Novel benzothiazapine azo dyes: synthesis, characterisation and printing properties

Purpose - The purpose of this paper is to synthesise new heterocyclic disperse azo dyes based on benzothiazapine moiety and their printability on synthetic fabrics. Design/methodology/approach - Ethyl cyanoacetate was refluxed with aniline derivatives for 3 h to form cyanoacetanilides which coupled with different diazonium salts. The products obtained were cyclised with 2-amino thiophenol to form arylazo benzothiazapine derivatives. The structures of the new dyes were characterised by micro-analysis as well as IR, H-1 NMR and C-13 NMR. Printing pastes containing the dyestuffs prepared and thickened with sodium alginate were used for printing synthetic fabrics using either transfer printing or traditional screen printing. Findings - New heterocyclic monoazo dyes derived from benzothiazabine moiety were obtained by the coupling of diazotised aniline derivatives with ethylcyanoacetate anilides followed by cyclisation with 2-amino thiophenol. The use of synthesised dyes for transfer- or screen-printing polyester and nylon 6 fabrics has been studied. The synthesised dyes which contain electron withdrawing substituents (NO2) in the phenyl ring attached to the azo groups and electron-donating (OCH3) group on the other phenyl ring exert a bathochromic effect. Research limitations/implications - Synthesis of azo dyes containing benzothiazapine moiety has never been reported in textile printing. Practical implications - Production of simple and less costly dyes. Originality/value - Synthesis of aryl azo benzothiazapine dyes by a simple method and application in printing of synthetic fabrics.