Synthesis of polycyclic mixed phenothiazine-phenoxazine organic dyes

Abstract

<p>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.</p