Nucleophilic replacement of the nitro group in E-2,4,6-trinitrostilbenes by O- and S-nucleophiles. Synthesis of 2-aryl-4-X-6-nitrobenzo[b]thiophenes

Article abstract of DOI:10.1007/s11172-005-0309-1

The direction of nucleophilic substitution for the nitro group in E-2,4,6-trinitrostilbenes under the action of arene- and alkanethiols or phenols in the presence of inorganic bases was studied. Products of o-NO₂ group replacement in the presen

Full text of DOI:10.1007/s11172-005-0309-1

Russian Chemical Bulletin, International Edition, Vol. 54, No. 3, pp. 711—718, March, 2005
711
Nucleophilic replacement of the nitro group in Eꢀ2,4,6ꢀtrinitrostilbenes
by Oꢀ and Sꢀnucleophiles.
Synthesis of 2ꢀarylꢀ4ꢀXꢀ6ꢀnitrobenzo[b]thiophenes*
ꢀ
O. Yu. Sapozhnikov, V. V. Mezhnev, M. D. Dutov, V. V. Kachala, N. A. Popov, and S. A. Shevelev
N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences,
47 Leninsky prosp., 119991 Moscow, Russian Federation.
Fax: +7 (095) 135 5328. Eꢀmail: shevelev@cacr.ioc.ac.ru
The direction of nucleophilic substitution for the nitro group in Eꢀ2,4,6ꢀtrinitrostilbenes
under the action of areneꢀ and alkanethiols or phenols in the presence of inorganic bases was
studied. Products of oꢀNO2 group replacement in the presence of PhCH2SH were used to
obtain earlier unknown 2ꢀarylꢀ4,6ꢀdinitrobenzo[b]thiophenes and their 3ꢀchloro derivatives.
In these fused heterocycles, the 4ꢀNO2 group can be selectively displaced by a nucleophile.
Key words: benzo[b]thiophenes, Eꢀ2,4,6ꢀtrinitrostilbenes, 2,4,6ꢀtrinitrotoluene, nucleoꢀ
philic substitution for the nitro group, heterocyclization, sulfides, sulfones, nitro compounds.
Scheme 1
The present work was carried out as part of the proꢀ
gram for the study of the chemistry of the explosive
2,4,6ꢀtrinitrotoluene (TNT). The program was intended
to create scientific fundamentals and technologies for use
of TNT as an accessible multipurpose chemical raw maꢀ
terial.2,3 A particular purpose of the program was to synꢀ
thesize polyfunctional benzoannelated heterocycles3 by
modifying the methyl group of TNT with subsequent cyꢀ
clization of the resulting 1ꢀXꢀ2,4,6ꢀtrinitrobenzenes via
intraꢀ or intermolecular replacement of the oꢀNO2 group.
Our systematic investigations of nucleophilic substituꢀ
tion in the series of such 1ꢀXꢀ2,4,6ꢀtrinitrobenzenes
were aimed at finding the possibility of and conditions
for selective replacement of the oꢀNO2 group (e.g., see
Refs 4—9).
It is known that condensation of TNT with aromatic
and heteroaromatic aldehydes smoothly gives the correꢀ
sponding Eꢀ2,4,6ꢀtrinitrostilbenes 1 (see Ref. 7 and referꢀ
ences cited therein). Regiospecific nucleophilic replaceꢀ
ment of the oꢀNO2 group in stilbenes 1 by the action of
NaN3 under mild conditions (20 °C, DMF) has also been
reported7 (Scheme 1).
The goal of the present work was to study the substituꢀ
tion of anionic Sꢀ and Oꢀnucleophiles for a nitro group in
Eꢀ2,4,6ꢀtrinitrostilbenes 1 and to use substitution prodꢀ
ucts for the synthesis of benzoannelated heterocycles.
We found that arenethiols in dipolar aprotic solvents
(Nꢀmethylpyrrolidone (NMP), DMF, DMSO, and acꢀ
etonitrile) react with stilbenes 1 in the presence of alkalis
or alkali metal carbonates even at 20 °C; regardless of
the character of the aryl substituent in stilbenes 1, the
only leaving group was oꢀNO2 and the corresponding
Eꢀ2ꢀarylthioꢀ4,6ꢀdinitrostilbenes 3a—f were obtained in
good yields (Scheme 2). In the absence of bases, the
reaction did not occur. Use of solid K2CO3 in NMP was
found to be optimum for both preparation of the desired
products in high yields and their isolation. The event of
1
orthoꢀsubstitution was proved by H NMR spectroscopy:
the spectra of the reaction products contained two differꢀ
ent signals from the dinitrophenyl fragment, whereas
paraꢀsubstitution would be manifested by a signal of
* For the preliminary communication, see Ref. 1.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 698—705, March, 2005.
1066ꢀ5285/05/5403ꢀ0711 © 2005 Springer Science+Business Media, Inc.

712
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Sapozhnikov et al.
Scheme 3
double intensity. No paraꢀsubstitution product was deꢀ
tected in the reaction mixture (1H NMR data).
Scheme 2
a
b
c
d
e
f
R
H
Cl
OMe
CF3
H
OMe
Alk CH2Ph CH2Ph
CH2Ph CH2Ph cycloꢀHex cycloꢀHex
Scheme 4
a
H
H
b
Cl
H
c
Cl
Me
d
OMe
H
e
OMe
Me
f
R
R´
CF3
H
The reactions with alkanethiols under the same conꢀ
ditions yielded both possible isomers, the orthoꢀisomer
being dominant: in all cases, the ortho/para ratio was ≈
3/1 (Scheme 3).
We found that phenols in the presence of K2CO3 also
replace the oꢀnitro group in trinitrostilbenes 1; however,
the reaction temperature should be increased to 80 °C
(Scheme 4). Acetonitrile proved to be the optimal solvent
for this reaction (from the viewpoint of isolation of the
product), although the reaction occurred in NMP and
DMF as well. The yields of orthoꢀsubstitution products 5
did not exceed 40%; however, replacement of the pꢀNO2
group was detected in no product (1H NMR data). The
low yields of Eꢀ2ꢀaryloxyꢀ4,6ꢀdinitrostilbenes 5 are due
to intense resinification during the reaction, probably, as
a result of destruction of anionic σꢀH complexes at 80 °C.
Apparently,10,11 the latter form via addition of the phenoꢀ
late anion to the aromatic ring of stilbenes 1 and 5 in the
ortho—paraꢀpositions relative to the nitro groups.
