Synthesis and characterization of bis- N -2-Aryl Triazole as a fluorophore

Article abstract of DOI:10.1021/acs.joc.5b00006

Naphthalene-bridged bis-triazole (NBT) complexes were prepared and characterized for investigation of their photophysical properties. Unlike our previously reported N-2-aryl triazoles, which gave strong emissions through the planar intramolecular charge transfer mechanism (coplanar conformation), this newly developed NBT adopted a noncoplanar conformation between triazole and naphthalene, achieving fluorescence through twisted intramolecular charge transfer.

Full text of DOI:10.1021/acs.joc.5b00006

Note
pubs.acs.org/joc
Synthesis and Characterization of Bis‑N‑2-Aryl Triazole as a
Fluorophore
†
†
†
,‡
,†
Yanwei Zhang, Xiaohan Ye, Jeffery. L. Petersen, Minyong Li,* and Xiaodong Shi*
†
C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown, West Virginia 26506, United States
Department of Medicinal Chemistry, Key Laboratory of Chemical Biology (MOE), School of Pharmacy, Shandong University, Jinan,
‡
Shandong 250012, China
*
S Supporting Information
ABSTRACT: Naphthalene-bridged bis-triazole (NBT) com-
plexes were prepared and characterized for investigation of
their photophysical properties. Unlike our previously reported
N-2-aryl triazoles, which gave strong emissions through the
planar intramolecular charge transfer mechanism (coplanar
conformation), this newly developed NBT adopted a non-
coplanar conformation between triazole and naphthalene,
achieving fluorescence through twisted intramolecular charge
transfer.
mall organic molecules that can provide strong fluores-
(Scheme 1B), suggesting twisted intramolecular charge transfer
(TICT) is a plausible mechanism for the observed strong
fluorescence emission.
S
cence emissions are of great importance to the scientific
1
4
community. These molecular fluorophores have been applied
to a wide range of research areas, including chemistry, biology,
We have previously reported that N-2-aryl triazole 1a gave
very strong fluorescence emission, whereas its N-1 isomer 1b
gave no emission at all. Two key factors appeared to control the
fluorescence emission in these NAT dyes: N-2 substitution and
coplanar conformation between the two rings. However, the
second assumption was greatly challenged by our recent studies
of N-naphthalene triazoles. As shown in Figure 1, we recently
prepared N-naphthalene triazole 1c (N-2 isomer) and 1d (N-1
2
and material science. In 2011, our group reported N-2-aryl-
1
,2,3-triazoles (NAT) as novel fluorophores with strong
3
emission in the high-energy UV/blue region. The exper-
imental results (X-ray structures) and computational studies
confirmed the coplanar conformation (observed in N-2
isomers, Scheme 1A) as the key factor for fluorescence
Scheme 1. N-2-Aryl Triazole Fluorophores
emission. On the basis of these studies, planar intramolecular
charge transfer (PICT) was proposed as a plausible mechanism
for the observed excellent optical properties of this novel NAT
system. Herein, we report the design and synthesis of
naphthalene-bridged bis-triazole (NBT) compounds, which
give excellent fluorescence emissions, even with a twisted
conformation between triazole and the N-2 aryl groups
Figure 1. Fluorescence emission of NAT with different aryl groups.
Received: January 2, 2015
Published: March 12, 2015
©
2015 American Chemical Society
3664
DOI: 10.1021/acs.joc.5b00006
J. Org. Chem. 2015, 80, 3664−3669

The Journal of Organic Chemistry
Note
isomer). Similar to phenyl triazoles, N-1 isomer 1d gave no
fluorescence emission, and the N-2 isomer 1c gave strong
emission. However, a closer look at 1c suggests that coplanar
conformation between naphthalene and the triazole ring is
highly unlikely due to steric repulsion. In fact, the crystal
structure of a similar analogue indicated a 49.5° dihedral angle
difference. Perhaps the most important question for the
synthesis of NBT was how to identify the relative position of
the two triazole rings with restricted rotation. Considering the
rotation of C−N bonds, theoretically two conformers (cis and
trans) could be formed. Interestingly, during our synthesis, only
one conformer was observed in almost all cases, which was later
confirmed as the cis-conformer via X-ray crystallography
5
between the two rings in the N-2 isomer. These results piqued
our interest in further exploring this new class of dyes by
(
Figure 3).
