Arylhydrazone ligands as Cu-protectors and -catalysis promoters in the azide-alkyne cycloaddition reaction

Article abstract of DOI:10.1039/c8dt04771e

A series of water soluble copper(ii) complexes, [Cu(κO¹O²N-H₂L¹)(H₂O)₂]·2H₂O (2), [Cu(κO-H₃L¹)₂(H₂O)₄] (3), [Cu(κO-H_4<

Full text of DOI:10.1039/c8dt04771e

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Arylhydrazone ligands as Cu-protectors and
catalysis promoters in the azide–alkyne
-
Cite this: DOI: 10.1039/c8dt04771e
cycloaddition reaction†
a,b
a
Abdallah G. Mahmoud,
Kamran T. Mahmudov
M. Fátima C. Guedes da Silva,
*
*
a,c
a
*
and Armando J. L. Pombeiro
1
2
1
1
A series of water soluble copper(II) complexes, [Cu(κO O N-H
(
2
L )(H
NCHO (7), were prepared by the reaction of
O with sodium (Z)-2-(2-(1-amino-1,3-dioxobutan-2-ylidene)hydrazineyl)benzenesulfonate,
2
O)
2
]·2H
2
O (2), [Cu(κO-H
3 2 2 4
L ) (H O) ]
2
3
4 2 2 4 2 6 2 3 2
3), [Cu(κO-H L ) (H O) ] (5) and [Cu(H O) ]·2H L ·2(CH )
Cu(NO
Na(μ
3
)
2
·3H
2
1
2
3
4
1
[
4
-1:2κO ,2κO ,3κO ,4κO -H
3
L )]
n
(1; for 2 and 3), sodium (Z)-3-(2-(1-amino-1,3-dioxobutan-2-
1
2
2
4 2
ylidene)hydrazineyl)-4-hydroxybenzene-sulfonate, [Na(μ-1κO ,2κO -H L )] (4; for 5) or sodium (Z)-2-(2-
1,3-dioxo-1-(phenylamino)butan-2-ylidene)hydrazineyl)naphthalene-1-sulfonate, [Na(μ-1κO O ,2κO -
1
2
3
(
3
H
2
L )(CH
3
OH)
2
]
2
(6; for 7). Compounds 1–7 were fully characterized, also by single-crystal X-ray diffrac-
tion analysis, and applied as homogeneous catalysts for the azide–alkyne cycloaddition (AAC) reaction to
afford 1,4-disubstituted 1,2,3-triazoles. A structure–catalytic activity relationship has been recognized for
the first time on the basis of the occurrence of resonance- and charge-assisted hydrogen bond inter-
actions (RAHB and CAHB), in charge and ligand binding modes, enabling the catalytic activity of the com-
pounds to be ordered as follows: Cu(NO ) ≪ 7 (complex salt with RAHB and CAHB) < 3 (with RAHB and
CAHB) < 5 (with RAHB) < 2 (neither RAHB nor CAHB). Complex 2, without such non-covalent interactions,
was found to be the most efficient catalyst for the AAC reaction, affording up to 98% product yield after
being placed for 15 min, at 125 °C, in a water/acetonitrile mixture under low power (10 W) MW irradiation.
Received 3rd December 2018,
Accepted 4th January 2019
3
2
DOI: 10.1039/c8dt04771e
rsc.li/dalton
of the 1,4- and 1,5-regioisomers (Scheme 1). The catalytic 1,3-
dipolar cycloaddition reaction of azides and terminal alkynes
1
. Introduction
The azide–alkyne cycloaddition (AAC) reaction (or the Huisgen by copper(I) or ruthenium(II) complexes can be completely
1
1
1
,3-dipolar cycloaddition reaction) leading to the formation of regioselective and represents a powerful method for the rapid
4
,4- or 1,5-disubstituted 1,2,3-triazole derivatives (Scheme 1) assembly of 1,4-disubstituted-1,2,3-triazoles
has been extensively studied in recent years due to the indus- substituted-1,2,3-triazoles. The metal complex catalyzed AAC
trial applications of such products as dyes, corrosion inhibi- reaction fulfils the “click criteria”
tors, photostabilizers and agrochemicals, in addition to their ditions of quantitative yields, regioselective conversions, pro-
antiparasitic, antiplatelet, anticancer, antimicrobial, antima- gression under mild conditions with high rates in benign sol-
larial, anti-inflammatory, and HIV-1 reverse transcriptase vents, modularity, broadness of scope, simple work-up or puri-
or 1,5-di-
5
1
c,d
since it meets the con-
2
3
4b,6–9
inhibitory properties, among others. The non-catalyzed 1,3- fication steps, etc.
In comparison with the use of other
dipolar cycloaddition of organic azides and alkynes is usually metal complexes, the Cu(I)-promoted AAC reaction has been
slow, requires an elevated temperature and affords a mixture largely explored because the method is cheap and easy to
4
handle and provides virtually quantitative yields.
There have been several reports of using a Cu(II) species for
catalyzing the AAC without adding any reducing agent or
a
Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa,
Av. Rovisco Pais, 1049-001 Lisboa, Portugal.
E-mail: fatima.guedes@tecnico.ulisboa.pt, pombeiro@tecnico.ulisboa.pt
b
Department of Chemistry, Faculty of Science, Helwan University, Ain Helwan,
1
1795 Cairo, Egypt
c
Department of Chemistry, Baku State University, Z. Xalilov Str. 23, Az 1148 Baku,
Azerbaijan. E-mail: kamran_chem@mail.ru, kamran_chem@yahoo.com
†
Electronic supplementary information (ESI) available. CCDC 1857654, 1857660,
857658, 1857655, 1857656, 1857657 and 1857659. For ESI and crystallographic
1
data in CIF or other electronic format see DOI: 10.1039/c8dt04771e
Scheme 1 1,3-Dipolar cycloaddition of organic azides and alkynes.
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8
e,9a,g–p
base.
(
The first example of using solely a Cu(II) salt the compounds, measured in the solid state, with their cata-
9
g
copper acetate) for the AAC reaction was reported in 2006,
evidencing the relevant direct participation of Cu(II) in this
catalytic process.
mechanistic and DFT studies
complexes clearly showed that Cu(I) species are generated in a
short induction period from alkyne–alkyne homocoupling
known as the Glaser reaction), and are responsible for the Sodium salts of (Z)-2-(2-(1-amino-1,3-dioxobutan-2-ylidene)
progress of the AAC reaction.
The role of the ligands as stabilizers of the copper oxidation H L )] (1), (Z)-3-(2-(1-amino-1,3-dioxobutan-2-ylidene)hydrazi-
state, modulating and increasing the reactivity, has also been neyl)-4-hydroxybenzenesulfonate, [Na(μ-1κO ,2κO -H L )] (4)
revealed.
Oxygen-based and mixed N,O-ligands have scarcely been zineyl)naphthalene-1-sulfonate,
investigated for the AAC reactions, where most of the reported (CH OH) ] (6) (Scheme 2), were prepared by the Japp–
lytic performances.
