Screening of Ligands in the Asymmetric Metallocenethiolatocopper(I)-Catalyzed Allylic Substitution with Grignard Reagents
2006 (English)In: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 62, no 24, 5632-5640 p.Article in journal (Refereed) Published
Screening of metallocenethiolate ligands for copper(I)-catalyzed substitution of allylic acetates with Grignard reagents has been carried out. The previously used ligand, lithium (R,Sp)-2-(1-dimethylaminoethyl)ferrocenylthiolate (4a), possessing both central and planar chirality, was the starting point for the screening. It was found that the diastereomeric ligand lithium (R,Rp)-2-(1-dimethylaminoethyl)ferrocenylthiolate (4b) exhibiting reversed planar chirality gave increased enantioselectivity in the allylic substitution, at least when cinnamyl acetate was used as a substrate. The ruthenocene-based ligand lithium (R,Sp)-2-(1-dimethylaminoethyl)ruthenocenylthiolate (4c) gave an enhanced reaction rate, but lower chiral induction. The use of disulfide bis[(R,Sp)-2-(1-dimethylaminoethyl)ferrocenyl]disulfide (7a) as a ligand precursor worked well but resulted in lower enantioselectivity.
Place, publisher, year, edition, pages
Elsevier Ltd , 2006. Vol. 62, no 24, 5632-5640 p.
Asymmetric induction; Copper catalysis; Allylic substitution; Cross-coupling; Ferrocene ligands
IdentifiersURN: urn:nbn:se:su:diva-22681DOI: 10.1016/j.tet.2006.03.100OAI: oai:DiVA.org:su-22681DiVA: diva2:189259
Part of urn:nbn:se:su:diva-10312006-05-082006-05-082011-01-14Bibliographically approved