Chemistry of iminofurans: V. Synthesis, structure, and cyclization of 4-R-4-oxo-2-[2-(2-oxo-1,2-diphenylethylidene)hydrazino]but-2-enoic acids

Article abstract of DOI:10.1134/S1070428010020156

Reactions of 1,2-diphenylethane-1,2-dione hydrazone with 4-aryl-2-hydroxy-4-oxobut-2-enoic and 2-hydroxy-5,5-dimethyl-4-oxohex-2-enoic acids provided 4-aryl-4-oxo-2-[2-(2-oxo-1,2-diphenylethylidene) hydrazino]but-2-enoic and 5,5-dimethyl-4-oxo-2-[2-(2-oxo

Full text of DOI:10.1134/S1070428010020156

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2010, Vol. 46, No. 2, pp. 236−240. © Pleiades Publishing, Ltd., 2010.
Original Russian Text © O.A. Komarova, N.M. Igidov, A.E. Rubtsov, V.V. Zalesov, A.S.Makarov, Yu.S. Toksarova, 2009, published in Zhurnal
Organicheskoi Khimii, 2010, Vol. 46, No. 2, pp. 242−246.
Chemistry of Iminofurans: V.*
Synthesis, Structure, and Cyclization of 4-R-4-Oxo-2-[2-(2-oxo-
1,2-diphenylethylidene)hydrazino]but-2-enoicAcids
O.A. Komarovaa, N.M. Igidovb, A.E. Rubtsova, V.V. Zalesov†a,
A. S. Makarovb, and Yu.S. Toksarovab
aPerm State University, Perm, 614990 Russia
e-mail: Alekhsandr.Rubtsov@psu.ru
bPerm State Farmaceutical Academy Perm, Russia
Received December 3, 2008
Abstract—Reactions of 1,2-diphenylethane-1,2-dione hydrazone with 4-aryl-2-hydroxy-4-oxobut-2-enoic and
2-hydroxy-5,5-dimethyl-4-oxohex-2-enoic acids provided 4-aryl-4-oxo-2-[2-(2-oxo-1,2-diphenyl-
ethylidene)hydrazino]but-2-enoic and 5,5-dimethyl-4-oxo-2-[2-(2-oxo-1,2-diphenylethylidene)hydrazino]hex-2-
enoic acids. The acids derivatives can exist in solutions as Z- and Ε-enehydrazino- or β-ketohydrazone forms, and
under the treatment with acetic anhydride they undergo cyclization into 5-aryl- and 5-tert-butyl-3-[2-(2-oxo-1,2-
diphenylethylidene)hydrazono]-2,3-furandiones.
DOI: 10.1134/S1070428010020156
It was shown formerly that 4-aryl-2-hydroxy-4-
oxobut-2-enoic acids Ia–If with benzophenone hydrazone
formed (2Z)-4-aryl-2-[2-(diphenylmethylene)hydrazino]-
4-oxobut-2-enoic acids II which in the polar solvent
existed partially in the β-ketohydrazone form: 4-aryl-2-
[(diphenylmethylene)hydrazono]-4-oxobutanoic acids [2]
(Scheme 1). Compounds II in acetic anhydride underwent
cyclization into 5-aryl-3-diphenylmethylenehydrazono-3H-
furan-2-ones [2]. Compounds II in [2] are presented only
by five examples, no information is given on their
spontaneous or thermal intramolecular cyclization into N-
substituted 5-aryl-3-hydrazono-3H-furan-2-ones in
contrast to the similar in structure 4-aryl(heteryl)-2-
arylamino--4-oxobut-2-enoic acids whose cyclization into
5-R-3-arylimino-3H-furan-2-ones is mentioned in [1, 3].
We carried out research on the synthesis of N-sub-
stituted 4-R-2-hydrazino-4-oxobut-2-enoic acids and their
tautomerism.