4
b,9q
Thereafter, several spectroscopic,
8
e,9r–t
on different Cu(II) salts and
2
. Results and discussion
2.1. Synthesis and characterization of compounds 1–7
9
u
(
1
2
3
4
hydrazineyl)benzenesulfonate, [Na(μ -1:2κO ,2κO ,3κO ,4κO -
4
1
3
n
1
2
2
4
2
1
0a
and (Z)-2-(2-(1,3-dioxo-1-(phenylamino)butan-2-ylidene) hydra-
1
2
3
3
[Na(μ-1κO O ,2κO -H L )
2
3
2 2
1
0b
10f–i
examples were found to be inactive,
require an inert atmo- Klingemann method
by the reaction of aryldiazonium
In chlorides and β-diketones (3-oxobutanamide or 3-oxo-N-phe-
addition, the development of the Cu-catalysed 1,3-dipolar nylbutanamide) in
sodium hydroxide water solution.
cycloaddition reaction in water instead of an organic solvent Reaction of 1 with Cu(NO ) ·3H O in a water–acetone (1 : 5)
1
0c
10d
sphere
or use a stoichiometric amount of metal.
a
3
2
2
4
b,9
will contribute to a cleaner green chemistry process.
However, catalytic processes in water medium require water- leads to [Cu(κO O N-H L )(H O) ]·2H O (2) or [Cu(κO-
soluble metal catalysts having suitable ligands, e.g., with H L ) (H O) ] (3), respectively (Scheme 2). Treatment of 4 or 6
mixture in the presence or absence of NH OH solution (pH 9)
4
1
2
1
2
2
2
2
1
3
2
2
4
hydrophilic functionalities.
with the same copper salt in a MeOH/MeCN (1 : 2) mixture or a
2
Arylhydrazones of active methylene compounds (AHAMCs) DMF/MeOH (1 : 20) mixture produces [Cu(κO-H L ) (H O) ] (5)
functionalized with carboxylic or sulfonic group(s) have effec- or [Cu(H O) ]·2H L ·2(CH ) NCHO (7), in this order. The com-
4
2
2
4
3
2
6
2
3 2
tively served as versatile ligands in the synthesis of water- pounds were characterized by elemental analysis, ESI-MS, IR
soluble copper(II) complexes, thereafter applied as catalysts in spectroscopy and single crystal X-ray diffraction (see below).
oxidation and C–C coupling reactions in aqueous They are soluble in water and DMSO and are insoluble in
1
0e–i
medium.
In pursuit of such research work, in this paper NCMe or chlorinated solvents; the pro-ligands 1, 4, and 6 and
we focused on the synthesis of novel water-soluble Cu(II)- complex 5 are soluble in MeOH, the latter being also soluble
AHAMCs complexes with the hydrazone ligands holding a in DMF as in the case of 2 and 3.
sulfonic group (Scheme 2), their full characterization and the
study of their catalytic activity towards the 1,3-dipolar cyclo- in the hydrazone form, as reported for analogues.
addition reaction under MW irradiation. We observed an un- fact, H-NMR spectra of 1, 4 and 6 in DMSO-d solution at
Compounds 1, 4 and 6 are stabilized in DMSO-d solution
6
1
0e–i
In
1
6
precedented relationship between resonance- and charge- room temperature show only one signal at δ 14.58, 14.68 and
assisted hydrogen bonds (RAHB and CAHB, respectively) of 14.88 respectively, which is assigned to the proton bound to
Scheme 2 Synthesis of water-soluble copper(II) complexes.
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the nitrogen atom adjacent to the aryl unit (vN–NH– hydra- 1652 cm−1) as compared to 6 (3198 and 1648 cm−1). The fol-
zone form). The chemical shifts at ca. 14 ppm are character- lowing ESI-MS fragmentation peaks were identified: m/z =
1
−
+
istic of resonance assisted hydrogen bonds (RAHB), while 284.0 [H
the weak N–H⋯O bonds are known to display the δN–H [Cu(H O)
3
L ] (for 1), 383.9 [Mr − 2H
2
O + H] (for 2), 67.8
2
+
1 −
2 −
2
4
]
3 4
and 284.2 [H L ] (for 3), 300.0 [H L ] (for 4),
1
0e–i
2+
2 −
3 −
values at the δ range of 7–9 ppm.
In the IR spectra, the 67.8 [Cu(H O) ] and 300.2 [H L ] (for 5), 410.3 [H L ]
2
4
4
2
−
1
2+
3 −
ν(N–H) and ν(CvO) vibrations of 2 (3183 and 1603 cm
)
(for 6) and 85.8 [Cu(H
2
O)
6
]
2
and 410.5 [H L ] (for 7),
−
1
and 3 (3108 and 1638 cm ) are significantly shifted in accounting for the existence of ionic species in solution,
relation to the corresponding signals of 1 (3138 and under ESI-MS conditions. Elemental analysis and X-ray crys-
tallography results (Fig. 1) are also in agreement with the
relative to 4 (3080 and 1606 cm ) and for 7 (3241 and proposed formulations.
1
−1
1
657 cm− ), the same occurring for 5 (3193 and 1599 cm
)
−
1
Fig. 1 Ellipsoid plots of 1–7 (drawn at the 30% probability level) with partial atom numbering schemes. The protons of the coordinated methanol in
6
and the DMF molecule in 7 are omitted for clarity. Intramolecular H-bond interactions are shown as dashed blue lines with the O(or N)⋯H dis-
tances in Å. Symmetry operations to generate equivalent atoms: (i) 2 − x, −y, 1 − z; (ii) 2 − x, −y, 2 − z; (vii) 1 + x, y, z (1; see also Fig. S1†). (i) −x, 1 − y,
− z (3). (i) 1 − x, −y, 2 − z (4). (i) 2 − x, 1 − y, 1 − z (5). (i) 1 − x, −y, 1 − z (6). (i) 2 − x, −y, 1 − z (7).
1
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.2. Single crystal X-ray diffraction analysis
2.3. Catalytic activity
The catalytic activities of compounds 1–7 were tested for the
,3-dipolar cycloaddition of ethynylbenzene with benzyl
bromide in the presence of NaN (Scheme 3) under microwave
Single crystal X-ray diffraction analysis revealed that the Cu(II)
compounds are all monomeric with the metal cations present-
ing square pyramidal (2, τ = 0.14) or octahedral (3, 5) geome-
tries, while those of Na(I) are dimeric (4 and 6) or polymeric
1
3
5
irradiation in a H
2
O/MeCN (v/v, 1/1) mixture and at 125 °C
(
Table 1, entries 1–7). No reaction takes place in the absence of
(
1), with the metals displaying distorted trigonal bipyramid (1,
τ5 = 0.67) or almost perfect square pyramidal conformations
= 0.03 (4), 0.00 (6)]. The compounds have all-O settings
any metal species or under solvent-free conditions, even in the
presence of the arylhydrazone sodium salts 1, 4 and 6 (Table 1,
entries 1, 4 and 6). In contrast, the Cu(II) complexes 2, 3, 5 and
[τ
5
around the cations, except 2 where the hydrazone ligand is
deprotonated and forces the metal to present a NO , instead of
7
are active catalysts for the reaction under study to afford 1,4-
4
disubstituted 1,2,3-triazoles, but their catalytic activities
strongly depend on their structures, the former being the most
active and the latter the least active one (Table 1, compare
entries 2, 3, 5 and 7). Only a small amount of 1-benzyl-4-
an all-O, coordination environment. In the remaining com-
pounds the hydrazone ligands are not deprotonated, the posi-
tive charges of the metals being balanced exclusively by the
sulfonate-centered negative charge (Scheme 2 and Fig. 1). In
the 2D polymeric structure of 1 the hydrazone is the sole
ligand with the three Osulfonate atoms and the Oamide, engaged
in coordination to Na(I). For the remaining compounds, water
(
in 2–5) or methanol molecules (in 6) are co-ligands.
