Chemistry Reference
In-Depth Information
usedwas to first entrap themetal catalysts by coacervationwith linear polystyrene that was functionalized
both by epoxide groups and oligo poly(ethylene glycol). The polymer becomes cross-linked upon heating
through reaction of the epoxide groups with polyethylene glycol entrapping the metal:
THF
Pd(PPh
3
)
4
O
O
+
H
4
+
120
o
C
6
90
4
O
O
The above solid catalysts were used successfully to catalyze various reactions, like the
Suzuki-Miyura reaction [
15
], such as aminocarbonylation, amidation, and the Heck reactions [
16
].
Polymers containing scandium triflate, ruthenium, platinum, or gold were prepared to perform
Mukayama aldol, alcohol, and sulfide oxidation, hydrogenation, and indole syntheses [
17
].
Incorporation of some of the metals, like palladium, is improved by incorporating phosphine
ligands into the polymer. One such ligand can be illustrated as follows [
19
]:
P
Hoveyda, Schrock, and coworkers [
19
] reported using chiral cross-linking compounds
immobilized on heterogeneous polystyrene resins. The chiral moiety was then used as a ligand in
asymmetric catalyses. In one application, they used the material to prepare a recyclable chiral
molybdenum olefin metathesis catalyst that was used in enantioselective ring opening and ring-
closing metathesis reactions. The material can be illustrated as follows:
O
O
O
O
