The design, synthesis and application to assymetric catalysis of chiral transition metal cyclopentadienyl complexes
The design, synthesis and application to assymetric catalysis of chiral transition metal cyclopentadienyl complexes
The synthesis of the known chiral zirconocene (-)-(η5-cyclopentadienyl) (η5-{1-[(1S, 2S, 4R)-2-isopropyl-5-methylcyclohexyl]- 4, 5, 6, 7 tetrahydroindenly} zirconium dichloride (135) and titanocene (-)-(η5-cyclopentadienyl) (η5-{1-[(1S, 2S, 5R)-2-isopropyl-5-methylcyclohexyl]-4,5,6, 7 tetrahydroindenyl}) titanium dichloride (151) has been repeated and the yields optimised. Application of the zirconocene (135) to chiral ethylmagnesiation has been extended with enantioselectivities of up to 89% observed. The effect of solvent and substrate on the enantioselectivity of the ethylmagnesiation reaction has been investigated.
Application of titanocene (151) to hydrogenation reactions have been investigated. The asymmetric reduction of terminal enamines has been achieved with moderate yield (55%) and enantioselectivity (50% e.e.). Hydrogenation of 2-phenyl-1-butene gave 19% enantiomeric excess. The hydrogenation of imines and hydrosilylation of ketones gave racemic products.
Novel chiral indenyl ligands containing pendant ether functionality have been synthesised from (R)-(+)-styrene oxide and indenyllithium. The chiral ligands have been applied to the synthesis of six chiral zirconocenes including; (+)(2R)-[η5-cyclopentadienyl)-2-{η5-3-(4,5,6,7-tetrahydroindenyl)-2-phenylethyl-1-methoxy}] zirconium dichloride (181) and (+)(2R)-[(η5-3-(4,5,6,7-tetrahydroindenyl)-2-phenylethyl}] zirconium dichloride (189). X-ray structures have been obtained of zirconocenes (rac)-(181) and (rac)-(189). Application of the chiral zirconocenes to chiral ethylmagnesiation and carboalumination reaction gave enantioselectivity of up to 71% e.e.
University of Southampton
Brookings, Daniel Christopher
1999
Brookings, Daniel Christopher
Brookings, Daniel Christopher
(1999)
The design, synthesis and application to assymetric catalysis of chiral transition metal cyclopentadienyl complexes.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
The synthesis of the known chiral zirconocene (-)-(η5-cyclopentadienyl) (η5-{1-[(1S, 2S, 4R)-2-isopropyl-5-methylcyclohexyl]- 4, 5, 6, 7 tetrahydroindenly} zirconium dichloride (135) and titanocene (-)-(η5-cyclopentadienyl) (η5-{1-[(1S, 2S, 5R)-2-isopropyl-5-methylcyclohexyl]-4,5,6, 7 tetrahydroindenyl}) titanium dichloride (151) has been repeated and the yields optimised. Application of the zirconocene (135) to chiral ethylmagnesiation has been extended with enantioselectivities of up to 89% observed. The effect of solvent and substrate on the enantioselectivity of the ethylmagnesiation reaction has been investigated.
Application of titanocene (151) to hydrogenation reactions have been investigated. The asymmetric reduction of terminal enamines has been achieved with moderate yield (55%) and enantioselectivity (50% e.e.). Hydrogenation of 2-phenyl-1-butene gave 19% enantiomeric excess. The hydrogenation of imines and hydrosilylation of ketones gave racemic products.
Novel chiral indenyl ligands containing pendant ether functionality have been synthesised from (R)-(+)-styrene oxide and indenyllithium. The chiral ligands have been applied to the synthesis of six chiral zirconocenes including; (+)(2R)-[η5-cyclopentadienyl)-2-{η5-3-(4,5,6,7-tetrahydroindenyl)-2-phenylethyl-1-methoxy}] zirconium dichloride (181) and (+)(2R)-[(η5-3-(4,5,6,7-tetrahydroindenyl)-2-phenylethyl}] zirconium dichloride (189). X-ray structures have been obtained of zirconocenes (rac)-(181) and (rac)-(189). Application of the chiral zirconocenes to chiral ethylmagnesiation and carboalumination reaction gave enantioselectivity of up to 71% e.e.
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Published date: 1999
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Local EPrints ID: 463564
URI: http://eprints.soton.ac.uk/id/eprint/463564
PURE UUID: b70ad3d7-74e7-4219-b944-41d22ee7c735
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Date deposited: 04 Jul 2022 20:53
Last modified: 04 Jul 2022 20:53
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Author:
Daniel Christopher Brookings
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