2
+
Complexes 3 and 5 hold the {Cu (H O) } unit, connecting two
2
4
organic ligand moieties; however, in the former such binding
of L to the cation is through the Oamide oxygen, and in the
Scheme 3 Microwave assisted 1,3-dipolar cycloaddition of alkynes with
3
substituted benzyl bromides in the presence of NaN and a catalyst.
latter it is through the Osulfonate
.
The NN distances (Table S2,† ca. 1.30 Å) are typical single
bonds. The M–Oamide bond distances (ca. 2.30–2.32, Table S2†)
are shorter than the M–Osulfonate ones (between 2.33 and
Table 1 Optimization of the parameters of the 1,3-dipolar cyclo-
addition reaction between ethynylbenzene and benzyl bromide in the
2
.39 Å), except for 1 where the reverse is detected (Table S2†).
a
presence of NaN
3
with 1–7 as catalysts
Probably resulting from deprotonation of the ligand, com-
pound 2 is the one that presents the shortest M–O bonds invol-
ving that species.
The compounds show several medium to strong intra- and
intermolecular hydrogen bond interactions (Table S3 and
Fig. S1–S7†), in particular those presenting coordinated water
Amount of
catalyst
(mol%)
b
c
Time Yield
(min) (%)
Entry Catalyst
Solvent
H O : MeCN
1
2
3
4
5
6
7
8
9
1
1
1
1
2
3
4
5
6
7
—
3
3
3
3
3
3
3
—
—
3
1
5
3
3
3
3
3
3
3
3
3
3
3
3
3
2
15
15
15
15
15
15
15
15
15
15
15
15
15
15
5
—
2
H O : MeCN
2
H O : MeCN
2
H O : MeCN
80.3
50.4
—
66.4
—
29.6
—
—
(
2–5 and 7) or methanol (6) molecules. Despite the use of a
strong base in the syntheses of the arylhydrazone species (see
the Experimental), the RAHB, Resonance-Assisted Hydrogen
Bond, involving the hydrazone hydrogen interaction with the
O-sulfonate and/or O-carbonyl moiety, is presented in 1, 4
and 6 (Scheme 2). In these RAHB systems the N⋯O distances
of (Table S3†) 2.823 and 2.602 (for 1), 2.570 (for 4) and
H O : MeCN
2
2
H O : MeCN
2
H O : MeCN
2
H O : MeCN
—
Cu(NO
Solvent free
0
1
2
3
)
2 2
·3H O
2
H O : MeCN
2
H O : MeCN
2
H O : MeCN
7.2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
34.8
80.3
61.9
78.1
51.2
80.4
74.1
11.7
55.6
57.8
60.0
63.3
66.4
d
e
2
.640 Å (for 6) confirm strong intramolecular donor–acceptor 13
2
H O : MeCN
1
1
1
1
1
4
5
6
2
H O : MeCN
2
H O : MeCN
2
H O : MeCN
interactions (Fig. 1).
4
The added NH OH conceivably
weakens the RAHB systems in 1 on its reaction with
30
15
15
Cu(NO ) ·3H O in a water–acetone (1 : 5) mixture, leading to 17
H O
3
2
2
2
1
1
2
8
9
0
MeCN
deprotonation of the hydrazone and affording 2. In the
absence of NH OH the copper(II) complex 3 is obtained,
H
H
2
O : Dioxane 15
O : BuOH 15
4
t
2
i
which has both RAHB and CAHB (Charge-Assisted Hydrogen 21
2
H O : PrOH
15
15
15
15
22
23
24
H
H
2
O : EtOH
Bond) systems with donor⋯acceptor distances of 2.603 and
.037, respectively. The RAHB systems of the sodium salts of
2
O : MeOH
3
Solvent free
H O : MeCN
2
Traces (<5)
f
arylhydrazones 4 and 6 (also CAHB for this latter one) were 25
24 h 51.3
not destroyed by interaction with the Cu(II) salt to give 5 and
a
Reaction conditions: Ethynylbenzene (0.33 mmol, 1.1 equiv.), benzyl
bromide (0.30 mmol, 1 equiv., limiting reactant), sodium azide
7
(Scheme 2 and Fig. 1), in this order, although with a slight
weakening when going from 4 to 5, and a strengthening (0.33 mmol, 1.1 equiv.), 1.5 mL of solvent (1 : 1 in the case of solvent
b
mixtures), MW irradiation (10 W), 125 °C. Calculated on the basis of
when comparing 6 and 7. In contrast, the CAHB interaction
in 7 is stronger than that in 6 (2.668 versus 2.639 Å,
Table S3†).
c
benzyl bromide. Isolated yield; calculated on the basis of benzyl
d
e
bromide. Reaction performed at 70 °C. Reaction performed at
f
150 °C. Reaction performed under conventional heating (100 °C).
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phenyl-1H-1,2,3-triazole (7.2%) was obtained in the presence Table 2 1,3-Dipolar cycloaddition of ethynylbenzene or 1,4-diethynyl-
benzene with substituted benzyl bromides in the presence of NaN
alysed by 3 mol% of 2
3
cat-
of Cu(NO ) ·3H O under the same reaction conditions
3
2
2
a
(Table 1, entries 8–10). Using 2 as a catalyst for the reaction
under study, the increase of its loading up to 3 mol% resulted
in a marked yield improvement (Table 1, entries 2, 11 and 12)
but further increase of the amount had no effect. The tempera-
ture of 125 °C is considered the best for the reaction (Table 1,
compare entries 2, 13 and 14) as well as the reaction time of
b
Entry
1
Product
Yield , %
97
1
5 min (Table 1, compare entries 2, 15 and 16). Using MeCN
2
98
as the sole solvent had an inhibiting effect possibly due to the
lack of solubility of NaN and of the catalyst in this solvent
3
3
4
99
82
(Table 1, entry 18). With water alone we obtained compara-
tively better yields, but utilizing a water : MeCN mixture led to
higher conversions, probably as a result of enhancement of
reactant miscibility (Table 1, entries 2 and 17). Apart from
MeCN several other organic co-solvents have been tested viz.
5
6
77
86
t
i
dioxane, BuOH, PrOH, EtOH and MeOH (Table 1, entries 2
and 19–23), with the H O/dioxane mixture falling well below
the others (56% yield, Table 1, entry 19) and the H O/MeCN
revealing to be the best combination (80% yield, Table 1, entry
). The 1,3-dipolar cycloaddition does not occur under solvent-
2
2
2
free conditions (Table 1, entry 24), whereas conventional
heating (oil bath, 100 °C) hampers the reactions in comparison
with MW irradiation (Table 1, entry 25) in the presence of cata-
lyst 2.
