Synthesis of the e and Z isomers of 3-(5-aryl-1,3,4-oxadiazol-2-yl)acrylic acids

Article abstract of DOI:10.1134/S1070428015070155

Two procedures have been proposed for the synthesis of pure (E)- and (Z)-3-(5-aryl-1,3,4-oxadiazol-2-yl)acrylic acids, by one-step cyclization of (Z)-4-(2-aroylhydrazinyl)-4-oxobut-2-enoic acids or via initial cyclization of (Z)-4-(2-aroylhydrazinyl)-4-oxobut-2-enoic acids to 5-(aroylhydrazinylidene)furan-2(5H)-ones which are then converted into the target compounds.

Full text of DOI:10.1134/S1070428015070155

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2015, Vol. 51, No. 7, pp. 982–987. © Pleiades Publishing, Ltd., 2015.
Original Russian Text © S.S. Rozhkov, K.L. Ovchinnikov, G.G. Krasovskaya, A.S. Danilova, A.V. Kolobov, 2015, published in Zhurnal Organicheskoi
Khimii, 2015, Vol. 51, No. 7, pp. 1000–1005.
Synthesis of the E and Z Isomers
of 3-(5-Aryl-1,3,4-oxadiazol-2-yl)acrylic Acids
S. S. Rozhkov, K. L. Ovchinnikov, G. G. Krasovskaya, A. S. Danilova, and A. V. Kolobov
Yaroslavl State Technical University, Moskovskii pr. 88, Yaroslavl, 150023 Russia
e-mail: serg_rozhkov@mail.ru
Received January 5, 2015
Abstract—Two procedures have been proposed for the synthesis of pure (E)- and (Z)-3-(5-aryl-1,3,4-oxadi-
azol-2-yl)acrylic acids, by one-step cyclization of (Z)-4-(2-aroylhydrazinyl)-4-oxobut-2-enoic acids or via
initial cyclization of (Z)-4-(2-aroylhydrazinyl)-4-oxobut-2-enoic acids to 5-(aroylhydrazinylidene)furan-2(5H)-
ones which are then converted into the target compounds.
DOI: 10.1134/S1070428015070155
Many 1,3,4-oxadiazole derivatives possessing
a conjugated bond system exhibit luminescence and
semiconducting properties and are used as optical
bleaching agents, fluorescent dyes [1], and components
of active media for liquid lasers [2]. Organic light-
emitting diodes [3–6] and electrically conducting ma-
terials [7] have been obtained on the basis of thin films
prepared from polymers containing 1,3,4-oxadiazole
fragments.
(Scheme 1). It should be noted that attempts of the
same authors [8] to react 5-aryltetrazoles with maleic
anhydride with the goal of obtaining (Z)-3-(5-aryl-
1,3,4-oxadiazol-2-yl)acrylic acids were unsuccessful.
The second approach implies cyclization of 1,2-di-
acylhydrazines, which can be accomplished in one or
two steps. Only a few examples of such syntheses have
been reported. In particular, one-step cyclization of
(
Z)-4-(2-isobutyrylhydrazinyl)-4-oxobut-2-enoic acid
The present work was aimed at finding out whether
the cyclization of (Z)-4-(2-aroylhydrazinyl)-4-oxobut-
-enoic acids can be used for the preparation of iso-
merically pure (E)- and (Z)-3-(5-aryl-1,3,4-oxadiazol-
-yl)acrylic acids. Two synthetic approaches to
-(5-aryl-1,3,4-oxadiazol-2-yl)acrylic acids are known.
(3) gave (Z)-3-(5-isopropyl-1,3,4-oxadiazol-2-yl)-
acrylic acid (4) (Scheme 2) [9]. The two-step version
includes cyclization of 1,2-diacylhydrazines to 5-(acyl-
hydrazinylidene)furan-2(5H)-ones (isomaleimides) or
maleimides and their subsequent recyclization to
3-(1,3,4-oxadiazol-2-yl)acrylic acids. (E)-3-(5-Methyl-
1,3,4-oxadiazol-2-yl)acrylic acid [10] and
(E)-3-[5-(4-ethoxycarbonylphenyl)-1,3,4-oxadiazol-
2-yl]acrylic acid [11] were obtained in this way. The
latter approach has been poorly explored. We tried to
synthesize 3-(5-aryl-1,3,4-oxadiazol-2-yl)acrylic acids
2
2
3
The first of these is based on the reaction of substituted
-aryltetrazoles with fumaryl chloride [8], which
affords methyl 3-(5-aryl-1,3,4-oxadiazol-2-yl)acrylates
, and hydrolysis of the latter yields the corresponding
)-3-(5-aryl-1,3,4-oxadiazol-2-yl)acrylic acids
5
1
(
E
2
Scheme 1.