R, R´ = H (a); R = OMe, R´ = Me (b), Cl (c)
for the same reasons as in the case of phenols. The higher
basicity of MeO– compared to PhO– facilitates the forꢀ
mation of anionic σꢀcomplexes.11
A possible explanation of the dominant formation of
the orthoꢀisomer is that the orthoꢀ and paraꢀnitro groups
in Eꢀ2,4,6ꢀtrinitrostilbenes 1, as in other 1ꢀXꢀ2,4,6ꢀtriꢀ
nitrobenzenes, are not equivalent. The AM1 semiempirical
calculation (Chem3D Ultra, 8.0) revealed that in stilbene
1a, the planes of the orthoꢀnitro groups are rotated through
considerable angles about the C—N axis (2ꢀNO2 through
~50° and 6ꢀNO2 through ~30°) under the steric effect of
the βꢀphenylvinyl fragment, while the pꢀNO2 group is
With aliphatic alkoxides (e.g., MeONa in MeOH or
DMF) as Oꢀnucleophiles, substitution products virtually
did not form; only resinification was observed, probably,

Synthesis of 2ꢀarylꢀ4ꢀXꢀ6ꢀnitrobenzo[b]thiophenes Russ.Chem.Bull., Int.Ed., Vol. 54, No. 3, March, 2005
713
coplanar with the aromatic ring; the plane of the βꢀphenylꢀ
vinyl fragment is rotated through ~60° with respect to this
ring (close data were reported earlier7). It is known that
rotation of the oꢀNO2 group in 1ꢀXꢀ2,4,6ꢀtrinitrobenzenes
favors its nucleophilic replacement by facilitating the limꢀ
iting step in the SNArꢀmechanism, namely, the formation
of the corresponding ipsoꢀσꢀcomplex.12,13 At the same
time, strong steric hindrances due to the structure of subꢀ
stituent X and to the character of the nucleophile can
change the direction of the reaction: the content of
paraꢀsubstitution products increases.13,14
compound had been synthesized by oxidation of an
orthoꢀsubstitution product from TNT and benzenethiol
followed by condensation of the resulting 4,6ꢀdinitroꢀ2ꢀ
phenylsulfonyltoluene with benzaldehyde.
Scheme 6
When moving from arenethiols and phenols to alkaneꢀ
thiols, the steric requirements of the nucleophile become
higher, which makes orthoꢀsubstitution less selective. An
analogous effect was observed for TNT,14 although the
content of paraꢀsubstitution products in the case of TNT
was lower than for stilbenes 1.
We studied the possibility of replacing a second
nitro group in stilbene 3a and two nitro groups in
Eꢀ2,4,6ꢀtrinitrostilbene 1a in the presence of benzenethiol
(1 or 2 equivalents, respectively). Reactions were carried
out under the same conditions as for substitution of the
first nitro group (Scheme 5); however, an inert atmoꢀ
sphere was required because the reaction time was much
longer (in both cases, 8 h) and thus benzenethiol could
oxidize into diphenyl sulfide. Both the reactions gave the
sole product identified as orthoꢀdisubstitution one 6
(1H NMR data). The spectrum shows a singlet of double
integrated intensity for the equivalent protons in posiꢀ
tions 3 and 5 of the central phenyl ring. In the case of
paraꢀsubstitution, the spectrum would contain two sigꢀ
nals for the nonequivalent protons in positions 3 and 5.
The reaction of sulfone 7 with benzenethiol in NMP
in the presence of K2CO3 gave compound 8 through reꢀ
placement of the orthoꢀnitro group (see Scheme 6). This
outcome was proved by chemical transformations. Oxiꢀ
dation of both compounds 8 and 6 yielded the same
disulfone 9 (Scheme 7).
Scheme 5
Scheme 7
It is known that when the PhSO2 (one or two) and
NO2 groups are meta to each other in a benzene ring
containing no other substituents, only the nitro group is
replaced in a reaction with PhSH.16 We found this valid
for nitrodisulfone 9 as well, though partial replacement
of the PhSO2 group also occurred (Scheme 8). The prodꢀ
uct contained no starting disulfone 9 (1H NMR data).
The spectra show signals for sulfone 8 and, in addition, a
set of signals corresponding to the double bond and a lowꢀ
field singlet assigned to product 9a; the ratio of comꢀ
Oxidation of sulfide 3a with 30% H2O2 in boiling aceꢀ
tic acid afforded sulfone 7 (Scheme 6). Earlier,15 this

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Sapozhnikov et al.
pounds 9a/8 was ≈ 4/1. Apparently, the presence of the
substituent (PhCH=CH) ortho to PhSO2 makes it more
mobile, though not so mobile as NO2.
were determined by the NOE method. This experiment
revealed an interaction between the H(2) and H(6) proꢀ
tons of the aryl substituent and the proton in position 3 of
the benzothiophene ring. With sulfides 4a,b as examples,
we demonstrated that their reactions with two equivalents
of SO2Cl2 immediately afford 2ꢀarylꢀ3ꢀchloroꢀ4,6ꢀdiꢀ
nitrobenzo[b]thiophenes 13a,b in 70—85% yields. It
turned out that this process involves chlorination of the
initially formed benzothiophenes 12a,b, because the reꢀ
actions of 12a,b with one equivalent of SO2Cl2 under the
same conditions give derivatives 13a,b (Scheme 9).
Apparently, the initially formed orthoꢀsulfenyl chloꢀ
rides 10 undergo cyclization into 2ꢀarylꢀ3ꢀchloroꢀ4,6ꢀ
dinitroꢀ2,3ꢀdihydrobenzo[b]thiophenes 11, which,
through in situ elimination of HCl, yield benzothiophenes
12 (see Scheme 8). Indeed, in the case of sulfide 4c, we
isolated the corresponding 3ꢀchloroꢀ2ꢀ(4ꢀmethoxyꢀ
phenyl)ꢀ4,6ꢀdinitroꢀ2,3ꢀdihydrobenzo[b]thiophene 11c,
which released HCl on prolonged keeping under the reꢀ
action conditions (SO2Cl2, 1,2ꢀdichloroethane, 20 °C) to
give benzothiophene 12c and chlorination products of the
thiophene and paraꢀmethoxyphenyl fragments, which
confirmed our assumption.
Scheme 8
It is known17 that the PhCH2—SAr bond easily underꢀ
goes cleavage in the presence of chlorinating reagents
to give the corresponding arylsulfenyl chlorides and
PhCH2Cl. Such transformations of orthoꢀbenzylthio deꢀ
rivatives 4a—d could be expected to yield products with
an orthoꢀSCl fragment capable of adding to the double
bond in intramolecular cyclization.
