Copper(II) oxide nanowhiskers—A new efficient catalyst of azide–alkyne cycloaddition

Full text of DOI:10.1134/S1070428016100328

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2016, Vol. 52, No. 10, pp. 1537–1539. © Pleiades Publishing, Ltd., 2016.
Original Russian Text © A.S. Bunev, E.S. Belinskaya, N.N. Gryzunova, A.A. Vikarchuk, 2016, published in Zhurnal Organicheskoi Khimii, 2016, Vol. 52,
No. 10, pp. 1542–1544.
SHORT
COMMUNICATIONS
Copper(II) Oxide Nanowhiskers—A New Efficient Catalyst
of Azide–Alkyne Cycloaddition
A. S. Bunev,* E. S. Belinskaya, N. N. Gryzunova, and A. A. Vikarchuk
Togliatti State University, ul. Belorusskaya 14, Togliatti, 445667 Russia
*
e-mail: a.s.bunev@gmail.com
Received February 1, 2016
DOI: 10.1134/S1070428016100328
At the beginning of the XXI century, much atten-
tion has been given to environmentally benign pro-
cesses with the use of highly efficient catalysts [1–3].
Among numerous transition metal compounds, copper
catalysts have been most needed during the past
decade [4–7]. The discovery of azide–alkyne cycload-
dition catalyzed by copper salts, which selectively
affords 1,4-disubstituted 1,2,3-1H-triazoles, has opened
new perspectives in the 1,2,3-triazole chemistry [8, 9].
It is known that 1,2,3-1H-triazole derivatives are
important building blocks for the synthesis of nitrogen-
containing heterocycles and are widely used in
pharmaceutical industry and agricultural chemistry
average diameter of copper oxide nanowhiskers ranged
from 40 to 120 nm, and their length was up to 100 nm.
The X-ray powder diffraction data showed that copper
nanowhiskers consist of three phases: coperr(II) oxide,
copper(I) oxide, and copper metal [23].
The optimal conditions for the reaction of phenyl-
acetylene (1a) with benzyl azide (2a) as model sub-
strates were as follows: a mixture of 1a and 2a in
aqueous tert-butyl alcohol was heated for 12 h at 50°C
in the presence of 2 mol % of copper oxide nano-
whiskers (calculated on Cu) and 20 mol % of sodium
ascorbate as reducing agent necessary for the regenera-
tion of the whisker surface consisting mainly of CuO.
The yield of 1-benzyl-4-phenyl-1,2,3-1H-triazole (3a)
[10, 11]. The following compounds should be noted
among efficient copper catalysts of the azide–alkyne
cycloaddition: CuSO [12–14], Cu O [15], CuI
1
attained 88% according to the H NMR data.
4
2
The reactions of substituted acetylenes 1a–1c with
azides 2a–2f under the optimal conditions afforded
[
[
16, 17], (Ph P) CuBr [18], copper nanoparticles
3 2
19], CuFe O [1], Cu/SiO [20], Cu/S [21], and
2
4
2
1
,4-disubstituted 1,2,3-1H-trizoles 3a–3j in 87–93%
Cu/Cu O [22].
2
yield. No relation between the substituent nature in the
initial reactants and the product yield was observed.
Herein we present the results of studying the cata-
lytic activity of nanosized whiskers (filamentary crys-
tals) in the azide–alkyne cycloaddition. We previously
reported a new form of copper(II) oxide, nanosized
whiskers [23]. According to the low-temperature kryp-
ton desorption data, the obtained catalyst was charac-
1
The H NMR spectra of 3a–3j displayed a singlet at
δ 7.50–7.91 ppm due to 5-H on the triazole ring, as
well as signals from aromatic protons and substituents
1
3
in the aromatic rings. The C NMR spectra of 3a–3j
2
terized by a high specific surface area (81 m /g). The
contained signals at δ
C
119.0–121.0 and 131.0–
Copper nanowhiskers
NaOAsc, t-BuOH–H O (1:1)
R1
2
5
0°C, 12 h
HC
R1
+
R2
N3
R2
N
N
N
1
a–1c
2a–2f
3a–3j
1
2
1
3
, R = Ph (a), 4-MeC
6
H
4
(b), PhOCH
2
(c); 2, R = Ph (a), 4-MeC
(c), 4-FC
6
H
4
(b), 4-MeOC
(d), 4-O NC (e); R = 4-MeC
Et (i); R = PhOCH
6
H
4
(c), 4-FC
6
H
4
(d), 4-O
2
NC
, R = Ph (f), 4-MeC
2
, R = Ph (j).
