Intramolecular cyclization of O-(3,5-dinitrophenyl) and O-(3-amino-5-nitrophenyl) ketoximes, products of transformations of 1,3,5-trinitrobenzene. the synthesis of nitrobenzo[b]furans and 4-hydroxynitroindoles

Article abstract of DOI:10.1007/s11172-007-0153-6

O-(3,5-Dinitrophenyl) ketoximes obtained in the reactions of ketoximes with 1,3,5-trinitrobenzene undergo acid-catalyzed cyclization into 2-substituted or 2,3-disubstituted 4,6-dinitrobenzo[b]furans. In analogous cyclization, products of selective reduction of a nitro group in O-(3,5-dinitrophenyl) ketoximes unexpectedly yield, along with 6-amino-4-nitrobenzofurans, 4-hydroxy-6- nitroindoles. The 4-NO₂ group is displaced from 4,6-dinitrobenzo[b] furans in reactions with thiols in the presence of K₂CO₃. Conditions for nitration and sulfochlorination of 4,6-dinitrobenzo[b]furans in position 3 were found. Condensation of a 2-methyl derivative with dimethylformamide acetal was accomplished.

Full text of DOI:10.1007/s11172-007-0153-6

Russian Chemical Bulletin, International Edition, Vol. 56, No. 5, pp. 1020—1027, May, 2007
1020
Intramolecular cyclization of Oꢀ(3,5ꢀdinitrophenyl) and
Oꢀ(3ꢀaminoꢀ5ꢀnitrophenyl) ketoximes, products of transformations
of 1,3,5ꢀtrinitrobenzene. The synthesis
of nitrobenzo[b]furans and 4ꢀhydroxynitroindoles
S. S. Vorob´ev, M. D. Dutov, I. A. Vatsadze, E. P. Petrosyan,
V. V. Kachala, Yu. A. Strelenko, and S. A. Shevelevꢀ
N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences,
47 Leninsky prosp., 119991 Moscow, Russian Federation.
Fax: +7 (495) 135 5328. Eꢀmail: Shevelev@ioc.ac.ru
Oꢀ(3,5ꢀDinitrophenyl) ketoximes obtained in the reactions of ketoximes with 1,3,5ꢀtriꢀ
nitrobenzene undergo acidꢀcatalyzed cyclization into 2ꢀsubstituted or 2,3ꢀdisubstituted 4,6ꢀdiꢀ
nitrobenzo[b]furans. In analogous cyclization, products of selective reduction of a nitro group
in Oꢀ(3,5ꢀdinitrophenyl) ketoximes unexpectedly yield, along with 6ꢀaminoꢀ4ꢀnitrobenzofurans,
4ꢀhydroxyꢀ6ꢀnitroindoles. The 4ꢀNO2 group is displaced from 4,6ꢀdinitrobenzo[b]furans in
reactions with thiols in the presence of K2CO3. Conditions for nitration and sulfochlorination
of 4,6ꢀdinitrobenzo[b]furans in position 3 were found. Condensation of a 2ꢀmethyl derivative
with dimethylformamide acetal was accomplished.
Key words: 1,3,5ꢀtrinitrobenzene, (3,5ꢀdinitrophenyl) ketoximes, Oꢀ(3ꢀaminoꢀ5ꢀnitroꢀ
phenyl) ketoximes, 6ꢀaminoꢀ4ꢀnitrobenzofurans, 4ꢀhydroxyꢀ6ꢀnitroindoles, 4,6ꢀdinitrobenzoꢀ
furans, nucleophilic displacement of nitro groups, cyclization.
Scheme 1
The present work was performed within the scope of
investigations of 1,3,5ꢀtrinitrobenzene (TNB) for use as a
multipurpose synthon, including the synthesis of polyꢀ
functional benzoannulated heterocycles. These investigaꢀ
tions are included in the program for chemical disposal of
explosive 2,4,6ꢀtrinitrotoluene (TNT) and its conversion
into a chemical raw material for various applications.1,2
1,3,5ꢀTrinitrobenzene can be easily derived from TNT by
twoꢀstep oxidative demethylation.3,4
A characteristic feature of TNB is its ability to add
nucleophiles at the orthoꢀposition relative to the nitro
group to form stable anionic σꢀH complexes.5—8 Earꢀ
lier,9—14 we have found conditions for displacement of
one or more nitro groups in TNB by a number of anionic
Oꢀ, Sꢀ, and Nꢀnucleophiles. The resulting products can
serve as starting materials for the synthesis of new polyꢀ
functional aromatic and heterocyclic structures.
R, R´ = H, Alk, Ar, Het
NMP is Nꢀmethylpyrrolidone
Recently,14 we have demonstrated that ketoximes and
aldoximes in the presence of a base displace a nitro group
from TNB to give earlier unknown Oꢀ(3,5ꢀdinitrophenyl)
oximes (Scheme 1).
Here we found that Oꢀ(3,5ꢀdinitrophenyl) ketoximes 1
containing a methyl group (R1 = H) or a methylene fragꢀ
ment (R1 = Alk) at the C atom of the C=N bond smoothly
undergo cyclization under mild conditions into 2ꢀsubstiꢀ
tuted (for R1 = H) or 2,3ꢀdisubstituted (for R1 = Alk)
4,6ꢀdinitrobenzo[b]furans 2 (Scheme 2)*.
Cyclization occurred even upon heating (>80 °C) of
oximes 1 in Nꢀmethylpyrrolidone (NMP) or DMF; howꢀ
ever, the best results were achieved under acid catalysis
conditions: reflux in conc. HCl + ethanol (1 : 1 v/v) (for
* For the preliminary communication, see Ref. 15.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 984—991, May, 2007.
1066ꢀ5285/07/5605ꢀ1020 © 2007 Springer Science+Business Media, Inc.

Nitrobenzo[b]furans and nitroindoles
Russ.Chem.Bull., Int.Ed., Vol. 56, No. 5, May, 2007
1021
ized literature data, Guzzo et al.26 have concluded that
[3,3]ꢀsigmatropic rearrangement should be favored by
electronꢀdonating substituents in the benzene ring but
hindered by electronꢀwithdrawing ones. Although cyꢀ
clization of Oꢀaryl oximes containing strong electronꢀ
withdrawing groups in the aryl fragment has been deꢀ
scribed,22,24 all documented examples involve very drasꢀ
tic conditions with electronꢀwithdrawing groups (NO2,
CN, RSO2, etc.) being meta to the C atom at which ring
closure occurs; if two such groups are present simultaꢀ
neously, the yield of the resulting benzofuran is substanꢀ
tially lower.22,24
In the present work, we were the first to carry out
cyclization of Oꢀaryl oximes into products with a new C—C
bond formed at the C atom that is ortho/para to strong
electronꢀwithdrawing substituents (two nitro groups). Apꢀ
parently, this arrangement of electronꢀwithdrawing subꢀ
stituents is more favorable for cyclization of Oꢀaryl oximes
than their metaꢀposition relative to a new C—C bond.
We made a preliminary estimation of the reactivities
of 4,6ꢀdinitrobenzo[b]furans 2 in a number of standard
reactions.