First from 1,2-diphenyl-1,2--ethanedione hydrazone
and 4-aryl-2-hydroxy-4-oxobut-2-enoic acids Ia–Ie we
obtained 4-aryl-4-oxo-2-[2-(2-oxo-1,2-diphenyl-
ethylidene)hydrazino]but-2-enoic acids IIIa–IIIe in 21–
79% yields (see the scheme).Alongside the main reaction
products we also isolated from the reaction mixture 1-
[(2-oxo-1,2--diphenylethylidene)hydrazone]-1,2-diphenyl-
ethane-1,2--dione (benzil azine). The ratio of the main
product and azine depended on the substituent in the
aromatic ring of initial acids. For instance, in the reaction
with 2-hydroxy-4-oxo-4-(4-fluorophenyl)but-2-enoic acid
the target product did not form, and the product of the
reaction of 4-(4-bromophenyl)-2-hydroxy-4oxobut-2-
enoic acid totally rearranged into the benzil azine in the
course of isolation and purification. In reactions of the
other acids the azine formation was negligible.
Scheme 1.
O
Ph
Ar
Ph
O
H
Ac2O
_2AcOH
N
N
O
N
H
N
Ar
O
O
Ph
Ph
IIа_IIf
R = Ph (a), 4-MeC6H4 (b), 4-MeOC6H4 (c), 4-EtOC6H4
(d), 4-ClC6H4 (e), t-Bu (f).
*For Communication IV, see [1].
†
Deceased.
In the IR spectra of compounds IIIa–IIIe recorded
236

CHEMISTRY OF IMINOFURANS:V.
237
and 14.14 ppm respectively. The downfield position of
the singlet belonging to the proton of the NH group is
apparently caused by the formation of the intramolecular
hydrogen bond with the carbonyl group C4=O of the acid
and (or) with the carbonyl group C2=O of the substituent
at the nitrogen atom. We failed to detect the signal of the
proton of carboxy group in compounds IIIc and IIIe
evidently due to its excessive broadening. Form B is
characterized by the presence of a singlet from the vinyl
proton C3–H at 6.13–6.27 ppm, the multiplet of aromatic
protons centered at 7.55–7.65 ppm, and a singlet of NH
group at 13.16–13.23 ppm. The location of the singlet of
NH proton is shifted downfield compared to the spectrum
of form A. Formerly in the spectra of aroylacetones
hydrazones the signal of the NH group of form B was
observed upfield from the corresponding signal of form
A [4]. This downfield position of the NH proton signal in
the spectrum of form B of compounds III may indicate
the formation of an intramolecular hydrogen bond with
the carbonyl group of the benzoyl substituent attached to
the C=N group. In the spectrum of β-ketohydrazone form
C the signals of vinyl proton and that of the NH group
are absent, a two-proton singlet is present from the C3H2
group at 4.53–4.59 ppm and a multiplet of aromatic
from mulls in mineral oil the absorption band of NH group
was observed in the region 3239–3258 cm–1. The
absorption band of the carbonyl from the carboxy groups
of compounds IIIa–IIIe is present in the region 1700–
1707 cm–1, and the band of the stretching vibrations of
the ketone carbonyl, in the region 1655–1662 cm–1. Like
in the spectra of analogous compounds II, in compounds
IIIa–IIIe due to the formation of an intramolecular
hydrogen bond between the hydrogen atom of the
enehydrazino group and the oxygen of the γ-carbonyl
group C4=O the absorption band of the latter is shifted to
lower frequencies, 1590–1620 cm–1, and it is impossible
to separate it from the group of the absorption bands.
According to 1H NMR data compounds IIIa–IIIe in
DMSO-d6 exist in Z- and Ε-enehydrazino forms A, B
and β-ketohydrazone forms C and D, with form A
prevailing, in contrast to the analogous acids II which
contain a phenyl instead of a benzoyl substituent at the
carbon atom of the C=N group; acids II in DMSO-d6
exist in two forms (Scheme 2). Form A is characterized
by the presence in the 1H NMR spectrum of a singlet of
the vinyl proton C3–H in the range 6.21–6.43 ppm, of a
multiplet of aromatic protons centered at 7.45–7.65 ppm,
a singlet of NH group at 12.71–12.77 ppm, and also of a
broadened singlet of the carboxy group proton in the
spectra of compounds IIIa, IIIb, IIId at 14.25, 14.22,
1
protons centered at 7.45–7.65 ppm. In the H NMR
spectrum of form D appears a two-proton singlet of the
Scheme 2.
Ph
N
Ph
O
O
O
N
O
H
R
R
Ph
H2N N
Ph
O
N
OH
O
H
+
O
O
_H2O
O
N
H
H
O
Iа_If
OH
Ph
O
R
Ph
IIIа_IIIf, A
B
Ph
O
N
Ph
Ph
Ph
O
O
R
Ac2O
_2AcOH
O
N
N
N
O
N
O
N
H
O
R
O
O
Ph
OH
O
R
Ph
IVа_IVf
C
D
R = Ph (a), 4-MeC6H4 (b), 4-MeOC6H4 (c), 4-EtOC6H4 (d), 4-ClC6H4 (e), t-Bu (f).
