Light can be considered a clean, renewable, and inexpensive “reagent” for chemical
synthesis. Nevertheless, most conventional methods for the photochemical synthesis of
organic compounds require the use of specialized photochemical equipment that is
capable of generating high-energy ultraviolet light and containing it safely. This is a
practical impediment that has prevented the wide adoption of photochemical synthesis in
the fine chemicals industry. We have developed a strategy that exploits the reactivity of
transition metal photocatalysts in order to perform a variety of synthetically useful
cycloaddition reactions using visible wavelengths of light. By enabling the use of direct
sunlight rather than high-energy artificial UV light, we hope to establish a new,
environmentally responsible approach to synthetic organic photochemistry.