Facile synthesis of symmetric and unsymmetric 1,3,4-oxadiazoles using 2-acyl(or aroyl)pyridazin-3-ones

Article abstract of DOI:10.1055/s-2003-37647

Symmetric and unsymmetric 1,3,4-oxadiazoles were synthesized in situ from hydrazine hydrate and the corresponding 2-acyl-4,5-dichloropyridazin-3-ones as acylating agents in polyphosphoric acid or BF₃·OEt₂ in excellent yields.

Full text of DOI:10.1055/s-2003-37647

560
PAPER
Facile Synthesis of Symmetric and Unsymmetric 1,3,4-Oxadiazoles Using
2-Acyl(or aroyl)pyridazin-3-ones
S
ynthesis of Symm
o
etric and
U
n
n
symmetric
1
g
,3,4-Oxadiaz
-
ole
s
Dae Park, Jeum-Jong Kim, Hyun-A Chung, Deok-Heon Kweon, Su-Dong Cho, Sang-Gyeong Lee,
Yong-Jin Yoon*
Department of Chemistry and Research Institute of Natural Sciences, Gyeongsang National University, Chinju 660-701, Korea
Fax +82(55)7610244; E-mail: yjyoon@nongae.gsnu.ac.kr
Received 13 November 2002; revised 7 January 2003
aroyl)-4,5-dichloropyridazin-3-ones. Since they are also
Abstract: Symmetric and unsymmetric 1,3,4-oxadiazoles were
stable in air and not hygroscopic, we successfully synthe-
synthesized in situ from hydrazine hydrate and the corresponding 2-
sized both symmetrically and unsymmetrically 2,5-disub-
acyl-4,5-dichloropyridazin-3-ones as acylating agents in polyphos-
stituted 1,3,4-oxadiazoles by using 2-acyl(or aroyl)-4,5-
dichloropyridazin-3-ones 1 as acylating agents. We report
here on a facile one-pot procedure for the synthesis of ei-
ther unsymmetrically or symmetrically 2,5-disubstituted
1,3,4-oxadiazoles using 2-acyl(or aroyl)-4,5-dichloro-
pyridazin-3-ones (Scheme 1).
phoric acid or BF3 OEt2 in excellent yields.
Key words: 2-acyl-4,5-dichlorolpyridazin-3-ones, 1,3,4-oxadiaz-
oles , cyclodehydration
1,3,4-Oxadiazoles have attracted significant interest in
medicinal chemistry,1–7 pesticide chemistry,8 polymer sci-
ence,9 and material science.10 This has, in recent years, led
to the discovery of a variety of cyclodehydrating agents
including the solid phase methodology for the synthesis of
1,3,4-oxadiazoles.11 Because the biological6,8a,b or electro-
chemical properties9a,b,10c,d of unsymmetrically 2,5-disub-
stituted 1,3,4-oxadiazoles are different from symmetric
derivatives, the synthesis of unsymmetrically 2,5-disub-
stituted 1,3,4-oxadiazole has been of considerable inter-
est. The synthesis of symmetrically 2,5-disubstituted
1,3,4-oxadiazoles from diacylhydrazines prepared from
acid chloride and hydrazine can be performed by using
several cyclodehydrating agents such as thionyl chlor-
ide,12 polyphosphoric acid,11e,13 sulfuric acid,14 phospho-
rus oxychloride,8a,9a,b,10b,c,15 orthophosphoric acid/
Scheme 1 i) NH2NH2 H2O ii) BF3 OEt2, dioxane or polyphosphoric
acid
phosphorus
pentoxide/phosphorus
oxychloride,11e
1,1,1,3,3,3-hexamethyldisilazane,6 and BF3 OEt2.11d Al-
though these methods are useful for the synthesis of sym-
metrically 2,5-disubstituted 1,3,4-oxadiazoles, they are
not suitable for the one-pot synthesis of unsymmetrically
2,5-disubstituted 1,3,4-oxadiazoles since the diacylhydra-
zines as the precursors of 2,5-disubstituted 1,3,4-oxadiaz-
oles are mostly prepared from acid chlorides.8a,10a,b,11d,e
The drawback of the synthetic method for unsymmetrical-
ly 2,5-disubstituted 1,3,4-oxadiazoles using hydrazine
and acid chloride is that acid chlorides are overly reactive.
