Complex Carbocyclic Skeletons from Aryl Ketones through a Three‐Photon Cascade Reaction

Starting from readily available 7‐substituted 1‐indanones, products with a tetracyclo[5.3.1.0(1,7)0(4,11)]undec‐2‐ene skeleton were obtained upon irradiation at λ=350 nm (eight examples, 49–67 % yield). The assembly of the structurally complex carbon framework proceeds in a three‐photon process comprising an ortho photocycloaddition, a disrotatory [4π] photocyclization, and a di‐π‐methane rearrangement. The flat aromatic core of the starting material is converted into a functionalized polycyclic hydrocarbon with exit vectors in three dimensions. Ring opening reactions at the central cyclopropane ring were explored, which enable the preparation of tricyclo[5.3.1.0(4,11)]undec‐2‐enes and of tricyclo[6.2.1.0(1,5)]undecanes.