For this purpose, unseparated sulfides 4 and 4´ and
were entered into reactions with sulfuryl chloride
in dichloroethane. The reactions between equimolar
amounts of SO2Cl2 and 4 + 4´ gave, even at room temꢀ
perature, earlier unknown 2ꢀarylꢀ4,6ꢀdinitrobenzo[b]thioꢀ
phenes 12a—d (Scheme 9) in 45—70% yields (with reꢀ
spect to sulfide 4). The structures of these compounds
Earlier, an analogous route to benzo[b]thiophenes was
known only with cinnamic acid derivatives. In this case,
aromatization of the initially formed 3ꢀchloroꢀ2,3ꢀdiꢀ
hydrobenzo[b]thiophenes required the use of a base.18
This is unnecessary for the synthesis of 2ꢀarylꢀ4,6ꢀ
dinitrobenzo[b]thiophenes 12a—d because of spontaneꢀ
ous dehydrochlorination.
Scheme 9
R = H (a), Cl (b), OMe (c), CF3 (d)

Synthesis of 2ꢀarylꢀ4ꢀXꢀ6ꢀnitrobenzo[b]thiophenes Russ.Chem.Bull., Int.Ed., Vol. 54, No. 3, March, 2005
715
To further functionalize dinitrobenzothiophenes 12
and 13, we studied their behavior in nucleophilic substiꢀ
tution reactions. Interestingly, only the 4ꢀNO2 group was
replaced, the 6ꢀNO2 group remaining intact even with an
excess of a nucleophile. For instance, thiols displace the
4ꢀNO2 group from 2ꢀarylꢀ4,6ꢀdinitrobenzo[b]thiophenes
12 in NMP in the presence of an equimolar amount of
K2CO3 at 60 °C (Scheme 10); the yields of products 14a—c
were 50 to 70%. The reaction with phenol occurs at 120 °C;
under these conditions, the yield of the product of 4ꢀNO2
group replacement decreased to 30%, while substitution
for the 6ꢀNO2 group was not detected anyway.
with benzothiophene 13 even at 20 °C for 48 h to give
azide 15; at elevated temperature (50 °C), intense resinifiꢀ
cation was observed.
Hence, dinitrobenzothiophenes 12 and 13 in reacꢀ
tions with anionic nucleophiles behave in a similar way:
the 4ꢀNO2 group is replaced regiospecifically, but chloro
derivatives 13 are more reactive than dinitrobenzoꢀ
thiophenes 12. This can be attributed to the electronꢀ
withdrawing effect of the chlorine atom in compounds 13.
However, an alternative explanation is also possible. As
noted above, the rotation of the nitro group (sterically
affected by the adjacent substituent) relative to the aroꢀ
matic ring plane in the starting nitro compound favors
nucleophilic substitution for this nitro group by facilitatꢀ
ing the formation of an ipsoꢀσꢀcomplex, which is the
rateꢀlimiting step of nitro group replacement according to
the SNAr mechanism. It is known19 that in 4,6ꢀdinitroꢀ
benzo[b]thiophenes, such a rotation can also be induced
by a periꢀsubstituent (i.e., a substituent in position 3); in
this case, replacement of the 4ꢀNO2 group is strongly actiꢀ
vated even by the electronꢀdonating 3ꢀNH2 group. Quanꢀ
tumꢀchemical AM1 calculations (Chem3D Ultra, 8.0)
for 3ꢀchloroꢀ4,6ꢀdinitroꢀ2ꢀphenylbenzo[b]thiophene 13a
showed that the 4ꢀNO2 group is rotated about the C—N
axis through 58°, while the 6ꢀNO2 group is rotated only
through 15°. In 4,6ꢀdinitroꢀ2ꢀphenylbenzo[b]thiophene
12a containing no 3ꢀCl atom, the rotation angles of the
4ꢀNO2 and 6ꢀNO2 groups are 13° and 6°, respectively.
Such a large difference between compounds 13a and 12a
in the rotation angle of the 4ꢀNO2 group can also be
responsible for its higher mobility in compound 13
than in 12.
Scheme 10
a
H
b
H
c
Cl
d
Cl
R
Nu SCH2Ph
SPh
SPh
OPh
It is worth noting that in the reactions of 2ꢀarylꢀ3ꢀ
chloroꢀ4,6ꢀdinitrobenzo[b]thiophenes 13a,b with nucleoꢀ
philes, the 4ꢀnitro group was replaced only, while the
chlorine atom remained intact (Scheme 11). In the reacꢀ
tions with thiols, substitution in compounds 13 occurred
even at 20 °C. With phenol, heating to 90 °C was required
(cf. 120 °C for compounds 12). Sodium azide reacted
Replacement of the nitro group in position 4 of the
benzothiophene fragment was proved by NOE experiꢀ
ments. The CH2 protons in compounds 14a and 16a inꢀ
teract with the benzothiophene H(5) proton (Scheme 12).
If the 6ꢀNO2 group were replaced, the NOE experiments
would reveal interaction with both the H(5) and H(7)
protons. The pattern is similar for compounds 14b and
16c and phenoxy derivatives: the H(5) proton interacts
only with the orthoꢀprotons of the phenyl ring. The valiꢀ
dation of structures 15a,b will be presented elsewhere we
deal with transformations of these azides.
Scheme 11
Thus, our study of nucleophilic substitution reactions
of 2,4,6ꢀtrinitrostilbenes with anionic Sꢀ and Oꢀnucleoꢀ
philes revealed that the oꢀNO2 group can be selectively
replaced; based on this, we developed the methods for
the synthesis of earlier unknown 2ꢀarylꢀ4,6ꢀdinitrobenꢀ
zo[b]thiophenes and 2ꢀarylꢀ3ꢀchloroꢀ4,6ꢀdinitrobenꢀ
zo[b]thiophenes, which can be further functionalized by
substituting a nucleophile for the 4ꢀNO2 group to give
4ꢀNuꢀ2ꢀarylꢀ6ꢀnitroꢀ and 4ꢀNuꢀ2ꢀarylꢀ3ꢀchloroꢀ6ꢀnitroꢀ
benzo[b]thiophenes, respectively.
15: R =H (a), Cl (b)
16
a
b
H
c
Cl
SPh
d
Cl
OPh
To sum up the results of the present work and our
previous data,19 one can conclude that regiospecific nuꢀ
R
H
Nu SCH2Ph
SCH2COOMe

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Sapozhnikov et al.
