Chemistry of iminofurans: VI.* Synthesis and structure of 2-(2-ylidenehydrazino)-substituted 4-aryl-4-oxobut-2-enoic and 5,5-dimethyl-4-oxohex-2-enoic acids

Article abstract of DOI:10.1134/S1070428011010131

Hydrazones derived from substituted benzophenones and fluorenone reacted with 4-aryl-2-hydroxy-4-oxobut-2-enoic and 2-hydroxy-5,5-dimethyl-4-oxohex-2- enoic acids to give the corresponding 2-(2-ylidenehydrazino) derivatives which may be used as initial compounds for the synthesis of 3-hydrazono-3H-furan-2- ones. The obtained but-2-enoic and hex-2-enoic acid derivatives in solution may exist as Z- and E-isomeric enehydrazine tautomers or hydrazone tautomers with syn or anti orientation of substituents with respect to the double C=N bond.

Full text of DOI:10.1134/S1070428011010131

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2011, Vol. 47, No. 1, pp. 109–114. © Pleiades Publishing, Ltd., 2011.
Original Russian Text © O.A. Komarova, N.M. Igidov, N.N. Koryagina, A.S. Makarov, Yu.S. Toksarova, A.E. Rubtsov, 2011, published in Zhurnal
Organicheskoi Khimii, 2011, Vol. 47, No. 1, pp. 110–115.
Chemistry of Iminofurans: VI.* Synthesis and Structure
of 2-(2-Ylidenehydrazino)-Substituted 4-Aryl-4-oxobut-2-enoic
and 5,5-Dimethyl-4-oxohex-2-enoic Acids
O. A. Komarovaa, N. M. Igidovb, N. N. Koryaginaa, A. S. Makarovb,
Yu. S. Toksarovab, and A. E. Rubtsova
a Perm State University, ul. Bukireva 15, Perm, 614990 Russia
e-mail: Rubtsov@psu.ru
b Perm State Pharmaceutical Academy, Perm, Russia
Received September 7, 2009
Abstract—Hydrazones derived from substituted benzophenones and fluorenone reacted with 4-aryl-2-hy-
droxy-4-oxobut-2-enoic and 2-hydroxy-5,5-dimethyl-4-oxohex-2-enoic acids to give the corresponding
2-(2-ylidenehydrazino) derivatives which may be used as initial compounds for the synthesis of 3-hydrazono-
3H-furan-2-ones. The obtained but-2-enoic and hex-2-enoic acid derivatives in solution may exist as Z- and
E-isomeric enehydrazine tautomers or hydrazone tautomers with syn or anti orientation of substituents with
respect to the double C=N bond.
DOI: 10.1134/S1070428011010131
We previously showed that 4-aryl-2-hydroxy-4-oxo-
but-2-enoic acids I react with benzophenone hydra-
zone and benzil monohydrazone to give the corre-
sponding 2-(2-methylidenehydrazino)-substituted
derivatives with Z configuration at the double C=C
bond. The products were found to exist in polar sol-
vents as 4-aryl-2-(methylidenehydrazono)-4-oxobuta-
noic acids and undergo cyclization to 3-hydrazono-3H-
furan-2-one derivatives by the action of acetic anhy-
dride [1, 2]. Neither spontaneous nor thermally
induced intramolecular cyclization of 4-R-2-(methyli-
denehydrazono)-4-oxobutanoic acids into N-substitut-
ed 5-aryl-3-hydrazono-3H-furan-2-ones was reported
in [1, 2], though intramolecular ring closure of struc-
turally related 4-aryl(hetaryl)-2-arylamino-4-oxobut-2-
enoic acids into 5-R-3-arylimino-3H-furan-2-ones was
noted in [3, 4].
ene]hydrazino}-4-oxobut-2-enoic acids IIIa–IIIe
(Scheme 1). Unlike previously reported (2Z)-4-aryl-2-
[2-(diphenylmethylidene)hydrazino]-4-oxobut-2-enoic
acids, molecules IIIa–IIIe contained a substituent in
the para position of one aromatic ring. The yields of
IIIa–IIIe were 81–87%.
