One-pot mild and efficient synthesis of [1,3]thiazino[3,2-a]indol-4-ones and their anti-proliferative activity.

A base mediated environmentally benign one-pot efficient methodology has been developed for the synthesis of [1,3]thiazino[3,2-a]indol-4-ones using indoline-2-thiones and propiolate esters in aqueous medium. The conjugate addition of thiones first results in ethyl (3-(indol-2-yl)thio)acrylates in situ, which subsequently undergoes intramolecular cyclization to produce indole-fused thiazin-4-ones in good to excellent yields. The cytotoxic screening of the synthesized compounds using MTT assay revealed the anti-proliferative nature of these frameworks against triple negative breast cancer cell lines with the highest activity emanating from 4H-[1,3]thiazino[3,2-a]indol-4-one and 8-methyl-2-propyl-4H-[1,3]thiazino[3,2-a]indol-4-one compounds.