Scheme 12
4´ꢀChloroꢀ4,6ꢀdinitroꢀEꢀ2ꢀphenylsulfanylstilbene (3b). Yield
80%, m.p. 160—161 °C. 1H NMR, δ: 8.59 (d, 1 H, C6H2(NO2)2,
4J = 1.9 Hz); 7.73—7.48 (m, 10 H, Ar); 7.39, 6.91 (both d,
3
1 H each, CH, Jtrans = 16.5 Hz). Found (%): C, 57.97;
H, 3.02; N, 6.52. C20H13ClN2O4S. Calculated (%): C, 58.18;
H, 3.17; N, 6.79.
4´ꢀChloroꢀEꢀ2ꢀ(4ꢀmethylphenylsulfanyl)ꢀ4,6ꢀdinitrostilbene
(3c). Yield 83%, m.p. 161—162 °C. 1H NMR, δ: 8.53 (d,
1 H, C6H2(NO2)2, 4J = 1.9 Hz); 7.74—7.61 (m, 3 H,
Ar + C6H2(NO2)2); 7.52—7.30 (m, 7 H, Ar + CH); 6.89 (d, 1 H,
CH, 3Jtrans = 15.3 Hz); 2.39 (s, 3 H, Me). Found (%): C, 58.97;
H, 3.41; N, 6.45. C21H15ClN2O4S. Calculated (%): C, 59.09;
H, 3.54; N, 6.56.
4´ꢀMethoxyꢀ4,6ꢀdinitroꢀEꢀ2ꢀphenylsulfanylstilbene (3d).
1
Yield 72%, m.p. 133—134 °C. H NMR, δ: 8.55, 7.70 (both d,
4
1 H each, C6H2(NO2)2, J = 1.8 Hz); 7.67—7.52 (m, 7 H, Ar);
3
7.18 (d, 1 H, CH, Jtrans = 15.1 Hz); 6.98 (d, 2 H, C6H4OMe,
3J = 7.7 Hz); 6.82 (d, 1 H, CH, 3Jtrans = 14.9 Hz); 3.79 (s, 3 H,
OMe). Found (%): C, 61.82; H, 4.01; N, 6.69. C21H16N2O5S.
Calculated (%): C, 61.75; H, 3.95; N, 6.86.
4´ꢀMethoxyꢀEꢀ2ꢀ(4ꢀmethylphenylsulfanyl)ꢀ4,6ꢀdinitroꢀ
1
stilbene (3e). Yield 92%, m.p. 139—140 °C. H NMR, δ: 8.51
(d, 1 H, C6H2(NO2)2, 4J = 1.8 Hz); 7.71—7.48 (m, 5 H,
3
Ar + C6H2(NO2)2); 7.39 (d, 2 H, C6H4Me, J = 6.3 Hz); 7.18
3
3
(d, 1 H, CH, Jtrans = 15.6 Hz); 6.98 (d, 2 H, C6H4OMe, J =
7.7 Hz); 6.87 (d, 1 H, CH, 3Jtrans = 15.6 Hz); 3.81, 2.38 (both s,
3 H each, Me). Found (%): C, 62.39; H, 4.07; N, 6.58.
C22H18N2O5S. Calculated (%): C, 62.55; H, 4.29; N, 6.63.
4,6ꢀDinitroꢀEꢀ2ꢀphenylsulfanylꢀ4´ꢀtrifluoromethylstilbene
R =H (14), Cl (16)
cleophilic substitution for the 4ꢀNO2 group is common in
4,6ꢀdinitrobenzo[b]thiophenes, regardless of the characꢀ
ter of the substituent in the thiophene ring. The reasons
for this phenomenon will be discussed elsewhere.
1
(3f). Yield 86%, m.p. 132—133 °C. H NMR, δ: 8.60 (d, 1 H,
C6H2(NO2)2, 4J = 2.0 Hz); 7.88 (d, 2 H, C6H4CF3, 3J = 7.3 Hz);
7.81—7.77 (m, 3 H, C6H4CF3+ C6H2(NO2)2); 7.66—7.50 (m,
6 H, Ph + CH); 7.02 (d, 1 H, CH, 3Jtrans = 14.9 Hz). Found (%):
C, 56,35; H, 2.79; N, 6.05. C21H13F3N2O4S. Calculated (%):
C, 56.50; H, 2.94; N, 6.28.
Experimental
1
Replacement of the nitro group in the reactions of Eꢀ2,4,6ꢀtriꢀ
nitrostilbenes with phenols (general procedure). A mixture of
trinitrostilbene 1 (0.01 mol), K2CO3 (0.01 mol), and a phenol
(0.01 mol) in acetonitrile (20 mL) was refluxed for 6 h (moniꢀ
toring by TLC). After the reaction was completed, the mixture
was poured into water. The precipitate that formed was reꢀ
peatedly washed with water, dried in air, and recrystallized
from CCl4.
4,6ꢀDinitroꢀEꢀ2ꢀphenoxystilbene (5a). Yield 14%, m.p.
133—134 °C. 1H NMR, δ: 8.57, 7.69 (both s, 1 H each,
C6H2(NO2)2); 7.62—7.17 (m, 12 H, Ar + CH). Found (%):
C, 66.03; H, 4.05; N, 7.59. C20H14N2O5. Calculated (%):
C, 66.30; H, 3.89; N, 7.73.
H NMR spectra were recorded on a Bruker ACꢀ200 specꢀ
trometer. 13C NMR spectra were recorded on a Bruker AMꢀ300
spectrometer in DMSOꢀd6. Chemical shifts (δ) were referenced
to Me4Si. Mass spectra were recorded on an MSꢀ30 Kratos
instrument (70 eV). Melting points were determined according
to the Kofler method on a Boetius hot stage (heating rate
4 deg min–1).
Replacement of the nitro group in the reactions of Eꢀ2,4,6ꢀtriꢀ
nitrostilbenes with Sꢀnucleophiles (general procedure). A mixture
of trinitrostilbene 1 (0.01 mol), K2CO3 (0.01 mol), and a nuꢀ
cleophile (0.01 mol) in NMP (20 mL) was stirred at 20 °C for
30 min (monitoring by TLC). After the reaction was completed,
the mixture was poured into water. The precipitate that formed
was repeatedly washed with water, dried in air, and recrystalꢀ
lized from acetonitrile. The yields of the mixture of isomeric
sulfides 4 + 4´ are given below.
