Highly Active Potential Antituberculotics: 3-(4-Alkylphenyl)-4-thioxo-2H-1,3-benzoxazine-2(3H)-ones and 3-(4-Alkylphenyl)-2H-1,3-benzoxazine-2,4(3H)-dihiones Substituted in Ring-B by Halogen

A series of 6-chloro-3-(4-alkylphenyl)-4-thioxo-2H-1,3-benzoxazine-2(3H)-ones, 7-chloro-3-(4-alkylphenyl)-4-thioxo-2H-1,3-benzoxazine-2(3H)-ones, 6-bromo-3-(4-alkylphenyl)-4-thioxo-2H-1,3-benzoxazine-2(3H)-ones, 6,8-dibromo-3-(4-alkylphenyl)-4-thioxo-2H-1,3-benzoxazine-2(3H)-ones, 6-chloro-3-(4-alkylphenyl)-2H-1,3-benzoxazine-2,4(3H)-dithiones, 7-chloro-3-(4-alkylphenyl)-2H-1,3-benzoxazine-2,4(3H)-dithiones, 6-bromo-3-(4-alkylphenyl)-2H-1,3-benzoxazine-2,4(3H)-dithiones and 6,8-dibromo-3-(4-alkylphenyl)-2H-1,3-benzoxazine-2,4(3H)-dithiones was synthesized. The compounds exhibited in-vitro activity against Mycobacterium tuberculosis, M. kansasii (two strains), and M. avium. 6-bromo-3-(4-propylphenyl)-4-thioxo-2H-1,3-benzoxazin-2(3H)-one and 6-bromo-3-(4-propylphenyl)-2H-1,3-benzoxazin-2,4(3H)-dithione are the most active compounds against M. tuberculosis. The activity is similar to isoniazid (INH). The compounds under study have a broad spectrum of activity against potential pathogenic strains. The replacement of the oxo group by thioxo group of 3-(4-alkylphenyl)-2H-1,3-benzoxazine-2,4(3H)-diones often led to an improvement in the antimycobacterial activity against M. tuberculosis.