Aryl-aryl cross-coupling reactions without reagents or catalysts: photocyclization of -iodoaryl ethers and related compounds triplet aryl cation intermediates.

Cyclisations of benzyl -iodoaryl ethers to benzo[]chromenes can be effected without reagents or catalysts by irradiation with UVC under flow. Reactions proceed triplet aryl cation generation, 5- and 3--cyclisations, and rearomatisation. They have wide scope, are easy to effect and extend to a myriad of related ring systems.