Investigation of the reaction of N-acetylindoxyl with substituted anilines. Synthesis of derivatives of indolo[3,2-b]quinolines

Article abstract of DOI:10.1023/A:1012459810266

1-Acetyl-2,3-dihydrospiro[indolo-3, 2′-(1′,2′,3′, 4′-tetrahydroquinazolin-4′-one) was obtained from the reaction with anthranilamide, and 3-(2′-acetylaminophenyl)quinoxalin-2-one from the reaction with o-phenylenediamine, along with the normal products of the condensation of N-acetylindoxyl with substituted anilines. Derivatives of indolo[3,2-b]quinoline were synthesized from the obtained condensation products.

Full text of DOI:10.1023/A:1012459810266

Chemistry of Heterocyclic Compounds, Vol. 37, No. 7, 2001
INVESTIGATION OF THE REACTION
OF N-ACETYLINDOXYL WITH SUBSTITUTED
ANILINES. SYNTHESIS OF DERIVATIVES
b
OF INDOLO[3,2- ]QUINOLINES
N. Z. Tugusheva1, S. Yu. Ryabova, N. P. Solov'eva2, O. S. Anisimova2, and V. G. Granik1
1-Acetyl-2,3-dihydrospiro[indolo-3,2'-(1',2',3',4'-tetrahydroquinazolin-4'-one) was obtained from the
reaction with anthranilamide, and 3-(2'-acetylaminophenyl)quinoxalin-2-one from the reaction with
o-phenylenediamine, along with the normal products of the condensation of N-acetylindoxyl with
substituted anilines. Derivatives of indolo[3,2-b]quinoline were synthesized from the obtained
condensation products.
Keywords: aniline, acetylindoxyl, indoloquinoline, quinazoline, quinoxaline.
A series of 3-arylaminoindoles, from which derivatives of indolo[3,2-b]quinolines were synthesized,
was obtained by the reaction of N-acetylindoxyl (1) with a number of aromatic amines. In a study of some
properties of the quinolines it was established that functionalization of these compounds is possible by
alkylation at the indole NH group and by quaternization of the quinoline nitrogen atom with subsequent
treatment with base to convert the quaternary salt into a derivative of indolo[3,2-b]quinolin-11-one with the oxo
functional group in position 11 [1].
The present work is concerned with further study of reactions of compound 1 with substituted anilines.
Condensation of N-acetylindoxyl (1) with m-nitroaniline (2a) under conditions previously used for
p-nitroaniline [2] – refluxing in acetic acid – gave 3-(m-nitrophenyl)aminoindole (3a) in 52% yield. Other
reactions conditions – refluxing the components in toluene in the presence of p-toluenesulfonic acid with
removal of water – were optimal for this reaction with the yield of the desired product (3a) reaching 95%.
Reaction of the aminoindole (3a) with Vilsmeier's reagent gave a mixture of 10-acetyl-1-nitroindolo[3,2-b]-
quinoline (4) and 3-aryl-2-formylaminoindole (5), but the two products were isolated in much smaller yield than
the previously prepared 2-nitro derivatives of this system [2]. Under the same conditions o-nitroaniline did not
react with acetylindoxyl 1; only the starting materials were isolated. As a result we paid particular attention to
the reaction of 1 with o-substituted anilines.
It appeared that derivatives of aniline with an electron-donating or relatively weak electron-accepting (in
comparison with the nitro group) substituent in the o-position reacted readily under the same conditions with
compound
1
to give the corresponding 3-aminoindoles. For example, N-acetyl-3-(o-substituted
phenylamino)indoles (3b-d) were readily obtained from o-aminophenol, anthranilic acid, and ethyl anthranilate
__________________________________________________________________________________________
1
"NIOPIK" State Science Center of the Russian Federation, Moscow 103787, Russia; e-mail:
2
makar-cl@ropnet.ru. Center for the Chemistry of Medicinal Materials, All-Russia Scientific Chemical-
Pharmaceutical Research Institute, Moscow 119021. Translated from Khimiya Geterotsiklicheskikh Soedinenii,
No. 7, 962-970, July 2001. Original article submitted September 3, 1999.
