Amidetriazole: A versatile building block for construction of oxyanion anion receptors

Article abstract of DOI:10.1002/chem.201102760

The design and synthesis of efficient receptors for tetrahedral oxyanions is an emerging field in supramolecular chemistry. Herein, we have developed a urea-like anion-recognizing motif, amidetriazole, which can be easily synthesized and derived and shows

Full text of DOI:10.1002/chem.201102760

DOI: 10.1002/chem.201102760
Amidetriazole: A Versatile Building Block for Construction of Oxyanion
Anion Receptors
Yong-Jun Li,*[a] Liang Xu,[a, b] Wen-Long Yang,[a, b] Hui-Biao Liu,[a] Siu-Wai Lai,[c]
Chi-Ming Che,[c] and Yu-Liang Li*[a]
Abstract: The design and synthesis of
efficient receptors for tetrahedral oxy-
anions is an emerging field in supra-
molecular chemistry. Herein, we have
developed a urea-like anion-recogniz-
ing motif, amidetriazole, which can be
easily synthesized and derived and
simple acyclic receptors were designed
and synthesized to confirm the poten-
tial of amidetriazole for the construc-
tion of tetrahedral oxyanion receptors.
This molecular platform can be used
extensively for the construction of nu-
merous receptor systems appended
with functional groups, which opens
the way to many applications in the
field of supramolecular chemistry.
Keywords: amidetriazoles · anions ·
click chemistry · host–guest sys-
tems · receptors
shows good solubility.
A series of
Introduction
struction of artificial receptors for tetrahedral anions. 1,2,3-
Triazoles with 5 Debye (D) dipole character are new motifs
that can participate in multiple noncovalent interactions (for
example, anion recognition[5] within flexible[6] and shape-per-
sistent triazolophanes[7] and in foldamers)[8] and they can
help facilitate self-assembly.[9] 1,2,3-Triazoles can serve as a
surrogate for amide bonds,[10] which motivated us to replace
one of the amide NH groups in the urea moiety with 1,2,3-
triazole to generate a versatile anion-receptor building
block that combines the characteristics of urea and triazole;
that is, amidetriazole (Figure 1b). This building block has
enormous advantages, such as ease of preparation, especially
for the construction of asymmetric molecules for functional
purposes.
Tetrahedral oxyanions are prominent radioactive contami-
nants (e.g., pertechnetate), toxic or otherwise troublesome
species (e.g., sulfate, chromate, arsenate, and phosphate, to
name a few), or matrix elements that can interfere with pro-
posed waste-treatment processes.[1] The design and synthesis
of efficient receptors for tetrahedral oxyanions is an impor-
tant field in supramolecular chemistry.[2] Anion receptors
with amide, pyrrole, urea, ammonium, imidazolium, and
guanidinium groups as binding sites for tetrahedral oxyan-
ions have been widely studied.[3] The urea moiety has been
utilized effectively in a number of tetrahedral oxyanion
binding systems.[2a] The synthesis of urea derivatives involves
the toxic reagents isocyanate or phosgene. Unsymmetrical
urea derivatives are relatively difficult to obtain.[4] As a
result, a building block with slight structural variation but
similar functionality to the urea moiety is desirable for con-
[a] Dr. Y.-J. Li, L. Xu, W.-L. Yang, Dr. H.-B. Liu, Prof. Y.-L. Li
CAS Key Laboratory of Organic Solids
Beijing National Laboratory for Molecular Sciences (BNLMS)
Institute of Chemistry, Chinese Academy of Sciences
Beijing 100190 (P. R. China)
Figure 1. Molecular modeling of a) tetramethylurea and b) amidetriazole
(HF 6-31G**).
Results and Discussion
Fax : (+86)10-82616576
E-mail: liyj@iccas.ac.cn
The synthesis of amidetriazole can be achieved through two
strategies: 1) Huisgen 1,3-dipolar cycloaddition between
methyl propiolate and a substituted azide followed by ami-
nolysis with amines (Scheme 1a) or 2) formation of N-sub-
stituted propiolamide through condensation of propiolic
acid and amines followed by CuI-catalyzed cycloaddition
(Scheme 1b). Molecular modeling (HF 6-31 G**) indicated
that amidetriazole exhibits a distance of 2.27 ꢀ between the
amide NH and triazole CH groups when it adopts an anion-
binding conformation. Amidetriazole is structurally similar
ylli@iccas.ac.cn
[b] L. Xu, W.-L. Yang
Graduate University of Chinese Academy of Sciences
Beijing 100190 (P. R. China)
[c] S.-W. Lai, Prof. C.-M. Che
Department of Chemistry
and the HKU-CAS Joint Laboratory on New Materials
The University of Hong Kong
Pokfulam Road (Hong Kong)
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201102760.
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FULL PAPER
Scheme 1. Strategies for the synthesis of amidetriazole.
Figure 3. Tetrahedral oxyanionic receptors designed based on different
preorganization strategies.
to tetramethylurea and has a larger dipole (7.89 versus
4.71 D). The structure of the amidetriazole unit is further il-
lustrated by the X-ray structure of model compound 1
(Figure 2). For the free amidetriazole motif, the amide NH
tion of hydrogen bonding, p–p stacking, and dipole–dipole
interactions for the realization of anion binding. These re-
ceptors are synthesized as illustrated in Schemes 2–4.
Sulfate is the smallest common tetrahedral anion and
plays important roles in biological systems and disease,[11] in
hydrometallurgy,[12] and as a pollutant.[13] Custelcean and co-
workers developed selective receptors for sulfate-based tri-
podal tris-urea systems for precipitation of anions from solu-
tion.[14] Custelcean, Hay, and co-workers have used self-as-
sembly strategies to construct urea-containing cage systems
with six urea groups arranged around sulfate.[15] Gale ob-
tained some sulfate-selective acyclic receptors based on
indole and carbazole.[16] Beer and Mullen utilized sulfate as
a template to prepare interlocked structures.[17] Macrocyclic
sulfate receptors such as cyclo[8]pyrrole,[18] cyclic tetraa-
mide/amine-based receptors,[19] and cyclic peptide-based mo-
lecular oysters[20] were also reported. The binding behavior
of our sulfate receptors will be studied.
