Conversion of 2(3H)-furanones into 1,3,4-oxadiazoles

Article abstract of DOI:10.1002/hc.10197

A series of 2-phenyl-5-alkenyl-1,3,4-oxadiazoles were synthesized in high yields from the corresponding dicarbonylhydrazides through cyclodehydration.

Full text of DOI:10.1002/hc.10197

Heteroatom Chemistry
Volume 14, Number 6, 2003
Conversion of 2(3H)-Furanones
into 1,3,4-Oxadiazoles
Abdel-Sattar S. Hamad Elgazwy,1 Mayssoune Y. Zaki,2
Nahed N. Eid,2 and Ahmed I. Hashem1
1Department of Chemistry, Faculty of Science, Ain Shams University, Abbassia 11566, Cairo, Egypt
2Research Center for Drugs Control, Dokki, Giza, Egypt
Received 4 April 2003; revised 12 May 2003
RESULTS AND DISCUSSION
ABSTRACT: A series of 2-phenyl-5-alkenyl-1,3,4-
oxadiazoles were synthesized in high yields from
the corresponding dicarbonylhydrazides through cy-
In a previous study, we reported [11,12] the syn-
thesis of 5-aryl-3-arylmethylene-2-(3H)-furanones
1a–f via the condensation reactions of furan-2-
carboxaldehyde or 4-dimethylaminobenzaldehyde
with 3-aroylpropionic acids under Perkin condi-
tions, which yielded the corresponding E-lactones
as the only product and with no detectable amount
of the Z-isomers [7]. This result was consistent
with the results reported by Awad et al. [13] and
others [14,15] concerning the condensation reaction
of 5-methyl-furan-2-carboxaldehyde or 5-methyl
thiophene-2-carboxaldehyde with 3-aroylpropionic
acids under Perkin conditions. Scheme 1 shows the
conversion of 1a–f into (E)-2-aroylmethyl-3-aryl-
acrylohydrazides 2a–f, N1-(E)-2-aroylmethyl-3-aryl-
N2-benzo-acrylohydrazides 3a–f, 2-phenyl-5-[(E)-1-
aroylmethyl-2-(2-furyl)vinyl]-1,3,4-oxadiazoles 4a–c,
and 2-phenyl-5-[(E)-1-aroylmethyl-2-(4-dimethyla-
minophenyl)vinyl]-1,3,4-oxadiazoles 4d–f. Reac-
tion of 2a–c with benzoyl chloride in dry ben-
zene at refluxing temperature afforded 3a–c in
moderate (52–69%) yield, but the reaction of
2d–f with benzoyl chloride under the same re-
action conditions afforded 3d–f in low (31–42%)
yield.
ꢀ
C
clodehydration.
2003 Wiley Periodicals, Inc. Het-
eroatom Chem 14:570–574, 2003; Published online in
Wiley InterScience (www.interscience.wiley.com). DOI
10.1002/hc.10197
INTRODUCTION
2-Aryl-5-alkenyl-1,3,4-oxadiazoles have been re-
ported to show antibacterial [1,2], antifungal
[3], analgesic, antiinflammatory [4,5], and hypo-
glycemic [2] activity. The most popular synthesis
of 2,5-disubstituted-1,3,4-oxadiazoles is based on
the thermal or acid-catalyzed cyclization of 1,2-
diacylhydrazines [6]. Ring closure usually proceeds
in the presence of hot phosphorus, using phospho-
rus oxychloride [2,3,7–10], although an improved
method by triphenylphosphine/carbon tetrachlo-
ride/triethylamine reagent has also been reported
[1]. These results promoted us to convert 2(3H)-
furanones 1a–f into 1,3,4-oxadiazoles 4a–f. In this
paper we report selected results of our investigations.
Treatment of hydrazides 3a–f with phosphorus
oxychloride under reflux furnished 4a–f in 22–70%
yield. The structures of 3a–f and 4a–f were deter-
mined by spectroscopic methods and analyses. The
IR spectral data for compounds 4a–c are in agree-
ment with our previous data [10].