O
(1) MeOPh, collidine, 95°C
(2) MeOH, 23°C
O
N
N
N
O
Cl
NH
+
R
Cl
OMe
R
N
N
O
1
(
(
1) i-PrOH, NaOH, H O, 90°C
2) HCl
2
O
O
R
OH
N
N
2
R = 4-MeOC
6
4
H , 2,5-Me
2
C
6
H .
3
9
82

SYNTHESIS OF THE E AND Z ISOMERS OF 3-(5-ARYL-1,3,4-OXADIAZOL-2-YL)...
983
Scheme 2.
OH
H
i-Pr
O
O
N
P
2
O
5
, H
2
SO
, 20°C
4
O
N
OH
–
H O
2
O
H
O
N
i-Pr
N
3
4
by cyclization of the corresponding 1,2-diacylhydra-
zines, (Z)-4-(2-aroylhydrazinyl)-4-oxobut-2-enoic
acids 5.
Thus, the one-step cyclization of (Z)-4-(2-aroylhy-
drazinyl)-4-oxobut-2-enoic acids by the action of
phosphoryl chloride turned out to be inefficient for the
synthesis of chloro- and nitro-substituted (E)- and
Initial acids 5 were prepared in 92–97% yield by
acylation of substituted benzoic acid hydrazides with
maleic anhydride in glacial acetic acid at room tem-
perature (Scheme 3). Compounds 5 can also be syn-
thesized in high yield using ethyl acetate or diethyl
ether as solvent [12]. (Z)-4-(2-Aroylhydrazinyl)-4-oxo-
but-2-enoic acids 5 were subjected to cyclization by
the action of phosphoryl chloride in DMF. The com-
plete conversion of 5 was attained in 20–60 min at
room temperature. In all cases, the products were mix-
tures of E (6) and Z isomers (7) of 3-(5-aryl-1,3,4-oxa-
diazol-2-yl)acrylic acids, the E isomer prevailing. We
succeeded by separating isomers 6 and 7 due to their
different solubilities in water.
(
Z)-3-(5-aryl-1,3,4-oxadiazol-2-yl)acrylic acids.
The structure of isomeric acids 6 and 7 was con-
1
firmed by H NMR. (E)-3-(5-Aryl-1,3,4-oxadiazol-2-
yl)acrylic acids 6 are characterized by a larger differ-
ence in the chemical shifts of protons on the C=C
double bond and a larger spin–spin coupling constant
(Jtrans = 16 Hz against Jcis = 12 Hz for Z isomers 7),
which is consistent with published data [13]. Further-
1
more, the H NOESY spectrum of (Z)-3-(5-phenyl-
1,3,4-oxadiazol-2-yl)acrylic acid (7a) displayed strong
cross peaks between the HC=CH protons. The corre-
sponding cross peaks in the NOESY spectrum of
E isomer 6a were less intense due to the larger distance
between those protons.
The isomer ratio 6/7 strongly depended on the reac-
tion time. As expected, longer reaction time favored
formation of the E isomer. Our attempts to increase the
yield of isomers 7a–7c by shortening the reaction time
to several minutes were unsuccessful; they resulted in
incomplete conversion of the substrates.
Assuming that the rate of Z–E isomerization of
3
-(5-aryl-1,3,4-oxadiazol-2-yl)acrylic acids should
decrease on lowering the temperature, we carried out
the cyclization of acids 5 at lower temperature with
a view to increasing the yield of the Z isomers. How-
ever, the reaction of (Z)-4-(2-aroylhydrazinyl)-4-oxo-
The cyclization of chloro- and nitro-substituted
(
Z)-4-(2-aroylhydrazinyl)-4-oxobut-2-enoic acids 5d
and 5e in 20–60 min produced mixtures of (E)- and
Z)-3-(5-aryl-1,3,4-oxadiazol-2-yl)acrylic acids and the
but-2-enoic acids 5 with POCl in DMF at 0–10°C
3
afforded only 5-(aroylhydrazinylidene)furan-2(5H)-
ones 8 in 58–90% yield (Scheme 4). Raising the tem-
perature above 10°C or increasing the reaction time to
more than 1 h resulted in the formation of a small
amount of (Z)-3-(5-aryl-1,3,4-oxadiazol-2-yl)acrylic
acids 7, but the yield of 8 was not improved. We also
(
corresponding 5-(aroylhydrazinylidene)furan-2(5H)-
ones, while the overall fraction of both isomeric acids
in the product mixture did not exceed 20%. Longer
reaction time led to reduction of the yield of 6 and 7.
Scheme 3.
O
O
O
H
NH2
AcOH, 20°C, 20 min
N
N
+
O
N
H
H
O
R
R
O
OH
O
O
5
a–5e
O
O
R
POCl , DMF, 20°C
O
3
OH
R
N
OH
N
N
N
6
a–6e
7a–7e
R = H (a), Me (b), MeO (c), Cl (d), O
2
N (e).