In fact, the reaction of acid chlorides with unprotected hy-
drazine always gave the corresponding diacylhydra-
zines.16 Therefore, a mild and stable acylating agent is
required for synthesizing unsymmetrically 2,5-disubsti-
tuted 1,3,4-oxadiazoles.
After the reaction of 1a–e with hydrazine hydrate, the re-
sulting mixture was treated with polyphosphoric acid or
boron trifluoride diethyl etherate in dioxane to give the
symmetrically 2,5-disubstituted 1,3,4-oxadiazoles 2 in
81–98% yields, except for 2-propyl-4,5-dichloropyri-
dazin-3-one (1h). However, 1,3,4-oxadiazoles 2f and 2g
were not formed from the corresponding diacylhydrazines
of 1f and 1g using BF3 OEt2 (Table 1).
2,5-Diethyl-1,3,4-oxadiazole (2h) could not be prepared
from 2-propanoyl-4,5-dichloropyridazin-3-one (1h) by
using either BF3 OEt2 or polyphosphoric acid as the cy-
clodehydrating agent. Polyphosphoric acid is more effec-
tive than boron trifluoride diethyl etherate as cyclo-
dehydrating agent in our systems.
We had reported in our previous paper17 on the excellent
ability of the acyl transfer to amines shown by 2-acyl(or
On the other hand, we attempted to synthesize in situ un-
symmetrically 2,5-disubstituted 1,3,4-oxadiazoles using
two different 2-acyl(or aroyl)-4,5-dichloropyridazin-3-
ones and polyphosphoric acid as cyclodehydrating agent.
A typical reaction procedure in situ involves the addition
of a 2-acyl(or aroyl)-4,5-dichloropyridazin-3-one to a so-
Synthesis 2003, No. 4, Print: 18 03 2003.
Art Id.1437-210X,E;2003,0,04,0560,0564,ftx,en;F09202SS.pdf.
© Georg Thieme Verlag Stuttgart · New York
ISSN 0039-7881

PAPER
Synthesis of Symmetric and Unsymmetric 1,3,4-Oxadiazoles
561
Table 1 Synthesis of Symmetrically 2,5-Disubstituted 1,3,4-Oxadi-
Table 2 Synthesis of Unsymmetrically 2,5-Disubstituted 1,3,4-Ox-
azoles
adizoles in Polyphosphoric Acid
Entry
1
Dehydrating
Agenta
Time (h) Product Yieldb
(%)
Entry
Compound 1
Time (h) Product Yielda (%)
1
2
3
4
5
6
7
8
1a
1a
1a
1a
1a
1d,f
1f
1h
2
3a
3b
3c
3d
3e
3f
74
90
95
81
87
84
79
74
1
2
3
4
5
6
7
8
1a
1b
1c
1d
1e
1f
PPA
BF3 OEt2
4
5.5
2a
2a
96
95
1b
1c
1d
1g
1g
1g
1h
2
2
PPA
BF3 OEt2
2.5
6.5
2b
2b
92
92
3.5
2
PPA
BF3 OEt2
3
11
2c
2c
98
88
2.5
2.5
1.5
PPA
BF3 OEt2
3
9
2d
2d
87
81
3g
3h
PPA
BF3 OEt2
3.5
12
2e
2e
94
86
1g
a Isolated yield. 4,5-Dichloropyridazin-3-one was recovered quantita-
tively.
PPA
BF3 OEt2
3.5
2f
2f
85
-
–
1g
1h
PPA
BF3 OEt2
3
2g
2g
91
-
–
spots were located by UV light. Column chromatography was car-
ried out on silica gel 60 (70–230 mesh). Melting points were deter-
mined with a Thomas–Hoover capillary apparatus and are
uncorrected. 1H and 13C NMR spectra were obtained on a Bruker FT
NMR-DRX 500 or a Varian Inova 500 spectrometer and with chem-
ical shift values reported in δ units (part per million) relative to an
internal standard (teteramethylsilane). IR spectra were obtained on
a Hitachi 270-50 or Mattson Genesis Series FT-IR spectrophotom-
eter. Elemental analyses were performed with a Perkin Elmer 240C.
