Nucleophilic addition to the double bond of 2,4,6-trinitrostyrene and transformations of adducts

Article abstract of DOI:10.1007/s11172-005-0357-6

Conditions were found under which 2,4,6-trinitrostyrene derived from 2,4,6-trinitrotoluene adds nucleophiles (thiophenol, aniline, and aliphatic amines) at the vinyl fragment to form the corresponding β-X-ethyl-2,4,6- trinitrobenzenes (X = PhS, PhNH, or R

Full text of DOI:10.1007/s11172-005-0357-6

1048
Russian Chemical Bulletin, International Edition, Vol. 54, No. 4, pp. 1048—1051, April, 2005
Nucleophilic addition to the double bond of 2,4,6ꢀtrinitrostyrene
and transformations of adducts*
ꢀ
O. Yu. Sapozhnikov, V. V. Mezhnev, M. D. Dutov, 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@ioc.ac.ru
Conditions were found under which 2,4,6ꢀtrinitrostyrene derived from 2,4,6ꢀtrinitrotoluꢀ
ene adds nucleophiles (thiophenol, aniline, and aliphatic amines) at the vinyl fragment to form
the corresponding βꢀХꢀethylꢀ2,4,6ꢀ trinitrobenzenes (X = PhS, PhNH, or R2N). In the reacꢀ
tions with primary aromatic amines, the initially formed adducts undergo intramolecular
replacement of the nitro group followed by aromatization of the indolines that formed to the
corresponding Nꢀsubstituted 4,6ꢀdinitroindoles.
Key words: 2,4,6ꢀtrinitrostyrene, 2,4,6ꢀtrinitrotoluene, indoles, nucleophilic addition, inꢀ
tramolecular cyclization.
The present study is part of investigations on the chemꢀ
in Eꢀ2,4,6ꢀtrinitrostilbenes remains intact in these reꢀ
actions.
istry of the explosive 2,4,6ꢀtrinitrotoluene (TNT) aimed
at developing scientific fundamentals and technology of
the use of TNT as a multipurpose synthon.1,2
Earlier,3—5 we have found conditions under which the
nitro group (predominantly, in the ortho position) in
Eꢀ2,4,6ꢀtrinitrostilbenes, which are produced by condenꢀ
sation of TNT with aromatic aldehydes, is replaced under
the action of Nꢀ, Sꢀ, or Oꢀnucleophiles. The double bond
The aim of the present study was to investigate the
reactions of an analog of Eꢀ2,4,6ꢀtrinitrostilbenes, viz.,
2,4,6ꢀtrinitrostyrene, with nucleophiles. The replacement
of the βꢀaryl group with the hydrogen atom would be
expected to enhance the reactivity of the vinyl fragment
toward nucleophiles due to a decrease in steric hindrance
to the attack on the Cβ atom.
2,4,6ꢀTrinitrostyrene (1) can be prepared from TNT
in several steps6,7 (Scheme 1). Only one example of the
reactions of styrene 1 with nucleophiles has been docuꢀ
mented earlier: under the action of NaN3 (DMF, ~20 °C),
* Dedicated to Corresponding Member of the Russian Acadꢀ
emy of Sciences E. P. Serebryakov on the occasion of his
70th birthday.
Scheme 1
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 1022—1025, April, 2005.
1066ꢀ5285/05/5404ꢀ1048 © 2005 Springer Science+Business Media, Inc.

