From homogeneous to heterogeneous catalysis of the three-component coupling of oxysulfonyl azides, alkynes, and amines

Article abstract of DOI:10.1002/cctc.201300241

A reliable procedure for the synthesis of oxysulfonyl azides has been developed and applied to the three-component coupling reactions of azides, alkynes, and amines catalyzed homogeneously by CuI, which led to the formation of N-oxysulfonyl amidines with

Full text of DOI:10.1002/cctc.201300241

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Azide-ways manoeuver: Oxysulfonyl
azide is developed for the formation of
N-oxysulfonyl amidines. Three kinds of
CuI catalysts are tested, which include
CuI, Cu2I2(PDIN) without micropores,
and Cu2I2(BTTP4) with micropores
(PDIN=1,4-phenylene diisonicotinate,
BTTP4=benzene-1,3,5-triyltriisonicoti-
nate). Both homogeneous CuI and het-
erogeneous Cu2I2(BTTP4) are catalytically
efficient and provide N-oxysulfonyl ami-
dines in good yields.
T. Yang, H. Cui, C. Zhang, L. Zhang,*
C.-Y. Su*
&& – &&
From Homogeneous to
Heterogeneous Catalysis of the Three-
Component Coupling of Oxysulfonyl
Azides, Alkynes, and Amines
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DOI: 10.1002/cctc.201300241
From Homogeneous to Heterogeneous Catalysis of the
Three-Component Coupling of Oxysulfonyl Azides,
Alkynes, and Amines
Tao Yang,[a] Hao Cui,[a] Changhe Zhang,[a] Li Zhang,*[a] and Cheng-Yong Su*[a, b]
A reliable procedure for the synthesis of oxysulfonyl azides has
been developed and applied to the three-component coupling
reactions of azides, alkynes, and amines catalyzed homogene-
ously by CuI, which led to the formation of N-oxysulfonyl ami-
dines with good yields. To fully evaluate the catalytic activity
towards this coupling reaction, two coordination frameworks,
namely, Cu2I2(PDIN) without micropores and Cu2I2(BTTP4) with
micropores (PDIN=1,4-phenylene diisonicotinate, BTTP4=
benzene-1,3,5-triyltriisonicotinate), were prepared by a facile
one-pot reaction as heterogeneous catalysts. Catalytic results
showed that nonporous Cu2I2(PDIN) was almost inactive for
the three-component coupling reaction, whereas microporous
Cu2I2(BTTP4) was an efficient heterogeneous catalyst for the
synthesis of N-oxysulfonyl amidines. Furthermore, porous Cu2I2-
(BTTP4) displayed a shape-selective performance with respect
to the alkyne substrates, and aromatic alkynes were preferable
to aliphatic alkynes. The location of the catalytically active sites
in the Cu2I2(BTTP4) framework has been studied by a series
physical techniques, which includes powder XRD, CO2 gas ad-
sorption, IR spectroscopy, energy dispersive X-ray analysis, and
X-ray photoelectron spectroscopy, which suggests that the cat-
alytic sites are not only on the external surface but also inside
the micropores.
Introduction
Over the past decade, metal–organic frameworks (MOFs), also
called porous coordination polymers (PCPs), have attracted
considerable interest because of their designable structures,
tunable channels, high internal surface area, and micro/meso-
porosity. Since the 1990s, a large number of MOFs have been
examined as heterogeneous catalysts, which were first based
on their intrinsic catalytic properties such as Lewis acid cataly-
sis and redox catalysis of the metal components.[1–6] To con-
struct catalytic MOFs capable of more valuable reactions, scien-
tists have developed three important strategies, (i) direct incor-
poration of homogeneous catalysts into a linker ligand,[7–16] (ii)
grafting an organocatalyst onto a metal node,[17–19] and (iii) ad-
sorption of transition-metal complexes into the cavities fol-
lowed by reduction to lead to the formation of catalytic nano-
sized metal particles.[20–26] In these strategies, the metal nodes
usually act as building units rather than catalytic sites.[27–30]
We are interested and engaged in the development of cata-
lytic MOFs in which the metal nodes themselves can act as cat-
alytic sites and promote reactions that lead to the formation of
valuable products.[31–34] Since 2000, a variety of CuI-based
frameworks have been constructed from bi- or tritopic ligands
as a result of the rich coordination chemistry of CuI as well as
the strong coordination nature of IÀ.[35–38] Interestingly, CuI can
promote a number of organic reactions, especially the remark-
able click reactions[39,40] and multicomponent coupling reac-
tions.[41–44] Therefore, the construction of porous CuI MOFs may
provide a feasible and convenient approach to self-supported,
heterogeneous catalysts with CuI ions that act as both metal
nodes and potential catalytic sites.[45–48] Furthermore, careful in-
vestigations into the catalytic activity as well as detailed mech-
anistic studies show that N-containing ligands, such as benzi-
midazole, triazole, and pyridine, can accelerate CuI-catalyzed
reactions,[49,50] which arouses our interest to study the applica-
tions of porous pyridine-based CuI MOFs in heterogeneous
catalysis.