Figure 2. a) Molecular structure of amidetriazole-containing model com-
pound 1; b) Crystal structure of model compound 1; c) Two-point hydro-
gen bonds formed by the amide NH group and the triazole nitrogen
atoms in a dimer of 1 in the crystal structure.
In our preliminary endeavor to build foldamers by using
the amidetriazole motif, we designed a new sulfate receptor,
L1, with an amidetriazole unit in the middle, another amide
and triazole CH units occupy opposite positions relative to
À
one another (Figure 2b), the N N=N triazole unit preferen-
tially forms an intermolecular
hydrogen bond with the amide
NH group (N···N distance=
3.035 ꢀ; Figure 2c). The amide-
triazole unit can resolve the
poor solubility of the urea
moiety through the formation
of a dimer rather than the poly-
mer-like assembly of ureas.
Furthermore, we designed
and synthesized
a series of
simple, acyclic receptors to con-
firm the potential of amidetria-
zole for the construction of tet-
rahedral oxyanion receptors
(Figure 3). The conformations
of these receptors are con-
trolled by either a V-shaped
carbazole or tripodal 2,4,6-trie-
thylbenzene, and the terminal
hydroxyl group on the chain
will provide additional anion-
binding affinity. A more elabo-
Scheme 2. Preparation of L1. Reaction conditions: a) SnCl2, ethanol, 81%; b) NaN3, sodium ascorbate, CuI,
N,Nꢂ-dimethylethane-1,2-diamine, DMSO/H2O (5:1), RT, 1 h, 81%; c) CuSO4, sodium ascorbate, ethanol/H2O
(2:1), RT, 8 h, 88%; d) N,N-dicyclohexylcarbodiimide (DCC), 4-dimethylamino pyridine (DMAP), CH2Cl2,
76%; e) CuSO4, sodium ascorbate, ethanol/H2O (2:1), RT, 8 h, 67%; f) Pyrene-1-carboxylic acid chloride,
rate example is the incorpora- NEt3, 63%.
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Y.-L. Li, Y.-J. Li et al.
addition of more sulfate
(5 equiv), the signals of protons
Hg and Hb were sharpened,
whereas Hf and Hk disappeared.
These results clearly indicate
that the addition of sulfate to a
solution of host L1 leads to the
predominant formation of a 2:1
host–guest complex at the ini-
tial stages of the titration up to
the sulfate/L1 ratio of 0.5. This
complex is gradually replaced
by a 1:1 complex as the sulfate/
L1 ratio increases from 0.5 to 1
and, ultimately, the 1:1 complex
prevails thereafter.[21] Large
binding constants (K1 and K2)
are anticipated from the ap-
pearance of sharp changes in
curvature at sulfate/L1 ratios of
1:2 and approximately 1:1, even
though the binding constants
cannot be obtained through
1H NMR titration data due to
line broadening. The binding
affinity of amidetriazole is defi-
nitely higher than that of its in-
dividual component, which is
supported by the small down-
field shift of the terminal tria-
zole proton. To obtain deeper
Scheme 3. Preparation of L2. Reaction conditions: a) NaN3, sodium ascorbate, CuI, N,Nꢂ-dimethylethane-1,2-
diamine, DMSO/H2O (5:1); b) Methyl propiolate, CuSO4, sodium ascorbate, ethanol/H2O (2:1), RT, 8 h, 85%
over two steps; c) 3-Aminopropan-1-ol, toluene, 808C, 10 h, 81%.
Scheme 4. Reaction conditions: a) Methyl propiolate, CuSO4, sodium ascorbate, ethanol/H2O (2:1), RT, 8 h,
95%; b) 3-Aminopropan-1-ol, toluene, 808C, 10 h, 90%.
group, and a triazole unit connected with benzene rings, in
which the binding affinity of the amidetriazole and its indi-
vidual components can be compared. The photoactive
pyrene ring is attached to the amide terminal as a fluores-
cent handle and provides p–p stacking; the triazole terminal
is equipped with a carboxylate group to increase the acidity
of the triazole CH proton relative to the amidetriazole CH
proton. Molecular modeling indicated that the two amide
NH and two triazole CH groups combined with the CH of
the connecting benzene group can interact with a sulfate
anion in a 1:1 or 2:1 ratio, to form six or twelve hydrogen
bonds, respectively.
Upon the addition of 0.5 equivalents of bis(tetrabutylam-
monium) sulfate (TBA2SO4), the triazole proton of the
middle amidetriazole unit (DdHg =1.61 ppm) and the amide
proton (DdHf =1.01 ppm) showed downfield shifts. The up-
field shifts of protons Hr and Hs on the pyrene ring and
alkyl chain, respectively, and Hh on the benzene ring close
to the pyrene ring is evidence for the 2:1 binding mode,
which can provide strong shielding effects to these protons.
