(Z)-1,4-diphenyl-2-phenylamino-2-butene-1,4-dione: Synthesis and mechanizm of formation

Article abstract of DOI:10.1023/B:RUJO.0000043716.91339.ea

Heating of 1-phenyl-2-(phenylamino)ethanone in a water-ethanol solution of potassium carbonate gave rise to (Z)-1,4-diphenyl-2-phenylamino-2-butene-1,4- dione; it formed most probably by reaction of the initial aminoketone with its oxidation product, 1-ph

Full text of DOI:10.1023/B:RUJO.0000043716.91339.ea

Russian Journal of Organic Chemistry, Vol. 40, No. 5, 2004, pp. 693 -698. Translated from Zhurnal Organicheskoi Khimii, Vol. 40, No. 5, 2004,
pp. 726-731.
Original Russian Text Copyright Ó 2004 by Akimova, Trofimenko, Verbitskii, Gerasimenko.
.
(Z)-1,4-Diphenyl-2-phenylamino-2-butene-1,4-dione:
Synthesis and Mechanizm of Formation
1
1
1
2
T.I. Akimova, N.N. Trofimenko, G.A. Verbitskii, andA.V. Gerasimenko
1
Far-Eastern State University, Vladivostok, 690950 Russia
e-mail: tiakim@chem.dvgu.ru
Institute of Chemistry, Far-Eastern Division, Russian Academy of Sciences, Vladivostok, Russia
2
Received September 27, 2003
Abstract—Heating of 1-phenyl-2-(phenylamino)ethanone in a water-ethanol solution of potassium carbonate gave
rise to (Z)-1,4-diphenyl-2-phenylamino-2-butene-1,4-dione; it formed most probably by reaction of the initial
aminoketone with its oxidation product, 1-phenyl-2-(phenylimino)ethanone.
In extension of our research in the field of diketones
chemistry we started investigation of their heteroanalogs,
formations solely of aminoketone III and that chlorocyclo-
hexanone (II) was not involved into the reaction. We
proved this assumption by a control run without compound
II, where product IV was obtained in the same yield.
3
-aza-1,5-diketones, that open the way to heterocycles
with two heteroatoms. The main preparation method for
-aza-1,5-diketones consists in reaction of a-haloketones
3
The structure of diketone IV was confirmed by IR,
Í and Ñ spectra, by GC-MS method and X-ray diffrac-
with a-aminoketones [1]. Inasmuch as 2-[(2-oxo-2-phen-
ylethyl)(phenyl)amino]cyclohexanone (I) was not de-
scribed in the literature we attempted to prepare the com-
pound by this procedure. To this end 2-chlorocyclo-
hexanone (II) and 1-phenyl-2-(phenylamino)ethanone
1
13
tion analysis. In the IR spectrum absorption bands were
present belonging to vibrations of benzene ring (1605,
–1
–1
1
506 cm ) and conjugated carbonyl group (1664 cm ).
In contrast to [2] we did not observe stretching vibrations
(III) were boiled in a saturated water-ethanol solution of
of the N–H bond in the high-frequency region at
potassium carbonate. As a result a bright yellow crystal-
line compound was obtained in a 64% yield; the sub-
stance turned out to be (Z)-1,4-diphenyl-2-phenyl-amino-
–1
3
400 cm because of a strong hydrogen bond (for refer-
ence, the N–H bond in compound III appeared in the
–
1
spectrum as a strong absorption band at 3370 cm ). The
same result was obtained in recording the IR spectrum in
2-butene-1,4-dione (IV). This procedure for preparation
of diketone IV was not published before. The known
methods afford lower yields of the reaction product [2, 3]
or the reagents used are less accessible [4, 5]. We pre-
sumed that the compound obtained resulted from trans-
CHCl at 5-fold dilution. The X-ray diffraction study re-
3
vealed the stereochemistry of compound IV (see figure
and table): the compound had the Z-configuration with a
strong hydrogen bond Ñ=ÎꢀHN.
The unexpected conversion of aminoketone III into
unsaturated 1,4-diketone IV attracted our interest to the
reaction mechanism. For this purpose we used the meth-
ods of GC and HPLC mass-spectrometry.
