2-Isoxazolidineethanols: an NMR study of the effect of intramolecular H-bonding on the population of nitrogen invertomers and inversion process.
A series of (betaR,5R)- and (betaR,5S)-2,5-disubstituted isoxazolidines: 5-(substituent)-beta-phenyl-2-isoxazolidineethanols, have been prepared by asymmetric nitrone cycloaddition reactions and their NMR spectra recorded over a wide range of temperatures. The spectra at low temperatures indicate the presence of the (betaR,5S) diasteromer almost exclusively as a single invertomer having trans disposition of the substituents at N(2) and C(5), while the (betaR,5R) diasteromer remained as a mixture of two interconverting invertomers in deuterated chloroform. The effect of H-bonding - intramolecular in CDCl(3) and intermolecular in CD(3)OD - on the population ratio of the invertomers and nitrogen inversion process has been investigated. The nitrogen inversion barriers are determined using complete line-shape analysis, and their dependence on solvent is discussed. Due to steric factor the trans-invertomers are found to be more stable than their cis counterparts.
Ali
Shaikh A
SA
Chemistry Department, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia. shaikh@kfupm.edu.sa
Iman
Muhammad Z N
MZ
Wazeer
Mohamed I M
MI
Fettouhi
Mohammed B
MB
D000431:Ethanol / Q000737:chemistry*; D006860:Hydrogen Bonding; D007536:Isomerism; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D009584:Nitrogen / Q000737:chemistry*; D010080:Oxazoles / Q000737:chemistry*; D013816:Thermodynamics
D010080:Oxazoles; D000431:Ethanol; D009584:Nitrogen