6
questioning whether the coplanar conformation is necessary.
Besides coplanar intramolecular charge transfer (PICT),
another feasible photochemical process associated with this
type of extended aromatic ring, twisted intramolecular charge
transfer (TICT), was first introduced by Grabowski and co-
7
workers. One important feature of the TICT type of emission
is the feasibility of the donor unit in initiating the charge
transfer. A number of nitrogen-containing heterocycles have
been studied as donors in TICT-emitting molecules. However,
to the best of our knowledge, 1,2,3-triazoles have never been
used as a potential donor in TICT fluorophores, and their
photochemical properties are unknown.
To explore triazole derivatives as potential TICT-emitting
dyes, we prepared anthracene-substituted triazole 1e (N-2) and
8
Figure 3. X-ray crystallography confirmed the formation of the cis-
conformer.
As shown in the X-ray crystal structure, the twisted
conformation was confirmed between the triazole and
naphthalene rings with a dihedral angle of 61.5°. The crystal
structure of mono-triazole-substituted 4a (Ar1 = Ph, with I on
naphthalene ring) was also obtained (see the Supporting
Information (SI)). Similarly, according to this crystal structure,
the dihedral angle between these two rings is 62.9°. With all of
the NBTs clearly characterized, their fluorescent properties
were measured and shown in Figure 4.
1
f (N-1). Clearly, the anthracene should provide a large enough
steric repulsion to prevent formation of the coplanar
conformation even in the N-2 isomer 1e. Thus, the
fluorescence emission should be mainly from the twisted
state. Interestingly, both N-1 and N-2 isomers gave good
emissions. However, three different emission bands were
observed in N-1 isomer 1f, which was similar to the typical
9
emission of aromatic-substituted anthracene. This result
suggested that triazole-anthracene compounds were not good
model molecules to access the triazole’s influence on TICT
emission due to the notable background emission from
anthracene. To better evaluate the triazole influence in the
twisted systems, we designed naphthalene-bridged bis-triazole
(
NBT).
As shown in Figure 2, bis-triazole can be readily prepared
from copper-catalyzed coupling between naphthalene di-iodide
Figure 4. Fluorescence emission of NBT 3 and 4a.
As shown by the crystal structures, both bis-triazole NBT 3
and mono-triazole 4 adopted a twisted conformation. However,
whereas N-2 isomers generally gave good fluorescence
emission, the N-1 isomers gave almost no emission in all
cases. The emission intensity of NBT 3 followed a clear trend
in that N2−N2 > N2−N1 > N1−N1 (almost no emission).
Because of the rotation strain, it is impossible for NBT 3 to
adopt planar conformation even in solution. Thus, the observed
good fluorescence emission of the N-2 isomers likely represents
the photochemical process associated with TICT states. The
optical properties (emission, excitation, and quantum yields) of
compounds 3 and 4 were determined and summarized in Table
1.
Figure 2. Synthesis of naphthalene-bridged bis-triazole (NBT).