Mass spectra were recorded using JEOL JMS-700 spectrometer.
–
–
PPA
BF3 OEt2
2h
2h
-
-
a PPA = polyphosphoric acid.
b Isolated yield. 4,5-Dichloropyridazin-3-one was recovered quantita-
tively.
lution of hydrazine hydrate in THF, stirring for 10 minutes
at room temperature and then adding another 2-acyl(or
aroyl)-4,5-dichloropyridazin-3-one to furnish the corre-
sponding unsymmetric N-acyl(or aroyl)-N′-aroylhydra-
zine. After evaporating the solvent under reduced
pressure, polyphosphoric acid was added to the residue,
and the reaction mixture was refluxed for 1.5–3.5 hours.
The yields of unsymmetric 2-alkyl(or aryl)-5-aryl-1,3,4-
oxadiazoles 3 were good to excellent. 4,5-Dichloropyri-
dazin-3-one was also isolated in quantitative yields in all
cases (Table 1 and 2).
Symmetrically 2,5-Disubstituted 1,3,4-Oxadiazoles 2; General
Procedures
Method A: To a solution of 117 (2.0 mmol) in anhyd THF (30 mL)
was added 80% hydrazine hydrate (1.0 mmol). The mixture was re-
fluxed until compound 1 had disappeared. After evaporating the
mixture under reduced pressure, polyphosphoric acid (30 mL) was
then added and the mixture was stirred for 2–4 h at 130 °C. After
cooling to r.t., H2O (100 mL) was slowly added. The pH of the so-
lution was adjusted to about 6 using sat. aq solution of NaHCO3.
The product was extracted with EtOAc (2 × 50 mL) and the com-
bined organic layers were dried (MgSO4) and filtered. Silica gel (1
g) was added to the filtrate and the solvent was evaporated under re-
duced pressure. The resulting gel was applied to the top of an open-
bed silica gel column (3 × 10 cm). The column was eluted with
CH2Cl2–THF (9.5:0.5) and fractions containing the product were
combined and evaporated under reduced pressure to give 2.
Unsymmetric 2,5-dialkyl-1,3,4-oxadiazoles, however,
could not be prepared from the different 2-acyl-4,5-
dichloropyridazin-3-one under our conditions.
In conclusion, our method for the synthesis of either sym-
metrically or unsymmetrically 2,5-disubstituted 1,3,4-ox-
adiazoles has several advantages: (1) the precursors such
as diaroylhydrazines or N-acyl-N′-aroylhydrazines need
not be isolated before cyclodehydration; (2) 2-acyl(or
aroyl)-4,5-dichloropyridazin-3-ones are mild and stable
sources of acyl (or aroyl) group for the synthesis of un-
symmetrically N,N′-disubstituted hydrazines; (3) cyclo-
dehydration can be accomplished in situ; and (4) reusable
4,5-dichloropyridazin-3-one can be recovered quantita-
tively.
Method B: To a solution of 117 (2.0 mmol) in anhyd dioxane (30
mL) was added 80% hydrazine hydrate (1.0 mmol). The mixture
was refluxed until compound 1 had disappeared, and BF3 OEt2 (3.6
mmol) in anhyd dioxane (5 mL) was then added and the mixture
was refluxed for 3–11 h. After evaporating the mixture under re-
duced pressure, H2O (100 mL) was slowly added. The pH of the so-
lution was adjusted to about 6 using sat. aq solution of NaHCO3.
The product was extracted with EtOAc (2 × 50 mL) and the com-
bined organic layers were dried (MgSO4) and filtered. Silica gel (1
g) was added to the filtrate and the solvent was evaporated under re-
duced pressure. The resulting gel was applied to the top of an open-
bed silica gel column (3 × 10 cm) and the column was eluted with
CH2Cl2–THF (9.5:0.5). Fractions containing the product were com-
bined and evaporated under reduced pressure to give 2.
