Reusable polymer-supported terpyridine copper complex for [3+2] Huisgen cycloaddition in water

Article abstract of DOI:10.3987/COM-09-11872

A polymer-supported terpyridine copper(I) complex was prepared and found to promote the Huisgen [3+2] cycloaddition reaction between azides and alkynes in water to give the corresponding triazoles with up to 87% isolated yield. This catalyst was recovered

Full text of DOI:10.3987/COM-09-11872

HETEROCYCLES, Vol. 81, No. 3, 2010
601
HETEROCYCLES, Vol. 81, No. 3, 2010, pp. 601 - 610. © The Japan Institute of Heterocyclic Chemistry
Received, 13th November, 2009, Accepted, 25th December, 2009, Published online, 29th December, 2009
DOI: 10.3987/COM-09-11872
REUSABLE
POLYMER-SUPPORTED
TERPYRIDINE
COPPER
COMPLEX FOR [3+2] HUISGEN CYCLOADDITION IN WATER
Toshimasa Suzuka, 1,* Kazumasa Ooshiro, 1 and Ken’yu Kina2
2
1Department of Chemistry and Cooperative Research Center, University of the
Ryukyus, Okinawa 903-0213, JAPAN
E-mail: suzuka@sci.u-ryukyu.ac.jp
Abstract – A polymer-supported terpyridine copper(I) complex was prepared and
found to promote the Huisgen [3+2] cycloaddition reaction between azides and
alkynes in water to give the corresponding triazoles with up to 87% isolated yield.
This catalyst was recovered and reused several times without any loss in catalytic
activity.
INTRODUCTION
Huisgen 1,3-dipolar cycloaddition of organic azides and alkynes1 is recognized as the most successful
method for synthesizing 1,2,3-triazole derivatives, which are important compounds used in agrochemicals
and biochemicals.2 Sharpless et al. successfully reported copper-catalyzed Huisgen 1,3-dipolar
cycloaddition in 2001; their new concept was named “click chemistry.”3 Since then, considerable
research has been conducted on improving the efficiency of the homogeneous conditions and the
applications of this reaction.4 One of the major problems with Sharpless et al.’s reaction lies in the
reaction conditions where a copper reagent is required to promote the reaction at low temperatures to
afford the corresponding 1,4-disubstituted-1,2,3-triazole derivatives with 100% regioselectivity, resulting
in the contamination of the coupling products with metal residue. Recently, several studies have been
conducted to addressing this problem. For example, the [3+2] cycloaddition reaction has been carried
out with solid-supported copper(I) catalysts in organic solvent.5 In addition, Girard et al. examined the
Huisgen [3+2] cycloaddition reaction of acetylenes with azides using Amberlyst A-21 supported Cu(I)
catalyst in CH2Cl2 to give the corresponding 1,4-disubstitued 1,2,3-triazoles in high yield.6 If azides and
acetylenes were reacted in water with recyclable copper catalysts, this would prevent the production of

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organic solvent wastes as well as metal-contaminated wastes, and the Huisgen [3+2] cycloaddition
reaction would meet the green chemical requirements. To meet these requirements, we have developed
an amphiphilic polystyrene-poly(ethylene glycol) (PS-PEG)7 resin-supported copper catalyst, which was
used for the Huisgen [3+2] cycloaddition reaction in water. In this paper, we report our results
demonstrating the Huisgen [3+2] cycloaddition reaction of azides and acetylenes in water in the presence
of a copper complex of an amphiphilic PS-PEG resin-bound terpyridine ligand8 (Scheme 1).
RESULTS AND DISCUSSION
The amphiphilic PS-PEG resin-bound terpyridine ligand was prepared from p-hydroxybenzaldehyde (5),
propane sultone, 2-acetylpyridine (7), and PS-PEG-N2 resin, and the coordination of the synthesized
polymeric terpyridine ligand with copper species proceeded to give the PS-PEG resin-supported
terpyridine copper complex 1, which exhibited good catalytic activity for the Huisgen [3+2] cycloaddition
reaction. Thus, the reaction of p-hydroxybenzaldehyde (5) with propane sultone in IPA at 100 °C for
3 h under alkaline conditions followed by the treatment of the obtained 3-(4-formylphenoxy)propane-1-
sulfonic acid (6) with 2-acetylpyridine (7) and AcONH4 in acetamide at 150 °C for 5 h gave terpyridine
ligand 8 in 68% yield in two steps. Immobilization of terpyridine ligand 8 onto an amphiphilic PE-PEG
resin through ionic bonds5f to the sulfonate group was performed in DMF at room temperature for 1 h and
the complexation of an amphiphilic PS-PEG resin-bound terpyridine ligand and Cu(I) occurred in CH2Cl2
to give PS-PEG-terpyridine-Cu(I) complex 1 as a green solid.
Scheme 1. Preparation of PS-PEG-terpyridine Cu(I) Complex and Application to the [3+2] Cycloaddition
Reaction
OH
O
S
O
N
N
O
O
O
O
S
7
S
O
H
O
H
O
N
O
HO
HO
O
AcONH4
NaOH, IPA, 100 °C, 3 h
84% yield
O
AcNH2, 150 °C
N
5
6
8
82% yield
N
Cu
N
1)
PS
O
O
n NH2
O
in DMF
+
–O
S
PS
N
I
O
O
n NH3
O
2)
CuI, CH2Cl2
O
PS-PEG-terpyridine-Cu
1
CO2Me
CO2Me
Cat. 1
N3
N
MeO2C
CO2Me
+
N
H2O
N