3
K
3K
1
1+
3
K
3K
2
In the study of formation mechanism of compound IV
we proceeded from the facts listed below. Oxygen sig-
nificantly affected the reaction rate: the process hardly
occurred in an argon atmosphere. Boiling of compound
III under argon for 5.5 h provided less than 3% of
diketone IV, and ~70% of unreacted initial aminoketone
III remained in the reaction mixture, whereas in air, all
other factors being the same, the reaction within 1.5 h
afforded 64% yield of compound IV. Besides diketone
2
2
,
,,,
2
&
O
3K
ꢀ
3
K
1+
2
2
,9
3
K
,
,
1070-4280/04/4005-0693Ó2004 MAIK “Nauka/Interperiodica”

694
AKIMOVAet al.
nish diketone IV. We tested the possibility of the process
taking the pathway a by preparation of phenylglyoxal (V)
6] and bringing it into reaction with aminoketone III
[
through boiling in water-ethanol solution of potassium
carbonate in an argon atmosphere. As a result we recov-
ered compound III (58%) and obtained diketone IV in
~6% yield. Obviously this yield was at the same level as
at boiling aminoketone III under inert atmosphere, and
no additional condensation with phenylglyoxal (V) oc-
curred. Therefore the assumption of diketone IV forma-
tion along path à is wrong.
According to the second assumption the oxygen initi-
ated formation of a radical (B) that on recombination pro-
vided dimer VI; the latter by aniline eliminating are
diketone IV (path b). Preparation of compound VI in 30%
yield by heating aminoketone III at reflux in ethanol in
the presence of piperidine was described in [7]. It was
reported that dimer VI formed only if the reaction mix-
ture was kept in air for 12 h and failed to form under
argon atmosphere. No diketone IV was revealed in the
reaction mixture in this reaction. We reproduced the pro-
cess described in [7] and on isolating dimer VI we sub-
jected it to boiling in a water-ethanol solution of potas-
sium carbonate under argon. Thus we obtained diketone
IV in 77% yield. This result suggests that compound VI
is an intermediate on the route aminoketone III ’diketone
IV. It also proved that in reaction carried out along pro-
cedure [7] in air compound VI could not be isolated, and
the final product was diketone IV. We also established
that preparation of dimer VI did not require boiling, and it
was obtained in 40% yield by keeping aminoketone III in
ethanol solution in the presence of catalytic amounts of
Structure of (Z)-1,4-diphenyl-2-phenyl-amino-2-butene-1,4-
dione (IV).
IV one of the main products in the reaction mixture was
aniline.
On the strength of this evidence we investigated three
possible pathways of the process:
We assumed first that aniline arose in the first stage
of the process and resulted from the hydrolysis of com-
pound III (path a).Alongside aniline also ketoalcohol (A)
formed in the reaction further oxidized by oxygen to
phenylglyoxal (V); the latter enters into condensation with
aminoketone III under the action of catalyst base to fur-
2
+
+
2
2
ꢀ
Dꢁꢂ+ 2
K1+
2
,,,
,
9
3
3
K
2
3K
$
&
9
3
K
2
3
K
+
1
3K
3K
1+
ꢀ
Eꢁꢂ2
+
1
+
,9
+
&
3K
1+
3K1+
3
K
2
2
3K
%
3
K
2
9,
3K
,,,
1
,
,,
ꢀFꢁꢂ2
9,
,9
3K1+
3K
2
9,,
RUSSIAN JOURNALOF ORGANIC CHEMISTRY Vol. 40 No. 5 2004

(Z)-1,4-DIPHENYL-2-PHENYLAMINO-2-BUTENE-1,4-DIONE
695
Main bond lengths (d) and bond angles (w) in diketone IV
piperidine in air for 15 h; this process did not occur under
inert atmosphere.