0009-3122/01/3707-0885$25.00©2001 Plenum Publishing Corporation
885

(2b-d). When compound 1 was refluxed in acetic acid with anthranilic acid (2c) or its ethyl ester (2d) complex
mixtures of products were obtained which included, according to the 1H NMR and mass spectra, indolo[3,2-b]-
quinolin-11-one (6) along with the indoles 3c,d. The tetracycle 6 was isolated in 10% yield from the mixture
1
obtained by condensation of compounds 1 and 2c. According to the H NMR spectrum the mixture contained
compounds 3c and 6 in a 1:1 ratio. Attempts to cyclize the ester 3d under various conditions gave a positive
result only on refluxing in ethylene glycol when the tetracycle 6 was isolated in 21% yield.
On reaction of N-acetylindoxyl (1) with anthranilamide (2e) a mixture of two compounds was obtained
1
in a ratio of 3:7 according to the H NMR spectra. According to the spectra the minor product was
3-arylaminoindole 3e. Compound 7 was isolated by recrystallization from the mixture. According to the mass
1
spectrum it had a molecular mass, m/z 293 (M+). The H NMR spectrum of this compound shows a quartet at
4.22 ppm, corresponding to the methylene protons 2-CH2 of the N-acetylindole fragment. That the protons of
this group are not equivalent arises from the presence in the molecule of an asymmetric center at C(3). The
13C NMR spectrum of compound 7 reveals a signal of the sp3-hybridized quaternary carbon C(3) at 74.8 ppm. It
was concluded from these results that 7 is a spiro compound.
H
N
N
+
N
N
CHO
NO2
NO2
Me
O
4
Me
O
5
for 3a
H
O
N
R
+
R
N
H2N
N
2a–f
Me
O
Me
O
3a–f
1
for 2c,d
for 3d
for 2e
H
N
HN
+
3e
N
H
O
N
H
N
O
Me
O
7
6
2, 3 a R = m-NO2, b R = o-OH, c R = o-COOH, d R = o-COOEt, e R = o-CONH2, f R = o-NH2
Prolonged heating of a mixture of compounds 3e and 7 in anhydrous conditions (toluene,
1
p-toluenesulfonic acid) gave no change in their ratio (according to the H NMR spectrum), however in the
presence of water led to a decrease in the content of the spiro compound 7 and a corresponding increase in
amide 3e ( when the mixture was heated under reflux for 3 h in toluene in the presence of p-toluenesulfonic acid
and water, the ratio of 3e to 7 changed from 26:74 to 60:40). It may be proposed that when N-acetylindoxyl (1)
reacted with the carbamide 2e the carbonylamine formed in the first step may be stabilized in two ways with the
elimination of water, to form the substituted aminoindole 3e or the spiro compound 7. Product 3e is completely
stable and undergoes no further transformations, whereas compound 7 may undergo ring opening under the
influence of H2O (H+), that leads eventually to an increase in the content of 1-acetyl-3-(o-
carbamoylphenyl)aminoindole (3e) in the mixture.
886

CONH2
H
N
HO
–H2O
+H2O
+ 2e
1
7
N
Me
O
–H2O
3e
When N-acetylindoxyl (1) was heated with o-phenylenediamine (2f) in isoamyl alcohol the product
obtained did not correspond to the expected condensation product 3f according to its elemental analysis and
mass spectrum. The mass spectrum reveals a molecular ion peak at m/z 279 (M+) which indicates the presence
of an additional oxygen atom. In the literature [3, 4] the reaction of N-acetylisatin (8) with a series of
o-diamines has been described and it has been proposed that the products have the spiro structure 9.
On repeating this reaction we obtained a product identical in physical constants with the compound
synthesized from N-acetylindoxyl and o-phenylenediamine and corresponding in mp and mass spectrum with
the compound described previously [3]. However its IR spectrum did not contain an absorption band at
1690 cm-1, characteristic of an amide fragment, but absorption bands were observed at 1650 and 1635 cm-1.