Small upfield shifts of protons Hk, Hj, and He are also ob-
served. With the addition of another 0.5 equivalents of sul-
fate (1.0 equiv total), the signals of the central amide NH
(Hf) and triazole CH (Hg) protons migrated further down-
field and the upfield-shifted signals Hr, Hs, and Hh moved
back to their original position (Figure 4, middle). With the
insight for the sulfate-induced 2:1 folding, NOESY NMR
spectroscopy and molecular modeling were carried out for
the structural assignment of the sulfate complex in solution
(Figure 4, bottom). Strong NOE connections were exhibited
between Hs and Hk, Ht, and Hk, Hk and Hj, Hk and Hg, Hj
and Hf, Hg and He, and Hf and Hb, which supported the for-
mation of the folded half-circle conformation. NOE connec-
tions were clearly observed between the signals of the
middle (Hg) and terminal triazole protons (Hb), and also
with the terminal pyrene unit (Hs, Ht; see the circled cross
peaks in Figure 4, bottom). Because distances between Hg
and Hb, Hs, and Ht of the same chain are much too long for
any cross peak to be observed these signals must correspond
to intermolecular contacts between different chains.[22] This
is precisely the situation when the two chains wrap around
each other (Figure 4, top,c). This complex is stabilized by p–
p stacking between the pyrene unit and the close phenyl-tri-
azole plane in the second molecule and by dipole–dipole in-
teractions between the terminal phenyl (À2 D) and triazole
groups (+5 D) (Figure 4, top,c).[23] This can explain the
small downfield shift of triazole proton Hb and even the up-
field shift of the terminal amide proton Hk, which is the sum
of p–p stacking (upfield shift) and hydrogen-bonding inter-
actions (downfield shift). Dihydrogen phosphate can form a
similar 1:2 complex with L1, supported by the upfield shift
of the related aromatic protons, although detailed analysis
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Amidetriazole: A Versatile Building Block
FULL PAPER
of the p-stacked structure in the 2:1 host–guest complex.[23]
The absorbance then increases with the addition of more
sulfate until the 1:1 complex is dominant. The absorption at
l=365 nm behaves reversely, increasing then dropping,
which corresponds to the formation and destruction of p–p
stacking between the pyrene ring and phenyl-triazole planes.
These changes of L1 reflect structural reorganization due to
the binding of sulfate, consistent with the above 1H NMR
results. L1 exhibits an emission band at l=400 nm, which is
2À
quenched by the addition of SO4 (Figure S11 in the Sup-
porting Information).
Encouraged by the fact that two amidetriazole molecules
can form a 2:1 complex with sulfate, we coupled our amide-
triazoles on the 3,6-positions of a carbazole moiety to build
receptor L2 with two amide NH, two triazole CH, and two
OH groups present for hydrogen-bond formation. Carbazole
and its derivatives have been widely used as functional
building blocks in the fabrication of organic photoconduc-
tors, nonlinear optical materials, and photorefractive materi-
als due to their specific optical and electrochemical proper-
ties.[24] At the same time, the 6 ꢀ distance between the C3
and C6 carbon atoms and the V-shape generated upon 3,6-
modification rendered carbazole with the potential to con-
trol the geometry of the receptors.
The complexation behavior of host L2 with the sulfate
1
anion was studied by H NMR titration in [D6]acetone/5%
[D6]DMSO at 258C. Upon addition of 1 equivalent of sul-
fate, large downfield shifts of the amide NH (DdHe =
1.24 ppm), triazole (DdHd =1.71 ppm), and hydroxyl group
resonances (DdHi =2.49 ppm) were observed (Figure 5).
The stable 1:1 complex allowed for a structural investigation
in solution by using NOESY NMR spectroscopy. Strong
NOE connections were exhibited between Hd and Ha and
Hd and He (Figure S17 in the Supporting Information),
which supported the conformation of the amidetriazole moi-
eties within a carbazole unit, shown in Figure 5. Interesting-
ly, the carbazole proton Ha first shifted downfield (Dd=
1.09 ppm) almost proportionally to the amount of added sul-
fate until the sulfate/L2 ratio reached 1:1, shifted back up-
field until the ratio reached 6.3:1, and finally leveled off
(Figure 5, bottom). The signal of proton Hc started to move
downfield after the addition of 1 equivalent of sulfate. These
results clearly indicate that the two amidetriazole arms can
cooperatively capture one sulfate anion at first, then with
Figure 4. Top: a) Illustration of the sulfate-binding process of receptor
L1; b) Intramolecular NOE contact in the L12·SO4 complex; c) Molecular
modeling of the L12·SO4 complex and the intermolecular NOE contacts.
Middle: 1H NMR ([D6]acetone/0.5% [D6]DMSO, 400 MHz) spectra of
2À
L1 (5 mm) in the presence of SO4 ions (0.25, 0.5, 0.5 at 243 K, 0.75, 1.0,
À
the addition of more sulfate (6.3 equiv) the C N bond con-
and 5.0 equiv for b) to g), respectively). Bottom: Partial NOESY spec-
necting one of the triazole and carbazole rings rotates so
that each arm can bind one sulfate anion (Figure 5). The hy-
drogen-bonding interactions between proton Ha and sulfate
were decreased, whereas hydrogen-bonding interactions be-
tween proton Hc and sulfate were increased; a weak com-
plex with 1:2 host–guest stoichiometry was formed. The
binding constant (K1) of the first sulfate can be fitted from
proton Hd (K1 =3895mÀ1). Dihydrogen phosphate binds with
L2 in a similar way but with lower stability (Figure S4 in the
Supporting Information).
2À
trum (600 MHz) of L1+SO4 in [D6]acetone/0.5% [D6]DMSO at 243 K
(mixing time=1 s).
was prevented by line broadening (Figure S2 in the Support-
ing Information).
UV/Vis experiments were carried out in acetone to evalu-
ate the binding properties of L1 towards sulfate (Figure S11
in the Supporting Information). Upon addition of sulfate,
the absorption at l=274 nm first decreases to a minimum in
the presence of 0.5 equivalents of sulfate as a consequence
The binding affinity will increase with the addition of
binding moieties and strength of the preorganization. Tripo-
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Y.-L. Li, Y.-J. Li et al.
