Copper-catalyzed direct cross coupling of 1,3,4-oxadiazoles with trans-β-halostyrenes: Synthesis of 2-E-vinyl 1,3,4-oxadiazoles

Article abstract of DOI:10.1016/j.tet.2011.10.049

The first direct C-H alkenylation of 1,3,4-oxadiazoles with trans-β-halo olefinic system has been carried out using a combination of CuI/DMEDA as a catalyst. A wide range of 2-E-vinyl-substituted oxadiazoles were obtained in high yields (85-93%).

Full text of DOI:10.1016/j.tet.2011.10.049

Tetrahedron 68 (2012) 300e305
Contents lists available at SciVerse ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Copper-catalyzed direct cross coupling of 1,3,4-oxadiazoles with
trans-
b
-halostyrenes: synthesis of 2-E-vinyl 1,3,4-oxadiazolesq
*
Biswanath Das , Gandolla Chinna Reddy, Penagaluri Balasubramanyam, N. Salvanna
Organic Chemistry Division-I, Indian Institute of Chemical Technology, Uppal Road, Hyderabad 500007, Andhra Pradesh, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 14 July 2011
Received in revised form 11 October 2011
Accepted 13 October 2011
Available online 20 October 2011
The first direct CeH alkenylation of 1,3,4-oxadiazoles with trans-b-halo olefinic system has been carried
out using a combination of CuI/DMEDA as a catalyst. A wide range of 2-E-vinyl-substituted oxadiazoles
were obtained in high yields (85e93%).
Ó 2011 Elsevier Ltd. All rights reserved.
Keywords:
CeH activation
1,3,4-Oxadiazole
trans-b-Halostyrenes
Copper iodide
Alkenylation
1. Introduction
a method for the Cu-catalyzed alkenylation of polyfluoroarene CeH
bond with alkenyl bromides.5b In 2010 Charette’s group pursued
The widespread application of heteroarenes in medicinal
chemistry and in material science has driven the development of
new synthetic strategies to prepare appropriately substituted het-
erocyclic cores. Metal-catalyzed direct functionalization of CeH
bond of heteroarenes is great importance in recent organic syn-
thesis to generate molecular complexity.1 In fact, the trans-
formation of CeH to CeC bond in the presence of a metal catalyst is
a highly valuable preparative reaction because of its atom economy.
Thus various arenes and heteroarenes have been subjected to direct
arylation,2 alkenylation,3 and alkynylation4 using different catalyst
systems. A wide range of metal catalysts including palladium,
rhodium, or ruthenium have been exploited for these trans-
formations. However, the use of copper catalyst remains quite rare,
despite clear advantages in their availability and cost-effectiveness.
Moreover, to our knowledge, metal-mediated creation of an
alkenyl-heteroaryl linkage between an sp2-hybridized heteroaryl
carbon of 1,3,4-oxadiazole and an sp2-hybridized carbon of alkenyl
halide using CeH bond activation has also not yet been reported.
In recent years, replacing the expensive metal catalysts with
more abundant and less expensive ones to execute similar CeH
activation has attracted great interest.5a Daugulis et al. developed
investigation into the CeH alkenylation of N-benzoyliminopyr-
idinium ylides with alkenyl iodides in presence of copper catalyst.5c
Grierson et al. reported direct alkenylation of oxazoles with vinyl
bromides using copper iodide as catalyst.3a However, alkenylation
of electron deficient heteroarenes such as oxadiazoles by CeH ac-
tivation still has not been reported.
Oxadiazole derivatives possess a wide range of biological
properties.6 They are known to work as ester and amide bio-
isosteres.7 They also exhibit anti-microbial and anti-convulsant
activities.8 Some of the compounds are employed in the field of
organic electronics.9 Thus the synthesis of oxadiazole derivatives is
an useful task in pharmaceutical and material science. Herein, we
report a copper catalyzed efficient and convenient method for
alkenylation of 1,3,4-oxadiazoles.
2. Results and discussion
In continuation of our work on the development of useful syn-
thetic methodologies10 we have observed that 1,3,4-oxadiazoles
underwent direct alkenylation with trans-b-iodostyrenes in the
presence of CuI using a ligand, N,N0-dimethylethylene diamine
(DMEDA) and LiO-t-Bu (Scheme 1).
Initially we considered 2-phenyl 1,3,4-oxadiazole (1a; R1¼Ph)
and trans-
b
-halostyrene (2a; R2¼Ph) as the starting materials for
q
Part 225 in the series, ‘Studies on novel synthetic methodologies’.
the optimization of the reaction conditions. The reaction was
screened with different copper compounds, ligands, and bases
* Corresponding author. Tel./fax: þ91 40 27160512; e-mail address: biswa-
nathdas@yahoo.com (B. Das).
0040-4020/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2011.10.049

B. Das et al. / Tetrahedron 68 (2012) 300e305
301
Table 2
CuI (0.05 mmol)
DMEDA (0.05 mmol)
R2
N
O
N
O
Optimization of solvent and temperaturea
N
N
I
R2
(0.05 mmol)
CuI
LiO-t-Bu (1.0 mmol)
R1
R1
DMSO, 70 oC
3 h
DMEDA (0.05 mmol)
LiO-t-Bu
N
N
N
O
(0.50 mmol)
2
(0.50 mmol)
1
N
Ph
I
(1.0 mmol)
3h.
