Bicyclic Piperidines via [2 + 2] Photocycloaddition

A synthetic strategy to fused bicyclic piperidines—building blocks for medicinal chemistry—is developed. The key step was an intramolecular [2 + 2]-photocyclization. The photochemical step was performed on a gram scale. Crystallographic analysis of the obtained compounds revealed that they occupy a novel chemical space and can be considered as elongated analogues of 3-substituted piperidines.