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Pronounced stereospecificity of 1H, 13C, 15N and 77Se shielding constants in the selenophenyl oximes as shown by NMR spectroscopy and GIAO calculations

✍ Scribed by Andrei V. Afonin; Dmitry V. Pavlov; Igor A. Ushakov; Elena Yu. Schmidt; Al'bina I. Mikhaleva

Publisher
John Wiley and Sons
Year
2009
Tongue
English
Weight
132 KB
Volume
47
Category
Article
ISSN
0749-1581

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✦ Synopsis

Abstract

In the ^1^H and ^13^C NMR spectra of 1‐(2‐selenophenyl)‐1‐alkanone oximes, the ^1^H, the ^13^C‐3 and ^13^C‐5 signals of the selenophene ring are shifted by 0.1–0.4, 2.5–3.0 and 5.5–6.0 ppm, respectively, to higher frequencies, whereas those of the ^13^C‐1, ^13^C‐2 and ^13^C‐4 carbons are shifted by 4–5, ∼11 and ∼1.7 ppm to lower frequencies on going from the E to Z isomer. The ^15^N chemical shift of the oximic nitrogen is larger by 13–16 ppm in the E isomer relative to the Z isomer. An extraordinarily large difference (above 90 ppm) between the ^77^Se resonance positions is revealed in the studied oxime isomers, the ^77^Se peak being shifted to higher frequencies in the Z isomer. The trends in the changes of the measured chemical shifts are well reproduced by the GIAO calculations of the ^1^H, ^13^C, ^15^N and ^77^Se shielding constants in the energy‐favorable conformation with the syn orientation of theCNOH group relative to the selenophene ring. Copyright © 2009 John Wiley & Sons, Ltd.

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