In the IR spectra of crystalline samples of IIIa–IIIe
(mineral oil) we observed a shoulder at 1599–
1602 cm–1, and a broadened absorption band was
present in the region 3226–3258 cm–1 (νNH), indicat-
ing that these compounds exist as enhydrazine tauto-
mer A or B with the carboxylic group involved in
intra- or intermolecular hydrogen bond [2].
According to the 1H NMR data, compounds IIIa–
IIIe in DMSO-d6 solution give rise to equilibrium
tautomeric mixtures of ketoenehydrazine (A, B) and
ketohydrazone structures (C, D) with syn and anti
orientation of substituents at the N′=C bond. Presum-
ably, the existence of tautomeric equilibrium in a polar
solvent is related to stabilization of ketohydrazone
structure due to formation of conjugated Ar2C=N–
N=C–C=O bond sequence. Enehydrazine tautomers A
(Z,E) and B (Z,Z) are characterized by a singlet from
the vinylic proton at δ 6.02–6.14 or 6.09–6.19 ppm and
a singlet from the NH proton at δ 12.64–12.76 or
We continued studies in the field of synthesis of
N-substituted 4-R-2-hydrazino-4-oxobut-2-enoic acids
with a view to examine their tautomeric transforma-
tions and intramolecular cyclization. Initially, by reac-
tion of 4-aryl-2-hydroxy-4-oxobut-2-enoic acids Ia–Id
with substituted benzophenone hydrazones IIa and IIb
we obtained (2Z)-4-aryl-2-{2-[(E)-aryl(phenyl)methyl-
* For communication V, see [1].
109

KOMAROVA et al.
110
Scheme 1.
R2
H
N
O
OH
NNH2
O
N
OH
OH
+
–H2O
O
O
R1
R2
R1
Ia–Id
IIa, IIb
A
R2
R2
R2
H
N
N
O
N
O
O
N
O
N
O
N
OH
OH
OH
O
R1
R1
R1
B
C
D
IIIa–IIIe
I, R1 = H (a), Me (b), MeO (c), Cl (d); II, R2 = Me (a), MeO (b); III, R1 = MeO, R2 = Me (a); R1 = H, R2 = MeO (b);
R1 = Me, R2 = MeO (c); R1 = R2 = MeO (d); R1 = Cl, R2 = MeO (e).
12.73–12.85 ppm, respectively [5]. The downfield po-
sition of the NH signal is determined by intramolecular
hydrogen bonding between the NH proton and C4=O
carbonyl oxygen atom. The overall fraction of struc-
tures A and B ranges from 63 to 79%, the former
prevailing (35–45%), which is quite consistent with
published data [5, 6]. Hydrazone tautomers C (E) and
D (Z) give rise to a singlet from the C3H2 methylene
group at δ 4.39–4.54 and 4.45–4.60 ppm, respectively.
The equilibrium between structures C and D is dis-
placed toward the former, presumably for steric and
thermodynamic reasons. Unlike 4-aryl-2-[2-(2-oxo-
Scheme 2.
NNH2
H
N
O
O
OH
O
N
OH
OH
+
O
R
R
Ia–Ie
A
HO
O
O
N
N
H
N
O
O
N
R
OH
R
B
IVa–IVe
E
R = H (a), Me (b), MeO (c), Cl (d), EtO (e).
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 47 No. 1 2011

CHEMISTRY OF IMINOFURANS: VI.
111
1,2-diphenylethylidene)hydrazino]-4-oxobut-2-enoic
acids [1], no ketoenehydrazine tautomers of IIIa–IIIe
with E configuration of the double C=C bond were de-
tected in DMSO-d6 solution, which may be due to ad-
ditional stabilization of Z-isomeric structures C and D
via formation of strong intramolecular hydrogen bond.
with the C=N–N=C–C=O fragment for steric reasons;
as a result, structure C prevails due to additional stabi-
lization by intramolecular hydrogen bond C4=O···HN.