We studied the possibility of and conditions for nucleoꢀ
philic displacement of a nitro group in 4,6ꢀdinitroꢀ
benzo[b]furans 2. As expected, dinitrobenzofurans 2 are
not highly electrophilic because of the πꢀabundant charꢀ
acter of the benzofuran system, which can hinder nucleoꢀ
philic displacement of a nitro group. Nevertheless, we
found conditions in which a nitro group (4ꢀNO2) that is
in periꢀposition is displaced in reactions with aromatic
and aliphatic thiols in NMP in the presence of K2CO3 as
a deprotonating agent. This can be suitable for the synꢀ
thesis of novel 4ꢀRSꢀ6ꢀnitrobenzo[b]furans 3 (Scheme 4).
Displacement of the 4ꢀNO2 group in dinitrobenzoꢀ
furans 2 was proven by NOE data for 4ꢀ(4ꢀchlorophenylꢀ
thio)ꢀ3ꢀmethylꢀ6ꢀnitroꢀ2ꢀphenylbenzo[b]furan (3i) as an
example. The NOE experiment revealed a coupling beꢀ
tween the H(5) proton of the nitrobenzene ring and the
H(2´) and H(6´) protons of the thiol substituent and couꢀ
Scheme 2
1, 2: R1 = H, R2 = Me (a), Ph (b), 4ꢀBrC6H4 (c), 4ꢀFC6H4 (d),
3,4ꢀmethylenedioxyphenyl (e), 4ꢀpyridyl (f),
2ꢀpyridyl (g), 2ꢀMeOC6H4 (h), 2,5ꢀ(MeO)2C6H3 (i),
4ꢀHOC6H4 (j), 2ꢀfuryl (k), 2ꢀthienyl (l);
R1R2 = —(CH2)4— (m), —CH2CH(Me)CH2CH2— (n);
R1 = Me, R2 = Ph (o)
1a—e,h—l), heating (80 °C) in conc. H2SO4 + AcOH
(1 : 1 v/v) (for 1f,g with formation of sulfates 2f,g as
products), or reflux in conc. HCl + AcOH (2 : 5 v/v)
(for 1m—o). The reaction was carried out until the startꢀ
ing oxime was consumed completely (4—18 h). The yields
of 4,6ꢀdinitrobenzo[b]furans 2 were 60—95%.
The proposed approach is a new and general route
to 2ꢀsubstituted and 2,3ꢀdisubstituted 4,6ꢀdinitrobenꢀ
zo[b]furans. The described16,17 synthesis of 2ꢀsubstituted
3ꢀacylꢀ4,6ꢀdinitrobenzo[b]furans involves intramolecular
cyclization of Cꢀpicrylated 1,3ꢀdicarbonyl compounds.
The synthesis of some 2ꢀsubstituted 4,6ꢀdinitrobenꢀ
zo[b]furans is of particular character.18—20
It should be noted that acidꢀcatalyzed intramolecular
cyclization of Oꢀaryl oximes into benzofurans is well
known21—27 and analogous to the Fischer transformation
of Nꢀarylhydrazones into indoles.28 The mechanism proꢀ
posed25,26 for this cyclization is shown in Scheme 3.
According to modern concepts,26 the key step of the
reaction is an acidꢀcatalyzed [3,3]ꢀsigmatropic rearrangeꢀ
ment of the enehydroxylamine form of Oꢀaryl oxime
(B → C) followed by aromatization of the sixꢀmembered
ring (C → D), closure of a dihydrofuran ring (D → E), and
its aromatization via elimination of the ammonium
ion (E → F). Based on this mechanism and generalꢀ
Scheme 3

1022
Russ.Chem.Bull., Int.Ed., Vol. 56, No. 5, May, 2007
Vorob´ev et al.
Scheme 4
in electrophilic displacement reactions. It was found that
compound 2a is smoothly nitrated with H2SO4 + HNO3
at position 3 to produce trinitro derivative 4 (Scheme 5).
Dinitrobenzo[b]furan 2a also readily undergoes sulfoꢀ
chlorination. The resulting sulfonyl chloride 5 reacts with
morpholine to give the corresponding substituted sulfonaꢀ
mide 6 (see Scheme 5). At the same time, dinitroꢀ
benzofuran 2a is inert to weaker electrophiles. For inꢀ
stance, its furan fragment cannot be formylated in
the Vilsmeier reaction (heating with DMF—SOCl2 or
DMF—POCl3) at free position 3, which is probably due
to the deactivating effect of the nitro groups on electroꢀ
philic displacement.
3
R1
R2
R3
3
R1
R2
Ph
Me
Ph
Ph
R3
a
b
c
d
e
H
H
Me
H
H
Me
Ph
Ph
Me
Ph
Ph
Ph
Ph
PhCH2
PhCH2
f
g
h
i
Me
H
H
PhCH2
4ꢀClC6H4
4ꢀClC6H4
4ꢀClC6H4
Me
The nitro groups increase the reactivity of the methyl
group in the furan fragment: 2ꢀmethylꢀ4,6ꢀdinitrobenꢀ
zo[b]furan (2a) can enter into reactions characteristic of
an activated methyl group. For example, heating of comꢀ
pound 2a with dimethylformamide dimethyl acetal gave
the corresponding enamine 7 (see Scheme 5), which is a
suitable precursor of various polyfunctional derivatives.31
An important approach to functionalization of diꢀ
nitrobenzofurans 2 could involve their reduction to
aminonitrobenzo[b]furans followed by various transforꢀ
mations of the amino group yielding new nitrobenzoꢀ
furans.
When we used standard systems for reduction of an
aromatic nitro group (NH2NH2•H2O + catalysts, Fe in
an acidic medium, and SnCl2) in amounts required to
reduce only one group, the reduction of dinitrobenzoꢀ
furans 2 proceeded nonselectively to give a difficultꢀtoꢀ
separate mixture of aminonitrobenzofurans 8 and 8´ in all
cases (1H NMR data) (Scheme 6). For this reason, we
followed an alternative route to aminonitrobenzofurans,
namely, acidꢀcatalyzed cyclization of Oꢀ(3ꢀaminoꢀ5ꢀ
nitrophenyl) ketoximes obtained by reduction of one niꢀ
tro group in Oꢀ(3,5ꢀdinitrophenyl) ketoximes 1.
plings between the methyl protons in position 3 and the
H(3´) and H(5´) protons of the thiol substituent. In the
other cases, the RS fragment was located by comparing
the 1H NMR spectra. The displacement of only one nitro
group was confirmed by the 1H NMR spectra of the crude
reaction product.
However, other anionic nucleophiles (phenols and fluꢀ
orinated alcohols in the presence of bases, as well as NaN3)
are unable to displace an NO2 group from dinitroꢀ
benzofurans 2: no displacement occurred in NMP or
DMF below 100 °C, while at higher temperatures, dinitroꢀ
benzofurans 2 decomposed. In this respect, dinitroꢀ
benzofurans differ substantially from 4,6ꢀdinitrobenꢀ
zo[b]thiophenes, which react under mild conditions not
only with thiols but also with other anionic nucleophiles
to give products of displacement of the 4ꢀNO2 group.29,30
Apparently, the πꢀabundance of the benzo[b]furan
system under study is much higher than that of the
benzo[b]thiophene analog.
