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iso (i)
iso (i)
l/i low
Nu
Nu
l/i high
Nu
Nu
linear (l)
linear (l)
R
3
P
Pd
+
Nu
Nu
-
Pd
Pd
Pd
R
3
P
R
3
P
R
3
P
PR
3
NuH
+
PR
3
Nu
-
Pd
R
3
P
- [Pd(PR
3
)]
+
NuH
Scheme 7 General mechanism of the palladium catalyzed telomerization reaction of a
nucleophile NuH with butadiene.
O
O
HO
O
O
O
O
[Pd]
0.4 mol%
O
O
O
O
O
Scheme 8 Telomerization of butadiene with a protected galactopyranose.
OH
O
H
OH
O
O
OH
O
OH
HO
O
OH
HO
OH
HO
OH
OH
OH
Saccharose
(sucrose)
β
-D-glucopyranose
(glucose)
OH
O
O
OH
O
H
OH
β
-D-methylglucoside
HO
sorbitol
HO
OH
OH
OH
OH
Scheme 9 Carbohydrates used by Gruber et al. as telogens in the telomerization reaction.
prepared by the reaction of butadiene with glucose and sucrose in
presence of an in situ formed palladium catalyst from Pd(acac)
2
and PPh
3
in isopropanol (Scheme 9). The unreacted solid carbohydrate was simply
filtered from the reaction mixture. The five hydroxyl groups of the glucose
and the eight hydroxyl groups of sucrose could be etherified by linear and
branched 1- and 3-octadienyl chains respectively. A mixture of the ethers
was then obtained with various substitution degrees.
In 1993, by using similar reaction conditions, the same authors re-
ported on the telomerization of butadiene with glycerol, aliphatic diols
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