Ru(II)-Catalyzed [3 + 3] Annulation of Benzamides with Iodonium Ylides via Redox-Neutral C-H Bond Functionalization

A ruthenium-catalyzed site-selective tandem annulation of iodonium ylides with substituted benzamides through C-H bond activation in a redox-neutral manner is described. In the reaction, substituted isocoumarin derivatives were observed in good to excellent yields, in which C-C/C-O bonds formed in one pot. In this protocol, iodonium ylides act as a carbene surrogate and tosylamide serves as a directing group in the catalytic system. Later, the isocoumarin derivative was aromatized to synthesize the biologically crucial chromenone derivative. A possible reaction mechanism involving C-H bond activation as a key step was proposed to account for the present reaction.