Eintrag in der Universitätsbibliographie der TU Chemnitz
Volltext zugänglich unter
URN: urn:nbn:de:bsz:ch1-qucosa2-969100
Gorai, Mahadeb
Teichert, Johannes F. ; Breder, Alexander (Gutachter)
Bifunctional ligands for copper-catalyzed hydrogenations – from asymmetric catalysis to proximity effects
Kurzfassung in englisch
This thesis discusses the development of chiral N-heterocyclic carbene (NHC)-guanidine bifunctional complexes for asymmetric hydrogenation of carbonyl compounds using dihydrogen (H2) as the terminal reducing reagent. Furthermore, the 2-iminopyridine-based copper(I)/NHC bifunctional complexes was developed as a major part of this work, which enabled copper(I)-catalyzed hydrogenation chemistry to be performed for the first time under low H2 pressure (1–2 bar), reaching balloon pressure. The first section of the thesis focuses on the synthetic development of several chiral NHC-guanidine ligand precursors, where chirality is embedded either in the linker unit or in the guanidine moiety. These ligand precursors facilitated the copper(I)-catalyzed asymmetric 1,2-reduction of ketones, with stereoinformation transfer from the ligand precursors to the substrate via H-bonding. The final section of the thesis discusses the development of 2-iminopyridine-based copper(I)/NHC bifunctional complexes. The presence of the basic 2-iminopyridine subunit allowed, for the first time, the copper(I)-catalyzed semihydrogenation of alkynes, 1,4-reduction of enolates/enamides, and 1,2-reduction of aldehydes/ketones under very low H2 pressure (1–2 bar), reaching balloon pressure. An unprecedented substrate scope in copper(I)-catalyzed hydrogenations was achieved using the 2-iminopyridine-based copper(I)/NHC bifunctional complex. Additionally, late-stage functionalization and deuterium labeling of several drug molecules were performed under mild reaction conditions. Mechanistic studies indicate that the bifunctional catalyst operates via an iminopyridine-mediated proximity effect, resulting in the coordination of an alcohol as a proton source on the copper(I) complex, thereby facilitating the overall reactions through a rapid protodecupration step.
| Universität: | Technische Universität Chemnitz | |
| Institut: | Professur Organische Chemie | |
| Fakultät: | Fakultät für Naturwissenschaften | |
| Dokumentart: | Dissertation | |
| Betreuer: | Teichert, Johannes F. | |
| DOI: | doi:10.60687/2025-0076 | |
| SWD-Schlagwörter: | Ligand , Katalytische Hydrierung , Katalyse , Proximity-Effekt | |
| Freie Schlagwörter (Englisch): | NHC , guanidine , bifunctional complex , asymmetric , H-bonding , 2-iminopyridine , proximity effect , copper , hydrogenation | |
| DDC-Sachgruppe: | Naturwissenschaften und Mathematik, Chemie | |
| Sprache: | englisch | |
| Tag der mündlichen Prüfung | 29.04.2025 | |
| OA-Lizenz | CC BY 4.0 |