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 51 No. 7 2015

9
84
ROZHKOV et al.
Scheme 4.
In summary, we have developed two procedures for
the synthesis of pure E and Z isomers of 3-(5-aryl-
,3,4-oxadiazol-2-yl)acrylic acid. The first procedure
O
N
O
1
i or ii
5
a–5e
N
O
is based on the cyclization of (Z)-4-(2-aroylhydra-
zinyl)-4-oxobut-2-enoic acids by the action of phos-
phoryl chloride in DMF at room temperature and
subsequent separation of isomer mixture by fractional
crystallization. The second procedure is more general;
it includes recyclization of 5-(aroylhydrazinylidene)-
furan-2(5H)-ones obtained from (Z)-4-(2-aroylhydra-
zinyl)-4-oxobut-2-enoic acids and affords, depending
on the conditions, pure E or Z isomers of 3-(5-aryl-
H
R
8
a–8e
i: DMF, POCl
3
, 0–10°C, 20–60 min; ii: Me
0 min, 20°C; R = H (a), Me (b), MeO (c), Cl (d), O
2
CO, EtOCOCl,
N (e).
3
2
tried ethyl chloroformate in the presence of triethyl-
amine to cyclize acids 5. The reactions were carried
out at room temperature (30 min), and the products
were furanones 8a–8e (yield 54–81%).
1
,3,4-oxadiazol-2-yl)acrylic acids with high yields.
Presumably, the cyclization of (Z)-4-(2-aroylhydra-
zinyl)-4-oxobut-2-enoic acids 5 initially gives fura-
nones 8 which then undergo recyclization to 3-(5-aryl-
EXPERIMENTAL
1
13
The H and C NMR spectra were recorded on
1
5
,3,4-oxadiazol-2-yl)acrylic acids. For instance,
-(acetylhydrazinylidene)furan-2(5H)-one was report-
Bruker Avance DRX-400 and Bruker AM-300 spec-
1
trometers, respectively; the H NOESY spectra were
ed to rearrange into (E)-3-(5-methyl-1,3,4-oxadiazol-2-
yl)acrylic acid on heating in boiling acetic acid [10]. In
fact, by heating compounds 8a–8e in boiling acetic
acid we obtained (E)-3-(5-aryl-1,3,4-oxadiazol-2-yl)-
acrylic acids 6a–6e, whereas Z isomers 7a–7e were
obtained on a Bruker DRX-500 instrument; DMSO-d6
was used as solvent. The IR spectra were measured on
a Perkin Elmer Spectrum RX1 spectrometer with
Fourier transform from samples dispersed in mineral
oil and placed between NaCl plates. The melting
points were determined on an Electrothermal IA 9300
Series melting point apparatus. The high-resolution
mass spectra (electrospray ionization) were recorded
on a Bruker Daltonics MicrOTOF mass spectrometer
1
formed in boiling toluene (Scheme 5). By H NMR
monitoring of the transformation of furanones 8 in
boiling acetic acid we found that mixtures of Z and E
isomers 6 and 7 were formed at incomplete conver-
sion. After subsequent heating we succeeded in isolat-
ing only pure E isomers 6a–6e in 55–57% yield. The
yields of 6a–6e were improved to 75–92% when the
reaction was carried out at room temperature in
methylene chloride with addition of acetyl chloride.
The yields of 7a–7e in the recyclization in toluene
were 64–82%.
(
ion source temperature 180°C, eluent acetonitrile).
(Z)-4-(2-Aroylhydrazinyl)-4-oxobut-2-enoic
acids 5a–5e (general procedure). A solution of 0.1 mol
of the corresponding benzoic acid hydrazide in 60 mL
of glacial acetic acid was added under vigorous stirring
to a solution of 10.8 g (0.11 mol) of maleic anhydride
in 30 mL of glacial acetic acid. A solid separated from
the mixture immediately after the addition was com-
plete. The mixture was stirred for 20 min, and the
precipitate was filtered off and washed on a filter with
glacial acetic acid.
Scheme 5.
i
O
7a–7e
N
O
N
O
H
ii or iii
(Z)-4-(2-Benzoylhydrazinyl)-4-oxobut-2-enoic
acid (5a). Yield 91%, mp 177–179°C; published data
12]: mp 178–179°C. IR spectrum, ν, cm : 3210
6
a–6e
R
8
a–8e
–
1
[
(
1
7
(
(
i: PhMe, reflux, 1.5 h; ii: AcOH, reflux, 4 h;
iii: AcCl, CH Cl , 24 h, 20°C.
