Synthesis of (E) α,2,4-trinitrostilbenes from (E) 2,4-dinitrostilbenes

Article abstract of DOI:10.1081/SCC-120018685

A convenient synthesis of (E) α,2,4-trinitrostilbenes 2a-d from (E) 2,4-dinitrostilbenes 1a-e by direct nitration is reported. Isomerization of the trans geometry of the reactant stilbenes to cis in the products was found. The structures of stilbenes 2a,

Full text of DOI:10.1081/SCC-120018685

Synthetic Communications
An International Journal for Rapid Communication of Synthetic Organic
Chemistry
ISSN: 0039-7911 (Print) 1532-2432 (Online) Journal homepage: http://www.tandfonline.com/loi/lsyc20
Synthesis of (E) α,2,4-Trinitrostilbenes from (E) 2,4-
Dinitrostilbenes
S. Saravanan & P. C. Srinivasan
To cite this article: S. Saravanan & P. C. Srinivasan (2003) Synthesis of (E) α,2,4-Trinitrostilbenes
from (E) 2,4-Dinitrostilbenes, Synthetic Communications, 33:8, 1261-1266, DOI: 10.1081/
SCC-120018685
To link to this article: http://dx.doi.org/10.1081/SCC-120018685
Published online: 15 Aug 2006.
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SYNTHETIC COMMUNICATIONSÕ
Vol. 33, No. 8, pp. 1261–1266, 2003
Synthesis of (E ) a,2,4-Trinitrostilbenes
from (E ) 2,4-Dinitrostilbenes
*
S. Saravanan and P. C. Srinivasan
Department of Organic Chemistry, University of
Madras, Guindy Campus, Chennai, India
ABSTRACT
A convenient synthesis of (E ) a,2,4-trinitrostilbenes 2a–d from
(E ) 2,4-dinitrostilbenes la–e by direct nitration is reported.
Isomerization of the trans geometry of the reactant stilbenes to cis
in the products was found. The structures of stilbenes 2a, 2c and 2d
were confirmed by XRD.
*Correspondence: P. C.Srinivasan,DepartmentofOrganicChemistry,University
of Madras, Guindy Campus, Chennai 600 025, India; E-mail: pancol2000@
yahoo.co.in.
1261
DOI: 10.1081/SCC-120018685
Copyright & 2003 by Marcel Dekker, Inc.
0039-7911 (Print); 1532-2432 (Online)
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1262
Saravanan and Srinivasan
Aromatic nitro compounds are important synthetic targets due to
their uses as explosives, dye intermediates and battery cathodes.[1]
a-Nitrostilbenes[2] belong to a class of important nitro compounds as
potential precursors for biologically active b-phenylethylamines and
Michael acceptors.[3] A survey of literature[4] shows that only a few
styrenes undergo direct nitration to give b-nitrostyrenes, while there are
no reports on side chain nitration of stilbenes. a-Nitrostilbenes are
synthesized by condensing a-nitrotoluenes with aromatic aldehydes.
Recent reports on the synthesis of a-2,4-trinitrotoluene[5] and a-nitro-
alkylbenzenes[6] also prompted us to report our synthesis of (E ) a,2,4-
trinitrostilbenes here.
We report here the first synthesis of (E ) a,2,4-trinitrostilbenes 2a–d by
direct nitration of easily available[7] (E ) 2,4-dinitrostilbenes la–e in
55–60% yield, using fuming nitric acid[8] (Sch. 1). The nitration was
found to be temperature independent in case of stilbenes la, lb, and 1e.
Whereas in the case of 1c it gives exclusively 2b at 25ꢀC and 2c at 90ꢀC.
In the case of 1d only side chain nitrated product 2b at 25ꢀC and side chain
as well as nuclear nitrated product 2c at 90ꢀC was obtained (Table 1).
It was found that the trans geometry of the reactant stilbenes la–e
1
(confirmed by H NMR (la–e) and XRD in case of 1e alone) isomerized
to cis in the products with respect to the aryl rings in the reactant. The cis
geometry of the products was confirmed by XRD in the case of stilbenes
2a, 2c and 2d (Fig. 1). This isomerization may be due to the favorable
ꢀ–ꢀ interaction between the two aryl rings during nitration.
Scheme 1.

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(E) a,2,4-Trinitrostilbenes
1263
Table 1.
Product
Reactant
25ꢀC
90ꢀC
M.p. (ꢀC)
Yield (%)
1a
1b
1c
1d
1e
2a
2a
2b
2b
2d
2a
2a
2c
2c
2d
200
200
55
55
58
60
60
2b, 183
2c, 210
215
Further work is in progress to study the electrochemical properties of
stilbenes 2a–d.
EXPERIMENTAL
Synthesis of 40-Methyl-2,30,4-trinitrostilbene (1d)
A mixture of 2,4-dinitrotoluene[7] (5 mM, 0.9 g) and 4-methyl-3-nitro-
benzaldehyde[9,10] (5 mM, 0.8 g) and pyrrolidine (0.106 g, 1.5 mM) was
stirred for 5 h in dry DMF for 5 h at 25–30ꢀC. Then it was poured
over crushed ice. The crude product was filtered, washed with water
and then with methanol and dried over anhydrous calcium chloride.
Yield 80%; m.p. 200ꢀC. IR (KBr): 3085, 1598, 1526, 1343 cmꢁ1
.
1H NMR (CDC13) 200 MHz: ꢁ 8.8 (d, 1H, J ¼ 2.3 Hz), 8.4 (d, 1H, J ¼
8.0 Hz), 8.1 (d, 1H, J ¼ 2.5 Hz), 7.9 (d, 1H, J ¼ 8.1 Hz), 7.7–7.5 (m, 3H,
vinylic and aromatic H), 7.3 (d, 1H, J ¼ 8 Hz), 2.6 (s, 3H). MS: m/z 329
(24% Mþ), 312 (23%), 164 (90%), 55 (100%).
Representative Procedure for the Synthesis of
(E ) 40-Methyl-a,2,30,4,50-pentanitrostilbene (2c)
To 5 mM (2.095 g) of (E ) 40-methyl-2,30,4-trinitrostilbene 5 mL of
fuming HNO3 was added slowly with stirring. Then the reaction mixture
was kept at 90ꢀC for 5 min. After cooling to 25–30ꢀC, the reaction mix-
ture was poured over crushed ice, the crude product was filtered, washed
with water and dessicated over anhydrous CaC12 and recrystallized from
acetone. Yield 60%. IR (KBr): 3130, 1649, 1602, 1517, 1326 cmꢁ1
.
1H NMR (DMSO-d6) 400 MHz: ꢁ 2.4 (s, 3H), 7.96 (d, 1H, J ¼ 8.5 Hz),

