Stereochemical Behavior of Silicon Five‐Membered Rings: A Comparison of the Nucleophilic Displacements of Intracyclic Si‐o and Si‐S Bonds

Abstract

Abstract A synthetic route to the new optically active 2‐(1‐naphthyl)‐2‐phenyl‐1‐thia‐2‐silacyclopentane is described. A comparison of the optically active oxa‐ and thiasilacyclopentanes shows that the most electronegative leaving group, i.e., the oxygen atom, leads preferentially to retention. The less electronegative leaving group, i.e., the sulfur atom, reacts mainly with inversion. The results are in disagreement with a mechanism governed by the apicophilicity of the substituents attached at silicon. In contrast, they are consistent which a mechanism controlled by two factors, i.e., the ability of the leaving group to be displaced by a nucleophile and the electronic character of the attacking reagent.