In 1952, the seminal publication by D. J. Cram and F. A. Abdel Hafez 1b appeared in which a model was introduced since then known as the Cram rules which allowed the analysis of the stereochemical outcome of such reactions. On the basis of the natureof the substituents at the chiral center, two different conformations of the substrate 1 were proposed together with the favored trajectory of the attacking nucleophile to explain the preferential formation of 2 or 3, respectively.