TfOH-triggered denitrogenative union of diazo carbonyl compounds and indolin-2-thiones toward functionalized indole derivatives and their preliminary anticancer assessment.

A metal-free, chemoselective TfOH-mediated union of α-diazo carbonyl compounds and indolin-2-thiones to access functionalized indoles has been disclosed. Interestingly, indolin-2-thiones treated with α-diazo esters delivered indolyl thioethers through formal S-H insertion, and α-diazo ketones provided fused hybrid heterocyclic systems, thiazolo[3,2-a]indoles, through a cascade process involving S-H insertion, cyclization, and dehydration. Furthermore, these newly synthesized compounds showed promising anti-cancer activities against breast cancer and prostate cancer cell models.