A one-step, safe synthesis of 2,4-dinitrostyrene and related (Di)nitrodivinylbenzenes via Stille coupling

Article abstract of DOI:10.1055/s-2008-1032117

A one-step synthesis of 2,4-dinitrostyrene is described. Based on a Stille coupling, the procedure is more amenable to scale-up than the existing methods that require longer reaction sequences and hazardous nitration processes. This easily polymerizable monomer was isolated using a continuous extraction method. The reaction was extended to the synthesis of two other related vinyl monomers including the previously unknown l,3-dinitro-4,6-divinylbenzene.

Full text of DOI:10.1055/s-2008-1032117

PRACTICAL SYNTHETIC PROCEDURES
1805
A One-Step, Safe Synthesis of 2,4-Dinitrostyrene and Related
(Di)nitrodivinylbenzenes via Stille Coupling
S
ynthesis of 2,4-D
a
initrostyren
t
e
a
nd R
h
elate
d
(Di)n
a
itrodivinylb
l
enzen
i
e
s
e Eloy, Eric Pasquinet,* Eric Grech, Frank David-Quillot, Olivier Besnard, Didier Poullain
CEA Le Ripault, BP16, 37260 Monts, France
Fax +33(2)47345142; E-mail: eric.pasquinet@cea.fr
PSP
Received 12 December 2007; revised 19 December 2007
No125
Abstract: A one-step synthesis of 2,4-dinitrostyrene is described. Based on a Stille coupling, the procedure is more amenable to scale-up
than the existing methods that require longer reaction sequences and hazardous nitration processes. This easily polymerizable monomer
was isolated using a continuous extraction method. The reaction was extended to the synthesis of two other related vinyl monomers includ-
ing the previously unknown 1,3-dinitro-4,6-divinylbenzene.
Key words: Stille reaction, cross-coupling, polymers, nitro compounds, styrenes
Procedure 1
Procedure 2
Cl
Br
NO2
NO2
NO2
, Pd(PPh3)4
SnBu3
NO2
, Pd(PPh3)4
SnBu3
toluene, 80 °C, 16 h
65%
Cl
toluene, 80 °C, 15 h
44%
NO2
1b
NO2
NO2
NO2
2a
1a
2b
Procedure 3
Br
NO2
NO2
, Pd(PPh )
SnBu3
3 4
toluene, 110 °C, 8 h
88%
Br
2c
1c
Scheme 1
2,4-Dinitrostyrene (2a) is a well-known monomer which Nevertheless, the synthetic utility of 2a as a Michael ac-
has been primarily used in the field of energetic materi- ceptor could increase in the future, since azoles as well as
als.1 Unusually, it does not polymerize under classical S-nucleophiles were also shown to add on the related
radical or cationic conditions, but generates poly(2,4-dini- 2,4,6-trinitrostyrene.5
trostyrene) upon the action of basic species. Charge-trans-
Two main methods have been described for the synthesis
fer complexes with some organic amines were shown to
of 2a. The first is lengthy (four steps from a commercial
be involved in the polymerization process.2 The copoly-
product) and low yielding (overall yield <33%).6 The oth-
merization of 2a with 2,4,6-trinitrostyrene was also de-
er involves the dehydration or dehydrohalogenation of a
hydroxy- or haloethyldinitrobenzene, followed by elimi-
scribed.3 This ability of 2a to produce a number of
energetic polymers surely makes it an interesting target
nation to generate the vinyl functionality.6,7 The latter was
for synthetic chemists. Moreover, due to the strongly elec-
obtained in one or two steps using a nitration reaction.
tron-withdrawing nitro groups in the ortho and para posi-
This nitration step suffers from safety drawbacks since 1-
(2-nitratoethyl)-2,4-dinitrobenzene, which may exhibit
tions, Michael-type additions are expected to occur on 2a.
This reactivity, which could lead to an interesting class of
explosive properties, can be formed in certain conditions.
compounds, was exploited using nitrogen nucleophiles.4
Moreover, in our hands, the elimination procedure proved
unreliable, mainly because of polymerization (certainly
explaining the insoluble product mentioned in reference
7a). These bibliographical and experimental results
SYNTHESIS 2008, No. 11, pp 1805–1807
Advanced online publication: 06.03.2008
x
x.
x
x
.
2
0
0
8
prompted us to design a new synthesis for 2,4-dinitrosty-
DOI: 10.1055/s-2008-1032117; Art ID: Z28707SS
© Georg Thieme Verlag Stuttgart · New York

