Synthesis of para-substituted styrenes

Article abstract of DOI:10.1016/S0040-4039(03)00027-3

Using double Stille cross-coupling reaction bromo (or chloro)benzylbromide is easily transformed into substituted styrene monomers bearing a wide range of substituents in para position

Full text of DOI:10.1016/S0040-4039(03)00027-3

TETRAHEDRON
LETTERS
Pergamon
Tetrahedron Letters 44 (2003) 1647–1649
Synthesis of para-substituted styrenes
Sandrine Langle, Franck David-Quillot, Mohamed Abarbri and Alain Ducheˆne*
Laboratoire de Physicochimie des Interfaces et des Milieux Re´actionnels, Faculte´ des Sciences de Tours, Parc de Grandmont,
F-37200 Tours, France
Received 19 November 2002; revised 20 December 2002; accepted 20 December 2002
Abstract—Using double Stille cross-coupling reaction bromo (or chloro)benzylbromide is easily transformed into substituted
styrene monomers bearing a wide range of substituents in para position © 2003 Elsevier Science Ltd. All rights reserved.
In continuation of our work on the synthesis of organic
materials (Inertial Confinement Fusion program)1 in
the form of co-polymer polystyrene-modified-
polystyrene in which the modified polystyrene is made
from styrene monomers substituted in the para position
by a spacer bearing an atom of the 14 group (Si, Ge or
Sn), this type of monomer was required for polymerisa-
tion in order to test the physical properties of the
co-polymers obtained. We have already described the
synthesis of such styrene monomers with an n=0 or 1
carbon spacer between the aromatic group and an atom
of the 14 group under ultrasound conditions.2 A possi-
ble method to introduce a three carbon spacer (n=3)
between the phenyl group and the trialkyl(or
triphenyl)metal group is shown in the retrosynthetic
scheme below (Scheme 1).
As can be seen in Scheme 1, vinyltin reagents are good
candidates for such synthesis and have proved to be
efficient tools for the transfer of a vinyl unit, with high
tolerance of numerous functions both on the substrate
and on the reagent.3 The other reagent needed as
starting material for such a synthesis is p-bromo-
(chloro)benzyl bromide which is inexpensive.
In view of the surprising lack of literature reports on
the reactivity of the two bromine atoms of p-bromo-
benzyl bromide and recognizing that a chemoselective
reaction could be useful, we decided to take a close
look at the substitution reaction under Stille cross-cou-
pling reaction4 in the presence of palladium complex
catalysis.5 We started from vinyltin compounds bearing
a trialkylsilyl, trialkyl (or triphenyl)germyl or a tributyl-
Scheme 1.
Scheme 2.
Keywords: styrenes; palladium catalyst; coupling reactions.
* Corresponding author. Fax: +33 (0)2 47 36 69 60; e-mail: duchene@delphi.phys.univ-tours.fr
0040-4039/03/$ - see front matter © 2003 Elsevier Science Ltd. All rights reserved.
PII: S0040-4039(03)00027-3

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S. Langle et al. / Tetrahedron Letters 44 (2003) 1647–1649
Table 1.
stannyl group at the b-position. These compounds are
obtained by hydrostannation of the corresponding alky-
nes under the experimental conditions used for the
synthesis of (E)-1,2-bis(tributylstannyl)ethylene.6 We are
able to selectively substitute only the bromine atom in the
benzylic position if we use 1 equiv. of the starting vinyltin,
toluene as solvent and 3% mol of tetrakis(triphenyl-
phosphine) palladium(0) as catalyst (Scheme 2, Table 1).
Only the MR3 group is transferred and no competition
occurs with the possible transfer of the vinylstannyl unit
(entries 1–5).6c,7
Entry
MR3
X
Yield (%)
No
1
2
3
4
5
6
SiMe3
SiMe3
GeEt3
GeEt3
GePh3
SnBu3
Cl
Br
Cl
Br
Br
Br
68
78
76
80
67
25
1a
1b
1c
1d
1e
1f
Table 2.
Scheme 3.

