Ruthenium-Catalyzed Regioselective C3(sp2)-H Functionalization of Coumarin-Indole Conjugates

Abstract

We have developed a highly regioselective ruthenium-catalyzed directing-group-assisted C3(sp2)-H functionalization of a coumarin-indole conjugate, in which the carbonyl oxygen acts as a weak directing group. The directing group forms a coordination bond with Ru metal, and then transition-metal-assisted C-H activation occurs at the proximal C-H bond. Here, we have synthesized the hybrid of two biologically active moieties. The carbonyl group of coumarin activated the C3-H bond of the indole moiety, which subsequently undergoes C-H functionalization in the presence of alkenes. The optimization of reactions was performed using different types of catalysts, additives, oxidants, and solvents at different temperatures and reaction times.