molecule
RQGꢀ
%
Gꢁꢀcꢀ
$QJOHꢀ
ZꢁꢀGHJꢀ
If the oxygen was necessary only to initiate radical
2
2
1
1
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ꢂꢃꢄꢄꢄꢊꢇꢂꢈꢉꢀ
ꢂꢃꢋꢅꢄꢆꢇꢂꢌꢉꢀ
ꢂꢃꢅꢂꢂꢍꢇꢂꢌꢉꢀ
ꢂꢃꢋꢈꢎꢂꢇꢂꢊꢉꢀ
ꢂꢃꢎꢂꢋꢅꢇꢂꢊꢉꢀ
ꢂꢃꢅꢋꢊꢅꢇꢂꢊꢉꢀ
ꢂꢃꢅꢊꢎꢆꢇꢂꢊꢉꢀ
ꢂꢃꢅꢌꢅꢂꢇꢂꢊꢉꢀ
ꢂꢃꢋꢊꢍꢄꢇꢂꢆꢉꢀ
ꢂꢃꢋꢊꢅꢎꢇꢂꢆꢉꢀ
ꢂꢃꢋꢊꢎꢇꢄꢉꢀ
& 1 & ꢀ
1 & & ꢀ
1 & & ꢀ
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2 & & ꢀ
2 & & ꢀ
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2 & & ꢀ
2 & & ꢀ
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& & & ꢀ ꢂꢂꢆꢃꢄꢆꢇꢂꢋꢉꢀ
& & 1 ꢀ
& & 1 ꢀ
& & & ꢀ ꢂꢄꢍꢃꢍꢆꢇꢂꢅꢉꢀ
& & & ꢀ ꢂꢄꢍꢃꢍꢄꢇꢂꢎꢉꢀ
& & & ꢀ ꢂꢂꢆꢃꢌꢄꢇꢂꢎꢉꢀ
& & & ꢀ ꢂꢄꢍꢃꢊꢂꢇꢂꢎꢉꢀ
& & & ꢀ ꢂꢄꢍꢃꢍꢅꢇꢂꢅꢉꢀ
& & & ꢀ ꢂꢂꢊꢃꢄꢍꢇꢂꢋꢉꢀ
ꢂꢄꢈꢃꢌꢋꢇꢂꢂꢉꢀ
ꢂꢄꢋꢃꢎꢂꢇꢂꢋꢉꢀ
ꢂꢂꢌꢃꢅꢈꢇꢂꢄꢉꢀ
ꢂꢂꢊꢃꢍꢋꢇꢂꢋꢉꢀ
ꢂꢄꢋꢃꢋꢆꢇꢂꢋꢉꢀ
ꢂꢄꢂꢃꢋꢅꢇꢂꢋꢉꢀ
ꢂꢂꢊꢃꢊꢂꢇꢂꢄꢉꢀ
ꢂꢂꢆꢃꢊꢋꢇꢂꢄꢉꢀ
ꢂꢄꢂꢃꢌꢈꢇꢂꢄꢉꢀ
ꢂꢂꢈꢃꢈꢌꢇꢂꢄꢉꢀ
ꢂꢄꢂꢃꢎꢋꢇꢂꢄꢉꢀ
(
B) formation, then it would be possible to obtain diketone
IV under inert atmosphere in the presence of the other
radical initiators, like 2,2'-azobisisobutyronitrile (AIBN),
hydrogen peroxide, potassium persulfate. Therewith the
absence of a basic catalyst should not affect the forma-
tion of diketone IV. Therefore we investigated the reac-
tion mixtures arising at boiling aminoketone III in the
water-ethanol solution of potassium carbonate under ar-
gon in the presence of the mentioned initiators. It turned
out that the yield of diketone IV in the presence of AIBN
was similar to that in the control run performed in an inert
atmosphere (less than 3%). In the presence of hydrogen
peroxide and potassium persulfate the yield was higher
and attained 35–47%. In the absence of potassium car-
bonate or piperidine the reaction did not occur even in air.
This result invalidates the assumption of the intermediate
generation of radical (B) and of the radical mechanism
of dimer VI formation. As showed further studies, the
considerable amounts of diketone VI arising in the pres-
ence of hydrogen peroxide or potassium persulfate origi-
nated from the oxidative properties of the latter favoring
formation from aminoketone III of Schiff base VII.