Correspondence to: Abdel-Sattar S. Hamad Elgazwy, Group de
Quimica Organometalica, Departamento de Quimica Inorganica,
Facultad de Quimica, Universidad de Murcia, Aptdo. 4021. E-
30071 Murcia, Spain; e-mail: abhamad@um.es.
Contract grant sponsor: Research Center of Drug Control in
Egypt.
c
ꢀ
2003 Wiley Periodicals, Inc.
570

Conversion of 2(3H)-Furanones into 1,3,4-Oxadiazoles 571
R
TABLE 1 Optical Properties of 1–4
R
R
λ
max
(nm)
Abso.
λ
max
(nm)
Abso.
1a
1b
1c
404.00
266.00
407.50
271.00
407.50
311.50
275.50
224.50
461.00
320.00
272.00
218.00
460.50
320.50
305.50
271.00
212.50
468.50
324.00
273.00
306.00
306.50
211.00
306.50
468.50
353.50
354.00
272.00
473.50
354.50
2.340
0.739
1.313
0.412
0.943
0.053
0.276
0.075
1.423
0.208
0.176
0.098
1.652
0.252
0.264
0.351
0.168
0.701
0.327
1.997
0.734
0.778
0.023
0.840
0.022
1.044
0.925
0.056
0.003
0.778
3a
415.00
341.50
270.00
227.50
417.50
334.00
268.00
417.50
340.50
270.50
455.00
321.50
271.00
232.00
743.00
455.00
324.50
273.50
460.50
273.50
221.50
269.50
471.00
276.00
466.00
287.50
269.50
214.00
270.00
219.50
0.448
0.383
0.363
0.081
0.244
0.239
0.671
0.210
0.181
0.504
0.921
0.066
0.362
−0.093
0.015
0.755
0.094
0.363
0.701
0.327
1.997
0.276
0.049
0.349
0.067
0.240
0.725
2.006
0.743
1.937
O
Ar
O
H
O
N
i
ii
O
N
H
Ph
Ar
NHNH2
Ar
O
O
O
3a-f
1a-f
2a-f
3b
3c
3d
a R = H,
b R = CH3
Ar = 2-furyl
Ar = 2-furyl
Ar = 2-furyl
R
N
N
,
c R = Cl
d R = H-,
,
O
Ph
iii
Ar = 4-dimethylaminophenyl
Ar = 4-dimethylaminophenyl
Ar = 4-dimethylaminophenyl
O
Ar
e R = CH3
f R = Cl-,
,
1d
1e
4a-f
SCHEME
1
Reagents and conditions: (i) NH2NH2·
H2O/ethanol, stirring at RT for 2 days: (ii) benzoyl chloride
in dry benzene heat/3 h: (iii) heating with POCl3 for 1 h.
3e
3f
The results obtained are valid for dichloromethane
as solvent and we did not find significant altered
trends in other solvents. With a view to understand
the coplanarity and rotational freedom of individ-
ual rings, nonstructured ꢀ–ꢀ∗ transition bands have
been studied. Compared to parent lactones 1a–c at
absorption maximum ꢁmax = 404 nm and 1d–f at
ꢁmax = 461 nm, as outlined in Table 1, the replace-
ment of 2-furyl by 4-dimethylaminophenyl rings, as
realized for 1a–c/1d–f, led to a bathochromic shift
at the absorption maximum ꢀꢁmax = +53–61 nm.
