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

The hitherto unreported 2-aryl-10H-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 KCO 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).