Diastereoselective Alkylation of β-Amino Esters: Structural and Rate Studies Reveal Alkylations of Hexameric Lithium Enolates
| Autor: | Emil B. Lobkovsky, Sol M. Gruner, David B. Collum, Timothy A. Ayers, Anne J. McNeil, Sithamalli V. Chandramouli, Vanasse Benoit J, Gilman E. S. Toombes |
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| Rok vydání: | 2004 |
| Předmět: |
Models
Molecular Reaction mechanism Magnetic Resonance Spectroscopy Alkylation Amino esters Chemistry Stereochemistry Esters Stereoisomerism General Chemistry Nuclear magnetic resonance spectroscopy Lithium Random hexamer Crystallography X-Ray Biochemistry Catalysis Kinetics Crystallography Colloid and Surface Chemistry Reaction rate constant Organometallic Compounds Amino Acids Equilibrium constant |
| Zdroj: | Journal of the American Chemical Society. 126:16559-16568 |
| ISSN: | 1520-5126 0002-7863 |
| DOI: | 10.1021/ja045144i |
| Popis: | Alkylation of beta-amino ester enolates proceeds with high diastereoselectivity. Single crystal, powder, and solution X-ray diffraction studies of the enolate show that the racemic enolate forms prismatic hexamers. 6Li NMR spectroscopic studies on partially racemic enolates reveal complex mixtures of homo- and heterochiral hexamers. An implicit fit of the aggregate populations to the Boltzmann distribution provides the free energy differences and equilibrium constants for the ensemble. Rate studies show that enolate alkylation occurs directly from the hexamer with participation by THF. A mechanism based on the alkylation of a ladder-like aggregate is proposed. |
| Databáze: | OpenAIRE |
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