The title compounds were generated by deprotonation of different benzyl-type carbamates with sec-butyllithium in the presence of chiral diamines (-)-sparteine or diisopropyl and di-tert-butyl bis(oxazoline)s. These lithiated species exhibit configurational lability at -78 8C. In the case of the chiral di-tert-butyl bis(oxazoline), the equilibrium of the epimeric complexes can be used synthetically to obtain highly enantioenriched secondary benzyl carbamates. The enantiodetermining step was proven to be a dynamic thermodynamic resolution. The absolute configurations of the products were determined, and the stereochemical pathways of selected substitution reactions were thus elucidated. High level quantum chemical investigations were performed to gain insight into the experimentally investigated system. To obtain an accuracy for the energy difference (DDH) between two epimeric complexes of about 0.5 kcalmol-1 as well as the correct sign, a theoretical procedure was established. It included geometry optimization at the dispersion-corrected DFT level, computation of zero-point vibrational energies, and single-point SCS-MP2 energy calculations with large atomic-orbital basis sets.

Lange, H., Huenerbein, R., Fröhlich, R., Grimme, S., Hoppe, D. (2008). Configurationally Labile Lithiated O-Benzyl Carbamates - Their Application in Asymmetric Synthesis and Quantum Chemical Investigations on the Equilibrium of Diastereomers. CHEMISTRY - AN ASIAN JOURNAL, 3(1), 78-87 [10.1002/asia.200700261].

Configurationally Labile Lithiated O-Benzyl Carbamates - Their Application in Asymmetric Synthesis and Quantum Chemical Investigations on the Equilibrium of Diastereomers

LANGE Heiko;
2008

Abstract

The title compounds were generated by deprotonation of different benzyl-type carbamates with sec-butyllithium in the presence of chiral diamines (-)-sparteine or diisopropyl and di-tert-butyl bis(oxazoline)s. These lithiated species exhibit configurational lability at -78 8C. In the case of the chiral di-tert-butyl bis(oxazoline), the equilibrium of the epimeric complexes can be used synthetically to obtain highly enantioenriched secondary benzyl carbamates. The enantiodetermining step was proven to be a dynamic thermodynamic resolution. The absolute configurations of the products were determined, and the stereochemical pathways of selected substitution reactions were thus elucidated. High level quantum chemical investigations were performed to gain insight into the experimentally investigated system. To obtain an accuracy for the energy difference (DDH) between two epimeric complexes of about 0.5 kcalmol-1 as well as the correct sign, a theoretical procedure was established. It included geometry optimization at the dispersion-corrected DFT level, computation of zero-point vibrational energies, and single-point SCS-MP2 energy calculations with large atomic-orbital basis sets.
Articolo in rivista - Articolo scientifico
Asymmetric synthesis; bis(oxazoline) ligands; lithium; quantum chemical calculations; stereochemistry;
English
2008
3
1
78
87
reserved
Lange, H., Huenerbein, R., Fröhlich, R., Grimme, S., Hoppe, D. (2008). Configurationally Labile Lithiated O-Benzyl Carbamates - Their Application in Asymmetric Synthesis and Quantum Chemical Investigations on the Equilibrium of Diastereomers. CHEMISTRY - AN ASIAN JOURNAL, 3(1), 78-87 [10.1002/asia.200700261].
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10281/320672
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