With 2ꢀmethylꢀ4,6ꢀdinitrobenzo[b]furan (2a) as an exꢀ
ample, we studied the reactivities of dinitrobenzofurans
Scheme 5

Nitrobenzo[b]furans and nitroindoles
Russ.Chem.Bull., Int.Ed., Vol. 56, No. 5, May, 2007
1023
Scheme 6
ferent patterns of fragmentation. The mixture was sepaꢀ
rated because the products are differently soluble in the
reaction mixture (the total yields were 55—70%). We idenꢀ
tified one product as substituted 6ꢀaminoꢀ4ꢀnitrobenꢀ
zo[b]furan 8 (Scheme 8) and confirmed its structure by
1H NMR spectroscopy: the NOE experiment revealed a
coupling between the NH2 protons and the H(5) and
H(7) protons of the nitrobenzene ring. Unexpectedly, the
other product was identified as substituted 4ꢀhydroxyꢀ6ꢀ
nitroindole 10 (see Scheme 8): its 1H NMR spectrum
shows characteristic signals for the NH group of the inꢀ
dole ring (δ 12.15) and for the OH group of the nitrobenꢀ
zene ring (δ 10.4). The NOE experiment revealed couꢀ
plings between the OH proton and the H(5) proton of the
nitrobenzene fragment and between the NH proton in the
indole ring and the H(7) proton of the nitrobenzene fragꢀ
ment. The presence of an OH group was also proved
chemically: indoles 10 are highly soluble in dilute aqueous
alkali (indoles even with two nitro groups in the benzene
ring32 were found to be insoluble in dilute aqueous alkali
at ambient temperature)*.
Scheme 8
R = H, Ar = Ph (1b, 9a); R = H, Ar = 4ꢀClC6H4 (1p, 9b);
R = H, Ar = 2ꢀClC6H4 (1q, 9c); R = H, Ar = 2ꢀMeOC6H4 (1h, 9d);
R = Me, Ar = Ph (1o, 9e)
i. HCl (conc.), EtOH, ∆.
Selective reduction of Oꢀ(3,5ꢀdinitrophenyl) ketꢀ
oximes 1 with hydrazine hydrate in the presence of FeCl3
and activated carbon proceeded smoothly to give
Oꢀ(3ꢀaminoꢀ5ꢀnitrophenyl) ketoximes 9 (see Scheme 6).
It is worth noting that cyclization of ketoximes 9 can
occur in different ways: at the C atom that is ortho to the
NO2 group or at the C atom adjacent to the NH2 group; the
resulting products are 6ꢀaminoꢀ4ꢀnitroꢀ (8) or 4ꢀaminoꢀ
6ꢀnitrobenzo[b]furans (8´), respectively (Scheme 7).
R = H, Ar = Ph (a); R = H, Ar = 4ꢀClC6H4 (b);
R = H, Ar = 2ꢀClC6H4 (c); R = H, Ar = 2ꢀMeOC6H4 (d);
R = Me, Ar = Ph (e)
This unexpected outcome can be explained in terms
of the generally accepted mechanism of cyclization of
Oꢀaryl ketoximes into benzo[b]furans26 (see Scheme 3).
As noted above, the key step of this transformation is an
acidꢀcatalyzed [3,3]ꢀsigmatropic rearrangement of the
enehydroxylamine form of Oꢀaryl oxime (B → C) folꢀ
lowed by aromatization of the sixꢀmembered ring (C → D),
Scheme 7
+
intramolecular addition of the OH group to the C=NH2
bond (D → E), and elimination of the ammonium ion,
leading to benzo[b]furan (E → F) (see Scheme 3).
According to the data obtained, [3,3]ꢀsigmatropic reꢀ
arrangement (B → C) of Oꢀ(3ꢀaminoꢀ5ꢀnitrophenyl)
ketoximes 9 is equally probable at the orthoꢀposition with
respect to both the NO2 and NH2 groups, giving intermeꢀ
diates C´ and C″ and then D´ and D″, respectively
(Scheme 9). Intermediates D´ undergo usual cyclization
into 6ꢀaminoꢀ4ꢀnitrobenzo[b]furans 8 (see Scheme 9,
D´ → E´ → 8). In the case of intermediates D″, the
We found that heating of Oꢀ(3ꢀaminoꢀ5ꢀnitrophenyl)
ketoximes 9 in a mixture of conc. HCl (36%) and ethanol
(1 : 1, v/v) always gives a ~1 : 1 mixture of two products
with the same elemental composition; their mass spectra
contain equal (in mass) peaks of molecular ions with difꢀ
* For the preliminary communication, see Ref. 33.

1024
Russ.Chem.Bull., Int.Ed., Vol. 56, No. 5, May, 2007
Vorob´ev et al.
Scheme 9
+
was added to a mixture of ethanol (10 mL) and 36% HCl (10 mL)
(for 1m—o, AcOH (10 mL) + conc. HCl (4 mL); for 1f,g,
conc. H2SO4 (5 mL) + AcOH (5 mL), the target products being
obtained as sulfates). The reaction mixture was refluxed (for
1f,g, heating at 80 °C) until the starting dinitro compound was
completely consumed (monitoring by TLC with CHCl3 as an
eluent). On cooling to ~20 °C, the precipitate that formed was
filtered off, recrystallized from acetonitrile, and dried in vacuo
(for 2f,g, the reaction mixture was poured into water, the resultꢀ
ing sulfate of 2f or 2g was filtered off, washed with water, dried
in air, and recrystallized from acetonitrile).
2ꢀMethylꢀ4,6ꢀdinitrobenzo[b]furan (2a). Reaction time 6 h,
yield 93%, m.p. 143—144 °C. Found (%): C, 48.42; H, 2.91;
N, 12.23. C9H6N2O5. Calculated (%): C, 48.66; H, 2.72;
N, 12.61. 1H NMR (DMSOꢀd6), δ: 2.65 (s, 3 H); 7.32 (s, 1 H);
8.78, 8.90 (both d, 1 H each, 4J = 1.9 Hz).
intramolecular addition to the C=NH2 bond probably
involves the NH2 group (D″ → G) rather than the
OH group and subsequent elimination of the ammonium
ion produces 4ꢀhydroxyꢀ6ꢀnitroindoles 10 (see Scheme 9,
G → 10). Here the nonionized OH group cannot compete
with the much more nucleophilic NH2 group; otherwise,
we would obtain 4ꢀaminoꢀ6ꢀnitrobenzofurans 8´, which
is not the case.
Analogous results were obtained when cyclization was
carried out in other acid mixtures (MeOH—HCl (conc.),
reflux; MeOH—HCl (gas), reflux; CF3COOH, reflux;
AcONa—AcOH, 80 °C; AcOH—H2SO4, 60 °C; H2SO4,
60 °C; POCl3—benzene, reflux) and a Lewis acid
(ZnCl2—pꢀcresol, 180 °C). In all the cases, the ratio 8 : 10
was ~1 : 1. Cyclization of ketoximes with the proꢀ
tected amino group (Oꢀ(3ꢀacetylaminoꢀ5ꢀnitrophenyl)
and Oꢀ(5ꢀnitroꢀ3ꢀphthalimidophenyl) ketoximes)—in orꢀ
der to make the reaction follow the pathway leading to
aminonitrobenzofuran 8´—gave, as with Oꢀ(3ꢀaminoꢀ5ꢀ
nitrophenyl) ketoximes, a ~1 : 1 mixture of compounds 8
and 10; i.e., the protective group is eliminated under the
reaction conditions before cyclization.
