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Schiff bases of gossypol: an NMR and DFT study

✍ Scribed by Quang Ton That; Kim Phi Phung Nguyen; Poul Erik Hansen

Publisher
John Wiley and Sons
Year
2005
Tongue
English
Weight
132 KB
Volume
43
Category
Article
ISSN
0749-1581

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✦ Synopsis

Abstract

Schiff bases of gossypol with benzylamine, methylamine, 4‐aminoacetophenone and 4‐fluoroaniline have been synthesized and characterized by NMR spectroscopy. All the Schiff bases of gossypol are in the enamine form according to ^3^J(HC,NH) and ^1^J(N,H) coupling constants. The spectra are basically unchanged by change of solvent (CD~2~Cl~2~, THF‐d~8~ and CD~3~OD) and by variation of temperature. For the derivative of benzylamine, deuterium isotope effects on ^13^C chemical shifts are determined. They support strongly the enamine form and serve as a reference for other tautomeric Schiff bases. Structures and NMR nuclear shieldings of model compounds (the second monomer is replaced by a 2‐hydroxybenzene ring) have been calculated by density functional theory (DFT) methods. A good correlation is observed between calculated ^13^C nuclear shieldings of the enamine form and observed ^13^C chemical shifts. Copyright © 2005 John Wiley & Sons, Ltd.

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