Figure 6. Crystal structure of the sulfate complex L3·SO4 (non-acidic hy-
drogen atoms and countercations omitted for clarity). a) Top view;
b),c) Side view from directions A and B shown in a); d) Hydrogen bonds
2À
around SO4
.
from 163.2–172.18 (164.118 on average); the C···O distances
À
ranged from 3.095–3.292 ꢀ (3.129 ꢀ on average) and C
H···O angles from 123.53–168.678 (154.118 on average); the
O···O distances ranged from 2.731–2.749 ꢀ (2.734 ꢀ on aver-
À
age) and O H···O angles from 160.3–161.28 (160.518 on
average).[26]
The interaction of receptor L3 with sulfate anions was fur-
ther investigated in [D6]acetone/5% [D6]DMSO by using a
1H NMR titration technique. The receptor–anion stoichio-
metries were determined by a continuous variation method
(Job plots) and proved to be 1:1 for sulfate anions. The ad-
dition of sulfate anions to 2.5 mm solutions of receptor 1 in
[D6]acetone/5% [D6]DMSO led to large downfield shifts of
the amide NH (DdHe =1.94 ppm), triazole proton (DdHd =
1.25 ppm), and terminal hydroxyl group resonances (DdHi =
1.72 ppm) (Figure 7). These large downfield shifts indicate
that the sulfate anion forms strong hydrogen bonds with all
binding sites of the tripodal receptor. The stability constant
of the sulfate complex of L3 could only be determined by
analysis of the signal shifts of benzylic proton Hc because of
line broadening of the binding-site proton signals in the
1H NMR spectrum. The data was fitted with the
WinEQNMR2 software[27] to give K1 >100000.
Figure 5. 1H NMR ([D6]acetone/0.5% [D6]DMSO, 400 MHz) spectra of
L2 (5 mm) in the presence of SO4 ions (0.5, 1.0, 2.0, and 5.0 equiv for b)
2À
&
*
*
to e), respectively) and the titration curves (Ha , Hb , Hc N, Hd , He
~
, Hi ꢃ).
dal receptor L3 was designed based on the “pinwheel” scaf-
fold 1,3,5-trisubstituted-2,4,6-triethylbenzene.[25] Preorgani-
zation is achieved by incorporation of three amidetriazole
groups into a 1,3,5-triethylbenzene core, to generate a cone-
shape cavity. The introduction of steric bulk around the ben-
zene-derived core predisposes the compound to adopt the
preferred conformation.[25] We obtained single crystals of a
sulfate complex of L3 for X-ray analysis by diffusing ether
into a solution of L3 and TBA2·SO4 in acetone/5% DMSO
(Figure 6). L3 shows high conformational complementarity
with the sulfate anion in the 1:1 host–guest complex; three
amide NH, three triazole CH, and two terminal OH groups
can be involved in hydrogen bonding with the sulfate to
form 11 hydrogen bonds. The N···O distances ranged from
Of these representative foldamer-type, cleft-type, and tri-
podal receptors that contained amidetriazole groups, the
third receptor L3 forms 1:1 complexes with sulfate anions
that have remarkably high stability, the other two receptors
additionally form complexes of higher stoichiometry. We ex-
panded the anion-binding studies of receptor L3 to investi-
gate oxyanion selectivity. Addition of tetrabutylammonium
iodide to L3 in [D6]acetone/0.5% [D6]DMSO resulted in
1
only very small perturbations in the H NMR spectra. For
chloride and bromide ions the triazole motifs supply stron-
À
À
ger C H···halide bonds than the amide N H···halide bonds,
evidenced from the larger chemical shifts of the resonance
À
2.831–2.906 ꢀ (2.869 ꢀ on average) and N H···O angles
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Amidetriazole: A Versatile Building Block
FULL PAPER
software.[27] With increasing halide size, the binding stability
decreased. In the oxyanions studied, L3 showed the greatest
selectivity towards sulfate, with an affinity too high to mea-
sure in the chosen medium (K1 >100000mÀ1).
An interesting phenomenon was observed for fluoride
binding. With the addition of tetrabutylammonium fluoride
(TBA-F) trihydrate to a solution of L3 in [D6]acetone/0.5%
[D6]DMSO, larger chemical shifts were observed for the res-
onance of amide proton He relative to that of triazole
proton Hd. The 1:1 binding stoichiometry was obtained from
proton Hd, whereas a final host–guest stoichiometry of 1:3
1
was achieved from proton He. Uncommonly, a new H NMR
resonance at d=8.11 ppm appeared, which reached the
highest level at 1.57 equivalents of hydrated fluoride and de-
creased with the addition of more hydrated fluoride (Fig-
ure 8a and b). This new peak was assigned as H2O bound to
fluoride and the integration of this peak relative to proton
Hd showed a 4:1 ratio to L3. The results indicated that tripo-
dal L3 first formed a 1:1 complex with hydrated fluoride,
followed by a 1:3 complex with fluoride. 19F NMR was used
to investigate fluoride anion binding by the receptor L3.
The addition of L3 to a solution of TBA-F trihydrate in
[D6]acetone/0.5% [D6]DMSO resulted in a downfield shift
of d=4.46 ppm relative to the free fluoride resonance (Fig-
ure 8c), which results from the weakened hydrogen bonding
between fluoride and water, indicative that the fluoride
anion does not directly participate in hydrogen bonding
Figure 7. 1H NMR ([D6]Acetone/0.5% [D6]DMSO, 400 MHz) spectra of
L3 (2.5 mm) in the presence of SO4 ions (1.0, 2.0, 3.0, and 7.0 equiv for
b) to e), respectively).
[28]
À
À
2À
with the CH and NH groups of the receptor L3. These
results led to the binding model presented in Figure 8d. The
water molecules formed a hydrogen-bond network with the
middle fluoride ion and outer C=O groups, and the triazole
CH and terminal OH groups provided further stabilization
of proton Hd relative to He (Figures S8 and S9 in the Sup-
porting Information). The opposite trends were observed
for oxyanionic anions, that is, the amides formed stronger
À
to the top water molecule through O H···O interactions.
The hydrated fluoride functioned as a pseudo-oxyanion and
À
À
N H···O bonds than the C H···O bonds to the triazole units
(Figures S6 and S10 in the Supporting Information). The
resonance of the terminal OH group shifted downfield with
the addition of halide, whereas it disappeared in the pres-
ence of oxyanions. The titration results indicated that hal-
ides (ClÀ, BrÀ) mainly interacted with the triazole CH unit,
whereas oxyanions interacted with the NH, CH, and OH
groups cooperatively. The binding constants (K1 only) for
the first anion derived from a model incorporating a final
host–guest stoichiometry of 1:3 are summarized in Table 1.