6
H
4
(e), CO
2
Et (f);
1
2
1
2
, R = Ph, R = Ph (a), 4-MeC (b), 4-MeOC
6
H
4
6
H
4
6
H
4
2
6
H
4
6
H
4
H (g);
6 4
1
2
1
2
1
2
R = Ph, R = CO
2
Et (h); R = 4-MeC
6
H
4
, R = CO
2
1
537

1
1
538
BUNEV et al.
4
5
35 ppm (C , C ), which indicated formation of exclu-
ppm: 53.1, 119.7, 124.0, 124.2, 125.7, 128.4, 128.5,
128.8, 130.0, 141.7, 148.0, 148.6.
sively 1,4-disubstituted 1,2,3-1H-triazoles.
General procedure for azide–alkyne cycloaddi-
tion. Copper oxide nanowhiskers (0.04 mmol of Cu),
and a solution of 0.4 mmol of sodium ascorbate in
1-Benzyl-4-(4-methylphenyl)-1H-1,2,3-triazole
(3f). Yield 92%, mp 153–155°C. H NMR spectrum, δ,
1
ppm: 2.35 s (3H, CH
arom, J = 8.0 Hz), 7.26–7.30 m (2H, Harom), 7.35–
7.40 m (3H, Harom), 7.61 s (1H, 5-H), 7.68 d (2H,
), 5.55 s (2H, CH ), 7.20 d (2H,
3
2
0
.1 mL of water were added in succession to a mixture
of 2 mmol of acetylene 1a–1c and 2 mmol of azide
a–2f in 5 mL of aqueous tert-butyl alcohol (1:1). The
H
1
3
2
Harom, J = 8.1 Hz). C NMR spectrum, δ , ppm:
C
mixture was stirred for 12 h at 50°C, and the precip-
itate was filtered off and dried in air.
21.2, 54.1, 119.1, 125.5, 127.7, 128.0, 128.7, 129.0,
129.4, 134.7, 127.9, 148.2. Found, %: C 77.11;
H 6.10; N 16.91. C H N . Calculated, %: C 77.08;
16
15
3
1
-Benzyl-4-phenyl-1H-1,2,3-triazole (3a). Yield
H 6.06; N 16.85.
8
1
7
7
8%, mp 128–129°C; published data [24]: mp 127–
1
28°C. H NMR spectrum, δ, ppm: 5.57 s (2H, CH ),
1-(4-Methylbenzyl)-4-(4-methylphenyl)-1H-
1,2,3-triazole (3g). Yield 91%, mp 118–119°C;
2
.25–7.36 m (3H, Harom), 7.37–7.41 m (5H, Harom),
1
.65 s (1H, 5-H), 7.80 d (2H, Harom, J = 8.6 Hz).
published data [25]: mp 120–121°C. H NMR spec-
1
3
C NMR spectrum, δ , ppm: 54.2, 119.4, 125.6,
trum, δ, ppm: 2.35 s (6H, CH
), 5.50 s (2H, CH ),
3 2
C
1
28.0, 128.1, 128.7, 129.1, 130.5, 134.6, 148.2.
7.17–7.25 m (6H, Harom), 7.58 s (1H, 5-H), 7.67 d (2H,
13
Harom, J = 8.0 Hz). C NMR spectrum, δ , ppm: 21.1,
C
1
-(4-Methylbenzyl)-4-phenyl-1H-1,2,3-triazole
2
1.2, 53.9, 118.9, 125.5, 127.7, 128.0, 129.4, 129.7,
(
3b). Yield 91%, mp 109–111°C; published data [24]:
1
131.6, 137.9, 138.6, 148.1. Found, %: C 77.59;
H 6.55; N 15.99. C H N . Calculated, %: C 77.54;
mp 110–112°C. H NMR spectrum, δ, ppm: 2.35 s
1
7
17
3
(
3H, CH ), 5.52 s (2H, CH ), 7.17–7.21 m (4H, Harom),
3 2
H 6.51; N 15.96.
7
8
8
.28–7.31 m (1H, Harom), 7.38 d.d (2H, Harom, J =
.1, 1.8 Hz), 7.62 s (1H, 5-H), 7.79 d (2H, Harom, J =
Ethyl 2-(4-phenyl-1H-1,2,3-triazol-1-yl)acetate
(3h). Yield 87%, mp 94–95°C; published data [26]:
1
3
.1 Hz). C NMR spectrum, δ , ppm: 21.1, 54.0,
C
1
1
1
19.3, 125.6, 128.0, 128.1, 128.7, 129.7, 130.5, 131.6,
38.7, 148.1.
