Nucleophilic substitution reactions of sulfur-substituted cyclohexanone acetals: An analysis of the factors controlling stereoselectivity

[GRAPHICS] The reactions of cyclohexanone acetals substituted with thiophenyl groups ( and other heteroatoms) at C-2 demonstrate the powerful influence that these substituents have on the stereoselectivity of nucleophilic substitution reactions. The trans selectivities of these reactions correlate with the behavior of the corresponding ketones. These experiments lend support to the possibility that the reactions of the acetals, which proceed via oxocarbenium ions, are operating under Felkin-Anh control.