[a] T. Yang, H. Cui, C. Zhang, Prof. L. Zhang, Prof. C.-Y. Su
MOE Laboratory of Bioinorganic and Synthetic Chemistry
State Kay of Optoelectronic Materials and Technologies
School of Chemistry and Chemical Engineering
Sun Yat-Sen University
Guangzhou 510275 (China)
Herein, we reveal that CuI and a porous MOF of Cu2I2(BTTP4)
(BTTP4=benzene-1,3,5-triyltriisonicotinate) can catalyze the
synthesis of N-oxysulfonyl amidines in a three-component cou-
pling reaction with oxysulfonyl azide as an efficient one-N-
atom source homo- and heterogeneously, respectively. Cu2I2-
(BTTP4) has a large free volume of 1776.9 ꢁ3 per unit cell, as
well as 1D channels (9ꢂ12 ꢁ2), which provide a platform to
perform reactions in the framework channels and display
shape-selective catalytic capability (Figure 1).[45]
Fax: (+86)20-8411-5178
E-mail: zhli99@mail.sysu.edu.cn
cesscy@mail.sysu.edu.cn
[b] Prof. C.-Y. Su
State Key Laboratory of Organometallic Chemistry
Shanghai Institute of Organic Chemistry
Chinese Academy of Sciences
Shanghai 200032 (China)
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/cctc.201300241.
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ic analysis, which discloses the E form of the generat-
ed C=N double bond (Figure S22). Next, we exam-
ined the scope of the reaction with respect to the
azide component. As illustrated by the examples
shown in Table 1, a range of oxysulfonyl azides par-
ticipated efficiently in the three-component coupling
reaction. For example, aryl (entries 1, 4–7) and alkyl
azides (entry 8) were competent reactants and pro-
vided N-oxysulfonyl amidines with good yields. Both
electron-deficient and -rich oxysulfonyl azides were
reactive in this coupling reaction (entries 6 and 7).
Figure 1. Illustration of the catalytic behavior of Cu2I2(BTTP4).
Based on these results, oxysulfonyl azides appear
Results and Discussion
to be promising one-N-atom sources, in addition to sulfonyl
and phosphoryl azides, and may be further applied in more
metal-catalyzed transformations to yield a variety of valuable
compounds. To further evaluate the reactivity of oxysulfonyl
azides in the three-component coupling of azides, alkynes, and
amines, we extended the catalyst from homogeneous CuI to
heterogeneous CuI-containing coordination frameworks.
Amidine synthesis from oxysulfonyl azide
As a broad class of compounds that are widely available or can
be prepared by straight synthesis, azides have the potential to
serve as a general type of N source in a variety of reactions.
Sulfonyl and phosphoryl azides have drawn much attention as
a result of their easy transformation to nitrenes or one-N-atom
sources upon the release of molecular N2 in CÀH bond amina-
tion[51,52] and ketenimine-intermediate-based multicomponent
reactions,[41–44] respectively. Oxysulfonyl azides (also called azi-
dosulfates), another class of reactive azides, have been much
less exploited in organic transformations, which might be be-
cause of a lack of appropriate methods for their synthesis. It
has been demonstrated by Zhang et al. that trichloroethoxysul-
fonyl azide (TcesN3) can be easily transformed to nitrenes with
the loss of N2.[53] This remarkable finding has encouraged us to
explore the reactivity of oxysulfonyl azides in the CuI-catalyzed,
three-component coupling of azides, alkynes, and amines,
which was originally developed by Chang et al.[41] We discov-
ered that a range of oxysulfonyl azides can be obtained simply
in moderate yields by the following procedure: a 1:1.1 mixture
of phenol and SO2Cl2 in the presence of one equivalent of pyri-
dine was stirred in dry CH2Cl2 at À788C followed by the addi-
tion of 1.5 equivalents of NaN3 [Eq. (1)].