13
Moreover, there was no signal of a quaternary sp3 carbon atom in the C NMR spectrum (not described in [3,
1
4]), which rules out the spiro structure 9. In the H NMR spectrum (DMSO-d6), along with the signals of the
13
aromatic protons, signals were observed at 1.90 and for NH groups at 9.77 (s) and 12.50 ppm (br). C NMR
spectrum , δ, ppm: 24.1 (CO
CH3), 123.3, 123.5, 128.9, and 129.9 (CH-Ph), 115.5, 123.5, 130.5, 131.1
(CH-arom), 128.0, 132.2, 132.6, 137.1, 157.2 (quaternary C-arom), 154.8 (s, CO), and 168.3 (q, COCH3). The
1
absence of signals for NH2 protons in the H NMR spectrum rules out the structure 10a, but the possibility of
N N transacetylation to give a compound with the structure 10b is not completely excluded.
→
NH2
NHCOMe
HN
O
N
N
N
H
N
O
N
N
H
O
O
Me
Me
O
10a
10b
9
Opening of the pyrrole ring was observed when N-acetylisatin (8) reacted with amines to give
substituted phenylglyoxamides 11 which were readily converted to the imino derivatives 12 [5].
NR'
CONHR
NH
O
O
R'NH2
RNH2
CONHR
O
N
O
NH
Me
O
Me
O
Me
12
8
11
In our case the reaction may occur as follows:
887

NHCOMe
N
H2N
O
O
RNH2
8
N
H
NH
O
N
H
Me
O
13
Unambiguous choice between structures 10b and 13 on the basis of spectroscopic data is rather
complex, so the corresponding model compounds were synthesized – 3-phenyliminoindolin-2-one (14) [6, 7]
and 3-phenylquinoxalin-2-one (15) [8].
N
N
N
H
O
O
N
H
15
14
1
13
To judge from the H and C NMR spectra, compound 14 exists in DMSO-d6 solution as a mixture of
two geometric isomers (87 and 13%) relative to the C=N bond: the chemical shift of the 4-H proton of the
predominant isomer is equal to 6.30 and of the minor isomer to 7.59 ppm. The 13C NMR spectrum of compound
14 contains, along with signals of the carbon atoms of a monosubstituted benzene ring, signals which are typical
13
for isatin derivatives, in particular the signal of the quaternary carbon atom C(3a) at 116.0 ppm. The C NMR
spectrum of the model compound 15 differs considerably from that of 14: the signals of sp2-hybridized quaternary
carbon atoms were observed at 132.3 (m), 132.4 (m), 135.9 (t), 154.3 (t), and 154.9 (s) ppm which are very
close to those of the compound isolated from the reaction which therefore may be ascribed the structure 13. The
UV spectra of compound 13 and the model 15 contain absorption maxima at 311.8, 366.1 and 310.0, 362.0 nm
λ
respectively, whereas for compound 14 max = 296.6 and 408.6 nm, i.e., there is no doubt about the similarity of
the electronic structures of 13 and 15. Additional evidence that 3-(o-acetylamino)phenylquinoxalin-2-one (13) is
formed in the reaction of N-acetylisatin (8) with o-phenylenediamine (2f) is provided by experiments of the
1
nuclear Overhauser effect in the H NMR spectrum and isotopic substitution in the 13C NMR spectrum.
Irradiation of the COCH3 signal (1.91 ppm) leads to an increase in intensity of the signal at 9.77 ppm (NH, sharp
signal), and on the other hand irradiation of this NH signal increases the intensities of the COCH3 signal and the
broad doublet at 7.82 ppm (in the o-position relative to the NHCOCH3 group). The effect of isotopic
C NMR spectrum for the signals of the acetyl fragment: Δδ
substitution is observed in the 13
C=O), -0.03 (24.1 CH3); for the quaternary carbon atom C(2')
at 123.3 Δδ
presence of the NHCOCH3 substituent in the benzene ring. Finally, the mass spectrum agrees well with the
structure proposed. The basic fragmentation is shown in Scheme 1.
