Oxidative cross-coupling of vinylsilanes in water

Article abstract of DOI:10.1016/j.jorganchem.2013.01.021

Palladium-promoted cross-dimerization reaction of alkenylsilanes is reported for the first time, which is also one of the very first studies on oxidative cross-coupling between vinylic organometallic reagents. The reaction occurs at room temperature in aqueous micelles and represents a convenient access to all-trans push-pull butadienes.

Full text of DOI:10.1016/j.jorganchem.2013.01.021

Accepted Manuscript
Oxidative Cross-Coupling of Vinylsilanes in Water
Stefania R. Cicco, Carmela Martinelli, Vita Pinto, Francesco Naso, Gianluca Maria
Farinola, Ph. D
PII:
S0022-328X(13)00048-X
10.1016/j.jorganchem.2013.01.021
JOM 17867
DOI:
Reference:
To appear in: Journal of Organometallic Chemistry
Received Date: 15 November 2012
Revised Date: 18 January 2013
Accepted Date: 23 January 2013
Please cite this article as: S.R. Cicco, C. Martinelli, V. Pinto, F. Naso, G.M. Farinola, Oxidative
Cross-Coupling of Vinylsilanes in Water, Journal of Organometallic Chemistry (2013), doi: 10.1016/
j.jorganchem.2013.01.021.
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ACCEPTED MANUSCRIPT
R1
SiMe3
R1
Pd(II)
H2
R1= OCH3, N(Me2), CH3, SCH3, H
+
R2
O
R2
Me3Si
R
2 = NO2, COPh, F

ACCEPTED MANUSCRIPT
Title: Oxidative Cross-Coupling of Vinylsilanes in Water
Keywords: Cross-coupling; Oxidative Cross-coupling; Vinylsilanes; Reactions in
Water; Palladium
Corresponding Author: Prof. Gianluca Maria Farinola, Ph. D.
Università degli Studi di Bari "Aldo Moro", Via Orabona
4, 70126 Bari, Italy
Contact Informations: Mail: farinola@chimica.uniba.it
Tel:+390805442064
First Author: Stefania R. Cicco, Dr
CNR-ICCOM –(Bari), Via Orabona 4, 70126 Bari, Italy
All Authors:
Stefania R Cicco, Dr;
Carmela Martinelli, Dr( Affiliation: Università degli Studi di Bari "Aldo Moro", Via
Orabona 4, 70126 Bari, Italy)
Vita Pinto, Dr; (Università degli Studi di Bari "Aldo Moro", Via Orabona 4, 70126
Bari, Italy)
Francesco Naso, Prof. (Università degli Studi di Bari "Aldo Moro", Via Orabona 4,
70126 Bari, Italy)
Abstract: Palladium-promoted cross-dimerization reaction of alkenylsilanes is
reported for the first time, which is also one of the very first studies on oxidative
cross-coupling between vinylic organometallic reagents. The reaction occurs at
room temperature in aqueous micelles and represents a convenient access to
all-trans push-pull butadienes.

ACCEPTED MANUSCRIPT
The first investigation of palladium-catalyzed oxidative cross-coupling reaction of vinylsilanes
bearing substituents with complementary electronic effects is reported. Besides being the first
example on oxidative cross-coupling of vinylic organosilicon reagents, the protocol is a convenient
access to push-pull butadienes.

ACCEPTED MANUSCRIPT
1. Introduction
Therefore, we adopted the same reaction protocol10 for the first
experiments of cross-dimerization between two different styryl
silanes 1a and 1b bearing the electron-donating methoxy group
and the electron-withdrawing nitro group, respectively (Scheme
Transition metal catalyzed cross-coupling reactions of C-sp2-
organometallic reagents with unsaturated electrophiles have been
widely investigated as an effective tool for C-C bond formation1
and are commonly used to build extended polyconjugated
systems of interest in materials science.2 Conversely, the study of
oxidative cross-coupling processes between organometallic
reagents is still at an early stage, in spite of their great potential in
organic synthesis.3 In particular, reports on Csp2-Csp2 bond
formation by this class of reaction are mainly limited to the
synthesis of biaryl compounds,4 stimulated by their applications
in materials science and medicinal chemistry.5
1).
Me3Si
+
CH3
O
NO2
SiMe3
1a
1b
PdCl2
CuCl2/LiCl
"H2O"
NO2
OCH3
NO2
+
O2
N
+
CH3
O
CH3
O
1''
9%
1'
14%
1
60%
To the best of our knowledge, no systematic investigation on
transition metal-catalyzed oxidative cross-coupling between vinyl
organometallic reagents has been reported so far, although the
occurrence of products of cross-dimerization was mentioned in a
study by Stefani et al. on the relative reaction rates in palladium-
catalyzed homocoupling of potassium alkenyltrifluoroborates.6
Scheme 1. Pd-catalyzed oxidative cross-coupling reaction of 1a and 1b.
Compound 1, resulting from the cross-coupling process, was
obtained as the major product (60% yield) (Table 1, entry 1)
together with lower amounts of the two homocoupling products
(14 % 1’ and 9% 1’’). The (E,E)-dienes were obtained as pure
isomers as demonstrated by 1H NMR spectroscopy.
As a part of our research efforts on the development of
efficient organometallic methods for the synthesis of conjugated
oligomers and polymers for photonics and electronics,2,7 and, in
particular, of protocols based on the use of alkenylsilanes,8 we
reported a PdCl2/CuCl2/LiCl-promoted homocoupling reaction of
vinylsilanes, useful to build extended polyenic systems.9 More
recently, we have described a micellar version of the same
process with significantly improved outcome for the synthesis of
symmetric 1,4-diarylbutadienes.10
The result of this first experiment clearly shows a remarkable
selectivity for the oxidative coupling in favor of the cross-
coupling product. The same reaction carried out in MeOH
afforded a lower yield of the cross-coupling compound 1 (45%)
as well as of the homocoupling reaction products (10% 1’ and
7% 1’’), but the same ratio between the three compounds was
maintained, confirming the selectivity and also the advantage of
the micellar environment over the MeOH reaction medium. In
fact, according to our previous report,10 the micellar system
prevents the formations of protodesilylation byproducts thus
leading to higher yields of the 1,4-disubstituted 1,3-butadienes.