NH), 2720 (OH), 1707 (C=O), 1651 (C=O, amide),
2
2
628 (C=C), 1588 (C=Carom), 1538 (δN–H), 920 (OH),
1
14 (δC–Harom). H NMR spectrum, δ, ppm: 6.35 d
This procedure allowed us to obtain in high yields
both Z (7) and E isomers (6) of 3-(5-aryl-1,3,4-oxadi-
azol-2-yl)acrylic acids, including chloro- and nitro-
substituted derivatives, with high purity, which cannot
be achieved by direct cyclization of (Z)-4-(2-aroyl-
hydrazinyl)-4-oxobut-2-enoic acids 5.
1H, J = 12.2 Hz), 6.41 d (1H, J = 12.3 Hz), 7.48 t
2H, J = 7.5 Hz), 7.56 t (1H, J = 7.4 Hz), 7.90 d (2H,
J = 7.5 Hz), 10.65 s (1H), 10.90 s (1H), 13.20 s (1H).
(Z)-4-[2-(4-Methylbenzoyl)hydrazinyl]-4-oxobut-
2-enoic acid (5b). Yield 96%, mp 177–178°C; pub-
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 51 No. 7 2015

SYNTHESIS OF THE E AND Z ISOMERS OF 3-(5-ARYL-1,3,4-OXADIAZOL-2-YL)...
985
–
1
lished data [12]: mp 183–185°C. IR spectrum, ν, cm :
215 (NH), 2725, 2607 (OH), 1707 (C=O), 1662
isomer 7 was filtered off, washed on a filter with
3
water, and (if necessary) recrystallized from ethanol.
(
C=O, amide), 1624 (C=C), 1545 (δN–H), 1597, 1517
(
E)-3-(5-Phenyl-1,3,4-oxadiazol-2-yl)prop-2-
1
(C=Carom), 921 (OH), 846 (δC–Harom). H NMR spec-
enoic acid (6a). Yield 52% (20 min), 64% (60 min),
mp 191–193°C. IR spectrum, ν, cm : 2627, 2541
OH), 1714 (C=O), 1650 (C=C), 1604 (C=Carom), 1520
C=N), 1262, 1175, 1022 (C–O–C), 964 (trans-
CH=CH), 927 (OH), 688 (δC–Harom). H NMR spec-
trum, δ, ppm: 6.94 d (1H, J = 15.9 Hz), 7.47 d (1H, J =
6.2 Hz), 7.61 m (3H), 8.09 d (2H, J = 8.4 Hz), 13.19 s
1H). C NMR spectrum, δ , ppm: 122.96, 124.26,
27.09, 129.46, 129.55, 132.58, 162.32, 164.55,
–
1
trum, δ, ppm: 2.36 s (3H), 6.34 d (1H, J = 12.0 Hz),
6
7
1
.43 d (1H, J = 12.3 Hz), 7.29 d (2H, J = 8.1 Hz),
.79 d (2H, J = 8.1 Hz), 10.53 s (1H), 10.58 s (1H),
3.26 s (1H).
(
(
1
(
Z)-4-[2-(4-Methoxybenzoyl)hydrazinyl]-4-oxo-
1
(
1
1
but-2-enoic acid (5c). Yield 93%, mp 173–174°C;
published data [12]: mp 188–189°C. IR spectrum, ν,
cm : 3320 (NH), 2720 (OH), 1722 (C=O), 1663
1
3
C
–
1
+
65.94. Mass spectrum: m/z 216.0530 [M] .
(
C=O, amide), 1630 (C=C), 1606 (C=Carom), 1555
δN–H), 1265 (C–O), 945 (OH), 838 (δC–Harom).
H NMR spectrum, δ, ppm: 3.82 s (3H), 6.35 d (1H,
C H N O . Calculated: M 216.0535.
1
1
8
2
3
(
1
(E)-3-[5-(4-Methylphenyl)-1,3,4-oxadiazol-2-yl]-
prop-2-enoic acid (6b). Yield 54% (60 min), 61%
(90 min); mp 208–211°C. IR spectrum, ν, cm : 2674,
570 (OH), 1685 (C=O), 1643 (C=C), 1518 (C=N),
612, 1516 (C=Carom), 1279, 1215, 1093 (C–O–C), 970
trans-CH=CH), 826 (δC–Harom). H NMR spectrum,
δ, ppm: 2.39 s (3H), 6.90 d (1H, J = 15.9 Hz), 7.41 d
2H, J = 7.6 Hz), 7.42 d (1H, J = 16.1 Hz), 7.98 d (2H,
J = 12.6 Hz), 6.42 d (1H, J = 12.1 Hz), 7.03 d (2H, J =
.4 Hz), 7.88 d (2H, J = 8.4 Hz), 10.45 s (1H), 11.40 s
1H), 13.01 s (1H).
