Synthesis of biologically active fused 1,4-oxathiin derivatives from 4-hydroxydithiocoumarins, arylacetylenes and dimethyl sulfoxide by Cu()-catalyzed C-H functionalization and cross-dehydrogenative C-S coupling reactions

The hitherto unreported 2-aryl-10 H -thiochromeno[3,2- b ][1,4]oxathiin-10-one derivatives are obtained in a single pot from 4-hydroxydithiocoumarins, arylacetylenes and dimethyl sulfoxide in the presence of 10 mol% CuI and K 2 CO 3 in an oil bath at 70 °C. The novelties of the present protocol are (i) selective C-H functionalization at the C-3 position of 4-hydroxydithiocoumarin, (ii) regioselective hydrothiolation with arylacetylenes and (iii) concomitant cyclisation. The major advantages are mild reaction conditions, broad substrate scope and good yield. Among the synthesized compounds, the following five compounds 3aa , 3bd , 3ec , 3fa , and 3fd showed anticancer activity against a human breast cancer cell line (MCF-7) and a cervical cancer cell line (HeLa). Novel synthesis of fused 1,4-oxathiin derivatives is reported via a pseudo-three component reaction, where DMSO acts as an oxygen donor and a solvent, and some of them exhibited anti-cancer activities.