NMR study of inversion isomerism in some isoxazolidines
作者:
Mohammed I. M. Wazeer,
Sk. Asrof Ali,
期刊:
Magnetic Resonance in Chemistry
(WILEY Available online 1993)
卷期:
Volume 31,
issue 1
页码: 12-16
ISSN:0749-1581
年代: 1993
DOI:10.1002/mrc.1260310105
出版商: John Wiley&Sons, Ltd.
关键词: Isoxazolidines;13C chemical shifts;Nitrogen inversion
数据来源: WILEY
摘要:
AbstractCarbon‐13 NMR spectra were recorded for two series of isoxazolidines, 3 (a 5/5 fused system) and 4 (a 6/5 fused system), over the temperature range − 100 to +60°C. Whereas all the compounds in series 3 existed solely as one isomer throughout this temperature range, some compounds in series 4 showed the presence of two isomers of unequal population at low temperatures. The major isomer was shown to be thetransconformer, which is in equilibrium with the minor isomer (cisconformer) through a relatively slow nitrogen inversion. The monosubstituted isoxazolidines 4 havingendosubstituents at either C‐2 or C‐3 and 2,3‐di‐ and 2,2,3‐trisubstituted compounds showed the presence of only one isomer throughout the temperature range. The barriers to nitrogen inversion were determined by band shape analysis and were in the range 65.2
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