Chirality Control in Planar Chiral Cobalt Oxazoline Palladacycles

Cassar, Doyle J., Roghzai, Hemin, Villemin, Didier, Horton, Peter N., Coles, Simon J. and Richards, Christopher J. ORCID: https://orcid.org/0000-0001-7899-4082 (2015) Chirality Control in Planar Chiral Cobalt Oxazoline Palladacycles. Organometallics, 34 (12). pp. 2953-2961. ISSN 0276-7333

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Abstract

Palladation of (eta(5)-(S)-2-(4-R-substituted)-oxazolinylcyclopentadienyl)(eta(4)-tetraphenylcyclobutadiene)cobalt-(I) with Pd(OAc)(2) (R = Me, CH2Cy, CH(2)i-Pr, CH2Ph) resulted exclusively in formation of the (S,Sp)-palladacycle with R = CH2Cy (acetic acid solvent) and up to 13:1 selectivity in favor of the (S,Sp)-palladacycle with R = CH(2)i-Pr (CH2Cl2 solvent). In the latter case diastereomeric purity was achieved by recrystallization, and the absolute configuration of the new element of planar chirality was established by X-ray crystallography. These outcomes contrast with the opposite sense of diastereoselectivity observed for the corresponding R = i-Pr-substituted oxazoline, which results in the palladacycle (S,R-p)-COP-OAc (acetic acid solvent), these palladation reactions being under either kinetic (S,S-p) or thermodynamic (S,Rp) control. Following conversion to the chloride-bridged (S,S-p)-palladacycle dimer (R = CH2Cy), this was employed as a catalyst for the rearrangement of allylic trichloroacetimidates (0.25 mol % catalyst loading, up to 80% ee).

Item Type: Article
Uncontrolled Keywords: catalytic asymmetric-synthesis,diastereoselective ortho-lithiation,aza-claisen rearrangement,allylic esters,direct arylation,derivatives,ligands,palladation,mechanism,heterocycles
Faculty \ School: Faculty of Science > School of Chemistry
Depositing User: Pure Connector
Date Deposited: 11 Feb 2016 16:00
Last Modified: 24 Sep 2022 00:40
URI: https://ueaeprints.uea.ac.uk/id/eprint/57054
DOI: 10.1021/acs.organomet.5b00282

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