The analysis was carried out with the aid of WinEQNMR2
showed relatively strong binding with L3.
Conclusion
We have developed a urea-like anion-recognizing motif,
amidetriazole, which can be easily synthesized and derivat-
ized and shows good solubility. This molecular platform can
be used extensively for the construction of numerous recep-
tor systems appended with functional groups. These systems
can open the way to many applications, for example, in the
field of addressable sensors or display. The studies demon-
strated that rational design with the cooperation and preor-
ganization of the amidetriazole units can lead to quite
strong oxyanion receptors. We are currently developing
more preorganized receptors that contain amidetriazole
units, such as macrocycles, as more practical and selective
chemosensors for oxyanions.
Table 1. Binding constants (K1) determined by 1H NMR titration for the
interaction of L3 with various anions.[a]
Anion FÀ·3H2O ClÀ BrÀ IÀ
À
2À
CH3COOÀ H2PO4
SO4
>100000[c]
[b]
K1
581
186 16
–
106 292
[a] Anions as nBu4N+ salts in [D6]acetone/0.5% [D6]DMSO, triazole pro-
tons Hd fit with WinEQNMR2.[27] Errors in K1 are <10%. Equilibria
were modeled according to the binding of up to three anions by each
host. [b] Only small perturbations were observed in the 1H NMR spec-
trum upon addition of iodide anions. [c] Fitting followed with benzyl
proton Hc because of the line broadening of the binding-site proton sig-
nals in the NMR spectra.
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Y.-L. Li, Y.-J. Li et al.
sorption spectra were measured on a JASCO V-579 spectrophotometer.
Fluorescence excitation and emission spectra were recorded using a Hita-
chi F-4500. All single crystal X-ray diffraction data were collected on a
Rigaku Saturn X-ray diffractometer with graphite-monochromator MoKa
radiation (l=0.71073 ꢀ) at 173 K. Intensities were corrected for absorp-
tion effects using the multi-scan technique SADABS (Siemens area de-
tector absorption corrections). The structures were solved by direct meth-
ods and refined by a full-matrix least-squares technique based on F2 by
using the SHELXL 97 program (Sheldrick, 1997). The extended packing
plots and data from crystal packing were obtained with Mercury 1.4.1
software.
Compound S1a: DMF (1 drop) was added to a solution of 3-iodo-5-nitro-
benzoic acid (2.93 g, 10 mmol) in SOCl2 (5 mL) and the mixture was
stirred at 508C for 2 h. The solvent was removed under vacuum. The resi-
due was dissolved in dry CH2Cl2 (5 mL) and added dropwise to a solution
of 2-methylbutan-1-ol (1 g, 12 mmol) and triethylamine (TEA) (3 mL) in
dry CH2Cl2 (20 mL). The mixture was stirred at RT for 4 h. The solvents
were removed under vacuum and the residue was dissolved in CH2Cl2
then washed with brine. The organic phase was dried (Na2SO4) and the
solvent was removed under vacuum. The product was purified by chro-
matography (SiO2, hexane) to give S1a (3 g, 82.6%). 1H NMR
(400 MHz, CDCl3): d=8.79 (s, 1H), 8.73 (s, 1H), 8.66 (s, 1H), 4.28 (m,
1H), 4.18 (m, 1H), 1.90 (m, 1H), 1.54 (m, 1H), 1.29 (m, 1H), 1.03 (d, J=
8 Hz, 3H), 0.97 ppm (t, J=8 Hz, 3H); 13C NMR (100 MHz, CDCl3): d=
163.2, 148.6, 144.0, 136.0, 133.6, 123.8, 93.4, 70.9, 34.3, 26.1, 16.5,
11.3 ppm; MS (EI): m/z: 363; elemental analysis calcd (%) for
(C12H14INO4): C 39.69, H 3.89, N 3.86; found: C 39.38, H 3.92; N 3.89.
Compound S1b: SnCl2·2H2O (9.06 g, 40.0 mmol) was added to a solution
of S1a (2.9 g, 8 mmol) in ethanol (5 mL). The reaction mixture was
heated at reflux until the reaction was complete (indicated by TLC analy-
sis). The solvent was removed under reduced pressure and the crude resi-
due was partitioned between ethyl acetate and 2m KOH. The aqueous
layer was extracted with ethyl acetate (3ꢃ25 mL) and the combined or-
ganic extracts were washed with brine (2ꢃ25 mL) and water (3ꢃ50 mL),
dried (Na2SO4), and concentrated under reduced pressure. The crude res-
idue was subjected to flash silica gel column chromatography (20% ethyl
1
acetate in hexanes) to yield S1b (81%). H NMR (400 MHz, CDCl3): d=
7.74 (s, 1H), 7.31 (s, 1H), 7.23 (s, 1H), 4.17 (dd, J=10.7, 6.0 Hz, 1H),
4.09 (dd, J=10.7, 6.7 Hz, 1H), 1.84 (dq, J=13.2, 6.7 Hz, 1H), 1.58–1.44
(m, 1H), 1.34–1.19 (m, 1H), 1.00 (d, J=6.7 Hz, 2H), 0.95 ppm (t, J=
7.5 Hz, 2H); 13C NMR (100 MHz, CDCl3): d=165.5, 147.7, 133.1, 128.3,
127.6, 115.4, 94.5, 70.0, 34.4, 26.2, 16.6, 11.4 ppm; MS (EI): m/z: 333; ele-
mental analysis calcd (%) for (C12H16INO2): C 43.26, H 4.84, N 4.20;
found: C 43.14, H 4.72, N 4.31.
Compound S1c: Compound S1b (1.33 g, 4 mmol), NaN3 (520 mg,
8 mmol), sodium ascorbate (44.6 mg, 0.2 mmol), CuI (76 mg, 0.4 mmol),
N,N’-dimethylethane-1,2-diamine (0.6 mmol) were added to degassed 5:1
DMSO/H2O (10 mL).[29] The reaction mixture was stirred at RT for 1 h.
