A systematic study of functionalized oxiranes as initiating groups for cationic polycyclization reactions

Area of Science:

• Organic Chemistry
• Synthetic Chemistry
• Stereoselective Synthesis

Background:

• Cationic cyclization of unsaturated substrates to form chiral polycycles is synthetically valuable but challenging.
• Previous methods for initiating cationic cyclizations with chiral epoxides have encountered difficulties.

Purpose of the Study:

• To develop novel methods for the enantioselective synthesis of chiral polycycles.
• To utilize chiral oxiranes derived from Katsuki-Sharpless epoxidation as initiating groups for cationic cyclization.
• To address and explain previously encountered challenges in this synthetic transformation.

Main Methods:

• Development of three distinct methodologies employing chiral oxiranes.
• Utilizing epoxy-methoximes, vinyl-substituted oxiranes, and hydroxymethyl oxiranes as initiating groups.
• Detailed description of the synthetic procedures and reaction conditions.

Main Results:

• Successful synthesis of chiral polycycles via cationic cyclization initiated by chiral oxiranes.
• Identification of potential explanations for prior difficulties in similar transformations.
• Gained two new insights into Lewis acid activation of oxiranes.

Conclusions:

• The developed methodology effectively links enantioselective Katsuki-Sharpless epoxidation with cationic polycyclization.
• The new approaches provide a valuable tool for constructing complex chiral polycyclic molecules.
• The research offers a deeper understanding of Lewis acid-mediated oxirane activation in cyclization reactions.