A photo-induced three-component reaction of N-aryl piperidines, sulfur dioxide, and cycloketone oxime esters.

A novel, external-oxidant-free method for synthesizing β-sulfonylated piperidines is established via a visible-light-driven three-component reaction. The reaction proceeds smoothly at room temperature, delivering products with good substrate generality. Control experiments support a radical mechanism, which entails ring-opening of the oxime ester, sulfur dioxide capture, and key SET oxidation steps.