+
( 85-93 %)
3
Ph
Ph
solvent (2 mL),
O
Ph
temperature (T oC)
Scheme 1. Copper-catalyzed CeC cross coupling of 1,3,4-oxadiazoles.
a
3
1a (0.50 mmol) 2a (0.50 mmol)
Entry
Solvent
Temp
Yieldb
(%)
(Table 1). The coupling was also conducted in various solvents at
different temperatures (Table 2). The following ligands (Fig. 1) were
used to study the present conversion.
(ꢀC)
1
2
3
4
5
6
7
8
DMSO
DMSO
DMSO
DMF
rtc
70
110
rtc
70
rtc
70
rtc
70
45
85
85
30
63
25
67
35
70
70
10
25
25
45
Table 1
Standardization of copper source, ligand, and basea
DMF
1,4-Dioxane
1,4-Dioxane
Toluene
Toluene
Toluene
THF
THF
Water
Water
Cu source
(0.05 mmol)
ligand (0.05 mmol)
(1.0 mmol)
N
O
N
N
N
X
Ph
base
+
9
Ph
DMSO (2 mL), 3h.
10
11
12
13
14
Reflux
O
70 (T oC)
Ph
Ph
rtc
3a
2a (0.50 mmol)
1a (0.50 mmol)
70
rtc
Entry
X
Cu source
Ligand
Base
Yieldb
(%)
70
a
Reaction conditions: 2-phenyl 1,3,4-oxadiazole 1 (0.50 mmol), trans-b-iodos-
1
2
3
4
5
6
7
8
I
Br
I
None
CuI
CuI
CuI
CuI
CuI
CuI
CuI
CuI
None
None
None
Acac
Acac
Acac
Phen
Phen
LiO-t-Bu
LiO-t-Bu
LiO-t-Bu
LiO-t-Bu
LiO-t-Bu
LiO-t-Bu
KO-t-Bu
LiO-t-Bu
LiO-t-Bu
LiO-t-Bu
LiO-t-Bu
LiO-t-Bu
LiO-t-Bu
LiO-t-Bu
LiO-t-Bu
KO-t-Bu
NaO-t-Bu
LiO-t-Bu
KO-t-Bu
LiO-t-Bu
LiO-t-Bu
Cs2CO3
0
0
0
55
45
0
tyrene 2 (0.50 mmol), CuI (0.05 mmol), DMEDA (0.05 mmol), LiO-t-Bu (1.0 mmol),
solvent (2 mL).
b
Isolated yield after column chromatography.
Room temperature, approximately 27 ꢀC.
c
I
Br
Cl
I
I
Br
I
Br
I
Br
I
I
I
I
I
I
I
I
I
I
9
O
O
H
N
Me
62
56
85
76
50
35
10
40
30
22
65
26
5
N
H
COOH
Me
N
H
9
Phen
Me
Me
10
11
12
13
14
15
16
17
18
19
20
21
22
23
CuI
CuI
DMEDA
DMEDA
DMEDA
DMEDA
DMEDA
DMEDA
DMEDA
DMEDA
TMEDA
TMEDA
N,N'-dimethylethylenediamine
acetyl acetone
L-Proline
(Acac)
(DMEDA)
CuBr
CuBr
CuCl
CuO
CuI
CuI
CuI
CuI
CuI
Me
Me
N
N
Me
Me
N
N
1,10-Phenantroline
N,N,N',N'-Tetramethylethanediamine
(Phen)
L-Proline
(TMEDA)
Cu(OTf)2
CuI
CuI
DMEDA
DMEDA
DMEDA
12
0
0
Fig. 1. Ligands used in copper-catalyzed CeC cross coupling of 1,3,4-oxadiazoles.
KHMDSc
a
Reaction conditions: 2-phenyl oxadiazole 1 (0.50 mmol), trans-
b-halostyrene 2
The effect of solvent and temperature was also studied for the
above reaction. Among all of the used solvents DMSO was most
effective at 70 ꢀC (Table 2). The reaction was complete in 3 h and
the alkenylation product 3a (R1¼R2¼Ph) was formed in a yield of
85%. No side product could be detected.
(0.50 mmol), Cu source (0.05 mmol), ligand (0.05 mmol), base (1.0 mmol), DMSO
(2 mL) at 70 ꢀC over 3 h.
b
Isolated yield of 3 after column chromatography.
c
Potassium bis(trimethyl silyl)-amide.
Following the standardization of the above reaction, with effec-
tive reaction conditions (Table 1, entry 10) the CeH functionalization
of a series of 1,3,4-oxadiazole derivatives was carried out to prepare
several new products using different trans-b-iodostyrenes (Table 3).
The oxadiazoles containing electron-donating as well as
electron-withdrawing groups in the aromatic ring underwent
In absence of the Cu source and ligand the reaction did not
proceed (Table 1, entry 1). trans-
any product (entry 6), while trans-
product with moderate yield in the presence of Cu source and li-
gand (entries 2, 5, 9, 13). However, trans- -bromostyrene gave the
desired product in high yield using the combination of CuI/DMEDA
and LiO-t-Bu (entry 11). The other olefinic compound, trans-
b
-Chlorostyrene could not afford
b-bromostyrene furnished the
b
conversion smoothly. The trans-b-iodo olefins (2) having hetero-
b
-
aromatic moiety also afforded the desired products in high yield.
For each conversion the reaction time was 3 h. The structures of the
products were established from their spectral (IR, 1H and 13C NMR,
and HRMS) data.
