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 K2CO3 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).

Newly synthesized 3-sulfenylindole derivatives from 4-hydroxydithiocoumarin using an oxidative cross dehydrogenative coupling reaction (OCDCR): potential lead molecules for antiproliferative activity.

An expedient and efficient synthetic method was developed for the oxidative cross dehydrogenative coupling reaction between 4-hydroxydithiocoumarin and indole at the C-3 position regio-selectively using a combination of 10 mol% molecular iodine and TBHP in the presence of 10 mol% CuBr2 as an additive at room temperature. Mild reaction conditions, good yields and a broad substrate scope are some of the salient features of the present protocol. Additionally, the synthesized 3-sulfenylindoles derived from 4-hydroxydithiocoumarin were converted into biologically active sulfone derivatives. Interestingly, some of the compounds exhibit anti-cell proliferative activity on breast cancer (MCF-7) cells due to reactive oxygen species (ROS) mediated cell damage.