±& ꢀ
±& ꢀ
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±& ꢀ
±& ꢀ
& ±& ꢀ
ꢂꢃꢋꢌꢊꢇꢄꢉꢀ
ꢂꢂꢆꢃꢎꢂꢇꢂꢄꢉꢀ
ꢂꢄꢂꢃꢂꢌꢇꢂꢄꢉꢀ
&
&
&
&
&
±& ꢀ
±&
±&
±& ꢀ
±& ꢀ
ꢂꢃꢋꢈꢎꢇꢄꢉꢀ
ꢂꢃꢋꢌꢅꢇꢄꢉꢀ
ꢂꢃꢋꢌꢊꢎꢇꢂꢆꢉꢀ
ꢂꢃꢋꢊꢎꢍꢇꢂꢊꢉꢀ
ꢂꢃꢋꢊꢅꢇꢄꢉꢀ
ꢂꢃꢋꢊꢄꢇꢄꢉꢀ
ꢂꢃꢋꢌꢄꢇꢄꢉꢀ
ꢂꢃꢋꢈꢊꢇꢄꢉꢀ
ꢂꢃꢋꢊꢅꢅꢇꢂꢊꢉꢀ
ꢂꢃꢋꢊꢌꢂꢇꢂꢊꢉꢀ
ꢂꢃꢋꢌꢈꢍꢇꢂꢆꢉꢀ
ꢂꢃꢋꢌꢈꢇꢄꢉꢀ
ꢂꢃꢋꢈꢈꢇꢄꢉꢀ
ꢂꢃꢋꢊꢎꢆꢇꢂꢆꢉꢀ
& ±& ꢀ
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&
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ꢀ
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ꢂꢄꢄꢃꢆꢅꢇꢂꢄꢉꢀ
ꢂꢂꢊꢃꢊꢋꢇꢂꢋꢉꢀ
& & & ꢀ ꢂꢄꢂꢃꢄꢌꢇꢂꢅꢉꢀ
& & & ꢀ ꢂꢂꢆꢃꢋꢅꢇꢂꢎꢉꢀ
& & & ꢀ ꢂꢂꢆꢃꢈꢆꢇꢂꢎꢉꢀ
& & & ꢀ ꢂꢄꢍꢃꢎꢈꢇꢂꢅꢉꢀ
& & & ꢀ ꢂꢄꢍꢃꢆꢋꢇꢂꢎꢉꢀ
& & & ꢀ ꢂꢂꢆꢃꢅꢅꢇꢂꢄꢉꢀ
±& ꢀ
We assumed in the study of the third path (c) leading
to diketone IV that the oxygen oxidized aminoketone III
giving Schiff base VII which further under catalysis with
a base enters into condensation with aminoketone III yield-
ing dimer VI and subsequently diketone IV. To test this
assumption we attempted to prepare anil VII by proce-
dure [8], but it proved that the target reaction product
having the same melting point as reported did not corre-
spond to Schiff base VII by IR and mass spectrum (double
mass value). The required compound we prepared by
mixing glyoxal V with aniline in ethanol solution at room
temperature. Compound VII is yellow oily substance very
unstable at storage. The freshly prepared reaction prod-
uct VII that was an individual compound according to
GC-MS data we brought into reaction with aminoketone
III under argon, and succeeded to isolate from the reac-
tion mixture diketone IV in a 75% yield. The reaction
carried out at room temperature afforded dimer VI.
&
&
& & ꢀ
& & ꢀ
ꢂꢄꢄꢃꢂꢆꢇꢂꢄꢉꢀ
ꢂꢂꢊꢃꢋꢎꢇꢂꢄꢉꢀ
& & & ꢀ ꢂꢄꢍꢃꢋꢎꢇꢂꢅꢉꢀ
&
&
&
&
& & ꢀ ꢂꢂꢆꢃꢊꢄꢇꢂꢅꢉꢀ
& & ꢀ ꢂꢄꢍꢃꢋꢎꢇꢂꢅꢉꢀ
& & ꢀ ꢂꢄꢍꢃꢅꢋꢇꢂꢎꢉꢀ
& & ꢀ ꢂꢂꢆꢃꢎꢆꢇꢂꢅꢉꢀ
ꢀ
EXPERIMENTAL
IR spectra were recorded on spectrophotometer
1
13
Perkin Elmer Spectrum BX-II. H and C NMR spec-
tra were registered on spectrometer Bruker AC-250 (op-
erating frequencies 250 and 62.9 MHz respectively) from
solutions in CDCl internal reference TMS.
3
,
HPLC-mass spectra were measured on Agilent 1100
Series LC/MSD (“Hewlett-Packard”, USA) instrument
equipped with a column LiChroCART CN (4 ´250 mm,
sorbent particles 5 mm) at thermostat temperature 40°C
in linear gradient elution mode (30–70% aqueous aceto-
nitrile) at a rate 2% per min. Elution rate 0.5 ml/min, de-
tection by electron absorption spectra in the range 200–
The results obtained suggest a conclusion that the most
probable route of diketone IV formation from aminoketone
III is path c. The latter adds across the C=N bond of
compound VII affording dimer VI that at heating is con-
verted into diketone IV.Aminoketone III in this reaction
acts as a compound with an active methylene group.
