Tetrahedron Letters
A highly stereoselective synthesis of new styryl-
organosilicon compounds
p
-conjugate
a
a
a
b,
Mariusz Majchrzak a, , Milena Hybsz , Sylwia Kostera , Maciej Kubicki , Bogdan Marciniec
⇑
⇑
a Faculty of Chemistry, Adam Mickiewicz University, Umultowska 89b, 61-614 Poznan, Poland
b Center of Advanced Technology, Adam Mickiewicz University, Grunwaldzka 6, 60-780 Poznan, Poland
a r t i c l e i n f o
a b s t r a c t
Article history:
This work describes very precise and controlled catalytic transformations as useful tools for the synthesis
of new trans- -conjugated molecular and macromolecular organosilicon compounds. Several distyryl-
arenes were obtained efficiently via silylative coupling in high yields and with excellent selectivity for
Received 1 December 2013
Revised 13 March 2014
Accepted 27 March 2014
Available online 5 April 2014
p
new E,E-bis(silyl)arenes.
Ó 2014 Published by Elsevier Ltd.
Keywords:
Catalysis
Silylative coupling
Suzuki–Miyaura coupling
p-Conjugated compounds
Organosilicon compounds
The search for new, highly selective methods to synthesize lin-
ear and branched organosilicon compounds has generated signifi-
cant interest. Both molecular and macromolecular compounds
containing silylene–arylene fragments are synthesized via Würtz
polycondensation (using Grignard reagents)1,2 or by reactions cat-
alysed by transition metals, for instance: Sonogashira,1c Suzuki3 or
Heck.4
We have described the synthesis of polymers and copolymers
containing arylene–silylene–vinylene and arylene–silylene–vinyl-
ene–phenylene–vinylene units with divinylbenzene, respectively,
with well-defined structures.8–11
In this Letter, we present a highly efficient, stereoselective
method for the preparation of new
p-conjugated distyryl-arylene
silicon derivatives through silylative coupling catalysed by a
Silylative coupling (SC) has been developed in our group over
the last two decades. It is the reaction of olefins with vinyl-substi-
tuted organosilicon compounds, taking place in the presence of
complexes containing initially, or generating in situ, metal–hydro-
gen [M–H] and metal–silicon [M–Si] bonds.5 The process occurs via
cleavage of the @CASi bond in the vinylsilane and the CAH bond in
the olefin, and is catalysed by transition metal complexes [TM–H]
or silyl [TM–Si] ligands (silicometallics) (where TM = Ru, Rh, Ir,
Co).6,7
Silylative coupling appears to be a unique, effective and highly
regio- and stereoselective method for the functionalization of
molecular and macromolecular compounds that have one or a
few vinyl groups connected to the silicon atom. Without any doubt,
this reaction is a powerful and convenient tool for the synthesis of
well-defined ruthenium(II) complex.
The starting dienes were prepared in a highly efficient Suzuki–
Miyaura coupling reaction catalysed by the very active palladium
complex [Pd(g
2-dba)(PCy3)2] 1, as shown in Scheme 1.
Typically, the crude mixture was extracted with CH2Cl2/water
and a small amount of sodium chloride to disperse the slurry.
The mixture was then left over sodium sulfate for six hours.12 In
the next step, we used the obtained olefin for the silylative cou-
pling reaction. The catalytic process between distyrylarene and
trimethylvinylsilane was conducted following the original proce-
dure: [RuH(CO)Cl(PCy3)2]13 (catalyst 2), toluene, sealed ampoule,
argon atmosphere.
In order to optimize the reaction conditions with respect to
activity, selectivity, catalyst loading, time and temperature, the
model reaction between 4,4-divinyl-p-biphenyl and vinyltrimeth-
ylsilane (after redistillation) at different molar ratios (from 1:2 to
1:5), was studied (Scheme 2).14
unsaturated, highly p-conjugated compounds.
Since the reactive substrate contains a styryl group, the reaction
conditions were optimized to eliminate possible uncontrolled,
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Corresponding authors. Tel.: +48 61 8291407; fax: +48 61 8291508.
0040-4039/Ó 2014 Published by Elsevier Ltd.