However, either acrylohydrazides 2a–c or 2d–f
caused an opposite hypsochromic shift at absorption
maximum ꢀꢁmax = −98 nm and ꢀꢁmax = −7 nm,
compared to parent lactones 1a–c and 1d–f respec-
tively. Hydrazides 3a–c caused a bathochromic shift
at the absorption maximum ꢀꢁmax = +10 nm ver-
sus parent lactones 1a–c, but the hydrazides 3d–f
gave unexpected data for the hypsochromic shift at
1f
2a
2b
4a
4b
2c
2d
4c
4d
2e
2f
4e
4f
Solvent dichloromethane, c = 5 × 10−6 mol/l for absorption measure-
ments, c = 1 × 10−6 mol/l for emission measurements.
Optical Characterization
The absorption spectra of 1a–f to 4a–f were mea-
sured in CH2Cl2 at a concentration of 5 × 10−6 mol/l.
TABLE 2 Melting Point, Yield, and Elemental Analysis for 1–4
Calcd/Found
m.p. (◦C)
Yield (%)
Formula
C
H
N
1e
1f
2d
2e
2f
3a
3b
3c
3d
3e
3f
4a
4b
4c
4d
4e
4f
186–188
204–206
158–160
134–135
126–128
167–168
170–171
253–254
234–236
247–249
266–268
83–86
44.2
52.7
77
86.7
79
69.4
52.6
57.1
31
42.3
57
58
22
77
26.6
14
C20H19NO2
78.66/78.9
6.27/6.10
4.95/5.40
6.54/6.68
6.87/6.20
5.63/5.90
4.84/4.80
5.18/5.70
4.19/4.20
5.98/6.5
4.58/5.00
4.29/4.90
12.99/13.00
12.45/12.46
11.74/11.70
7.84/7.78
7.21/7.30
6.85/6.71
9.82/9.78
9.51/9.33
9.09/9.00
7.86/7.58
7.56/7.28
7.16/7.12
10.26/10.10
9.92/9.80
9.46/9.40
C
19H16ClNO2
70.04/70.40
70.56/69.90
71.19/71.00
63.77/63.70
70.57/70.10
71.12/71.00
64.63/64.60
73.04/73.04
73.44/73.8
67.60/70.00
74.14/74.16
74.58/74.18
67.61/67.50
76.26/76.14
76.57/76.34
70.34/70.30
C
19H21N3O2
C19H21N3O2
C19H20ClN3O2
22H18N2O4
C23 20N2O4
C22H17ClN2O4
C
H
C
C
26H25N3O3
27H27N3O3
6.16/6.51
5.23/5.4
C
26H24ClN3O3
22H16N2O3
C23H18N2O3
C22H15ClN2O3
C
4.52/4.60
4.89/4.43
3.86/3.70
5.66/5.60
5.94/5.80
4.99/5.16
87–90
>360
>360
>360
C
26H23N3O2
C27H25N3O2
C26H22ClN3O2
>360
65

572 Elgazwy et al.
TABLE 3 Infrared (Nujol) (cm−1) and 1H NMR (Deuteriodimethyl Sulfoxide) Spectral Data for 1–4
υ
C=O, υC=N, υ
δ
1H
−NH
1e
1f
1783
2.21 (s, 3H, Ar CH3), 2.96 (s, 6H, NCH3), 6.59 (s, 1H, CH C ), 6.69 (d, 2H, J =
8.8 Hz, Ar H), 6.75 (s, 1H, CH C ), 7.15 (d, 2H, J = 9.05 Hz, Ar H), 7.62 (d,
2H, J = 8.8 Hz, Ar H), 7.70 (d, 2H, J = 8.3 Hz, Ar H)
1752
2.97 (s, 6H, NCH3), 6.61 (s, 1H, CH C ), 6.72 (d, 2H, J = 8.8 Hz, Ar H), 7.17 (d,
