Laccase-catalyzed green synthesis and cytotoxic activity of novel pyrimidobenzothiazoles and catechol thioethers

The laccase-catalyzed reaction between unsubstituted catechol and 2-thioxopyrimidin-4(1H)-ones using aerial O₂ as the oxidant delivers novel pyrimidobenzothiazoles with high yields in an aqueous solvent system under mild reaction conditions. With 4-substituted catechols, catechol thioethers are formed exclusively. The synthetic protocols developed provide a sustainable approach for these compound classes. In addition, the cytotoxicity of the products against HepG2 cell line is reported. Most compounds exhibit antiproliferative activities with IC₅₀ values at the micromolar level. A structure–activity relationship study will facilitate the further development of these compounds as cytotoxic agents.