4´ꢀMethoxyꢀEꢀ2ꢀ(4ꢀmethylphenoxy)ꢀ4,6ꢀdinitrostilbene
(5b). Yield 37%, m.p. 171—172 °C. 1H NMR, δ: 8.52, 7.71
(both s, 1 H each, C6H2(NO2)2); 7.75 (d, 2 H, Ar, 3J = 7.9 Hz);
7.37 (d, 1 H, CH, 3Jtrans = 14.2 Hz); 7.31, 7.16 (both d, 2 H each,
3
3
R
H
Cl
86
OMe
82
CF3
54
Ar, J = 7.6 Hz); 7.07 (d, 1 H, CH, Jtrans = 14.2 Hz); 6.96 (d,
3
Yield (%)
77
2 H, Ar, J = 7.9 Hz); 3.78 (s, 3 H, OMe); 2.33 (s, 3 H, Me).
Found (%): C, 64.87; H, 4.41; N, 6.71. C22H18N2O6. Calcuꢀ
lated (%): C, 65.02; H, 4.46; N, 6.89.
4,6ꢀDinitroꢀEꢀ2ꢀphenylsulfanylstilbene (3a). Yield 79%, m.p.
158—159 °C. 1H NMR, δ: 8.58, 7.71 (both d, 1 H each,
C6H2(NO2)2, 4J = 2.0 Hz); 7.68—7.53 (m, 7 H, Ar); 7.47—7.31
(m, 4 H, Ar + CH); 6.91 (d, 1 H, CH, Jtrans = 16.1 Hz).
Found (%): C, 63.56; H, 3.66; N, 7.26. C20H14N2O4S. Calcuꢀ
lated (%): C, 63.48; H, 3.73; N, 7.40.
Eꢀ2ꢀ(4ꢀChlorophenoxy)ꢀ4´ꢀmethoxyꢀ4,6ꢀdinitrostilbene (5c).
1
Yield 26%, m.p. 191—192 °C. H NMR, δ: 8.58, 7.89 (both s,
3
1 H each, C6H2(NO2)2); 7.59 (m, 4 H, Ar); 7.36 (d, 1 H, CH,
3
3Jtrans = 14.9 Hz); 7.27 (d, 2 H, Ar, J = 8.1 Hz); 7.05 (d, 1 H,
3
3
CH, Jtrans = 14.9 Hz); 6.97 (d, 2 H, Ar, J = 8.0 Hz); 3.80

Synthesis of 2ꢀarylꢀ4ꢀXꢀ6ꢀnitrobenzo[b]thiophenes Russ.Chem.Bull., Int.Ed., Vol. 54, No. 3, March, 2005
717
4
(s, 3 H, OMe). Found (%): C, 58.98; H, 3.59; N, 6.48.
C21H15ClN2O6. Calculated (%):C, 59.10; H, 3.54; N, 6.56.
4ꢀNitroꢀEꢀ2,6ꢀdiphenylsulfanylstilbene (6). A. A mixture of
4,6ꢀdinitroꢀEꢀ2ꢀphenylsulfanylstilbene 3a (0.01 mol), K2CO3
(0.01 mol), and benzenethiol (0.01 mol) in NMP (20 mL) was
stirred at 20 °C for 8 h (monitoring by TLC) under inert gas and
then poured into water. The precipitate that formed was reꢀ
peatedly washed with water, dried in air, and recrystallized
from acetonitrile. The yield of compound 6 was 48%, m.p.
159—160 °C.
8.93 (d, 1 H, H(5), J = 1.9 Hz); 8.49 (s, 1 H, H(3)); 7.95 (m,
2 H, Ph); 7.56 (m, 3 H, Ph). Found (%): C, 55.83; H, 2.67;
S, 10.43. C14H8N2O4S. Calculated (%): C, 56.00; H, 2.69;
S, 10.68.
2ꢀ(4ꢀChlorophenyl)ꢀ4,6ꢀdinitrobenzo[b]thiophene (12b).
1
Yield 71%, m.p. 237—238 °C. H NMR, δ: 9.50 (d, 1 H, H(7),
4J = 1.9 Hz); 8.91 (d, 1 H, H(5), J = 1.9 Hz); 8.47 (s, 1 H,
4
3
H(3)); 7.96, 7.56 (both d, 2 H each, 4ꢀClC6H4, J = 7.6 Hz).
Found (%): C, 50.11; H, 1.98; S, 9.41. C14H8N2O4S. Calcuꢀ
lated (%): C, 50.23; H, 2.11; S, 9.58.
B. A mixture of stilbene 1a (0.01 mol), K2CO3 (0.02 mol),
and benzenethiol (0.02 mol) in NMP (20 mL) was stirred at
20 °C for 10 h (monitoring by TLC) under inert gas and then
poured into water. The precipitate that formed was repeatedly
washed with water, dried in air, and recrystallized from acetoniꢀ
2ꢀ(4ꢀMethoxyphenyl)ꢀ4,6ꢀdinitrobenzo[b]thiophene (12c).
1
Yield 52%, m.p. 207—208 °C. H NMR, δ: 9.43 (d, 1 H, H(7),
4
4J = 2.1 Hz); 8.87 (d, 1 H, H(5), J = 2.1 Hz); 8.35 (s, 1 H,
H(3)); 7.86, 7.10 (both d, 2 H each, 4ꢀMeOC6H4, 3J = 8.2 Hz);
3.82 (s, 3 H, MeO). Found (%): C, 54.58; H, 2.90; S, 9.78.
C15H10N2O5S. Calculated (%): C, 54.54; H, 3.05; S, 9.71.
4,6ꢀDinitroꢀ2ꢀ(4ꢀtrifluoromethylphenyl)benzo[b]thiophene
1
trile. The yield of compound 6 was 60%. H NMR, δ: 7.67 (m,
2 H, Ph); 7.61—7.53 (m, 11 H, Ph); 7.44 (m, 2 H, Ph); 7.38 (s,
3
1
2 H, C6H2(NO2)2); 7.30, 7.06 (both d, 1 H each, CH, Jtrans
=
(12d). Yield 47%, m.p. 192—193 °C. H NMR, δ: 9.54 (d, 1 H,
4
4
16.1 Hz). Found (%): C, 70.86; H, 4.20; S, 14.45. C26H19NO2S2.
Calculated (%): C, 70.72; H, 4.34; S, 14.52.
H(7), J = 2.1 Hz); 8.96 (d, 1 H, H(5), J = 2.1 Hz); 8.61 (s,
1 H, H(3)); 8.18, 7.90 (both d, 2 H each, 4ꢀCF3C6H4, 3J =
8.2 Hz). Found (%): C, 48.99; H, 1.77; S, 8.88. C15H7F3N2O4S.
Calculated (%): C, 48.92; H, 1.92; S, 8.71.