Z)-4-[2-(4-Chlorobenzoyl)hydrazinyl]-4-oxobut-
-enoic acid (5d). Yield 92%, mp 175–176°C. IR
–
1
8
(
2
1
(
(
1
2
–
1
spectrum, ν, cm : 3239 (NH), 2721 (OH), 1699
(
(
C=O), 1672 (C=O, amide), 1624 (C=C), 1594, 1508
C=Carom), 1543 (δN–H), 952 (OH), 850 (δC–Harom).
H NMR spectrum, δ, ppm: 6.34 d (1H, J = 12.5 Hz),
J = 8.2 Hz), 13.22 s (1H).
(
1
(E)-3-[5-(4-Methoxyphenyl)-1,3,4-oxadiazol-2-
yl]prop-2-enoic acid (6c). Yield 44% (60 min), 56%
120 min); mp 237–239°C; published data [8]:
mp 164°C (decomp.). IR spectrum, ν, cm : 2617,
524 (OH), 1715 (C=O), 1647 (C=C), 1617 (C=Carom),
6
7
1
.40 d (1H, J = 12.4 Hz), 7.55 d (2H, J = 8.1 Hz),
.9 d (2H, J = 8.1 Hz), 10.62 s (1H), 11.76 s (1H),
3.11 s (1H).
(
–
1
2
1
(
(
Z)-4-[2-(4-Nitrobenzoyl)hydrazinyl]-4-oxobut-2-
558 (C=N), 1264, 1231, 1178, 1090 (C–O–C), 986
trans-CH=CH), 926 (OH), 832 (δC–Harom). H NMR
1
enoic acid (5e). Yield 97%, mp 182–183°C; published
–
1
data [12]: mp 195–196°C. IR spectrum, ν, cm : 3229
NH), 2605 (OH), 1710 (C=O), 1679 (C=O, amide),
spectrum, δ, ppm: 3.84 s (3H), 6.91 d (1H, J =
6.2 Hz), 7.17 d (2H, J = 8.1 Hz), 7.44 d (1H, J =
16.2 Hz), 8.06 d (2H, J = 8.1 Hz), 13.18 s (1H).
Z)-3-(5-Phenyl-1,3,4-oxadiazol-2-yl)prop-2-
enoic acid (7a). Yield 14% (20 min), yield 3%
(
1
1
1
635 (C=C), 1568 (δN–H), 1590 (C=C ), 1523,
arom
1
346 (NO ), 917 (OH), 837 (δC–H ). H NMR
2
arom
(
spectrum, δ, ppm: 6.32 d (1H, J = 12.1 Hz), 6.43 d
1H, J = 11.9 Hz), 8.11 d (2H, J = 8.2 Hz), 8.35 d (2H,
J = 8.4 Hz), 10.65 s (1H), 10.97 s (1H), 13.10 s (1H).
(
–1
(
2
60 min), mp 155–158°C. IR spectrum, ν, cm : 2735,
517 (OH), 1712 (C=O), 1649 (C=C), 1604, 1513
(
E)- and (Z)-3-(5-Aryl-1,3,4-oxadiazol-2-yl)prop-
(C=Carom), 1550 (C=N), 1217, 1184, 1022 (C–O–C),
2
-enoic acids 6a–6c and 7a–7c (general procedure).
814 (cis-CH=CH), 927 (OH), 684 (δ C–Harom).
H NMR spectrum, δ, ppm: 6.69 d (1H, J = 12.3 Hz),
6.92 d (1H, J = 12.3 Hz), 7.63 m (3H), 7.99 d (2H, J =
1
Phosphoryl chloride, 1.1 mL (0.012 mol), was slowly
added under stirring to a solution of 0.01 mol of acid
5
a–5c in 10 mL of DMF, maintaining the temperature
below 40°C, and the mixture was kept for 20–120 min
depending on the substrate) at room temperature. The
7.9 Hz), 13.38 s (1H).
(
Z)-3-[5-(4-Methylphenyl)-1,3,4-oxadiazol-2-yl]-
(
prop-2-enoic acid (7b). Yield 10% (60 min), mp 186–
–
1
mixture was then poured into an ice–water mixture,
and the white precipitate of E isomer 6 was filtered off
and washed on a filter with water. To remove an im-
purity of the second isomer (if present), the product
was recrystallized from ethanol. The filtrate was kept
for 12 h at room temperature, and the precipitate of
189°C. IR spectrum, ν, cm : 2585, 2507 (OH), 1710
(C=O), 1647 (C=C), 1612, 1494 (C=Carom), 1553
(C=N), 1273, 1175, 1094 (C–O–C), 814 (cis-CH=CH),
927 (OH), 816 (cis-CH=CH), 825 (δ C–Harom).