Under the above optimized experimental conditions, we
explored the versatility of catalyst 2 for the 1,3-dipolar cyclo-
addition of ethynylbenzene or 1,4-diethynylbenzene with sub-
7
88
8
9
91
75
stituted benzyl bromides in the presence of NaN , and the
3
results are summarized in Table 2. All the substrates produced
the expected 1,4-disubstituted 1,2,3-triazoles in good to excel-
lent yields and selectivity. The presence of the strong electron-
acceptor nitro group at the phenyl group of benzyl bromide
enhances the reaction (97% yield versus 80%, entry 1 of
Table 2 versus entry 2 of Table 1), but its position (ortho, meta equiv. or 0.63 mmol, 2.1 equiv.), 1.5 mL H O/MeCN (1 : 1), MW
or para) appears to have no effect on the yield of the corres-
ponding 1,4-disubstituted 1,2,3-triazole (Table 2, entries 1–3).
a
Reaction conditions: 3.0 mol% of catalyst 2, ethynylbenzene
(
0.33 mmol, 1.1 equiv.) or 1,4-diethynylbenzene (0.33 mmol, 1.1
equiv.), substituted benzyl bromides (0.30 mmol,
1 equiv. or
0
.60 mmol, 2 equiv., limiting reactant), sodium azide (0.33 mmol, 1.1
2
b
irradiation (10 W), 125 °C, 15 min. Isolated yield; calculated on the
basis of substituted benzyl bromide.
However, the Br substituent, with a much weaker electron
withdrawing ability, has only a low promoting effect (82%,
entry 4 of Table 2 versus entry 2 of Table 1). When using 1,4- able with those of other reported copper complexes bearing
1
2c–f
12b,g
diethynylbenzene instead of ethynylbenzene as a substrate, the phosphines,
reaction is not so effective (Table 2, entries 5–9). All isolated methanes
tris(triazolyl)methanols,
tris(pyrazolyl)
However, our
1
2h,i
12i–k
and N-heterocyclic carbenes.
1
,4-disubstituted 1,2,3-triazoles were fully characterized by water soluble AHAMCs have an important advantage over
elemental analysis and NMR spectroscopy (see the ESI†).
these ligands as they are easily prepared from readily available
Most of the protocols for the synthesis of 1,4-disubstituted and cheap starting materials using a very simple and mild syn-
6
d,f
1
,2,3-triazoles use long reaction times,
toxic solvents (e.g. thetic protocol, in addition to their high stability in air and
9
e
THF and toluene), costly reagents (Au, Ag, Ir, and Ln com- water and under several reaction conditions. Moreover, all cat-
plexes), and may occur in a multistep manner.
6
d
6e,9e
Our alysts of this study exhibit good solubility in water and using
method is straightforward, uses inexpensive reagents, is per- water-soluble catalysts simplified their separation from the
formed in aqueous medium and under MW irradiation, hydrophobic product (1,4-disubstituted 1,2,3-triazole). This
achieving conversions that are comparable to other related sys- fact is relevant for the industrial application of homogeneous
1
2a,b
tems.
tively milder as only 10 W of MW irradiation were applied in a economical and environmental costs of the chemical process.
shorter time and in the absence of reducing agents. In terms
The discussion of the effect of the structure on the catalytic
In addition, our experimental conditions are rela- catalysis since an easy way for catalyst separation can lower the
of the obtained high yields and regioselectivities for AAC reac- activity of the compounds, with the aiming of finding a struc-
tions, the efficiency of our complexes as catalysts is compar- ture–catalytic activity relationship, is not straightforward.
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a,b,g
Considering that dissolution in water of the copper(II) nitrate mediate (C);
(iii) involvement of dinuclear species (C and
1
3f,h
salt should lead to the formation of the hexaaqua complex and Ds) despite the mononuclear nature of the precatalyst;
(iv)
that a low catalytic activity is observed, we believe that the cata- acetylide–azide coupling upon oxidative addition followed by
lytic activity is promoted by the hydrazone ligand. The low reductive elimination steps; and (v) the role of the arylhydra-
activity of the complex salt 7 can be related to the enforced zone ligand acting as a stabilizer of the Cu(I) centre and as
stabilization of the hydrazone anion simultaneously through proton acceptor/donor species. The primary participation of
RAHB and CAHB, which hampers its coordination to copper; the azide molecule by coordination to 2 in the aforementioned
despite their detection in the solid state, these interactions induction period of formation of the Cu(I) active catalyst
can also occur in water solution. Since compounds 2, 3 and 5 should not be disregarded, as well as the recognised facile
1
3i
are more catalytically active than 7, coordination of the hydra- binding of azide to Cu(II) relatively to Cu(I) compounds.
zone species to the metal cation has been proved to favour the To find some evidence for the involvement of some of the
catalysis. Moreover, the RAHB and CAHB contacts in the co- aforementioned species in our system, reactions were per-
+
ordinated hydrazone in 3 inhibit its performance, which is formed under ESI-MS , namely by mixing complex
2
lower than that of complex 5 in view of the non-existent CAHB (0.2 mmol) and ethynylbenzene (1 mmol) in a 1 : 1 water :
system in the latter. Compound 2, the most active catalyst, acetonitrile solution, and by mixing the reaction components
lacks both H-contact interactions. However, other types of using the amounts specified in Table 1, entry 12.
+
factors of the catalytic activity can be considered on the basis
of the expected mechanism, as discussed below.
The ESI-MS spectrum of the first mixture is shown in
Fig. S21† and shows evidence for the occurrence of the Glaser
A conceivable mechanism for the CuAAC reaction catalysed reaction indicated in Scheme 4, viz., the product of the alkyne–
+
by 2 is depicted in Scheme 4, taking into consideration a col- alkyne homocoupling reaction {PhCuC–CuCPh + H O + H}
2
I
1 +
lection of key mechanistic aspects based on reported compu- (m/z 221) and the formation of{Cu (H
3
L )} (m/z 347), together
1
3
I
1
+
tational and experimental studies, in particular: (i) alkyne– with the related solvated groups {Cu (H
3
L ) + H
2
O} (m/z 365),
I
1
+
I
1
alkyne homocoupling with the generation of a Cu(I) species {Cu (H L ) + MeCN} (m/z 388) and {Cu (H L ) + H O +
3
+
3
2
9
u
(
A), in an initial short induction period (Glaser reaction),
which is the one responsible for the catalytic reaction progress; A; the peak at m/z 449 can correspond to {Cu (H
ii) π-coordination of the ethynylbenzene to the Cu(I) site (B) (intermediate B). This experiment also shows evidence for the
MeCN} (m/z 406), all these revealing variants of intermediate
I
1
+
3
L )(PhCCH)}
(
+
promoting CH-acidity of the terminal alkyne and the for- formation, under ESI-MS conditions, of a dinuclear species
I
2
1
mation of the σ, π-coordinated acetylide in a di-Cu(I) inter- involving solely the protonated hydrazone ligand {Cu (H
3
L ) +
Scheme 4 Postulated mechanism of the Cu–AAC reaction.