Enehydrazine tautomer A is characterized by vinylic
proton signal at δ 6.51–6.54 ppm and NH singlet at
δ 13.78–13.85 ppm. Hydrazone structure C gives
a two-proton singlet from the C3H2 methylene group at
δ 4.41–4.48 ppm. Signal from the carboxy proton was
not detected, presumably because of its considerable
broadening.
Replacement of the aryl(phenyl)methylidene frag-
ment by fluoren-9-ylidene fragment in which both aro-
matic rings are fixed in one plane does not change the
reaction direction. 4-Aryl-2-hydroxy-4-oxobut-2-enoic
acids Ia–Ie reacted with fluorenone hydrazone to give
(2Z)-4-aryl-2-[2-(9H-fluoren-9-ylidene)hydrazino]-
4-oxobut-2-enoic acids IVa–IVe in 81–94% yield
(Scheme 2). Compounds IVa–IVe displayed in the IR
spectra (mineral oil) a shoulder at 1564–1568 cm–1 and
a broadened absorption band in the region 3304–
3314 cm–1 due to stretching vibrations of the NH
group; these findings indicate that acids IVa–IVe in the
crystalline state have enehydrazine structure and that
the carboxylic group is involved in intra- or intermo-
lecular hydrogen bond (or the nitrogen atom is pro-
1
The H NMR spectra of compounds IVb and IVd
in CDCl3 displayed a different pattern. The spectra
lacked signals assignable to ketohydrazone structure
C, whereas those belonging to E-isomeric ketoenehy-
drazine E were observed in addition to signals of
Z-ketoenehydrazine A. This may be rationalized in
terms of weaker solvation by less polar CDCl3 which,
unlike DMSO-d6, weakens intramolecular hydrogen
bonds thus destabilizing ketoenehydrazine structures A
and E. Tautomer A displays the NH signal at δ 14.24
(IVb) or 14.26 ppm (IVd); the corresponding signal of
E-isomeric ketoenehydrazine E is observed at δ 10.88
(IVb) or 10.95 ppm (IVd). The vinylic 3-H proton
signal of both A and E is overlapped by aromatic
proton signals. The downfield position of that signal
may result from formation of strong intramolecular hy-
drogen bond and additional effect of the fluorenylidene
substituent through the p–π conjugation system involv-
ing nitrogen atoms [7]. No carboxy proton signal was
observed in the 1H NMR spectra of these compounds.
1
tonated by the carboxylic group) [2]. The H NMR
data allowed us to conclude that, unlike derivatives
IIIa–IIIe, compounds IVa and IVc–IVe in DMSO-d6
exist as two tautomeric ketoenehydrazine (A) and
ketohydrazone structures (C), the fraction of tautomer
A being 29–47%. Presumably, structure C predomi-
nates due to formation of the C=N–N=C–C=O con-
jugated bond system which is additionally stabilized
by the fluorenylidene fragment oriented in the same
plane. By contrast, the aryl substituents in benzophe-
none derivatives IIIa–IIIe and (2Z)-4-aryl-2-[2-(di-
phenylmethylidene)hydrazino]-4-oxobut-2-enoic acids
[2] are most likely to be forced out from conjugation
We also examined reactions of 2-hydroxy-5,5-di-
methyl-4-oxohex-2-enoic acid (V) with hydrazones
derived from substituted benzophenones and fluore-
none. In all cases, the corresponding 5,5-dimethyl-2-
Scheme 3.
R1
N
R2
R2
N
R1
O
OH
NNH2
R2
H
N
O
H
N
O
OH
O
O
t-Bu
+
R1
OH
OH
–H2O
O
t-Bu
t-Bu
V
IIa–IIe
A
VIa–VIe
B
R1
N
R2
R2
R1
N
O
N
N
O
O
OH
OH
t-Bu
t-Bu
O
C
VIa–VIe
D
R1 = Ph, R2 = 4-MeC6H4 (a), 4-MeOC6H4 (b), 4-BrC6H4 (c), Ph (d); R1R2 = biphenyl-2,2′-diyl (e).