Although the exact mechanism still remains unknown for this
new process, plausible mechanism11 is shown in Scheme 2. This
mechanism involves the base assisted transmetallation of 1,3,4-
oxadiazole to form (heteroaryl) Cu (I) intermediate A. Oxidative
iodostyrene afforded the product in various yields depending on
the application of Cu sources, ligands, and bases. Among various Cu
sources, CuI was found to be most effective. The choice of the ligand
was also crucial in this alkenylation reaction; DMEDA showed
highest efficiency (entry 10). Phen (entry 8) and TMEDA (entry 18)
also revealed considerable efficiency. However, among the used
bases LiO-t-Bu was most effective but other bases were not useful.
From this study it was evident that the alkenylation of 2-phenyl
addition of trans-b-iodostyrene to A to form the copper(III) complex
1,3,4-oxadiazole with trans-
b
-iodostyrene in the presence of CuI/
B followed by reductive elimination leads to the formation of ex-
DMEDA and LiO-t-Bu can proceed efficiently (entry 10).
pected alkenylated product.

302
B. Das et al. / Tetrahedron 68 (2012) 300e305
Table 3
4. Experimental section
4.1. General
Copper-catalyzed direct alkenylation of oxadiazoles with various trans-b-
halostyrenesa
CuI (0.05 mmol)
R2
N
N
O
N
DMEDA (0.05 mmol)
N
X
Melting points were measured on a Buchi 510 apparatus and are
uncorrected. The Spectra were recorded with the following in-
struments. IR: PerkineElmer RX1 FT-IR spectrophotometer; NMR:
Varian Gemini 200 MHz (1H) and 50 MHz (13C) spectrometer;
ESIMS: VG-Autospec micromass (70 eV) and HRMS: Hybrid MS
system (Indian Institute of Chemical Technology). Analytical thin
layer chromatography (TLC) was carried out using silica gel 60 F254
pre-coated plates. Visualization was accomplished with UV lamp or
I2 stains. Organic extracts were dried over anhydrous Na2SO4.
O
R2
LiO-t-Bu (1.0 mmol)
DMSO (2 mL), 70 oC
3 h
R1
R1
3
1
2
X = I, Br
Entry
R1 (1)
C6H5
4-CH3eC6H4
4-OCH3eC6H4
4-CleC6H4
4-CF3eC6H4
C6H5
4-CH3eC6H4
4-OCH3eC6H4
4-CleC6H4
4-CF3eC6H4
3,4,5-(OMe)3eC6H2
C6H5
R2 (2)
Product
Yieldb,c
(%)
(3)
1
2
3
4
5
6
7
8
C6H5
C6H5
C6H5
C6H5
3a
3b
3c
3d
3e
3f
3g
3h
3i
3j
3k
3l
3m
3n
85 (76)
91
93 (82)
87
89 (78)
86
4.2. General procedure for alkenylation of 2-aryl 1,3,4-
oxadiazoles (3)
C6H5
4PheC6H4
4PheC6H4
4PheC6H4
4PheC6H4
4PheC6H4
4PheC6H4
3,4(OMe)2eC6H3
3,4(OMe)2eC6H3
3,4(OMe)2eC6H3
90
91
85
88
In a 10 mL round bottom flask under nitrogen atmosphere, CuI
(9 mg, 0.05 mmol), DMEDA (4.5 mg, 0.05 mmol), LiO-t-Bu (80 mg,
1.0 mmol), 2-aryl-1,3,4-oxadiazole (0.50 mmol), and trans-b-
9
10
11
12
13
14
93 (78)
91 (81)
90
iodostyrene (0.50 mmol) in DMSO (2.0 mL) were taken. The re-
action mixture was stirred at 70 ꢀC for 3 h. The progress of the re-
action was monitored by TLC. After the consumption of the starting
materials, the reaction mixture was allowed to cool, and sub-
sequently extracted with EtOAc (2ꢁ10 mL). The combined organic
extracts were dried over anhydrous Na2SO4. Concentration in vacuo
followed by column chromatography (EtOAc/hexane: 5:95 to
10:90) gave pure compound 3 in 85e93% yield.
4-OCH3eC6H4
4-CF3eC6H4
88
Cl
15
16
C6H5
3o
3p
87
O
Cl
4-CH3eC6H4
88 (71)
O
Cl
4.3. Spectral data of all compounds are given below
17
4-CleC6H4
3q
85
O
4.3.1. (E)-2-Phenyl-5-styryl-1,3,4-oxadiazole (3a). Following Sec-
tion 4.2, CuI (9 mg, 0.05 mmol), DMEDA (4.5 mg, 0.05 mmol), LiO-t-
Bu (80 mg, 1.0 mmol), 2-phenyl-1,3,4-oxadiazole (73 mg,
a
Reaction conditions: 2-aryl 1,3,4-oxadiazole 1 (0.50 mmol), trans-b-iodostyrene
2 (0.50 mmol), CuI (0.05 mmol), DMEDA (0.05 mmol), LiO-t-Bu (1.0 mmol), DMSO
0.50 mmol), and trans-b-iodostyrene (115 mg, 0.50 mmol) in DMSO
(2 mL).
(2.0 mL) to give crude product, which was purified by column
chromatography (5% EtOAc/hexane) to give the product 3a (105 mg,
85%) as a white solid; Rf (15% EtOAc/hexane) 0.52; mp: 125e127 ꢀC;
b
Yield of isolated product using trans-
b
-iodostyrene.
c
In parenthesis: yield of isolated product when trans-
b-bromostyrene was used.
