Synthesis of new N-alkyl and N-acyldioxinophenothlazine and acridinone derivatives

The synthesis of new substituted dioxino[b]- and [c]phenothiazines or acridinones is reported. N-Arylation of [1,4]benzodioxin-6-amine with organolead or organobismuth reagents gave N-aryl-2,3-dihydro- 1,4-benzodioxin-6-amine; subsequent Bernthsen thionation led to phenothiazine ring formation, followed by N-acylation. On the other hand [1,4]benzodioxin-6-amine was first N-alkylated and the resulting alkylamines were N-phenylated before Bernthsen thionation to provide the tetracyclic phenothiazines. Alternative arylation with chlorobenzoic acid followed by cyclization under acidic conditions afforded the dioxinoacridinones, which were successfully alkylated.