The synthesis of some new angular and Y-shaped azaphenothiazine ring systems from simple heterocyclic compounds is described. 3-Nitration of pyridin-4[1H]-one (7) followed by reduction and thiation with P2S5 gave 3-aminopyridine-4 [1H]-thione (10) in good yields. Reaction of product 10 with 2,3-dichloro-1,4-naphthoquinone (12) gave a red dyestuff, 6-chloro-7-thia-10,12-diazabenz [a]anthracen-5-one (13) having a new angular azaphenothiazine ring system. Two facile methods were also proposed for the synthesis of 15,16-dithia-1,5,10-triazahenzo[h]pentaphene (26) from 3-aminopyridine-2[1H]-thione (25, R= H) and 2-aminothiophenol. The purple pigment 26, R= H is the parent compound of this Y-shaped azaphenothiazine. Reduction of these dyestuffs (13 and 26) and their derivatives led to loss of colour which reappeared on exposure to atmospheric oxygen. This property makes them applicable as vat dyes. Additionally they were found to be good colorants for soap, candle, polish, paint and plastic materials.
Dyes and Pigments 12/1991; 16(2):149–163. DOI:10.1016/0143-7208(91)85006-T