700 nm, ionization by electrospray at atmospheric pres-
RUSSIAN JOURNALOF ORGANIC CHEMISTRY Vol. 40 No. 5 2004

696
AKIMOVAet al.
sure, ionizing voltage 70 V, ionizing chamber voltage
kV, the gas-dryer flow (nitrogen) 6 l/min, the pressure
of spraying gas (nitrogen) 50 kg cm , the range of regis-
tered mass m/z 150–700. GC-MS spectra were taken on
Agilent GC/MS 5973N (“Hewlett-Packard”, USA) in-
strument, column HP5-MS, carrier gas helium, flow rate
(N–H), 1693 (conjug. C=O), 1603, 1513 (Ph), 1579 (bend-
ing vibrations N–H), 1222, 1264 (C–N). Mass spectrum,
4
-
2
+
m/z (I , %): 211 [M] (9.4), 106 (100), 77 (20.6).
rel
(
Z)-1,4-Diphenyl-2-phenylamino-2-butene-1,4-
dione (IV). (a) A mixture of 0.5 g (2.37 mmol) of
aminoketone III, 1.5 g of K CO 1 ml of water, and 5 ml
2
3,
1
ml/min, mass scanning in the range 50–500 m/z, de-
of ethanol was heated at reflux while stirring till complete
consumption of aminoketone III (3.5 h; TLC monitor-
ing). The mixture was cooled, diluted with water to com-
plete dissolution of potassium carbonate, and the or-
ganic layer was separated. On cooling the solution yel-
low crystals precipitated of diketone IV, yield 0.25 g
(64%). On recrystallization from ethanol mp. 126–127°C
tector temperature 230°C, oven temperature pro-
grammed as follows: 100°C (1 min), 20 deg/min; 250°C;
2
1.5 min.
Compounds III, IV, and VII were studied by GC-MS
method, and compound VI that decomposed under GC-
MS conditions was studied by HPLC-MS procedure.
(
publ.: mp 124–128°C [2–5]). IR spectrum (KBr), n,
The X-ray diffraction study of compound IV was per-
formed on diffractometer SMART-1000 CCD (Bruker).
Crystal of compound IV bright yellow prism, crystal habit
–
1
cm : 1664 (conjug. C=O), 1605, 1506 (Ph), 1575, 1552
(
spectrum (CDCl ), d, ppm: 6.12 s (1H, vinyl proton),
6
tons), 12.5 s (1H, NH), the signal disappeared on add-
ing CD OD. CNMR spectrum (CDCl ), d, ppm: 190.9,
192.16 (2C=O), 121.7, 125.04, 127.4, 128.5, 128.7, 129.2,
129.7, 131.9, 134.3 (arom =CH), 134.6, 138.6, 138.9,
1
bending vibrations N–H), 1241, 1283 (C–N). H NMR
0
.30´0.22´0.04 mm; at 293 (2) K a 5.9697(18), b 13.603
3
°
°3
.96–8.00 m (four groups of multiplets, aromatic pro-
(4), c 21.260 (6) A, b 94.077 (7)°, V 1772.1 (9) A , r
calc
3
–1
1
.263 mg/m , m 0.081 mm , F 688, space group P2 /n,
1
1
3
Z 4. The structure was refined by full-matrix least-squares
3
3
2
method along F . Number of refined parameters 227.
2
2
GooF 0.746, R (F ) [F > 2s], R 0.0431, wR 0.0890, R
1
2
1
%
56.7 (arom =C–), 95.0 (CH=CNH). GC-MS, m/z (I ,
using all reflections R 0.1718, wR 0.1193, extinction fac-
rel
1
2
+
): 327 [M] (12), 222 (100), 105 (53), 77 (49). Reten-
tor 0.0057(5), residual electron density (min/max.) –0.156/
–
°–3
tion time 22.20 min.