Synthesis and characterization of Cu2I2(PDIN) and
Cu2I2(BTTP4)
It has been established by Finn et al. that flexible N-containing
tripodal ligands, which are based on a central tertiary amine
surrounded by three N-heterocycles such as triazoles, benzimi-
dazoles, and pyridines, can display a dramatic enhancement in
the reactivity in reactions catalyzed homogeneously by
CuI.[49,50] Chang et al. discovered that tris[(1-benzyl-1H-1,2,3-tria-
zol-4-yl)methyl]amine (TBTA) exhibited a significant rate en-
hancement in the synthesis of amidines.[44] Their remarkable re-
sults prompted us to examine the effect of N-based ligands on
the catalytic activity in three-component coupling reactions
with oxysulfonyl azides. Other than flexible ligands for homo-
geneous catalysis, we are interested to explore whether rigid
di- or tritopic ligands, which are typically composed of a ben-
zene core surrounded by two or three N-heterocycles (e.g., 3-/
4-pyridine), could be exploited as accelerating ligands
in heterogeneous transition-metal catalysis because
these rigid ligands have been widely applied in the
construction of porous MOFs. With the robustness of
MOFs, the rigid N-based ligands could not only stabi-
To explore the reactivity of oxysulfonyl azides, we performed
comparison tests on the reactions between phenylacetylene
(PhCCH), diisopropylamine ((iPr)2NH), and different azides, such
as p-tosyloxysulfonyl azide (TsOxy-N3), p-tosylsulfonyl azide (Ts-
N3), and diphenylphosphoryl azide (DPPA), in the presence of
10 mol% CuI in acetonitrile. To our delight, under the opti-
mized conditions (alkyne/azide/amine=1:1.2:1.2), the reaction
with TsOxy-N3 was accomplished within 10 min with 100%
conversion to form N-oxysulfonyl amidine 1 (Table 1, entry 1).
In comparison, the reaction with Ts-N3 yielded the correspond-
ing N-sulfonyl amidine 2 with a conversion of 62% in 10 min
(entry 2). After 1 h, the reaction with Ts-N3 achieved 100% con-
version. However, the reaction with DPPA was rather poor and
achieved only 24% conversion after 4 h. The molecular struc-
ture of 1 was determined by single-crystal X-ray crystallograph-
lize the oxidation state of the catalytically active metal center
CuI in the solid state but also maintained its potential reactivity
and dynamics.[45–48]
Based on the above concept, two MOFs, namely, Cu2I2(PDIN)
(PDIN=1,4-phenylene diisonicotinate) and Cu2I2(BTTP4), have
been synthesized based on the pyridine-containing ligands
PDIN and BTTP4, respectively. The orange-yellow Cu2I2(PDIN)
crystallites were obtained from the direct mixing of a CH3CN
solution of CuI and a CHCl3 solution of PDIN followed by stir-
ring at room temperature for 30 min. Single crystals suitable
for XRD analysis were obtained one week after layering
a CH3CN solution of CuI onto a CHCl3 solution of PDIN. The
crystal structure displays a closely packed 2D network in which
Cu2I2 ribbons are connected by the bridging PDIN ligand (Fig-
ure S2). The phase purity of the crystalline precipitates ob-
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Table 1. CuI-catalyzed three-component coupling reactions of oxysulfonyl
azides, alkynes, and amines.[a]
Entry RN3
Product
Conversion Isolated
[%] (t [min]) yield [%]
1
100 (10)
87
1
2
62 (10)
83 (20)
90 (30)
100 (60)
2
3
n.d.[b]
12 (30)
15 (60)
24 (4 h)
n.d.[b]
3
95 (10)
100 (30)
4
5
6
7
87
89
67
81
Figure 2. Characterization of Cu2I2(PDIN) (left) and Cu2I2(BTTP4) (right):
a,d) PXRD patterns; b,e) particle-size analyses; c,f) SEM images; scale
bars=1.0 and 5.0 mm, respectively.
4
5
6
7
100 (30)
100 (30)
100 (30)
van der Waals radii). The solvent-accessible voids amount to
43% of the unit-cell volume. In this work, we simplified the
synthetic procedure and prepared orange-yellow Cu2I2(BTTP4)
crystallites by the direct mixing of a CH3CN solution of CuI and
a CHCl3 solution of BTTP4. The PXRD patterns of the bulky
samples prepared in this way matched those of pure crystals
of Cu2I2(BTTP4) (Figure 2d). Particle-size analysis showed that
the average edge length is about 7.2 mm (Figure 2e). A typical
SEM image of Cu2I2(BTTP4) revealed block-like crystals with
particle sizes in the range 1–10 mm, which agrees with the par-
ticle-size analysis (Figure 2 f).
8
100 (30)
90
Quantitative amounts of Cu2I2(PDIN) and Cu2I2(BTTP4) crystal-
line products could be obtained by a simple and convenient
synthetic method in a one-pot reaction, which promotes their
applications in catalytic reactions.
8
[a] Reaction conditions: oxysulfonyl azide (0.3 mmol), phenylacetylene
(0.25 mmol), (iPr)2NH (0.3 mmol), CuI (0.025 mmol), CH3CN (0.5 mL); [b] Not
determined.