Starting from these previous reports, we decided to investigate
the coupling of different vinylsilanes, and herein we describe the
results of our study demonstrating the first oxidative cross-
coupling reaction between two vinylic organosilicon reagents,
which also turns out to be one of the very first reports on
oxidative cross-coupling between alkenyl organometallic
reagents.
Encouraged by these interesting results, we decided to extend the
study to other styrylsilanes bearing substituents with different
electronic effects on the phenyl rings. The general equation of the
reaction is shown in the Scheme 2.
2. Results and Discussion
In a previous paper,9 we had systematically studied a reaction
protocol which delivers satisfactory yields in the highly
stereoselective homocoupling reaction of vinylsilanes promoted
by Pd(II). The presence of a large excess of CuCl2 and LiCl is
required to reoxidize the Pd(0) generated in the reductive
elimination step leading to the butadienic system formation.
Notably, the reactions can also be carried out in water in the
presence of the non ionic surfactant TRITON X-100 (15% wt)
(Figure 1) with improved outcomes.10
G2
SiMe3
G1
+
Me3Si
PdCl2
CuCl2/LiCl
"H2O"
G2
G2
G1
G1
G2
G1
+
+
1''-6''
1-6
1'-6'
Scheme 2. Pd-catalyzed oxidative cross-coupling of styryl silanes in water.
Fig. 1. Structure of Triton X-100

ACCEPTED MANUSCRIPT
Table 1. Oxidative cross coupling reaction of G1-substituted
styryl silanes with G2-substituted styryl silanes
The unsymmetrical substituted 1,3-butadienes 1-2 and 4-7
obtained are listed in Figure 2. In fact, the method disclosed here
offers convenient synthetic access to stereodefined all trans push-
pull butadienes, a class of molecules widely employed as active
materials in organic photonics.11
Entry[a]
G1
G2
Product Yield[b] Ratio[c] T(h)
1
OCH3
(1a)
NO2
(1b)
1
2
3
4
5
6
60
65
-
72:17:11 12
N(CH3)2
OCH3
2
3
4
5
6
N(Me)2
(2a)
NO2
(1b)
74:16:10 12
O2N
O2N
O2N
4
2
1
F
F
CH3O
SCH3
(3a)
NO2
(1b)
-
-
O2N
CH3O
O
7
5
6
CH3
(4a)
NO2
(1b)
58
55
50
70:18:12 24
67:19:14 24
68:18:14 24
Fig. 2. 1,4-Disubstitued-1,3-butadienes 1-7 synthesized
H
(5a)
NO2
(1b)
Starting from the mechanistic path postulated for the
homocoupling process of vinylsilanes,12 we can speculate that the
initial electrophilic addition of PdCl2 occurs preferentially on the
more electron-rich double bond, thus generating the β-
styrylpalladium chloride intermediate of the electron-donor
substituted olefin as the most abundant intermediate. Such
intermediate would then undergo electrophilic addition to the
electron-poor residual vinylsilane, remaining as the most
abundant in the reaction mixture, thus generating preferentially
the asymmetric butadienes upon the last reductive elimination
step with Pd(0) release.
OCH3
3,5-diF
(1a)
(2b)
[a] Reactions carried out at room temperature in 15% wt Triton
X-100/H2O; the catalytic system consists of PdCl2/LiCl/CuCl2
with a molar ratio 1:3:8 optimized in previous studies.9,10 [b]
Based on isolated materials. [c] This value indicates the cross-
coupling G1-G2: self-coupling G1-G1: self-coupling G2-G2
products ratio.
The results summarized in Table 1 show similar chemoselectivity
in all the reactions investigated, which is only slightly affected by
the nature of the electron-donating and electron-withdrawing
substituents. The cross-coupling compounds were always
obtained as the main reaction products in fair to good yields (50-
65%) and the ratio of the unsymmetrical butadienes vs the two
symmetrical products was similar in all cases. The only exception
is represented by compound 3a substituted with the SCH3 group
(entry 3). In this case no reaction was observed, which is likely to
be due to the poisoning effect of the sulfur atom on the catalytic
system. The reaction of the substrates functionalized with the
strongly electron-donating (1a, 2a) and electron-withdrawing
(1b) substituents went to completion in 12 hours, while a rate
retarding effect was observed by decreasing the electron-donating
strength of the substituent (4a) or removing it (5a). Similarly, a
24 hours reaction time was necessary to lead to completion the
reaction involving the difluorosubstituted styrylsilane (2b).
The substituted styryl silanes 1a-5a and 1b-3b used as starting
materials were prepared with various organometallic methods, as
shown in the Experimental Section.
3. Conclusions
In summary, we have reported the first systematic investigation
on oxidative cross-coupling of vinylsilanes functionalized with
substituents with complementary electronic effects. Besides
being the first report on the oxidative cross-coupling of vinyl
organosilicon reagents, this is one of the very first investigations
on oxidative cross-coupling between alkenyl organometallic
reagents. Moreover, this procedure turns out to be a convenient
synthesis of all-trans unsymmetrical 1,4-disubstituted-1,3-
butadienes carried out in water at room temperature, affording
push-pull butadienic systems, with the distinctive advantages of
operational simplicity and low toxicity starting materials.
Cross-coupling product 7 (Scheme 3) was obtained from the
reaction of the 2-ketovinyltrimethyl silane 3b with 1a, with a
selectivity similar to that observed in the case of the styrylsilanes,
in 24 hours reaction time.
Experimental
O
SiMe3
All chemicals were purchased from Aldrich, Alfa Aesar and
Acros and used without further purification. (E)-1-
(tributylstannyl)-2-(trimethylsilyl)ethene 813 and (E)-trimethyl-
(4-methylstyryl)silane10 4a were prepared as reported in the
literature.
Me3Si
+
CH3O
3b
1a
PdCl2
CuCl2/LiCl
"H2O"
OCH3
O
O
+
+
Column chromatography was performed by using silica gel 60
(0.04-0.063 mm) from Merck. Petroleum ether was the 40-70 °C
boiling fraction. Thin-layer-cromatography analysis was
conducted using Merck Silica gel 60 F254 aluminium sheets. GC
O
CH3O
CH3O
7''
1'
7
60%
10%
13%
Scheme 3. Cross-coupling reaction with the ketosilane 3b

ACCEPTED MANUSCRIPT
Anal. Calcd. for C13H21NSi (219.40): C 71.70, H 9.64, N 6.38.