4,6ꢀDinitroꢀ2ꢀphenylbenzo[b]furan (2b). Reaction time 18 h,
yield 95%, m.p. 178—179 °C. Found (%): C, 59.42; H, 2.52;
N, 9.47. C14H8N2O5. Calculated (%): C, 59.16; H, 2.84; N, 9.86.
1H NMR (DMSOꢀd6), δ: 7.57, 8.15 (both m, 3 H each); 8.82,
8.97 (both d, 1 H each, 4J = 2.0 Hz).
2ꢀ(4ꢀBromophenyl)ꢀ4,6ꢀdinitrobenzo[b]furan (2c). Reaction
time 7 h, yield 77%, m.p. 248—249 °C. Found (%): C, 45.98;
H, 1.63; N, 7.92. C14H7BrN2O5. Calculated (%): C, 46.31;
1
H, 1.94; N, 7.71. H NMR (DMSOꢀd6), δ: 7.75, 8.07 (both d,
Thus, we discovered that Oꢀaryl ketoximes containing
a metaꢀamino group in the aryl fragment undergo inꢀ
tramolecular cyclization into 4ꢀhydroxyindoles rather than
benzo[b]furans as always reported for this cyclization.
2 H each, 3J = 8.0 Hz); 8.17 (s, 1 H); 8.85, 8.97 (both d,
4
1 H each, J = 2.0 Hz).
2ꢀ(4ꢀFluorophenyl)ꢀ4,6ꢀdinitrobenzo[b]furan (2d). Reaction
time 6 h, yield 92%, m.p. 214—215 °C. Found (%): C, 55.87;
H, 2.11; N, 9.52. C14H7FN2O5. Calculated (%): C, 55.64;
1
3
Experimental
H, 2.33; N, 9.27. H NMR (DMSOꢀd6), δ: 7.40 (t, 2 H, J =
3
7.8 Hz); 8.05 (s, 1 H); 8.17 (t, 2 H, J = 7.8 Hz); 8.80, 8.95
1
4
H NMR spectra were recorded on a Bruker ACꢀ250 specꢀ
(both d, 1 H each, J = 2.1 Hz).
trometer. Mass spectra (EI) were recorded on a Kratos MSꢀ30
instrument (the spectra of all compounds showed a molecular
ion peak [M]+). The course of the reaction was monitored by
TLC on Silufol UVꢀ254 plates.
Oꢀ(3,5ꢀDinitrophenyl) ketoximes 1a—q were prepared acꢀ
cording to a known procedure.14
2ꢀ(3,4ꢀMethylenedioxyphenyl)ꢀ4,6ꢀdinitrobenzo[b]furan
(2e). Reaction time 4 h, yield 86%, m.p. 268—269 °C.
Found (%): C, 56.01; H, 3.11; N, 8.22. C16H10N2O7. Calcuꢀ
lated (%): C, 56.15; H, 2.94; N, 8.18. 1H NMR (DMSOꢀd6), δ:
6.15 (s, 2 H); 7.10 (d, 1 H); 7.61 (s, 2 H); 7.95 (s, 1 H); 8.82,
8.87 (both d, 1 H each, 4J = 2.0 Hz).
Synthesis of 4,6ꢀdinitrobenzo[b]furans 2a—o (general proceꢀ
dure). Appropriate Oꢀ(3,5ꢀdinitrophenyl) ketoxime 1 (0.01 mol)
4,6ꢀDinitroꢀ2ꢀ(4ꢀpyridyl)benzo[b]furan (2f). Reaction
time 3 h, yield 88% (as sulfate), m.p. 162—163 °C. Found (%):

Nitrobenzo[b]furans and nitroindoles
Russ.Chem.Bull., Int.Ed., Vol. 56, No. 5, May, 2007
1025
C, 41.01; H, 2.12; N, 10.43; S, 8.54. C13H9N3O9S. Calcuꢀ
lated (%): C, 40.74; H, 2.37; N, 10.96; S, 8.37. 1H NMR
(DMSOꢀd6), δ: 8.03 (d, 2 H, 3J = 8.0 Hz); 8.40 (s, 1 H); 8.79 (d,
2 H, 3J = 8.0 Hz); 8.85, 9.07 (both d, 1 H each, 4J = 2.0 Hz).
4,6ꢀDinitroꢀ2ꢀ(2ꢀpyridyl)benzo[b]furan (2g). Reaction
time 10 h, yield 72% (as sulfate), m.p. 174—175 °C. Found (%):
C, 41.12; H, 2.68; N, 11.32; S, 8.77. C13H9N3O9S. Calcuꢀ
lated (%): C, 40.74; H, 2.37; N, 10.96; S, 8.37. 1H NMR
K2CO3 (0.207 g, 1.5 mmol) in NMP (10 mL). The reaction
mixture was stirred at 70 °C until the dinitro compound was
completely consumed (monitoring by TLC with CHCl3 as an
eluent) and poured into ice water (50 mL). The precipitate that
formed was filtered off and washed with water (2×10 mL). For
products 3a,b,d,e,g, the precipitate was dissolved in chloroform
(25 mL) and filtered through a short column with silica gel
(for 3i, the volume of chloroform was 30 mL). The solution was
twice washed with water and the organic layer was separated,
dried over MgSO4, and evaporated to dryness. The precipitate
was recrystallized from glacial acetic acid.
2ꢀMethylꢀ6ꢀnitroꢀ4ꢀ(phenylthio)benzo[b]furan (3a). Reacꢀ
tion time 2 h, yield 26%, m.p. 160—162 °C. Found (%): C, 63.01;
H, 4.01; N, 4.78. C15H11NO3S. Calculated (%): C, 63.14;
H, 3.89; N, 4.91. 1H NMR (DMSOꢀd6), δ: 2.52 (s, 3 H); 6.55 (s,
1 H); 7.55—7.25 (m, 5 H); 8.85, 9.10 (both s, 1 H each).
6ꢀNitroꢀ2ꢀphenylꢀ4ꢀ(phenylthio)benzo[b]furan (3b). Reaction
time 4 h, yield 29%, m.p. 110—112 °C. Found (%): 69.01;
H, 3.91; N, 3.92. C20H13NO3S. Calculated (%): C, 69.15;
H, 3.77; N, 4.03. 1H NMR (DMSOꢀd6), δ: 7.40—8.65 (m, 9 H);
7.75 (s, 1 H); 8.95—7.95 (m, 2 H); 8.41 (s, 1 H).
3
(DMSOꢀd6), δ: 7.53 (t, 1 H, J = 8.0 Hz); 8.10 (m, 3 H); 8.75
(m, 1 H); 8.83, 9.02 (both d, 1 H each, 4J = 1.9 Hz).