13C = -0.08 (168.3,
13C = -0.11 (137.1, t); for the protonated carbon
: Δδ
13C = -0.09; and for the quaternary carbon C(1')
13C = -0.09 (128.0 m). This confirms the
Δδ
C(3')
When N-acetylindoxyl (1) and o-phenylenediamine (2f) were heated in isoamyl alcohol compound 13
was formed which was identical in physical properties and spectroscopic characteristics with the product
obtained from N-acetylisatin (8) and amine 2f in either ethanol or isoamyl alcohol. The spectra were more
complex when the reaction of N-acetylindoxyl (1) with o-phenylenediamine (2f) was carried out in toluene with
1
the removal of water in the presence of p-toluenesulfonic acid. To judge from the H NMR spectrum
(DMSO-d6) a mixture of two substances was formed one of which was readily identified as the quinoxalinone
13 by comparison with the spectrum of a known sample. The second compound was characterized by the
1
presence in the H NMR spectrum of an acetyl group at 2.09, 8 aromatic protons (7.20-7.82 ppm), a CH–COH
888

.
+
.
118
+
.
–CO
+
.
+
N
NHAc
NH
NH
134
91
N
–COCH2
92
NH
91
–COMe
O
NH
279
+
NH
N
O
Me
O
146
90
–COMe
–H2O
–COCH2
218
N
.
NH
+
NH
+
–COMe
O
NH
O
+
236
.
N
NH
+
N
N
.
+
NH
–CO
O
264
O
NH2
N
–H2O
237
220
COMe
261
NH
–COCH2
N
–NH3
NH2
+
.
+
209
N
N
N
N
O
H
219

fragment with the corresponding signals at 5.26 (–CH) and 6.52 ppm (OH, 4JCH,OH = 1.6 Hz), and downfield NH
13
signals at 9.75 and 10.70 ppm. In the C NMR spectrum the signals of the carbon atoms of the acetyl group
(24.2 and 168.7 ppm), 8 aromatic protonated and 4 quaternary sp2-hybridized carbon atoms and the CH–C–OH
fragment were clearly identified. Carbon with a neighboring heteroatom absorbed at 55.2 (CH, 1JCH = 143), and
the quaternary sp3-hybridized carbon atom, with no less than two heteroatom substituents resonated at 79.5 ppm.
After this mixture was heated in DMSO-d6 on a water bath for 5 h the content of the second component
decreased, and after 10 h the spectrum corresponded to the spectrum of individual compound 13. To judge by
the data obtained for the second compound it is proposed that it is 6-acetyl-5a-hydroxy-5,5a,10b,11-
tetrahydroindolo[2,3-b]quinoxaline (16). The following scheme is proposed for the formation of compounds 16
and 13:
H
H
N
H
N
oxydation
2f
1
H2N
N
N
H2N
O
Me
O
Me
O
3f
H
H
H
N
N
dehydrogenation
∆
13
HN
N
N
H
O
N
H
Me
OH
Me
O
O
16
The driving force for the proposed scheme is the presence in intermediate 3f of a strong electron
donating substituent (NH2) in the benzene ring which facilitates oxidation at position 2 of the indole ring.
Further transformations of the intermediate oxoindole leads to the tetracycle 16 and then to the quinoxaline 13.
