, 1152, 1143, 934, 851, 836, 773, 734, 692, 605, 587, 558
cm−1. HRMS (ESI) Calcd For C26H16F2N2O2: [M + H]+, 427.1253,
Found: 427.1255.
(E)-(Diazene-1,2-diylbis(2,1-phenylene))bis((4-
chlorophenyl)methanone) 3o: red solid (64 mg, 70%), mp 202−
1
205 °C; H NMR (400 MHz, CDCl3): δ 7.59 (d, J = 8.3 Hz, 4H),
7.53−7.43 (m, 6H), 7.32 (d, J = 8.4 Hz, 4H), 7.22 (d, J = 7.9 Hz, 2H).
13C NMR (100 MHz, CDCl3): δ 195.7, 150.0, 139.7, 137.4, 136.7,
131.6, 131.2, 128.9, 128.8, 119.3. IR (KBr): 3432, 3141, 2925, 2853,
1741, 1662, 1586, 1400, 1306, 1295, 1244, 1097, 1012, 931, 846, 769,
728, 679, 655, 566, 538 cm−1. HRMS (ESI) Calcd For
C26H16Cl2N2O2: [M + H]+, 459.0662, Found: 459.0662.
(E)-(Diazene-1,2-diylbis(3-fluoro-6,1-phenylene))bis(o-tolyl-
methanone) 3p: red solid (48 mg, 53%), mp 158−160 °C; 1H NMR
(400 MHz, CDCl3): δ 7.43 (d, J = 7.7 Hz, 2H), 7.23 (d, J = 8.0 Hz,
4H), 7.14 (d, J = 7.4 Hz, 2H), 7.05 (t, J = 7.4 Hz, 2H), 6.96−6.92 (m,
2H), 6.82 (t, J = 8.4 Hz, 2H), 2.56 (s, 6H). 13C NMR (100 MHz,
CDCl3): δ 196.4, 164.9 (d, JC−F = 252.2 Hz), 163.1 (d, JC−F = 254.8
Hz), 148.2, 145.6, 139.4, 138.7 (d, JC−F = 6.2 Hz), 137.0, 132.2, 132.1,
131.1, 125.9, 124.8 (d, JC−F = 9.1 Hz), 118.3 (d, JC−F = 23.8 Hz), 116.0
(d, JC−F = 22.9 Hz), 21.8. IR (KBr): 3433, 3135, 3072, 2927, 2854,
(E)-(4-Bromo-2-((3-bromophenyl)diazenyl)phenyl)(phenyl)-
methanone 3ja: red solid (49 mg, 55%), mp 128−130 °C; 1H NMR
(400 MHz, CDCl3): δ 8.04 (d, J = 1.8 Hz, 1H), 7.74 (dd, J = 4.8 Hz, J
= 1.4 Hz, 3H), 7.55−7.49 (m, 3H), 7.45−7.39 (m, 3H), 7.34 (t, J = 1.8
2960
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The Journal of Organic Chemistry
Article
1671, 1593, 1583, 1502, 1475, 1455, 1412, 1315, 1291, 1238, 1139,
1009, 885, 867, 843, 786, 746, 728, 648, 569, 560, 533 cm−1. HRMS
(ESI) Calcd For C28H20F2N2O2: [M + H]+, 455.1566, Found:
455.1563.
AUTHOR INFORMATION
■
Corresponding Authors
*cuixl@zzu.edu.cn
*wyj@zzu.edu.cn
(E)-(2-((2-(2-Methylbenzoyl)phenyl)diazenyl)-1,3-
1
phenylene)bis(o-tolylmethanone) 3q: red oil (80 mg, 75%); H
Notes
NMR (400 MHz, CDCl3): δ 7.56−7.54 (m, 2H), 7.51−7.49 (m, 1H),
7.34−7.32 (m, 1H), 7.24−7.13 (m, 7H), 7.04 (t, J = 7.0 Hz, 5H), 6.98
(t, J = 8.2 Hz, 2H), 6.58 (d, J = 8.0 Hz, 1H), 2.34 (s, 6H), 2.26 (s,
3H). 13C NMR (100 MHz, CDCl3): δ 197.5, 197.3, 150.2, 150.1,
140.2, 139.4, 139.3, 137.6, 137.3, 136.6, 132.6, 131.7, 131.6, 131.5,
131.3, 131.2, 130.6, 129.7, 128.3, 125.6, 125.4, 117.3, 21.5, 21.4. IR
(KBr): 3444, 3142, 2921, 2850, 1741, 1668, 1599, 1573, 1486, 1456,
1401, 1301, 1252, 1163, 1121, 1035, 1006, 928, 771, 731, 639, 561,
481 cm−1. HRMS (ESI) Calcd For C36H28N2O3: [M + H]+, 537.2173,
Found: 537.2175.
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was supported by NSF of China (21102133,
21172200), and the NSF of Henan (082300423201).