0
.151 e/A . From 12550 measured reflections 4814 were
independent (R 0.0676), 1548 had 2s (I). The range of
(b) The same mixture as used in the a run was boiled
with passing air through the reaction mixture. The reac-
tion completed within 1.5 h, yield of diketone IV 64%.
int
data collection q 1.78–30.03°. The range of reflection
indices 8 £ h £ 8, –18 £ k £ 18, –25 £ I £ 15. The struc-
ture was solved by the direct method and refined by the
least-squares method in anisotropic approximation for
nonhydrogen atoms. Collection and treating of the ex-
perimental data, refinement of parameters of the unit cell
was performed by software SMART and SAINT Plus.
All calculations in solving and refining of the structure
were done by SHELXTL/PC programs. The X-ray
abextinction in the sample was not taken into consider-
ation.
(
c) The same mixture as used in the a run was boiled
with passing argon through the reaction mixture. After
.5 h the mixture was cooled, and from the organic layer
separated the precipitate of unreacted aminoketonea III
0.27 g). The filtrate was diluted with water and extracted
5
(
with ethyl ether. The extracts were dried on magnesium
sulfate, and ethyl ether was distilled off to leave a semic-
rystalline red-brown mass (0.21 g). As revealed by GC-
MS the residue contained the initial aminoketone III, 46%,
anil VII, 6%, and diketone IV, 5%. The resulting recov-
ery of compound III 73%, yield of compound IV 3%. No
compound VI was present in the reaction product ac-
cording to HPLC-MS data.
The reaction progress was monitored and homogene-
ity of compounds was checked by TLC on Sorbfil plates,
eluent petroleum ether-ethyl acetate (4:1), development
in iodine vapor. Melting points were measured on Bo¸tius
heating block.
Conversion of aminoketone III in the presence
of radical initiators. (a) A mixture of 0.5 g (2.37 mmol)
of aminoketone III, 1.5 g of K CO , 1.5 ml (0.42 g, 12.35
1
-Phenyl-2-phenylamino-1-ethanone (III) was
prepared by procedure [7]. It is a yellow crystalline com-
pound, after recrystallization from ethanol mp 93°C (publ.:
mp 96–98°C [7]).According to GC-MS the compound is
chromatographically homogeneous, retention time
2
3
mol) of H O , and 5 ml of ethanol was heated under re-
2
2
flux at stirring in an argon atmosphere for 5.5 h. After a
workup carried out as in the run (c) from the alcohol
layer was separated a yellow precipitate of diketone IV
–1
8
.96 min. IR spectrum (mull in mineral oil), n, cm : 3367
RUSSIAN JOURNALOF ORGANIC CHEMISTRY Vol. 40 No. 5 2004

(Z)-1,4-DIPHENYL-2-PHENYLAMINO-2-BUTENE-1,4-DIONE
697
weighing.12 g (31%). The extraction of filtrate furnished
.26 g of red-brown oily substance that according to GC-
for 15 h. The precipitate of dimer VI was filtered off,
washed with ethanol, yield 0.04 g (40%).
0
MS was a multicomponent mixture with the following main
components: compound of [M] 225 (35%), aminoketone
III (8%), and diketone IV (6%). The overall yield of com-
pound IV reached 34%.
Conversion of dimer VI into diketone IV. A mix-
ture of 0.08 g (0.19 mmol) of dimer VI, 0.2 g of K CO ,
+
2
3
0.05 ml of water, 3 ml of ethanol was heated under reflux
at stirring in an argon atmosphere for 5.5 h.After a workup
carried out as in the run (c) from the organic layer was
separated 0.02 g of diketone IV (32%). The treating of
filtrate afforded a red-brown oily substance (0.04 g) that
contained as the main component diketone IV (69%) (GC-
MS data). According to HPLC-MS the reaction mixture
contained no dimer VI. The overall yield of compound
IV was 77%.
(
b) A mixture of 0.5 g (2.37 mmol) of aminoketone
III, 1.5 g of K CO 1 ml of water, 0.64 g (2.35 mmol)
2
3,
of K S O , and 5 ml of ethanol was heated under re-
2
2
8
flux in an argon atmosphere for 5.5 h. After a workup
carried out as in the run (c) from the organic layer
was filtered off 0.3 g of yellow precipitate that ac-
cording to GC-MS data was composed of diketone IV
(
(
55%), initial aminoketone III (44%), and anil VII
1%). After treating the filtrate we obtained 0.18 g of
1-Phenyl-2-(phenylimino)ethanone (VII). A mix-
ture of 4.15 g (31 mmol) of phenylglyoxal, 2.35 ml
(26 mmol) of aniline, 20 ml of anhydrous ethanol was
kept for 24 h at room temperature under argon, and then
the reaction mixture was poured into 20 ml of water. The
precipitated yellow oily Schiff base VII was several times
washed with water, diluted with ethyl ether, the ether so-
red-brown semicrystalline substance containing
aminoketone III (70%), diketone IV (8%), and anil
VII (5%). The overall yield of compound IV reached
4
7%.
