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Stereoselective and stereospecific reactions of cobalt sandwich complexes: Synthesis of a new class of single enantiomer bulky planar chiral P-N and P-P ligands

Stereoselective and stereospecific reactions of cobalt sandwich complexes: Synthesis of a new class of single enantiomer bulky planar chiral P-N and P-P ligands
Stereoselective and stereospecific reactions of cobalt sandwich complexes: Synthesis of a new class of single enantiomer bulky planar chiral P-N and P-P ligands
Starting from (η 5 -acetylcyclopentadienyl)(η 4 -tetraphenylcyclobutadiene)cobalt(I), highly enantioselective (99% ee) (S)-CBS catalysed ketone reduction followed by stereospecific alcohol-azide exchange, azide reduction and dimethyllation gave (R)-(η 5 -α-N,N-dimethylaminoethylcyclopentadienyl)(η 4 -tetraphenylcyclobutadiene) cobalt(I) (Arthurs' amine). This underwent highly diastereoselective cyclopalladation to give di-μ-acetate-bis-(R)-[(η 5 -(S p )-2-(α-N,N-dimethylaminoethyl)cyclopentadienyl, 1-C, N)(η 4 -tetraphenylcyclobutadiene)cobalt(I)]dipalladium, and highly diastereoselective lithiation to give (R)-(η 5 -(S p )-1-(α-N,N-dimethylaminoethyl)-2-(diphenylphosphino)cyclopentadienyl)(η 4 -tetraphenylcyclobutadiene)cobalt(I) (PPCA) following the addition as electrophile of chlorodiphenylphosphine. This PN-ligand was converted into (R)-(η 5 -(S p )-1-(α-dicyclohexylphosphinoethyl)-2-(diphenylphosphino)cyclopentadienyl)(η 4 -tetraphenylcyclobutadiene)cobalt(I), a PP-ligand (Rossiphos), by stereospecific amine-phosphine exchange using HPCy 2 . These air-stable P-N and P-P complexes are the first examples of a new class of bulky planar chiral ligands for application in asymmetric catalysis.
Cobalt, Diastereoselectivity, Enantioselectivity, Ligands, Sandwich complexes
0947-6539
4310-4319
Arthurs, Ross A.
d88e1b07-6886-422f-810c-aa293043854d
Horton, Peter N.
154c8930-bfc3-495b-ad4a-8a278d5da3a5
Coles, Simon J.
3116f58b-c30c-48cf-bdd5-397d1c1fecf8
Richards, Christopher J.
bf1ec9f1-3545-450b-b64c-2984e311dfb6
Arthurs, Ross A.
d88e1b07-6886-422f-810c-aa293043854d
Horton, Peter N.
154c8930-bfc3-495b-ad4a-8a278d5da3a5
Coles, Simon J.
3116f58b-c30c-48cf-bdd5-397d1c1fecf8
Richards, Christopher J.
bf1ec9f1-3545-450b-b64c-2984e311dfb6

Arthurs, Ross A., Horton, Peter N., Coles, Simon J. and Richards, Christopher J. (2018) Stereoselective and stereospecific reactions of cobalt sandwich complexes: Synthesis of a new class of single enantiomer bulky planar chiral P-N and P-P ligands. Chemistry - A European Journal, 24 (17), 4310-4319. (doi:10.1002/chem.201705113).

Record type: Article

Abstract

Starting from (η 5 -acetylcyclopentadienyl)(η 4 -tetraphenylcyclobutadiene)cobalt(I), highly enantioselective (99% ee) (S)-CBS catalysed ketone reduction followed by stereospecific alcohol-azide exchange, azide reduction and dimethyllation gave (R)-(η 5 -α-N,N-dimethylaminoethylcyclopentadienyl)(η 4 -tetraphenylcyclobutadiene) cobalt(I) (Arthurs' amine). This underwent highly diastereoselective cyclopalladation to give di-μ-acetate-bis-(R)-[(η 5 -(S p )-2-(α-N,N-dimethylaminoethyl)cyclopentadienyl, 1-C, N)(η 4 -tetraphenylcyclobutadiene)cobalt(I)]dipalladium, and highly diastereoselective lithiation to give (R)-(η 5 -(S p )-1-(α-N,N-dimethylaminoethyl)-2-(diphenylphosphino)cyclopentadienyl)(η 4 -tetraphenylcyclobutadiene)cobalt(I) (PPCA) following the addition as electrophile of chlorodiphenylphosphine. This PN-ligand was converted into (R)-(η 5 -(S p )-1-(α-dicyclohexylphosphinoethyl)-2-(diphenylphosphino)cyclopentadienyl)(η 4 -tetraphenylcyclobutadiene)cobalt(I), a PP-ligand (Rossiphos), by stereospecific amine-phosphine exchange using HPCy 2 . These air-stable P-N and P-P complexes are the first examples of a new class of bulky planar chiral ligands for application in asymmetric catalysis.

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More information

Accepted/In Press date: 1 January 2018
e-pub ahead of print date: 1 February 2018
Published date: 25 March 2018
Keywords: Cobalt, Diastereoselectivity, Enantioselectivity, Ligands, Sandwich complexes

Identifiers

Local EPrints ID: 420414
URI: https://eprints.soton.ac.uk/id/eprint/420414
ISSN: 0947-6539
PURE UUID: c3a5d05d-6ce4-418f-bf0a-9105c2a37754
ORCID for Peter N. Horton: ORCID iD orcid.org/0000-0001-8886-2016
ORCID for Simon J. Coles: ORCID iD orcid.org/0000-0001-8414-9272

Catalogue record

Date deposited: 04 May 2018 16:31
Last modified: 06 Jun 2018 12:54

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Contributors

Author: Ross A. Arthurs
Author: Peter N. Horton ORCID iD
Author: Simon J. Coles ORCID iD
Author: Christopher J. Richards

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