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 47 No. 1 2011

KOMAROVA et al.
112
(2-ylidenehydrazino)-4-oxohex-2-enoic acids VIa–VIe
were obtained in 45–86% yield (Scheme 3), i.e., re-
placement of the 4-aryl substituent in acids I by tert-
butyl group did not result in change of the reaction
direction. The IR spectra of crystalline compounds
VIa–VIe (mineral oil) contained a broadened absorp-
tion band at 3304–3314 cm–1 (NH), absorption bands
due to carboxylic (1723–1745 cm–1) and carbonyl
groups (C4=O, 1598–1603 cm–1), and an absorption
band in the region 1576–1582 cm–1, which is typical of
stretching vibrations of C=C and C=N bonds. Broad-
ening of the NH band and low-frequency position of
the C4=O band suggest that acids VIa–VIe in the crys-
talline state exist as enehydrazine tautomers stabilized
by intramolecular hydrogen bond C4=O···HN [2, 8].
The 1H NMR spectra of VIa–VIe in DMSO-d6 consid-
erably differed from each other. The spectra of IVa–
IVc were consistent with the existence of these com-
pounds in solution as two Z-isomeric ketoenehydrazine
tautomers A and B and two ketohydrazone tautomers
C and D, structure A prevailing (cf. the above data for
acids IIIa–IIId). Enehydrazines A (Z,E) and B (Z,Z)
are characterized by the position of vinylic proton
singlet at δ 5.36–5.40 and 5.42–5.49 ppm and of NH
singlet at δ 11.92–12.13 and 12.01–12.16 ppm, respec-
tively. The NH signal is displaced downfield as a result
of intramolecular hydrogen bonding with the C4=O
carbonyl oxygen atom. The fraction of structure A is
31–36%, and the fraction of B is 20–23%. Hydrazones
C (E) and D (Z) each displayed a singlet from the C3H2
methylene protons at δ 3.94–3.98 and 3.98–4.0 ppm,
respectively. The fraction of C is 27–30%, and the
fraction of D is 14–19%.
purity of the isolated compounds was checked, and
the progress of reactions was monitored, by TLC on
Silufol UV-254 plates using diethyl ether–benzene–
acetone (10:9:1) as eluent; spots were detected by
treatment with iodine vapor.
4-Aryl-2-{2-[aryl(phenyl)methylidene]hydra-
zino}-4-oxobut-2-enoic acids IIIa–IIIe (general
procedure). A solution of 0.001 mol of hydrazone IIa
or IIb in 20 ml of chloroform was added to a solution
of 0.01 mol of 4-aryl-2-hydroxy-4-oxobut-2-enoic acid
Ia–Id in 20 ml of ethanol. The mixture was kept for
24 h at 20–25°C and cooled to 0°C, and the precipitate
was filtered off and recrystallized from appropriate
solvent.
2-{2-[(4-Methoxyphenyl)(phenyl)methylidene]-
hydrazino}-4-oxo-4-phenylbut-2-enoic acid (IIIa).
Yield 3.41 g (88%), orange crystals, mp 165–167°C
(from EtOH–CHCl3). IR spectrum, ν, cm–1: 3226 br
(NH), 1602 sh (COO, C=O, C=N). 1H NMR spectrum,
δ, ppm: A (43.5%): 3.83 s (3H, OMe), 6.12 s (1H,
CH), 7.65 m (14H, Harom), 12.75 s (1H, NH); B
(35.5%): 3.95 s (3H, OMe), 6.18 s (1H, CH), 7.65 m
(14H, Harom), 12.84 s (1H, NH); C (15%); 3.88 s (3H,
OMe), 4.49 s (2H, CH2), 7.65 m (14H, Harom); D (6%):
3.91 s (3H, OMe), 4.58 s (2H, CH2), 7.65 m (14H,
H
arom). Found, %: C 71.40; H 4.94; N 7.22.
C23H19N2O4. Calculated, %: C 71.31; H 4.94; N 7.23.