2
b and NH-triazole. Two different conditions were developed
to reach NBT, either in a one-pot fashion (condition A) or a
5
stepwise process (condition B). Using these methods, both
symmetrical NBT 3 and unsymmetrical NBT 5 could be easily
prepared. Notably, both N-1 and N-2 isomers were observed in
all cases. The regioselectivity (ratio between N-2 and N-1
isomers) depends on the substituted groups (Ar) similar to
what has been observed previously in triazole functionaliza-
1
0
tion. The N-1 and N-2 isomers could be easily separated
These N-2 isomers of NBTs were identified as a new class of
fluorophores, and one interesting feature offered by the
using column chromatography due to the significant polarity
3
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DOI: 10.1021/acs.joc.5b00006
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The Journal of Organic Chemistry
Note
a
Table 1. Comparison of Optical Properties of Different NBTs
R1/R2
excitation (λmax
)
emission (λmax
)
Φ
Stokes shift (nm)
NAT
1
a
a
298
300
347
378
0.34
0.20
49
78
4
N2-TA-I
NBT
1
2
3a
3b
3c
5a
5b
5c
5d
5e
R = R = H (N1−N1)
<0.01
0.13
0.24
0.26
0.29
0.41
0.47
0.39
1
2
R = R = H (N1−N2)
307
315
305
315
300
302
300
384
393
393
403
396
403
408
77
78
1
2
R = R = H (N2−N2)
1
2
R = R = Cl
88
1
2
R = R = OMe
88
1
2
R = R = COOMe
96
1
2
R = R = CN
101
108
1
2
R = OMe, R = CN
a
Sample information: 1.0 × 10−6 mol/L in dichloromethane. Quantum yields (Φ) were determined based on 1.0 × 10−6 mol/L 9,10-
diphenylanthracene in cyclohexane (Φ = 0.9). Photo emission integration calculated from the original spectra. All fluorescence was measured under
identical conditions (see the SI).
naphthalene-bridge was the potential π-π stacking between the
(up to 47%) through the introduction of extended
conjugations. Overall, compared with NAT, this new NBT
system gave significantly higher fluorescence efficiency, which
implies great potential for future applications.
1
1
13
two triazoles. As revealed by the X-ray structures, the two
triazoles in NBT are almost parallel with a distance that is just
slightly longer than van der Waals radii (see the space filling
model in the SI). Thus, it is reasonable to expect that the
substituted groups on the triazole phenyl ring may provide
various electronic effects that will influence the overall optical
In conclusion, we report a new type of triazole-based
fluorescence-active compound: naphthalene-bridged bis-triazole
(NBT). Practical syntheses have been developed, and regio-
isomers of compounds have been characterized by X-ray
crystallography. The fluorescence studies reveal that in this
twisted system, N-2 substitution is crucial for fluorescence
emission. Compared to the previously reported NAT system,
this new NBT gives higher fluorescence efficiency and larger
Stokes shifts, which warrants the new molecule as a potential
fluorophore for chemical and biological applications.
3
,12
properties.
To explore the substituted group influence, we
prepared a series of symmetrical and unsymmetrical NBTs 5a−
e with various substituents on the triazole phenyl rings. Their
photochemical properties were evaluated (Table 1), and the
spectra of some representative NBTs are shown in Figure 5.
EXPERIMENTAL SECTION
■
General Information. All of the reactions dealing with air and/or
moisture-sensitive reactions were carried out under an atmosphere of
nitrogen using oven-dried glassware and standard syringe/septa
techniques. Unless otherwise noted, all commercial reagents and
solvents were obtained from commercial providers and used without
further purification. Chemical shifts were reported relative to internal
1
tetramethylsilane (δ 0.00 ppm) or CDCl (δ 7.26 ppm) for H NMR
3
1
3
and CDCl (δ 77.0 ppm) or d6-DMSO (δ 39.5 ppm) for C NMR.
3
Representative Procedure for the Preparation of 2-
(
Anthracen-9-yl)-4-phenyl-2H-1,2,3-triazole (1e) (Condition
A). To a solution of 9-bromoanthracene (514 mg, 2.0 mmol, 1.0
equiv) in dry DMSO (4 mL, 0.5 M) were successively added 4-phenyl-
1
,2,3-NH-triazole (725 mg, 5.0 mmol, 2.5 equiv), CuI (76 mg, 20%),
L-proline (92 mg, 40%), and K CO (1.1 g, 8.0 mmol, 4.0 equiv) under
2
3
Figure 5. Fluorescence emission of NBT 5 and 4a.