Nucleophilic addition to 2,4,6ꢀtrinitrostyrene
Russ.Chem.Bull., Int.Ed., Vol. 54, No. 4, April, 2005
1049
Scheme 2
phenol to the vinyl fragment giving rise only to adduct 5
(Scheme 2).
We found conditions, under which other nucleophiles
also add to the double bond of styrene 1 (Scheme 3). For
example, heating of aniline in ethanol affords adduct 6.
In the reactions with aliphatic secondary amines, the best
results were obtained in benzene (in polar protic and
aprotic solvents, considerable resinification was observed)
with the use of an equimolar ratio of the reagents (exemꢀ
plified by the reaction of morpholine giving rise to adꢀ
duct 7). Refluxing of imidazole with styrene 1 in ethanol
affords adduct 8. It should be noted that, under analoꢀ
gous conditions, Eꢀ2,4,6ꢀtrinitrostilbenes do not give
doubleꢀbond addition products with aniline, amines, and
NHꢀazoles. Therefore, the results of the earlier studies3,4
and our investigation provide evidence that the βꢀaryl
substituent at the double bond hinders the addition of
nucleophiles to this bond.
Earlier,9 compound 6 has been synthesized by the
replacement of the chlorine atom in 2ꢀchloroethylꢀ
2´,4´,6´ꢀtrinitrobenzene under the action of 2 equiv. of
aniline. However, taking into account our data, this proꢀ
cess can be represented as the successive elimination of
HCl and addition of aniline to the resulting styrene 1.
The reactions of primary aliphatic amines with styrene
1 follow another pathway. For example, the reaction of
an equimolar amount of benzylamine with 2,4,6ꢀtrinitroꢀ
styrene in ethanol gives only compound 9, which is the
addition product of benzylamine to two molecules of styꢀ
rene 1 (Scheme 4). Unexpectedly, the reaction with the
use of a large excess of benzylamine produced indole 12a
only the оꢀNO2 group is replaced to form 2ꢀazidoꢀ4,6ꢀ
dinitrostyrene 48 (see Scheme 1).
In contrast to these results, we found that the reaction
of thiophenol with styrene 1 under the conditions typical
of the replacement of the nitro group in Eꢀ2,4,6ꢀtrinitroꢀ
stilbenes with thiophenol4 (in the presence of K2CO3, in
Nꢀmethylpyrrolidone, 20 °C) affords a mixture of prodꢀ
1
ucts. Analysis of the H NMR spectra of this mixture
showed that it contained products of the replacement of
the nitro group in styrene 1, products of the addition of
thiophenol to the double bond, and products of the reꢀ
placement of the nitro group in the latter. It appeared that
the reaction in a less polar solvent (EtOH) with the use of
an organic base (Et3N) results in the addition of thioꢀ
Scheme 3

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Russ.Chem.Bull., Int.Ed., Vol. 54, No. 4, April, 2005
Sapozhnikov et al.
Scheme 4
R = PhCH2 (a), PhCH2CH2 (b), Me (c)
(R = CH2Ph). The reactions with the use of phenetylꢀ
amine and methylamine give similar results.
It should be emphasized that the addition product
of aniline to styrene 6 reacts with thiophenol under
conditions typical of 2,4,6ꢀtrinitrotoluene10 and
Eꢀ2,4,6ꢀtrinitrostilbenes,4 resulting in the replacement of
the orthoꢀnitro group (Scheme 5).
It should be noted that all reactions produced indoles
12 in low yields (12—18%). Presumably, these reactions
proceed according to Scheme 4. In the first step, primary
amines add to the double bond to form adduct 10, which
undergoes intramolecular replacement of the nitro group
giving rise to indoline 11. The low yield of the final indole
is, apparently, attributable to the fact that the resulting
indoline 11 is oxidized only by nitro compounds present
in the mixture rather than by atmospheric oxygen, beꢀ
cause the reaction performed under an inert gas atmoꢀ
sphere follows the same pathways and produces indole 12
in approximately the same yield.
Experimental
The 1H NMR spectra were recorded on a Bruker АCꢀ200
instrument. The chemical shifts (δ) are given relative to Me4Si.
The mass spectra were obtained on an MSꢀ30 instrument
(Kratos); the ionization energy was 70 eV. The melting points
were determined on a Boetius hot stage at a heating rate
of 4 K min–1
.
Nucleophilic addition to the double bond of 2,4,6ꢀtrinitroꢀ
styrene (general procedure). A mixture of styrene 1 (1.2 g,
0.005 mol), ethanol (15 mL), and a nucleophile (0.005 mol) (in
the synthesis of compound 5, Et3N (0.005 mol) was added) was
refluxed for 2 h (compounds 6 and 8) or stirred at room temꢀ
perature (compounds 5 and 9). Then the reaction mixture was
poured into water, and the precipitate of compound 5, 6, 8, or 9
was filtered off, dried in air, and recrystallized.
Scheme 5
2,4,6ꢀTrinitroꢀ2ꢀphenylsulfanylethylbenzene (5). The yield
was 69%. M.p. 166—167 °C (EtOH/CH3CN). Found (%):
C, 47.86; H, 3.02; N, 11.80. C14H11N3O6S. [M]+ = 349. Calcuꢀ
lated (%): C, 48.14; H, 3.17; N, 12.03. 1H NMR (CDCl3), δ:
8.75 (s, 2 H, C6H2(NO2)3); 7.38—7.19 (m, 5 H, SPh); 3.41 (t,
2 H, CH2, 3J = 7.5 Hz); 3.26 (t, 2 H, CH2, 3J = 7.2 Hz).
2ꢀ(NꢀAnilino)ethylꢀ2,4,6ꢀtrinitrobenzene (6). The yield was
61%. M.p. 151—153 °C (EtOH) (cf. lit. data9: m.p. 153—155 °C).
Found (%): C, 50.47; H, 3.70; N, 16.59. C14H12N4O6. Calcuꢀ
lated (%): C, 50.61; H, 3.64; N, 16.86. 1H NMR (DMSOꢀd6), δ:
9.06 (s, 2 H, C6H2(NO2)3); 7.08 (t, 2 H, Ph, 3J = 7.9 Hz);
NMP is Nꢀmethylpyrrolidone

