Zusammenfassung
N,N-Dimethylthiobenzamides bearing hydrogen atoms in both orthopositions were shown by 1H NMR in the presence of an optically active alcohol to have non-coplanar π-systems. The barrier to rotation about the C(sp2-C(sp2) bond amounts to 43 ± 2 kJ/mol. Liquid chromatography on triacetylcellulose served for the enrichment of enantiomers of 2-substituted thiobenzamides. In several cases considerable ...
Zusammenfassung
N,N-Dimethylthiobenzamides bearing hydrogen atoms in both orthopositions were shown by 1H NMR in the presence of an optically active alcohol to have non-coplanar π-systems. The barrier to rotation about the C(sp2-C(sp2) bond amounts to 43 ± 2 kJ/mol. Liquid chromatography on triacetylcellulose served for the enrichment of enantiomers of 2-substituted thiobenzamides. In several cases considerable enantioselectivity (relative retention up to 8.7) was observed. The barriers to enantiomerization (Tables 3, 4 and 5), determined by thermal racemization, were discussed in terms of non-bonding interactions, electrostatic repulsions and buttressing effects in the transition state of rotation.
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