Products derived from the reaction between N-tert-butanesulfinyl imidates and acylsilanes can be tuned by choosing appropriate bases and solvents. Here we show that in the presence of NaHMDS/THF, addition of enolized N-tert-butanesulfinyl imidates to acylsilanes and subsequent [1,2]-Brook rearrangement generate beta-silyloxy anion intermediates that undergo intramolecular cyclization to afford polysubstituted cyclopropanes. In the presence of (BuOK)-Bu-t/toluene, the reaction generates beta-silyloxy imidates as the protonation products of the beta-silyloxy anion intermediates. Both reactions are highly diastereoselective.