The crude reaction mixture was taken up in a mixture of brine and
EtOAc. The aqueous phase was extracted with EtOAc (ꢃ3). The com-
bined organic phases were concentrated in vacuo and the residue was pu-
rified by flash chromatography over silica gel (100:1 CH2Cl2/methanol)
to give the aryl azide S1c (803 mg, 81%). 1H NMR (400 MHz, CDCl3):
d=7.09 (s, 1H), 7.05 (s, 1H), 6.44 (s, 1H), 4.16 (dd, J=10.7, 6.0 Hz, 1H),
4.11–4.03 (m, 1H), 3.85 (d, J=15.4 Hz, 1H), 1.82 (dq, J=13.1, 6.6 Hz,
1H), 1.57–1.42 (m, 1H), 1.32–1.18 (m, 1H), 0.98 (d, J=6.8 Hz, 2H),
0.93 ppm (t, J=7.5 Hz, 2H); 13C NMR (100 MHz, CDCl3): d=166.1,
148.0, 141.4, 133.0, 112.7, 109.9, 109.1, 69.8, 34.3, 26.2, 16.5, 11.3 ppm; MS
(EI): m/z: 206 [MÀN3], 219 [MÀN2]; elemental analysis calcd (%) for
(C12H16N4O2): C 58.05, H 6.50, N 22.57; found: C 58.21, H 6.43, N 22.48.
Figure 8. a) 1H NMR ([D6]/acetone/0.5% [D6]DMSO, 400 MHz) spectra
of L3 (2.5 mm) in the presence of TBA-F·3H2O; b) Titration curves; CH
&
*
*
, NH , (the integration of the peak at d=8.11 ppm ( ) is calibrated
with proton Hd); c) Partial 19F NMR spectra (400 MHz) of TBA-F and a
1:1 mixture of L3 and TBA-F in [D6]acetone/0.5% [D6]DMSO at 298 K;
d) Binding model of L3 with hydrated fluoride.
Experimental Section
General methods: All reagents were obtained from commercial suppliers
and used as received unless otherwise noted. Column chromatography
was performed on silica gel (160–200 mesh) and TLC was performed on
precoated silica gel plates and observed under UV light. NMR spectra
were recorded on Bruker Avance DPS-400 and Bruker Avance DPS-600
spectrometers at room temperature (298 K). Chemical shifts were refer-
enced to the residual-solvent peaks. MALDI-TOF mass spectrometry
was performed on a Bruker Biflex III mass spectrometer. Electronic ab-
Compound S1d: CuSO4 (24.5 mg, 0.1 mmol) and sodium ascorbate
(40 mg, 0.2 mmol) were added to a solution of S1c (744 mg, 3 mmol) and
methyl propiolate (252 mg, 3 mmol) in ethanol/H2O (2:1). The mixture
was stirred at RT for 8 h. Ethanol was removed under vacuum and
CH2Cl2 was added. The organic phase was washed with water and dried
(Na2SO4). The residue was purified by silica gel chromatography (100:1
CH2Cl2/methanol) to afford S1d (876 mg, 88%) as
a white solid.
1H NMR (400 MHz, CDCl3): d=8.55 (s, 1H), 7.63 (s, 1H), 7.45 (s, 1H),
4788
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Chem. Eur. J. 2012, 18, 4782 – 4790

Amidetriazole: A Versatile Building Block
FULL PAPER
7.42 (s, 1H), 4.23 (dd, J=10.7, 6.0 Hz, 1H), 4.14 (dd, J=10.7, 6.7 Hz,
1H), 4.00 (s, 2H), 1.88 (dd, J=13.3, 6.7 Hz, 1H), 1.59–1.46 (m, 1H),
1.35–1.22 (m, 1H), 1.02 (d, J=6.7 Hz, 2H), 0.96 ppm (t, J=7.5 Hz, 2H);
13C NMR (100 MHz, CDCl3): d=165.6, 161.1, 148.5, 140.6, 137.4, 133.3,
125.8, 116.5, 110.8, 110.4, 70.3, 52.5, 34.3, 26.2, 16.6, 11.4 ppm; MS (EI):
m/z: 332; elemental analysis calcd (%) for (C16H20N4O4): C 57.82, H 6.07,
N 16.86; found: C 57.55, H 6.15, N 16.73.
brine and EtOAc. The aqueous phase was extracted with EtOAc (ꢃ1–3).
The combined organic phases were concentrated in vacuo and the resi-
due was used without further purification. CuSO4 (24.5 mg, 0.1 mmol)
and sodium ascorbate (40 mg, 0.2 mmol) were added to crude 3,6-diazi-
do-9-octyl-9H-carbazole (650 mg, 1.8 mmol) and methyl propiolate
(504 mg, 6 mmol) in 2:1 ethanol/H2O (15 mL). The mixture was stirred at
RT for 8 h. Ethanol was removed, then CH2Cl2 was added. The organic
phase was washed with water and dried (Na2SO4). The residue was puri-
fied by silica gel chromatography (100:1 CH2Cl2/methanol) to afford S2
(899 mg, 85%) as a white solid. 1H NMR (400 MHz, CDCl3): d=8.61 (s,
2H), 8.48 (d, J=2.0 Hz, 2H), 7.90 (dd, J=8.8, 2.1 Hz, 2H), 7.61 (d, J=
8.8 Hz, 2H), 4.42 (t, J=7.1 Hz, 2H), 4.03 (s, 6H), 1.92 (q, J=6.9 Hz,
2H), 1.42–1.32 (m, 4H), 1.32–1.23 (m, 6H), 0.86 ppm (t, J=6.6 Hz, 3H);
13C NMR (100 MHz, CDCl3): d=161.5, 141.5, 129.6, 123.1, 120.4, 114.1,
110.7, 52.7, 44.1, 32.0, 29.6, 29.4, 29.3, 27.6, 22.9, 14.4 ppm; MS (MALDI-
TOF): m/z: 530.4; elemental analysis calcd (%) for (C28H31N7O4): C
63.50, H 5.90, N 18.51; found: C 63.34, H 5.95, N 18.46.