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+
H
2
O + MeCN} (m/z 468) and of another dinuclear species with selectively 1,4-disubstituted 1,2,3-triazoles in yields up to 98%
I
1
+
acetylene {Cu (H L )(PhCuCH) + 3H O + MeCN} (m/z 709).
after being placed for 15 min at 125 °C under low power
2
3
2
2
+
The set of fragmentation peaks in the ESI-MS spectrum of (10 W) MW irradiation.
the second mixture (Fig. S22†) allowed the identification of the
+
ESI-MS analysis of the catalytic reaction mixture using 2 as
triazole product (m/z 236), as well as the hydrated sodium salt a pre-catalyst supported the generation of the catalytically
1
+
of the ligand {H
3 2
L + Na + H O} (m/z 326). Evidence for the active Cu(I) species and the alkyne–alkyne coupling, in what is
I
1
coordination of the organic azide is given by {Cu (H
3
L ) considered as the induction period for this reaction. These
+
(
PhCH N ) + 3H O} (m/z 533). The identified dinuclear experiments also showed the formation of dinuclear species
2
3
2
I
2
1
+
species include {Cu (H
3
L ) + H
2
O} (m/z 426), a variant of involving the hydrazone, the alkyne, or both the alkyne and
I
2
1
+
structure C {Cu (H
3
L )(PhCuCH) + H
2
O + MeCN} (m/z 570) the organic azide (or the dipolar cycloaddition product). The
I
+
and a structure of D type, {Cu (PhCH N PhCCH) + 2H O}
m/z 633).
On the basis of the proposed mechanism which involves an
detection of the free hydrazone suggests ligand decoordination
to some extent and explains the loss of activity of the complex.
This protocol provides the first example of using Cu(II)–aryl-
2
2
3
2
2
(
oxidative addition step to the metal, the highest activity of hydrazone complexes as homogeneous catalysts for the AAC
catalyst 2 is consistent with the expected most favourable reaction, following a facile synthetic procedure with in-
occurrence of such a type of reaction in this case, in view of expensive reagents and being applied to various substrates.
the lower charge (in comparison with 7) and of the direct The generality of this research direction is worth exploring.
coordination of the anionic sulfonate group (2 and 5 in con-
trast to 3, all with the same charge). In accord, the lowest
activity of 7 is due to the cationic character of the copper
centre and the absence of electron donation by the hydrazine
species which is uncoordinated.
4
. Experimental
4.1. Materials and general procedures
All synthetic procedures were performed in air. Reagents and
solvents were obtained from commercial sources and used
−
1
without further purification. Infrared spectra (4000–650 cm
)
3
. Conclusions
were recorded on a Cary 630 FTIR spectrometer; wavenumbers
are reported in cm− ; abbreviations: s, strong; m, medium; w,
weak. Elemental analyses (C, H, and N) were carried out by the
Microanalytical service of the Instituto Superior Técnico.
Electrospray mass spectra (ESI-Ms) were obtained using a
Varian 500-MS LC Ion Trap mass spectrometer equipped with
an electrospray ion source. For electrospray ionization, the
drying gas and the flow rate were optimized according to the
sample with 35 p.s.i. nebulizer pressure. The scanning was
performed from m/z 0 to 2000. All compounds were observed
in both the negative and positive modes (capillary voltage =
1
Novel water-soluble copper(II) complexes (2, 3, 5 and 7) con-
taining ortho-sulfonic functionalized arylhydrazones of
β-diketones were synthesized from the corresponding aryl-
hydrazone sodium salts (1, 4 and 6). The reaction is shown to
strongly depend on the pH of the medium and solvents used
in the synthesis. All the compounds were fully characterized,
also by single-crystal X-ray diffraction analysis, and tested as
catalysts in the 1,3-dipolar cycloaddition of ethynylbenzene
and 1,4-diethynylbenzene with substituted benzyl bromides in
3
the presence of NaN (AAC reaction) in a water/acetonitrile
mixture under microwave irradiation.
1
13
80–105 V). H, C and DEPT NMR spectra were obtained in
DMSO-d using a Bruker Advance 400 MHz spectrometer at
ambient temperature. Chemical shifts δ are quoted in ppm. All
spectra were internally referenced to residual protio-solvent
6
While none of the sodium precursors is a catalyst, the
copper(II) species are affective catalysts for the reaction and
their activity was shown to be highly dependent (i) on the sim-
ultaneous presence of the arylhydrazone moiety and the Cu(II)
cation, (ii) on the concurrent existence of RAHB and CAHB in
the structure of the catalyst, and (iii) on the charge of the
complex and the nature of the coordinating group of the
hydrazone ligand. Hence, in this work we have established, for
the first time, a structure–catalytic activity relationship that
follows the order: Cu(NO3)2 ≪ 7 (complex salt with positive
charge at the copper complex and uncoordinated hydrazone
resonance and are reported relative to SiMe
H and C signals rely on g-COSY and/or g-HSQC experiments.
4
. Assignments of
1
13
The MW irradiation was performed on a focused microwave
Anton Paar Monowave 300 reactor (10 W), using a 10 mL
capacity reaction tube with a 13 mm internal diameter, fitted
with a rotational system and an IR temperature detector.
4.2. Synthesis of arylhydrazone ligands
stabilized by RAHB and CAHB) < 3 (neutral, with hydrazone The sodium salts of arylhydrazone ligands (1, 4 and 6) were
stabilized by RAHB and CAHB, and coordinated via a neutral prepared using the Japp–Klingemann synthetic protocol in two
1
1
binding group) < 5 (neutral, with hydrazone stabilized by steps: (i) Diazotization of aromatic amine. 10 mmol of the
RAHB and coordinated via the anionic sulfonate group) < 2 respective aniline and 0.20 g (5 mmol) of NaOH were dissolved
(neutral, with hydrazone without RAHB and CAHB, and co- in 20 mL of water. The solution was cooled to 0–5 °C; then
ordinated via the anionic sulfonate group, apart from N,O- 0.69 g (10 mmol) of NaNO were added. After 5 minutes of stir-
2
coordination). Complex 2 was thus found to be the most ring, 2 mL HCl were added slowly over 30 minutes in 0.1 mL
efficient catalyst for the 1,3-dipolar cycloaddition, yielding portions, while the temperature was maintained at 0–5 °C
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during the whole time. (ii) Azocoupling. 10 mmol of the 497.50 g mol− ): C 53.11, H 4.86, N 8.45, S 6.45. Found: C
1
−
1
β-diketone compound and 0.40 g (10 mmol) of NaOH were dis- 53.72, H 3.97, N 8.33, S 6.47. FTIR (KBr): ν (cm ) = 3380 m,
solved in 30 mL of a water–ethanol (1 : 2) mixture. This solu- 3198 w, 3100 w, 1648 m, 1594 m, 1559 m, 1484 s, 1441 m,
tion was then added to the suspension of diazonium salt (see 1424 m, 1354 m, 1314 w, 1280 w, 1254 w, 1222 m, 1179 s, 1138
the first step) in portions under vigorous stirring. Catalytic w, 1046 s, 945 m, 885 m, 810 m, 770 w, 735 m, 695 m, 660 m.
