The book deals with the synthetic and spectral studies of substituted 2-aminobenzenethiols and their conversion into phenothiazines, 4H-1, 4-benzothiazines and 1, 4- benzothiazino- (2,3-b)-phenothiazines. It also includes the oxidation behavior of 4H-1, 4-benzothiazines and the synthetic and spectral studies of substituted (1,4)- benzoxazino (2,3-b)-phenoxazines. Synthesis of 2-amino-3-methyl-5-nitrobenzenthiol by alkaline hydrolysis of 2-amino-4-methyl-6-nitrobenzothiazole. Synthesis of phenothiazines. by smiles rearrangement of substituted 2-formanido-2-nitrodiphenyl sulphides. The latter were obtained by the reaction of substituted 2-aminobenzenethiol with o-halonitrobenzenes and followed by formylation. Synthesis of 4H-1,4-benzothiazines by the condensation and oxidative cyclisation of 2-aminobenzenethiols with beta-diketone in DMSO. Substituted 1,2,4-trithenodithiazin-3-ones prepared by condensing substituted o-aminobenzenethiols with halogeno-p-benzoquinones (chloranil/bromanil) in presence of fused sodium acetate These were further condensed with some of different o-aminothiophenols yielding 1,4-benezothiazino-(2,3-b)-phenothiazins derivatives.