New systems for catalytic asymmetric epoxidation

This thesis describes the catalytic asymmetric epoxidation of olefins mediated by oxaziridinium salts. The introduction highlights some of the most successful methods for preparing chiral oxiranes and hints at the synthetic utility of this versatile molecule. The second chapter is dedicated to our efforts to synthesize chiral iminium salts as catalysts for asymmetric epoxidation. The first part of this chapter describes previous Page group findings and leads on to the current author's efforts in this area. Initial results from modified amino acids, cyclo-condensed to form dihydroisoquinolinium salts, showed that an aromatic unit at C4 of our catalysts was vital for asymmetric induction. Following this, several catalysts substituted at the 4-position of the aromatic functionality were tested, and found to be effective mediators for asymmetric epoxidation. Triphenylethylene was epoxidized with up to 71% ee when using oxone as the stochieometric oxidant. [Continues.]