Intramolecular Crossed [2 + 2] Cycloaddition through Visible‐light Triplet Sensitization: Expedient Access to Bridged Bicyclic Alkene

A visible‐light‐induced intramolecular crossed [2 + 2] cycloaddition reaction of allene‐tethered alkylidenecyclopropanes was reported in this paper. The reactions were conducted under mild conditions using Iridium(III) catalyst FirPic as a photosensitizer for energy transfer, affording bridged bicyclic alkenes in moderate to good yields with excellent regioselectivity and stereoselectivity through the regulation of substituents at the olefin’s terminal position. Meanwhile, the computational study explained the special region control assisted by sulfonyl radicals in detail.