Condensation of aminoketone III with phenyl-
lution was dried on MgSO , ethyl ether was removed,
4
glyoxal (V). A mixture of 0.5 g (2.37 mmol) of amino-
ketone III, 0.48 g (3.56 mmol) of phenylglyoxal (V), 1.5
g of K CO , 1 ml of water, and 5 ml of ethanol was heated
under reflux at stirring in an argon atmosphere for 5.5 h.
From the alcoholic layer on cooling separated a precipi-
tate of the initial aminoketone III, 0.23 g (46%). After
dilution with water and treatment of the filtrate as in the
run (c), we obtained 0.56 g of red-brown oily substance
that according to GC-MS contained the following main
components: aminoketone III (11%), diketone IV (8%),
yield 3.6 g (67%). According to GC-MS data the com-
pound is homogeneous, retention time 8.14 min. Mass
2
3
+
spectrum, m/z (I , %): 209 [M] (17), 104 (100), 77
rel
(65.7).
Condensation of Schiff base VII with
aminoketone III. (a) A mixture of 1 g (4.7 mmol) of
aminoketone III, 1.2 g (5.7 mmol) of freshly prepared
Schiff base VII, 6 g of potassium carbonate, 3 ml of water,
and 20 ml of ethanol was heated under reflux at stirring
in an argon atmosphere for 2.5 h (TLC monitoring). On
cooling a precipitate separated (0.98 g) that by GC-MS
data contained diketone IV (92.1%), anil VII (3%), and
aminoketone III (4%). The filtrate was evaporated by
half, and 0.25 g of bright yellow precipitate was addi-
tionally isolated. The precipitates were combined and
recrystallized from ethanol to obtain 1.15 g of diketone
IV (75%).
+
Schiff base VII (17%), and a compound of [M] 225
(
36%). Yield of compound IV was ~6%, overall recov-
ery of compound III 58%.
,4-Diphenyl-2,3-diphenylaminobutane-1,4-dione
VI). (a_ Amixture of 0.6 g (2.85 mmol) of aminoketone
1
(
III and 0.025 ml of piperidine in 8 ml of ethanol was
boiled for 4 h on a steam bath, and then the reaction mix-
ture was maintained in air for 12 h. The separated pre-
cipitate was filtered off and washed with ethanol, yield
(b) In 10 ml of ethanol was dissolved at heating 0.25 g
(1.2 mmol) of aminoketone III, and to the solution was
0
.15 g (25%), yellow crystalline substance, mp 183–184°C
added 0.3 g (1.4 mmol) of Schiff base VII and 0.05 ml
of piperidine in 10 ml of ethanol. Through a homogeneous
mixture argon was bubbled, and the reaction mixture was
maintained at room temperature under argon for 36 h.
The reaction progress was monitored by TLC, and after
each sampling argon was again bubbled through the mix-
ture. The separated yellow precipitate of dimer VI was
filtered off, washed with ethanol, and dried; yield 0.2 g
(40%).
(from ethyl acetate) (publ.: mp 184–185°C [7]). IR spec-
–
1
trum, (KBr), n, cm : 3345 (N–H), 1664 (conjug. C=O),
1
1
pseudomolecular ion, m/z: 421 [M + H] (calculated for
C H N O 420).
599, 1447 (Ph), 1579 (bending vibrations of N–H), 1269,
295(C–N). By means of HPLC-MS was registered a
+
2
8
24
2
2
(b) A mixture of 0.1 g (0.47 mmol) aminoketone III
and 0.01 ml of piperidine in 5 ml of ethanol was kept in air
RUSSIAN JOURNALOF ORGANIC CHEMISTRY Vol. 40 No. 5 2004

6
98
AKIMOVAet al.
vol. 46, p. 5156.
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RUSSIAN JOURNALOF ORGANIC CHEMISTRY Vol. 40 No. 5 2004