Diastereoselective\nConstruction\nof Bridged Azabicyclo[3.2.1]octane\nvia Copper-Catalyzed Formal [4 + 3] Cycloaddition

A novel\ncopper-catalyzed formal diastereoselective [4 + 3] cycloaddition\nof 2-arylaziridines and 2-substituted cyclopentadiene was developed.\nThis transformation provided an efficient protocol for the assembly\nof a highly strained bridged azabicyclo[3.2.1]octane scaffold, which\nis widespread in bioactive natural products. A likely mechanism showed\nthat the reaction proceeds through [3 + 2] cycloaddition, ring opening,\nand aza-Michael addition cascade reaction. This protocol features\nhigh efficiency and diastereoselectivity, wide functional group compatibility,\nand a cheap catalyst.