Scandium-Catalyzed Preparation of Cytotoxic 3-Functionalized Quinolin-2-ones: Regioselective Ring Enlargement of Isatins or Imino Isatins

Trimethylsilyldiazomethane in the presence of catalytic amounts of Sc(OTf)3 smoothly promotes the ring expansion of isatins or imino isatins to efficiently afford 3-functionalized quinolin-2-ones through controlled ring enlargement. Whereas the ring-expansion reaction of azetidine-2,3-diones led to the adduct resulting from migration of the carbonyl group, the ring-expansion reaction of oxindole derivatives gave the adduct resulting from migration of the aryl group. To rationalize the experimental observations, theoretical studies have been performed. Moreover, the biological activity of some of the synthesized heterocycles has been evaluated in four cancer cell lines.