4-(4-Methoxyphenyl)-2-{2-[(4-methoxyphenyl)-
(phenyl)methylidene]hydrazino}-4-oxobut-2-enoic
acid (IIIb). Yield 3.53 g (82%), orange crystals,
mp 182–183°C (from EtOH–CHCl3). IR spectrum, ν,
cm–1: 3257 br (NH), 1605 sh (COO, C=O, C=N).
1H NMR spectrum, δ, ppm: A (45%): 3.80 s (3H,
OMe), 3.83 s (3H, OMe), 6.09 s (1H, CH), 7.65 m
(13H, Harom), 12.64 s (1H, NH); B (30%): 3.78 s (3H,
OMe), 3.90 s (3H, OMe), 6.04 s (1H, CH), 7.65 m
(13H, Harom), 12.64 s (1H, NH); C (23%): 3.81 s (3H,
OMe), 3.86 s (3H, OMe), 4.39 s (2H, CH2), 7.65 m
(13H, Harom); D (2%): 3.77 s (3H, OMe), 3.88 s (3H,
OMe), 4.45 s (2H, CH2), 7.65 m (13H, Harom). Found,
%: C 69.72; H 5.16; N 6.52. C25H22N2O5. Calculated,
%: C 69.76; H 5.15; N 6.51.
A different pattern is observed in the 1H NMR spec-
tra of compounds VId and VIe. Apart from signals
belonging to the Z isomer (structure A, 80 and 16%,
respectively; δNH 12.11 and 13.32 ppm, δ3-H 5.5 and
5.92 ppm), the spectra contained signals assignable to
β-ketohydrazone tautomer C, δ 3.98 and 4.01 ppm
(C3H2), respectively. No isomer with E configuration
of the C2=C3 bond was detected in the 1H NMR spectra
of compounds VIa–VIe.
2-{2-[(4-Methoxyphenyl)(phenyl)methylidene]-
hydrazino}-4-(4-methylphenyl)-4-oxobut-2-enoic
acid (IIIc). Yield 3.36 g (81%), orange crystals,
mp 157–158°C (from EtOH–CHCl3). IR spectrum, ν,
cm–1: 3251 br (NH), 1599 sh (COO, C=O, C=N).
1H NMR spectrum, δ, ppm: A (45%): 2.38 s (3H, Me),
3.82 s (3H, OMe), 6.02 s (1H, CH), 7.65 m (13H,
EXPERIMENTAL
The IR spectra were measured on an FSM-1201
spectrometer from samples dispersed in mineral oil.
The H NMR spectra were recorded on Bruker DRX-
500 (500.13 MHz) and Varian Mercury Plus-300 in-
struments (300.05 MHz) using DMSO-d6 as solvent
and hexamethyldisiloxane as internal reference. The
1
H
arom), 12.73 s (1H, NH); B (30%): 2.37 s (3H, Me),
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 47 No. 1 2011

CHEMISTRY OF IMINOFURANS: VI.
113
3.94 s (3H, OMe), 6.14 s (1H, CH), 7.65 m (13H,
Harom), 12.82 s (1H, NH); C (23%): 2.41 s (3H, Me),
3.87 s (3H, OMe), 4.54 s (2H, CH2), 7.65 m (13H,
7.70 m (13H, Harom), 13.85 s (1H, NH); C (68%):
4.48 s (2H, CH2), 7.70 m (13H, Harom). Found, %:
C 75.03; H 4.41; N 7.58. C23H16N2O3. Calculated, %:
C 74.99; H 4.38; N 7.60.
H
arom); D (2%): 2.40 s (3H, Me), 3.90 s (3H, OMe),
4.52 s (2H, CH2), 7.65 m (13H, Harom). Found, %:
C 72.42; H 5.36; N 6.72. C25H22N2O5. Calculated, %:
C 72.45; H 5.35; N 6.76.
