Copper(i)-catalyzed intramolecular [2 + 2] cycloaddition of 1,6-enyne-derived ketenimine: an efficient construction of strained and bridged 7-substituted-3-heterobicyclo[3.1.1]heptan-6-one

The transformation of 1,6-enynes into bridged bicyclic systems was accomplished for the first time by a copper(I)-catalyzed tandem cycloaddition reaction. The reaction provides a straightforward approach for the synthesis of structurally diverse, strained and bridged bicycles in good yields with moderate to excellent diastereoselectivities.