Determination of energy barriers to rotation and absolute conformations of thermally interconvertible 5,5-dimethyl-3-(o-aryl)-2,4-oxazolidinedione enantiomers
作者:Öznur Demir Ordu、İlknur Doğan
DOI:10.1016/j.tetasy.2003.12.039
日期:2004.3
The activation barriers for the interconversion between the enantiomers of 5,5-dimethyl-3-(o-aryl)-2,4-oxazolidinediones (M = P) have been determined by temperature dependent NMR and by enantioresolution on chiral sorbents via HPLC. The activation barriers were found to increase linearly with the size of the van der Waals radii of the ortho-halogen substituents. The enantiomers of the o-iodo derivative were micropreparatively enriched on a Chiralpak AD column, leading to the determination of its barrier to rotation via thermal racemization and resulting in the assignments of conformations in the presence of the optically active chiral auxiliary (S)-(+)-1-(9-anthryl)-2,2,2-trifluoro ethanol [(S)-TFAE]. (C) 2004 Elsevier Ltd. All rights reserved.
N-Substituted Oxazolidinediones
作者:Seymour L. Shapiro、Ira M. Rose、Frank C. Testa、Eric Roskin、Louis Freedman
DOI:10.1021/ja01533a042
日期:1959.12
Axially chiral N-(o-aryl)-4-hydroxy-2-oxazolidinone derivatives from diastereoselective reduction of N-(o-aryl)-2,4-oxazolidinediones: Thermally interconvertible atropisomers via ring-chain-ring tautomerization
作者:Ãznur Demir-Ordu、IÌlknur DogÌan
DOI:10.1002/chir.20811
日期:——
The reduction of the axiallychiral N‐(o‐aryl)‐5,5‐dimethyl‐2,4‐oxazolidinediones by NaBH4 yielded axiallychiral N‐(o‐aryl)‐4‐hydroxy‐5,5‐dimethyl‐2‐oxazolidinone enantiomers having a chiral center at C‐4, with 100% diastereoselectivity as has been shown by their 1H and 13C NMR spectra and by enantioselective HPLC analysis. The resolved enantiomeric isomers were found to interconvert thermally through