Oxidation of sulfides 3a and 6 into sulfones 7 and 9 (general
procedure). To a mixture of a sulfide (0.01 mol) in glacial AcOH
(30 mL) 30% H2O2 (5 mL per sulfide group) was added. The
reaction mixture was refluxed for 3 h and cooled. The precipiꢀ
tate that formed was filtered off and dried in air.
3ꢀChloroꢀ4,6ꢀdinitroꢀ2ꢀphenylbenzo[b]thiophene (13a). Yield
1
4
86%, m.p. 154—155 °C. H NMR, δ: 9.45 (d, 1 H, H(7), J =
4
2.0 Hz); 8.81 (d, 1 H, H(5), J = 2.0 Hz); 7.77 (m, 2 H, Ph);
4,6ꢀDinitroꢀEꢀ2ꢀphenylsulfonylstilbene (7). Yield 80%, m.p.
244—245 °C. 1H NMR, δ: 9.14, 9.09 (both d, 1 H each,
C6H2(NO2)2, 4J = 2.2 Hz); 7.72 (d, 2 H, Ph, 3J = 6.9 Hz); 7.65
(t, 1 H, Ph, 3J = 7.1 Hz); 7.47—7.38 (m, 7 H, Ph); 7.25 (d, 1 H,
CH, Jtrans = 16.3 Hz); 6.33 (d, 1 H, CH, Jtrans = 16.1 Hz).
Found (%): C, 58.38; H, 3.50; S, 7.62. C20H14N2O6S. Calcuꢀ
lated (%): C, 58.53; H, 3.44; S, 7.81.
7.60 (m, 3 H, Ph). Found (%): C, 50.08; H, 1.95; Cl, 10.40;
S, 9.51. C14H7ClN2O4S. Calculated (%): C, 50.23; H, 2.11;
Cl, 10.59; S, 9.58.
3ꢀChloroꢀ2ꢀ(4ꢀchlorophenyl)ꢀ4,6ꢀdinitrobenzo[b]thiophene
3
3
1
(13b). Yield 71%, m.p. 211—212 °C. H NMR, δ: 9.48 (d, 1 H,
4
H(7), 4J = 1.9 Hz); 8.82 (d, 1 H, H(5), J = 1.9 Hz); 7.79, 7.66
(both d, 2 H each, 4ꢀClC6H4, 3J = 7.9 Hz). Found (%): C, 45.67;
H, 1.49; Cl, 19.28; S, 8.63. C14H6Cl2N2O4S. Calculated (%):
C, 45.55; H, 1.64; Cl, 19.21; S, 8.69.
4ꢀNitroꢀEꢀ2,6ꢀdiphenylsulfonylstilbene (9). Yield 83%, m.p.
249—250 °C. 1H NMR, δ: 9.19 (s, 2 H, C6H2(NO2)2); 7.70—7.61
(m, 6 H, Ph); 7.48—7.32 (m, 7 H, Ph); 7.12—7.08 (m, 2 H, Ph);
3ꢀChloroꢀ2ꢀ(4ꢀmethoxyphenyl)ꢀ4,6ꢀdinitroꢀ2,3ꢀdihydrobenꢀ
3
3
1
6.56 (d, 1 H, CH, Jtrans = 15.7 Hz); 5.67 (d, 1 H, CH, Jtrans
=
zo[b]thiophene (11c). Yield 43%, m.p. 163—164 °C. H NMR,
4
4
15.8 Hz). Found (%): C, 61.86; H, 3.71; S, 12.52. C26H19NO6S2.
Calculated (%): C, 61.77; H, 3.79; S, 12.69.
δ: 8.81 (d, 1 H, H(7), J = 2.0 Hz); 8.59 (d, 1 H, H(5), J =
2.0 Hz); 7.23, 6.86 (both d, 2 H each, 4ꢀMeOC6H4, 3J = 8.5 Hz);
6.37, 5.38 (both s, 1 H each, CH); 3.71 (s, 3 H, MeO).
Found (%): C, 49.34; H, 2.96; Cl, 9.44; S, 8.54. C15H11ClN2O5S.
Calculated (%): C, 49.12; H, 3.02; Cl, 9.67; S, 8.74.
Eꢀ4ꢀNitroꢀ2ꢀphenylsulfanylꢀ6ꢀphenylsulfonylstilbene (8).
A mixture of sulfone 7 (0.01 mol), K2CO3 (0.01 mol), and
benzenethiol (0.01 mol) in NMP (20 mL) was stirred at 20 °C
for 1 h (monitoring by TLC) and poured into water. The preꢀ
cipitate that formed was repeatedly washed with water, dried in
air, and recrystallized from acetonitrile. The yield of compound 8
was 55%, m.p. 190—191 °C. 1H NMR, δ: 8.68 (d, 1 H,
Replacement of the nitro group in 4,6ꢀdinitroꢀ3ꢀXꢀbenꢀ
zo[b]thiophenes (general procedure). A mixture of benzo[b]thioꢀ
phene 12 or 13 (0.01 mol), K2CO3 (0.01 mol), and a nucleoꢀ
phile (0.01 mol) in NMP (20 mL) (reactions with NaN3 were
carried out in DMF without K2CO3) was stirred until the reacꢀ
tion was completed (monitoring by TLC). The reaction temꢀ
peratures and times are specified below. Then the reaction mixꢀ
ture was poured into water. The precipitate that formed was
repeatedly washed with water and dried in air.
4
C6H2(NO2)2, J = 2.0 Hz); 7.75 (m, 3 H, C6H2(NO2)2 + Ph);
7.65 (m, 1 H, Ph); 7.54 (m, 5 H, Ph); 7.49—7.38 (m, 7 H, Ph);
3
3
7.14 (d, 1 H, CH, Jtrans = 16.1 Hz); 6.49 (d, 1 H, CH, Jtrans
=
16.3 Hz). Found (%): C, 66.11; H, 3.87; S, 13.39. C26H19NO4S2.
Calculated (%): C, 65.94; H, 4.04; S, 13.54.
Synthesis of 4,6ꢀdinitroꢀ3ꢀXꢀbenzo[b]thiophenes (X = H
and Cl) (general procedure). An unseparated mixture of isomeric
sulfides 4 and 4´ (0.01 mol) was dissolved in dichloroethane
(10 mL). Then SO2Cl2 (0.01 mol, but 0.02 mol for 3ꢀchloroꢀ
benzothiophenes) was added and the solution was stirred at
room temperature for 0.5 to 1 h (monitoring by TLC). The
reaction mixture was concentrated and the resulting oil was
recrystallized from ethanol—acetonitrile (1 : 1). The yield was
converted with respect to sulfide 4.