2-[2-(9H-Fluoren-9-ylidene)hydrazino]-4-
(4-methylphenyl)-4-oxobut-2-enoic acid (IVb). Yield
3.1 g (81%), red crystals, mp 187–188°C (from
CHCl3). IR spectrum, ν, cm–1: 3304 br (NH), 1566 sh
(COO, C=O, C=N). H NMR spectrum, δ, ppm
(CDCl3): A (18%): 2.44 s (3H, Me), 7.60 s (13H,
4-(4-Chlorophenyl)-2-{2-[(4-methoxyphenyl)-
(phenyl)methylidene]hydrazino}-4-oxobut-2-enoic
acid (IIId). Yield 3.76 g (87%), orange crystals,
mp 134–135°C (from EtOH–CHCl3). IR spectrum, ν,
cm–1: 3258 br (NH), 1605 sh (COO, C=O, C=N).
1H NMR spectrum, δ, ppm: A (35%): 3.83 s (3H,
OMe), 6.14 s (1H, CH), 7.65 m (13H, Harom), 12.76 s
(1H, NH); B (28%): 3.95 s (3H, OMe), 6.19 s (1H,
CH), 7.65 m (13H, Harom), 12.82 s (1H, NH); C (20%):
3.85 s (3H, OMe), 4.47 s (2H, CH2), 7.65 m (13H,
1
H
arom), 14.38 s (1H, NH); E (82%): 2.48 s (3H, Me),
7.60 s (13H, Harom), 10.88 s (1H, NH). Found, %:
C 75.26; H 4.75; N 7.31. C24H18N2O3. Calculated, %:
C 75.38; H 4.74; N 7.33.
2-[2-(9H-Fluoren-9-ylidene)hydrazino]-
4-(4-methoxyphenyl)-4-oxobut-2-enoic acid (IVc).
Yield 3.86 g (94%), red crystals, mp 194–195°C (from
toluene). IR spectrum, ν, cm–1: 3312 br (NH), 1568 sh
Harom); D (17%): 3.91 s (3H, OMe), 4.60 s (2H, CH2),
1
7.65 m (13H, Harom). Found, %: C 72.27; H 4.36;
Cl 8.18; N 6.42. C24H19ClN2O4. Calculated, %:
C 66.29; H 4.40; Cl 8.15; N 6.44.
(COO, C=O, C=N). H NMR spectrum, δ, ppm: A
(29%): 3.87 s (3H, OMe), 6.51 s (1H, CH), 7.60 m
(12H, Harom), 13.84 s (1H, NH); C (68 %): 3.81 s (3H,
OMe), 4.42 s (2H, CH2), 7.60 m (12H, Harom). Found,
%: C 71.60; H 4.56; N 7.05. C23H18N2O4. Calculated,
%: C 71.56; H 4.55; N 7.03.
4-(4-Methoxyphenyl)-2-{2-[(4-methylphenyl)-
(phenyl)methylidene]hydrazino}-4-oxobut-2-enoic
acid (IIIe). Yield 2.9 g (88%), orange crystals,
mp 151–152°C (from toluene). IR spectrum, ν, cm–1:
4-(4-Chlorophenyl)-2-[2-(9H-fluoren-9-ylidene)-
hydrazino]-4-oxobut-2-enoic acid (IVd). Yield 3.62 g
(90%), red crystals, mp 172–173°C (from toluene). IR
spectrum, ν, cm–1: 3302 br (NH), 1564 sh (COO, C=O,
1
3237 br (NH), 1604 sh (COO, C=O, C=N). H NMR
spectrum, δ, ppm: A (36%): 2.36 s (3H, Me), 3.84 s
(3H, OMe), 6.12 s (1H, CH), 7.65 m (13H, Harom),
12.69 s (1H, NH); B (35%): 2.52 s (3H, Me), 3.91 s
(3H, OMe), 6.15 s (1H, CH), 7.65 m (13H, Harom),
12.73 s (1H, NH); C (25%): 2.32 s (3H, Me), 3.87 s
(3H, OMe), 4.43 s (2H, CH2), 7.65 m (13H, Harom);
D (4%): 2.42 s (3H, Me), 3.89 s (3H, OMe), 4.52 s
(2H, CH2), 7.65 m (13H, Harom). Found, %: C 72.43;
H 5.35; N 6.74. C25H22N2O5. Calculated, %: C 72.45;
H 5.35; N 6.76.