a N atmosphere. The mixture was stirred at 120 °C and monitored by
2
TLC. After the reaction was completed, it was quenched with brine
and extracted with ethyl acetate three times. The organic phases were
combined, and the solvent was removed under vacuum. The residue
was purified by flash silica gel chromatography (hexane/EtOAc v/v
Among all the tested NBTs, N-2 substitution is crucial for
effective emission. Compared with previous planar NAT 1a, the
new twisted NBT fluorophores give more red shifted emissions
around 400 nm (blue light). Interestingly, although the two
triazole rings are almost parallel, changing the substituent
groups on the phenyl rings did not influence the overall
emission of the NBT. For example, with either EDG (5b)- or
EWG (5c and 5d)-substituted NBT, there were little changes in
the emission and excitation wavelengths. Furthermore,
substrate 5e, with EDG and EWG incorporated on different
rings, also gave similar emission, which strongly suggested that
little π-π interactions occurred between the two rings. Notably,
the substituent group did help to improve the quantum yields
20:1), giving the desired product as a yellow solid (yield: 340 mg,
1
53%). H NMR (400 MHz, CDCl ): δ 8.66 (s, 1H), 8.37 (s, 1H), 8.32
3
(dd, J = 5.8, 3.3 Hz, 1H), 8.09 (dd, J = 7.1, 1.9 Hz, 2H), 8.00−7.98 (m,
1
3
2
(
H), 7.79 (dd, J = 5.8, 3.3 Hz, 1H), 7.51−7.44 (m, 7H). C NMR
100 MHz, CDCl ): δ 148.94, 134.1, 132.5, 131.3, 129.5, 129.00,
3
1
28.85, 128.70, 128.2, 127.6, 127.2, 126.2, 125.7, 122.6. HRMS: [M +
+
H] calcd for C H N , 322.1338; found, 322.1342.
22
15
3
Representative Procedure for the Preparation of 1-
Anthracen-9-yl)-4-phenyl-1H-1,2,3-triazole (1f) (Condition A).
(
To a solution of 9-bromoanthracene (514 mg, 2.0 mmol, 1.0 equiv) in
dry DMSO (4 mL, 0.5 M) were successively added 4-phenyl-1,2,3-
NH-triazole (725 mg, 5.0 mmol, 2.5 equiv), CuI (76 mg, 20%), L-
3
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DOI: 10.1021/acs.joc.5b00006
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The Journal of Organic Chemistry
Note
proline (92 mg, 40%), and K CO (1.1 g, 8.0 mmol, 4.0 equiv) under a
(8-azidonaphthalen-1-yl)-4-phenyl-2H-1,2,3-triazole was prepared
from 1-azido-8-iodonaphthalene under condition B. Then, to a
solution of 2-(8-azidonaphthalen-1-yl)-4-phenyl-2H-1,2,3-triazole
2
3
N atmosphere. The mixture was stirred at 120 °C and monitored by
2
TLC. After the reaction was completed, it was quenched with brine
and extracted with ethyl acetate three times. The organic phases were
combined, and the solvent was removed under vacuum. The residue
was purified by flash silica gel chromatography (hexane/EtOAc v/v
(624 mg, 2.0 mmol, 1.0 equiv) in 1:1 t-BuOH/H O (5 mL, 0.4 M)
2
were successively added phenylacetylene (510 mg, 5.0 mmol, 2.5
equiv), CuSO (64 mg, 20%), and L-ascorbic acid sodium salt (118.8
4
1
3
5:1), giving the desired product as a light yellow solid (yield: 237 mg,
mg, 30%) under a N atmosphere. The mixture was stirred at 120 °C
2
1
7%). H NMR (400 MHz, CDCl ): δ 8.69 (s, 1H), 8.20 (s, 1H), 8.11
and monitored by TLC. After the reaction was completed, it was
quenched with brine and extracted with ethyl acetate three times. The
organic phases were combined, and the solvent was removed under
vacuum. The residue was purified by flash silica gel chromatography
3
(
7
1
d, J = 7.6 Hz, 2H), 8.03 (d, J = 8.4 Hz, 2H), 7.55−7.51 (m, 5H),
13
.43−7.40 (m, 2H). C NMR (100 MHz, CDCl ): δ 147.8, 131.2,
3
30.3, 129.8, 129.0, 128.46, 128.35, 128.0, 127.4, 126.7, 125.97,
+
125.89, 124.0, 122.1. HRMS: [M + H] calcd for C H N , 322.1338;
(hexane/EtOAc v/v 3:1), giving the desired product as a light yellow
22
15
3
1
found, 322.1342.
solid (yield: 605 mg, 73%). H NMR (400 MHz, CDCl ): δ 8.17 (dd,
3
Representative Procedure for the Preparation of 1,8-Bis(4-
phenyl-2H-1,2,3-triazol-2-yl)naphthalene (3c) (Condition A).
