The Lewis acid promoted hetero-cycloaddition of a series of ketene imines to stereogenic (S)-α-alkoxy aldehydes is regiospecific and gives diastereomeric mixtures of the corresponding opticallyactive 2-iminooxetanes. The possibility of achieving a “chelation” or “non-chelation” controlled facial selectivity is investigated. The non-chelating Lewis acids (BF3.Et2O and ZnCl2.Et2O) govern the selectivity