1
H NMR spectrum, δ, ppm: 2.39 s (3H), 6.66 d (1H,
J = 12.2 Hz), 6.88 d (1H, J = 12.1 Hz), 7.44 d (2H, J =
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 51 No. 7 2015

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8
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ROZHKOV et al.
.5 Hz), 7.88 d (2H, J = 8.3 Hz), 13.23 s (1H). Mass
spectrum: m/z 230.0686 [M] . C H N O . Calculated:
M 230.0691.
Z)-3-[5-(4-Methoxyphenyl)-1,3,4-oxadiazol-2-
yl]prop-2-enoic acid (7c). Yield 16% (60 min),
6.92 d (1H, J = 5.7 Hz), 7.30 d (2H, J = 8.1 Hz), 7.79 d
(2H, J = 8.1 Hz), 7.93 d (1H, J = 5.6 Hz), 11.59 s (1H).
C NMR spectrum, δ , ppm: 21.11, 125.60, 126.62,
+
1
2
10
2
3
1
3
C
1
28.51, 128.82, 129.81, 130.09, 142.28, 142.36, 166.27.
(
5-[(4-Methoxybenzoyl)hydrazinylidene]furan-
–
1
mp 190–191°C. IR spectrum, ν, cm : 2726, 2525
OH), 1721 (C=O), 1640 (C=C), 1610 (C=Carom), 1584
C=N), 1265, 1217, 1175 (C–O–C), 814 (cis-CH=CH),
2(5H)-one (8c). Yield 82% (a), 70% (b); mp 152–
155°C. IR spectrum, ν, cm : 3375 (N–H), 1790
(C=O), 1685 (C=N), 1654 (C=O, amide), 1605, 1492
–
1
(
(
9
3
1
8
1
29 (OH), 836 (δC–Harom). H NMR spectrum, δ, ppm:
.84 s (3H), 6.64 d (1H, J = 12.5 Hz), 6.87 d (1H, J =
2.4 Hz), 7.16 d (2H, J = 8.5 Hz), 7.92 d (2H, J =
.5 Hz), 13.21 s (1H).
(C=Carom), 1526 (δN–H), 1249, 1177, 1096 (C–O–C),
1
8
6
26 (δC–H). H NMR spectrum, δ, ppm: 3.83 s (3H),
.90 d (1H, J = 5.6 Hz), 7.02 d (2H, J = 8.9 Hz), 7.89 d
(
2H, J = 8.9 Hz), 7.93 d (1H, J = 5.6 Hz), 11.51 s (1H).
1
3
5
-(Aroylhydrazinylidene)furan-2(5H)-ones 8a–
e (general procedures). a. A solution of 0.0043 mol of
C NMR spectrum, δ
124.67, 125.44, 128.54, 130.55, 142.37, 162.41, 166.32.
-[(4-Chlorobenzoyl)hydrazinylidene]furan-
C
, ppm: 55.5, 113.58, 115.05,
8
(
Z)-4-(2-aroylhydrazinyl)-4-oxobut-2-enoic acid 5a–5e
in 5 mL of DMF was cooled on an ice bath, and
.48 mL (0.0052 mol) of phosphoryl chloride was
slowly added at such a rate that the temperature did not
exceed 10°C. The mixture was kept for 30 min (20 min
for 5a or 60 min for 5d) at 0–10°C and poured into
an ice–water mixture, and the white precipitate was
filtered off and washed with water on a filter.
5
2
(5H)-one (8d). Yield 76% (a), 67% (b); mp 163–
0
–1
1
65°C. IR spectrum, ν, cm : 3308 (N–H), 1801
(
(
(
C=O), 1670 (C=N), 1649 (C=O, amide), 1595
C=Carom), 1527 (δN–H), 1263, 1098 (C–O–C), 824
δC–Harom). H NMR spectrum, δ, ppm: 6.93 d (1H,
1
J = 5.6 Hz), 7.56 d (2H, J = 8.5 Hz), 7.89 d (2H, J =
8
.1 Hz), 7.94 d (1H, J = 5.6 Hz), 11.81 s (1H).
C NMR spectrum, δ , ppm: 117.07, 125.85, 128.32,
1
3
b. Triethylamine, 1.53 mL (0.0111 mol), was added
to a suspension of 0.0085 mol of (Z)-4-(2-aroylhydra-
zinyl)-4-oxobut-2-enoic acid 5a–5e in 10 mL of ace-
tone, and the mixture became homogeneous. Ethyl
chloroformate, 0.9 mL (0.0094 mol), was then slowly
added under vigorous stirring, and the mixture was
stirred for 30 min and poured into water. The precip-
itate was filtered off, and thoroughly washed on a filter
with cold water and ethanol. Dimethylformamide can
also be used as solvent at the same volume ratio.