REFERENCES
■
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Samor, P.; Mayor, M.; Rampi, M. A. Angew. Chem., Int. Ed. 2008, 47,
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1873. (e) Berg, R. H.; Hvilsted, S.; Ramanujam, P. S. Nature 1996,
383, 505. (f) Puntoiero, F.; Geroni, P.; Balzani, V.; Begamini, G.;
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(E)-(2-((2-Benzoyl-4-methylphenyl)diazenyl)-5-methyl-1,3-
phenylene)bis(phenylmethanone) 3r: red solid (84 mg, 80%), mp
1
92−94 °C; H NMR (400 MHz, CDCl3): δ 7.60−7.58 (m, 4H),
7.45−7.36 (m, 6H), 7.31−7.27 (m, 7H), 7.02 (dd, J = 4.7 Hz, J = 1.2
Hz, 1H), 6.94−6.89 (m, 2H), 2.42 (s, 3H), 2.27 (s, 3H). 13C NMR
(100 MHz, CDCl3): δ 195.9, 195.7, 147.2, 146.3, 142.4, 141.8, 137.3,
137.0, 135.8, 133.1, 133.1, 131.0, 130.7, 130.1, 129.7, 128.8, 128.5,
128.3, 21.6. IR (KBr): 3432, 3135, 2924, 2854, 1673, 1656, 1595,
1579, 1449, 1400, 1323, 1261, 1210, 1178, 1141, 1035, 993, 959, 846,
762, 726, 703, 669, 650, 592, 557 cm−1. HRMS (ESI) Calcd For
C35H26N2O3: [M + H]+, 523.2016, Found: 523.2013.
(2) (a) Li, H. J.; Li, P. H.; Wang, L. Org. Lett. 2013, 15, 629. (b) Li,
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14432.
(E)-(5-Methoxy-2-((4-methoxy-2-(2-methylbenzoyl)phenyl)-
diazenyl)-1,3-phenylene)bis(o-tolylmethanone) 3s: yellow solid
1
(70 mg, 59%), mp 138−140 °C; H NMR (400 MHz, CDCl3): δ
7.24−7.16 (m, 5H), 7.06−6.95 (m, 9H), 6.67−6.64 (m, 3H), 3.85 (s,
3H), 3.74 (s, 3H), 2.38 (s, 6H), 2.24 (s, 3H). 13C NMR (100 MHz,
CDCl3): δ 197.3, 161.5, 160.6, 144.4, 143.3, 141.9, 139.7, 139.4, 138.9,
137.3, 136.7, 133.0, 131.7, 131.6, 125.5, 125.4, 119.7, 116.3, 115.7,
112.0, 56.3, 55.9, 21.7, 21.6. IR (KBr): 3434, 3146, 2923, 2853, 1742,
1670, 1591, 1573, 1457, 1401, 1330, 1291, 1252, 1225, 1149, 1035,
1012, 947, 874, 724, 652, 582 cm−1. HRMS (ESI) Calcd For
C38H32N2O5: [M + H]+, 597.2384, Found: 597.2384.
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(E)-(2-((2-Benzoyl-4-methoxyphenyl)diazenyl)-5-methoxy-
1,3-phenylene)bis(phenylmethanone) 3t: yellow solid (70 mg,
1
63%), 101−103 °C; H NMR (400 MHz, CDCl3): δ 7.62−7.60 (m,
4H), 7.49−7.39 (m, 5H), 7.33−7.26 (m, 6H), 7.00−6.96 (m, 3H),
6.71 (dd, J = 5.9 Hz, J = 2.7 Hz, 1H), 6.59 (d, J = 2.7 Hz, 1H), 3.85 (s,
3H). 13C NMR (100 MHz, CDCl3): δ 195.1, 195.0, 161.6, 160.9,
143.2, 141.9, 138.5, 137.5, 137.0, 136.5, 132.9, 132.9, 129.8, 129.5,
128.3, 128.1, 122.6, 115.8, 115.0, 112.5, 56.0, 55.7. IR (KBr): 3435,
3159, 3062, 2924, 2852, 1683, 1666, 1589, 1451, 1404, 1327, 1238,
1175, 1131, 1099, 1032, 1018, 964, 880, 850, 828, 761, 691, 626, 578
cm−1. HRMS (ESI) Calcd For C35H26N2O5: [M + H]+, 555.1914,
Found: 555.1919.
(E)-(5-Methoxy-2-((4-methoxy-2-(4-methylbenzoyl)phenyl)-
diazenyl)-1,3-phenylene)bis(p-tolylmethanone) 3u: red solid
1
(86 mg, 72%), 84−86 °C; H NMR (400 MHz, CDCl3): δ 7.51 (d,
J = 8.1 Hz, 4H), 7.31 (d, J = 8.1 Hz, 2H), 7.10−7.03 (m, 7H), 6.90 (s,
2H), 6.71 (dd, J = 5.9 Hz, J = 2.6 Hz, 1H), 6.57 (d, J = 4.0 Hz, 1H),
3.82 (s, 3H), 3.71 (s, 3H), 2.38 (s, 3H), 2.35 (s, 6H). 13C NMR (100
MHz, CDCl3): δ 195.2, 194.9, 161.7, 161.0, 143.9, 143.8, 143.5, 141.9,
139.3, 138.0, 134.7, 134.4, 130.3, 129.9, 129.2, 128.9, 122.6, 116.0,
114.9, 112.5, 56.2, 55.9, 22.1, 22.0. IR (KBr): 3441, 3141, 2923, 2853,
1741, 1667, 1605, 1590, 1402, 1332, 1291, 1231, 1175, 1131, 1029,
965, 840, 780, 721, 675, 805, 571 cm−1. HRMS (ESI) Calcd For
C38H32N2O5: [M + H]+, 597.2384, Found: 597.2384.
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ASSOCIATED CONTENT
■
S
* Supporting Information
Typical experimental procedure, characterization for all
products, and crystallographic information for 3o. This material
is available free of charge via the Internet at http://pubs.acs.org.
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