Ruthenium-Catalyzed Oxidative C-H Bond Alkenylations in Water: Expedient Synthesis of Annulated Lactones

Ruthenium-catalyzed cross-dehydrogenative C-H bond alkenylations occurred efficiently in environmentally benign water, which was exploited for an oxidative phthalide synthesis with ample scope. Mechanistic studies provided strong evidence for the oxidative alkenylation to proceed by an irreversible C-H bond metalation via acetate assistance.