Sequential Visible Light-Induced Reactions Using Different Photocatalysts: Transformation of Furans into 2-Pyridones via γ-Lactams Using a New Ring Expansion Reaction

A new photocatalytic ring expansion reaction that transforms gamma-lactams into 2-pyridones is described. The reaction is radical-triggered and was inspired by a late-stage oxidation commonly observed in fungal metabolism. The reaction is particularly powerful because it can be included in a one pot process which converts readily accessible furans directly into 2-pyridones through sequential photo-induced reactions (energy transfer and electron transfer). The study also unveiled unprecedented reactivity for the mild and metal-free photocatalyst eosin, wherein it is used to cleave a C-I bond activated only by an electron donor on the neighbouring carbon.

Automated summary

This study describes a new photocatalytic ring expansion reaction that converts gamma-lactams into 2-pyridones, inspired by a late-stage oxidation commonly observed in fungal metabolism. The reaction is highly powerful and can directly convert readily accessible furans into 2-pyridones through sequential photo-induced reactions (energy transfer and electron transfer).