IR (KBr): 2390, 1643, 1521, 1445, 1265 cmꢂ1 1H NMR (200 MHz,
;
CDCl3):
d 8.12 (2H, d, J 8.0 Hz, AreH), 7.62e7.50 (6H, m, AreH,
CH]), 7.49e7.38 (3H, m, AreH), 7.11 (1H, d, J 14.0 Hz, ]CH); 13C
HN
CuI
NH
N
N
NMR (50 MHz, CDCl3): d 164.1, 139.0, 135.0, 131.8, 130.1, 129.1, 127.5,
127.2, 123.9, 110.2; ESIMS: m/z 249 [MH]þ; HRMS (ESI): [MH]þ,
R1
O
LiI+ tBuOH
found 249.1030. C16H13N2O requires 249.1027.
NH NH
Cu
LiO-t-Bu
4.3.2. (E)-2-Styryl-5-p-tolyl-1,3,4-oxadiazole (3b). Following Sec-
tion 4.2, CuI (9 mg, 0.05 mmol), DMEDA (4.5 mg, 0.05 mmol), LiO-t-
Bu (80 mg, 1.0 mmol), 2-p-tolyl-1,3,4-oxadiazole (80 mg,
I
R2
N
O
N
N
N
NH
R1
Cu
R1
0.50 mmol), and trans-b-iodostyrene (115 mg, 0.50 mmol) in DMSO
O
A
NH
(2.0 mL) to give crude product, which was purified by column
chromatography (5% EtOAc/hexane) to give the product 3b (118 mg,
91%) as a white solid; Rf (15% EtOAc/hexane) 0.49; mp: 127e129 ꢀC;
I
I-
NH
N
N
R2
+
IR (KBr): 2378, 1642, 1492, 1443, 1258 cmꢂ1 1H NMR (200 MHz,
;
Cu
CDCl3):
CH]), 7.41e7.28 (5H, m, AreH), 7.05 (1H, d, J 14.0 Hz, ]CH), 2.42
(3H, s, CH3); 13C NMR (50 MHz, CDCl3):
164.1, 142.3, 138.8, 134.9,
d 7.99 (2H, d, J 8.0 Hz, AreH), 7.60e7.52 (3H, m, AreH,
R1
O
NH
B
d
R2
130.1, 130.0, 129.2, 127.6, 126.9, 121.1, 110.0, 21.2; ESIMS: m/z 263
[MH]þ; HRMS (ESI): [MH]þ, found 263.1185. C17H15N2O requires
263.1184.
Scheme 2. Plausible mechanism of alkenylation.
3. Conclusions
4.3.3. (E)-2-(4-Methoxyphenyl)-5-styryl-1,3,4-oxadiazole
(3c). Following Section 4.2, CuI (9 mg, 0.05 mmol), DMEDA
(4.5 mg, 0.05 mmol), LiO-t-Bu (80 mg, 1.0 mmol), 2-(4-
methoxyphenyl)-1,3,4-oxadiazole (88 mg, 0.50 mmol), and trans-
In conclusion, we have developed for the first time an efficient
method for direct alkenylation of 1,3,4-oxadiazoles with trans-
b
-
iodo olefinic system using
a
combination of CuI/DMEDA as
b-iodostyrene (115 mg, 0.50 mmol) in DMSO (2.0 mL) to give crude
a catalyst.
product, which was purified by column chromatography (7% EtOAc/

B. Das et al. / Tetrahedron 68 (2012) 300e305
303
hexane) to give the product 3c (129 mg, 93%) as a white solid; Rf
(20% EtOAc/hexane) 0.51; mp: 135e137 ꢀC; IR (KBr): 2382, 1609,
127.9, 127.8, 127.0, 121.1, 110.0, 21.8; ESIMS: m/z 339 [MH]þ; HRMS
(ESI): [MH]þ, found 339.1511. C23H19N2O requires 339.1497.
1493, 1449, 1257 cmꢂ1 1H NMR (200 MHz, CDCl3):
; d 8.07 (2H, d, J
8.0 Hz, AreH), 7.65e7.52 (3H, m, AreH, CH]), 7.48e7.31 (4H, m,
4.3.8. (E)-2-(2-(Biphenyl-4-yl)vinyl)-5-(4-methoxyphenyl)-1,3,4-
oxadiazole (3h). Following Section 4.2, CuI (9 mg, 0.05 mmol),
DMEDA (4.5 mg, 0.05 mmol), LiO-t-Bu (80 mg, 1.0 mmol), 2-(4-
methoxyphenyl)-1,3,4-oxadiazole (88 mg, 0.50 mmol), and
AreH, ]CH), 7.02 (2H, d, J 8.0 Hz, AreH), 3.90 (3H, s, OCH3); 13C
NMR (50 MHz, CDCl3): d 162.9, 138.8, 135.1, 130.0, 129.1,128.9, 127.8,
116.3, 114.8, 110.2, 55.7; ESIMS: m/z 279 [MH]þ; HRMS (ESI): [MH]þ,
found 279.1136. C17H15N2O2 requires 279.1133.
