Visible-Light-Mediated Oxidative Coupling of Vinylarenes with Bromocarboxylates Leading to γ-Ketoesters.

A photocatalytic strategy for the synthesis of γ-ketoesters was reported. Using DMSO as both the solvent and terminal oxidant, oxidative coupling of vinylarenes with bromocarboxylates proceeded readily, giving a variety of γ-ketoesters in good isolated yields and with a broad functional-group tolerance.

Preparation of oxazolines and oxazoles via a PhI(OAc)2-promoted cyclization of N-propargylamides.

A metal-free cyclization of N-propargylamides for the synthesis of various oxazolines and oxazoles via a 5-exo-dig process is presented. Using (diacetoxyiodo)benzene (PIDA) as a reaction promoter and lithium iodide (LiI) as an iodine source, intramolecular iodooxygenation of N-propargylamides proceeded readily, leading to the corresponding (E)-5-iodomethylene-2-oxazolines in good to excellent isolated yields. In addition, using the PhI(OAc)2/LiI system, N-propargylamides can be converted to the corresponding oxazole-5-carbaldehydes in the presence of oxygen under visible light irradiation. The resulting products can be further converted into various oxazoline and oxazole derivatives after simple derivatizations, and this method ultimately offers an efficient route to a variety of biologically active structures.