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KOMAROVA et al.
238
C3H2 group at 4.31–4.38 ppm and a multiplet of aromatic
protons centered at 7.45–7.65 ppm. 1H NMR spectra do
not allow an unambiguous assignment of signals to
a definite ketohydrazone form (C or D), however,
considering the data obtained in the study of hydrazones
of esters of 2,4-dioxobutanoic acids [5, 6], it is possible
to suggest that form C is predominant in the solution.
in the crystal in the form C and its prevalence in the
solution apparently is due to the lack of the stabilization
of the six-membered H-chelate ring in the A form by
aromatic substituent in the position 4.As a result it proved
to be more feasible to form a π-conjugated system
O=C1–C2=N–N=C(Ph)–C(Ph)=O involving the
substituent at the nitrogen atom.
The intramolecular cyclization of acids IIIa–IIIf by
boiling in acetic anhydride resulted in the corresponding
5-aryl- and 5-tert-butyl-3-[2-(diphenylmethylene)-
hydrazono]-3H-furan-2-ones IVa–IVf.
The replacement of the aryl fragment in acids Ia–Ie
by the tert-butyl group did not change the direction of the
reaction, and 2-hydroxy-5,5-dimethyl-4-oxohex-2-enoic
acid (If) with benzil hydrazone in toluene afforded 5,5-
dimethyl-4-oxo-2-[2-(2-oxo-1,2-diphenylethylidene)-
hydrazino]hex-2-enoic acid (IIIf). In acetic acid, similarly
to the reactions of 4-(4-fluorophenyl)-, 4-(4-bromo-
phenyl)-2-hydroxy-4-oxobut-2-enoic acids, the process
is directed to the benzil azine formation, apparently due
to the rearrangement of the arising acid IIIf or because
of predominant formation of azine under the conditions
of hard acid catalysis.
Furanones IVa–IVf are brightly colored from yellow
to dark red crystalline substances. The IR spectra of
compounds IVa–IVf contain the absorption band in the
region 1798–1814 cm–1 characteristic of the stretching
vibrations of the lactone carbonyl of the furan ring, the
absorption band of the carbonyl group from the substituent
at the nitrogen atom at 1664–1676 cm–1. In the 1H NMR
spectrum of compound IVd a three-proton triplet of the
CH3CH2 group is observed at 1,3 ppm, the two-proton
quartet from CH3CH2 group appears at 4.1 ppm, the
singlet of vinyl proton C4H, at 7.37 ppm, and a set of
aromapic protons gives rise to a multiplet centered at
7.45 ppm.
In the IR spectrum of compound IIIf recorded from
a mull in mineral oil lacks the absorption band of the NH
group in the region 3200–3600 cm–1. The absorption band
of the carbonyl of the carboxy group is observed in the
region 1699 cm–1, and the bands of the stretching
vibrations of the ketone carbonyls are present in the region
1681 and 1662 cm–1. The absence of an amino group
and the high-frequency position of the band of C4=O
carbonyl shows that acid IIIf in the crystal state exists in
the β-ketohydrazone form C.
EXPERIMENTAL
IR spectra were recorded on a spectrophotometer
FSM-1201 from mulls in mineral oil. 1H NMR spectra
were registered on a spectrometer Varian Mercury Plus-
300 (300.05 MHz) in DMSO-d6, internal reference
HMDS. The reaction progress was monitored and the
purity of compounds was checked by TLC on Silufol UV-
254 or Sorbfil plates, eluent ether–benzene–acetone,
10:9:1, the spots visualized in iodine vapor.
According to 1H NMR spectra, compound IIIf exists
in DMSO-d6 in Z- and Ε-enehydrazino fotms A, B and β-
ketohydrazone forms C and D, with form C prevailing.