2ꢀ(2ꢀMethoxyphenyl)ꢀ4,6ꢀdinitrobenzo[b]furan (2h). Reacꢀ
tion time 8 h, yield 80%, m.p. 227—228 °C. Found (%): C, 57.12;
H, 3.27; N, 9.25. C15H10N2O6. Calculated (%): C, 57.33;
H, 3.21; N, 8.91. 1H NMR (DMSOꢀd6), δ: 4.10 (s, 3 H); 7.21 (t,
3
1 H, 3J = 7.8 Hz); 7.32 (d, 1 H, 3J = 8.0 Hz); 7.58 (t, 1 H, J =
8.0 Hz); 7.90 (s, 1 H); 8.05 (d, 1 H, J = 7.0 Hz); 8.82, 8.95
(both d, 1 H each, 4J = 2.0 Hz).
2ꢀ(2,5ꢀDimethoxyphenyl)ꢀ4,6ꢀdinitrobenzo[b]furan (2i). Reꢀ
action time 8 h, yield 84%, m.p. 252—253 °C. Found (%):
C, 56.04; H, 3.21; N, 8.45. C16H12N2O7. Calculated (%):
C, 55.82; H, 3.51; N, 8.14. 1H NMR (DMSOꢀd6), δ: 3.85, 4.07
(both s, 3 H each); 7.25 (d, 2 H, 3J = 8.0 Hz); 7.51, 7.93 (both s,
3ꢀMethylꢀ6ꢀnitroꢀ2ꢀphenylꢀ4ꢀ(phenylthio)benzo[b]furan
(3c). Reaction time 3.5 h, yield 41%, m.p. 147—149 °C.
Found (%): C, 69.47; H, 4.31; N, 4.05. C21H15NO3S. Calcuꢀ
lated (%): C, 69.79; H, 4.18; N, 3.88. 1H NMR (DMSOꢀd6), δ:
2.62 (s, 3 H); 7.40—7.65 (m, 8 H); 7.72 (s, 1 H); 7.80—7.85
(m, 2 H); 8.41 (s, 1 H).
4
1 H each); 8.83, 9.02 (both d, 1 H each, J = 1.9 Hz).
2ꢀ(4ꢀHydroxyphenyl)ꢀ4,6ꢀdinitrobenzo[b]furan (2j). Reaction
time 12 h, yield 58%, m.p. 271—272 °C. Found (%): C, 56.35;
H, 2.61; N, 9.81. C14H8N2O6. Calculated (%): C, 56.01; H, 2.69;
1
3
N, 9.33. H NMR (DMSOꢀd6), δ: 6.95 (d, 2 H, J = 8.0 Hz);
3
7.81 (s, 1 H); 7.93 (d, 2 H, J = 8.0 Hz); 8.80, 8.84 (both d,
1 H each, J = 2.0 Hz); 10.30 (s, 1 H).
4ꢀ(Benzylthio)ꢀ2ꢀmethylꢀ6ꢀnitrobenzo[b]furan (3d). Reaction
time 2 h, yield 35%, m.p. 80—82 °C. Found (%): C, 64.01;
H, 4.57; N, 4.34. C16H13NO3S. Calculated (%): C, 64.20;
4
2ꢀ(2ꢀFuryl)ꢀ4,6ꢀdinitrobenzo[b]furan (2k). Reaction time 5 h,
yield 75%, m.p. 160—161 °C. Found (%): C, 52.33; H, 2.01;
N, 10.66. C12H6N2O6. Calculated (%): C, 52.57; H, 2.21;
N, 10.22. 1H NMR (DMSOꢀd6), δ: 6.84 (m, 1 H); 7.48 (d, 1 H,
J = 5.0 Hz); 7.77, 8.09 (both s, 1 H each); 8.87, 8.98 (both d,
1
H, 4.38; N, 4.68. H NMR (DMSOꢀd6), δ: 2.55 (s, 3 H); 4.45
(s, 2 H); 6.80 (m, 1 H); 7.21—7.43 (m, 5 H); 8.00, 8.30 (both s,
1 H each).
4ꢀ(Benzylthio)ꢀ6ꢀnitroꢀ2ꢀphenylbenzo[b]furan (3e). Reaction
time 8 h, yield 57%, m.p. 111—124 °C. Found (%): C, 69.97;
H, 4.45; N, 3.54. C21H15NO3S. Calculated (%): C, 69.79;
H, 4.18; N, 3.88. 1H NMR (DMSOꢀd6), δ: 4.48 (s, 2 H);
7.20—7.62 (m, 9 H); 7.92—8.50 (m, 3 H); 8.32 (s, 1 H).
4ꢀ(Benzylthio)ꢀ3ꢀmethylꢀ6ꢀnitroꢀ2ꢀphenylbenzo[b]furan (3f).
Reaction time 3.2 h, yield 80%, m.p. 122—124 °C. Found (%):
C, 70.00; H, 4.65; N, 3.94. C22H17NO3S. Calculated (%):
C, 70.38; H, 4.56; N, 3.73. 1H NMR (DMSOꢀd6), δ: 2.62
(s, 3 H); 4.45 (s, 2 H); 7.25—7.80 (m, 10 H); 7.96, 8.27 (both s,
1 H each).
4ꢀ(4ꢀChlorophenylthio)ꢀ2ꢀmethylꢀ6ꢀnitrobenzo[b]furan (3g).
Reaction time 2 h, yield 17%, m.p. 146—148 °C. Found (%):
C, 56.47; H, 3.25; N, 4.68. C15H10ClNO3S. Calculated (%):
C, 56.34; H, 3.15; N, 4.38. 1H NMR (DMSOꢀd6), δ: 2.67
(s, 3 H); 6.61 (m, 1 H); 7.31—7.60 (m, 4 H); 8.85, 9.10 (both s,
1 H each).
4ꢀ(4ꢀChlorophenylthio)ꢀ6ꢀnitroꢀ2ꢀphenylbenzo[b]furan (3h).
Reaction time 4 h, yield 39%, m.p. 187—188 °C. Found (%):
C, 63.09; H, 3.04; N, 3.81. C20H12ClNO3S. Calculated (%):
C, 62.91; H, 3.17; N, 3.67. 1H NMR (DMSOꢀd6), δ: 7.45—7.61
(m, 8 H); 7.92 (s, 1 H); 8.00—8.05 (m, 2 H); 8.50 (s, 1 H).
4ꢀ(4ꢀChlorophenylthio)ꢀ3ꢀmethylꢀ6ꢀnitroꢀ2ꢀphenylbenꢀ
zo[b]furan (3i). Reaction time 4.5 h, yield 30%, m.p.
137—139 °C. Found (%): C, 63.45; H, 3.34; N, 3.24.
C21H14ClNO3S. Calculated (%): C, 63.72; H, 3.56; N, 3.54.
1H NMR (DMSOꢀd6), δ: 2.60 (s, 3 H); 7.40—7.65 (m, 7 H);
7.80—7.86 (m, 2 H); 7.82, 8.50 (both s, 1 H each).