HETEROCYCLES, Vol. 81, No. 3, 2010
603
To explore the catalytic activity of the resin-supported complex in water, we studied the copper-catalyzed
Huisgen [3+2] cycloaddition reaction of acetylenes and azides in water, which is the first example of
Huisgen [3+2] cycloaddition using a reusable heterogeneous catalyst in water. On screening reaction
conditions for copper-catalyzed [3+2] cycloaddition with polymeric copper 1, we found that the reaction
efficiency was greatly enhanced by the solvent used. Thus, the coupling of benzyl azide (2a) and
phenylacetylene (3e) was performed in water with polymeric catalyst 1 (5 mol % to Cu) at 40 °C for 6 h
in the solvent. The reaction mixture was filtered and the recovered resin beads were rinsed with a small
amount of water and extracted with EtOAc to give 1-benzyl-4-phenyl-1H-1,2,3-triazole (4e). The most
effective solvent was water, as seen in the results summarized in Table 1. The coupling in toluene,
CH2Cl2, CHCl3, DMSO, and DMF gave 4e in 33%, 19%, 24%, 26%, and 18% yields, respectively. The
use of IPA improved the coupling performance to afford 1-benzyl-4-phenyl-1H-1,2,3-triazole (4e) in 71%
yield. When water was used as the solvent, the [3+2] cycloaddition reaction proceeded smoothly, with a
significant increase in the chemical yield of 4e to 87% (Table 1).9
Table 1. Solvent Effect of [3+2] Huisgen Cycloaddition Reactiona
Cat. 1 (5 mol %)
N3
N
+
N
in H2O, 40 °C, 6 h
N
2a
3e
4e
Entry
Solvent
Yield (%)
1
2
3
4
5
6
7
H2O
toluene
CH2Cl2
CHCl3
DMSO
DMF
87
33
19
24
26
18
71
IPA
a All reactions were performed with Bn-N3 (2a; 0.6 mmol) and phenylacetylene (3e; 0.4 mmol) in the
presence of polystyrene-poly(ethylene glycol)-supported copper-terpyridine complex 1 in 3.0 mL of
solvent at 40 °C for 6 h under aerobic conditions.

