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

Starting from readily available 7-substituted 1-indanones, products with a tetracyclo[5.3.1.01,7 04,11 ]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[5.3.1.04,11 ]undec-2-enes and of tricyclo[6.2.1.01,5 ]undecanes.