Form A is characterized by the presence in the 1H NMR
spectrum of a singlet of the vinyl proton C3–H at 5.79 ppm,
of a multiplet of aromatic protons centered at 7.55 ppm,
a singlet of NH group at 12.24 ppm, and also of a broaden-
ed singlet of the carboxy group proton at 13.21 ppm. Form
4-Oxo-2-(2-oxo-1,2-diphenylethylidene-
hydrazino)-4-phenylbut-2-enoic acids IIIa–IIIf. To
a solution of 0.02 mol of acid Ia–If in 20 ml of ethanol
was added a solution of 0.02 mol of 1,2-diphenyl-
1,2-ethanedione hydrazone in 20 ml of ethanol, the mixture
was kept for 24 h at 20–25°C, then cooled to 0°C, the
separated precipitate was filtered off and recrystallized
from acetonitrile.
1
B is characterized by the presence in the H NMR
spectrum of a singlet of the vinyl proton C3–H at 6.65 ppm,
of a multiplet of aromatic protons centered at 7.55 ppm,
a singlet of NH group at 12.78 ppm. In the spectrum of
β-ketohydrazone form C the signals of vinyl proton and
that of the NH group are absent, a two-proton singlet is
present from the C3H2 group at 4.12 ppm and a multiplet
of aromatic protons centered at 7.55 ppm. In the 1H NMR
spectrum of form D appears a two-proton singlet of the
C3H2group at 3.91 ppm and a multiplet of aromatic protons
centered at 7.55 ppm. The existence of compound IIIf
4-Oxo-2-(2-oxo-1,2-diphenylethylidene-
hydrazino)-4-phenylbut-2-enoic acid (IIIa). Yield
1.7 g (21%), orange crystals, t.decomp. 144– 146°C
(from acetonitrile). IR spectrum, ν, cm–1: 3258 (NH),
1
1707 (COO), 1658 (CO). H NMR spectrum, δ, ppm,
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 46 No. 2 2010

CHEMISTRY OF IMINOFURANS:V.
239
CH3CH2O), 4.12 m (2H, CH3CH2O), 4.53 s (2H, CH2),
7.59 m (14H, 2C6H5, C6H4), 14.14 br.s (1H, OH); form
D (3%): 1.33 m (3H, CH3CH2O), 4.12 m (2H,
CH3CH2O), 4.36 s (2H, CH2), 7.59 m (14H, 2C6H5,
C6H4), 14.14 br.s (1H, OH). Found, %: C 70.58; H 4.99;
N 6.33. C26H22N2O5. Calculated, %: C 70.59; H 4.98;
N 6.33.
form A(62.5%): 6.43 s (1H, CH), 7.65 m (15H, 3C6H5),
12.77 s (1H, NH), 14.25 br.s (1H, OH); form B (13.1%):
6.29 s (1H, CH), 7.65 m (15H, 3C6H5), 13.20 s (1H,
NH), 14.25 br.s (1H, OH); form C (18.4%): 4.59 s
(2H, CH2), 7.65 m (15H, 3C6H5), 14.25 br.s (1H, OH);
form D (6%): 4.43 s (2H, CH2), 7.65 m (15H, 3C6H5),
14.25 br.s (1H, OH). Found, %: C 72.40; H 4.54; N 7.03.
C24H18N2O4. Calculated, %: C 72.36; H 4.52; N 7.04.
4-Oxo-2-(2-oxo-1,2-diphenylethylidene-
hydrazino)-4-(4-chlorophenyl)but-2-enoic acid
(IIIe). Yield 6.8 g (79%), orange crystals, t.decomp. 147–
148°C (from acetonitrile). IR spectrum, ν, cm–1: 3257
4-(4-Methylphenyl)-4-oxo-2-(2-oxo-1,2-di-
phenylethylidenehydrazino)but-2-enoic acid (IIIb).
Yield 3.9 g (47%), orange crystals, t.decomp. 139–140°C
(from acetonitrile). IR spectrum, ν, cm–1: 3246 (NH),
1
(NH), 1705 (COO), 1662 (CO). H NMR spectrum, δ,
1
ppm, form A (60%): 6.39 s (1H, CH), 7.6 m (14H, 2C6H5,
C6H4), 12.71 s (1H, NH); form B (16%): 6.27 s (1H,
CH), 7.60 m (14H, 2C6H5, C6H4), 13.16 s (1H, NH);
form C (19.5%): 4.54 s (2H, CH2), 7.6 m (14H, 2C6H5,
C6H4); form D (4.5%): 4.36 s (2H, CH2), 7.6 m (14H,
2C6H5, C6H4). Found, %: C 66.60; H 3.92; N 6.48.
