Synthesis and application of chiral dienes and chiral imidates as ligands for transition metal catalysis

In this dissertation, two main ligandclasses have been studied: chiral diene ligands and chiral imidate ligands. We developed a novel route to synthesize chiral disubstituted bicyclo[2.2.1]heptadienes (R= i-Bu, c-Hex, Benzyl and allyl) starting from enantiomerically pure bistriflate. The synthesized diene ligands were tested in the rhodium(I)-catalyzed 1,4-addition of phenylboronic acids to cyclic enones (up to 96% ee) and α-acetamido acrylic ester and in the rhodium(I)-catalyzed 1,2-addition of phenylboronic acids to benzaldehydes (up to 48% ee). We introduced chiral imidates as a novel nitrogen-based ligand family. These imidates, with an exocyclic nitrogen, have never before been reported in literature. We showed that these imidate ligands could be obtained readily via a one-step synthesis starting from a central precursor in excellent yields. Moreover, imidate ligands could further be fine-tuned when substituents were put on the aromatic ring of the imidate ligand precursor. The synthesized monodentate and bidentate ligands were tested in several asymmetric test reactions. In the copper(I)-catalyzed asymmetric aziridinations, we obtained usually high yields (up to 90% yield) and moderate enantioselectivity (51% ee) with a bidentate imidate ligand. The asymmetric addition of diethylzinc to benzaldehyde resulted in high yields (up to 87% yield) and good enantioselectivities (up to 76% ee). However, the best result was obtained in the asymmetric allylic alkylation with an imidate with a binaphtylbackbone: a moderate yield (53% yield) with an excellent selectivity (95% ee). Futhermore, we developed successfully hybrid imidate-phosphane ligands as a new type of P,N ligands. These ligands are easily accessible in one step via a condensation of a commercially available aminophosphane and an imidate ligand precursor. The ligands were demonstrated to be highly valuable in palladium-catalyzed allylic substitution reactions. Excellent performance of this catalyst system was observed in the allylic alkylation of 1,3-diphenyl-2-propenyl acetate with various nucleophiles (up to 99% yield and >99% ee). Moreover, the allylic alkylation of linear unhindered and cyclic substrates resulted in good conversions and enantioselectivities. The cyclic imidate ligand precursor could also be used efficiently as a synthetic intermediate for the synthesis of chiral oxazoline alcohol ligands and the synthesis of chiral imidazolidines.

Grantor dc:publisher

Ghent University. Faculty of Sciences

Year dc:date

2009

Author dc:creator

• Noël, Timothy

Contributors dc:contributor

• Van der Eycken, Johan

• Chemistry
• P_N ligands
• diene ligands
• Imidate ligands
• Asymmetric catalysis
• Ligand Design

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

eng

Identifier

https://biblio.ugent.be/publication/811200
https://biblio.ugent.be/publication/811200/file/4335096

OAI identifier oai:identifier

oai:archive.ugent.be:811200