Date Approved

2014

Date Posted

4-16-2014

Degree Type

Campus Only Senior Honors Thesis

Department

Chemistry

First Advisor

Prof. Maria C. Milletti

Second Advisor

Prof. Hedeel Guy Evans

Third Advisor

Prof. Steve Pernecky

Abstract

Density functional methods are used to determine the energies of stationary points on the reaction pathways and activation barriers for an aza-Cope Mannich tandem reaction converting an oxazolidine into a pyrrolidine. Several steps in the reaction mechanism are examined to determine where stereoselectivity can be eroded. Specifically, we investigate the initial oxazolidine ring opening step, the aza-Cope rearrangement step and the C-C bond rotations that can occur prior to or following the aza-Cope rearrangement. The results of the calculations suggest that using a sterically-demanding chiral catalyst does not lead to selectivity toward one of two oxazolidine stereoisomers. In addition, this chiral catalyst does not prevent erosion of stereospecificity through C-C bond rotation in the iminium cation intermediates. Finally, in the presence of an achiral Lewis acid, when the oxazolidine substrate includes an isopropyl protecting group at the nitrogen center and a secondary carbinol carbon, activation barriers to C-C bond rotations that interconvert among stereoisomers are also sufficiently low to prevent stereoselectivity.

Share

COinS