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HETEROCYCLES, Vol. 81, No. 3, 2010
The scope of azides and acetylenes was examined for the Huisgen [3+2] cycloaddition reaction in water
using PS-PEG-terpyridine Cu(I) 1. The representative results are summarized in Table 2. PS-PEG
resin-supported terpyridine copper(I) complex 1 efficiently catalyzed the coupling of benzyl azide (2a)
and n-nonanyl azide (2b) with dimethyl acetylenedicarboxylate (3a) to afford triazoles 4a and 4f in 82%
and 54% yields, respectively (entries 1 and 6). The Huisgen [3+2] cycloaddition reaction of benzyl
azide (2a) with various acetylenes 3b–3e proceeded to give the corresponding ethyl
1-benzyl-1H-1,2,3-triazole-4-carboxylate (4b), 1-benzyl-4-(phenoxymethyl)-1H-1,2,3-triazole (4c),
(1-benzyl-1H-1,2,3-triazol-4-yl)methyl acetate (4d), and 1-benzyl-4-phenyl-1H-1,2,3-triazole (4e) in 77%,
59%, 71%, and 87% yields, respectively. The coupling reaction of alkyl azide 2b with various acetylenes
3b–3e also proceeded to give the corresponding ethyl 1-nonyl-1H-1,2,3-triazole-4-carboxylate (4g),
1-nonyl-4-phenoxy-1H-1,2,3-triazole (4h), (1-nonyl-1H-1,2,3-triazol-4-yl)methyl acetate (4i), and
1-nonyl-4-phenyl-1H-1,2,3-triazole (4j) in 67%, 45%, 44%, and 56% yields, respectively.
The recyclability of the PS-PEG-Terpyridine Cu(I) 1 was examined for the Huisgen [3+2] cycoaddition
reaction of benzyl azide with phenylacetylene. Thus, after the first reaction, which gave 82% of
dimethyl 1-benzyl-1H-1,2,3-triazole-4,5-dicarboxylate (4a), the catalyst was recovered by simple
filtration, washed with water, dried under vacuum, and reused three times under similar reaction
conditions to give 4e in 83%, 85%, and 85% yields (Scheme 2). After recycling experiments, ICP-AES
analysis showed that leaching of Cu to the aqueous solution was 6 ppm.
Scheme 2. Catalyst Recycling Experiments
PS-PEG-terpyridine-Cu 1
CO2Me
(5 mol % Cu)
N3
MeO2C
CO2Me
N
+
CO2Me
in H2O
N
N
40 °C, 6 h
2a
3a
0.4 mmol
4a
0.6 mmol
83% yield (1st reuse)
85% yield (2nd reuse)
85% yield (3rd reuse)
In conclusion, we have developed a novel polymer-supported terpyridine-copper complex through ionic
bonds to the sulfonate group, which efficiently catalyzed the Huisgen [3+2] cycoaddition reaction of
benzyl or alkyl azides with acetylenes in water under aerobic conditions to give the corresponding
triazoles in high yield and high regioselectivity. This catalyst was recovered and reused several times
without any loss of catalytic activity. Further extensive scope of the Huisgen [3+2] cycoaddition
reaction and application of this catalyst to the other organic transformations are in progress in our lab.

HETEROCYCLES, Vol. 81, No. 3, 2010
605
Table 2. Huisgen [3+2] cycloaddition reaction of benzyl azide and acetylenes with polymeric catalyst 1
in water a
R3
Cat. 1 (5 mol %)
R1
N
N
4
R2
R1 N3
R2
R3
+
in H2O, 40 °C, 6 h
N
2
3
Entry
1
Azide
Alkyne
Product (4)
Yield
(%)
CO2Me
CO2Me
N3
N
N
MeO2C
CO2Me
82
77
59
N
3a
2a
4a
N3
N
N
CO2Et
2
3
CO2Et
N
3b
2a
4b
N3
N
N
O
OPh
N
2a
4c
3c
N3
N
N
4
5
6
OAc
OAc
N
71
87
3d
2a
4d
N3
N
N
N
2b
3e
3a
4e
CO2Me
C8H17
N3
C8H17
N
N
MeO2C
CO2Me
CO2Me
54
67
2b
N
4f
C8H17
N
N
CO2Et
7
8
C8H17
N3
CO2Et
N
2b
3b
4g
C8H17
C8H17
C8H17
N
C8H17
N3
N3
N3
O
N
OPh
N
45
44
56
2b
4h
3c
N
C8H17
9
N
OAc
OAc
N
2b
3d
4i
N
C8H17
10
N
N
2b
4j
3e
a All reactions were performed with R-N3 (2; 0.6 mmol) and acetylene (3; 0.4 mmol) in the presence of
polystyrene-poly(ethylene glycol)-supported copper-terpyridine complex 1 in 3.0 mL of water at 40 °C
for 6 h under aerobic conditions.