Reagents and solvents were used as received from commercial
sources. TLC was performed on silica gel 60 F254 (Merck). The
Synthesis 2003, No. 4, 560–564 ISSN 0039-7881 © Thieme Stuttgart · New York

562
Y.-D. Park et al.
PAPER
2,5-Diphenyl-1,3,4-oxadiazole (2a)
HRMS (EI, 80 eV): m/z calcd for C26H18N2O: 374.1419; found:
374.1423.
Mp 132–133 °C (Lit.11b mp 137–139 °C; Lit.11e mp 138 °C).
IR (KBr): 3050, 2950, 1620, 1560, 1500, 1440, 1260, 1080, 1020,
710, 690 cm–1.
Anal. Calcd for C26H18N2O: C, 83.40; H, 4.85; N, 7.48. Found: C,
83.49; H, 4.92; N, 7.53.
1H NMR (CDCl3): δ = 7.52–7.58 (m, 6 H), 8.14–8.16 (m, 4 H).
13C NMR (CDCl3): δ = 123.9, 126.9, 129.0, 131.7, 164.6.
2,5-Bis(4-methoxyphenyl)-1,3,4-oxadiazole (2f)
Mp 155–157 °C.
HRMS (EI, 80 eV): m/z calcd for C14H10N2O: 222.0793; found:
222.0792.
IR (KBr): 3000, 1650, 1500, 1450, 1430, 1320, 1280, 1180, 1040,
850 cm–1.
1H NMR (CDCl3): δ = 3.88 (s, 6 H), 7.01–7.03 (m, 4 H), 8.04–8.06
(m, 4 H).
Anal. Calcd for C14H10N2O: C, 75.66; H, 4.54; N, 12.60. Found: C,
75.78; H, 4.65; N, 12.71.
13C NMR (CDCl3): δ = 55.5, 114.5, 116.5, 128.6, 162.2, 164.1.
2,5-Bis(4-methylphenyl)-1,3,4-oxadiazole (2b)
Mp 171–173 °C (Lit.11e mp 175 °C).
HRMS (EI, 80 eV): m/z calcd for C16H14N2O3: 282.1004; found:
282.1007.
IR (KBr): 3050, 3000, 2950, 1610, 1500, 1440, 1300, 1260, 1180,
1080, 1020, 820, 740 cm–1.
1H NMR (CDCl3): δ = 2.40 (s, 6 H), 7.32 (d, 4 H, J = 6.5 Hz), 8.01
(d, 4 H, J = 6.5 Hz).
Anal. Calcd for C16H14N2O3: C, 68.07; H, 5.00; N, 9.92. Found: C,
68.12; H, 5.21; N, 10.03.
2,5-Bis(2-furyl)-1,3,4-oxadiazole (2g)
Mp 136–138 °C.
13C NMR (CDCl3): δ = 21.1, 121.2, 126.7, 129.6, 142.0, 164.4.
HRMS (EI, 80 eV): m/z calcd for C16H14N2O; 250.1106; found:
250.1103.
IR (KBr): 3100, 1640, 1520, 1460, 1400, 1240, 1160, 1100, 1020,
900 cm–1.
1H NMR (CDCl3): δ = 6.62–6.63 (m, 2 H), 7.24 (d, 2 H, J = 5.0 Hz),
7.67 (d, 2 H, J = 3.0 Hz).
Anal. Calcd for C16H14N2O: C, 76.78; H, 5.64; N, 11.19. Found: C,
76.80; H, 5.71; N, 11.30.
13C NMR (CDCl3): δ = 112.3, 114.4, 139.2, 145.9, 156.8.
2,5-Bis(4-chlorophenyl)-1,3,4-oxadiazole (2c)
Mp 220–222 °C (Lit.11e mp 242 °C).
HRMS (EI, 80 eV): m/z calcd for C10H6N2O3: 202.0378; found:
202.0377.
