Syntheses and Theoretical Studies of Exocyclic γ-Oxoalkenyltrimethylsilanes. An Approach to the Stereodefined Exocyclic Tetrasubstituted Alkenes

Article abstract of DOI:10.1021/jo00099a027

The Z-selectivity in the dehydration of α-hydroxy-γ-oxoalkyltrimethylsilanes under acidic conditions was studied from experimental and theoretical points of view.Experimental results showed that (Z)-γ-oxoalkenyltrimethylsilanes were thermodynamic products under these conditions.The dehydration studies of the compound involving the tert-butyl group instead of the TMS group pointed out that not only steric but also electronic effects of Si could contribute to the distribution of the products as well as their stereochemistries.Theoretical studies using ab initio calculation at the 6-31D* level indicated that the (Z)-isomer was thermodynamically more stable than the corresponding (E)-isomer.Detail examinations of the optimized structures showed that the configuration of Si in the (Z)-isomer was slightly distorted from tetrahedral.Interpretation of the geometrical change of Si to rationalization of the thermodynamic preference was discussed from the viewpoint of possible coordination of the carbonyl oxygen to Si.Those (Z)-γ-oxoalkenyltrimethylsilanes would have potential to be the novel type of alkenylmetal compounds in organic synthesis as we demonstrated in the construction of stereodefined exocyclic tetrasubstituted alkene.