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OH
O
H
OR
O
R
O
O
OH
O
n
O
OR
HO
RO
O
Pd(OAc)
2
0.4 mol%
TPPTS
H
2
O/NaOH
O
OH
HO
OH
OR
RO
OR
OH
sucrose
OR
R= Hor
or
Scheme 11 Telomerization of butadiene with sucrose in basic aqueous medium.
OH
OH
OH
O
O
O
O
OH
O
O
O
O
O
O
[Pd]
O
HO
HO
HO
OH
OH
HO
OH
n
n
i
PrOH/NaOH 0.1 N
Scheme 12 Telomerization of butadiene with starch.
control of the butadiene to sucrose ratio have allowed to tune the average
substitution degree from 1.2 to 3.
27
It has also to be noticed that along
with the classical OC8 substitution corresponding to the two butadiene
units coupling, the presence of odd values of butadiene units could be
detected by FAB spectroscopy, indicating that the mixture also contained
OC4 moieties.
This reaction was also further studied by Pinel.
30
The catalytic system
was based on Pd(OAc)
2
/TPPTS in a mixture NaOH/iPrOH as solvent. The
degree of substitution on sucrose has been evaluated from a combination
of analytical techniques as NMR and LSIMS (Liquid Secondary Impact
Mass Spectrometry) as well as chromatographic and gravimetric
measurements. Degrees of substitution ranging from 1 to 6 are obtained
depending upon experimental conditions, especially the temperature, the
butadiene/sucrose ratio and the nature of the catalyst.
In 2002, the same authors applied this methodology to starch in order
to modify the hydrophilic properties of native starch for its incorporation
in polymers (Scheme 12).
31,32
This reaction could be successfully achieved with low to moderate
degrees of substitutions (DS
=
0.04-0.52) depending on experimental
conditions. For example, using 0.3 mol% of the water soluble palladium
catalyst (Pd/TPPTS), the reaction occurred in iPrOH/NaOH 0.1 N solvent
mixture, even at 50 1C and after 3 h reaction, the DS reached 0.08.
Unfortunately, these conditions did not preserve the granular aspect of
starch, which is a key factor for an industrial aqueous process. After
optimization, a system based on [(p-allyl)Pd(TPPTS)
2
Cl]/Na
2
SO
4
in
dimethylisosorbide as cosolvent allowed to obtain high conversions of
butadiene (93%) without degradation of the starch texture.
In order to avoid the use of an organic co-solvent with aqueous
mixtures, telomerization of butadiene with starch has been performed in
pure water in the presence of surfactants.
33-35
The best activity was
achieved using cetyltrimethylammonium bromide (CTAB) as a cationic
surfactant. Using the system [(p-allyl)Pd(TPPMS)
2
]/CTAB/Na
2
SO
4
/CTAB
(TPPMS
=
(m-sulfonatophenyl)-diphenylphosphine monosodium salt) in
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