Comparison of the catalytic activity of CuI, Cu2I2(PDIN), and
Cu2I2(BTTP4)
To study the potential of Cu2I2(PDIN) and Cu2I2(BTTP4) as heter-
ogeneous catalysts in the three-component coupling reaction,
we compared their activities with the naked homogeneous CuI
by keeping Cu content the same (10 mol%). As the azide only
acts as a N source and variation of the alkyne component can
lead to the formation of various amidine compounds, we se-
lected three alkynes that contained different substituents for
comparison, namely, PhCCH, cyclohexyl acetylene (CyCCH), and
tert-butyl acetylene (tBuCCH). The optimized reactant ratio
under heterogeneous conditions is alkyne/azide/amine=1:1:1,
which is different to that of the homogeneous reaction with
tained by the direct mixing of CuI and PDIN solutions was de-
termined by powder XRD (PXRD) analysis (Figure 2a). Particle-
size analysis shows that the average edge length is approxi-
mately 0.4 mm (Figure 2b). SEM images of Cu2I2(PDIN) reveal
a flaky crystal with particle sizes in the range 0.1–1 mm (Fig-
ure 2c), which agrees with the particle-size analysis.
Cu2I2(BTTP4) has been prepared previously by our group.[45]
Its crystal structure features a polycatenated 3D framework
consisting of 2D (6,3) networks through inclined catenation,
and contains large 1D channels (9ꢂ12 ꢁ2, after considering the
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CuI but apparently more economic. Before the catalytic reac-
tions, the Cu2I2(PDIN) and Cu2I2(BTTP4) crystallites were dried
completely under vacuum until no further solvent loss was ob-
served from thermogravimetric analysis (Figures S1 and S4).
The results are summarized in Figure 3 and provide the follow-
ing important information about their catalysis: (i) Cu2I2(PDIN)
is relatively ineffective for N-oxysulfonyl amidine, and the con-
geneous catalyst CuI, which contains the same amount of Cu.
Furthermore, aggregation of crystallites during the reaction
makes catalysis ineffective. The surface catalytic reaction was
proved by IR and energy-dispersive X-ray spectroscopic (EDS)
examination of the Cu2I2(PDIN) crystallites after catalytic reac-
tions, which confirmed that no N-oxysulfonyl amidine products
could be detected inside the recycled catalyst either by the ob-
servation of S in the EDS spectra or by the presence of C=N vi-
brations in the IR spectrum (Figures S11, S12, and S19).
On the contrary, the single-crystal structural analysis of Cu2I2-
(BTTP4) revealed that there are 1D open channels of an effec-
tive size of 9ꢂ12 ꢁ2 inside the coordination framework, which
provide a platform for the catalytic reactions within the chan-
nels.[45] The PXRD patterns of the Cu2I2(BTTP4) crystallites after
catalytic reactions closely matched those of Cu2I2(BTTP4) single
crystals, which indicates the unchanged framework (Figure S8).
The average edge length of the Cu2I2(BTTP4) crystallites was re-
duced to approximately 3.2 mm, which may be explained by
the SEM observation that some of the Cu2I2(BTTP4) crystallites
fell apart into smaller particles (Figure S10). As the reactions go
on inside the crystal channels, it is understandable that the
Cu2I2(BTTP4) crystallites are smashed on exclusion of N2 from
TsOxy-N3.
With the development of MOFs as promising heterogeneous
catalysts, there is always a debate as to whether the catalytic
reactions proceed within the crystal voids.[1–8] To investigate
whether the catalytic transformation can proceed inside the
crystal pores or only on the external crystal surface of Cu2I2-
(BTTP4), we firstly performed selective accommodation experi-
Figure 3. Comparison of the catalytic behavior of CuI, Cu2I2(PDIN), and Cu2I2-
&
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(BTTP4). The selectivities towards PhCCH ( ), CyCCH ( ), and tBuCCH ( ).
1
ments of the alkyne substrates by H NMR spectroscopy. After
Cu2I2(BTTP4) was immersed in a 1:1 mixture of PhCCH and
CyCCH in CD3CN for 10 min, the molar ratio of these two al-
kynes changed to 0.73:1 (Figure 4), indicative of the selective
inclusion of aromatic alkyne PhCCH over the aliphatic alkyne
CyCCH, which is consistent with the selective vapor adsorption
of benzene over cyclohexane by the Cu2I2(BTTP4) framework
observed previously.[45] Similar results were obtained from an
immersion experiment of Cu2I2(BTTP4) in a 1:1 mixture of
version of the reactions with all of the alkynes was around
10%; (ii) CuI showed a similar activity for all of the alkynes, and
the conversion was in the range of 70–80%; (iii) Cu2I2(BTTP4)
performed differently with respect to the alkyne substrates.
For example, the conversion of the reactions of PhCCH,
CyCCH, and tBuCCH after 10 min was 96, 55, and 24%,
respectively.