C
1
28.39, 129.77, 130.45, 131.98, 142.33, 166.21. Mass
+
spectrum: m/z 250.0140 [M] . C H ClN O . Calculat-
11
7
2
3
ed: M 250.0145.
-[(4-Nitrobenzoyl)hydrazinylidene]furan-
(5H)-one (8e). Yield 90% (a), 81% (b); mp 180–
5
2
1
1
–
1
83°C. IR spectrum, ν, cm : 3376 (N–H), 1791 (C=O),
689 (C=N), 1646 (C=O, amide), 1604 (C=Carom), 1535
(δN–H), 1527, 1348 (NO ), 1282, 1096 (C–O–C), 822
2
1
(δC–Harom). H NMR spectrum, δ, ppm: 6.96 d (1H,
5
-(Benzoylhydrazinylidene)furan-2(5H)-one
8a). Yield 58% (a), 54% (b); mp 130–132°C. IR spec-
trum, ν, cm : 3497, 3346 (N–H), 1799 (C=O), 1703
C=N), 1650 (C=O, amide), 1598 (C=Carom), 1524
δ N–H), 1250, 1102 (C–O–C), 708 (δC–Harom).
H NMR spectrum, δ, ppm: 6.90 d (1H, J = 5.6 Hz),
.50 t (2H, J = 7.5 Hz), 7.59 t (1H, J = 7.5 Hz), 7.87 d
2H, J = 8.1 Hz), 7.94 d (1H, J = 5.6 Hz), 11.69 s (1H).
J = 5.6 Hz), 7.95 d (1H, J = 5.6 Hz), 8.08 d (2H, J =
(
8
.8 Hz), 8.32 d (2H, J = 8.9 Hz), 12.07 s (1H).
–
1
Recyclization of compounds 8a–8e (general
(
procedures). a. Compound 8a–8e, 0.008 mol, was dis-
solved on heating in 30 mL of toluene, and the solution
was heated under reflux until an abundant solid precip-
itated (~90 min). The mixture was cooled, and the
precipitate was filtered off and washed on a filter with
toluene. Yield, %: 7a, 64; 7b, 73; 7c, 75.
(
1
7
(
1
3
C NMR spectrum, δ , ppm: 125.73, 126.67, 128.26,
28.45, 129.57, 132.07, 132.75, 142.35, 166.25. Mass
C
1
+
spectrum: m/z 216.0530 [M] . C H N O . Calculated:
1
1
8
2
3
(Z)-3-[5-(4-Chlorophenyl)-1,3,4-oxadiazol-2-yl]-
prop-2-enoic acid (7d). mp 211–214°C. IR spectrum,
ν, cm : 2652, 2590 (OH), 1708 (C=O), 1645 (C=C),
1580 (C=N), 1604, 1507 (C=Carom), 1287, 1178, 1094
(C–O–C), 911 (OH), 819 (cis-CH=CH), 833
M 216.0535.
-[(4-Methylbenzoyl)hydrazinylidene]furan-
(5H)-one (8b). Yield 81% (a), 71% (b); mp 144–
–
1
5
2
1
(
(
(
–
1
46°C. IR spectrum, ν, cm : 3357 (N–H), 1789
1
C=O), 1670 (C=N), 1654 (C=O, amide), 1608
(δC–Harom). H NMR spectrum, δ, ppm: 6.68 s (1H,
C=Carom), 1539 (δNH), 1263, 1102 (C–O–C), 820
δC–Harom). H NMR spectrum, δ, ppm: 2.37 s (3H),
J = 12.6 Hz), 6.91 d (1H, J = 12.3 Hz), 7.69 d (2H, J =
8.4 Hz), 7.95 d (2H, J = 8.4 Hz), 13.24 s (1H).
1
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 51 No. 7 2015

SYNTHESIS OF THE E AND Z ISOMERS OF 3-(5-ARYL-1,3,4-OXADIAZOL-2-YL)...
987
(
Z)-3-[5-(4-Nitrophenyl)-1,3,4-oxadiazol-2-yl]-
(C=Carom), 1527 (C=N), 1542, 1351 (NO
2
), 1294,
prop-2-enoic acid (7e). mp 206–208°C. IR spectrum,
1178, 1111 (C–O–C), 970 (trans-CH=CH), 934 (OH),
855 (δC–Harom). H NMR spectrum, δ, ppm: 7.00 d
(1H, J = 16.0 Hz), 7.48 d (1H, J = 15.8 Hz), 8.21 d
(2H, J = 8.1 Hz), 8.36 d (2H, J = 8.2 Hz), 13.20 s (1H).