To a solution of 1,8-diiodonaphthalene (760 mg, 2.0 mmol, 1.0 equiv)
in dry DMSO (4 mL, 0.5 M) were successively added 4-phenyl-1,2,3-
NH-triazole (725 mg, 5.0 mmol, 2.5 equiv), CuI (76 mg, 20%), L-
proline (92 mg, 40%), and K CO (1.1 g, 8.0 mmol, 4.0 equiv) under a
J = 7.5, 5.2 Hz, 2H), 7.84 (d, J = 7.2 Hz, 1H), 7.79 (d, J = 7.1 Hz, 1H),
7.72 (t, J = 7.8 Hz, 2H), 7.63 (s, 1H), 7.52 (s, 1H), 7.45 (ddd, J = 12.2,
6.4, 2.7 Hz, 4H), 7.26−7.24 (t, J = 3.0 Hz 3H), 7.18 (t, J = 2.8 Hz,
3H). 13C NMR (100 MHz, CDCl ): δ 149.0, 146.9, 135.8, 135.0,
3
132.4, 132.0, 131.1, 130.8, 129.7, 129.1, 128.52, 128.48, 128.38,
2
3
128.25, 128.08, 127.7, 126.16, 126.12, 126.04, 125.5, 122.3, 121.6,
+
N atmosphere. The mixture was stirred at 120 °C and monitored by
2
116.0. HRMS: [M + H] calcd for C H N , 415.1665; found,
26 18
6
TLC. After the reaction was completed, it was quenched with brine
and extracted with ethyl acetate three times. The organic phases were
combined, and the solvent was removed under vacuum. The residue
was purified by flash silica gel chromatography (hexane/EtOAc v/v
415.1672.
Representative Procedure for the Preparation of 1,8-Bis(4-
(4-chlorophenyl)-2H-1,2,3-triazol-2-yl)naphthalene (5a) (Con-
dition A). To a solution of 1,8-diiodonaphthalene (760 mg, 2.0 mmol,
1.0 equiv) in dry DMSO (4 mL, 0.5 M) were successively added 4-(4-
chlorophenyl)-1,2,3-NH-triazole (898 mg, 5.0 mmol, 2.5 equiv), CuI
(76 mg, 20%), L-proline (92 mg, 40%), and K
4.0 equiv) under a N atmosphere. The mixture was stirred at 120 °C
and monitored by TLC. After the reaction was completed, it was
quenched with brine and extracted with ethyl acetate three times. The
organic phases were combined, and the solvent was removed under
vacuum. The residue was purified by flash silica gel chromatography
(hexane/EtOAc v/v 5:1), giving the desired product as a light yellow
5
5
7
7
1
1
4
:1), giving the desired product as a light yellow solid (yield: 472 mg,
1
7%). H NMR (400 MHz, CDCl ): δ 8.12 (dd, J = 8.4, 1.2 Hz, 2H),
3
.96 (dd, J = 7.4, 1.2 Hz, 2H), 7.71 (dd, J = 8.2, 7.4 Hz, 2H), 7.48−
2 3
CO (1.1 g, 8.0 mmol,
1
3
.51 (m, 4H), 7.28−7.22 (m, 6H). C NMR (100 MHz, CDCl ): δ
2
3
48.3, 136.1, 135.6, 131.7, 130.2, 129.4, 128.5, 128.3, 127.0, 125.9,
21.1. HRMS: [M + H] calcd for C H N , 415.1666; found,
+
26
18
6
15,1672.