trans-b-iodo-(4-phenyl)styrene (152 mg, 0.50 mmol) in DMSO
(2.0 mL) to give crude product, which was purified by column
chromatography (8% EtOAc/hexane) to give the product 3h
(161 mg, 91%) as a white solid; Rf (20% EtOAc/hexane) 0.42; mp:
4.3.4. (E)-2-(4-Chlorophenyl)-5-styryl-1,3,4-oxadiazole
(3d). Following Section 4.2, CuI (9 mg, 0.05 mmol), DMEDA
(4.5 mg, 0.05 mmol), LiO-t-Bu (80 mg, 1.0 mmol), 2-(4-
164e166 ꢀC; IR (KBr): 2394, 1610, 1494, 1451, 1256 cmꢂ1 1H NMR
;
chlorophenyl)-1,3,4-oxadiazole (90 mg, 0.50 mmol), and trans-
b
-
(200 MHz, CDCl3): d 8.05 (2H, d, J 8.0 Hz, AreH), 7.72e7.54 (7H,
iodostyrene (115 mg, 0.50 mmol) in DMSO (2.0 mL) to give crude
product, which was purified by column chromatography (6% EtOAc/
hexane) to give the product 3d (122 mg, 87%) as a white solid; Rf
(15% EtOAc/hexane) 0.42; mp: 140e142 ꢀC; IR (KBr): 2386, 1643,
m, AreH, CH]), 7.49e7.30 (3H, m, AreH), 7.10 (1H, d, J 14.0 Hz, ]
CH), 7.01 (2H, d, J 8.0 Hz, AreH), 3.91 (3H, s, OCH3); 13C NMR
(50 MHz, CDCl3):
d 162.7, 142.9, 140.0, 137.9, 134.1, 128.9, 128.8,
128.0, 127.9, 127.7, 127.1, 116.6, 114.5, 109.9, 55.2; ESIMS: m/z 355
[MH]þ; HRMS (ESI): [MH]þ, found 355.1460. C23H19N2O2 requires
355.1446.
1519, 1480, 1263 cmꢂ1
;
1H NMR (200 MHz, CDCl3):
d
8.01 (2H, d, J
8.0 Hz, AreH), 7.63e7.31 (8H, m, AreH, CH]), 7.02 (1H, d, J 14.0 Hz,
]CH); 13C NMR (50 MHz, CDCl3):
163.1, 139.3, 138.1, 134.5, 130.2,
d
129.8, 128.9, 128.2, 127.4, 125.5, 122.6, 109.8; ESIMS: m/z 283, 285
[MH]þ; HRMS (ESI): [MH]þ, found 283.0646. C16H12N2OCl [MH]þ
283.0638.
4.3.9. (E)-2-(2-(Biphenyl-4-yl)vinyl)-5-(4-chlorophenyl)-1,3,4-
oxadiazole (3i). Following Section 4.2, CuI (9 mg, 0.05 mmol),
DMEDA (4.5 mg, 0.05 mmol), LiO-t-Bu (80 mg, 1.0 mmol), 2-(4-
(trifluoromethyl)phenyl)-1,3,4-oxadiazole (107 mg, 0.50 mmol),
4.3.5. (E)-2-Styryl-5-(4-(trifluoromethyl)phenyl)-1,3,4-oxadiazole
(3e). Following Section 4.2, CuI (9 mg, 0.05 mmol), DMEDA
(4.5 mg, 0.05 mmol), LiO-t-Bu (80 mg, 1.0 mmol), 2-(4-(tri-
fluoromethyl)phenyl)-1,3,4-oxadiazole (107 mg, 0.50 mmol), and
and trans-b-iodo-(4-phenyl)styrene (152 mg, 0.50 mmol) in DMSO
(2.0 mL) to give crude product, which was purified by column
chromatography (6% EtOAc/hexane) to give the product 3i (152 mg,
85%) as a white solid; Rf (15% EtOAc/hexane) 0.51; mp: 158e160 ꢀC;
trans-
b-iodostyrene (115 mg, 0.50 mmol) in DMSO (2.0 mL) to give
IR (KBr): 2396, 1639, 1509, 1476, 1275 cmꢂ1 1H NMR (200 MHz,
;
crude product, which was purified by column chromatography (7%
EtOAc/hexane) to give the product 3e (140 mg, 89%) as a white
solid; Rf (20% EtOAc/hexane) 0.42; mp: 146e148 ꢀC; IR (KBr): 2382,
CDCl3):
7.54e7.35 (5H, m, AreH, CH]), 7.12 (1H, d, J 14.0 Hz, ]CH); 13C
NMR (50 MHz, CDCl3): 164.8, 143.2, 140.1, 139.0, 138.2, 133.7,
129.3, 128.9, 128.0, 127.9, 127.3, 126.6, 122.9, 109.5; ESIMS: m/z 359,
361 [MH]þ; HRMS (ESI): [MH]þ, found 359.0963. C22H16N2OCl re-
quires 359.0951.
d 8.09 (2H, d, J 8.0 Hz, AreH), 7.72e7.61 (7H, m, AreH),
d
1643, 1518, 1329, 1163 cmꢂ1; 1H NMR (200 MHz, CDCl3):
d
8.26 (2H,
d, J 8.0 Hz, AreH), 7.79 (2H, d, J 8.0 Hz, AreH), 7.64e7.52 (3H, m,
AreH, CH]), 7.46e7.38 (3H, m, AreH), 7.09 (1H, d, J 14.0 Hz, ]CH);
13C NMR (50 MHz, CDCl3):
d 162.9, 139.9, 134.4, 130.1, 129.2, 127.5,
127.2, 126.1, 109.2; ESIMS: m/z 317 [MH]þ; HRMS (ESI): [MH]þ,
4.3.10. (E)-2-(2-(Biphenyl-4-yl)vinyl)-5-(4-(trifluoromethyl)phenyl)-
1,3,4-oxadiazole (3j). Following Section 4.2, CuI (9 mg, 0.05 mmol),
DMEDA (4.5 mg, 0.05 mmol), LiO-t-Bu (80 mg, 1.0 mmol), 2-(4-
(trifluoromethyl)phenyl)-1,3,4-oxadiazole (107 mg, 0.50 mmol),
found 317.0904. C17H12N2OF3 requires 317.0901.
