particularly [8+2] cycloadditions, are a straightforward and efficient strategy for constructing significant medium‐sized architectures. Typically, configuration‐restrained conjugated systems are utilized as 8π‐components for higher‐order concerted cycloadditions. However, for this reason, 10‐membered monocyclic skeletons have never been constructed via catalytic asymmetric [8+2] cycloaddition with
Copper(I)‐catalyzed [2+2] cycloadditions of various ketenes with 2‐nitrosopyridine to afford synthetically highly valuable 1,2‐oxazetidine‐3‐ones are shown to occur with good enantioselectivities. The thermal uncatalyzed process furnishes the unstable regioisomeric oxazetidinone. Density function theory (DFT) calculations give evidence that the reaction occurs via a concerted [2+2] cycloaddtion pathway