4
1 H each, J = 1.9 Hz).
4,6ꢀDinitroꢀ2ꢀ(2ꢀthienyl)benzo[b]furan (2l). Reaction
time 6 h, yield 80%, m.p. 165—166 °C. Found (%): C, 50.35;
H, 2.18; N, 9.21. C12H6N2O5S. Calculated (%): C, 49.66;
1
H, 2.08; N, 9.65. H NMR (DMSOꢀd6), δ: 7.24 (t, 1 H, J =
4.0 Hz); 7.72 (s, 1 H); 7.92 (m, 2 H); 8.71, 8.80 (both d, 1 H each,
4J = 1.9 Hz).
7,9ꢀDinitroꢀ1,2,3,4ꢀtetrahydrodibenzofuran (2m). Reaction
time 6 h, yield 85%, m.p. 102 °C. Found (%): C, 55.21; H, 4.01;
N, 10.25. C12H10N2O5. Calculated (%): C, 54.97; H, 3.84;
N, 10.68. 1H NMR (DMSOꢀd6), δ: 1.89, 2.84 (both m,
4
4 H each); 8.70, 8.85 (both d, 1 H each, J = 2.0 Hz).
3ꢀMethylꢀ7,9ꢀdinitroꢀ1,2,3,4ꢀtetrahydrodibenzofuran (2n).
Reaction time 9 h, yield 71%, m.p. 88 °C. Found (%): C, 56.68;
H, 4.11; N, 10.05. C13H12N2O5. Calculated (%): C, 56.52;
H, 4.38; N, 10.14. 1H NMR (DMSOꢀd6), δ: 1.10 (d, 3 H); 1.50
(m, 1 H); 1.95 (m, 2 H); 2.35 (m, 1 H); 2.90 (m, 3 H); 8.62, 8.75
(both d, 1 H each, 4J = 2.0 Hz).
3ꢀMethylꢀ4,6ꢀdinitroꢀ2ꢀphenylbenzo[b]furan (2o). Reaction
time 6 h, yield 73%, m.p. 151—152 °C. Found (%): C, 60.59;
H, 3.56; N, 9.01. C15H10N2O5. Calculated (%): C, 60.41;
1
H, 3.38; N, 9.39. H NMR (DMSOꢀd6), δ: 2.42 (s, 3 H); 7.62
(m, 3 H); 7.85 (m, 2 H); 8.70, 8.85 (both d, 1 H each,
4J = 2.0 Hz).
Synthesis of 4ꢀSRꢀ6ꢀnitrobenzo[b]furans 3a—i (general proꢀ
cedure). An appropriate thiol (1.5 mmol) was added under niꢀ
trogen to a stirred mixture of dinitrobenzofuran 2 (1 mmol) and

1026
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Vorob´ev et al.
2ꢀMethylꢀ3,4,6ꢀtrinitrobenzo[b]furan (4). 2ꢀMethylꢀ4,6ꢀdiꢀ
nitrobenzo[b]furan (2a) (2.22 g, 0.01 mol) was added at 10 °C to
a vigorously stirred mixture of fuming HNO3 (0.5 mL) and H2SO4
(4.5 mL). After 20 min, the reaction mixture was poured into ice
water (50 mL) and the resulting precipitate was filtered off, washed
with water (2×10 mL), and dried in air. The yield was 79%, m.p.
150—152 °C. Found (%): C, 40.21; H, 1.95; N, 15.95. C9H5N3O7.
Calculated (%): C, 40.46; H, 1.89; N, 15.73. 1H NMR (CDCl3),
δ: 2.95 (s, 3 H); 8.64, 8.85 (both s, 1 H each).
3ꢀChlorosulfonylꢀ2ꢀmethylꢀ4,6ꢀdinitrobenzo[b]furan (5).
2ꢀMethylꢀ4,6ꢀdinitrobenzo[b]furan (2a) (1 g, 4.5 mmol) was
added at 6 °C to ClSO3H (30 mmol, 6 mL). The reaction mixꢀ
ture was allowed to warm to ~20 °C, kept for an additional
40 min, and poured onto ice (50 mL). The resulting precipitate
was filtered off, washed with water to neutral reaction, and dried
in air. The yield was 72%, m.p. 198—200 °C. Found (%):
C, 33.45; H, 1.57; Cl, 11.21; N, 8.21; S, 10.32. C9H5ClN2O7S.
Calculated (%): C, 33.71; H, 1.57; Cl, 11.06; N, 8.74; S, 10.00.
4ꢀ(2ꢀMethylꢀ4,6ꢀdinitrobenzo[b]furanꢀ3ꢀylsulfonyl)morphoꢀ
line (6). Morpholine (4 mL, 4.6 mmol) was added to comꢀ
pound 5 (0.73 g, 2.3 mmol) in stirred acetonitrile (5 mL). The
reaction mixture was kept for 1.5 h. The precipitate that formed
was filtered off and recrystallized from a minimum amount of
acetonitrile. The yield was 66%, m.p. 221—223 °C. Found (%):
C, 42.21; H, 3.42; N, 11.01. C13H13N3O8S. Calculated (%):
C, 42.05; H, 3.53; N, 11.32. 1H NMR (DMSOꢀd6), δ:
3.10—3.20, 3.60—3.70 (both m, 4 H each); 8.85, 9.00 (both s,
1 H each).
Oꢀ(3ꢀAminoꢀ5ꢀnitrophenyl)ꢀ1ꢀ(2ꢀchlorophenyl)ethanone
oxime (9c). Reaction time 8 h, yield 50%, m.p. 136—138 °C.
Found (%): C, 54.78; H, 3.98; Cl, 11.24; N, 13.62.
C14H12ClN3O3. Calculated (%): C, 55.00; H, 3.96; Cl, 11.60;
N, 13.74. 1H NMR (DMSOꢀd6), δ: 2.45 (s, 3 H); 5.91 (s, 2 H);
6.85 (s, 1 H); 7.08—7.15 (m, 2 H); 7.46—7.64 (m, 4 H).
Oꢀ(3ꢀAminoꢀ5ꢀnitrophenyl)ꢀ1ꢀ(2ꢀmethoxyphenyl)ethanone
oxime (9d). Reaction time 7 h, yield 71%, m.p. 146—147 °C.
Found (%): C, 59.97; H, 5.12; N, 13.47. C15H15N3O4. Calcuꢀ
lated (%): C, 59.79; H, 5.02; N, 13.95. 1H NMR (DMSOꢀd6), δ:
2.32, 3.83 (both s, 3 H each); 5.88 (s, 2 H); 6.82 (s, 1 H);
6.95—7.18 (m, 4 H); 7.30—7.55 (m, 2 H).
Oꢀ(3ꢀAminoꢀ5ꢀnitrophenyl)ꢀ1ꢀphenylpropanꢀ1ꢀone oxime
(9e). Reaction time 3 h, yield 68%, m.p. 188—192 °C.
Found (%): C, 63.45; H, 5.49; N, 14.26. C15H15N3O3. Calcuꢀ
lated (%): C, 63.15; H, 5.30; N, 14.73. 1H NMR (DMSOꢀd6), δ:
3
3
1.15 (t, 3 H, J = 7.0 Hz); 2.92 (q, 2 H, J = 7.0 Hz); 5.92
(s, 2 H); 6.91 (s, 1 H); 7.10—7.16 (m, 2 H); 7.45—7.56 (m, 3 H);
7.71—7.87 (m, 2 H).
