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Lanthanum-pyBOX complexes as catalysts for the enantioselective conjugate addition of malonate esters to β,γ-unsaturated α-ketimino esters

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Lanthanum-pyBOX complexes as catalysts for the enantioselective conjugate addition of malonate esters to β,γ-unsaturated α-ketimino esters

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dc.contributor.author	Espinosa López, Miguel
dc.contributor.author	Blay Llinares, Gonzalo
dc.contributor.author	Cardona Prósper, María Luz
dc.contributor.author	Fernández Picot, Isabel
dc.contributor.author	Muñoz, M. Carmen
dc.contributor.author	Pedro, José Ramón
dc.date.accessioned	2020-09-29T14:18:53Z
dc.date.available	2020-09-29T14:18:53Z
dc.date.issued	2018
dc.identifier.citation	Espinosa López, Miguel Blay Llinares, Gonzalo Cardona Prósper, María Luz Fernández Picot, Isabel Muñoz, M. Carmen Pedro, José Ramón 2018 Lanthanum-pyBOX complexes as catalysts for the enantioselective conjugate addition of malonate esters to β,γ-unsaturated α-ketimino esters Journal of Coordination Chemistry 71 6 864 873
dc.identifier.uri	https://hdl.handle.net/10550/75684
dc.description.abstract	In this paper, we report the application of chiral complexes of La(III) with pyBOX ligands as Lewis acid catalysts in the conjugate addition of malonic esters to N-tosyl imines derived from β,γ-unsaturated α-keto esters to give the corresponding chiral α,β-dehydroamino esters. pyBOX complexes with La(III), Yb(III), Sc(III), and In(III) triflates were assessed in this reaction but only La(III) showed good activity and enantioselectivity, while Yb(III) provided the expected product with low yield and stereoselectivity, and the Sc(III) and In(III) complexes were completely inactive. The complex of La(OTf )3 with the diphenylpyBOX ligand prepared in situ provided the best results and allowed obtaining chiral α,β-dehydroamino esters 3 with excellent yields, E:Z diastereomeric ratios (29:71-99:1) and high enantiomeric excesses (20-95%). The reaction could be applied to imines having a substituted aromatic ring or a heterocycle attached to the double bond, although the presence of electron-withdrawing groups on the aromatic ring was detrimental for stereoselectivity. The reaction products were obtained with the S configuration at the stereogenic center and the Z configuration at the enamine double bond as determined by NOESY experiments and X-ray analysis. Based on the experimental results a stereochemical model involving a nine- coordinate La(III) species has been proposed.
dc.language.iso	eng
dc.relation.ispartof	Journal of Coordination Chemistry, 2018, vol. 71, num. 6, p. 864-873
dc.subject	Química orgànica
dc.subject	Catàlisi
dc.title	Lanthanum-pyBOX complexes as catalysts for the enantioselective conjugate addition of malonate esters to β,γ-unsaturated α-ketimino esters
dc.type	journal article	es_ES
dc.date.updated	2020-09-29T14:18:53Z
dc.identifier.doi	10.1080/00958972.2018.1437422
dc.identifier.idgrec	126269
dc.rights.accessRights	open access	es_ES