IR (KBr): 3100, 2900, 1620, 1560, 1500, 1400, 1100, 1000, 840,
740 cm–1.
1H NMR (CDCl3): δ = 7.45 (d, 4 H, J = 8.6 Hz), 8.00 (d, 4 H, J = 8.6
Anal. Calcd for C10H6N2O3: C, 59.41; H, 2.99; N, 13.86. Found: C,
59.52; H, 3.02; N, 13.92.
Hz).
Unsymmetrically 2,5-Disubstituted 1,3,4-Oxadiazoles 3; Gener-
al Procedure
13C NMR (CDCl3): δ = 122.0, 128.1, 129.4, 138.0, 167.8.
To a solution of 117 (Table 2) (1.11 mmol) in anhyd THF (30 mL)
was added 80% hydrazine hydrate (1.0 mmol). The mixture was
stirred for 10 min, and a different (Table 2) acylpyridazin-3-one 1
(Table 2) (1.11 mol) was then added. After stirring the mixture for
10 min, the solvent was evaporated under reduced pressure, and
then polyphosphoric acid (30 mL) was added. The solution was
stirred for 1.5–3.5 h at 130 °C, cooled to r.t., and H2O (100 mL) was
slowly added. The pH of the solution was adjusted to about 6 by
addition of sat. aq solution of NaHCO3. The product was extracted
with EtOAc (2 × 50 mL), and the combined organic layers were
dried (MgSO4) and filtered. Silica gel (1 g) was added to the filtrate
and the mixture was evaporated under reduced pressure. The result-
ing gel was applied to the top of an open-bed silica gel column
(3 × 10 cm). The column was eluted with CH2Cl2–THF (9.5:0.5)
and fractions containing the product were combined and evaporated
under reduced pressure to give 3.
HRMS (EI, 80 eV): m/z calcd for C14H8Cl2N2O: 290.0014; found:
290.0012.
Anal. Calcd for C14H8Cl2N2O: C, 57.76; H, 2.77; N, 9.62. Found: C,
57.81; H, 2.82; N, 9.71.
2,5-Bis(2,4-dichlorophenyl)-1,3,4-oxadiazole (2d)
Mp 194–195 °C (Lit.11e mp 161.5 °C).
IR (KBr): 3100, 3000, 1620, 1490, 1400, 1100, 1060, 860, 700
cm–1.
1H NMR (CDCl3): δ = 7.29 (dd, 2 H, J = 2.0, 8.5 Hz), 7.44 (d, 2 H,
J = 2.0 Hz), 7.89 (d, 2 H, J = 8.5 Hz).
13C NMR (CDCl3): δ = 120.9, 127.4, 130.8, 131.6, 133.5, 138.0,
162.3.
HRMS (EI, 80 eV): m/z calcd for C14H6N2OCl4: 357.9234; found:
357.9223.
2-Ethyl-5-phenyl-1,3,4-oxadiazole (3a)
Oil.
Anal. Calcd for C14H6Cl4N2O: C, 46.71; H, 1.68; N, 7.78. Found: C,
46.80; H, 1.71; N, 7.82.
IR (KBr): 3050, 3000, 2950, 1620, 1580, 1560, 1500, 1460, 1200,
1100, 1060, 1000, 780, 720, 700 cm–1.
2,5-Bis(4-biphenylyl)-1,3,4-oxadiazole (2e)
1H NMR (CDCl3): δ = 1.45 (t, 3 H, J = 6.0 Hz), 2.96 (q, 2 H, J = 6.0
Mp 234–236 °C.
Hz), 7.48–7.52 (m, 3 H), 8.03–8.05 (m, 2 H).
13C NMR (CDCl3): δ = 10.9, 19.2, 124.2, 126.8, 129.0, 131.5,
164.7, 167.8.
IR (KBr): 3100, 1620, 1580, 1480, 1460, 1420, 1080, 1000, 840
cm–1.
1H NMR (CDCl3): δ = 7.23–7.33 (m, 6 H), 7.49 (d, 4 H, J = 7.4 Hz),
7.60 (d, 4 H, J = 8.2 Hz), 8.04 (d, 4 H, J = 8.2 Hz).