Found: C 71. 81, H 9.78, N 6.43.
analysis was performed with Varian 3900 (dimethylpolysiloxane
30 m x 25 mm x 0.25 µm). MS spectra were acquired on a
Shimadzu GCMS-QP 5000 spectrometer. 1H and 13C NMR
(E)-(Styryl)trimethylsilane (5a). Following the same procedure
used to prepare 1a, the silane 5a was prepared starting from (E)-
(2-bromovinyl)trimethylsilane (3.0 g, 16.8 mmol), NiCl2(dppe)
(0.44 g, 0.84 mmol) and 4-phenylmagnesium bromide (N=0.54 in
THF, 37 ml, 20 mmol). The pure product was isolated as a
colourless oil after purification by column chromatography by
using petroleum ether as eluent (2.6 g, 87 %).
spectra were recorded in CDCl3 on
spectrometer at 500 MHz and 125 MHz, respectively. The
a Bruker AM 500
residual CHCl3 signal at δ=7.24 ppm and the CDCl3 signal at
1
δ=77.0 ppm were used as standards for H NMR and 13C NMR
spectra, respectively. 19F NMR spectra were recorded in CDCl3
on a Varian Inova 400 spectrometer at 376 MHz, using CFCl3 as
internal standard. FT-IR spectra were measured on a Perkin-
Elmer 1710 spectrofotometer using dry KBr pellets. Elemental
analyses were done by a Carlo Erba CHNS-O EA1108-Elemental
Analyzer. Melting points were determined on a Gallenkamp
capillary melting points apparatus.
The characterization of the product 5a is in agreement with the
data reported in the literature.14
MS (EI, 70 eV) m/z (%): 176 [M+], 161 (100), 145 (61), 135 (13),
73 (8). FTIR (KBr): 2956, 1606, 1466, 1248, 988, 866, 843, 756,
723, 691 cm-1. 1H NMR: δ 7.47-7.52 (m, 2H), 7.33-7.41 (m, 2H),
7.22-7.33 (m, 1H), 6.95 (d, J=19.1 Hz, 1H), 6,55 (d, J=19.1 Hz,
1H), 0.18 (s, 9H) ppm. 13C NMR: δ = 143.7, 138.4, 129.5, 128.6,
128.0, 126.4, 1.1 ppm.
CHCl3 was distilled from P2O5 under a nitrogen atmosphere;
THF, Et2O and toluene were distilled over sodium and
benzophenone under a nitrogen atmosphere, immediately prior to
use. Methanol was degassed by bubbling nitrogen for 30 minutes,
prior to use.
(E)-(4-Nitrostyryl)trimethylsilane (1b). A three neck 100 mL
round bottom flask equipped with a magnetic stir bar was
charged with dry toluene (60 ml), (E)-1-(tributylstannyl)-2-
(trimethylsilyl)ethene 8 (2 g, 5.14 mmol), 1-iodo-4-nitrobenzene
(1.28 g, 5.14 mmol) and tetrakis(triphenylphosphine)
palladium(0) (0.29 g, 0.25 mol), under a nitrogen atmosphere.
The resulting mixture was refluxed overnight. The reaction
mixture was quenched with water and extracted with ethyl
acetate (3 x 50 mL). The organic layers were combined and dried
over anhydrous Na2SO4 and the solvent was evaporated under
reduced pressure. The crude product was purified by column
chromatography using petroleum ether/ethyl acetate 9:1 as
eluent, to give the pure product a pale yellow solid (0.97 g, 85
%). The characterization of the product 1b is in agreement with
the data reported in the literature.15 M. p.= 37-39 °C (Water).
MS (EI, 70 eV) m/z (%): 221 [M+], 206 (67), 160 (58), 147 (100),
145 (75), 117 (17), 115 (20), 75 (3). FTIR (KBr): 2956, 1591,
(E)-(4-Methoxystyryl)trimethylsilane (1a). A three neck 250 ml
round bottom flask equipped with a magnetic stir bar and 100 ml
dropping
funnel
was
charged
with
(E)-(2-
bromovinyl)trimethylsilane (4.9 g, 27.35 mmol), NiCl2(dppe)
(0.84 g, 1.37 mmol) and 100 ml of freshly distilled THF. The
solution was cooled to 0°C and p-methoxyphenylmagnesium
bromide (0.32 N in THF, 100 ml, 32 mmol) was added dropwise.
The solution was maintained at 0°C during the addition and then
warmed to room temperature overnight. The reaction mixture
was then quenched with water and extracted twice with diethyl
ether. The organic layer was dried by using anhydrous Na2SO4,
filtered and concentrated at reduced pressure. The pure product
was isolated as a white solid after purification by column
chromatography on silica gel using petroleum ether/ethyl acetate
(9.6:0.4) as eluent (4.84 g, 86 %).
1
1521, 1341, 1240, 1109, 993, 861, 839, 750 cm-1. H NMR: δ
8.16-8.21 (m, 2H), 7.53-7.57 (m, 2H), 6.91 (d, J=19.1 Hz, 1H),
6.71 (d, J=19.1 Hz, 1H), 0.18 (s, 9H) ppm. 13C NMR: δ = 147.1,
144.4, 141.2, 136.2, 126.9, 124.0, 1.2 ppm.
The characterization of the product 1a is in agreement with the
data reported in the literature.14 M.p.= 50-52°C (Methanol). MS
(EI, 70 eV) m/z (%)= 206 [M+], 191 (100), 175 (43), 165 (30),
145 (7), 131 (6), 73 (5). FTIR (KBr): 2955, 1606, 1249, 1033,
992, 835, 801 cm-1. 1H NMR: δ 7.4 (d, J=8.5 Hz, 2H), 6.88 (d, J=
8.5 Hz, 2H), 6.84 (d, J= 19.1 Hz, 1H), 6.33 (d, J=19.1 Hz, 1H),
3.82 (s, 3H), 0.12 (s, 9H) ppm. 13C NMR: δ = 159.4, 142.9,
131.2, 127.5, 126.6, 113.8, 55.2, 1.1 ppm.