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1264
Saravanan and Srinivasan
Figure 1. XRD structure of stilbene 2c.

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(E) a,2,4-Trinitrostilbenes
1265
8.0 (s, 1H), 8.7 (m, 2H, Ar-H and vinylic-H), 9.1 (d, 1H, J ¼ 3.05 Hz).
Anal. calcd. for C15H9N5O10; C 42.9, H 2.16, N 16.7; Found C 43.04, H
1.9, N 17.1. M.p. 210ꢀC.
(E ) a,2,30,4-Tetranitrostilbene (2a)
Yield 55%. IR (KBr): 1660, 1606, 1533, 1332 cmꢁ1 1H NMR
.
(CDCl3) 300 MHz: ꢁ 9.22 (d, 1H, J ¼ 2.1 Hz), 8.55 (d, 1H, J ¼ 8 Hz),
8.48 (s, 1H), 8.32 (d, 1H, J ¼ 8 Hz), 8.1 (s, 1H). Anal calcd. for
C14H8N4O8; C 46.67, H 2.23, N 15.55; Found C 46.67, H 2.23, N
15.93. M.p. 200ꢀC.
(E ) 40-Methyl-a,2,30,4-tetranitrostilbene (2b)
1
Yield 58%. IR (KBr): 3125, 1650, 1600, 1526, 1340 cmꢁ1. H NMR
(CDCl3) 400 MHz: ꢁ 9.22 (d, 1H, J ¼ 1.96 Hz), 8.56 (d, 1H, J ¼ 8.32 Hz),
8.42 (s, 1H), 7.70 (s, 1H), 7.58 (d, 1H, J ¼ 8.28 Hz), 7.29 (d, 1H,
J ¼ 8.32 Hz), 7.14 (d, 1H, J ¼ 8.3 Hz), 2.7 (s, 3H). Anal. calcd. for
C15H10N4O8; C 48.13, H 2.69, N 15.0; Found C 48.0, H 2.09, N 15.5.
M.p. 183ꢀC.
(E ) 40-Methoxy-a,2,30,4-tetranitrostilbene (2d)
1
Yield 60%. IR (KBr): 3124, 1650, 1614, 1542, 1325 cmꢁ1. H NMR
(CDCl3) 400 MHz: ꢁ 9.21 (d, 1H, J ¼ 1.96 Hz), 8.58 (d, 1H, J ¼ 8.52 Hz),
8.38 (s, 1H), 7.62 (d, 1H, J ¼ 8.32 Hz), 7.58 (d, 1H, J ¼ 8.44 Hz), 7.22
(d, 1H, J ¼ 8.8 Hz), 7.03 (d, 1H, J ¼ 8.8 Hz), 3.97 (s, 3H). Anal. calcd.
for C15H10N4O9; C 46.16, H 2.58, N 14.35; Found C 46.38, H 2.46,
N 14.59. M.p. 215ꢀC.
ACKNOWLEDGMENT
The authors thank Dr. Paul Ratnasamy, Director; NCL, Pune for
providing CHN data for the stilbenes 2a–d, Prof. D. Velmurugan,
Dept. of Biophysics and Crystallography, University of Madras, for
providing XRD data for stilbenes 1e, 2a, 2c and 2d, CSIR, New Delhi
for financial support and the UGC-SAP Government of India for
instrument grants to this department.

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1266
Saravanan and Srinivasan
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Saravanan, S.; Srinivasan, P.C. Ind. J. Chem. 2001, 40A, 175–181.
2. Robertson, D.N. J. Org. Chem. 1960, 25, 47–49.
3. Flintoft, R.J.; Buzby, J.C.; Tucker, J.A. Tetrahedron Lett. 1999, 40,
4485–4488.
4. Nitro Group in Organic Synthesis; Noboru Ono; Wiley-VCH
Pubn, 2001.
5. Kawakami, T.; Suzuki, H. Tetrahedron Lett. 1999, 40, 1157–1160.
6. Vogel, E.M.; Buchwald, S.L. J. Org. Chem. 2002, 67, 106–111.
7. Saravanan, S.; Srinivasan, P.C. Syn. Commun. 2001, 31 (6), 24–28.
8. Fuming nitric acid was prepared by distilling 1:1 mixture (v/v) of
70% nitric acid and conc. sulphuric acid.
9. Beilsteins Hand Book of Organic Chemistry; Syst. No. 640, 1925;
Vol. 7, 299.
10. Rashid, I.; Hasan, N.; Muhammad Zia Ul, H.; Farag Ali, M.
J. Chem. Soc. Pak. 1997, 19, 141–144.
Received in the Netherlands April 18, 2002