–
1
1
ν, cm : 2656 (OH), 1697 (C=O), 1644 (C=C), 1607
C=Carom), 1550 (C=N) 1520, 1351 (NO ), 1278, 1175,
(
2
1
089 (C–O–C), 820 (cis-CH=CH), 933 (OH), 854
1
(
δC–Harom). H NMR spectrum, δ, ppm: 6.73 d (1H,
J = 12.5 Hz), 6.97 d (1H, J = 12.6 Hz), 8.22 d (2H, J =
.5 Hz), 8.45 d (2H, J = 8.4 Hz), 13.24 s (1H). Mass
REFERENCES
8
+
1. Jiang, X., Liu, Y., Tian, H., Qiu, W., Song, X., and
spectrum: m/z 261.0383 [M] . C H N O . Calculated:
11
7
3
5
Zhu, D., J. Mater. Chem., 1997, 7, 1395.
M 261.0386.
2. Nijegorodov, N. and Mabbs, R., Spectrochim. Acta,
b. Compound 8a–8e, 0.008 mol, was dissolved on
heating in 20 mL of glacial acetic acid, and the solu-
tion was heated for 4 h under reflux, cooled, and
poured into cold water. The precipitate was filtered off,
washed on a filter with water and ethanol, and repre-
cipitated from a sodium carbonate solution. Yield, %:
Part A, 2002, vol. 58, p. 349.
3. Peng, Z., Bao, Z., and Galvin, M.E., Adv. Mater., 1998,
vol. 10, p. 680.
4. Jin, S.-Ho, Kim, M.-Y., Kim, J.Y., Lee, K., and
Gal, Y.-S., J. Am. Chem. Soc., 2004, vol. 126, p. 2474.
5. Zhang, Y., Zuniga, C., Kim, S.-J., Cai, D., Barlow, S.,
Salman, S., Coropceanu, V., Bredas, J.-L., Kippelen, B.,
and Marder, S., Chem. Mater., 2011, vol. 23, p. 4002.
6
a, 55; 6b, 67; 6c, 59; 6d, 65; 6e, 64.
c. Compound 8a–8e, 0.004 mol, was dissolved in
6
7
. Akcelrud, L., Prog. Polymer. Sci., 2003, vol. 28, p. 875.
2
0 mL of methylene chloride (in some cases, 0.5–1 mL
. Saegusa, Y., Koshikawa, T., and Nakamura, S.,
J. Polym. Sci., Part A: Polym. Chem., 1992, vol. 30,
p. 1369.
. Detert, H. and Schollmeier, D., Synthesis, 1999, p. 999.
. Gutov, O.V., Cryst. Growth Des., 2013, vol. 13, p. 3953.
of DMF was added to improve the solubility), 1.42 mL
0.02 mol) of acetyl chloride was added, and the
(
mixture was left to stand for 24 h. The precipitate was
filtered off and washed with methylene chloride and
ethanol. Yield, %: 6a, 66; 6b, 75; 6c, 74; 6d, 92; 6e, 91.
8
9
1
0. Le Berre, A., Godin, J., and Garreau, R., C.R. Acad.
Sci., Ser. C, 1967, vol. 265, p. 570.
(
E)-3-[5-(4-Chlorophenyl)-1,3,4-oxadiazol-2-yl]-
prop-2-enoic acid (6d). mp 252–254°C. IR spectrum,
11. Siegrist, A.E., Moergeli, E., and Hoelzle, K., US Patent
no. 2765304, 1956.
12. Kolotova, N.V., Koz’minykh, E.N., Kolla, V.E., Syro-
pyatov, B.Ya., Voronina, E.V., and Koz’minykh, V.O.,
Pharm. Chem. J., 1999, vol. 33, no. 5, p. 248.
–
1
ν, cm : 2590 (OH), 1710 (C=O), 1642 (C=C), 1546
C=N), 1600 (C=Carom), 1263, 1170, 1083 (C–O–C),
15 (OH), 967 (trans-CH=CH), 832 (δ C–Harom).
(
9
1
H NMR spectrum, δ, ppm: 6.96 d (1H, J = 16.0 Hz),
1
3. Structure Determination of Organic Compounds: Tables
of Spectral Data, Pretsch, E., Bühlmann, P., and
Affolter, C., Eds., Berlin: Springer, 2000, 3rd ed.
Translated under the title Opredelenie stroeniya orga-
nicheskikh soedinenii. Tablitsy spektral’nykh dannykh,
Moscow: Mir, 2006, p. 174.
7
8
.46 d (1H, J = 16.0 Hz), 7.71 d (2H, J = 8.2 Hz),
.14 d (2H, J = 8.4 Hz), 13.27 s (1H).
(
E)-3-[5-(4-Nitrophenyl)-1,3,4-oxadiazol-2-yl]-
prop-2-enoic acid (6e). mp 268–270°C. IR spectrum,
–
1
ν, cm : 2670 (OH), 1692 (C=O), 1644 (C=C), 1607
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 51 No. 7 2015