Notably, negligible loss of the orange-yellow crystallites of
Cu2I2(PDIN) and Cu2I2(BTTP4) was detected, which testifies their
competence as heterogeneous catalysts. Thus, we employed
various physicochemical techniques to characterize the cata-
lysts before and after the reactions in an attempt to illustrate
the origin of their catalytic differences. For Cu2I2(PDIN) crystalli-
tes, the PXRD patterns measured after catalytic reactions dis-
closed that the crystallinity was retained (Figure S7). Addition-
ally, particle-size analysis showed that the average edge length
of the Cu2I2(PDIN) crystallites was enlarged to approximately
1.2 mm after catalytic reactions. Such a phenomenon could
also be seen from the SEM images (Figure S9), which suggest-
ed that the flaky crystals might undergo aggregation during
the catalytic reactions. From the single-crystal structural analy-
sis we know that Cu2I2(PDIN) is nonporous (Figure S2). There-
fore, the catalytic sites could only exist on the outer surface.
The fact that the catalytic reaction can only take place on the
outer surface accounts for the low activity of the Cu2I2(PDIN)
crystallites as a heterogeneous catalyst compared with homo-
Figure 4. Selective adsorption behavior of Cu2I2(BTTP4) determined by
1H NMR spectroscopy of a 1:1 mixture of PhCCH and CyCCH in CD3CN
a) before and b) after the immersion of Cu2I2(BTTP4).
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PhCCH and tBuCCH in CD3CN (Figure S6). We ascribed such se-
lective adsorption to the preferential host–guest interactions
between the pyridyl rings of the BTTP4 ligands and the phenyl
rings of the aromatic alkynes. This selective inclusion of alkyne
substrates by the porous Cu2I2(BTTP4) MOF not only confirmed
that the substrates could enter the pores of the MOF catalyst
but also explained the much faster rate of reaction with
PhCCH than that with CyCCH or tBuCCH.
catalytic reactions. This XPS result suggested that the recycled
Cu2I2(BTTP4) catalyst is still active for further reaction.
From the comparison of the catalytic results of the homoge-
neous catalyst CuI, nonporous, heterogeneous catalyst Cu2I2-
(PDIN), and porous, heterogeneous catalyst Cu2I2(BTTP4), we
may conclude that the porous Cu2I2(BTTP4) framework stands
out as a shape-selective catalyst because of the presence of
catalytic sites on the inner micropore surfaces and its hetero-
geneous catalytic activity is comparable with that of homoge-
neous CuI for aromatic alkyne substrates.
Secondly, we measured CO2 gas adsorption–desorption iso-
therms for the Cu2I2(BTTP4) crystallites before and after catalyt-
ic reactions (Figure S21). At 195 K, the amount of CO2 uptake
at 1 atm was 23.7 and 13.7 wt% before and after catalytic reac-
tion. The decrease of the adsorption capability of CO2 by the
Cu2I2(BTTP4) framework after catalysis might be caused by N-
oxysulfonyl amidine products that remain in the channels,
which might partially block the framework pores. Additionally,
we characterized Cu2I2(BTTP4) after catalytic reactions by IR,
EDS, and X-ray photoelectron spectroscopy (XPS). The IR spec-
trum disclosed the presence of C=N bonds of the amidine
products (Figure S20), and both EDS (Figure 5) and XPS
(Figure 6) confirmed the presence of S in the recycled catalyst
sample. XPS also verified that the valence (+1) of Cu2I2(BTTP4)
remained unchanged after the catalytic reactions, which was
ascertained by observation of the same two intense peaks at
932.5Æ0.2 and 952.5Æ0.2 eV assigned to Cu2p3/2 and Cu2p1/2
components for the Cu2I2(BTTP4) crystallites before and after
Catalytic performance of Cu2I2(BTTP4)
To explore the substrate scope of Cu2I2(BTTP4) as a heterogene-
ous catalyst, three-component reactions of TsOxy-N3, (iPr)2NH,
and different alkynes have been studied. To our delight,
a series of aromatic alkynes can take part in the catalytic reac-
tions, and the reactions could be finished in 30 min with good
yields (Table 2, entries 1–7). In all cases, N-oxysulfonyl amidines
were formed as the sole products, except in the reaction with
p-fluorophenylacetylene, in which a minor amount of oxysul-
fonyl triazole was obtained (entry 4). In contrast, N-oxysulfonyl
amidines were obtained with modest yields from the reactions
with alkyl alkynes (entries 8–13). In particular, the reaction with
the bulky alkyne tBuCCH gave amidine 10 in only 38% yield
(entry 9). With respect to functional group compatibility,
a range of functional groups, which includes halide, alcohol,
ether, and silyl groups, are tolerated in Cu2I2(BTTP4)-catalyzed
reactions. It is interesting that hydroxyl groups in the alkyne
substrates could even promote the reaction (entries 11 and
12),[54] which is in agreement with our previous observation
that the inclusion of polar alcohols by the Cu2I2(BTTP4) frame-
work is superior to the inclusion of cyclohexane.[45] Amines
other than (iPr)2NH, such as N-methylaniline (Ph(Me)NH) and
diphenylamine (Ph2NH), have also been tested, and the results
show that the reactivity is in the order of (iPr)2NH>
Ph(Me)NH>Ph2NH (entries 1 and 14). Only a trace amount of
amidine product could be detected from the reaction with
Ph2NH, which indicates that the basicity of the amine affects
the coupling significantly.
