SYNTHESIS OF NEW DIAZA ANGULAR AND TETRAAZA COMPLEX PHENOTHIAZINE RINGS

Abstract

New diaza angular and tetraaza complex phenothiazine rings are synthesized and characterized. Alkaline hydrolysis of 2,4-diamino-6-hydroxy-5-thiocyanatopyrimidine in 20% sodium hydroxide solution and neutralization with acetic acid gave 2,4-diamino-6-hydroxyprimidine-5-thiol (7). Base catalyzed (anhydrous sodium carbonate) condensation of this compound with 2,3-dichloro-1,4-naphthoquinone in yielded the diaza heterocycle 10-amino-5-chloro-8-hydroxybenzo[a]-9,11-diazaphenothiazin-5-one(9). Further condensation of (9) with another molecule of (7) in the presence of anhydrous sodium carbonate gave the tetraaza heterocycle identified as 7,14-diamino-9,12-dihydroxy-6,8,13,15-tetraazabenzo[a][1,4]benzothiazino[3,2-c]pheno thiazine, a deep  red solid. The intense colour, high molar absorptivity of the new heterocycles and the ease re-oxidation of the reduced leuco-bases by atmospheric air (O₂) makes them suitable as vat dyes.

Keywords: 2,4-diamino-6-hydroxypyrimidine-5-thiol, 2,3-dichloro-1,4-naphthoquinone, anhydrous sodium carbonate, hydrolysis, condensation.