1
C=N). H NMR spectrum, δ, ppm: A (47%): 6.52 s
(1H, CH), 7.6 m (12H, Harom), 13.78 s (1H, NH);
C (53%): 4.43 s (2H, CH2), 7.60 m (12H, Harom).
1H NMR spectrum in CDCl3, δ, ppm: A (55%): 7.60 s
(13H, CH, Harom), 14.26 s (1H, NH); E (45%): 7.60 s
(13H, CH, Harom), 10.895 s (1H, NH). Found, %:
C 68.55; H 3.76; Cl 8.84; N 6.94. C23H15ClN2O3. Cal-
culated, %: C 68.58; H 3.75; Cl 8.80; N 6.95.
4-Aryl-2-[2-(9H-fluoren-9-ylidene)hydrazino]-
4-oxobut-2-enoic acids IVa–IVe (general procedure).
A solution of 0.01 mol of fluorenone hydrazone in
20 ml of ethanol was added to a solution of 0.01 mol
of 4-aryl-2-hydroxy-4-oxobut-2-enoic acid Ia–Ie in
20 ml of ethanol, and the mixture was kept for 24 h at
20–25°C. The mixture was cooled to 0°C, and the
precipitate was filtered off and recrystallized from
toluene.
4-(4-Ethoxyphenyl)-2-[2-(9H-fluoren-9-ylidene)-
hydrazino]-4-oxobut-2-enoic acid (IVe). Yield 3.79 g
(92%), red crystals, mp 201–202°C (from toluene). IR
spectrum, ν, cm–1: 3308 br (NH), 1566 sh (COO, C=O,
1
C=N). H NMR spectrum, δ, ppm: A (36%): 1.36 t
(3H, Me), 4.14 q (3H, OCH2), 6.51 s (1H, CH), 7.60 m
(12H, Harom), 13.85 s (1H, NH); C (64%): 1.32 t (3H,
Me), 4.08 q (3H, OCH2), 4.41 s (2H, CH2), 7.60 m
(12H, Harom). Found, %: C 72.82; H 4.86; N 6.74.
C25H20N2O4. Calculated, %: C 72.80; H 4.89; N 6.79.
2-[2-(9H-Fluoren-9-ylidene)hydrazino]-4-oxo-4-
phenylbut-2-enoic acid (IVa). Yield 3.46 g (94%), red
crystals, mp 190–190.5°C (from toluene). IR spectrum,
ν, cm–1: 3314 br (NH), 1568 sh (COO, C=O, C=N).
1H NMR spectrum, δ, ppm: A (32%): 6.54 s (1H, CH),
2-{2-[Aryl(phenyl)methylidene]hydrazino}-5,5-
dimethyl-4-oxohex-2-enoic acids VIa–VId and
2-[2-(9H-fluoren-9-ylidene)hydrazino]-5,5-dimeth-
yl-4-oxohex-2-enoic acid (VIe) (general procedure).
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 47 No. 1 2011

KOMAROVA et al.
114
A solution of 0.01 mol of hydrazone IIa–IIe in 20 ml
of ethanol or toluene was added to a solution of 1.72 g
(0.01 mol) of 2-hydroxy-5,5-dimethyl-4-oxohex-2-en-
oic acid (V) in 15 ml of ethanol. The mixture was
heated for 3–4 min and kept for 24 h at 20–25°C, and
the precipitate was filtered off and recrystallized from
toluene or ethanol.
2-{2-[(4-Bromophenyl)(phenyl)methylidene]hy-
drazino}-5,5-dimethyl-4-oxohex-2-enoic acid (VId).