4.3.6. (E)-2-(2-(Biphenyl-4-yl)vinyl)-5-phenyl-1,3,4-oxadiazole
(3f). Following Section 4.2, CuI (9 mg, 0.05 mmol), DMEDA
(4.5 mg, 0.05 mmol), LiO-t-Bu (80 mg, 1.0 mmol), 2-phenyl-1,3,4-
and trans-b-iodo-(4-phenyl)styrene (152 mg, 0.50 mmol) in DMSO
(2.0 mL) to give crude product, which was purified by column
chromatography (7% EtOAc/hexane) to give the product 3j (172 mg,
88%) as a white solid; Rf (15% EtOAc/hexane) 0.43; mp: 201e203 ꢀC;
oxadiazole (73 mg, 0.50 mmol), and trans-b-iodo-(4-phenyl)sty-
rene (152 mg, 0.50 mmol) in DMSO (2.0 mL) to give crude product,
which was purified by column chromatography (5% EtOAc/hexane)
to give the product 3f (139 mg, 86%) as a white solid; Rf (15%
EtOAc/hexane) 0.48; mp: 130e132 ꢀC; IR (KBr): 2391, 1643, 1549,
IR (KBr): 2372, 1636, 1414, 1331, 1124 cmꢂ1 1H NMR (200 MHz,
;
CDCl3):
7.73e7.55 (7H, m, AreH, CH]), 7.49e7.31 (3H, m, AreH), 7.12 (1H,
d, J 14.0 Hz, ]CH); 13C NMR (50 MHz, CDCl3):
162.9, 143.1, 140.0,
d 8.26 (2H, d, J 8.0 Hz, AreH), 7.82 (2H, d, J 8.0 Hz, AreH),
1477, 1278 cmꢂ1
;
1H NMR (200 MHz, CDCl3):
d
8.18e8.02 (3H, m,
AreH), 7.70e7.31 (12H, m, AreH, CH]), 7.12 (1H, d, J 14.0 Hz, ]
CH); 13C NMR (50 MHz, CDCl3):
164.3, 142.8, 140.2, 138.7, 133.9,
d
139.3, 133.2, 128.9,128.1,128.0, 127.8, 127.2,127.0,126.1,111.9, 109.3;
ESIMS: m/z 393 [MH]þ; HRMS (ESI): [MH]þ, found 393.1218.
C23H16N2OF3 requires 393.1214.
d
132.8, 129.0, 128.9, 127.8, 127.6, 127.4, 126.7, 124.1, 109.9; ESIMS: m/
z 325 [MH]þ; HRMS (ESI): [MH]þ, found 325.1346. C22H17N2O re-
quires 325.1340.
4.3.11. (E)-2-(2-(Biphenyl-4-yl)vinyl)-5-(3,4,5-trimethoxyphenyl)-
1,3,4-oxadiazole (3k). Following Section 4.2, CuI (9 mg,
0.05 mmol), DMEDA (4.5 mg, 0.05 mmol), LiO-t-Bu (80 mg,
1.0 mmol), 2-(3,4,5-trimethoxyphenyl)-1,3,4-oxadiazole (118 mg,
4.3.7. (E)-2-(2-(Biphenyl-4-yl)vinyl)-5-p-tolyl-1,3,4-oxadiazole
(3g). Following Section 4.2, CuI (9 mg, 0.05 mmol), DMEDA
(4.5 mg, 0.05 mmol), LiO-t-Bu (80 mg, 1.0 mmol), 2-p-tolyl-1,3,4-
0.50 mmol),
and
trans-
b
-iodo-(4-phenyl)styrene
(152 mg,
oxadiazole (80 mg, 0.50 mmol), and trans-
b
-iodo-(4-phenyl)sty-
0.50 mmol) in DMSO (2.0 mL) to give crude product, which was
purified by column chromatography (10% EtOAc/hexane) to give
the product 3 k (192 mg, 93%) as a white solid; Rf (20% EtOAc/
hexane) 0.41; mp 154e156 ꢀC; IR: 2382, 1643, 1594, 1493,
rene (152 mg, 0.50 mmol) in DMSO (2.0 mL) to give crude product,
which was purified by column chromatography (5% EtOAc/hexane)
to give the product 3g (152 mg, 90%) as a white solid; Rf (15% EtOAc/
hexane) 0.46; mp: 150e152 ꢀC; IR (KBr): 2394, 1638, 1490, 1410,
1321 cmꢂ1; 1H NMR (200 MHz, CDCl3):
d 7.72e7.52 (7H, m, AreH),
1268 cmꢂ1
;
1H NMR (200 MHz, CDCl3):
d
8.01 (2H, d, J 8.0 Hz,
7.42 (2H, m, AreH, CH]), 7.35e7.26 (3H, m, AreH), 7.09 (1H, d, J
AreH), 7.68e7.57 (7H, m, AreH, CH]), 7.49e7.30 (5H, m, AreH),
14.0 Hz, ]CH), 3.94 (6H, s, 2ꢁOCH3), 3.88 (3H, s, OCH3); 13C NMR
7.10 (1H, d, J 14.0 Hz, ]CH), 2.43 (3H, m, CH3); 13C NMR (50 MHz,
(50 MHz, CDCl3):
d 164.2, 153.8, 142.7, 140.0, 138.3, 133.5, 129.1,
CDCl3):
d
164.5, 142.8, 142.5, 140.2, 138.4, 133.9, 129.9, 129.1, 128.0,
128.1, 128.0, 127.8, 127.1, 118.6, 110.0, 104.2, 61.6, 56.5; ESIMS: m/z

304
B. Das et al. / Tetrahedron 68 (2012) 300e305
415 [MH]þ; HRMS (ESI): [MH]þ, found 415.1669. C25H23N2O4 re-
quires 415.1657.