2H, J = 9.05 Hz, Ar H), 7.65 (d, 2H, J = 8.8 Hz, Ar H), 7.71 (d, 2H, J = 9.05 Hz,
Ar H), 6.77 (s, 1H, CH C )
2d
1648, 1687, 3100–3300
1652–1692, 3100–3300
1653–1697, 3110–3330
1667–1725, 3112–3263
2.84 (s, 6H, NCH3), 2.98 (d, 1H, J = 2.4 Hz, NHNH2a), 3.08 (d, 1H, J = 2 Hz,
NHNH2b), 4.24 (s, 2H, CH2), 6.47 (s, 1H, CH C ), 6.62 (d, 2H, J = 8.9 Hz,
Ar H), 7.07 (t, 1H, J = 2.3 Hz, CO-NHNH2), 7.17–7.29 (m, 5H, Ph-H), 7.24 (d, 2H,
J = 8.9 Hz, Ar H)
2e
2f
2.21 (s, 3H, Ar CH3), 2.96 (s, 6H, NCH3), 3.12 (d, 2H, J = 2.4 Hz, NHNH2b), 4.33
(s, 2H, CH2), 6.58 (s, 1H, CH C ), 6.69 (d, 2H, J = 8.7 Hz, Ar H), 7.15 (t, 1H,
J = 2.3 Hz, CO-NHNH2), 7.33 (d, 2H, J = 8.7 Hz, Ar H), 7.62 (d, 2H, J = 8.8 Hz,
Ar H), 7.70 (d, 2H, J = 8.3 Hz, Ar H)
2.92 (s, 6H, NCH3), 3.08 (d, 1H, J = 2.4 Hz, NHNH2a), 3.15 (d, 1H, J = 2.4 Hz,
NHNH2b), 4.34 (s, 2H, CH2), 6.63 (s, 1H, CH C ), 6.68 (d, 2H, J = 6.7 Hz,
Ar H), 7.15 (t, 1H, J = 2.3 Hz, CO-NHNH2), 7.33 (d, 2H, J = 6.7 Hz, Ar H),
7.35–7.41 (m, 4H, Cl Ar H)
3.85 (s, 2H, CH2CO ), 6.63 (dd, 1H, J = 1.8, 3.3 Hz, furan-H4), 7.04 (d, 1H, J = 3
Hz, furan-H3), 6.75 (s, 1H, furan-CH C ), 7.37–7.43 (m, 5H, Ph-H), 7.64 (d, 1H,
J = 1.8 Hz, furan-H5), 7.75 (m, 5H, Ar H), 9.30 (s, 1H, NH-NH ), 10.67 (s, 1H,
NH-NH )
3a
3b 1667–1699, 1726, 3099–3267 2.21 (s, 3H, Ar CH3), 3.88 (s, 2H, CH2CO), 6.70 (s, 1H, furan-CH C ), 6.87 (d, 2H,
J = 9 Hz, Ar H), 7.00 (d, 1H, J = 3.6 Hz, furan-H3), 7.14 (dd, 1H, J = 1.8, 3.6 Hz,
furan-H4), 7.45 (d, 2H, J = 9 Hz, Ar H), 7.69 (d, 2H, J = 7.5 Hz, Ar H), 7.96 (d,
J = 1.5 Hz, furan-H5), 8.34 (s, 1H, NH-NH ), 11.01 (s, 1H, NH-NH )
3c
1660–1726, 3225–3316
3.86 (s, 2H, CH2CO), 6.61 (s, 1H, furan-CH C ), 6.85 (d, 2H, J = 9 Hz, Ar H), 7.1
(d, 1H, J = 3.6 Hz, furan-H3), 7.2 (dd, 1H, J = 1.8, 3.6 Hz, furan-H4), 7.38 (d, 2H,
J = 8.1 Hz, Ar H), 7.42 (d, 2H, J = 9 Hz, Ar H), 7.73 (d, 2H, J = 7.5 Hz, Ar H),
7.85 (s, 1H, NH-NH ), 7.97 (d, 1H, J = 1.5 Hz, furan-H5), 8.57 (s, 1H, NH ),
10.72 (s, 1H, NH )
3d
3e
1665–1726, 3230–3318
1661–1729, 3232–3320
3.03 (s, 6H, NCH3), 3.86 (s, 2H, CH2CO ), 6.75 (s, 1H, CH C ), 6.80 (d, 2H,
J = 8.9 Hz, Ar H), 7.32–7.84 (m, 10H, Ph-H), 7.75–7.32 (d, 2H, J = 9 Hz, Ar H),
9.30 (s, 1H, NH-NH ), 11.16 (s, 1H, NH-NH )
2.21 (s, 3H, CH3), 2.98 (s, 6H, NCH3), 3.56 (s, 2H, CH2CO ), 6.59 (s, 1H,