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EXPERIMENTAL
General Methods:
All manipulations were carried out under aerobic conditions. Water was deionized with a Millipore
system as Milli-Q grade. NMR spectra were recorded on a JEOL JNM-LA 500 spectrometer (500 MHz
1
for H and 125 MHz for C). H and C NMR spectra were recorded in CDCl3 or DMSO at 25 °C.
13
1
13
1
Chemical shifts were reported in ppm referenced to an internal tetramethylsilane standard for H NMR.
Chemical shifts of 13C NMR were given relative to CDCl3 and DMSO as an internal standard (δ 77.0 ppm
and 39.7 ppm). Mass spectral data were measured on a Shimadzu Qp2010 MS detector (GC-MS) and a
Hitachi M-2500 (GC-MS) and JEOL JMS-T100LP (LC-MS); the abbreviation ‘bp’ is used to denote the
base peak. ICP-AES spectral data were measured on a Shimadzu ICPE-9000.
Materials:
PS-PEG-supported catalyst 1 was prepared from PS-PEG amino-resin7 (Tenta Gel S NH2, average
diameter 90 mm, 1% divinylbenzene cross-linked, loading value of amino residue 0.31 mmol/g;
purchased from RAPP POLYMERE) and terpyridine ligand according to the reported procedures.10
Synthesis:
Preparation of 3-(4-formylphenoxy)propane-1-sulfonic acid (6).
To
a
solution of
p-hydroxybenzaldehyde (10.0 g, 82 mmol) in 2-propanol (100 mL) was added KOH (4.6 g, 82 mmol).
The resulting mixture was stirred until it became homogeneous under ultrasonic wave irradiation
conditions. To a reaction mixture was added propane sultone (10.0 g, 82 mmol) in 2-propanol (50 mL)
and the reaction mixture was stirred at 100 °C until it became generating the solid. The generated solid
was collected by filtration, washed with 2-propanol, and dried under vaccum to gave compound 6 in 84%
yield (19.2 g), which was used directly in the next step.
Preparation
of
3-(4-(terpyridin-4'-yl)phenoxy)propane-1-sulfonic
acid
(8).
3-(4-formylphenoxy)propane-1-sulfonic acid (6) (12.2 g, 50 mmol), acetamide (88.6 g, 1.5 mol),
ammonium acetate (57.8 g, 0.75 mol) and 2-acetylpyridine (12.1 g, 0.10 mol) were stirred at 150 °C for
2 h. The reaction mixture was cooled until 40 °C and added NaOH (45 g, 1.1 mol) in H2O (200 mL) at
100 °C. The reaction mixture was stirred for overnight at 100 °C to generate the yellow solid. The
solid was corrected by filtration, washed with H2O, and dried under vacuum to give a pale yellow solid.
Purification of the pale yellow solid via recrystallization from H2O gave the
3-(4-(terpyridin-4'-yl)phenoxy)propane-1-sulfonic acid (8) in 82% yield (18.3 g, 41 mmol). 1H NMR
(DMSO-d6) δ 8.78-8.77 (m, 2 H), 8.68-8.66 (m, 4 H), 8.03 (td, J = 7.5, 1.7 Hz, 2 H), 7.88 (d, J = 8.7 Hz,
2 H), 7.55-7.51 (m, 2 H), 7.13 (d, J = 8.7 Hz, 2 H), 4.17 (t, J = 6.8 Hz, 2 H), 2.64 (t, J = 7.3 Hz, 2 H),
2.52-2.51 (m, 1 H), 2.11-2.06 (m, 2 H): 13C NMR (DMSO-d6) δ 160.0, 155.7 (2C), 155.2 (2C), 149.5
(2C), 149.2, 137.6 (2C), 130.9, 129.5 (2C), 128.3 (2C), 124.6 (2C), 121.0 (2C), 117.4 (2C), 67.1, 48.0,