HRMS (EI, 80 eV): m/z calcd for C10H10N2O: 174.0793; found:
174.0795.
13C NMR (CDCl3): δ = 122.2, 126.8, 127.0, 127.3, 127.9, 128.7,
139.3, 144.1, 164.1.
Anal. Calcd for C10H10N2O: C, 68.95; H, 5.79; N, 16.08. Found: C,
68.99; H, 5.87; N, 16.21.
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Synthesis of Symmetric and Unsymmetric 1,3,4-Oxadiazoles
563
2-(4-Methylpheny)-5-phenyl-1,3,4-oxadiazole (3b)
Mp 132–135 °C.
1H NMR (CDCl3): δ = 6.64 (dd, 1 H, J = 2.0, 3.5 Hz), 7.26–7.27 (m,
1 H), 7.42 (dd, 1 H, J = 2.0, 6.5 Hz), 7.60 (d, 1 H, J = 2.0Hz), 7.68–
7.69 (m, 1 H), 8.03 (d, 1 H, J = 8.5 Hz).
IR (KBr): 3100, 2950, 1630, 1600, 1560, 1500, 1460, 1420, 1320,
1280, 1200, 1100, 1030, 840, 740, 700 cm–1.
13C NMR (CDCl3): δ = 112.3, 114.7, 121.5, 127.7, 131.3, 132.0,
134.0, 138.3, 139.3, 146.1, 158.0, 161.7.
1H NMR (CDCl3): δ = 2.44 (s, 3 H), 7.32–7.34 (m, 2 H), 7.52–7.54
(m, 3 H), 8.00–8.03 (m, 2 H), 8.11–8.14 (m, 2 H).
HRMS (EI, 80 eV): m/z calcd for C12H6Cl2N2O2: 279.9806; found:
279.9801.
13C NMR (CDCl3): δ = 21.7, 121.2, 124.1, 126.9, 127.0, 129.1,
131.6, 142.3, 164.4, 164.8.
Anal. Calcd for C12H6Cl2N2O2: C, 51.27; H, 2.15; N, 9.97. Found:
C, 51.35; H, 2.40; N, 10.13.
HRMS (EI, 80 eV): m/z calcd for C15H12N2O: 236.0950; found:
236.0957.
2-(2-Furyl)-5-(4-methoxyphenyl)-1,3,4-oxadiazole (3g)
Mp 127–129 °C.
Anal. Calcd for C15H12N2O: C, 76.25; H, 5.12; N, 11.86. Found: C,
76.31; H, 5.19; N, 11.93.
IR (KBr): 3150, 2950, 1650, 1650, 1630, 1510, 1460, 1320, 1280,
1200, 1100, 900 cm–1.
1H NMR (CDCl3): δ = 3.88 (s, 3 H), 6.61–6.62 (m, 1 H), 7.01–7.03
(m, 2 H), 7.20 (d, 1 H, J = 5.0 Hz), 7.65 (d, 1 H, J = 5.0 Hz), 8.04–
8.06 (m, 2 H).
13C NMR (CDCl3): δ = 55.5, 112.1, 113.7, 114.6, 116.1, 128.8,
139.7, 145.5, 157.1, 162.5, 164.0.
2-(4-Chlorophenyl)-5-phenyl-1,3,4-oxadiazole (3c)
Mp 157–159 °C.
IR (KBr): 3100, 1620, 1560, 1500, 1420, 1320, 1280, 1100, 1080,
1020, 980, 840 cm–1.
1H NMR (CDCl3): δ = 7.50–7.57 (m, 5 H), 8.06–8.09 (m, 2 H),
8.12–8.14 (m, 2 H).
HRMS (EI, 80 eV): m/z calcd for C13H10N2O3: 242.0691; found:
242.0692.
13C NMR (CDCl3): δ = 122.5, 123.8, 127.0, 128.3, 129.2, 129.6,
131.9, 138.1, 163.8, 164.8.
Anal. Calcd for C13H10N2O3: C, 64.46; H, 4.16; N, 11.56. Found: C,
64.53; H, 4.24; N, 11.77.