1806
N. Eloy et al.
PRACTICAL SYNTHETIC PROCEDURES
Procedure 1
rene (2a) which could meet the industrial requirements in
terms of efficiency and safety.
2,4-Dinitrostyrene (2a)7a
To a solution of 1-bromo-2,4-dinitrobenzene (1a; 30 g, 107 mmol)
in anhyd toluene (300 mL) were added tributyl(vinyl)tin (42.9 g,
135.3 mmol) and Pd(PPh3)4 (1.12 g, 9.7 mmol). The mixture was
stirred for 16 h at 80 °C. After cooling, an aq 1 M KF solution (410
mL) was added. The mixture was stirred for 2 h, and then filtered on
Celite. The organic layer was separated from the filtrate, dried
(MgSO4), and concentrated to dryness. The residue was dissolved
in MeCN (400 mL) and washed with heptane (4 × 100 mL). The
MeCN phase was extracted continuously with petroleum ether for 4
days. Upon concentration of the petroleum ether, the product pre-
cipitated. After filtration and drying in vacuo, pure 2a was obtained
as a pale yellow powder; yield: 15.0 g (65%); mp 53 °C.
Considering the commercial availability of both 1-chloro-
and 1-bromo-2,4-dinitrobenzene, the Stille reaction8 us-
ing tributyl(vinyl)tin as the stannylated partner was an ob-
vious choice. Since 1-bromo-2,4-dinitrobenzene (1a) was
reported to couple with other tin substrates,9 it was select-
ed to optimize the process. However, the cheaper chloro
derivative could also be used.
Standard Stille conditions [Pd(PPh3)4, tributyl(vinyl)tin
(1.3 equiv), toluene, 80 °C, 16 h] with 1a resulted in a
clean conversion into the desired 2,4-dinitrostyrene (2a)
as indicated by NMR analysis of the crude product. How-
ever, removal of tin salts and isolation of the product
proved to be the main issues. This usual problem in Stille
reaction was crucial here considering the high polymeriz-
ability of 2a and the need for an industrially amenable
process. As a matter of fact, chromatography on silica gel
resulted in almost complete degradation, with only traces
of 2a being recovered. Recrystallization in different sol-
vents was also ineffective mainly because of polymeriza-
tion during heating. Chemically pure 2a was obtained in a
65% yield by using the following sequence: (i) KF treat-
ment followed by liquid/liquid extraction with heptane to
remove tin residues, (ii) continuous extraction of the
crude product with petroleum ether, and (iii) filtration of
the pure 2,4-dinitrostyrene precipitated upon concentra-
tion of the petroleum ether extraction phase. This process
enabled the synthesis of 15 grams of 2a in a single batch.
IR: 3112, 3096, 1603, 1591, 1541, 1524, 1419, 1338, 1148, 985,
946, 908, 861, 831 cm–1.
1H NMR (200 MHz, CDCl3): d = 5.74 (d, J = 11.0 Hz, 1 H, Hbcis),
5.96 (d, J = 17.3 Hz, 1 H, Hbtrans), 7.23 (dd, J = 11.0, 17.3 Hz, 1 H,
Ha), 7.86 (d, J = 8.7 Hz, 1 H, H-4), 8.44 (dd, J = 2.3, 8.7 Hz, 1 H,
H-5), 8.80 (d, J = 2.3 Hz, 1 H, H-3).
13C NMR (50 MHz, CDCl3): d = 120.2, 123.1, 127.2, 129.7, 130.8,
139.0, 146.8, 147.4.
Procedure 2
1,3-Dinitro-4,6-divinylbenzene (2b)
To a solution of 4,6-dichloro-1,3-dinitrobenzene (1b; 10.1 g, 42.6
mmol) in anhyd toluene (40 mL) were added tributyl(vinyl)tin (29.3
g, 92.5 mmol) and Pd(PPh3)4 (0.98 g, 0.85 mmol). The mixture was
stirred for 15 h at 80 °C. After cooling, an aq 1 M KF solution (80
mL) was added. The mixture was stirred for 2 h, then diluted with
EtOAc (150 mL), and filtered on Celite. The organic layer was sep-
arated from the filtrate, dried (MgSO4), and concentrated to dry-
ness. The residue was dissolved in MeCN (100 mL) and washed
with petroleum ether (3 × 40 mL). The MeCN phase was extracted