HETEROCYCLES, Vol. 81, No. 3, 2010
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25.4. ESI-HRMS calcd for C24H21N3O4SNa 470.1150, found 470.1154.
Preparation of immobilized copper complex 1:
A Merrifield vessel was charged with PS-PEG-NH2 (0.80 g, 0.24 mmol), 8 (165 mg, 0.37 mmol), and
DMF, and the reaction mixture was shaken on a shaking machine (CM-1000) at 25 °C for 1 h.
Complete consumption of the primary amino residue of the resin was monitored by Kaiser negative test.
The reaction mixture was filtered and the resin was washed with DMF and CH2Cl2. The resin was dried
under reduced pressure to give the polymer-supported 3-(4-(terpyridin-4'-yl)phenoxy)propane-1-sulfonate
(total loading: 0.24 mmol), which was used directly in the next step. A Merrifield vessel was charged
with resin-supported 3-(4-(terpyridin-4'-yl)phenoxy)propane-1-sulfonate (loading value: 0.24 mmol) and
20 mL of CH2Cl2. To this suspension was added 53.2 mg of copper(I) iodine (0.28 mmol) and the
mixture was shaken on a shaking machine (CM-1000) at 25 °C for 10 min. After filtration, the resin
was washed with CH2Cl2 and dried under reduced pressure to give polymer-supported copper complex 1
(lording value: 0.26 mmol/g).
Copper-catalyzed Cycloaddition Reaction of benzyl azide with phenylacetylene:
To a mixture of the polymeric catalyst 1 (76 mg, 0.020 mmol) and benzyl azide (2a; 79.8 mg, 0.60 mmol)
in H2O (3.0 mL) was added phenylacetylene (3e; 40.8 mg, 0.40 mmol). The reaction mixture was
shaken at 40 °C for 6 h and filtered. The recovered resin beads were rinsed with H2O and extracted
three times with EtOAc (6 mL). The EtOAc layer was separated and the aqueous layer was extracted
with EtOAc (5 mL). The combined EtOAc extracts were washed with brine (2 mL), dried over MgSO4,
and concentrated in vacuo. The resulting residue was chromatographed on silica gel (hexane-EtOAc,
10:1) to give 81.6 mg (87% yield) of 1-benzyl-4-phenyl-1H-1,2,3-triazole (4e). 1H NMR (CDCl3) δ
7.81-7.78 (m, 2 H), 7.66 (s, 1 H), 7.41-7.37 (m, 5 H), 7.33-7.30 (m, 3 H), 5.57 (s, 2 H): 13C NMR
(CDCl3) δ 148.1, 134.6, 130.4, 129.0 (2C), 128.7, 128.7 (2C), 128.0 (2C), 127.9 (2C), 125.6, 119.4, 54.1.
MS (EI): m/z (rel%) 235 (8, M+), 206 (30), 116 (bp), 91 (87).
Dimethyl 1-benzyl-1H-1,2,3-triazole-4,5-dicarboxylate (4a): 1H NMR (CDCl3) δ 7.35-7.32 (m, 3 H),
7.26-7.25 (m, 2 H), 5.81 (s, 2 H), 3.96 (s, 3 H), 3.87 (s, 3 H): 13C NMR (CDCl3) δ 160.3, 158.7, 140.1,
133.1, 129.1 (2C), 128.9 (2C), 128.8, 127.9, 53.9, 53.2, 52.6. MS (EI): m/z (rel%) 216 (2, M+ –
COOMe), 214 (6), 174 (6), 156 (10), 130 (12), 91 (bp).
Ethyl 1-benzyl-1H-1,2,3-triazole-4-carboxylate (4b): 1H NMR (CDCl3) δ 8.02 (s, 1 H), 7.39-7.37 (m,
3 H), 7.30-7.28 (m, 2 H), 5.57 (s, 2 H), 4.38 (q, J = 7.0 Hz, 2 H), 1.37 (t, J = 7.0 Hz, 3 H): 13C NMR
(CDCl3) δ 160.5, 140.4, 133.6, 129.1 (2C), 128.9 (2C), 128.1, 127.2, 61.1, 54.3, 14.1. MS (EI): m/z
(rel%) 231 (1, M+), 202 (2), 174 (18), 130 (25), 91 (bp).
1-Benzyl-4-phenoxy-1H-1,2,3-triazole (4c): 1H NMR (CDCl3) δ 7.53 (s, 1 H), 7.38-7.35 (m, 3 H),
7.30-7.26 (m, 4 H), 6.96-6.95 (m, 3 H), 5.53 (s, 2 H), 5.19 (s, 2 H): 13C NMR (CDCl3) δ 158.1, 144.5,