Figure 5. Elemental distribution of Cu2I2(BTTP4) after catalytic reactions
(2.12 keV, AuMa; 2.30 keV, SKa).
One remarkable feature of this catalysis is that Cu2I2(BTTP4)
crystallites can be easily isolated from the reaction suspension
by simple filtration alone and can be reused at least three
times without any loss in yield or chemoselectivity (Figure 7).
The PXRD patterns recorded for the recovered catalyst after
the three runs show no signs of framework collapse or decom-
position (Figure S8). Moreover, inductively coupled plasma op-
tical emission spectroscopic (ICP-OES) analysis of the reaction
filtrate indicates that the amount of Cu leached into the reac-
tion mixture is only 6.0% of the total Cu content in Cu2I2-
(BTTP4), which corresponds to 3.879 ppm. To eliminate the
possibility that the catalysis might be a result of the leached
Cu in the solution, a new batch of starting materials, TsOxy-N3
(0.25 mmol), PhCCH (0.25 mmol), and (iPr)2NH (0.25 mmol), was
added to the filtrate. After 1 h, a negligible amount of amidine
was detected by in situ 1H NMR spectroscopic monitoring,
Figure 6. XPS spectra of Cu2I2(BTTP4) before (top) and after (bottom) catalyt-
ic reactions. MNN=initial vacancy in the M shell and final double vacancy in
the N shell; LMM=initial vacancy in the L shell and final double vacancy in
the M shell.
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Table 2. Three-component coupling reactions of oxysulfonyl azides, al-
kynes, and amines catalyzed by Cu2I2(BTTP4).[a]
Entry Alkyne
Product
Conversion Isolated
[%]
yield [%]
1
96
92
Figure 7. Recycling experiments for Cu2I2(BTTP4).
1
2
3
4
5
6
93
74
89
82
66
87
which confirms that heterogeneous Cu2I2(BTTP4) was responsi-
ble for the catalytic performance.
11
12
13
14
93
Conclusions
We have developed a new protocol for the synthesis of N-oxy-
sulfonyl amidines with satisfactory yields from the three-com-
ponent coupling reactions of oxysulfonyl azides, alkynes, and
amines in the presence of the homogeneous CuI or heteroge-
neous Cu2I2(BTTP4) catalysts. As a result of the presence of
large, open channels in the Cu2I2(BTTP4) framework, the reac-
tants could enter the pores and undergo reactions in the inner
cavities, which endowed porous Cu2I2(BTTP4) with shape-selec-
tive catalytic activity. This hypothesis has been proved directly
and indirectly by the substrate adsorption of aromatic alkynes
in solution and the observation of N-oxysulfonyl amidine prod-
ucts in the catalyst sample after catalytic reactions. As an effi-
cient heterogeneous catalyst, the porous Cu2I2(BTTP4) crystalli-
tes could be recycled and used in three runs without signifi-
cant loss of activity. Further investigations on the catalytic ap-
plications of Cu2I2(BTTP4) towards more organic reactions are
in progress.
93[b]
75[c]
92
15
16
7
8
77
58
66
48
9
9
44
75
81
63
88
38
60
68
53
64
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18
19
20
Experimental Section
10
11
12
13
General
Unless otherwise stated, all commercial reagents and solvents
were used without additional purification. 1H, 13C, and 19F NMR
spectra were recorded by using Varian/Mercury-Plus (300 MHz) or
Bruker AVANCE III (400 MHz) spectrometers. IR spectra were record-
ed by using a Nicolet Nexus-670 FTIR spectrometer with KBr pellets
in range 4000–400 cmÀ1. PXRD patterns were recorded by using
a Bruker D8 Advance diffractometer at 40 kV and 40 mA with a Cu-
target tube and a graphite monochromator. X-ray intensity data
were collected by using an Oxford Diffraction Xcalibur Onyx Nova
diffractometer using CuKa1 radiation (l=1.54184). ICP-OES was
conducted by using a Spectro Ciros Vision ICP-OES spectrometer
equipped with vacuum optics that cover the spectral range from
14[d]
63[e]
40
175–777 nm, plasma power, 1300 W; coolant flow, 15.00 LminÀ1
;
21
auxiliary flow, 0.80 LminÀ1; nebulizer 0.70 LminÀ1. ESI-MS was per-
formed by using a AccuTOF CS JMS-T100CS spectrometer. HRMS
were recorded by using a MAT95XP instrument by using the EI
method or a maxis 4G ESI-Q-TOF instrument by using the ESI
method. The sorption isotherms of Cu2I2(BTTP4) for CO2 (195 K)
were performed by using a Micromeritics ASAP 2020 instrument.