Representative Procedure for the Preparation of 2-(8-
Iodonaphthalen-1-yl)-4-phenyl-2H-1,2,3-triazole (4a) (Condi-
tion B). To a solution of 1,8-diiodonaphthalene (760 mg, 2.0 mmol,
1
3
solid (yield: 580 mg, 60%). H NMR (400 MHz, CDCl ): δ 8.14 (dd,
J = 8.4, 1.1 Hz, 2H), 7.95 (dd, J = 7.4, 1.2 Hz, 2H), 7.72 (dd, J = 8.1,
7.6 Hz, 2H), 7.56 (s, 2H), 7.42−7.39 (m, 4H), 7.24−7.22 (m, 4H).
1
.0 equiv) in dry DMSO (4 mL, 0.5 M) were successively added 4-
phenyl-1,2,3-NH-triazole (290 mg, 2.0 mmol, 1.0 equiv), CuI (38 mg,
0%), L-proline (46 mg, 20%), and K CO (552 mg, 4.0 mmol, 2.0
13
1
C NMR (100 MHz, CDCl ): δ 147.1, 136.0, 135.3, 134.3, 131.44,
2
3
3
equiv) under a N atmosphere. The mixture was stirred at 80 °C and
2
131.41, 130.4, 128.7, 127.8, 127.07, 127.00, 126.0, 121.0. HRMS: [M +
+
monitored by TLC. After the reaction was completed, it was quenched
with brine and extracted with ethyl acetate three times. The organic
phases were combined, and the solvent was removed under vacuum.
The residue was purified by flash silica gel chromatography (hexane/
H] calcd for C H N Cl , 483.0887; found, 483.0897.
26
16
6
2
Representative Procedure for the Preparation of 1,8-Bis(4-
(4-methoxyphenyl)-2H-1,2,3-triazol-2-yl)naphthalene (5b)
(Condition A). To a solution of 1,8-diiodonaphthalene (760 mg,
2.0 mmol, 1.0 equiv) in dry DMSO (4 mL, 0.5 M) were successively
added 4-(4-methoxyphenyl)-1,2,3-NH-triazole (875 mg, 5.0 mmol, 2.5
equiv), CuI (76 mg, 20%), L-proline (92 mg, 40%), and K CO (1.1 g,
EtOAc v/v 10:1), giving the desired product as a light yellow solid
1
(
yield: 401 mg, 51%). H NMR (400 MHz, CDCl ): δ 8.29 (dd, J =
3
7
.4, 1.2 Hz, 1H), 8.21 (s, 1H), 8.04 (dd, J = 8.3, 1.3 Hz, 1H), 7.97 (dd,
J = 8.3, 1.1 Hz, 1H), 7.94−7.91 (m, 2H), 7.68 (dd, J = 7.2, 1.6 Hz,
H), 7.59 (dd, J = 8.1, 7.3 Hz, 1H), 7.49−7.45 (m, 2H), 7.42−7.38
2
3
8.0 mmol, 4.0 equiv) under a N atmosphere. The mixture was stirred
2
1
at 120 °C and monitored by TLC. After the reaction was completed, it
was quenched with brine and extracted with ethyl acetate three times.
The organic phases were combined, and the solvent was removed
under vacuum. The residue was purified by flash silica gel
chromatography (hexane/EtOAc v/v 5:1), giving the desired product
13
(
m, 1H), 7.19 (dd, J = 8.1, 7.4 Hz, 1H). C NMR (100 MHz,
CDCl ): δ 149.1, 143.0, 137.2, 135.8, 132.6, 132.0, 130.1, 129.5, 129.1,
3
+
1
28.92, 128.75, 128.73, 127.4, 126.2, 125.2, 86.5. HRMS: [M + H]
calcd for C H N I, 398.0149; found, 398.0155.