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HETEROCYCLES, Vol. 81, No. 3, 2010
134.2, 129.5 (2C), 129.1 (2C), 128.8, 128.1 (2C), 122.6, 121.2, 114.7 (2C), 61.9, 54.3. MS (EI): m/z
(rel%) 265 (7, M+), 172 (13), 144 (41), 91 (bp).
1
(1-Benzyl-1H-1,2,3-triazol-4-yl)methyl acetate (4d): H NMR (CDCl3) δ 7.53 (s, 1 H), 7.37-7.35 (m, 3
H), 7.28-7.27 (m, 2 H), 5.52 (s, 2 H), 5.18 (s, 2 H), 2.05 (s, 3 H): 13C NMR (CDCl3) δ 170.7, 143.1,
134.3, 129.0 (2C), 128.7 (2C), 128.0, 123.5, 57.5, 54.1, 20.7. MS (EI): m/z (rel%) 231 (2, M+), 188 (18),
161 (10), 144 (6), 91 (bp).
1
Dimethyl 1-nonyl-1H-1,2,3-triazole-4,5-dicarboxylate (4f): H NMR (CDCl3) δ 4.58 (t, J = 7.3 Hz, 2
H), 4.00 (s, 3 H), 3.97 (s, 3 H), 1.92-1.86 (m, 2 H), 1.31-1.25 (m, 12 H), 0.87 (t, J = 6.8 Hz, 3 H): 13C
NMR (CDCl3) δ 160.5, 159.0, 139.8, 129.8, 53.3, 52.6, 50.6, 31.7, 30.2, 29.2, 29.0, 28.8, 26.2, 22.5, 14.6.
MS (EI): m/z (rel%) 280 (6, M+ – OMe), 252 (bp), 224 (25), 154 (37), 140 (37), 126 (27).
1
Ethyl 1-nonyl-1H-1,2,3-triazole-4-carboxylate (4g): H NMR (CDCl3) δ 8.09 (s, 1 H), 4.46-4.40 (m, 4
H), 2.07-1.90 (m, 2 H), 1.41 (t, J = 7.0 Hz, 3 H), 1.32-1.26 (m, 12 H), 0.87 (t, J = 7.0 Hz, 3 H): 13C
NMR (CDCl3) δ 160.7, 140.1, 127.1, 61.1, 50.6, 31.6, 30.0, 29.1, 29.0, 28.8, 26.2, 22.5, 14.2, 13.9. MS
(EI): m/z (rel%) 222 (16, M+ – OEt), 210 (14), 168 (45), 154 (62), 152 (75), 130 (50), 96 (83), 83 (bp).
1
1-Nonyl-4-phenoxy-1H-1,2,3-triazole (4h): H NMR (CDCl3) δ 7.59 (s, 1 H), 7.31-7.27 (m, 2 H),
7.00-6.95 (m, 3 H), 5.22 (s, 2 H), 4.34 (t, J = 7.0 Hz, 2 H), 1.91-1.89 (m, 2 H), 1.31-1.25 (m, 12 H), 0.87
(t, J = 7.0 Hz, 3 H): 13C NMR (CDCl3) δ 158.1, 144.0, 129.5 (2C), 122.4, 121.2, 114.7 (2C), 61.9, 50.6,
31.7, 30.2, 29.2, 29.1, 28.9, 26.4, 22.6, 14.0. MS (EI): m/z (rel%) 301 (13, M+), 180 (bp), 94 (51).
(1-Nonyl-1H-1,2,3-triazol-4-yl)methyl acetate (4i): 1H NMR (CDCl3) δ 7.60 (s, 1 H), 5.21 (s, 2 H), 4.34
(t, J = 7.31 Hz, 2 H), 2.08 (s, 3 H), 1.95-1.87 (m, 2 H), 1.32-1.26 (m, 12 H), 0.87 (t, J = 6.5 Hz, 3 H):
13C NMR (CDCl3) δ 170.8, 142.6, 123.4, 57.6, 50.3, 31.7, 30.1, 29.2, 29.0, 28.8, 26.3, 22.5, 20.8, 13.9.
MS (EI): m/z (rel%) 267 (4, M+), 224 (37), 168 (35), 154 (87), 126 (41), 98 (39), 84 (bp).
1-Nonyl-4-phenyl-1H-1,2,3-triazole (4j): 1H NMR (CDCl3) δ 7.85-7.81 (m, 2 H), 7.74 (s, 1 H), 7.42 (t, J
= 7.8 Hz, 2 H), 7.35-7.32 (m, 1 H), 4.40 (t, J = 7.3 Hz, 2 H), 1.97-1.92 (m, 2 H), 1.35-1.26 (m, 12 H),
0.87 (t, J = 7.0 Hz, 3 H): 13C NMR (CDCl3) δ 147.6, 130.6, 128.8 (2C), 128.0, 125.6 (2C), 119.3, 50.4,
31.7, 30.3, 29.3, 29.1, 28.9, 26.4, 22.6, 14.0. MS (EI): m/z (rel%) 271 (8, M+), 242 (8), 172 (20), 145
(29), 117 (bp), 104 (35).
ACKNOWLEDGEMENTS
We are grateful for financial support from the Young Scientists Program of University of the Ryukyus,
and this work was the Joint Study in Cooperative Research Center.
REFERENCES AND NOTES
1. R. Huisgen, In 1,3-Dipolar Cycloaddition Chemistry; ed. by A. Padwa; Wiley: New York, 1984.

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