Triarylmethyl Cations as Photocatalysts for Radical-Mediated Cycloaddition Reactions

We have developed a novel photocatalytic system using readily available triarylmethyl cations for radical-mediated (4 + 2) and (2 + 2) cycloaddition reactions. A variety of substituted triarylmethyl cations were investigated, and the optimal catalyst exhibited high efficiency and broad substrate scope, affording the desired cycloadducts in good to excellent yields with high regio- and diastereoselectivities. Furthermore, the catalyst could be immobilized on a polymer support and reused multiple times without a significant loss of activity.