Compound S1e: Propiolic acid (100 mg, 1.4 mmol) and N,N-dicyclohexyl-
carbodiimide (DCC) (290 mg, 1.4 mmol) were combined in CH2Cl2
(10 mL), the solution was stirred for 10 min, then S1d (464 mg,
1.4 mmol) and 4-dimethylaminopyridine (DMAP) (5 mg) were added.
The reaction mixture was stirred for 30 min, then the precipitate was fil-
tered off and the solvent was removed under vacuum. The residue was
purified by silica gel chromatography (50:1 CH2Cl2/methanol) to afford
S1e (408 mg, 76%) as a white solid. 1H NMR (400 MHz, CDCl3): d=
8.62 (s, 1H), 8.53 (s, 1H), 8.38 (s, 1H), 8.20 (s, 1H), 4.26 (dd, J=10.7,
6.0 Hz, 1H), 4.18 (dd, J=10.6, 6.8 Hz, 1H), 4.01 (s, 2H), 3.04 (s, 1H),
1.89 (dd, J=13.3, 6.4 Hz, 1H), 1.59–1.46 (m, 1H), 1.28 (dd, J=14.0,
7.4 Hz, 1H), 1.02 (d, J=6.7 Hz, 2H), 0.96 ppm (t, J=7.4 Hz, 2H);
13C NMR (100 MHz, CDCl3): d=164.9, 161.0, 157.3, 150.6, 140.7, 139.6,
136.9, 133.2, 126.0, 121.6, 117.4, 116.3, 75.6, 70.6, 52.6, 34.3, 26.2, 16.6,
11.3 ppm; MS (EI): m/z: 384; elemental analysis calcd (%) for
(C19H20N4O5): C 59.37, H 5.24, N 14.58, found: C 59.26, H 5.12, N 14.47.
Compound L2: 3-Aminopropan-1-ol (2 mL) was added to a solution of
S2 (530 mg, 1 mmol) in toluene (5 mL) and the mixture was heated at
808C for 10 h. Ethyl acetate (30 mL) and H2O (30 mL) were added and
the organic phase was dried (Na2SO4). The solvent was removed under
vacuum. The product was purified by silica gel chromatography (10:1
CH2Cl2/methanol) to afford L2 (500 mg, 81.1%) as
a white solid.
1H NMR (400 MHz, [D6]acetone): d=9.04 (s, 2H), 8.92 (d, J=1.7 Hz,
2H), 8.24 (s, 2H), 8.14 (dd, J=8.8, 1.9 Hz, 2H), 7.91 (d, J=8.9 Hz, 2H),
4.62 (t, J=7.0 Hz, 2H), 4.11 (s, 1H), 3.65 (q, J=5.9 Hz, 4H), 3.57 (q, J=
6.4 Hz, 4H), 2.01–1.93 (m, 2H), 1.82 (quin, J=6.3 Hz, 4H), 1.45 (m, 2H),
1.36 (m, 2H), 1.24 (m, 6H), 0.84 ppm (t, J=6.6 Hz, 3H); 13C NMR
(100 MHz, [D6]DMSO): d=160.5, 144.7, 141.4, 130.1, 125.5, 123.1, 120.3,
114.3, 111.8, 59.7, 37.1, 33.3, 32.1, 29.7, 29.6, 27.3, 22.9, 14.8 ppm; MS
(MALDI-TOF): m/z: 616.5 [M+H], 638.5 [M+Na]; elemental analysis
calcd (%) for (C32H41N9O4): C 62.42, H 6.71, N 20.47; found: C 62.29, H
6.76, N 20.40.
Compound S1 f: CuSO4 (24.5 mg, 0.1 mmol) and sodium ascorbate
(40 mg, 0.2 mmol) were added to a solution of S1e (384 mg, 1 mmol) and
S1c (248 mg, 1 mmol) in 2:1 ethanol/H2O (9 mL). The mixture was
stirred at RT for 8 h. Ethanol was removed under vacuum and CH2Cl2
was added. The organic phase was washed with water and dried
(Na2SO4). The residue was purified by silica gel chromatography (100:1
CH2Cl2/methanol) to afford S1 f (423 mg, 67%) as a pale-yellow solid.
1H NMR (400 MHz, CDCl3): d=9.34 (s, 1H), 8.77 (s, 1H), 8.66 (s, 1H),
8.27 (s, 1H), 8.22 (s, 1H), 7.67 (s, 1H), 7.46 (s, 1H), 7.38 (s, 1H), 4.33–
4.11 (m, 2H), 4.02 (s, 2H), 1.90 (dt, J=13.9, 6.7 Hz, 1H), 1.60–1.48 (m,
1H), 1.30 (dt, J=15.2, 7.9 Hz, 1H), 1.03 (dd, J=10.7, 6.9 Hz, 3H), 1.00–
0.92 ppm (m, 3H); 13C NMR (100 MHz, CDCl3): d=165.5, 164.9, 161.0,
158.2, 148.5, 143.2, 140.8, 139.5, 137.4, 137.1, 133.3, 126.0, 124.6, 121.3,
117.1, 116.7, 116.0, 110.6, 70.7, 70.3, 52.6, 34.4, 26.3, 16.6, 11.4 ppm; MS
(MALDI-TOF): m/z: 633.4 [M+H], 665.4 [M+Na]; elemental analysis
calcd (%) for (C31H36N8O7): C 58.85, H 5.74, N 17.71; found: C 58.69, H
5.65, N 17.53.
