Reaction control in synthetic organic photochemistry: Switching between [5+2] and [2+2] Modes of Cycloaddition

Article abstract of DOI:10.1002/anie.200904059

Split personality: Reaction conditions that enable powerful control over the mode of photocycloaddition in maleimides have been developed. Direct irradiation favors the [5+2] mode whereas sensitized irradiation allows a complete switch to the [2+2] mode (see scheme; TBS=tertbutyldimethylsilyl).