Synthesis of 6ꢀaminoꢀ4ꢀnitrobenzofurans 8a—e and 4ꢀhydrꢀ
oxyꢀ6ꢀnitroindoles 10a—e (general procedure). An appropriate
Oꢀ(3ꢀaminoꢀ5ꢀnitrophenyl) oxime 9 (0.01 mol) was added to a
mixture of ethanol (10 mL) and 36% HCl (10 mL). The reaction
mixture was refluxed until the starting aminonitro compound
was completely consumed (monitoring by TLC with CHCl3 as
an eluent). On cooling to ~20 °C, the precipitate that formed
was filtered off and neutralized in water (50 mL) with aqueous
ammonia to weakly basic reaction. The precipitate of 6ꢀaminoꢀ
4ꢀnitrobenzofuran 8 was filtered off and dried in vacuo. The
filtrate was evaporated to dryness and the residue was neutralꢀ
ized in water (50 mL) with aqueous ammonia to weakly basic
reaction. The precipitate of 4ꢀhydroxyꢀ6ꢀnitroindole 10 was filꢀ
tered off, recrystallized from a minimum amount of ethanol,
and dried in vacuo.
2ꢀ(2ꢀDimethylaminoethenyl)ꢀ4,6ꢀdinitrobenzo[b]furan (7).
A mixture of 2ꢀmethylꢀ4,6ꢀdinitrobenzo[b]furan (2a) (0.51 g,
2.3 mmol) and dimethylformamide dimethyl acetal (4 mL) was
refluxed for 2.5 h (monitoring by TLC with CHCl3 as an eluꢀ
ent). The reaction mixture was cooled, diluted with light petroꢀ
leum, and filtered. The yield was 80%, m.p. 152—154 °C.
Found (%): C, 52.31; H, 3.74; N, 15.37. C12H11N3O5. Calcuꢀ
lated (%): C, 51.99; H, 4.00; N, 15.16. 1H NMR (DMSOꢀd6), δ:
3.10 (s, 6 H); 5.40 (d, 1 H, 3J = 16.1 Hz); 7.00 (s, 1 H); 7.90 (d,
1 H, 3J = 16.1 Hz); 8.30, 8.73 (both s, 1 H each).
6ꢀAminoꢀ4ꢀnitroꢀ2ꢀphenylbenzo[b]furan (8a). Reaction
time 2 h, yield 38%, m.p. 192—194 °C. Found (%): C, 66.03;
H, 3.95; N, 11.29. C14H10N2O3. Calculated (%): C, 66.14;
1
H, 3.94; N, 11.02. H NMR (DMSOꢀd6), δ: 5.88 (s, 2 H); 7.18
Synthesis of Oꢀ(3ꢀaminoꢀ5ꢀnitrophenyl) ketoximes 9a—e
(general procedure). Hydrazine hydrate (10 mL, 0.2 mol) was
added to a mixture of an appropriate Oꢀ(3,5ꢀdinitrophenyl)
ketoxime 1 (0.1 mol), FeCl3•6H2O (0.13 g, 0.5 mmol), and
activated carbon (6 g) in methanol (700 mL). The reaction
mixture was refluxed until the starting dinitro compound was
completely consumed (monitoring by TLC with CHCl3 as an
eluent) and filtered hot. The carbon was washed with hot methaꢀ
nol (2×50 mL), the filtrate was cooled to 4 °C, and the precipiꢀ
tate that formed was filtered off.
Oꢀ(3ꢀAminoꢀ5ꢀnitrophenyl)ꢀ1ꢀphenylethanone oxime (9a).
Reaction time 3 h, yield 72%, m.p. 157—159 °C. Found (%):
C, 62.12; H, 4.95; N, 15.84. C14H13N3O3. Calculated (%):
C, 61.99; H, 4.83; N, 15.49. 1H NMR (DMSOꢀd6), δ: 2.45
(s, 3 H); 5.92 (s, 2 H); 6.92 (s, 1 H); 7.10—7.22 (m, 2 H);
7.45—7.55 (m, 3 H); 7.76—7.90 (m, 2 H).
Oꢀ(3ꢀAminoꢀ5ꢀnitrophenyl)ꢀ1ꢀ(4ꢀchlorophenyl)ethanone
oxime (9b). Reaction time 7 h, yield 60%, m.p. 155—157 °C.
Found (%): C, 54.65; H, 3.59; Cl, 11.72; N, 13.58.
C14H12ClN3O3. Calculated (%): C, 55.00; H, 3.96; Cl, 11.60;
N, 13.74. 1H NMR (DMSOꢀd6), δ: 2.43 (s, 3 H); 5.91 (s, 2 H);
6.89 (s, 1 H); 7.10—7.18 (m, 2 H); 7.55, 7.65 (both d, 2 H each,
3J = 8.0 Hz).
(s, 1 H); 7.32—7.61 (m, 4 H); 7.68 (s, 1 H); 7.75—8.11 (m, 2 H).
4ꢀHydroxyꢀ6ꢀnitroꢀ2ꢀphenylindole (10a). Reaction time 2 h,
yield 24%, m.p. 183—185 °C. Found (%): C, 66.20; H, 3.83;
N, 10.96. C14H10N2O3. Calculated (%): C, 66.14; H, 3.94;
N, 11.02. 1H NMR (DMSOꢀd6), δ: 7.10, 7.22 (both s, 1 H each);
7.31—7.42 (m, 1 H); 7.45—7.58 (m, 2 H); 7.75—8.00 (m, 3 H);
10.40, 12.15 (both s, 1 H each).
6ꢀAminoꢀ2ꢀ(4ꢀchlorophenyl)ꢀ4ꢀnitrobenzo[b]furan (8b). Reꢀ
action time 3 h, yield 31%, m.p. 278—280 °C. Found (%):
C, 57.67; H, 4.17; Cl, 12.13; N, 9.62. C14H9ClN2O3. Calcuꢀ
lated (%): C, 57.63; H, 4.12; Cl, 12.17; N, 9.61. 1H NMR
(DMSOꢀd6), δ: 5.90 (s, 2 H); 7.15 (s, 1 H); 7.45—7.60 (m, 3 H);
7.68 (s, 1 H); 7.89 (d, 2 H, 3J = 8.0 Hz).
2ꢀ(4ꢀChlorophenyl)ꢀ4ꢀhydroxyꢀ6ꢀnitroindole (10b). Reaction
time 3 h, yield 36%, m.p. 232—234 °C. Found (%): C, 57.55;
H, 4.11; Cl, 12.22; N, 9.62. C14H9ClN2O3. Calculated (%):
C, 57.63; H, 4.12; Cl, 12.17; N, 9.61. 1H NMR (DMSOꢀd6), δ:
3
7.10, 7.27 (both s, 1 H each); 7.58 (d, 2 H, J = 8.0 Hz); 7.86
(s, 1 H); 7.92 (d, 2 H, 3J = 8.0 Hz); 10.49, 12.32 (both s,
1 H each).
6ꢀAminoꢀ2ꢀ(2ꢀchlorophenyl)ꢀ4ꢀnitrobenzo[b]furan (8c). Reꢀ
action time 2 h, yield 27%, m.p. 178—182 °C. Found (%):
C, 57.54; H, 4.18; N, 9.62. C14H9ClN2O3. Calculated (%):

Nitrobenzo[b]furans and nitroindoles
Russ.Chem.Bull., Int.Ed., Vol. 56, No. 5, May, 2007
1027
C, 57.63; H, 4.12; N, 9.61. 1H NMR (DMSOꢀd6), δ: 6.00
(s, 2 H); 7.09, 7.21, 7.29 (all s, 1 H each); 7.45—7.56 (m, 3 H);
7.52—7.59 (m, 1 H).
tion. The Chemistry of Anionic SigmaꢀComplexes, Elsevier,
New York, 1984.