Compound S3a: CuSO4 (24.5 mg, 0.1 mmol) and sodium ascorbate
(40 mg, 0.2 mmol) were added to a solution of 1,3,5-tris(azidomethyl)-
2,4,6-triethylbenzene[25a] (654 mg, 2 mmol) and methyl propiolate
(554 mg, 6.6 mmol) in 2:1 ethanol/H2O (15 mL). The mixture was stirred
at RT for 8 h. Ethanol was removed, then CH2Cl2 was added. The organ-
ic phase was washed with water and dried (Na2SO4). The residue was pu-
rified by silica gel chromatography (100:1 CH2Cl2/methanol) to afford
S3a (1.1 g, 95%) as a white solid. 1H NMR (400 MHz, CDCl3): d=7.78
(s, 3H), 5.71 (s, 6H), 3.93 (s, 6H), 2.76 (q, J=8.0 Hz, 6H), 0.96 ppm (t,
J=8.0 Hz, 9H); 13C NMR (100 MHz, CDCl3): d=161.2, 147.2, 140.5,
129.8, 127.1, 52.7, 48.5, 24.0, 15.7 ppm; MS (MALDI-TOF): m/z: 602.4
[M+Na]; elemental analysis calcd (%) for (C27H33N9O6): C 55.95, H 5.74,
N 21.75; found: C 55.86, H 5.65, N 21.88.
Compound L1: DMF (1 drop) was added to a solution of pyrene-1-car-
boxylic acid (148 mg, 0.6 mmol) in SOCl2 (3 mL) and the mixture was
stirred at 508C for 2 h. The solvent was removed under vacuum. The resi-
due was dissolved in dry CH2Cl2 (5 mL) and added dropwise to a solution
of S1 f (316 mg, 0.5 mmol) and TEA (2 mL) in dry CH2Cl2 (20 mL). The
mixture was stirred at RT for 4 h. The solvents were removed under
vacuum, the residue was dissolved in CH2Cl2, then washed with brine.
The organic phase was dried over anhydrous Na2SO4. The solvent was re-
moved under vacuum then the product was purified by silica gel chroma-
tography (CH2Cl2) to give L1 (271 mg, 63%). 1H NMR (400 MHz,
[D6]acetone): d=10.95 (s, 9H), 10.71 (s, 9H), 9.43 (s, 7H), 9.31 (s, 7H),
9.09 (s, 8H), 8.97 (s, 8H), 8.86 (s, 8H), 8.73 (d, J=9.1 Hz, 15H), 8.60–
8.21 (m, 71H), 8.15 (t, J=7.6 Hz, 9H), 4.26 (dtd, J=17.7, 10.7, 6.8 Hz,
33H), 3.96 (d, J=17.8 Hz, 27H), 2.90 (d, J=13.6 Hz, 54H), 2.58 (s, 4H),
2.48 (s, 15H), 2.14 (s, 5H), 2.09–2.01 (m, 102H), 1.92 (d, J=6.0 Hz,
23H), 1.70–1.46 (m, 21H), 1.46–1.11 (m, 39H), 1.16–1.11 (m, 2H), 1.07
(d, J=6.7 Hz, 45H), 0.98 (t, J=7.4 Hz, 48H), 0.89–0.84 ppm (m, 4H);
13C NMR (150 MHz, [D6]acetone): d=169.9, 166.3, 162.2, 159.9, 145.2,
142.9, 141.9, 141.8, 138.7, 138.6, 134.5, 134.3, 132.8, 132.3, 132.1, 130.5,
130.3, 128.7, 128.2, 127.7, 127.6, 127.0, 126.1, 126.0, 125.9, 125.7, 122.6,
122.4, 117.6, 117.4, 71.4, 53.0, 35.9, 27.5, 17.5, 12.4 ppm; MS (MALDI-
TOF): m/z: 883.9 [M+Na]; elemental analysis calcd (%) for
(C48H44N8O8): C 66.97, H 5.15, N 13.02; found: C 66.85, H 5.24, N 13.13.
Compound L3: 3-Aminopropan-1-ol (2mL) was added to a solution of
S3a (580mg, 1mmol) in toluene (5mL) and the mixture was heated at
808C for 10h. Ethyl acetate (30mL) and H2O (30mL) were added, then
the organic phase was dried (Na2SO4). The solvent was removed under
vacuum and the residue was purified by silica gel chromatography (10:1
CH2Cl2/methanol) to afford L3 (637mg, 90%) as a white solid. 1H NMR
(400 MHz, [D6]DMSO): d=8.52 (t, J=5.8Hz, 3H), 8.44 (s, 3H), 5.74 (s,
6H), 4.53 (t, J=5.2 Hz, 6H), 3.47 (dd, J=11.5, 5.9 Hz, 6H), 3.32 (dd, J=
12.9, 6.5Hz, 6H), 2.86 (d, J=7.3 Hz, 6H), 1.68 (quin, J=6.5 Hz, 6H),
0.77 ppm (t, J=7.2 Hz, 9H); 13C NMR (100 MHz, [D6]DMSO): d=160.6,
147.1, 143.9, 130.7, 127.0, 59.7, 48.9, 37.1, 33.3, 24.1, 16.0 ppm; MS
(MALDI-TOF): m/z: 709.6 [M+H], 731.6 [M+Na]; elemental analysis
calcd (%) for (C33H48N12O6): C 55.92, H 6.83, N 23.71; found: C 55.79, H
6.75, N 23.49.
Acknowledgements
Compound S2: 3,6-Diiodo-9-octyl-9H-carbazole (1.06 g, 2 mmol), NaN3
(390 mg, 6 mmol), sodium ascorbate (44.6 mg, 0.2 mmol), CuI (76 mg,
0.4 mmol), and N,Nꢂ-dimethylethane-1,2-diamine (0.6 mmol) were added
to degassed 5:1 DMSO/H2O (10 mL).[29] The reaction mixture was stirred
at RT for 1 h. The crude reaction mixture was taken up in a mixture of
This work was supported by the National Nature Science Foundation of
China (21031006, 20971127, 90922017, 20831160507) and the National
Basic Research 973 Program of China.
Chem. Eur. J. 2012, 18, 4782 – 4790
ꢁ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
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Received: September 4, 2011
Published online: February 29, 2012
4790
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Chem. Eur. J. 2012, 18, 4782 – 4790