Photocatalytic Activation of Heterocyclic Iodonium Ylides for the Synthesis of Dihydrofuropyranones and Dihydrofuropyridones.

β-Distabilized iodonium ylides undergo photocatalytic activation using neutral eosin Y and visible light to afford dihydrofuropyranones, dihydrofuropyridones, and dihydrofurans. Steady-state absorption spectroscopy and application of the method of continuous variations to complexation-induced chemical shifts provide evidence for the binary complexation of eosin Y and β-distabilized iodonium ylides. Preliminary mechanistic studies using transient absorption spectroscopy suggest monoanionic eosin Y as the active photocatalyst functioning via an oxidative quenching cycle. This simple approach to enhancing the reactivity of heterocyclic iodonium ylides expands the scope of their use as building blocks in the synthesis of heterocycles.