127.0, 125.5, 125.3, 116.2, 108.2, 107.6; ESIMS: m/z 349, 351 [MH]þ;
HRMS (ESI): [MH]þ, found 349.0742. C20H14N2O2Cl requires
349.0743.
4.3.12. (E)-2-(3,4-Dimethoxystyryl)-5-phenyl-1,3,4-oxadiazole
(3l). Following Section 4.2, CuI (9 mg, 0.05 mmol), DMEDA (4.5 mg,
0.05 mmol), LiO-t-Bu (80 mg, 1.0 mmol), 2-phenyl-1,3,4-oxadiazole
4.3.16. (E)-2-(2-(5-(4-Chlorophenyl)furan-2-yl)vinyl)-5-p-tolyl-
1,3,4-oxadiazole (3p). Following Section 4.2, CuI (9 mg,
0.05 mmol), DMEDA (4.5 mg, 0.05 mmol), LiO-t-Bu (80 mg,
1.0 mmol), 2-p-tolyl-1,3,4-oxadiazole (80 mg, 0.50 mmol), and (E)-
2-(4-chlorophenyl)-5-(2-iodovinyl)furan (165 mg, 0.50 mmol) in
DMSO (2.0 mL) to give crude product, which was purified by col-
umn chromatography (8% EtOAc/hexane) to give the product 3m
(161 mg, 88%) as a white solid; mp: 197e199 ꢀC; IR (KBr): 2385,
(73 mg, 0.50 mmol), and trans-b-iodo-(3,4-dimethoxy)styrene
(145 mg, 0.50 mmol) in DMSO (2.0 mL) to give crude product,
which was purified by column chromatography (9% EtOAc/hexane)
to give the product 3l (140 mg, 91%) as a white solid; Rf (20% EtOAc/
hexane) 0.52; mp: 102e104 ꢀC; IR (KBr): 2408, 1638, 1592, 1523,
1266 cmꢂ1 1H NMR (200 MHz, CDCl3):
; d 8.13 (2H, d, J 8.0 Hz,
AreH), 7.58e7.47 (4H, m, AreH, CH]), 7.19e7.12 (2H, m, AreH),
6.99 (1H, d, J 14.0 Hz, ]CH), 6.90 (1H, d, J 8.0 Hz, AreH), 3.97 (3H, s,
1619, 1488, 1463, 1259 cmꢂ1 1H NMR (200 MHz, CDCl3):
; d 7.98
(2H, d, J 2.0 Hz, AreH), 7.65 (2H, d, J 8.0 Hz, AreH), 7.41e7.23 (5H,
m, AreH, CH]), 7.02 (1H, d, J 14.0 Hz, ]CH), 6.71 (1H, d, J 2.0 Hz,
AreH), 6.65 (1H, d, J 2.0 Hz, AreH), 2.46 (3H, s, CH3); 13C NMR
OCH3), 3.95 (3H, s, eOCH3); 13C NMR (50 MHz, CDCl3):
d 164.1, 151.1,
149.8, 138.9, 132.0, 129.1, 127.8, 127.0, 124.2, 122.1, 111.2, 109.1, 107.9,
56.1, 56.0; ESIMS: m/z 309 [MH]þ; HRMS (ESI): [MH]þ, found
309.1238. C18H17N2O3 requires 309.1239.
(50 MHz, CDCl3):
d 164.2, 155.0, 150.9, 142.2, 134.1, 130.0, 129.1,
126.8, 125.9, 125.0, 121.2, 118.9, 116.2, 107.9, 107.3, 21.5; ESIMS: m/z
363, 365 [MH]þ; HRMS (ESI): [MH]þ, found 363.0882.
C21H16N2O2Cl requires 363.0900.
