The synthesis of 6-substituted aryl derivatives of 8-methyl-1,11-diazabenzo[a]phenothiazin-5-one, potential vat dyes is reported. This was achieved by condensation reaction between 2-amino-4-methylpyridine-3-thiol and 6,7-dibromo-5,8-quinolinequinone under anhydrous basic condition to obtain 6-bromo-8-methyl-1,11-diazabenzo[a]phenothiazin-5-one as the parent compound. The 6-aryl derivatives of this parent compound were obtained using Suzuki-Miyaura protocol. The structure of the synthesized compounds was established by spectra and analytical data obtained. These compounds showed great potentials as vat dyes.