Complexity from Simplicity: Tricyclic Aziridines from the Rearrangement of Pyrroles by Batch and Flow Photochemistry

摘要

The use of photochemistry has a long and rich history in organic synthesis. Performing reactions specific to an excited state by simple UV irradiation can enable a low cost, environmentally benign, reagent- and catalyst-free entry to molecular complexity. For example, the alkene [2+2] cyclo-addition has proven to be a photochemical workhorse in the construction of complex natural products. In the field of arene photochemistry, the meta-photocycloaddition reaction is an outstanding example of the extensive bond reorganization that can only be achieved through a photo-induced excited state. The application of this reaction in natural product synthesis has been demonstrated by the pioneering studies of Wender and others. In contrast, the photochemistry of nitrogenous heteroaromatic systems is less advanced, although useful procedures, involving rearrangement and reactive-intermediate solvation, have been developed and applied in synthesis. Herein, we report a novel and general photochemical reaction sequence that results in the formation of tricyclic, fused aziridine ring systems from simple pyrrole derivatives.