TABLE 1. Characteristics of the Compounds Synthesized
Found, %
——————
Com-
Empirical
Yield, %
(method)
mp, °С
Calculated, %
pound formula
С
Н
N
С16Н13N3O3
65.28
65.08
4.43
4.41
14.41
14.24
198-199
52 (A)
95 (B)
3a
3b
3c
3d
4
(propanol-2)
С16Н14N2O2
С17Н14N2O3
С19Н18N2O3
С17Н11N3O3
С17Н13N3O4
С15Н10N2O
С17Н15N3O2
72.18
5.40
10.39
185-186
99
74
90
10
7
72.09
5.26
10.53
(propanol -2)
69.23
69.39
4.90
4.76
9.51
9.52
211-213
(propanol-2)
70.79
5.79
8.67
108-110
70.81
5.59
8.70
(propanol-2)
67.15
66.89
3.85
3.61
13.87
13.77
250-251
(propanol-2–DMF, 1:1)
63.21
4.06
13.00
196-197
5
63.16
4.02
13.00
(МеОН–DMF, 7:4)
76.92
76.92
4.29
4.27
11.89
11.97
>355
21 (А)
6
7 (B)
69.29
5.45
14.36
289-292
31
7
69.62
5.12
14.33
(propanol-2–DMF, 2:1)
890

EXPERIMENTAL
IR spectra of nujol mulls were recorded on a Perkin-Elmer 457 spectrometer. Mass spectra were
obtained with a Finnigan-MAT SSQ-710 mass spectrometer with direct inlet of the sample into the ion source,
1
13
energy of the ionizing electrons 70 eV, ionization chamber temperature 150°C. H and C NMR spectra were
recorded on a Varian UNITY plus 400 spectrometer (400 and 100.6 MHz respectively) with TMS as internal
standard. The course of reactions and purity of the products were monitored by TLC on Silufol UV-254 plates
with chloroform–methanol, 1:10 as eluant and visualization with UV light. Characteristics of the compounds
synthesized are given in Table 1.
1-Acetyl-3-(3'-nitrophenyl)aminoindole (3a). A. A solution of N-acetylindoxyl (1 g, 5.7 mmol) and
m-nitroaniline (0.8 g, 5.8 mmol) in acetic acid (5 ml) was refluxed for 2 h. The reaction mixture was cooled to
20°C, the precipitate was filtered off and washed with ethyl acetate to give 3a (0.88 g).
B. p-Toluenesulfonic acid (0.3 g, 1.6 mmol) was added to solution of N-acetylindoxyl (5 g, 28.6 mmol)
and m-nitroaniline (4 g, 29 mmol) in toluene (50 ml). The mixture was refluxed with a Dean and Stark trap for
30 min and then cooled to 20°C. The precipitate was filtered off, washed with toluene and ether to give
compound 3a (5.3 g). p-Toluenesulfonic acid (0.05 g) was added to the filtrate which was again refluxed with a
Dean and Stark trap for 15 min until a precipitate appeared. An additional 2.7 g of 3a was obtained.
IR spectrum, , cm-1: 3340, 1670, 1610, 1590. M+· 295. A mixture of compound B with a sample prepared by
ν
method A gave no depression of the melting point.
1-Acetyl-3-(2'-hydroxyphenyl)aminoindole (3b). o-Aminophenol (0.64 g, 5.9 mmmol) and
p-toluenesulfonic acid (0.05 g) were added to a suspension of N-acetylindoxyl (1 g, 5.7 mmol) in toluene
(20 ml). The mixture was refluxed with a Dean and Stark trap for 2 h, adding toluene when necessary. The
precipitate which formed during reflux was filtered off after cooling the reaction mixture to 20°C to give
compound 3b (1.5 g). M+· 266.
1-Acetyl-3-(2'-hydroxycarbonylphenyl)aminoindole (3c) was obtained from N-acetylindoxyl (1 g,
5.7 mmol) and anthranilic acid (0.8 g, 5.8 mmol) as for the synthesis of compound 3b, reflux time 3 h. The
precipitate was washed with a small amount of ether to give compound 3c (1 g). IR spectrum, , cm-1: 3310,
ν
1710, 1670, 1600, 1520. M+· 294.
1-Acetyl-3-(2'-ethoxycarbonylphenyl)aminoindole (3d) was obtained from N-acetylindoxyl (2 g,
11.4 mmol) and ethyl anthranilate (2 g, 12 mmol) as for the synthesis of compound 3b, reflux time 5 h.
Methanol was added to the reaction mixture and the precipitate filtered off to give compound 3d (3.3 g).