C24H17ClN2O4. Calculated, %: C 66.59; H 3.93; N 6.47.
1700 (COO), 1655 (CO). H NMR spectrum, δ, ppm,
form A (68%): 2.33 s (3H, CH3), 6.21 s (1H, CH),
7.55 m (14H, 2C6H5, C6H4), 12.76 s (1H, NH), 14.22 br.s
(1H, OH); form B (13%): 2.36 s (3H, CH3), 6.13 s (1H,
CH), 7.55 m (14H, 2C6H5, C6H4), 13.21 s (1H, NH),
14.22 br.s (1H, OH); form C (18%): 2.40 s (3H, CH3),
4.55 s (2H, CH2), 7.45 m(14H, 2C6H5, C6H4), 14.22 br.s
(1H, OH); form D(1%): 2.38 C (3H, CH3), 4.39 s (2H,
CH2), 7.45 m (14H, 2C6H5, C6H4), 14.22 br.s (1H, OH).
Found, %: C 72.84; H 4.86; N 6.82. C25H20N2O4.
Calculated, %: C 72.82; H 4.85; N 6.80.
5,5-Dimethyl-4-oxo-2-[2-(2-oxo-1,2-diphenyl-
ethylidene)hydrazino]hex-2-enoic acid (IIIf). Yield
5.07 g (67%), yellow crystals, t.decomp. 135–136°C (from
toluene). IR spectrum, ν, cm–1: 3257, 1699 (COO), 1681
4-(4-Methoxyphenyl)-4-oxo-2-(2-oxo-1,2-
diphenylethylidenehydrazino)but-2-enoic acid (IIIc).
Yield 3.8 g (44%), orange crystals, t.decomp. 168–171°C
(from acetonitrile). IR spectrum, ν, cm–1: 3275 (NH),
1
(CO). H NMR spectrum, δ, ppm, form A(24.9%):
1.01 s (9H, 3CH3), 5.79 s (1H, CH), 7.55 m(10H, 2C6H5),
12.24 s (1H, NH), 13.21 br.s (1H, OH); form B (18.1%):
1.03 s (9H, 3CH3), 5.65 s (1H, CH), 7.55 m (10H,
2C6H5), 12.78 s (1H, NH), 13.21 br.s(1H, OH); form C
(54.2%): 1.18 s (9H, 3CH3), 4.12 s(2H, CH2), 7.55 m
(10H, 2C6H5), 13.21 br.s (1H, OH); form D (2.8%): 1.18
s (9H, 3CH3), 3.91 s (2H, CH2), 7.55 m (10H, 2C6H5),
13.21 br.s (1H, OH). Found, %: C 69.86; H 5.84; N 7.40.
C22H22N2O4. Calculated, %: C 69.84; H 5.82; N 7.41.
1
1700 (COO), 1660 (CO). H NMR spectrum, δ, ppm,
form A (74.6%): 3.76 s (3H, CH3O), 6.36 s (1H, CH),
7.5 m (14H, 2C6H5, C6H4), 12.73 s (1H, NH); form B
(9.4%): 3.78 s (3H, CH3O), 6.21 s (1H, CH), 7.45 m
(14H, 2C6H5, C6H4), 13.2 s (1H, NH); form C (15%):
3.81 s (3H, CH3O), 4.49 (4.31) s (2H, CH2), 7.45 m (14H,
2C6H5, C6H4); form D (1%): 3.81 s (3H, CH3O), 4.31
C (2H, CH2), 7.45 m (14H, 2C6H5, C6H4). Found, %:
C 70.07; H 4.69; N 6.55. C25H20N2O5. Calculated, %:
C 70.09; H 4.67; N 6.54.
3-(2-Oxo-1,2-diphenylethylidenehydrazono)-5-
phenyl-3H-furan-2-ones IVa–IVf. To 0.01 mol of acid
IIIa–IIIf was added 10 ml of acetic anhydride, and the
mixture was heated to boiling, On cooling the mixture to
0°C the separated precipitate was filtered off and
recrystallized from toluene.
