Unusual Stereochemical Results in the Reaction of Alpha-Lithio Derivatives of Bicyclic Sulfoxides

Article abstract of DOI:10.1016/S0040-4020(01)90458-2

The stereochemistry of the reaction of the lithio derivatives of two sets of isomeric 3-thia<3.2.1>octane-3-oxides with electrophiles such as benzyl bromide, acetone and D2O has been studied.Introduction of deuterium always occurred cis to the S=O bond as expected on the basis of earlier results described by Marquet for the related thiane-S-oxides.In contrast, benzyl groups were introduced either cis or trans to the existing S=O bond.The results are most readily rationalized in terms of a planar configuration at the α-carbanion center. the unexpected cis benzylations are due to steric hindrance of the preferred approach anti to the S=O bond by either the ethano bridge or the 8-endo methyl group.