Nucleophilic addition to 2,4,6ꢀtrinitrostyrene
Russ.Chem.Bull., Int.Ed., Vol. 54, No. 4, April, 2005
1051
6.61—6.48 (m, 3 H, Ph); 5.82 (t, 1 H, NH, 3J = 5.1 Hz);
3.42—3.34 and 3.22—3.15 (both m, 2 H each, CH2).
lated (%): C, 48.87; H, 3.19; N, 19.00. 1H NMR (DMSOꢀd6), δ:
8.96 and 8.78 (both s, 1 H each, C6H2(NO2)2); 8.15 (d, 1 H,
CH, 3J = 3.4 Hz); 7.18 (d, 1 H, CH, 3J = 3.5 Hz); 4.06
(s, 3 H, Me).
2ꢀ(NꢀImidazolyl)ethylꢀ2,4,6ꢀtrinitrobenzene (8). The yield
was 62%. M.p. 172—173 °C (EtOH). Found (%): C, 42.76;
H, 2.78; N, 22.51. C11H9N5O6. Calculated (%): C, 43.00;
H, 2.95; N, 22.80. 1H NMR (DMSOꢀd6), δ: 9.08 (s, 2 H,
C6H2(NO2)3); 7.55, 7.11, and 6.93 (all s, 1 H each, imidazole);
4.37 and 3.44 (both t, 2 H each, CH2, 3J = 6.7 Hz).
NꢀBenzylꢀN,Nꢀbis(2,4,6ꢀtrinitrophenetyl)amine (9). The
yield was 47%. M.p. 162—163 °C (EtOH). Found (%): C, 46.95;
H, 3.01; N, 16.51. C23H19N7O12. Calculated (%): C, 47.19;
H, 3.27; N, 16.75. 1H NMR (DMSOꢀd6), δ: 8.97 (s, 4 H,
2 C6H2(NO2)3); 7.14—7.02 (m, 5 H, Ph); 3.53 (s, 2 H, CH2Ph);
3.10 (t, 4 H, 2 CH2, 3J = 7.6 Hz); 2.84 (t, 4 H, 2 CH2,
3J = 7.3 Hz).
2ꢀ(NꢀAnilino)ethylꢀ2,4ꢀdinitroꢀ6ꢀphenylsulfanylbenzene (13).
Thiophenol (10 mmol) was added to a mixture of compound 6
(10 mmol) and K2CO3 (10 mmol) in Nꢀmethylpyrrolidone
(10 mL). The reaction mixture was stirred at room temperature
for 3 h and poured into water. The precipitate was filtered off
and dried in air. The yield was 61%. M.p. 157—158 °C.
Found (%): C, 60.92; H, 4.01; N, 10.22. C20H17N3O4S. Calcuꢀ
lated (%): C, 60.75; H, 4.33; N, 10.63. 1H NMR (DMSOꢀd6), δ:
8.56 and 7.85 (both s, 1 H each, C6H2(NO2)3); 7.63—7.51 (m,
5 H, Ph); 7.12—7.06 (m, 2 H, Ph); 6.68—6.52 (m, 3 H, Ph);
5.91 (t, 1 H, NH, 3J = 5.3 Hz); 3.43—3.34 and 3.28—3.15
(both m, 2 H each, CH2).
2ꢀ(NꢀMorpholino)ethylꢀ2,4,6ꢀtrinitrobenzene (7). A solution
of morpholine (0.005 mol) in benzene (5 mL) was added with
stirring to a solution of styrene 1 (1.2 g, 0.005 mol) in benzene
(5 mL). The solution was stirred for 10 min, and the benzene
