13C NMR of N-heterocycles. Conformation OF phenothiazines and 2,3-diazaphenothiazines

Abstract

Abstract Phenothiazines, 2,3-diazaphenothiazines, and numerous derivatives have been investigated by 13C and 1H NMR spectroscopy in order to study the electronic properties of these heterocyclic systems and the conformation of the ligands at N-10. The psychopharmacological activity of phenothiazine derivatives seems to be related both to the electron donor properties and to the side chain attached at N-10. The orientation of such substituents assumes a particular interest in view of the X-ray results, which contradict the theoretical predictions and also seem to be inconsistent with the chemical reactivity. The results for the crystal phase are discussed together with those obtained for the solution by NMR analysis. Unusually large y, S, and e effects, all to low field, are observed. Measurements in different solvents and CNDO charge density calculations have been performed.