−
3 −
amounts of sodium acetate (ca. 0.10 g) were added; then the ESI-MS in MeOH (m/z assignment, % intensity): 410 ([H
2
L ] ,
+
prepared mixture was stirred for an additional 1 h where it 100). ESI-MS in MeOH (m/z assignment, % intensity): 889
3
+
3
+
1
warmed gradually to reach room temperature.
The produced solids were then filtered, washed repeatedly DMSO-d
with ethanol and dried at 40 °C under vacuum. Crystals suit- 8.09–7.15 (m, 11H, Ar–H), 2.56 (s, 3H, CH
able for X-ray measurements were obtained upon recrystalliza- (400 MHz, DMSO-d ) δ: 198.20 (H C–CvO), 160.53 (N–CvO),
([Na (H L ) ] , 89), 456 ([Na (H L )] , 100). H NMR (400 MHz,
3 2 2 2 2
6
) δ: 14.88 (s, 1H, N–NH), 11.03 (s, 1H, C(O)–NH),
1
3
1
3
). C{ H} NMR
6
3
tion from methanol.
Compounds 1, 4 and 6 are soluble in water, methanol and 1 30.73 (NNHCCHCH–Cquat), 130.64 (CvN), 130.38 (SC–Cquat
DMSO and are insoluble in NCMe and chlorinated solvents. Cquat), 129.06 (HC–Ph), 128.76 (HC–Ph), 128.03 (HC–Ph),
92% 127.51 (S–Cquat), 126.62 (HC–Ph), 124.83 (HC–Ph), 124.26 (HC–
S (Mr = Ph), 120.19 (HC–Ph), 115.19 (HC–Ph), 26.11 (CH ). DEPT
07.26 g mol− ): C 39.09, H 3.28, N 13.68, S 10.44. Found: C (400 MHz, DMSO-d ) δ: 131.12, 128.80, 128.51, 127.78, 126.37,
137.89 (N–NH–Cquat), 136.47 (C(O)–NH–Cquat), 131.37 (HC–Ph),
–
1
2
3
4
1
[
Na(μ
4
-1:2κO ,2κO ,3κO ,4κO -H
3
L )]
n
(1): yield
NaO
=
(
2.83 g). Elemental analysis calcd (%) for C10
H
10
N
3
5
3
1
3
3
3
1
6
−
1
9.72, H 3.38, N 12.17, S 10.23. FTIR (KBr): ν (cm ) = 3371 s, 124.58, 124.01, 119.93, 114.94, 25.86.
305 m, 3253 m, 3196 w, 3138 m, 1657 s, 1643 s, 1576 m,
559 m, 1513 s, 1441 m, 1418 m, 1355 m, 1308 w, 1230 s, 1190
4
.3. Synthesis of complexes
s, 1133 s, 1084 s, 1052 m, 1038 m, 1017 s, 940 m, 862 w,
7
−
93 m, 758 m, 709 m. ESI-MS in MeCN (m/z assignment, %
Synthesis of 2 and 3. Compound 1 (0.31 g, 1 mmol) was dis-
1
−
1 −
+
intensity): 591 ([Na(H L ) ] , 9%), 284 ([H L ] , 100). ESI-MS
solved in 20 mL of a water–acetone (1 : 5) mixture (1.5 mL of
L ) 0.1 M NH OH solution was also added to increase the pH up
L )] , 78). H NMR (400 MHz, to 9, in the case of 2); then Cu(NO ·3H O (0.24 g, 1 mmol)
DMSO-d ), δ: 14.58 (s, 1H, N–NH), 8.32 (s, 1H, C(O)–N–H⋯O), was added to the reaction mixture. The obtained dark green or
3
2
3
1
in MeCN (m/z assignment, % intensity): 371 ([Na
2
(H
3
4
+
1
+
1
(MeCN)] , 100), 330 ([Na
2
(H
3
3
)
2
2
6
7
9
1
d
C
1
.75–7.67 (m, 2H, Ar–H and 1H, C(O)–N–H), 7.42 (dd, J
.6 Hz, J = 1.2 Hz, 1 H, Ar–H), 7.11 (dd, J = 10 Hz, J = 1.2 Hz, left in the open air at room temperature for slow evaporation
H, Ar–H), 2.45 (s, 3H, CH3). C{ H} NMR (400 MHz, DMSO- to afford or as green crystals suitable for X-ray
) δ: 198.07 (H C–CvO), 164.14 (H N–CvO), 138.71 (HN– measurements.
quat–Ph), 135.21 (CvN), 130.25 (HC–Ph), 128.03 (S–Cquat–Ph), Compounds 2 and 3 have a good solubility in water, DMF
27.44 (HC–Ph), 123.40 (HC–Ph), 115.40 (HC–Ph), 26.07 (CH3). and DMSO, and are insoluble in MeOH, NCMe and in chlori-
DEPT (400 MHz, DMSO-d ) δ: 130.00, 127.19, 123.15, 115.15, nated solvents.
5.82.
1
=
green (in the case of 3) solution was stirred for 1 h and then
2
1
2
1
3
1
2
3
6
3
2
6
1
2
1
2
2 2 2 2
[Cu(κO O N-H L )(H O) ]·2H O (2): yield = 91% (0.38 g,
1
2
2
[
Na(μ-1κO ,2κO -H L )] (4): yield = 86% (3.25 g). Elemental based on Cu). Elemental analysis calcd (%) for C H CuN O S
4
2
10 17
3 9
S (Mr = 377.30 g mol− ): C (Mr = 418.87 g mol ): C 28.67, H 4.09, N 10.03, S 7.66. Found:
1
−1
analysis calcd (%) for C10
H
16
N
3
NaO
9
−1
3
1.83, H 4.27, N 11.14, S 8.50. Found: C 31.59, H 4.12, N 10.60, C 29.24, H 3.84, N 10.51, S 7.64. FTIR (KBr): ν (cm ) = 3310 Br
−
1
S 7.94. FTIR (KBr): ν (cm ) = 3417 s, 3287 m, 3080 w, 1667 m, s, 3183 s, 1603 s, 1390 m, 1352 s, 1320 m, 1300 w, 1277 w,
1
1
635 m, 1606 m, 1531 m, 1444 w, 1421 w, 1395 w, 1355 m, 1223 s, 1188 m, 1136 s, 1084 m, 1055 w, 1012 s, 948 m, 908 w,
312 m, 1292 m, 1254 m, 1234 m, 1182 s, 1127 m, 1087 s, 1032 868 w, 807 m, 758 s, 741 w, 721 m, 669 w. ESI-MS in H O (m/z
2
−
−
1
1 −
s, 948 m, 827 w, 807 m, 784 w, 698 s. ESI-MS in MeOH (m/z assignment, % intensity): 630 ([Cu(H L )(H L )] , 100), 284
assignment,
2
3
2
−
1 −
+
%
intensity): 623 ([Na(H
4
L )
2 3 2
] , 15%), 300 ([H L ] , 61). ESI-MS in H O (m/z assignment, % intensity):
2
−
+
1
+
1
+
([H
4
L ] , 100). ESI-MS in MeOH (m/z assignment, % inten- 712 ([H{Cu(H L )} (H O)] , 82), 694 ([H{Cu(H L )} ] , 49), 364
2 2 2 2 2
2
+
2
+
1
+
1
+
sity): 1315 ([Na (H L ) ] , 53), 992 ([Na (H L ) ] , 100), 669 ([H{Cu(H L )}(H O)] , 100), 347 ([H{Cu(H L )}] , 13), 286
5
4
4
4
4
3
2
2
2
2
+
2
+
1
1 +
([Na
3
(H
4
L )
2
] , 54), 346 ([Na
2
(H
4
L )] , 60). H NMR (400 MHz, ([H(H
) δ: 14.68 (s, 1H, N–NH), 8.57 (s, 1H, C(O)–N–H⋯O),
4
L )] , 8).