was evaporated in vacuo. The resulting oil was crystallized from
ethanol. The yield was 70%. M.p. 131—133 °C. Found (%):
C, 43.92; H, 4.25; N, 16.85. C12H14N4O7. Calculated (%):
C, 44.18; H, 4.33; N, 17.17. 1H NMR (CDCl3), δ: 8.79 (s, 2 H,
C6H2(NO2)3); 3.70—3.58 (m, 4 H, morpholine); 3.29 (t, 2 H,
References
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1997, p. 137.
3
3
CH2, J = 5.3 Hz); 2.71 (t, 2 H, CH2, J = 5.2 Hz); 2.44—2.35
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Synthesis of indoles 12 (general procedure). A solution of
primary amine (0.02 mol) in ethanol (5 mL) (in the case of
MeNH2, a 40% aqueous solution (2 mL) was used) was added
with stirring to a solution of styrene 1 (1.2 g, 0.005 mol) in
ethanol (10 mL). The reaction mixture was refluxed for 4 h and
poured into water. The precipitate that formed was filtered off,
dried in air, and treated with chloroform (3×30 mL). The comꢀ
bined solutions were concentrated to 30 mL and filtered through
a layer of silica gel (0.035—0.070 mm, Acros). The solution was
concentrated in vacuo and the resulting compound was crystalꢀ
lized from ethanol.
1ꢀBenzylꢀ4,6ꢀdinitroindole (12a). The yield was 18%. M.p.
170—171 °C. Found (%): C, 60.56; H, 3.80; N, 13.80.
C
15H11N3O4. [M]+ 297. Calculated (%): C, 60.61; H, 3.73;
N, 14.14. 1H NMR (DMSOꢀd6), δ: 9.02 and 8.77 (both s,
1 H each, C6H2(NO2)2); 8.33 (d, 1 H, CH, 3J = 3.7 Hz);
7.38—7.21 (m, 6 H, Ph + CH); 5.76 (s, 2 H, CH2).
4,6ꢀDinitroꢀ1ꢀ(2ꢀphenylethyl)indole (12b). The yield was
15%. M.p. 150—151 °C. Found (%): C, 61.54; H, 4.03; N, 13.27.
C
16H13N3O4. [M]+ 311. Calculated (%): C, 61.73; H, 4.21;
N, 13.50. 1H NMR (DMSOꢀd6), δ: 8.84 and 8.72 (both s,
1 H each, C6H2(NO2)2); 8.12 (d, 1 H, CH, 3J = 3.4 Hz);
7.26—7.11 (m, 6 H, Ph + CH); 4.74 (t, 2 H, CH2, 3J = 6.6 Hz);
3.12 (t, 2 H, CH2, 3J = 6.7 Hz).
1ꢀMethylꢀ4,6ꢀdinitroindole (12с). The yield was 12%. M.p.
176—177 °C (cf. lit. data11: m.p. 179—180 °C). Found (%):
C, 48.66; H, 3.15; N, 18.82. C9H7N3O4. [M]+ 221. Calcuꢀ
Received January 25, 2005;
in revised form April 1, 2005