(E)-[4-(Methylthio)styryl]trimethylsilane (3a). Following the
same procedure used to prepare 1b, the silane 3a was prepared
starting from (E)-1-(tributylstannyl)-2-(trimethylsilyl)ethene 8
(1.5 g, 3.86 mmol), 4-bromo-1-methylthiobenzene (0.78 g, 3.85
mmol) tetrakis(triphenylphosphine)palladium(0) (0.22 g, 0.19
mmol) and dry THF (30 mL). The reaction mixture was
quenched with water and extracted with ethyl acetate (3 x 30
mL). The organic layers were combined and dried over
anhydrous Na2SO4 and the solvent was evaporated under reduced
pressure. The crude product was purified by column
chromatography using petroleum ether as eluent, to give the pure
product as a colourless oil (0.45 g, 53 %). MS (EI, 70 eV) m/z
(%): 222 [M+], 207 (100), 177 (52), 145 (9), 115 (10), 73 (5).
FTIR( KBr): 2956, 2922, 1602, 1490, 1247, 985, 866, 834, 790
(E)-[4-(N,N-Dimethylamino)styryl]trimethylsilane
(2a).
Following the same procedure used to prepare 1a, the silane 2a
was prepared starting from (E)-(2-bromovinyl)trimethylsilane
(3.0 g, 16.8 mmol), NiCl2(dppe) (0.44 g, 0.84 mmol) and 4-N,N
dimethylaminophenylmagnesium bromide (0.33 N in THF, 60
ml, 20 mmol). The pure product was isolated as a white solid
after purification by column chromatography using petroleum
ether/ethyl acetate (9:1) as eluent (2.85 g, 78 %). M.p.= 48-50°C
(Methanol).
1
cm-1. H NMR: δ 7.18-7.22 (m, 4H), 6.81 (d, J= 19.1 Hz, 1H),
6.41 (d, J= 19.1 Hz, 1H), 2.48 (s, 3H), 0.09 (s, 9H) ppm. 13C
NMR: δ = 142.9, 138.2, 136.2, 134.6, 128.9, 126.6, 15.9, 1.2
ppm. Anal. Calcd. for C12H18SSi (222.42): C 64.80, H 8.16, S
14.42. Found: C 65.11, H 8.93, S 14.77.
MS (EI, 70 eV) m/z (%)= 219 [M+] (100), 204 (99), 188 (16), 178
(23), 144 (7). FTIR (KBr): 2953, 1607, 1520, 1360, 1259, 1244,
1182, 1096, 1065, 1022, 986, 791, 727 cm-1. H NMR: δ 7.32-
1
7.37 (m, 2H), 6.81 (d, J=19.1 Hz, 1H), 6.64-6.73 (m, 2H), 6.22
(d, J=19.1 Hz, 1H), 2.97 (s, 6H), 0.151 (s, 9H) ppm. 13C NMR: δ
= 150.2, 143.4, 136.5, 127.3, 127.1, 112.3, 40.5, 1.0 ppm.
(E)-1-Phenyl-3-(trimethylsilyl)-propen-1-one (3b). To 50 mL of
previously degassed chloroform was added PdCl2(dppf) (0.21g,

ACCEPTED MANUSCRIPT
MS (EI, 70 eV) m/z (%): 281 [M+] (100), 250 (31), 234 (25), 219
0.25 g, 0,25 mmol), benzoylchloride (1.0 g, 5.07 mmol) and (E)-
1-(tributylstannyl)-2-(trimethylsilyl)ethene (2.15 g, 5.5 mmol).
The mixture was stirred under a nitrogen atmosphere for 2 days
at room temperature. The reaction mixture was quenched with
water and extracted with dichloromethane (3x 30 mL). The
organic layer was washed with water (3 x 50 mL) and dried over
anhydrous Na2SO4, and the solvent evaporated at reduced
pressure. The residue was purified by column chromatography
using petroleum ether/ethyl acetate (9:1) as eluent to yield the
pure product as a pale yellow oil (0.83 g, 80%).
(22), 204(24), 189 (27), 115 (10). FTIR (KBr): 2956, 2834, 1585,
1504, 1463, 1325, 1250, 1171, 1106, 1036, 980, 853, 806, 746
cm-1. 1H NMR: δ= 8.21-8.10 (m, 2H), 7.55-7.51 (m, 2H), 7.38-
7.34 (m, 2H), 7.19-7.15 (m, 2H), 7.15-7.05 (m, 1H), 6.96-6.89
(m, 1H), 6.77 (d, J= 15.5 Hz, 1H), 6,67 (d, J= 15.5 Hz, 1H), 2.36
(3H, s) ppm. 13C NMR: δ= 147.2, 144.9, 136.8, 136.5, 133.8,
130.4, 129.0, 128.4, 128.2, 126.6, 126.5, 123.3, 56.5 ppm. M.p.=
176-177 °C (Methanol). Anal. Calcd. for C17H15NO3 (281.31): C
72.58, H 5.37, N 4.98. Found: C 72.81, H 5.41, N 5.16.
The self-coupling product (1E,3E)-1,4-di(4-methoxyphenyl)-1,3-
butadiene (1’)6 was recovered as a white solid (0.03g, 14%). MS
(70 eV) m/z (%): 266 [M+], 251 (22), 236 (16), 220 (19), 209
(26), 207 (100), 191(28). FTIR (KBr): 2923, 2852, 1600, 1508,
The characterization of the product 3b is in agreement with the
data reported in the literature.16
MS (EI, 70 eV) m/z (%): 204 [M+], 189 (100), 161 (10), 105 (16),
73 (16). FTIR (KBr): 3062, 3032, 2955, 2893, 1665, 1608, 1577,
1
1462, 1256, 1176, 1110, 1028, 985, 847, 800 cm-1. H NMR: δ=
1
1450, 1244, 1180, 1010, 873, 855, 750, 690 cm-1. H NMR: δ =
7.36 (d, J= 8.7 Hz, 4H), 6.87 (d, J= 8.7 Hz, 4H), 6.81 (dd, J=
11.9, 2,8 Hz, 2H), 6.58 (dd, J= 11.9, 2.8 Hz, 2H), 3,82 (s, 6H)
ppm. 13C NMR: δ=159.1, 131.3, 130,4, 127.5, 127.4, 114.1, 55.3
ppm. M.p.= 221-223 °C (Ethanol).
7.95-7.91 (m, 2H), 7.57-7.51 (m, 1H), 7.48-7.43 (m, 2H), 7.33-
7.21 (m, 2H), 0.19 (s, 9H) ppm. 13C NMR: δ = 193.4, 149.6,
138.1, 137.5, 132.7, 128.9, 128.6, 0.9 ppm.
