Carbon-13 nuclear magnetic resonance spectral study of some isomeric derivatives of 2-methoxytropone. Troponoid-II

Abstract

The 13C nmr spectra of several isomeric monosubstituted derivatives of 2-methoxytropone together with some dibromo derivatives have been obtained and analysed. Substituent parameters were defined and shown to exhibit additivity. Differences with corresponding parameters for monosubstituted benzene analogs suggest proximity interactions between the 3-substituents and the 2-OCH3 group as well as between 7-substituents and the adjacent carbonyl group. The data indicates that the OCH3 group is a convenient probe to investigate the orientation of mesomeric electronic charge transfer to the various carbons of the tropone seven-membered ring. Finally, it is demonstrated that 13C nmr is quite useful to distinguish between the various substituted 2-methoxytropones.