8. F. Terrier, Nucleofilic Aromatic Displacement. The Influence
of the Nitro Group, VCH Publ., New York, 1991.
9. S. A. Shevelev, M. D. Dutov, I. A. Vatsadze, O. V.
Serushkina, A. L. Rusanov, and M. A. Andrievskii, Mendeleev
Commun., 1995, 157.
10. S. A. Shevelev, M. D. Dutov, I. A. Vatsadze, M. A. Korolev,
and A. L. Rusanov, Mendeleev Commun., 1996, 155.
11. S. A. Shevelev, M. D. Dutov, M. A. Korolev, O. Yu.
Sapozhnikov, and A. L. Rusanov, Mendeleev Commun.,
1998, 69.
12. S. A. Shevelev, M. D. Dutov, and O. V. Serushkina, Izv.
Akad. Nauk, Ser. Khim., 1995, 2528 [Russ. Chem. Bull., 1995,
44, 2424 (Engl. Transl.)].
13. O. Yu. Sapozhnikov, M. D. Dutov, M. A. Korolev, V. V.
Kachala, and S. A. Shevelev, Mendeleev Commun., 2001, 232.
14. S. A. Shevelev, I. A. Vatsadze, and M. D. Dutov, Mendeleev
Commun., 2002, 196.
15. M. D. Dutov, I. A. Vatsadze, S. S. Vorob´ev, and S. A.
Shevelev, Mendeleev Commun., 2005, 202.
16. D. V. Davydov and I. P. Beletskaya, Izv. Akad. Nauk, Ser.
Khim., 1995, 1393 [Russ. Chem. Bull., 1995, 44, 1344 (Engl.
Transl.)].
17. P. P. Onys´ko, N. V. Proklina, V. P. Prokopenko, and Yu. G.
Gololobov, Zh. Org. Khim., 1987, 23, 606 [J. Org. Chem.
USSR, 1987, 23 (Engl. Transl.)].
18. T. Severin, R. Schmitz, and H. Temme, Chem. Ber., 1964,
97, 467.
2ꢀ(2ꢀChlorophenyl)ꢀ4ꢀhydroxyꢀ6ꢀnitroindole (10c). Reaction
time 2 h, yield 21%, m.p. 226—228 °C. Found (%): C, 57.71;
H, 4.04; N, 9.63. C14H9ClN2O3. Calculated (%): C, 57.63;
1
H, 4.12; N, 9.61. H NMR (DMSOꢀd6), δ: 7.06, 7.29 (both d,
1 H each, 4J = 1.8 Hz); 7.51—7.60 (m, 2 H); 7.65, 7.85 (both dd,
1 H each, 3J = 7.9 Hz, 4J = 2.0 Hz); 7.91 (d, 1 H); 10.40, 12.15
(both s, 1 H each).
6ꢀAminoꢀ2ꢀ(2ꢀmethoxyphenyl)ꢀ4ꢀnitrobenzo[b]furan (8d).
Reaction time 2 h, yield 36%, m.p. 212—214 °C. Found (%):
C, 63.35; H, 4.26; N, 9.88. C15H12N2O4. Calculated (%):
C, 63.38; H, 4.23; N, 9.85. 1H NMR (DMSOꢀd6), δ: 4.00
3
(s, 3 H); 5.58 (s, 2 H); 7.09 (t, 1 H, J = 8.0 Hz); 7.15—7.27
(m, 2 H); 7.41 (t, 1 H, 3J = 8.0 Hz); 7.52, 7.64 (both s, 1 H each);
7.90 (d, 1 H, 3J = 8.0 Hz).
4ꢀHydroxyꢀ2ꢀ(2ꢀmethoxyphenyl)ꢀ6ꢀnitroindole (10d). Reacꢀ
tion time 2 h, yield 21%, m.p. 252—254 °C. Found (%): C, 63.42;
H, 4.19; N, 9.90. C15H12N2O4. Calculated (%): C, 63.38;
H, 4.23; N, 9.85. 1H NMR (DMSOꢀd6), δ: 3.97 (s, 3 H);
7.02—7.25 (m, 4 H); 7.30—7.47, 7.78—7.88 (both m, 1 H each);
7.98, 10.32, 11.79 (all s, 1 H each).
6ꢀAminoꢀ3ꢀmethylꢀ4ꢀnitroꢀ2ꢀphenylbenzo[b]furan (8e). Reꢀ
action time 4 h, yield 29%, m.p. 149—150 °C. Found (%):
C, 66.87; H, 4.25; N, 10.77. C15H12N2O3. Calculated (%):
C, 67.16; H, 4.48; N, 10.45. 1H NMR (DMSOꢀd6), δ: 2.32
(s, 3 H); 5.82 (s, 2 H); 7.08, 7.38 (both s, 1 H each); 7.39—7.59
(m, 3 H); 7.65—7.76 (m, 2 H).
4ꢀHydroxyꢀ3ꢀmethylꢀ6ꢀnitroꢀ2ꢀphenylindole (10e). Reaction
time 4 h, yield 37%, m.p. 139—140 °C. Found (%): C, 67.55;
H, 4.40; N, 10.47. C15H12N2O3. Calculated (%): C, 67.16;
19. P. E. Brown and R. A. Lewis, J. Chem. Soc., Perkin Trans. 1,
1992, 573.
20. F. Bordin, R. Bevilacqua, and F. DabbeniꢀSala, Gazz. Chim.
Ital., 1969, 99, 1177.
1
H, 4.48; N, 10.45. H NMR (DMSOꢀd6), δ: 2.60 (s, 3 H); 7.25
(s, 1 H); 7.38—7.46, 7.51—7.58, 7.65—7.71 (all m, 2 H each);
10.37, 11.83 (both s, 1 H each).
21. T. Sheradsky, Tetrahedron Lett., 1966, 5225.
22. T. Sheradsky, J. Heterocycl. Chem., 1967, 4, 413.
23. A. Mooradian and P. Dupont, Tetrahedron Lett., 1967, 407.
24. A. Mooradian and P. Dupont, J. Heterocycl. Chem.,
1967, 4, 441.
This work was financially supported in part by the Interꢀ
national Scientific and Technical Center (Grant 3197p).
25. A. Mooradian and P. Dupont, Tetrahedron Lett., 1967, 2867.
26. P. R. Guzzo, R. N. Buckle, and M. Chou, J. Org. Chem.,
2003, 68, 770.
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in revised form March 14, 2007