18
22
3
1
Representative Procedure for the Preparation of 1,8-Bis(4-
phenyl-1H-1,2,3-triazol-1-yl)naphthalene (3a). To a solution of
as a light yellow solid (yield: 607 mg, 64%). H NMR (400 MHz,
CDCl ): δ 8.10 (dd, J = 8.4, 1.2 Hz, 2H), 7.94 (dd, J = 7.4, 1.2 Hz,
3
1,8-diazidonaphthalene (420 mg, 2.0 mmol, 1.0 equiv) in 1:1 t-BuOH/
2H), 7.69 (dd, J = 8.2, 7.4 Hz, 2H), 7.50 (s, 2H), 7.44−7.40 (m, 4H),
1
3
H O (5 mL, 0.4 M) were successively added phenylacetylene (1.02 g,
6.80−6.76 (m, 4H), 3.80 (s, 6H). C NMR (100 MHz, CDCl ): δ
2
3
1
0.0 mmol, 5.0 equiv), CuSO (128 mg, 40%), and L-ascorbic acid
159.6, 148.0, 136.0, 135.6, 131.1, 130.0, 127.2, 126.9, 125.9, 122.2,
4
+
sodium salt (237.6 mg, 60%) under a N atmosphere. The mixture was
121.2, 113.8, 55.1. HRMS: [M + H] calcd for C H N O , 475.1877;
2
28 22
6
2
stirred at 80 °C and monitored by TLC. After the reaction was
completed, it was quenched with brine and extracted with ethyl acetate
three times. The organic phases were combined, and the solvent was
removed under vacuum. The residue was purified by flash silica gel
chromatography (hexane/EtOAc v/v 5:1), giving the desired product
found, 475.1883.
Representative Procedure for the Preparation of Dimethyl
4,4′-(2,2′-(Naphthalene-1,8-diyl)bis(2H-1,2,3-triazole-4,2-
diyl))dibenzoate (5c) (Condition A). To a solution of 1,8-
diiodonaphthalene (760 mg, 2.0 mmol, 1.0 equiv) in dry DMSO (4
mL, 0.5 M) were successively added 4-(1H-1,2,3-triazole-4-yl)-benzoic
acid methyl ester (1.015 g, 5.0 mmol, 2.5 equiv), CuI (76 mg, 20%), L-
1
as a light yellow solid (yield: 712 mg, 86%). H NMR (400 MHz,
CDCl ): δ 8.25 (dd, J = 8.3, 1.2 Hz, 1H), 7.75 (t, J = 7.8 Hz, 1H), 7.66
3
(
(
dd, J = 7.6, 1.2 Hz, 1H), 7.56 (s, 1H), 7.47−7.43 (m, 2H), 7.25−7.21
proline (92 mg, 40%), and K
2 3
CO (1.1 g, 8.0 mmol, 4.0 equiv) under a
m, 3H). 13C NMR (100 MHz, d6-DMSO): δ 146.4, 135.7, 132.1,
N
atmosphere. The mixture was stirred at 120 °C and monitored by
2
1
31.7, 130.5, 129.4, 128.7, 128.0, 127.0, 125.8, 124.4. HRMS: [M +
TLC. After the reaction was completed, it was quenched with brine
and extracted with ethyl acetate three times. The organic phases were
combined, and the solvent was removed under vacuum. The residue
was purified by flash silica gel chromatography (hexane/EtOAc v/v
+
H] calcd for C H N , 415.1665; found, 415.1677.
26
18
6
Representative Procedure for the Preparation of 2,3′-
(Naphthalene-1,8-diyl)bis(5-phenyl-2H-1,2,3-triazole) (3b). 2-
3
667
DOI: 10.1021/acs.joc.5b00006
J. Org. Chem. 2015, 80, 3664−3669

The Journal of Organic Chemistry
Note
5
4
:1), giving the desired product as a light yellow solid (yield: 456 mg,
in cyclohexane. Quantum yields were calculated using the following
equation, where Φ is the quantum yield, Int is the area of the emission
peak, A represents absorbance at the excitation wavelength, and n is
the reflective index of the solvent. The subscript reference is the
respective values of the standard 9,10-diphenylanthracene. The
absorptions of bis-N-2-aryl triazole and 9,10-diphenylanthracene
1
3%). H NMR (400 MHz, CDCl ): δ 8.15 (d, J = 8.2 Hz, 2H), 7.96
3
(
7
d, J = 7.4 Hz, 2H), 7.86 (d, J = 8.2 Hz, 4H), 7.73 (t, J = 7.8 Hz, 2H),
.62 (s, 2H), 7.51 (d, J = 8.3 Hz, 4H), 3.91 (s, 6H). 13C NMR (100
MHz, CDCl ): δ 166.5, 147.2, 136.0, 135.2, 133.5, 132.01, 131.96,
3
1
30.5, 129.82, 129.69, 127.2, 126.0, 125.5, 121.0, 52.1. HRMS: [M +
+
−6
Na] calcd for C H N O , 553.1595; found, 553.1600.
were <0.05 (concentrations = 10 mol/L).