HRMS (EI, 80 eV): m/z calcd for C14H9ClN2O: 256.0403; found:
256.0402.
Anal. Calcd for C14H9ClN2O: C, 65.51; H,3.53; N,10.91. Found: C,
65.70; H, 3.62; N, 11.12.
2-Ethyl-5-(2-furyl)-1,3,4-oxadiazole (3h)
Mp 48–49 °C.
IR (KBr): 3300, 2900, 1640, 1580, 1520, 1460, 1400, 1100, 1020,
900, 800 cm–1.
1H NMR (CDCl3): δ = 1.43 (t, 3 H, J = 7.5 Hz), 2.94 (q, 2 H, J = 7.5
Hz), 6.58 (dd, 1 H, J = 2.0, 1.5 Hz), 7.12–7.13 (m, 1 H), 7.62–7.63
(m, 1 H).
13C NMR (CDCl3): δ = 10.8, 19.1, 112.1, 113.6, 139.7, 145.5,
157.7, 167.2.
2-(2,4-Dichlorophenyl)-5-phenyl-1,3,4-oxadiazole (3d)
Mp 116–118 °C.
IR (KBr): 3010, 1600, 1560, 1470, 1420, 1300, 1120, 1100, 1000
cm–1.
1H NMR (CDCl3): δ = 7.44 (dd, 1 H, J = 2.6, 5.2 Hz), 7.54–7.59 (m,
3 H), 7.61 (d, 1 H, J = 2.6 Hz), 8.09 (d, 1 H, J = 8.5 Hz), 8.15–8.17
(m, 2 H).
HRMS (EI, 80 eV): m/z calcd for C8H8N2O2: 164.0586; found:
164.0586.
13C NMR (CDCl3): δ = 121.8, 123.7, 127.1, 127.7, 129.2, 131.2,
131.9, 132.0, 133.8, 138.1, 162.4, 165.2.
Anal. Calcd for C8H8N2O2: C, 58.53; H, 4.91; N, 17.06. Found: C,
58.64; H, 5.03; N, 17.16.
HRMS (EI, 80 eV): m/z calcd for C14H8Cl2N2O: 290.0014; found:
290.0013.
Anal. Calcd for C14H8Cl2N2O: C, 57.76; H, 2.77; N, 9.62. Found: C,
57.83; H, 2.86; N, 9.82.
Acknowledgments
This work was supported by grant No. 2000-1-12300-003-2 from
the Basic Research Program of the Korea Science & Engineering
Foundation.
2-(2-Furyl)-5-phenyl-1,3,4-oxadiazole (3e)
Mp 84–85 °C.
IR (KBr): 3150, 3100, 1640, 1560, 1540, 1500, 1460, 1300, 1180,
1120, 1100, 1080, 1040, 900 cm–1.
1H NMR (CDCl3): δ = 6.62–6.63 (m, 1 H), 7.24 (d, 1 H, J = 3.5 Hz),
References
7.53–7.55 (m, 3 H), 7.66–7.68 (m, 1 H), 8.12–8.14 (m, 2 H).
13C NMR (CDCl3): δ = 112.2, 114.1, 123.6, 127.0, 129.1, 131.9,
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HRMS (EI, 80 eV): m/z calcd for C12H8N2O2: 212.0586; found:
212.0581.
Anal. Calcd for C12H8N2O2: C, 67.92; H, 3.80; N, 13.20. Found: C,
67.98; H, 3.91; N, 13.30.
2-(2,4-Dichlorophenyl)-5-(2-furyl)-1,3,4-oxadiazole (3f)
Mp 143–144 °C.
(5) Ladduwahetty, T.; Baker, R.; Cascieri, M. A.; Chambers, M.
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IR (KBr): 3150, 3100, 3070, 1640, 1600, 1560, 1520, 1460, 1420,
1400, 1100, 1000, 960, 900, 800, 760 cm–1.
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Synthesis 2003, No. 4, 560–564 ISSN 0039-7881 © Thieme Stuttgart · New York