S. Langle et al. / Tetrahedron Letters 44 (2003) 1647–1649
1649
As seen in the results reported in Table 1, we neither
obtain bis-coupling products,8 nor allylic compounds
resulting from the conjugation of the external double
bond with the aromatic ring, when the concentration of
the solution is around 0.5 M. We also observe retention
of the configuration of the double bond.
Chem. 1981, 46, 5221; (c) Thibonnet, J.; Abarbri, M.;
Parrain, J.-L.; Ducheˆne, A. Synlett 1997, 1771; (d)
Lukevics, E.; Arsenyan, P.; Fleisher, M.; Popelis, J.;
Pudova, O. Main Group Metal Chem. 1999, 22, 655.
7. Representative general procedure: 0.04 g (3% mol) of tetra-
kis(triphenylphosphine)palladium(0) was added to a tolu-
ene solution (15 mL) of organic halide (1.15 mmol) after
stirring for 15 min, 1.25 mmol of (E)-1-tributylstannyl-2-
trialkyl (or triphenenyl)germylethylene diluted in 10 mL of
toluene were added dropwise. The mixture was stirred
overnight at 80°C. After cooling, the reaction mixture was
filtered through a Celite path, and toluene was evaporated
under reduced pressure. The residue was then treated with
a 1 M solution of potassium fluoride and ethylacetate to
eliminate the tributyltin halide thus formed. The aqueous
layer was extracted with diethyl ether. The organic layer
was washed with brine and dried over MgSO4. After
evaporation of the solvents, the crude product was purified
by column chromatography on silica gel (petroleum ether/
triethylamine: 98/2). 1b: 1H NMR l ppm (CDCl3, 200
MHz): 0.12 (s, 9H), 3.45 (dd, J=6.1 Hz, J=1.5 Hz, 2H),
5.75 (dt, J=18.4 Hz, J=1.5 Hz, 1H), 6.17 (dt, J=18.4 Hz,
J=6.1 Hz, 1H), 7.10 (m, 2H), 7.47 (m, 2Har, m); 13C
NMR l ppm (CDCl3, 50 MHz): −1.2 (3C), 42.5, 119.8,
130.5, 131.4, 132.0, 138.8, 144.4; MS (70 eV) m/z: 255
Another clean second substitution is also possible under
Stille cross-coupling reaction providing as required
acceptable yields of the new styrene monomers 2a–h
with an n=3 spacer between the aromatic group and
the metal (Scheme 3).9 The results are presented in
Table 2.
In conclusion we report, through a double cross-cou-
pling reaction, the synthesis of styrenes substituted in
the para position by a wide range of substituents, with
good overall yields, from commercially available bromo-
benzyl bromide. Some of the new compounds are cur-
rently tested for copolymerisation with styrene and
provide promising results in terms of molecular weight,
low polydispersity and physical properties (mechanical,
thermal and solubility).
Acknowledgements
+
’
+
’
(M −15, 26), 253 (M −15, 26), 159 (12), 137 (10), 116
(31), 115 (18), 90 (13), 89 (12), 74 (10), 73 (100), 59 (67), 58
(14), 45 (25), 43 (28). 1d: 1H NMR l ppm (CDCl3, 200
MHz): 0.86 (q, J=6.4 Hz, 6H), 1.06 (t, J=7.2 Hz, 9H),
3.46 (d, J=5.8 Hz, 2H), 5.82 (d, J=18.2 Hz, 1H), 6.06 (dt,
J=18.2 Hz, J=5.8 Hz, 1H), 7.10 (d, J=8 Hz, 2H), 7.45
(d, J=8 Hz, 2H); 13C NMR l ppm (CDCl3, 50 MHz): 4.7
We thank the CNRS and MRT for providing financial
support, and the ‘Service d’analyse chimique du Vivant
de Tours’ for recording NMR and mass spectra.
(3C), 9.3 (3C), 43.0, 120.1, 129.0, 129.6, 130.8 (2C), 131.8
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’
(2C), 139.6, 144.1; MS (70 eV) m/z: 358 (M −, 15), 356
+
’
(M −, 13), 211 (27), 209 (30), 102 (100), 91 (16).
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5.26 (dd, J=10.8 Hz, J=0.8 Hz, 1H), 5.77 (dd, J=17.6
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J=8.1 Hz, 2H); 13C NMR l ppm (CDCl3, 50 MHz): 4.8
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+
’
135.8, 137.1, 140.5, 144.7; MS (70 eV) m/z: 304 (M , 8),
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