M+· 322.
10-Acetyl-1-nitroindolo[3,2-b]quinoline (4). A solution of compound 3a (5 g, 17 mmol) in DMF
(25 ml) was added at 20°C to Vilsmeier complex prepared in the normal way from POCl3 (5 ml) and DMF
(10 ml). The reaction mixture was stirred for 3 days at 18°C. The precipitate was filtered off and washed with
water to give crude 4 (1.65 g). It was recrystallized from 1:1 DMF-propanol-2 to give pure compound 4 (0.5 g).
IR spectrum, , cm-1: 1695, 1615, 1525. M+· 305.
ν
1-Acetyl-2-formyl-3-(3'-nitrophenyl)aminoindole (5) was obtained from compound 3a (0.5 g,
1.7 mmol) and the Vilsmeier complex as for the synthesis of compound 4. The reaction mixture was kept at
18°C for 2.5 h and then poured into ice water. The precipitate which formed over 1.5 h was filtered off and
washed with water to give compound 5 (0.22 g). It was recrystallized from 7:4 MeOH–DMF to give 0.04 g of
pure compound 5. M+· 323.
5,10-Dihydroindolo[3,2-b]quinolin-11-one (6). A. A solution of compound 3d (0.2 g, 0.6 mmol) in
ethylene glycol (3 ml) was refluxed for 10 h. The reaction mixture was cooled to 20°C, the precipitate was
1
filtered off and washed with acetone to give compound 6 (0.03 g). M+· 234. H NMR spectrum (DMSO-d6),
δ,
ppm: 7.20 (1H, t, 2-H); 7.30 (1H, t, 7-H); 7.47 (1H, t, 8-H); 7.54 (1H, d, 9-H); 7.69 (1H, t, 3-H); 7.75 (1H, d,
4-H); 8.20 (1H, d, 1-H); 8.37 (1H, d, 6-H); 11.71 (1H, s, 5-NH); 12.54 (1H, br. s, 10-NH).
891

B. A solution of N-acetylindoxyl (1 g, 5.7 mmol) and anthranilic acid (0.8 g, 5.8 mmol) in acetic acid
(5 ml) was refluxed for 5 h. The precipitate was filtered off and washed with methanol to give a mixture of
1
+·
+·
compounds 3c and 6 (0.25 g, 1:1 according to the H NMR spectrum; M1 294, M2 234). The mixture was
treated with aqueous alkali, the insoluble residue was filtered off and washed with water to give compound 6
(0.09 g). A mixture of compound B with a sample prepared by method A gave no depression of the melting
point.
1-Acetyl-2,3-dihydrospiro[indolo-3,2'-(1',2',3',4'-tetrahydroquinazolin-4'-one)] (7) was obtained
from N-acetylindoxyl (1 g, 5.7 mmol) and anthranilamide (0.82 g, 6 mmol) as for the synthesis of compound 3b,
reflux time 3 h. The precipitate was ground in methanol (5 ml), filtered off, washed with methanol to
1
give compounds 3e and 7 (1.1 g, 32:68 according to the H NMR spectrum). The material was recrystallized
+·
1
), δ, ppm:
from 2:1 propanol-2–DMF to give compound 7 (0.51 g). M 293. H NMR spectrum (DMSO-d6
2.17 (3H, s, CH3); 4.22 (2H, q, 2-H); 6.69 (1H, d, 8'-H); 6.76 (1H, t, 6'-H); 7.04 (1H, t, 5-H); 7.30 (1H, d, 6-H);
7.31 (1H, d, 4-H); 7.35 (1H, t, 7'-H); 7.46 (1H, s, NH); 7.68 (1H, d, 7-H); 8.12 (1H, d, 5'-H); 8.63 (1H, s,
13
), δ, ppm: 24.4 (CH
CONH). C NMR spectrum (DMSO-d6
3), 62.9 (CH2), 74.8 (C(3)), 114.9, 116.9, 118.2,
123.4, 124.2, 127.7, 130.6, 134.3 (arom. CH), 114.3 (C(3a)), 134.7 (C(4a')), 141.4 and 146.5 (C(8a'), C(7a)),
163.1 (CONH).
