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. (2015) Chirality Control in Planar Chiral Cobalt Oxazoline Palladacycles. Organometallics, 34 (12). pp. 2953-2961. ISSN 0276-7333

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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: 22 Jul 2020 00:40
DOI: 10.1021/acs.organomet.5b00282

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