4.3.13. (E)-2-(3,4-Dimethoxystyryl)-5-(4-methoxyphenyl)-1,3,4-
oxadiazole (3m). Following Section 4.2, CuI (9 mg, 0.05 mmol),
DMEDA (4.5 mg, 0.05 mmol), LiO-t-Bu (80 mg, 1.0 mmol), 2-(4-
methoxyphenyl)-1,3,4-oxadiazole (88 mg, 0.50 mmol), and
4.3.17. (E)-2-(4-Chlorophenyl)-5-(2-(5-(4-chlorophenyl)furan-2-yl)
vinyl)-1,3,4-oxadiazole (3q). Following Section 4.2, CuI (9 mg,
0.05 mmol), DMEDA (4.5 mg, 0.05 mmol), LiO-t-Bu(80 mg,1.0 mmol),
2-(4-chlorophenyl)-1,3,4-oxadiazole (90 mg, 0.50 mmol), and (E)-2-
(4-chlorophenyl)-5-(2-iodovinyl)furan (165 mg, 0.50 mmol) in DMSO
(2.0 mL) to give crude product, which was purified by column chro-
matography (9% EtOAc/hexane) to give the product 3m (164 mg, 85%)
as a white solid; mp: 192e194 ꢀC; IR (KBr): 2380, 1605, 1475, 1407,
trans-b-iodo-(3,4-dimethoxy)styrene (145 mg, 0.50 mmol) in
DMSO (2.0 mL) to give crude product, which was purified by
column chromatography (9% EtOAc/hexane) to give the product
3m (152 mg, 90%) as a white solid; Rf (20% EtOAc/hexane) 0.49;
mp: 142e144 ꢀC; IR (KBr): 2401, 1608, 1496, 1457, 1249 cmꢂ1 1H
;
NMR (200 MHz, CDCl3):
d 8.01 (2H, d, J 8.0 Hz, AreH), 7.46 (1H, d,
J 14.0 Hz, CH]), 7.11e6.82 (6H, m, AreH, ]CH), 3.93 (3H, s,
1255 cmꢂ1; 1H NMR (200 MHz, CDCl3):
d 8.02 (2H, d, J 8.0 Hz, AreH),
OCH3), 3.90 (3H, s, OCH3), 3.86 (3H, s, OCH3); 13C NMR (50 MHz,
7.68 (2H, d, J8.0 Hz, AreH), 7.55e7.47 (2H, m, AreH), 7.44e7.30 (3H, m,
AreH, CH]), 7.04 (1H, d, J 14.0 Hz, ]CH), 6.73 (1H, d, J 2.0 Hz, AreH),
CDCl3):
d 164.1, 162.2, 150.9, 149.0, 138.0, 128.2, 127.9, 121.8, 116.5,
114.8, 111.1, 108.9, 107.8, 55.6, 55.5, 55.2; ESIMS: m/z 339 [MH]þ;
HRMS (ESI): [MH]þ, found 339.1335. C19H19N2O4 requires
339.1344.
6.69 (1H, d, J 2.0 Hz, AreH); 13C NMR (50 MHz, CDCl3):
d 164.8, 155.2,
150.3, 133.9, 129.8, 129.2, 128.2, 125.4, 125.2, 119.1, 116.2, 108.8, 107.2;
ESIMS: m/z 383, 385, 387 [MH]þ; HRMS (ESI): [MH]þ, found 383.0353.
C20H13N2O2Cl2 requires 383.0354.
4.3.14. (E)-2-(3,4-Dimethoxystyryl)-5-(4-(trifluoromethyl)phenyl)-
1,3,4-oxadiazole (3n). Following Section 4.2, CuI (9 mg, 0.05 mmol),
DMEDA (4.5 mg, 0.05 mmol), LiO-t-Bu (80 mg, 1.0 mmol), 2-(4-
(trifluoromethyl)phenyl)-1,3,4-oxadiazole (107 mg, 0.50 mmol),
Acknowledgements
The authors thank CSIR and UGC, New Delhi for financial
assistance.
and trans-b-iodo-(3,4-dimethoxy)styrene (145 mg, 0.50 mmol) in
DMSO (2.0 mL) to give crude product, which was purified by col-
umn chromatography (8% EtOAc/hexane) to give the product 3m
(165 mg, 88%) as a white solid; Rf (20% EtOAc/hexane) 0.53; mp:
Supplementary data
136e138 ꢀC; IR (KBr): 2238, 1633, 1591, 1572, 1325 cmꢂ1 1H NMR
;
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.tet.2011.10.049.
(200 MHz, CDCl3): d 8.22 (2H, d, J 8.0 Hz, AreH), 7.80 (2H, d, J 8.0 Hz,
AreH), 7.57 (1H, d, J 14.0 Hz, CH]), 7.14e7.05 (2H, m, AreH), 6.92
(1H, d, J 14.0 Hz, ]CH), 6.84 (1H, d, J 8.0 Hz, AreH), 3.95 (3H, s,
OCH3), 3.90 (3H, s, OCH3); 13C NMR (50 MHz, CDCl3):
d 162.8, 151.1,
References and notes
149.5, 139.9, 133.2, 133.0, 127.2, 127.1, 126.0, 125.9, 122.0, 111.1, 109.1,
107.0, 55.9, 55.8; ESIMS: m/z 377 [MH]þ; HRMS (ESI): [MH]þ, found
377.1123. C19H16N2O3F3 requires 377.1113.
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DMEDA (4.5 mg, 0.05 mmol), LiO-t-Bu (80 mg, 1.0 mmol), 2-
phenyl-1,3,4-oxadiazole (73 mg, 0.50 mmol), and (E)-2-(4-
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chromatography (8% EtOAc/hexane) to give the product 3m
(151 mg, 87%) as a white solid; Rf (20% EtOAc/hexane) 0.43; mp:
150e152 ꢀC; IR (KBr): 2376, 1624, 1550, 1460 cmꢂ1
;
1H NMR
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d
AreH, CH]), 7.02 (1H, d, J 14.0 Hz, ]CH), 6.72 (1H, d, J 2.0 Hz,
AreH), 6.68 (1H, d, J 2.0 Hz, AreH); 13C NMR (50 MHz, CDCl3):
d
163.8, 155.0, 150.8, 133.1, 132.1, 132.0, 129.5, 129.2, 127.8, 127.1,

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