1
DMSO-d
6
[Cu(κO-H
3
L )
2
(H
2
O)
4
] (3): yield = 83% (0.29 g, based on Cu).
7
1
2
.91 (s, 1H, C(O)–N–H), 7.81 (s, 1H, HN–C–CH), 7.26 (d, J = Elemental analysis calcd (%) for C H CuN O S (Mr =
20 28 6 14 2
2 Hz, 1H, SC–CH–CH), 6.86 (d, J = 12 Hz, 1 H, HO–C–CH), 704.14 g mol− ): C 34.11, H 4.01, N 11.94, S 9.11. Found: C
1
1
3
1
−1
3 6
.44 (s, 3H, CH ). C{ H} NMR (400 MHz, DMSO-d ) δ: 197.63 33.89, H 3.79, N 11.80, S 9.32. FTIR (KBr): ν (cm ) = 3457 m,
(H C–CvO), 165.93 (H N–CvO), 146.75 (HO–Cquat–Ph), 140.20 3313 m, 3108 s, 1638 s, 1571 m, 1551 w, 1517 s, 1450 m,
3 2
(
(
(
2
CvN), 128.70 (HN–Cquat–Ph), 126.81 (S–Cquat–Ph), 122.85 1416 m, 1355 m, 1315 w, 1243 s, 1165 s, 1133 s, 1084 m, 1052
−
SC–CH–CH), 114.67 (HO–C–CH), 111.97 (N–Cquat–CH), 25.77 w, 1018 s, 946 m, 862 w, 793 m, 755 s, 712 s. ESI-MS in H
2
O
1
−
CH ). DEPT (400 MHz, DMSO-d ) δ: 122.60, 114.42, 111.71, (m/z assignment, % intensity): 915 ([Cu(H L ) ] , 12%), 630
3
6
3
3
1
1
−
1 −
+
5.52.
([Cu(H O (m/
3
L )(H
2
L )] , 83), 284 ([H
3
L ] , 100). ESI-MS in H
2
1
2
3
3
1
+
[
Na(μ-1κO κO ,2κO -H
2
L )(CH
3
OH)
2
]
2
(6): yield
=
94% z assignment, % intensity): 1611 ([Cu (H L ) ] , 67), 980
3 3 5
1
+
1
+
1 +
(
4.67 g). Elemental analysis calcd (%) for C H N NaO S (Mr = ([Cu (H L ) ] , 79), 347 ([Cu(H L )] , 100), 286 ([H(H L )] , 12).
22 24 3 7 2 3 3 3 4
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Synthesis of 5. Compound 4 (0.38 g, 1 mmol) was dissolved DFIX command. Coordinates of hydrogen atoms bonded to
in a MeOH/MeCN (1 : 2) (20 mL) mixture, and Cu(NO ) ·3H O carbon atoms were included in the refinement using the
3
2
2
(0.12 g, 0.5 mmol) was added. The produced solution was riding-model approximation with the Uiso(H) defined as 1.2Ueq
stirred under reflux for 3 h. The obtained green product was of the parent aromatic atoms, and 1.5Ueq of the parent carbon
filtered off, washed repeatedly with ethanol and dried under atoms for methyl. Least-squares refinements with anisotropic
vacuum. Crystals of 5 suitable for X-ray measurements were thermal motion parameters for all the non-hydrogen atoms
obtained by allowing the filtrate to stand at room temperature were employed. In 4 the oxygen atoms of the sulfonate group
for slow evaporation.
were disordered over two positions with occupancies of 0.53
Compound 5 is soluble in water, methanol, DMF and and 0.47% and were refined with the use of PART instruction.
DMSO and is insoluble in NCMe and chlorinated solvents.
Despite the low-quality data for 7 resulting from low diffracting
2
[
Cu(κO-H L ) (H O) ] (5): yield = 71% (0.26 g, based on Cu). crystals, the final refinement parameters are reasonably good;
4
2
2
4
Elemental analysis calcd (%) for C20
H
28CuN
6
O
16
S
2
(Mr = the structure proves the composition of the sample and is
36.14 g mol− ): C 32.63, H 3.83, N 11.42, S 8.71; found: C included in this study for comparative purposes.
1
7
3
1
−
1
3.23, H 3.80, N 11.28, S 8.87. FTIR (KBr): ν (cm ) = 3193 s, Crystallographic data are given in Table S1 (ESI†); selected
599 s, 1519 m, 1470 m, 1406 s, 1352 m, 1280 s, 1233 m, 1156 bond lengths and angles are given in Table S2† and hydrogen-
s, 1087 m, 1032 s, 977 m, 931 m, 876 m, 844 w, 819 w, 770 w, bond interactions in Table S3.† The structures with partial
−
6
95 m. ESI-MS in H O (m/z assignment, % intensity): 300 numbering schemes are shown in Fig. 1.
2
2
−
+
([H
4
L ] , 100). ESI-MS in H
2
O (m/z assignment, % intensity):
Crystallographic data for the structural analysis have been
deposited to the Cambridge Crystallographic Data Center
2
+
2 +
1
2 4 3 4
028 ([Cu (H L ) ] , 62), 363 ([Cu(H L )] , 100).
Synthesis of 7. Cu(NO ) ·3H O (0.06 g, 0.25 mmol) was [CCDC 1857654 (for 1), 1857660 (for 2), 1857658 (for 3),
3
2
2
added to a solution of 6 (0.25 g, 0.5 mmol) in 20 mL of water. 1857655 (for 4), 1857656 (for 5), 1857657 (for 6) and 1857659
The obtained solution was stirred under reflux for 5 min. The (for 7)†].
obtained green product was filtered off, dried under vacuum,
and recrystallized from a mixture of DMF/MeOH (1 : 20) solu-
tions to afford 7 as crystals suitable for X-ray measurements.
