Synthesis of polycyclic mixed phenothiazine-phenoxazine organic dyes

GRAPHICAL ABSTRACT ABSTRACT A convenient synthesis of new polycyclic mixed phenothiazine-phenoxazine compounds is described. The cross-coupling of 2,4-diaminothiophenol with 2,3-dichloro-1,4-naphthoquin one at room temperature gave reddish brown 10-amino-6-chlorobenzo[a]phenoxazin-5-one which was converted into a benzoxazinophenothiazin-12-amine in 58% yield via reaction with 2-aminothiophenol under anhydrous basic conditions. A three-component one-pot synthesis improved the yield of benzoxazinophenothia-12-amine to 81% a in shorter time compared to two steps reactions. The synthesis of new azomethine derivatives of benzo[a]benzo[5,6] [1,4] oxazino [3,2-c] phenothiazin-12-amine with extended conjugations and excellent yields were also reported. The structural assignments of the prepared compounds were established by combine Ultraviolet-Visible, Fourier Transform Infrared, 1H and 13C Nuclear Magnetic Resonance Spectroscopies, Mass Spectrometry and elemental analytical data. The ease of preparations in high yields and their intense colourations make these compounds applicable as dyestuffs.