The self-coupling product (1E,3E)-1,4-di(4-nitrophenyl)-1,3-
butadiene (1’’) was recovered as a yellowish solid (0.02 g, 9%)
MS (70 eV) m/z (%): 296 [M+], 281 (29), 279 (21), 249 (49), 207
(100), 202 (51), 191 (38). FTIR (KBr): 2918, 2850, 1592, 1505,
1377, 1109, 984, 861 cm-1. 1H NMR: δ= 8.22 (d, J= 8.9 Hz, 4H),
7,59 (d, J= 8.8 Hz, 4H), 7.11 (dd, J= 11.9, 2.9 Hz, 2H), 6.83 (dd,
J= 11.6, 2.7 Hz, 2H) ppm. 13C NMR: δ= 147.1, 143.1, 133.1,
132.5, 127.1, 124.2 ppm. M.p.= 272-273°C (Water).
(E)-(3,5-Difluorostyryl)trimethylsilane (2b). A three-neck 100 ml
round bottom flask containing a magnetic stirrer was charged
under a nitrogen atmosphere with 3,5-difluorophenyl boronic
acid (0.88 g, 5.54 mmol), (E)-(2-bromovinyl)trimethylsilane
(0.83 g, 4.64 mmol), tetrakis(triphenylphosphine)palladium(0)
(0.16 g, 0.14 mmol), dry toluene (40 mL), methanol (10 mL) and
sodium carbonate 2M (30 mL). The resulting mixture was stirred
at 110 °C and the reaction was monitored by GC-MS until the
disappearance of (E)-(2-bromovinyl)trimethylsilane. The reaction
mixture was quenched with water, extracted with ethyl acetate (2
x 100 mL) and the organic layer was dried over anhydrous
Na2SO4, filtered and the solvent evaporated at reduced pressure.
The residue was purified by column chromatography using
petroleum ether as eluent to yield the pure product as a colourless
liquid (0,73 g, yield 74%).
Anal. Calcd. for C16H12N2O4 (296.28): C 64.86, H 4.08, N 9.46.
Found: C 65.01, H 4.21, N 9.86.
(1E,3E)-1-(4-N,N-Dimethylaminophenyl)-4-(4’-nitrophenyl)-1,3-
butadiene (2). A 50 mL round bottom flask was charged with
(E)-[4-(N,N-dimethylaminostyryl)trimethylsilane 2a (0.2 g, 0.90
mmol), (E)-trimethyl(4-nitrostyryl)silane 1b (0.2 g, 0.90 mmol),
PdCl2 (0.08 g, 0.45 mmol), CuCl2 (0.49 g, 3.66 mmol), and LiCl
(0.06 g, 1.36 mmol) in 20 mL of surfactant solution (15% wt
Triton X-100 in H2O) and the mixture was stirred at room
temperature. The reaction was monitored by TLC and GC-MS
until the disappearance of the starting reagents. The reaction
mixture was quenched with a saturated aqueous NaCl and then
extracted with ethyl acetate (3 x 50 mL). The organic layers were
combined and dried over anhydrous Na2SO4. After filtration the
solvent was evaporated under a reduced pressure and the residue
was purified by column chromatography using petroleum ether
and acetone 9:1 as eluent to give the pure product as a red solid
(0.17 g, 65%).
MS (EI, 70 eV) m/z (%) : 212 [M+], 197 (98), 181 (100), 115(53),
75 (12). FTIR (KBr): 2956, 1617, 1584, 1319, 1249, 1119, 983,
1
866, 838 cm-1. Η ΝΜR: δ= 6.90−6.96 (m, 2Η), 6.76 (d, J= 19.1
Hz, 1H), 6.71-6.66 (m, 1H), 6.51 (d,
J = 19.1 Hz,
1H), 0.17 (s, 9H) ppm. 13C NMR: δ =163.3 (dd, J= 247.6, 13.2
Hz), 141.9 (t, J= 9.0 Hz), 141.3 (t, J = 2.7 Hz), 133.1, 109.0 (dd, J
= 19.3, 5.7 Hz), 103.0 (t, J = 25.7 Ηz), 1.1 ppm. 19F NMR
(CF3Cl): δ= -(110.93-111.00) (m, 2F) ppm.
Anal. Calcd. for C11H14F2Si (212.31): C 62.23, H 6.65. Found: C
62.34, H 6.88.
FTIR (KBr): 2896, 2814, 1599, 1575, 1505, 1442, 1329, 1178,
1
1107, 987, 856, 804, 749 cm-1. H NMR: δ= 8.19-8.14 (m, 2H),
(1E,3E)-1-(4-Methoxyphenyl)-4-(4’-nitrophenyl)-1,3-butadiene
(1). A 50 ml round bottom flask was charged with (E)-(4-
methoxystyryl)trimethylsilane 1a (0.19 g, 0.91 mmol), (E)-(4-
nitrostyryl)trimethylsilane 1b (0.20 g, 0.91 mmol), PdCl2 (0.08 g,
0.45 mmol), CuCl2 (0.49 g, 3.65 mmol), and LiCl (0.06 g, 1.36
mmol) in 20 ml of surfactant solution (15% wt Triton X-100 in
H2O) and the mixture was stirred at room temperature. The
reaction was monitored by TLC and GC-MS until the
disappearance of the starting reagents. The reaction mixture was
quenched with a saturated aqueous NaCl and then extracted with
ethyl acetate (3 x 50 mL). The organic layers were combined and
dried over anhydrous Na2SO4. After filtration the solvent was
evaporated under a reduced pressure and the residue was purified
by column chromatography using petroleum ether and ethyl
acetate 9:1 as eluent to give the pure product 1 as an orange solid
(0.15 g, 60%).
7.53-7.48 (m, 2H), 7.35-7.44 (m, 2H), 7.14-7.03 (m, 1H), 6.56-
6.09 (m, 5H), 3.02 (s, 6H) ppm. 13C NMR: δ = 146.5, 144.1,
138.5, 137.4, 136.2, 134.0, 129.6, 129.4, 127.4, 126.7, 126.6,
124.2, 21.4 ppm. M.p.= 300°C (dec.) (Methanol).
Anal.Calcd. for C18H18N2O2 (294.35): C 73.45, H 6.16, N 9.52.
Found: C 73.71, H 6.48, N 9.80.
The
self-coupling
product
(E,E)-1,4-di(p-N,N-
dimethylaminophenyl)-1,3-butadiene (2’)17, was recovered as a
yellow solid (0.04 g, 13%).
