Soluble polymer supports facilitate the recovery and recycling of expensive
transition metal complexes. Recently, polyisobutylene (PIB) oligomers have been found
to be suitable polymer supports for the recovery of a variety of transition metal catalysts
using liquid/liquid biphasic separations after a homogeneous reaction. Our work has
shown that PIB-supported Ni(II) and Co(II) β-diketonates prepared from commercially
available vinyl terminated PIB oligomers possess catalytic activity like that of their low
molecular weight analogs in Mukaiyama epoxidation of olefins.
Carboxylic acid terminated PIB derivatives can act as carboxylate ligands for
Rh(II) cyclopropanation catalysts. An achiral PIB-supported Rh(II) carboxylate catalyst
showed good activity in cyclopropanation of styrene in hydrocarbon solvents, and could
be easily recycled nine times by a post reaction extraction. Further application of PIB
supports in asymmetric cyclopropanation reactions were investigated using PIBsupported
arenesulfonyl Rh(II) prolinates derived from L-proline as examples. The PIBsupported
chiral Rh carboxylates demonstrated moderate activity and were recovered and reused for four to five cycles. The prolinate catalyst prepared from PIB-anisole also
showed encouraging enantioselectivity and about 8% ee and 13% ee were observed on
trans- and cis-cyclopropanation product respectively.
Finally, PIB oligomers can be modified in a multi step sequence to prepare PIBsupported
chiral bisoxazolines that can in turn be used to prepare active, recyclable PIBsupported
Cu(I) bisoxazoline complexes for olefin cyclopropanation. These chiral
copper catalysts showed moderate catalytic activity and good stereoselectivity in
cyclopropanation of styrene. A chiral ligand prepared from D-phenylglycinol provided
the most effective stereo control and gave the trans- and cis-cyclopropanation product in
94% ee and 68% ee respectively. All three PIB-supported chiral bisoxazoline-Cu(I)
catalysts could be reused five to six times.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-3129 |
| Date | 15 May 2009 |
| Creators | Tian, Jianhua |
| Contributors | Bergbreiter, David E. |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | electronic, application/pdf, born digital |
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