Chiral Memory in Silylium Ions.

The configurational stability of the chiral silicon center in Lewis base-stabilized silyliums has been studied. Complete retention of configuration at silicon is observed at low temperature in silylium ions stabilized by lone-pair interactions. In contrast, loss of chiral memory is observed with systems involving π-interactions. Epimerization of the silicon center was observed by simply allowing equilibration of the diastereomeric silyliums at RT or by adding a catalytic amount of a chelating solvent. Conditions for the transfer of axial chirality to Si-centered chirality were shown to rely on the strength of the Lewis base-silylium ion interaction.