MS (EI, 70 eV) m/z (%): 292 [M+] (100), 277 (10), 248 (18), 202
(36), 172 (52), 158 (66), 77 (4). FTIR (KBr): 2803, 1612, 15240,
992, 817 cm-1. 1H NMR: δ= 7.32 (d, J= 8.8 Hz, 4H), 6.77 (dd, J=
12.0, 2,5 Hz, 2H), 6.71 (d, J= 7,5 Hz, 4 H), 6.52 (dd, J= 11.9, 2.6
Hz, 2H), 2.97 (s, 12H); 13C NMR: δ = 133.7, 129.1, 128.9, 127.2,
114.3, 114.2, 41.5 ppm. M.p.= 245-246 °C (Methanol).

ACCEPTED MANUSCRIPT
0.02 g, (8%) of the self-coupling product (1E,3E)-1,4-di(4-
nitrophenyl)-1,3-butadiene (1’’) were recovered.
128.8, 128.4, 128.3, 126.8, 126.7, 124.2 ppm. M.p.= 137-139 °C
(Methanol). Anal. Calcd. for C16H13NO2 (251.28): C 76.48, H
5.21, N 5.57. Found: C 76.71, H 5.58, N 5.82.
(1E,3E)-1-(4-Nitrophenyl)-4-(4’-tolyl)-1,3-butadiene (4). A 50
mL round bottom flask was charged with (E)-trimethyl(4-
nitrostyryl)silane 1b (0.23 g, 1.05 mmol), (E)-trimethyl(4-
methylstyryl)silane 4a (0.20 g 1.05 mmol) PdCl2 (0.09 g, 0.52
mmol), CuCl2 (0.57 g, 4.2 mmol), and LiCl (0.07 g, 1.58 mmol)
in 20 mL of surfactant solution (15% wt Triton X-100 in H2O)
and the mixture was stirred at room temperature. The reaction
was monitored by TLC and GC-MS until the disappearance of
the starting reagents. The reaction mixture was quenched with a
saturated aqueous NaCl and then extracted with ethyl acetate (3 x
50 mL). The organic layers were combined and dried over
anhydrous Na2SO4. After filtration the solvent was evaporated
under a reduced pressure and the residue was purified by column
chromatography (petroleum ether/ethyl acetate 9:1 as eluent) to
give the pure product as a pale orange solid (0.16 g, 58%).
MS (EI, 70 eV) m/z (%): 265 [M+] (100), 250 (65), 218 (2), 204
(63), 202 (49), 191 (16), 128 (15). FTIR (KBr): 2918, 2849,
1587, 1512, 1344, 1109, 993, 862, 803, 746 cm-1.
The self-coupling product (1E,3E)-1,4-diphenyl-1,3-butadiene
(5’) was recovered as a white solid (0.021 g, 15%)6. MS (70eV)
m/z (%): 206 [M+](100), 205 (51), 203 (30), 202 (21), 191 (48),
190 (20), 128 (34), 91 (38). FTIR (KBr): 2918, 1490, 1412, 991,
1
738, 689, 491 cm-1. H NMR: δ= 7.48 (dd, J= 8.6, 1.4 Hz, 4H),
7.35-7.40 (m, 4H), 7.25-7.30 (m, 2H), 7.00 (dd, J= 11.9, 2.8 Hz,
2H), 6.71 (dd, J= 11.9, 2.8 Hz, 2H). 13C NMR: δ = 137.3, 132.8,
129.2, 128.6, 127.5, 126.4 ppm.
0.019 g (11%) of the self-coupling product (1E,3E)-1,4-di(4-
nitrophenyl)-1,3-butadiene (1’’) were recovered.
(1E,3E)-1-(4-Methoxyphenyl)-4-(3,5-difluorophenyl)-1,3-
butadiene (6). A 50 mL round bottom flask was charged with
(E)-(4-methoxystyryl)trimethylsilane 1a (0.20 g, 0.97 mmol),
(E)-(3,5-difluorostyryl)trimethylsilane 2b (0.21 g, 0.97 mmol),
PdCl2 (0.09 g, 0.49 mmol), CuCl2 (0.52 g, 3.88 mmol), and LiCl
(0.06 g, 1.45 mmol) in 20 mL of surfactant solution (15% wt
Triton X-100 in H2O) and the mixture was stirred at room
temperature. The reaction was monitored by TLC and GC-MS
until the disappearance of the starting reagents. The reaction
mixture was quenched with a saturated aqueous NaCl and then
extracted with ethyl acetate (3 x 50 mL). The organic layers were
combined and dried over anhydrous Na2SO4. After filtration the
solvent was evaporated under a reduced pressure and the residue
was purified by column chromatography using petroleum ether
and ethyl acetate 9:1 as eluent, to give the pure product as a white
solid (0.13 g, 50%).
1H NMR: δ = 8.18 (d, J=8.7 Hz, 2H), 7.53 (d, J=8.7 Hz, 2H),
7.36 (d, J=8.0 Hz, 2H), 7.16 (d, J= 8.0 Hz, 2H), 7.05-7.11 (m,
1H), 6.96-6.88 (m, 1H), 6.77 (d, J=15.4 Hz, 1H), 6.66 (d, J=15.4
Hz, 1H), 2.36 (s, 3H) ppm.
13C NMR: δ = 146.5, 144.1, 138.5, 136.2, 134.0, 129.6, 129.5,
128.6, 127.4, 126.7, 126.6, 124.2, 21.4 ppm. Mp: 172-174 °C
(Methanol). Anal. Calcd. for C17H15NO2 (265.31): C 76.96, H
5.70, N 5.28. Found: C 77.31, H 6.01, N 5.64.
The (1E,3E)-1,4-di(p-tolyl)-1,3-butadiene (4’)10 (0.04 g, 14%)
was recovered as a white solid. MS (70eV): 234 [M+], 229 (18),
219 (100), 218 (17), 204 (40), 203 (25), 202 (21), 105 (10) ppm.