CH C ), 6.72 (d, 2H, J = 8.8 Hz, Ar H), 7.15 (d, 2H, J = 9.05 Hz, Ar H),
7.39–7.53 (m, 5H, Ph-H), 7.64–7.62 (d, 2H, J = 8.8 Hz, Ar H), 7.77–7.75 (d, 2H,
J = 8.8 Hz, Ar H), 8.34 (s, 1H, NH-NH ), 11.04 (s, 1H, NH-NH )
2.98 (s, 6H, NCH3), 3.56 (s, 2H, CH2CO ), 6.81 (s, 1H, CH C ), 6.74 (d, 2H,
J = 8.8 Hz, Ar H), 7.15 (d, 2H, J = 9.05 Hz, Ar H), 7.52 (m, 5H, Ph-H), 7.65 (d,
2H, J = 8.8 Hz, Ar H), 7.78 (d, 2H, J = 8.8 Hz, Ar H), 8.4 (s, 1H, NH-NH ),
11.4 (s, 1H, NH-NH )
3f
1663–1727, 3224–3330
4a
4b
1689, 1590–1620, 3217
1690, 1590–1616, 3217
4.34 (s, 2H, CH2 ), 6.09 (s, 1H, furan-CH C ), 6.66 (dd, 1H, J = 1.8, 3.3 Hz,
furan-H4), 7.15 (d, 1H, J = 3.3 Hz, furan-H3), 7.07–7.64 (m, 10H, Ph-H), 7.95 (d, J
= 1.5 Hz, furan-H5)
2.34 (s, 3H, Ar CH3), 4.58 (s, 2H, CH2), 6.09 (s, 1H, CH C ), 7.07 (dd, 1H,
J = 1.8, 3.6 Hz, furan-H4), 7.20 (d, 1H, J = 3.3 Hz, furan-H3), 7.38 (d, 2H,
J = 8.7, Ar H), 7.45 (d, 2H, J = 8.4 Hz, Ar H), 7.48–7.85 (m, 5H, Ph-H), 8.20 (d,
1H, J = 1.5 Hz, furan-H5)
4c
1689, 1591–1619, 3219
4.44 (s, 2H, CH2), 6.71 (dd, 1H, J = 1.8, 3.3 Hz, furan-H4), 7.13 (s, 1H, CH C ),
7.18 (d, 1H, J = 3.3 Hz, furan-H3), 7.38 (d, 2H, J = 8.7 Hz, Ar H), 7.39–7.68 (m,
5H, Ph-H), 7.70 (d, 2H, J = 8.7 Hz, Ar H), 7.95 (d, 1H, J = 1.5 Hz, furan-H5)
2.98 (s, 6H, NCH3), 4.1 (s, 2H, CH2CO ), 6.75 (s, 1H, CH C ), 6.80 (d, 2H,
J = 8.9 Hz, Ar H), 7.32–7.84 (m, 10H, Ph-H), 7.75–7.32 (d, 2H, J = 9 Hz, Ar H)
2.21 (s, 3H, CH3), 2.98 (s, 6H, NCH3), 3.56 (s, 2H, CH2CO ), 6.59 (s, 1H, CH C ),
6.72 (d, 2H, J = 8.8 Hz, Ar H), 7.15 (d, 2H, J = 9.05 Hz, Ar H), 7.39–7.53 (m, 5H,
Ph-H), 7.64–7.62 (d, 2H, J = 8.8 Hz, Ar H), 7.77–7.75 (d, 2H, J = 8.8 Hz, Ar H)
2.99 (s, 6H, NCH3), 4.03 (s, 2H, CH2CO), 7.72 (s, 1H, CH C ), 6.82 (d, 2H,
J = 8.4 Hz, Ar H), 7.32 (d, 2H, J = 8.7 Hz, Ar H), 7.47 (d, 2H, J = 8.4 Hz, Ar H),
7.54–7.73 (m, 5H, Ph-H), 7.92 (d, 2H, J = 8.7 Hz, Ar H)
4d
4e
1692, 1592–1622, 3221
1695, 1595–1618, 3222
4f
1690, 1590–1624, 3230

Conversion of 2(3H)-Furanones into 1,3,4-Oxadiazoles 573
absorption maximum ꢀꢁmax = −6 nm compared to
the parent lactones 1d–f. The parent lactones 1a–f,
hydrazides 2a–f and/or 3a–f, in which one lactone
ring was replaced by hydrazides 2a–f or 3a–f and/or
1,3,5-oxadiazole 4a–f moiety, are compared; only the
