The Awakening of a Sleeping Beauty: The ortho Photocycloaddition in the Total Synthesis of Protoilludane- and Prezizaene-Type ­Sesquiterpenes

Photochemical cascade (domino) reactions provide a unique opportunity for the construction of complex molecular architectures. Specifically, an intramolecular ortho photocycloaddition of 7- (alkenyloxy)-indanones triggers a sequence of consecutive reactions that can lead in a single operation to the complete skeleton of two important classes of sesquiterpenes: protoilludanes and prezizaenes. I the former case, two transformations follow the initial photocycloaddition, while in the latter case, there are three consecutive transformations, two of which are initiated by a photon. Remarkably, the reaction cascades proceed with exquisite diastereoselectivity, generating three (protoilludane) or five (prezizaene) stereogenic centers with defined relative configurations. 1 Introduction 2 First Encounter and Initial Studies 3 Protoilludane-Type Sesquiterpenes 4 Prezizaene-Type Sesquiterpenes 5 Enantioselectivity 6 Perspective and Summary.