[a] Reaction conditions: TsOxy-N3 (0.25 mmol), alkyne (0.25 mmol),
(iPr)2NH (0.25 mmol), Cu2I2(BTTP4) (0.0125 mmol), CH3CN (0.5 mL);
[b] Conversion in 60 min, and 7% triazole was found; [c] Conversion in
60 min; [d] PhNHMe was used instead of (iPr)2NH, and Et3N (1 equiv.) was
added; [e] Conversion in 6 h.
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Prior to the sorption examination, the samples were prepared
under vacuum at 358C for 16 h. Thermogravimetric (TG) analyses
were performed under an N2 atmosphere at a heating rate of
108CminÀ1 by using a NETZSCH TG 209 system. XPS spectra were
measured by using a Thermo-VG Scientific ESCALAB 250 spectrom-
eter under a pressure of ꢀ2ꢂ10À9 mbar with X-ray monochromat-
ized AlKa radiation (15 kV, 150 W, spot size=500 mm). SEM images
and the elemental distribution of Cu2I2(PDIN) and Cu2I2(BTTP4)
were obtained by using a JSM-6330F field emission scanning elec-
tron microscope combined with EDS. Prior to examination, the
compounds were coated with a thin layer of Au. The particle sizes
were measured by using a MasterSizer 2000 Analyzer.
33.60, H 1.82, N 5.04, Cu 14.28; found: C 33.73, H 2.20, N 5.15, Cu
14.00 (ICP-OES).
[Cu2I2(BTTP4)]·0.5CHCl3·0.2CH3CN was dried under high vacuum for
16 h at 358C to give the solvent-free complex with an empty
framework, Cu2I2(BTTP4). IR (KBr): n˜ =3040, 2920, 2850, 1750, 1606,
1561, 1455, 1431, 1323, 1252, 1210, 1132, 1080, 1059, 896, 848,
754, 695, 660, 585 cmÀ1. Phase purity was verified by powder XRD.
Typical procedure for the three-component coupling reac-
tions catalyzed by CuI
Under a N2 atmosphere, to a mixture of phenylacetylene (27.5 mg,
0.25 mmol, 1 equiv.), TsOxy-N3 (63.9 mg, 0.3 mmol, 1.2 equiv.), and
CuI (4.75 mg, 0.025 mmol, 10 mol%) in CH3CN (0.5 mL) was slowly
added diisopropylamine (42 mL, 0.3 mmol, 1.2 equiv.). The whole re-
action mixture was allowed to stand at RT for 30 min. The organic
solvent was removed by reduced pressure. The remaining solid
mixture was treated by adding CH2Cl2 (3 mL) and aqueous NH4Cl
solution (2 mL). The two layers were separated, and the aqueous
layer was extracted with CH2Cl2 (3 mLꢂ3). The combined organic
layers were dried over Na2SO4, filtered, and concentrated under re-
duced pressure. The crude residue was purified by flash column
chromatography with an appropriate eluting solvent system. The
pure product of N1,N1-diisopropyl-N2-(4-methylbenzeneoxysulfon-
yl)-2-phenylacetamidine (1) was obtained as an off-white solid.
Yield=84.7 mg, 87%; Rf =0.45 (EtOAc/hexane, 1:3); m.p.: 96–978C;
1H NMR (300 MHz, CDCl3): d=7.33–7.15 (m, 7H), 7.10 (d, J=8.3 Hz,
2H), 4.29 (s, 2H), 4.02 (dt, J=13.2, 6.6 Hz, 1H), 3.47 (brs, 1H), 2.32
(s, 3H), 1.38 (d, J=6.6 Hz, 6H), 0.89 ppm (d, J=6.6 Hz, 6H);
13C NMR (75 MHz, CDCl3): d=165.58, 148.86, 135.38, 134.39, 129.65,
128.83, 127.83, 126.88, 121.42, 51.19, 48.72, 38.55, 38.48, 20.94,
19.67 ppm; IR (KBr): n˜ =3085, 3029, 3011, 2982, 2966, 2932, 2872,
1549, 1521, 1502, 1472, 1457, 1438, 1374, 1317, 1271, 1193, 1159,
1132, 1053, 1018, 950, 857, 830, 817, 787, 754, 718, 691, 639, 618,
577, 548, 519, 479, 462 cmÀ1; HRMS (EI): m/z: calcd for C21H28N2O3S:
388.1815 [M+]; found: 388.1816.
Synthesis of oxysulfonyl azides
The synthesis of oxysulfonyl azides was achieved by using a similar
procedure to that of TsOxy-N3 as follows: A solution of p-cresol (p-
CH3C6H4OH; 1.08 g, 10 mmol) and pyridine (0.81 mL, 10 mmol) in
dry CH2Cl2 (11 mL) was added dropwise to a solution of SO2Cl2
(0.89 mL, 11 mmol) in dry CH2Cl2 (10 mL) at À788C under N2. The
mixture was allowed to warm to RT and stirred overnight. After the
reaction was complete, all of the solvent was removed by rotary
evaporation. The residue was dissolved in CH3CN (10 mL), and the
solution was stirred at 08C for 15–20 min. Sodium azide (0.975 g,
15 mmol) was added to the mixture in six portions, and the reac-
tion mixture was allowed to warm to RT and stirred overnight.