introduction of a second 1,3,5-oxadiazole unit led to
a further significant hypsochromic shift of 4a–c at
absorption maximum ꢀꢁmax = −130 nm and of 4d–
f at ꢀꢁmax = −191 nm. These results are in agree-
ment with a theoretically calculated convergence of
the frontier orbitals.
(3E)-1,4-Diaryl-3(5-phenyl)-1,3,4-oxadiazol-2-
yl-but-3-en-1-ones 4a–f
A mixture of 3a–f (2 mmol) and phosphorus oxy-
chloride (10 ml) was refluxed for 1 h. The mix-
ture was cooled, poured onto crushed ice (20 ml),
and then neutralized with 1.0 N aqueous solu-
tion of sodium hydrogen carbonate. The yellow-
ish precipitate was collected by filtration, washed
with water, and recrystallized from acetonitrile to
give 4a–f. Analytical data are given in Tables 2
and 3.
EXPERIMENTAL
1H NMR spectra were recorded on a Varian Plus 300
(300 MHz) or Bruker XL 300 (300 MHz) instrument.
Infrared spectra were taken on a Perkin-Elmer
1600 FT-IR spectrometer. Mass points were recorded
on a Kratos Concept instrument. Melting points
were measured on an electrothermal digital melt-
CONCLUSION
We have demonstrated the benzoylation of (E)-
2-aroylmethyl-3-(2-aryl) acrylohydrazides 2a–f in
nonpolar solvent by benzoyl chloride and cyclo-
dehydration of N-(2E)-3-substituted-2-(2-oxo-subs-
titute-ethyl)prop-2-enoylbenzohydrazides 3a–f by
phosphorus oxychloride to give (3E)-1,4-disubs-
tituted-3(5-phenyl-1,3,4-oxadiazol-2-yl)but-3-ene-1-
ones 4a–f.
ing point apparatus and are uncorrected. The R
f
values reported for TLC analyses were determined
on Macherey–Nagel 0.25-mm layer fluorescent UV254
plates with the indicated solvent system. Elemen-
tal analyses were performed by M-H-W Laboratories
(Phoenix, AZ) at Murcia University, Spain, and Cairo
University.
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N-(2E)-3-Substituted-2-(2-oxosubstituted-
ethyl)prop-2-enoylbenzohydrazides 3a–f
To a suspension of 2a–f (2 mmol) in dry benzene (15
ml) at 25◦C, benzoyl chloride (2.1 mmol) was added
and the mixture was heated under reflux at 75◦C for
6 h. The solvent was evaporated in vacuo, and the
solid residue was recrystallized from ethanol to give
3a–f. Analytical data are given in Tables 2 and 3.

574 Elgazwy et al.
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