A Visible Light Ru-Catalyzed Photoredox Access to Substituted Dihydrofurans.

An efficient, visible light Ru(bpy) 3 Cl 2 -catalyzed method for the preparation of 2,3-dihydrofurans is reported. This approach employs 2-bromoketoesters as radical precursors and alkyl enol ethers as acceptors. The photoredox cycle furnishes an oxonium ion that is captured by an internal nucleophile to render the corresponding dihydrofurans. Moreover, the obtained products contain a versatile acetal moiety at C-2, allowing its transformation into a diverse variety of heteroaromatic and nonaromatic compounds. This method could serve as an important tool in the synthesis of complex tetrahydro- and dihydrofurans as well as heteroaromatic structures.