4-Oxo-2-(2-oxo-1,2-diphenylethylidene-
hydrazino)-4-(4-ethoxyphenyl)but-2-enoic acid
(IIId). Yield 3.6 g (41%), orange crystals, t.decomp. 157–
159°C (from acetonitrile). IR spectrum, ν, cm–1: 3239
3-(2-Oxo-1,2-diphenylethylidenehydrazono)-5-
phenyl-3H-furan-2-one (VIa). Yield 3.7 g (97%),
orange crystals, mp 159–160°C (from toluene). IR
spectrum, ν, cm–1: 1804 (C2=Olactone), 1664 (C=O), 1592,
1578 (C=N, C=C). Found, %: C 75.77; H 4.20; N 7.37.
C24H16N2O3. Calculated, %: C 75.79; H 4.21; N 7.37.
1
(NH), 1665 (COO, CO). H NMR spectrum, δ, ppm,
form A (40.5%): 1.33 m (3H, CH3CH2O), 4.12 m (2H,
CH3CH2O), 6.39 s (1H, CH), 7.59 m (14H, 2C6H5, C6H4),
12.77 s (1H, NH), 14.14 br.s (1H, OH); form B (21%):
1.33 m (3H, CH3CH2O), 4.12 m (2H, CH3CH2O), 6.25 s
(1H, CH), 7.59 m (14H, 2C6H5, C6H4), 13.23 s (1H, NH),
14.14 br.s (1H, OH); form C (35.5%): 1.33 m (3H,
5-(4-Methylphenyl)-3-(2-oxo-1,2-diphenyl-
ethylidenehydrazono)-3H-furan-2-one (IVb). Yield
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KOMAROVA et al.
240
C24H15ClN2O3. Calculated, %: C 69.48; H 3.62; N 6.76.
3.9 g (99%), orange crystals, mp 184–186°C(from
toluene). IR spectrum, ν, cm–1: 1809 (C2=Olactone), 1670
(C=O), 1591, 1570 (C=N, C=C). Found, %: C 76.17;
H 4.59; N 7.10. C25H18N2O3. Calculated, %: C 76.14;
H 4.57; N 7.11.
5-tert-Butyl-3-(2-oxo-1,2-diphenylethylidene-
hydrazono)-3H-furan-2-one (IVf). Yield 3.03 g (84%),
orange crystals, mp 143–144°C (from toluene–hexane).
IR spectrum, ν, cm–1: 1798 (C2=Olactone), 1676 (C=O).
Found, %: C 73.31; H 5.54; N 7.74. C22H20N2O3.
Calculated, %: C 73.33; H 5.56; N 7.78.
5-(4-Methoxyphenyl)-3-(2-oxo-1,2-diphenyl-
ethylidenehydrazono)-3H-furan-2-one (IVc). Yield
The study was carried out under a financial support
of the Russian Foundation for Basic Research (grant no.
08-03-00488).
4.0 g (97%), dark red crystals, mp 93–95°C (from
toluene). IR spectrum, ν, cm–1: 1804 (C2=Olactone), 1668
(C=O), 1589, 1574 (C=N, C=C). Found, %: C 73.18;
H 4.38; N 6.83. C25H18N2O4. Calculated, %: C 73.17;
H 4.39; N 6.83.
REFERENCES
3-(2-Oxo-1,2-diphenylethylidenehydrazono)-5-
(4-ethoxyphenyl)-3H-furan-2-one (IVd). Yield 3.9 g
(93%), orange crystals, mp 160–161°C(from toluene).
IR spectrum, ν, cm–1 : 1811 (C=O), 1668 (C=O), 1591,
1574 (C=N, C=C). 1H NMR spectrum, δ, ppm: 1.3 t (3H,
CH3), 4.10 q (2H, CH2),7.37 s (1H, CH), 7.45 m (14H,
2C6H5, C6H4). Found, %: C 73.59; H 4.74; N 6.58.
C26H20N2O4. Calculated, %: C 73.58; H 4.72; N 6.60.
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5. Yakimovich, S.I. and Zerova, I.V., Zh. Org. Khim., 1980,
vol. 16, p. 1633.
6. Yakimovich, S.I., Zerova, I.V., and Gavrilova, N.N., Zh. Org.
Khim., 1977, vol. 13, p. 263.
3-(2-Oxo-1,2-diphenylethylidenehydrazono)-5-
(4-chlorophenyl)-3H-furan-2-one (IVe). Yield 4.1 g
(98%), orange crystals, mp 174–175°C(from toluene).
IR spectrum, ν, cm–1: 1814 (C=O), 1664 (C=O), 1593,
1575 (C=N, C=C) . Found, %: C 69.46; H 3.60; N 6.78.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 46 No. 2 2010