Cobalt(III)-Catalyzed Oxidative Annulation of Benzaldehydes with Internal Alkynes via C–H Functionalization in Poly(ethylene glycol)

A novel Co(III)-catalyzed oxidative annulation of aromatic aldehydes with internal alkynes for accessing isocoumarins is described, which is achieved by oxidation, weak chelation-assisted C–H bond functionalization, and annulation cascades with excellent functional group compatibility, high atom economy, and step efficiency. By using environmentally benign and inexpensive poly(ethylene glycol)-400 (PEG-400), the Co/Cu/PEG-400 system could be recycled and reused.