MS (EI, 70 eV) m/z (%): 272 [M+] (100), 256 (37), 241 (50), 214
(26), 159 (26), 145 (29). FTIR (KBr): 2924, 2850, 1622, 1594,
1
1511, 1442, 1250, 1173, 1117, 1031, 984, 834 cm-1. H NMR:
1
FTIR (KBr): 2922, 2851, 1506, 1456, 985, 850, 798 cm-1. H
δ = 7.41 (m, 2H), 6.93 - 6.86 (m, 4H), 6.83 - 6.76 (m, 1H), 6.70 -
6.62 (m, 3H), 6.50 (d, J=15.35 Hz, 1H), 3.83 (s, 3H) ppm. 13C
NMR: δ = 163.3 (dd, J=13.19, 247.50 Hz), 159.1, 141.1 (t, J= 9.7
Hz), 134.5, 132.1, 129.2 (t, J=3.2 Hz), 127.9, 127.4, 126.2, 114.3,
108.7 (dd, J= 19.7, 5.8 Hz), 102.3 (t, J= 25.7 Hz), 55.3 ppm.
M.p.= 97-99 °C (Methanol). 19F NMR (CF3Cl):
δ= −(110.49−110.58) (m, 2F) ppm.
Anal. Calcd. for C17H14F2O (272.29): C 74.99, H 5.18. Found: C
75.31, H 5.28.
0.03 g (13 %) of the (1E,3E)-1,4-di(4-methoxyphenyl)-1,3-
butadiene (1’) were recovered.
NMR: δ = 7.29-7.39 (m, 4H), 7.10-7.20 (m, 4H), 6.85-6.98 (m,
2H), 6.56-6.69 (m, 2H), 2.35 (s, 6H) ppm. 13C NMR: δ = 137.2,
134.5, 132.1, 129.2, 128.3, 126.1, 21.3 ppm.
0.03 g (9%) of the self-coupling product product (1E,3E)-1,4-
di(4-nitrophenyl)-1,3-butadiene (1’’) were recovered.
(1E,3E)-1-(4-Nitrophenyl)-4-(phenyl)-1,3-butadiene (5). A 25
mL round bottom flask was charged with (E)-trimethyl(4-
nitrostyryl)silane
1b
(0.13
g,
0.57
mmol),
(E)-
trimethyl(styryl)silane 5a (0.10 g 0.57 mmol), PdCl2 (0.05 g, 0.28
mmol), CuCl2 (0.31 g, 2.28 mmol), and LiCl (0.04 g, 0.94 mmol)
in 15 mL of surfactant solution (15% wt Triton X-100 in H2O)
and the mixture was stirred at room temperature. The reaction
was monitored by TLC and GC-MS until the disappearance of
the starting reagents. The reaction mixture was quenched with a
saturated aqueous NaCl and then extracted with ethyl acetate (3 x
50 mL). The organic layers were combined and dried over
anhydrous Na2SO4. After filtration the solvent was evaporated
under a reduced pressure and the residue was purified by column
chromatography using petroleum ether and ethyl acetate 9.4:0.6
as eluent, to give the pure product as a yellow solid (0.08 g,
55%).
The homocoupling product (1E,3E)-bis(3,5-difluorophenyl)-1,3-
butadiene (6’’) was recovered as a white solid (0.02 g, 10%)
MS (EI, 70eV) m/z (%): 278 [M+], 257 (18), 256 (19), 165 (37),
151 (100), 127 (73), 119 (18). FTIR (KBr): 2924, 2848, 1622,
1
1586, 1443, 1260, 1115, 977, 864, 855 825 cm-1. H NMR: δ =
6.91-6.96 (m, 4H), 6.89 (dd, J= 11.9, 2.8 Hz, 2H), 6.70 (tt, J= 8.0,
2.3 Hz, 2H), 6.61 (dd, J= 11.9, 2.8 Hz, 2Hz) ppm. 13C NMR : δ =
163.1 (dd, J= 247.9, 13.1 Hz), 140.3 (t, J= 9.6 Hz), 132.2 (t,
J=3.1 Hz), 131.4, 109.0 (dd, J= 19.5, 5.9 Hz), 103.1 (t, J=.25.7
Hz) ppm. 19F NMR (CF3Cl): δ= −(110.97÷ −111.04) (m, 4F).
M.p.= 168-170°C (Methanol).
Anal.Calcd. for C16H10F4 (278.24): C 69.07, H 3.62. Found: C
69.34, H 3.95.
MS (EI, 70 eV) m/z (%): 251 [M+] (100), 205 (25), 202 (51), 189
(24), 178 (23), 165 (22), 129 (28), 115 (89). FTIR (KBr): 2920,
1
2850, 1587, 1512, 1341, 1108, 992, 857, 760, 743, 688 cm-1. H
(2E,4E)-5-(4-Methoxyphenyl)-1-phenylpenta-2,4-dien-1-one (7).
A 50 mL round bottom flask was charged with (E)-(4-
methoxystyryl)trimethylsilane 1a (0.17 g, 0.84 mmol), (E)-1-
phenyl-3-(trimethylsilyl)propen-1-one 3b (0.17 g, 0.84 mmol),
PdCl2 (0.07 g, 0.42 mmol), CuCl2 (0.45 g, 3.36 mmol), and LiCl
NMR: δ = 8.21-8.17 (m, 2H), 7.57-7.52 (m, 2H), 7.49-7.44 (m,
2H), 7.38-7.32 (m, 2H), 7.31-7.26 (m, 1H), 7.14-7.06 (m, 1H),
7.01-6.93 (m, 1H), 6.80 (d, J=15.4 Hz, 1H), 6.70 (d, J=15.4 Hz,
1H) ppm. 13C NMR: δ = 146.6, 143.9, 136.7, 136.1, 133.8, 130.1,

ACCEPTED MANUSCRIPT
R., Babudri, F., Farinola, G. M., Naso, F., Ragni, R., Eur. J. Org.
Chem. 2002, 4127.
(0.05 g, 1.18 mmol) in 25 mL of surfactant solution (15% wt
Triton X-100 in H2O) and the mixture was stirred at room
temperature. The reaction was monitored by TLC and GC-MS
until the disappearance of the starting reagents. The reaction
mixture was quenched with a saturated aqueous NaCl and then
extracted with ethyl acetate (3 x 50 mL). The organic layers were
combined and dried over anhydrous Na2SO4. After filtration the
solvent was evaporated under a reduced pressure and the residue
was purified by column chromatography using petroleum ether
and ethyl acetate 9:1 as eluent, to give the pure product as a
yellow solid (0.13 g, 60%).
9.
Babudri, F., Cicciomessere, A. R., Farinola, G. M., Fiandanese, V.,
Marchese, G. , Musio, R., Naso, F., Sciacovelli, O., J. Org. Chem.
