[2 + 2] Cycloaddition of chlorosulfonylisocyanate to chiral alkyl vinyl ethers bearing a sterogenic center in the alkyl part of the ether afford the corresponding azetidin-2-ones with relatively good asymmetric induction in certain cases. Reactions were shown to depend on steric requirements of the ligands at the stereogenic center. The model that rationalizes the stereochemical outcome is based on