-(4-Methoxybenzyl)-4-phenyl-1H-1,2,3-triazole
3c). Yield 93%, mp 125–127°C; published data [24]:
mp 92–93°C. H NMR spectrum, δ, ppm: 1.31 t (3H,
CH
, J = 7.5 Hz), 4.29 q (2H, CH , J = 7.4 Hz), 5.20 s
3
2
(
2H, CH ), 7.32–7.36 m (1H, Harom), 7.43 t (2H, Harom
,
2
1
J = 7.5 Hz), 7.85 d (2H, Harom, J = 8.0 Hz), 7.91 s (1H,
(
1
3
1
5
1
-H). C NMR spectrum, δ , ppm: 14.0, 50.9, 62.4,
mp 129–130°C. H NMR spectrum, δ, ppm: 3.81 s
C
20.9, 125.8, 128.2, 128.8, 130.3, 148.2, 166.2.
(
3H, OCH ), 5.50 s (2H, CH ), 6.92 d (2H, Harom, J =
3 2
9
7
6
.2 Hz), 7.25–7.32 m (3H, Harom), 7.90 t (2H, Harom, J =
.5 Hz), 7.61 s (1H, 5-H), 6.79 d (2H, Harom, J =
Ethyl 2-[(4-methylphenyl)-1H-1,2,3-triazol-1-yl]-
acetate (3i). Yield 89%, mp 100–102°C; published
1
3
1
.9 Hz). C NMR spectrum, δ , ppm: 53.7, 55.3,
data [26]: mp 99–101°C. H NMR spectrum, δ, ppm:
C
1
1
14.5, 119.2, 125.6, 126.6, 128.0, 128.1, 128.7, 129.6,
29.8, 130.5, 148.1, 159.9.
-(4-Fluorobenzyl)-1-phenyl-1H-1,2,3-triazole
3d). Yield 89%, mp 154–155°C; published data [25]:
1.30 t (3H, CH , J = 7.4 Hz), 2.38 s (6H, CH ), 4.28 q
3
3
(2H, CH , J = 6.9 Hz), 5.18 s (2H, CH ), 7.24 d (2H,
2
2
Harom, J = 8.1 Hz), 7.74 d (2H, Harom, J = 8.0 Hz),
4
1
3
7
2
1
.86 s (1H, 5-H). C NMR spectrum, δ , ppm: 14.0,
(
C
1
1.2, 50.9, 62.4, 120.5, 125.7, 127.5, 129.4, 138.1,
48.3, 166.2. Found, %: C 63.73; H 6.21; N 17.20.
mp 152–153°C. H NMR spectrum, δ, ppm: 5.54 s
(
(
(
2H, CH ), 7.07 t (2H, Harom, J = 8.6 Hz), 7.29–7.33 m
3H, Harom), 7.40 t (2H, Harom, J = 7.5 Hz), 7.65 s
1H, 5-H), 7.80 d (2H, Harom, J = 8.1 Hz). C NMR
2
C H N O . Calculated, %: C 63.66; H 6.16; N 17.13.
13 15
3
2
1
3
1-Benzyl-4-(phenoxymethyl)-1H-1,2,3-triazole
(3j). Yield 93%, mp 126–127°C; published data [24]:
spectrum, δ , ppm: 53.4, 116.1, 119.2, 119.3, 125.7,
1
1
C
1
28.3, 128.7, 128.8, 129.7, 129.8, 130.0, 130.4, 130.5,
48.3, 161.8.
mp 128–129°C. H NMR spectrum, δ, ppm: 5.15 s
(2H, CH ), 5.49 s (2H, CH ), 6.89–6.93 m (3H, Harom),
2
2
7
7
6
1
.21–7.26 m (4H, Harom), 7.29–7.34 m (3H, Harom),
1
-(4-Nitrobenzyl)-4-phenyl-1H-1,2,3-triazole
1
3
.50 s (1H, 5-H). C NMR spectrum, δ , ppm: 54.5,
(
3e). Yield 92%, mp 85–86°C; published data [25]:
mp 91°C. H NMR spectrum, δ, ppm: 5.69 s (2H,
C
1
2.2, 115.0, 121.5, 122.8, 128.3, 129.0, 129.4, 129.8,
34.7, 144.9, 158.4.
CH ), 7.31–7.36 m (1H, Harom), 7.40–7.44 m (4H,
2
1
13
Harom), 7.76 s (1H, 5-H), 7.81 d (2H, Harom, J = 6.9 Hz),
.22 d (2H, Harom, J = 6.9 Hz). C NMR spectrum, δ ,
The H and C NMR spectra were recorded on
a Bruker Avance spectrometer at 600 and 150 MHz,
1
3
8
C
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 52 No. 10 2016

COPPER(II) OXIDE NANOWHISKERS—A NEW EFFICIENT CATALYST
1539
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RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 52 No. 10 2016