continuously with petroleum ether for 4 days. Upon concentration
of the petroleum ether, the product precipitated. After filtration and
drying in vacuo, pure 2b was obtained as an orange powder; yield:
4.16 g (44%); mp 64–68 °C.
The method used for 2a (Scheme 1, Procedure 1) was fur-
ther extended to the synthesis of two related compounds:
1,3-dinitro-4,6-divinylbenzene (2b) (Scheme 1, Proce-
dure 2) and 1-nitro-2,5-divinylbenzene (2c) (Scheme 1,
Procedure 3). The previously unknown 2b polymerized
very easily and was therefore isolated as for 2a. The yield
was 44% in one step from the commercially available 4,6-
dichloro-1,3-dinitrobenzene (1b). The unique combina-
tion of two nitro and vinyl groups in 2b makes it an inter-
esting building block. As a matter of fact, the use of 2b as
a co-monomer would allow the synthesis of cross-linked
polymers with energetic properties. Compound 2c was
much less prone to polymerization than 2a,b. Therefore,
the continuous extraction method was not needed and
pure 2c was easily obtained in good yield (88%) after
flash chromatography. This synthesis of 2c avoids the use
of pressure, which was the main drawback of the reported
procedure.10
IR: 3115, 2988, 1889, 1603, 1579, 1516, 1419, 1343, 1156, 979,
944, 908, 894, 832 cm–1.
1H NMR (200 MHz, CDCl3): d = 5.73 (d, J = 11.4 Hz, 2 H, 2 Hbcis),
6.21 (d, J = 17.3 Hz, 2 H, 2 Hbtrans), 7.09 (dd, J = 11.4, 17.3 Hz, 2
H, 2 Ha), 8.08 (s, 1 H, H-5), 8.62 (s, 1 H, H-2).
13C NMR (50 MHz, CDCl3): d = 121.5, 123.2, 128.1, 130.6, 136.5,
145.7.
Anal. Calcd for C10H8N2O4: C, 54.55; H, 3.66; N, 12.72. Found: C,
55.24; H, 3.72; N, 12.65.
Procedure 3
1-Nitro-2,5-divinylbenzene (2c)10
To a solution of 2,5-dibromo-1-nitrobenzene (1c; 1.12 g, 4 mmol)
and 2,6-di-tert-butyl-4-methylphenol (9 mg, 0.04 mmol) in anhyd
toluene (10 mL) were added tributyl(vinyl)tin (2.63 mL, 9 mmol)
and Pd(PPh3)4 (139 mg, 0.12 mmol). The mixture was stirred for 8
h at 110 °C. After cooling, an aq 1 M KF solution (27 mL) was add-
ed. The mixture was stirred for 2 h, and then filtered on Celite. The
organic layer was separated from the filtrate, dried (MgSO4), and
concentrated to dryness. The residue was chromatographed over sil-
ica gel (eluent: heptane–EtOAc, 8:2) to give pure 2c as a yellow oil;
yield: 0.62 g (88%).
NMR measurements were performed at r.t. on a Bruker Avance 200
spectrometer. IR spectra were recorded with an attenuated total re-
flectance Perkin-Elmer SpectrumOne spectrometer. Melting points
were determined on a Kofler apparatus and are uncorrected. Ele-
mental analyses were performed on a ThermoFisher Scientific
Flash EA 1112CHNS/O apparatus. All reactions were performed
under N2. Anhydrous toluene and Pd(PPh3)4 were purchased from
Aldrich and were used as received. Petroleum ether used refers to
the fraction boiling in the range 30–60 °C.
IR: 3092, 1848, 1737, 1626, 1547, 1522, 1493, 1344, 1309, 1288,
983, 915, 843, 806 cm–1.
1H NMR (200 MHz, CDCl3): d = 5.42 (d, J = 10.9 Hz, 1 H, Hbcis),
5.47 (d, J = 10.9 Hz, 1 H, Hbcis), 5.75 (d, J = 17.1 Hz, 1 H, Hbtrans),
Synthesis 2008, No. 11, 1805–1807 © Thieme Stuttgart · New York

PRACTICAL SYNTHETIC PROCEDURES
2,4-Dinitrostyrene and Related (Di)nitrodivinylbenzenes
1807
5.85 (d, J = 17.1 Hz, 1 H, Hbtrans), 6.70 (dd, J = 10.9, 17.1 Hz, 1 H,
Ha), 7.13 (dd, J = 10.9, 17.1 Hz, 1 H, Ha), 7.58 (m, 2 H, H-3 + H-
4), 7.91 (s, 1 H, H-6).
13C NMR (50 MHz, CDCl3): d = 116.7, 118.7, 121.8, 128.4, 130.3,
131.9, 132.0, 134.3, 138.1, 148.0.
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Synthesis 2008, No. 11, 1805–1807 © Thieme Stuttgart · New York