Yield 1.71 g (59%), orange crystals, mp 150–151°C
(from toluene). IR spectrum, ν, cm–1: 1745 (COOH);
1
1598, 1577 (C=C, C=O, C=N). H NMR spectrum, δ,
ppm: A (36%): 0.98 s (9H, CMe3), 5.36 s (1H, CH),
7.50 m (9H, Harom), 12.13 s (1H, NH); B (23%): 1.04 s
(9H, CMe3), 5.49 s (1H, CH), 7.50 m (9H, Harom),
12.16 s (1H, NH); C (27%): 1.0 s (9H, CMe3), 3.98 s
(2H, CH2), 7.40 m (9H, Harom); D (14%): 1.05 s (9H,
CMe3), 4.0 s (2H, CH2), 7.40 m (9H, Harom). Found, %:
C 58.73; H 4.91; Br 18.65; N 6.51. C21H21BrN2O3.
Calculated, %: C 58.75; H 4.93; Br 18.61; N 6.53.
2-[2-(Diphenylmethylidene)hydrazino]-5,5-di-
methyl-4-oxohex-2-enoic acid (VIa). Yield 3.01 g
(86%), yellow crystals, mp 151–152°C (from ethanol).
IR spectrum, ν, cm–1: 1744 (COOH); 1597, 1577
1
(C=C, C=O, C=N). H NMR spectrum, δ, ppm:
A (80%): 0.99 s (9H, CMe3) 5.50 s (1H, CH), 7.50 m
(10H, Harom), 12.11 s (1H, NH), 13.97 br.s (1H,
COOH); C (20%): 1.05 s (9H, CMe3) 3.98 s (2H,
CH2), 7.50 m (10H, Harom), 13.97 br.s (1H, COOH).
Found, %: C 71.95; H 6.28; N 7.94. C21H22N2O3. Cal-
culated, %: C 71.98; H 6.33; N 7.99.
2-[2-(9H-Fluoren-9-ylidene)hydrazino]-5,5-di-
methyl-4-oxohex-2-enoic acid (VIe). Yield 2.54 g
(73%), orange crystals, mp 174–175°C (from toluene).
IR spectrum, ν, cm–1: 3318 (NH); 1723 (COOH);
1
1602, 1576 (C=C, C=O, C=N). H NMR spectrum, δ,
ppm: A (16%): 1.19 s (9H, CMe3), 5.92 s (1H, CH),
7.70 m (9H, Harom), 13.32 s (1H, NH), 13.50 br.s
(COOH); C (86%): 1.02 s (9H, CMe3), 4.01 s (2H,
CH2), 7.70 m (4H, Harom), 13.50 br.s (COOH). Found,
%: C 72.43; H 5.81; N 8.01. C21H20N2O3. Calculated,
%: C 72.40; H 5.79; N 8.04.
5,5-Dimethyl-2-{2-[(4-methylphenyl)(phenyl)-
methylidene]hydrazino}-4-oxohex-2-enoic acid
(VIb). Yield 2.73 g (75%), orange crystals, mp 136–
137°C (from ethanol). IR spectrum, ν, cm–1: 1743
1
(COOH); 1603, 1582 (C=C, C=O, C=N). H NMR
spectrum, δ, ppm: A (31%): 1.02 s (9H, CMe3), 2.37 s
(3H, Me), 5.37 s (1H, CH), 7.40 m (9H, Harom), 11.92 s
(1H, NH); B (20%): 1.14 s (9H, CMe3), 2.35 s (3H,
Me), 5.43 s (1H, CH), 7.40 m (9H, Harom), 12.03 s (1H,
NH); C (30%): 0.98 s (9H, CMe3), 2.33 s (3H, Me),
3.95 s (2H, CH2), 7.40 m (9H, Harom); D (19%): 1.06 s
(9H, CMe3), 2.43 s (3H, Me), 3.99 s (2H, CH2), 7.40 m
(9H, Harom). Found, %: C 72.51; H 6.62; N 7.68.
C22H24N2O3. Calculated, %: C 72.50; H 6.64; N 7.69.
This study was performed under financial support
by the Russian Foundation for Basic Research (project
no. 08-03-00488).
REFERENCES
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RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 47 No. 1 2011