Rapid Access to New Angular Phenothiazine and Phenoxazine Dyes

Abstract

The synthesis of some new thiophenyl‐derivatized and furanyl‐derivatized phenothiazine and phenoxazine dyestuffs is described. This was achieved by two methods after the synthesis of 6‐chloro‐5H‐benzo[a]phenothiazin‐5‐one, 6‐chloro‐5H‐benzo[a]phenoxazin‐5‐one, and 6‐chloro‐5H‐naphtho[2,1‐b]pyrido[2,3‐e][1,4]oxazin‐5‐one intermediates via anhydrous base condensation reaction of 2,3‐dichloro‐1,4‐naphthoquinone with 2‐aminothiophenol, 2‐aminophenol, and 2‐aminopyridinol, respectively. The first method involved treatment of tributyl(thien‐2‐yl) or tributyl(furan‐2‐yl) stannane with chlorophenothiazine/chlorophenoxazine under mild basic chemical formula (CsF) and 1,4‐dioxane or toluene solvent at 80°C to supply dazzling yellow solid in high yields. In the second method, the catalytic system was pre‐activated in acetonitrile, followed by addition of coupling partners and K3PO4 to obtain high melting and variety of highly colored products in moderate to high yields. The reaction conditions were compatible with unprotected N–H and carbonyl functional groups. The intense colors of these dyes and their ease of re‐oxidation of Na2S2O4‐reduced derivatives make them suitable as vat dyes. Also, they were found to be good colorants for textiles, papers, paint, ink, soap, polish, candle, and plastic materials.