After the reaction was complete, the crude product was filtered
through Celite and washed with EtOAc (ethyl acetate) until all the
product was washed out. The filtrate was collected and concentrat-
ed by rotary evaporation. The crude product was dissolved in
ether and washed with aqueous NaOH solution (0.1m) and brine,
dried over sodium sulfate, and concentrated by rotary evaporation.
The resulting oil was then purified by flash chromatography (silica
gel). Yield=0.92 g, 43%; Rf =0.48 (EtOAc/PE=1/20); 1H NMR
(300 MHz, CDCl3): d=7.24 (d, J=0.8 Hz, 4H), 2.40 ppm (s, 3H);
13C NMR (75 MHz, CDCl3): d=147.51, 138.26, 130.53, 121.07, 20.93,
20.88 ppm; IR (KBr): n˜ =2923, 2852, 2147, 1501, 1416, 1179, 1142,
1018, 883, 804, 765, 641, 623, 581, 552 cmÀ1
.
Typical procedure for the three-component coupling reac-
tions catalyzed by Cu2I2(BTTP4)
Synthesis of Cu2I2(PDIN)
To CH3CN (0.5 mL) in a vessel was added Cu2I2(BTTP4) (10.2 mg,
0.012 mmol, 10 mol% based on Cu), phenylacetylene (27.5 mg,
0.25 mmol, 1 equiv.), and TsOxy-N3 (53.3 mg, 0.25 mmol, 1 equiv.)
A solution of CuI (68.4 mg, 0.36 mmol) in CH3CN (8 mL) was added
dropwise over 15 min to a solution of PDIN (57.6 mg, 0.18 mmol)
in CHCl3 (8 mL).The mixture was stirred for 30 min at RT. The pre-
cipitates were collected by filtration through Celite (P4), washed
with CHCl3/CH3CN (1:1, 2 mLꢂ3), and dried under vacuum. The
product was obtained as a yellow precipitate. Yield=111 mg, 88%;
elemental analysis calcd (%) for Cu2I2C18H12N2O4 (Cu2I2(PDIN): C
30.83, H 1.72, N 4.00; found: C 30.60, H 1.88, N 3.90; IR (KBr): n˜ =
3084, 3049, 1742, 1503, 1414, 1323, 1272, 1173, 1101, 1093, 1062,
1017, 896, 854, 810, 755, 698, 677, 524 cmÀ1. Phase purity was veri-
fied by powder XRD.
under
a N2 atmosphere. Diisopropylamine (35 mL, 0.25 mmol,
1 equiv.) was added slowly to the vessel. The whole reaction mix-
ture was allowed to stand at RT. After the reaction was complete,
the supernatant was filtered through a thin pad of Celite (P4) and
washed by CH3CN (0.5 mLꢂ3). The organic solvent was removed
under reduced pressure followed by flash chromatography. Pure
1 was obtained as an off-white solid. Yield=89.3 mg, 92%.
Crystal structure determination
Diffraction data for Cu2I2(PDIN), 1, 9, and 10 were collected by
using an Oxford Gemini S Ultra diffractometer equipped with CuKa
radiation (l=1.54178 ꢁ) at 150 K by using f and w scans. Structur-
al solution and refinement against F2 were performed with SHELXL
programs.[55] Anisotropic thermal factors were assigned to all of the
non-hydrogen atoms. The positions of the hydrogen atoms were
generated geometrically, assigned isotropic thermal parameters,
and allowed to ride on their respective patent atoms before the
final cycle of least-squares refinement.
Synthesis of Cu2I2(BTTP4)
A solution of CuI (68.4 mg, 0.36 mmol) in CH3CN (8 mL) was added
dropwise over 15 min to a solution of BTTP4 (79.4 mg, 0.18 mmol)
in CHCl3 (8 mL). The mixture was stirred for 30 min at RT. The pre-
cipitates were collected by filtration through Celite (P4) and
washed by CHCl3/CH3CN (1:1, 2 mLꢂ3). The product was obtained
as a yellow powder. Yield=156 mg, 96%; elemental analysis calcd
(%) for Cu2I2Cl1.5C25.1H16.4N3.3O6 ([Cu2I2(BTTP4)]·0.5CHCl3·0.2CH3CN): C
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Acknowledgements
This work was supported by the 973 Program (2012CB821701)
and NSF Projects (21102186, 21121061, 91222201, 21173272, and
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Keywords: azides · copper · heterogeneous catalysis · metal–
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