4ꢀBenzylsulfanylꢀ6ꢀnitroꢀ2ꢀphenylbenzo[b]thiophene (14a).
Reaction conditions: 60 °C, 4 h. The yield of compound 14a was
1
4
61%, m.p. 156—157 °C. H NMR, δ: 8.86 (d, 1 H, H(7), J =
4
1.9 Hz); 8.10 (d, 1 H, H(5), J = 1.9 Hz); 7.97 (s, 1 H, H(3));
7.85 (m, 2 H, Ph); 7.59—7.41 (m, 5 H, Ph); 7.29 (m, 3 H, Ph);
4.50 (s, 2 H, CH2). Found (%): C, 66.73; H, 3.98; N, 3.56.
C21H15NO2S2. Calculated (%): C, 66.82; H, 4.01; N, 3.71.
6ꢀNitroꢀ2ꢀphenylꢀ4ꢀphenylsulfanylbenzo[b]thiophene (14b).
Reaction conditions: 60 °C, 3 h. The yield of compound 14b
1
4,6ꢀDinitroꢀ2ꢀphenylbenzo[b]thiophene (12a). Yield 66%,
m.p. 214—215 °C. 1H NMR, δ: 9.52 (d, 1 H, H(7), 4J = 1.9 Hz);
was 68%, m.p. 163—164 °C. H NMR, δ: 8.92 (d, 1 H, H(7),
4J = 1.9 Hz); 7.93 (s, 1 H, H(3)); 7.85—7.77 (m, 3 H, Ph + H(5));

718
Russ.Chem.Bull., Int.Ed., Vol. 54, No. 3, March, 2005
Sapozhnikov et al.
7.59—7.42 (m, 8 H, Ph). Found (%): C, 66.21; H, 3.54; N, 3.81.
C20H13NO2S2. Calculated (%): C, 66.09; H, 3.61; N, 3.85.
2ꢀ(4ꢀChlorophenyl)ꢀ6ꢀnitroꢀ4ꢀphenylsulfanylbenzo[b]thioꢀ
phene (14c). Reaction conditions: 60 °C, 3 h. The yield of comꢀ
C, 57.55; H, 2.61; Cl, 16.88; N, 3.40. C20H11Cl2NO3S. Calcuꢀ
lated (%): C, 57.71; H, 2.66; Cl, 17.03; N, 3.36.
References
1
pound 14c was 91%, m.p. 138—139 °C. H NMR, δ: 8.97 (d,
1 H, H(7), 4J = 1.9 Hz); 8.02 (s, 1 H, H(3)); 7.87 (d, 2 H,
4ꢀClC6H4, 3J = 7.9 Hz); 7.81 (d, 1 H, H(5), 4J = 1.9 Hz);
7.62—7.43 (m, 7 H, Ar). Found (%):C, 60.45; H, 2.96; N, 3.37.
C20H12ClNO2S2. Calculated (%): C, 60.37; H, 3.04; N, 3.52.
2ꢀ(4ꢀChlorophenyl)ꢀ6ꢀnitroꢀ4ꢀphenoxybenzo[b]thiophene
(14d). Reaction conditions: 120 °C, 10 h. The yield of comꢀ
1. O. Yu. Sapozhnikov, V. V. Mezhnev, M. D. Dutov, V. V.
Kachala, and S. A. Shevelev, Mendeleev Commun., 2004, 27.
2. V. A. Tartakovsky, S. A. Shevelev, M. D. Dutov, A. Kh.
Shakhnes, A. L. Rusanov, L. G. Komarova, and A. M.
Andrievsky, in Conversion Concepts for Commercial Applicaꢀ
tions and Disposal Technologies of Energetic Systems,
Ed. H. Krause, Kluwer Academic Publishers, Dordrecht,
1997, p. 137.
3. S. A. Shevelev, V. A. Tartakovsky, and A. L. Rusanov, in
Combustion of Energetic Materials, Eds K. K. Kuo and L. T.
DeLuca, Begell House, Inc., New York, 2002, p. 62.
4. I. L. Dalinger, T. I. Cherkasova, S. S. Vorob´ev, A. V.
Aleksandrov, G. P. Popova, and S. A. Shevelev, Izv. Akad.
Nauk, Ser. Khim., 2001, 2292 [Russ. Chem. Bull., Int. Ed.,
2001, 50, 2401].
5. T. K. Shkineva, I. L. Dalinger, S. I. Molotov, and S. A.
Shevelev, Tetrahedron Lett., 2000, 41, 4973.
6. V. V. Rozhkov, A. M. Kuvshinov, V. I. Gulevskaya, I. I.
Chevrin, and S. A. Shevelev, Synthesis, 1999, 2065.
7. A. M. Kuvshinov, V. I. Gulevskaya, V. V. Rozhkov, and
S. A. Shevelev, Synthesis, 2000, 1474.
8. I. L. Dalinger, T. I. Cherkasova, V. M. Khutoretskii, and
S. A. Shevelev, Mendeleev Commun., 2000, 72.
9. V. I. Gulevskaya, A. M. Kuvshinov, and S. A. Shevelev, Het.
Commun., 2001, 7, 283.
1
pound 14d was 29%, m.p. 202—203 °C. H NMR, δ: 8.78 (d,
4
1 H, H(7), J = 2.0 Hz); 8.08 (s, 1 H, H(3)); 7.87 (d, 2 H,
4ꢀClC6H4, 3J = 8.1 Hz); 7.57—7.46 (m, 5 H, Ar); 7.33 (d, 1 H,
H(5), 4J = 2.0 Hz); 7.30—7.21 (m, 2 H, Ar). Found (%):
C, 63.03; H, 3.02; N, 3.74. C20H12ClNO2S2. Calculated (%):
C, 62.91; H, 3.17; N, 3.67.
4ꢀAzidoꢀ3ꢀchloroꢀ6ꢀnitroꢀ2ꢀphenylbenzo[b]thiophene (15a).
Reaction conditions: 20 °C, 48 h. The yield of compound 15a
1
was 54%, m.p. 171—172 °C. H NMR, δ: 8.97 (d, 1 H, H(7),
4
4J = 1.9 Hz); 8.06 (d, 1 H, H(5), J = 1.9 Hz); 7.75 (m, 2 H,
Ph); 7.59 (m, 3 H, Ph). Found (%): C, 50.67; H, 2.02; Cl, 10.89;
N, 16.79. C14H7ClN4O2S. Calculated (%): C, 50.84; H, 2.13;
Cl, 10.72; N, 16.94.