3-(2'-Acetylaminophenyl)quinoxalin-2-one (13). A. A solution of N-acetylindoxyl (1.4 g, 8 mmol)
and o-phenylenediamine (0.8 g, 8.1 mmol) in isoamyl alcohol was refluxed for 10 h. The mixture was cooled to
20°C, the precipitate was filtered off to give compound 13 (0.55 g, 22%); mp 292-294°C (DMF). IR spectrum,
, cm-1: 3215, 3100, 1650, 1635, 1600, 1585. M+· 279.
ν
B. A suspension of N-acetylisatin (0.3 g, 1.6 mmol) and o-phenylenediamine (0.17 g, 1.6 mmol) in
isoamyl alcohol (7 ml) was refluxed for 5 min, then was cooled, the precipitate was filtered off and washed with
isoamyl alcohol and ether to give compound 13 (0.29 g, 66%).
C. Compound 13 (0.23 g, 52%) was obtained from N-acetylisatin (0.3 g, 1.6 mmol) and
o-phenylenediamine (0.17 g, 1.6 mmol) in ethanol (10 ml) analogously to method B. A mixture of samples
prepared by methods A and B gave no melting point depression.
Mixture of 3-(2'-acetylaminophenyl)quinoxalin-2-one (13) and 6-acetyl-5a-hydroxy-5,10b,11-H-
indolo[3,2-b]quinoxaline (16) was obtained from N-acetylindoxyl (0.5 g, 2.9 mmol) and o-phenylenediamine
(0.32 g, 3.0 mmol) under the conditions for the synthesis of compound 3b, reflux time was 4 h. The precipitate
which appeared after 48 h at 20°C was filtered off and washed with toluene and methanol to give a mixture of
compounds 13 and 16 (0.15 g).
1
), δ, ppm, major isomer:
3-Phenyliminoindolin-2-one (14) [6, 7]. H NMR spectrum (DMSO-d6
6.30 (1H, d, 4-H); 6.71 (1H, t, 5-H); 6.97 (2H, d, 2',6'-H); 7.33 (1H, m, 4'-H); 7.33 (1H, m, 6-H); 7.46 (2H, t,
3',5'-H); 7.90 (1H, d, 7-H); 11.00 (1H, br.s, NH). Minor isomer: 6.86 (1H, d, 7-H); 6.99 (2H, d, 2',6'-H);
7.06 (1H, t, 5-H); 7.30 (1H, t, 4'-H) 7.45 (2H, t, 3',5'-H); 7.45 (1H, t, 6-H); 7.59 (1H, d, 4-H); 10.90 (1H, br.s,
13
), δ, ppm: principle isomer: 111.8 (C
NH). C NMR spectrum (DMSO-d6
(7)), 116.0 (C(3a)), 117.5 (C(2',6')),
122.0 (C(4)), 125.2, 125.7 (C(4')) or (C(5)), 129.9 (C(3',5')), 134.8 (C(6)), 147.3 (C(1')), 150.9 (C(7a)), 155.3 (C(3)),
163.8 (C(2)).
1
), δ, ppm: 7.30-7.36 (2H, m);
3-Phenylquinoxalin-2-one (15) [8]. H NMR spectrum (DMSO-d6
7.46-7.57 (4H, m); 7.84 (1H, m); 8.30 (2H, m, 2',6'-H); 12.60 (1H, br. s, NH). 13C NMR spectrum (DMSO-d6),
δ,
ppm: 115.4, 123.7, 130.5, 130.6 (C(5-8)), 128.2 (2C), 129.0 (1C), 129.2 (2C) (Ph), 132.3, 132.4 (C(4a), C(8a)),
135.9 (C(1')), 154.3 (C(3)), 154.9 (C(2)).
This work was carried out with a financial subvention from the Russian for Fundamental Research
(grant 97-03-33066).
892

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