30
22
6
4
Representative Procedure for the Preparation of 4,4′-(2,2′-
Int × A
reference×n2
(
Naphthalene-1,8-diyl)bis(2H-1,2,3-triazole-4,2-diyl))-
ϕ = ϕreference
×
2
dibenzonitrile (5d) (Condition A). To a solution of 1,8-
diiodonaphthalene (760 mg, 2.0 mmol, 1.0 equiv) in dry DMSO (4
mL, 0.5 M) were successively added 4-(2H-1,2,3-triazol-4-yl)-
benzonitrile (850 mg, 5.0 mmol, 2.5 equiv), CuI (76 mg, 20%), L-
proline (92 mg, 40%), and K CO (1.1 g, 8.0 mmol, 4.0 equiv) under a
Int × A × n
reference
ASSOCIATED CONTENT
Supporting Information
Characterizations, NMR fluorescence spectra, X-ray data, and
other supporting figures. This material is available free of charge
via the Internet at http://pubs.acs.org.
■
2
3
*
S
N atmosphere. The mixture was stirred at 120 °C and monitored by
2
TLC. After the reaction was completed, it was quenched with brine
and extracted with ethyl acetate three times. The organic phases were
combined, and the solvent was removed under vacuum. The residue
was purified by flash silica gel chromatography (hexane/EtOAc v/v
AUTHOR INFORMATION
Corresponding Authors
*E-mail: mli@sdu.edu.cn.
*E-mail: Xiaodong.Shi@mail.wvu.edu.
5
4
(
7
1
:1), giving the desired product as a light yellow solid (yield: 389 mg,
■
1
2%). H NMR (400 MHz, CDCl ): δ 8.18 (d, J = 8.2 Hz, 2H), 7.97
3
d, J = 7.4 Hz, 2H), 7.76 (dd, J = 9.7, 6.0 Hz, 2H), 7.63 (s, 2H), 7.63−
.53 (m, 8H). 13C NMR (100 MHz, CDCl ): δ 146.3, 136.0, 135.0,
3
33.5, 132.4, 131.9, 130.7, 128.4, 127.1, 126.1, 120.7, 118.3, 112.0.
+
Notes
HRMS: [M + Na] calcd for C H N , 487.1390; found, 487.1396.
28
16
8
The authors declare no competing financial interest.
Representative Procedure for the Preparation of 5e
Conditions A and B). To a solution of 1,8-diiodonaphthalene
(
(
760 mg, 2.0 mmol, 1.0 equiv) in dry DMSO (4 mL, 0.5 M) were
successively added 4-(4-methoxyphenyl)-1,2,3-NH-triazole (350 mg,
.0 mmol, 1.0 equiv), CuI (38 mg, 10%), L-proline (46 mg, 20%),
K CO (552 mg, 4.0 mmol, 2.0 equiv) under a N atmosphere. The
ACKNOWLEDGMENTS
■
We thank the National Science Foundation (CHE-1362057
and CHE-1228336) and NSFC (21228204) for financial
support. We also acknowledge (CHE-1336071) which
provided funds for X-ray diffraction.
2
2
3
2
mixture was stirred at 80 °C and monitored by TLC. After the reaction
was completed, it was quenched with brine and extracted with ethyl
acetate three times. The organic phases were combined, and the
solvent was removed under vacuum. The residue was purified by flash
silica gel chromatography (hexane/EtOAc v/v 10:1), giving the
desired intermediate 2-(8-iodonaphthalen-1-yl)-4-(4-methoxyphenyl)-
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2
3
2
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13
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7
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1
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2
2
between 200 and 600 nm.
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2
2
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J. Org. Chem. 2015, 80, 3664−3669