4ꢀAzidoꢀ3ꢀchloroꢀ2ꢀ(4ꢀchlorophenyl)ꢀ6ꢀnitrobenzo[b]thioꢀ
phene (15b). Reaction conditions: 20 °C, 48 h. The yield of
1
compound 15b was 60%, m.p. 196—197 °C. H NMR, δ: 8.97
4
4
(d, 1 H, H(7), J = 1.9 Hz); 8.05 (d, 1 H, H(5), J = 1.9 Hz);
7.76, 7.62 (both d, 2 H each, 4ꢀClC6H4, 3J = 7.6 Hz). Found (%):
C, 45.85; H, 1.54; Cl, 19.31; N, 15.41. C14H7ClN4O2S. Calcuꢀ
lated (%): C, 46.04; H, 1.66; Cl, 19.42; N, 15.34.
10. E. Buncel, M. R. Crampton, M. J. Strauss, and F. Terrier,
Electron Deficient Aromatic and Heteroaromatic Base Interacꢀ
tion. The Chemistry of Anionic SigmaꢀComplexes, Elsevier,
New York, 1984.
4ꢀBenzylsulfanylꢀ3ꢀchloroꢀ6ꢀnitroꢀ2ꢀphenylbenzo[b]thioꢀ
phene (16a). Reaction conditions: 20 °C, 2 h. The yield of comꢀ
1
pound 16a was 73%, m.p. 161—162 °C. H NMR, δ: 8.82 (d,
1 H, H(7), 4J = 2.1 Hz); 8.10 (d, 1 H, H(5), 4J = 2.1 Hz);
7.77—7.71 (m, 2 H, Ph); 7.62—7.56 (m, 3 H, Ph); 7.54—7.47
(m, 2 H, Ph); 7.40—7.29 (m, 3 H, Ph); 4.47 (s, 2 H, CH2).
Found (%): C, 61.44; H, 3.33; Cl, 8.53; N, 3.47. C21H14ClNO2S2.
Calculated (%): C, 61.23; H, 3.43; Cl, 8.61; N, 3.40.
11. F. Terrier, Chem. Rev., 1982, 82, 77.
12. O. V. Serushkina, M. D. Dutov, V. N. Solkan, and S. A.
Shevelev, Izv. Akad. Nauk, Ser. Khim., 2001, 2297 [Russ.
Chem. Bull., Int. Ed., 2001, 50, 2406].
13. F. Benedetti, D. R. Marshall, C. J. M. Stirling, and J. L.
Leng, J. Chem. Soc., Chem. Commun., 1982, 18, 918.
14. (a) O. V. Serushkina, M. D. Dutov, and S. A. Shevelev, Izv.
Akad. Nauk, Ser. Khim., 2001, 252 [Russ. Chem. Bull., Int.
Ed., 2001, 50, 261]; (b) V. N. Solkan and S. A. Shevelev,
Abstrs, III Vserossiiskii simpozium po organicheskoi khimii
"Strategiya i taktika organicheskogo sinteza" (Yaroslavl´,
Rossiya, mart 2001 g.) [III AllꢀRussia Symp. on Organic Chemꢀ
istry "Strategy and Tactics of Organic Synthesis" (Yaroslavl,
Russia, March, 2001)], Yaroslavl, 2001, 100 (in Russian).
15. V. V. Rozhkov, A. M. Kuvshinov, and S. A. Shevelev, Synth.
Commun., 2002, 32, 1465.
3ꢀChloroꢀ4ꢀmethoxycarbonylmethylsulfanylꢀ6ꢀnitroꢀ2ꢀ
phenylbenzo[b]thiophene (16b). Reaction conditions: 20 °C, 2 h.
The yield of compound 16b was 78%, m.p. 133—134 °C.
4
1H NMR, δ: 8.91 (d, 1 H, H(7), J = 2.0 Hz); 8.07 (d, 1 H,
4
H(5), J = 2.0 Hz); 7.76 (m, 2 H, Ph); 7.57 (m, 3 H, Ph); 4.22
(s, 2 H, CH2); 7.71 (s, 3 H, OMe). Found (%): C, 51.93; H, 2.86;
Cl, 8.92; N, 3.41. C17H12ClNO4S2. Calculated (%): C, 51.84;
H, 3.07; Cl, 9.00; N, 3.56.
3ꢀChloroꢀ2ꢀ(4ꢀchlorophenyl)ꢀ6ꢀnitroꢀ4ꢀphenylsulfanylbenꢀ
zo[b]thiophene (16c). Reaction conditions: 20 °C, 1.5 h. The
1
yield of compound 16c was 89%, m.p. 204—205 °C. H NMR,
δ: 8.97 (d, 1 H, H(7), 4J = 1.9 Hz); 7.81, 7.63 (both d, 2 H each,
4ꢀClC6H4, 3J = 7.8 Hz); 7.81 (d, 1 H, 4J = 1.9 Hz, H(5));
7.59—7.50 (m, 6 H, Ph + H(5)). Found (%): C, 55.64; H, 2.70;
Cl, 16.16; N, 2.89. C20H11Cl2NO2S2. Calculated (%): C, 55.68;
H, 2.61; Cl, 16.31; N, 3.06.
16. O. V. Serushkina, M. D. Dutov, O. Yu. Sapozhnikov, B. I.
Ugrak, and S. A. Shevelev, Zh. Org. Khim., 2002, 38, 1819
[Russ. J. Org. Chem., 2002, 38 (Engl. Transl.)].
17. E. Kuhle, Synthesis, 1970, 561.
18. A. Ruwet and M. Renson, Bull. Soc. Chim. Belg., 1970, 593.
19. S. A. Shevelev, I. L. Dalinger, and T. I. Cherkasova, Tetraꢀ
hedron Lett., 2001, 42, 8539.
3ꢀChloroꢀ2ꢀ(4ꢀchlorophenyl)ꢀ6ꢀnitroꢀ4ꢀphenoxybenꢀ
zo[b]thiophene (16d). Reaction conditions: 90 °C, 7 h. The yield
of compound 16d was 15%, m.p. 150—151 °C. 1H NMR, δ: 8.96
(d, 1 H, H(7), 4J = 2.0 Hz); 7.78, 7.63 (both d, 2 H each,
4
4ꢀClC6H4, 3J = 8.1 Hz); 7.56 (d, 1 H, H(5), J = 2.0 Hz); 7.51
Received November 12, 2004;
(m, 2 H, Ph); 7.23 (m, 1 H, Ph); 7.15 (m, 2 H, Ph). Found (%):
in revised form December 17, 2004