4
.5. General procedure for the three-component azide alkyne
cycloaddition reaction
Compound 7 is soluble in water and DMSO and is insoluble A mixture of the respective substituted benzyl bromide
in MeOH, DMF, NCMe and chlorinated solvents. (0.30 mmol, 1 equiv.), ethynylbenzene (0.33 mmol, 1.1 equiv.),
NCHO (7): yield = 81% (0.23 g, NaN (0.33 mmol, 1.1 equiv.), the catalyst (1–5 mol%) and
based on Cu). Elemental analysis calcd (%) for 1.5 mL of solvent was charged to a 10 mL pyrex vial equipped
3
[
Cu(H
2
O)
6
]·2H
2
L ·2(CH
3
)
2
3
−
1
C
46
H
58CuN
8 18 2
O S (Mr = 1138.67 g mol ): C 48.52, H 5.13, N with a magnetic stirring bar. The vial was then tightly sealed
9
.84, S 5.63. Found: C 48.11, H 4.88, N 8.62, S 6.30. FTIR (KBr): and placed in the microwave reactor to be irradiated (10 W) at
−1
ν (cm ) = 3241 m, 1652 m, 1638 m, 1615 w, 1594 m, 1560 m, 125 °C for the periods of time indicated in Table 1 and
1
1
8
485 s, 1442 m, 1427 m, 1413 m, 1361 m, 1295 m, 1254 m, Scheme 3. A precipitate was formed; the reaction mixture was
179 s, 1156 s, 1139 s, 1061 m, 1044 s, 986 w, 957 m, 885 w, cooled to ambient temperature and diluted with 7 mL of
50 w, 807 m, 770 w, 744 m, 703 m, 663 m. ESI-MS in MeOH water. The product was filtered off, washed repeatedly with pet-
−
3
−
+
(
m/z assignment, % intensity): 410 ([H
2
L ] , 100). ESI-MS in roleum ether and dried under vacuum. In the case of 1,4-
3
+
MeOH (m/z assignment, % intensity): 473 ([Cu(H
2
L )] , 100).
diethynylbenzene as a substrate (Table 2), the reactions were
performed according to the general procedure described above
except that 0.60 mmol of the respective benzyl bromide deriva-
4
.4. X-ray structure determination
X-ray quality single crystals of the compounds were mounted tive, 0.33 mmol of 1,4-diethynylbenzene and 0.62 mmol of
1
13
in a nylon loop and measured at ambient temperature. sodium azide were used. The H, C and DEPT NMR spectro-
Intensity data were collected using a Bruker AXS-KAPPA APEX scopic data of all 1,4-disubstituted 1,2,3-triazole products are
II PHOTON 100 diffractometer with graphite monochromated reported in the ESI.†
+
Mo-Kα (0.71069 Å) radiation. Data were collected using omega
ESI-Ms analysis of the catalytic reaction mixtures. Mixture
scans of 0.5° per frame and full sphere of data were obtained. 1: (Complex 2 + ethynylbenzene).
Cell parameters were retrieved using Bruker SMART software 1 mmol of ethynylbenzene and 0.2 mmol of complex 2
1
4
and refined using Bruker SAINT on all the observed reflec- (20 mol%) were mixed in a 2 mL mixture of water and aceto-
tions. Absorption corrections were applied using the SADABS nitrile (1 : 1). The obtained mixture was left at room tempera-
1
5
+
program. The structures were solved by direct methods using ture for 1 h, and then subjected to the ESI-Ms analysis.
1
6
+
1
the SIR97 software package and refined with SHELXL-2014/
Calculations were performed using the WinGX System {PhCuCH}] , 12), 406 {Cu (H
Version 2014-1. The hydrogen atoms of water, hydrazine or ({Cu (H
amine groups were found in the difference Fourier map and ([Cu {H L }] , 7), 221 ([{PhCuC–CuCPh + H O + H}] , 4), 144
the isotropic thermal parameters were set at 1.5 times the ([{PhCuCH + MeCN} + H] , 100).
average thermal parameters of the belonging oxygen or nitro- Mixture 2: (Complex 2 + ethynylbenzene + NaN
ESI-MS (m/z assignment, % intensity): 449 ([Cu{H L }
3
1
7
+
I
1
+
7
.
3
L )
+
MeCN} , (7), 388
L ) + H
1
8
I
1
+
I
1
+
3
L ) + MeCN} , 14), 365 ({Cu (H
3
2
O} , 12), 347
I
1
+
+
3
2
+
3
+ Benzyl
gen atoms, frequently with their distances restrained using the bromide).
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Benzyl bromide (0.30 mmol, 1 equiv.), ethynylbenzene
0.33 mmol, 1.1 equiv.), NaN (0.33 mmol, 1.1 equiv.) and the
complex 2 (0.015 mmol, 5 mol%) were added to a 1.5 mL solu-
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(
3
tion of water and acetonitrile (1 : 1). The obtained mixture was
+
left at room temperature for 1 h and then subjected to ESI-MS
analysis.
+
intensity): 633 {CuI
2
ESI-MS
(m/z assignment,
%
+
I
1
(
PhCH N PhCCH) + 2H O} , (6), 570 ({Cu (H L )(PhCCH) +
2
3
2
2
2
3
+
I
1
+
H
2
O + MeCN} , 3) 533 ({Cu (H
3
L )(PhCH
2
N
3
) + 3H
2
O} , 24),
1
+
I
2
1
+
4
71 ([Cu{NaH
2
L }{PhCuCH}] , 12), 426 ({Cu (H
3
L ) + H
+ H] , 4).
2
O} ,
1
+
+
2
7), 326 ([{NaH L + H O + H}] , 100), 236 ([M
3
2
triazol
Conflicts of interest
There are no conflicts to declare.
(
i) D. K. Nasirova, A. V. Malkova, K. B. Polyanskii,
K. Y. Yankina, P. N.-A. Amoyaw, I. A. Kolesnik,
A. V. Kletskov, I. A. Godovikov, E. V. Nikitina and
F. I. Zubkov, Tetrahedron Lett., 2017, 58, 4384–4387;
Acknowledgements
(
j) F. Reck, F. Zhou, M. Girardot, G. Kern, C. J. Eyermann,
This work has been partially supported by the Foundation for
Science and Technology (FCT) (UID/QUI/00100/2013),
Portugal. AGM is grateful to the CATSUS doctoral program of
FCT for his PhD fellowship (SFRH/BD/106006/2014). KTM
acknowledges the FCT and Instituto Superior Técnico (DL 57/
N. J. Hales, R. R. Ramsay and M. B. Gravestock, J. Med.
Chem., 2005, 48, 499–506; (k) D. Y. Vandyshev,
K. S. Shikhaliev, A. Y. Potapov, M. Y. Krysin, F. I. Zubkov
and L. V. Sapronova, Beilstein J. Org. Chem., 2017, 13, 2561–
2
568; (l) H. Elamari, R. Slimi, G. G. Chabot, L. Quentin,
D. Scherman and C. Girard, Eur. J. Med. Chem., 2013, 60,
60–364; (m) W.-T. Li, W.-H. Wu, C.-H. Tang, R. Tai and
S.-T. Chen, ACS Comb. Sci., 2011, 13, 72–78;
n) K. K. Borisova, E. V. Nikitina, R. A. Novikov,
2
016 and L 57/2017 Program, Contract No. IST-ID/85/2018).
The authors acknowledge the Portuguese NMR Network
IST-UL Centre) for access to the NMR facility and the IST
3
(
Node of the Portuguese Network of Mass-spectrometry for the
ESI-MS measurements.
(
V. N. Khrustalev, P. V. Dorovatovskii, Y. V. Zubavichus,
M. L. Kuznetsov, V. P. Zaytsev, A. V. Varlamov and
F. I. Zubkov, Chem. Commun., 2018, 54, 2850–2853;
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