1997, 62, 3291-3298.
10. Cicco, S. R., Farinola, G. M., Martinelli, C., Naso, F., Tiecco, M., Eur. J.
Org. Chem. 2010, 2275-2279.
11. For applications of polyenes in nonlinear optics, see the special issue:
Alain, V., Redoglia, S., Blanchard-Desce, M., Lebus, S., Lukaszuk, K.,
Wortmann, R., Gubler, U., Bosshard, C., Günter, P., Chem. Phys.
1999, 245, 51-71.
12. For mechanistic aspects, see: Weber, W. P., Felix, R. A., Willard, A.
K., Koenig, K. E., Tetrahedron Lett. 1971, 4701-4704.
13. Encyclopedia of Reagents for Organic Synthesis., Vol. 7, Paquette, L.
A. Ed., John Wiley & Sons Ltd, Chichester, 1995.
MS (EI, 70 eV) m/z (%): 264 [M+] (100), 233 (19), 159 (31), 144
(26), 115 (16). FTIR (KBr): 2919, 2850, 1672, 1598, 1511, 1251,
1175, 1033, 837, 816 cm-1. 1H NMR: δ = 7.98-7.95 (m, 2H),
7.63-7.58 (m, 1H), 7.58-7.50 (m, 2H), 7.50-7.42 (m, 5H), 7.07-
7.01 (m, 1H), 6.91-6.88 (m, 2H), 3.84 (s, 3H) ppm. 13C NMR:
δ = 160.6, 145.5, 141.9, 138.4, 132.5, 128.9, 128.8, 128.6, 128.5,
128.4, 124.9, 124.3, 114.4, 55.4 ppm. M.p.= 176-178°C
(Hexane).
14. McAtee, J. R., Martin, S. E. S., Ahneman, D. T., Johnson, K. A.,
Watsoneffrey, D. A., Angew. Chem., Int. Ed. Engl. 2012, 51, 3663–
3667.
15.
Saxena, A., Lam, H. W., Chem. Sci., 2011, 2, 2326-2331.
16. Kacprzynski, M. A. ,Kazane, S. A., May, T. L., Hoveyda, A. H., Org.
Lett. 2007, 9, 3187-3190.
17. Rodriguez, J. G., Tejedor, J. L., Rumbero A., Canoira L., Tetrahedron
2006, 62, 3075-3080.
Anal. Calcd. for C18H16O2 (264.32): C 81.79, H 6.10. Found: C
81.92, H 6.32.
0.03 g (13%) of the self-coupling product (1E,3E)-1,4-di(4-
methoxyphenyl)-1,3-butadiene (1’) were recovered.
The homo-coupling product (2E,4E)-1,6-diphenyl-2,4-butadiene-
1,6-dione (7’’) was recovered as a white solid (0.02 g, 10%) MS
(EI, 70eV) m/z (%): 262 [M+], 157 (73), 128 (31), 105 (71), 77
(100), 51 (47). FTIR (KBr): 2921, 2852, 1647, 1578, 1445, 1260,
1192, 1176, 1008, 764, 689, 651 cm-1. 1H NMR: δ = 7.98-8.00
(m, 4H), 7.56-7.63 (m, 4H), 7.49-7.54 (m, 4H), 7.38 (dd, J= 11.3,
3.0 Hz, 2H) ppm. 13C NMR: δ = 189.9, 141.1, 137.4, 133.3,
132.5, 128.8, 126.6 ppm. M.p.= 180-181°C (Methanol). Anal.
Calcd for C18H14O2 (262.30): C 82.42, H 5.38. Found: C 82.63, H
5.57.
Acknowledgments
This work was financially supported by Ministero dell’Istruzione,
dell’Universita` e della Ricerca (MIUR), ‘‘Progetto PRIN 2009
PRAM8L’’ and by Universita` degli Studi di Bari Aldo Moro
References and notes
1.
2.
3.
Metal Catalyzed Cross Coupling Reactions 2nd Edition.; A. de Meijere,
F. Diederich, Eds., Wiley- VCH : Weinheim, 2008.
Babudri, F., Farinola, G. M., Naso, F. J. Mater. Chem. 2004, 14, 11-
34.
Shi, W., Liu, C., Lei, A. Chem. Soc. Rev. 2011, 40, 2761-2766 and
references therein; Liu C., Zhang H., Shi W., Lei A. Chem. Rev. 2011,
111, 1780-1824.
4.
(a) Alberico, D., Scott, M. E., Lautens, M., Chem. Rev. 2007, 107, 174-
238; (b) Lipshutz, B. H., Siegmann, K., Garcia, E., Kayser, F., J. Am.
Chem. Soc. 1993, 115, 9276-9282; (c) Mizuno, H., Sakurai, H.,
Amaya, T., Hirao, T., Chem. Commun. 2006, 5042-5044 .
Hassan, J., Sevignon, M., Gozzi, C., Schulz, E., Lemarc, M., Chem.
Rev. 2002, 102, 1359-1470 .
Weber, M., Singh, F. V., Vieira, A. S., Stefani, H. A., Paixao, M. W.,
Tetrahedron Lett. 2009, 50, 4324-4327.
For some recent reviews, see: (a) Babudri, F., Farinola, G. M., Naso,
F., Ragni, R., Chem. Commun. 2007, 1003-1022; b) Farinola, G. M.,
Babudri, F., Cardone A., Omar, O. H., Naso, F., Pure Appl. Chem.
2008, 80, 1735-1746.
5.
6.
7.
8.
a) Farinola, G. M., Fiandanese, V., Mazzone, L., Naso, F., J. Chem.
Soc., Chem. Commun. 1995, 2523; b) Babudri, F., Farinola, G. M.,
Fiandanese, V., Mazzone, L., Naso, F., Tetrahedron. 1998, 54, 1085;
c) Babudri, F., Farinola, G. M., Naso, F., Panessa, D., J. Org. Chem.
2000, 66, 1554; d) Babudri, F., Farinola, G. M., Lopez, L. C.,
Martinelli, M. G., Naso, F., J. Org. Chem. 2001, 66, 3878; e) Ancora,

ACCEPTED MANUSCRIPT
•
•
•
one of the very first examples of oxidative cross-coupling between vinyl organometallic reagents
alkenyl silanes as useful synthetic intermediates to access extended polyenic systems
a suitable approach to the synthesis of unsymmetrically substituted push-pull butadienes,